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1
Peterson, J. E., and A. Davey. "Crossvalidation method for crosswell seismic tomography." GEOPHYSICS 56, no. 3 (March 1991): 385–89. http://dx.doi.org/10.1190/1.1443055.
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Crosswell seismic tomography is used to determine the variation of elastic wave velocity or attenuation between two boreholes and, if possible, boreholes and the surface from which they are drilled. In a transmission tomographic survey, traveltimes or amplitudes are measured for many raypaths between the boreholes and the surface. The data are inverted for velocity and attenuation, respectively. In this paper we only discuss traveltimes, but the methods are equally applicable to amplitude inversions.
2
Laine, E. F. "Remote monitoring of the steam‐flood enhanced oil recovery process." GEOPHYSICS 52, no. 11 (November 1987): 1457–65. http://dx.doi.org/10.1190/1.1442263.
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Cross‐borehole seismic velocity and high‐frequency electromagnetic (EM) attenuation data were obtained to construct tomographic images of heavy oil sands in a steam‐flood environment. First‐arrival seismic data were used to construct a tomographic color image of a 10 m by 8 m vertical plane between the two boreholes. Two high‐frequency (17 and 15 MHz) EM transmission tomographs were constructed of a 20 m by 8 m vertical plane. The velocity tomograph clearly shows a shale layer with oil sands above it and below it. The EM tomographs show a more complex geology of oil sands with shale inclusions. The deepest EM tomograph shows the upper part of an active steam zone and suggests steam chanelling just below the shale layer. These results show the detailed structure of the entire plane between boreholes and may provide a better means to understand the process for in situ heavy oil recovery in a steam‐flood environment.
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Cui, Pengfei, Banghua Yao, Yong Liu, Jianping Wei, Zhihui Wen, and Hui Li. "A New Width Measurement Method of the Stress Relief Zone on Roadway Surrounding Rocks." Geofluids 2019 (November 27, 2019): 1–12. http://dx.doi.org/10.1155/2019/9519353.
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Determining the width of the stress relief zone on roadway surrounding rocks is the premise to optimize drilling borehole effect and increase gas extraction efficiency. In this study, a new width measurement method of the stress relief zone on the roadway surrounding rocks was proposed, which determined the width according to gas pressure attenuation speeds in roadway boreholes at different depths. Then, the variation curve of the gas pressure in boreholes at different depths with the time was gained through a field test. On this basis, laws of the gas pressure attenuation and the gas transmission and loss in boreholes at different depths were explored through a numerical simulation based on COMSOL Multiphysics, thus concluding the stress on roadway surrounding rocks, the distribution of plastic zones, and the stress-permeability relation. The scientificity of the proposed method was illustrated theoretically. Finally, the proposed method was verified by the field test data and numerical simulation results of the gas extraction at different sealing depths. Research results demonstrate that the pressure in boreholes attenuates in the logarithmic function pattern. The attenuation speed decreases with the increase of the drilling depth. The width of the stress relief zone on roadway surrounding rocks in the studied area was determined to be about 11 m according to the proposed method. Both the numerical simulation and the field test of the gas extraction efficiency prove the feasibility and validity of the proposed method in determining the sealing depth of the borehole for the gas extraction. Research conclusions are of important significance to enrich width measurement methods of the stress relief zone on roadway surrounding rocks and to optimize sealing parameters of underground boreholes for gas extraction.
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Giertzuch, Peter-Lasse, Joseph Doetsch, Alexis Shakas, Mohammadreza Jalali, Bernard Brixel, and Hansruedi Maurer. "Four-dimensional tracer flow reconstruction in fractured rock through borehole ground-penetrating radar (GPR) monitoring." Solid Earth 12, no. 7 (July 6, 2021): 1497–513. http://dx.doi.org/10.5194/se-12-1497-2021.
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Abstract. Two borehole ground-penetrating radar (GPR) surveys were conducted during saline tracer injection experiments in fully saturated crystalline rock at the Grimsel Test Site in Switzerland. The saline tracer is characterized by an increased electrical conductivity in comparison to formation water. It was injected under steady-state flow conditions into the rock mass that features sub-millimeter fracture apertures. The GPR surveys were designed as time-lapse reflection GPR from separate boreholes and a time-lapse transmission survey between the two boreholes. The local increase in conductivity, introduced by the injected tracer, was captured by GPR in terms of reflectivity increase for the reflection surveys, and attenuation increase for the transmission survey. Data processing and difference imaging was used to extract the tracer signal in the reflection surveys, despite the presence of multiple static reflectors that could shadow the tracer reflection. The transmission survey was analyzed by a difference attenuation inversion scheme, targeting conductivity changes in the tomography plane. By combining the time-lapse difference reflection images, it was possible to reconstruct and visualize the tracer propagation in 3D. This was achieved by calculating the potential radially symmetric tracer reflection locations in each survey and determining their intersections, to delineate the possible tracer locations. Localization ambiguity imposed by the lack of a third borehole for a full triangulation was reduced by including the attenuation tomography results in the analysis. The resulting tracer flow reconstruction was found to be in good agreement with data from conductivity sensors in multiple observation locations in the experiment volume and gave a realistic visualization of the hydrological processes during the tracer experiments. Our methodology was demonstrated to be applicable for monitoring tracer flow and transport and characterizing flow paths related to geothermal reservoirs in crystalline rocks, but it can be transferred in a straightforward manner to other applications, such as radioactive repository monitoring or civil engineering projects.
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Le, Heng, Ming Deng, Qi Sheng Zhang, Guan Min Li, and Shan Qiao. "Development of Long Distance Data Transmission and Control Circuit in Borehole." Applied Mechanics and Materials 321-324 (June 2013): 2492–95. http://dx.doi.org/10.4028/www.scientific.net/amm.321-324.2492.
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This paper introduces a data transmission circuit used to transmit signals over thousands of meters in borehole; meanwhile, a control system that is equipped with the circuit is also presented here. This set of equipment has many advantages over previous systems-smaller size, less cost, longer communication distance and friendlier user interface. The design of hardware in the system consists of LVDS transceiver circuit, USB port circuit based on high speed MCU C8051F321, automatic power-on circuit based on relay TQ201 and acquisition circuit based on 24-bit analog-to-digital converter LTC2492. The software is based on both C language and VC++6.0. Finally, it accomplishes a kind of data transmission circuit and control system in borehole which delivers the data from thousands of meters away.
6
Squires, Livia J., Paul L. Stoffa, and Guillaume Cambois. "Borehole transmission tomography for velocity plus statics." GEOPHYSICS 59, no. 7 (July 1994): 1028–36. http://dx.doi.org/10.1190/1.1443659.
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The accuracy of velocity tomograms reconstructed from borehole transmission traveltime data is highly sensitive to traveltime statics. We present a least‐squares tomography algorithm that includes a traveltime static term. The algorithm solves for both the velocity field and the traveltime statics simultaneously. This enables us to separate traveltime signal from traveltime noise, reducing the tomographic velocity artifacts caused by the statics. The incorporation of a priori constraints on the poorly determined spectral components of the velocity field further improves accuracy by reducing velocity artifacts as a result of uneven ray coverage. Application of the algorithm to numerical crosswell data results in velocity and statics’ estimates that are accurate to within 1 percent. Application of the algorithm to Exxon’s Friendswood tomography data results in velocity and statics’ estimates that correlate with independent data.
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Su, Juan, and Zheng Guo Yan. "Image Compression and Transmission System for Digital Down-Hole Television." Applied Mechanics and Materials 130-134 (October 2011): 3068–71. http://dx.doi.org/10.4028/www.scientific.net/amm.130-134.3068.
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Image compression method and long distance transmission technology are technical difficulties in researching digital down-hole television. A down-hole image compression and transmission system is designed. Data are transmitted with quad logging cables and the data transfer rate is 100Kbps; hardware image compression method based on the wavelets transform is adopted and image data are treated with the wavelets transform, quantization and coding. By controlling color selection, quantizes coefficients, quality box parameters, background contrast and field rate to achieve dynamic control of compression rate and obtain high compression ratio simultaneously. Two compression ratio control methods are presented according to data transfer rate and typical borehole image and steady image can be observed in 3000m deep mine.
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Akbar, Muhammad F., Ivan Vasconcelos, Hanneke Paulssen, and Wen Zhou. "In-Reservoir Waveform Retrieval for Monitoring at Groningen—Seismic Interferometry with Active and Passive Deep Borehole Data." Remote Sensing 13, no. 15 (July 26, 2021): 2928. http://dx.doi.org/10.3390/rs13152928.
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The Groningen gas field in the Netherlands is an ideal test bed for in-situ reservoir monitoring techniques because of the availability of both active and passive in-reservoir seismic data. In this study, we use deconvolution interferometry to estimate the reflection and transmission response using active and passive borehole data within the reservoir at ∼3-km depth and separate up- and downgoing P- and S-wave fields by f-k filtering. We validate the results using synthetic data of a 1D elastic model built from sonic logs recorded in the well. The estimated full-waveform reflection response for a virtual source at the top geophone is consistent with the synthetic response. For the virtual source at the bottom geophone, the reflection response appears to be phase delayed, though its arrivals are consistent with the local subsurface geology. Similarly, the first-order estimated local transmission response successfully approximates that of the P-wave velocity in the reservoir. The study shows that reliable subsurface information can be obtained from borehole interferometry without detailed knowledge of the medium parameters. In addition, the method could be used for passive reservoir monitoring to detect velocity, attenuation, and/or interface time-lapse variations.
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Irving, James D., and Rosemary J. Knight. "Numerical simulation of antenna transmission and reception for crosshole ground-penetrating radar." GEOPHYSICS 71, no. 2 (March 2006): K37—K45. http://dx.doi.org/10.1190/1.2187768.
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Numerical models that account for realistic transmitter and receiver antenna behavior are necessary to develop waveform-based inversion methods for crosshole ground-penetrating radar (GPR) data. A challenge in developing such models is simulating the antennae in a computationally efficient manner so that inversions can be performed in a reasonable amount of time. We present an approach to efficiently simulate crosshole GPR transmission and reception in heterogeneous media. The core of our approach is a finite-difference time-domain (FDTD) solution of Maxwell's equations in 2D cylindrical coordinates. First, we determine the behavior of the current on a realistic GPR antenna in a borehole through detailed FDTD modeling of the antenna and its immediate surroundings. To model transmission and reception, we then replicate this antenna current behavior on a much-coarser grid using a superposition of point-electric-dipole source and receiver responses. Results obtained with our technique agree with analytical results, with numerical modeling results where the transmitter antenna and borehole are explicitly accounted for using a fine discretization, and with crosshole GPR field data.
10
Li, Jiang, and Tsili Wang. "Efficient compression of borehole resistivity and acoustic imaging data using wavelets." GEOPHYSICS 70, no. 6 (November 1, 2005): F53—F60. http://dx.doi.org/10.1190/1.2127112.
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This paper presents a new approach to borehole resistivity and acoustic imaging data compression. The method is based on the discrete wavelet transform (DWT) combined with the set partitioning in the hierarchical trees (SPIHT) coding method. The primary advantages of the DWT + SPIHT method are its superior compression performance, simple implementation, and constant compression and transmission rate control. This new approach generally performs better than the traditional discrete cosine transform (DCT) followed by Huffman coding methods such as JPEG, particularly for target compression ratios greater than 50:1. Image block size plays a key role in using this method. To achieve the best compression performance, the image block size needs to be selected appropriately. In general, large image block sizes and more DWT decomposition levels result in higher compression ratios and/or fewer reconstruction errors. Whenever possible, image block sizes that allow the maximum levels of dyadic DWT decomposition should be used. When insufficient data samples are available in either depth or azimuthal direction, a small number of extra data samples can be added without sacrificing the overall compression performance. The DWT + SPIHT method also shows good fidelity in representing major features in borehole images such as fractures and sinusoids.
11
Islam, Md Shahriar, Nathan Peter, and Travis Wiens. "Simulation and experiment of vibrational or acoustic communication in mining and oil-gas drill strings." Transactions of the Canadian Society for Mechanical Engineering 43, no. 4 (December 1, 2019): 454–62. http://dx.doi.org/10.1139/tcsme-2018-0227.
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Drilling for exploration and mineral extraction purposes is generally an invisible process, that is, there is a lack of real-time information available from the tool head. The borehole mining and oil-gas drilling industries both face tremendous challenges because of this invisibility. Lack of data has impacts on extraction quantity and quality, process efficiencies, and is a major factor in overall program costs. This is why a communication method between the drill head and the surface has been under research. Different communication methods have enabled industries to establish more control over the drill bit. Low data transmission rate is one of the most concerning drawbacks of existing communication methods. Acoustic, also known as vibrational telemetry, is the most recent method used in transferring data through drill pipe at the highest data transmission rate. The proper use of acoustic tools and communication schemes will successfully establish a fast data transmission rate and is expected to become a popular method. This paper will introduce a simulation model for transmission of data through drill pipes and will extrapolate a practical case of a large number of pipes that is usually used in oil-gas extraction. It will also demonstrate an experimental setup of a new acoustic transducer.
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Verwer, Klaas, Hendrik Braaksma, and Jeroen A. Kenter. "Acoustic properties of carbonates: Effects of rock texture and implications for fluid substitution." GEOPHYSICS 73, no. 2 (March 2008): B51—B65. http://dx.doi.org/10.1190/1.2831935.
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More than 250 plugs from outcrops and three nearby boreholes in an undisturbed reef of Miocene (Tortonian) age were quantitatively analyzed for texture, mineralogy, and acoustic properties. We measured the P- and S-waves of carbonate rocks under dry (humidified) and brine-saturated conditions at [Formula: see text] effective pressure with an ultrasonic pulse transmission technique [Formula: see text]. The data set was compared with an extensive database of petrophysical measurements of a variety of rock types encountered in carbonate sedimentary sequences. Two major textural groups were distinguished on the basis of trends in plots of compressional-wave velocity versus Poisson’s ratio (a specific ratio of P-wave over S-wave velocity). In granular rocks, the framework of depositional grains is the main medium for acoustic-wave propagation; in crystalline rocks, this medium is provided by a framework of interlocking crystals formed during diagenesis. Rock textures are connected to primary depositionalparameters and a diagenetic overprint through the specific effects on Poisson’s ratio. Calculating acoustic velocities using Gassmann fluid substitution modeling approximates measured saturated velocities for 55% of the samples (3% error tolerance); however, it shows considerable errors because shear modulus changes with saturation. Introducing brine into the pore space may decrease the shear modulus of the rock by approximately [Formula: see text] or, alternatively, increase it by approximately [Formula: see text]. This change in shear modulus is coupled with the texture of the rock. In granular carbonates, the shear modulus decreases; in crystalline and cemented carbonates, it increases with saturation. The results demonstrate the intimate relationship between elastic behavior and the depositional and diagenetic properties of carbonate sedimentary rocks. The results potentially allow the direct extraction of granular and crystalline rock texture from acoustic data alone and may help predict rock types from seismic data and in wells.
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Xia, Tong-qiang, Ke Gao, Hong-yun Ren, Jiao-fei He, and Zi-long Li. "Network Design Mode of In-Seam Gas Extraction Parameters Using Mathematical Modelling—Take Tangan Colliery as an Example." Geofluids 2020 (November 10, 2020): 1–12. http://dx.doi.org/10.1155/2020/8886068.
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Gas extraction is a practical and effective way to guarantee mining-process safety and deliver greater environmental benefits through reducing greenhouse gas emissions and increase the supply of a valuable clean gas resource. It has been effective in recent years, however it still has a series of problems that need to be solved. Gas extraction design mainly relies on engineering experience rather than quantitative design, resulting in low input-output ratio of gas extraction because of unreasonable design. How to build a bridge of communication between engineers and scientists is the key to realize scientific gas extraction. In this work, taking our previous gas-coal and gas-coal-heat coupling models of gas extraction as the theoretical basis, a new communication and design concept—an engineering design platform for gas extraction—is proposed using the network mode. Through the platform, on- and off-line interactions between service centre (scientific workers) and design objects (enterprises or individuals), such as data transmission, material review, scheme design and reviews, and so on. It greatly improves the efficiency and standardization of gas extraction design. Appling the networked platform, the gas extraction engineering parameters were quantitatively designed in the working face of 3307, Tangan colliery. According to the extraction time, the working face was divided into 6 extraction units. The number of boreholes were 763, the drilling capacity of coal was 0.03 m/t, and the extraction rate of each unit was more than 25%. The networked mode of in-seam gas extraction design would transform the traditional experience to the quantitative mode.
14
Squires, Livia J., and Guillaume Cambois. "A linear filter approach to designing off‐diagonal damping matrices for least‐squares inverse problems." GEOPHYSICS 57, no. 7 (July 1992): 948–51. http://dx.doi.org/10.1190/1.1443308.
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Many geophysical data processing applications are formulated as either linear or linearized‐nonlinear inverse problems. Usually, the linear systems that describe these problems are ill‐posed. For example, seismic deconvolution is an ill‐posed inverse problem because the seismic wavelet is band limited. Borehole transmission tomography is ill‐posed because of insufficient ray coverage around the tomographic model (Worthington, 1984). Surface‐consistent statics’ estimation is intrinsically ill‐posed because of the geometrical relationships between the parameters defined by the surface-consistent model (Taner et al., 1974).
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Tura, M. Ali C., Lane R. Johnson, Ernest L. Majer, and John E. Peterson. "Application of diffraction tomography to fracture detection." GEOPHYSICS 57, no. 2 (February 1992): 245–57. http://dx.doi.org/10.1190/1.1443237.
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Two diffraction tomography techniques are applied to crosshole field data to detect fractures in granitic rock. The techniques used are the conventional back‐propagation method and a new quadratic programming method incorporating constraints. In this formulation, the Born approximation is used for linearization of the inverse problem. Two dimensional (2-D) pseudo spectral finite‐difference synthetic data are generated to demonstrate the inversion methods and justify use of the Born approximation. Also, using 2-D Born synthetic data, the velocity sensitivity of the inversion algorithm and reduction of fracture generated tube waves and S‐waves are investigated. The inversion methods are applied to field data from the Grimsel test site in Switzerland. The data are collected from a [Formula: see text] rectangular area where fractures are known to exist. Data acquisition with 0.5 m spacing of three component receivers and a piezoelectric source is carried out so as to obtain a nearly complete coverage of the region. Crosshole inversions are performed on data from the receiver components in the plane of the rectangular region and normal to its boundary. As the result of a separate experiment conducted in a homogeneous region of the granitic rock, a cosine function was found to best fit the source radiation pattern. A background attenuation value is estimated for the region, using a simple statistical approach, and estimates of the wavelet are found by common source gathers, common receiver gathers, and averages of all traces. The preprocessing steps are: (1) source radiation correction, (2) attenuation correction, (3) removal of the incident wavefield, (4) muting beginning of the traces and windowing the ends, (5) wavelet deconvolution, and (6) two‐and‐a‐half dimensional (2.5-D) corrections. This preprocessing is designed to enhance scattered P‐waves that are used in the inversions. Images obtained from the application of back‐propagation and quadratic programming methods to the preprocessed data show possible fracture zones that agree well at the boundaries of the region with the fracture sets observed from core samples taken from the boreholes. Although the quadratic programming method is an order of magnitude slower than the back‐propagation method, as demonstrated by the synthetic examples, it proves useful by yielding high resolution images when constraints can be imposed. Transmission ray tomography is also applied to the crosshole data, and although the resolution is not as high, general agreement with the wave equation based methods is obtained.
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Liu, Qing‐Huo, and Chung Chang. "Compressional head waves in attenuative formations: Forward modeling and inversion." GEOPHYSICS 61, no. 6 (November 1996): 1908–20. http://dx.doi.org/10.1190/1.1444106.
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We develop a method of forward modeling and inverting formation attenuation data from sonic compressional head waves in a fluid‐filled borehole using a branch‐cut integration (BCI) technique to calculate individual acoustic arrivals. We validate this approach with a real‐ axis integration (RAI) method that does not separate the individual arrivals. We show that the straightforward application of the original BCI method for lossless media gives erroneous results for attenuative formations. With a choice of the Riemann sheets satisfying the radiation condition, the new BCI method gives correct results for most lossy and lossless formations. However, modeling very slow formations needs to include the contribution of a leaky pole near the vertical branch cut. With a constant‐Q assumption, we develop a simple processing scheme to extract the formation compressional Q factor from the P head‐wave arrivals. We used experimental data from laboratory‐scale borehole measurements to invert for the compressional Q value of a Lucite block. The inverted results agree within 4.5% of an independent ultrasonic transmission measurement of Q.
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Lee, Doo Sung, Spyros K. Lazaratos, Gregory N. Fitzgerald, and Takashi Imayoshi. "High‐resolution crosswell seismic experiment with a large interwell spacing in a west Texas carbonate field." GEOPHYSICS 60, no. 3 (May 1995): 727–34. http://dx.doi.org/10.1190/1.1443811.
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A high‐frequency crosswell seismic dataset acquired in a west Texas carbonate field has demonstrated the feasibility of the technique with a large interwell spacing. Two crosswell profiles were acquired with a well spacing of 1500 ft (460 m) and over a depth interval from 7700 ft (2350 m) to 9600 ft (2930 m) using a piezoelectric bender source. The data quality is profile and depth dependent, with the ambient noise level at the receiver position being the most important factor. Noise levels and noise characteristics among three wells were significantly different. Tube waves and gas‐ and fluid‐movement in the borehole are the dominant noise sources found in the data set. Two lithologic properties, attenuation and transmission loss controlled the data quality. Good quality and high frequency (>1000 Hz) data were acquired over most of the survey interval which contains massive limestones. However, we could not acquire any useful data within the shale layers. Transmission losses and the effects of the source radiation pattern that occurred at interfaces with large impedance contrasts limited the aperture of the useful data. There were two critical issues encountered during the reflection imaging process: (1) sparse trace spacing and poor coherency of the reflection events in common‐source gathers degraded the image in a region near the receiver well; and (2) possible lateral velocity heterogeneity in the medium and limited aperture made it difficult to build an appropriate velocity model for reflection imaging.
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Bretaudeau, François, Céline Gélis, Donatienne Leparoux, Romain Brossier, Justo Cabrera, and Philippe Côte. "High-resolution quantitative seismic imaging of a strike-slip fault with small vertical offset in clay rocks from underground galleries: Experimental platform of Tournemire, France." GEOPHYSICS 79, no. 1 (January 1, 2014): B1—B18. http://dx.doi.org/10.1190/geo2013-0082.1.
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Imaging tectonic faults with small vertical offsets in argillites (clay rock) using geophysical methods is challenging. In the context of deep radioactive waste disposals, the presence of such faults has to be assessed because they can modify the rock-confining properties. In the Tournemire Experimental Platform (TEP, Aveyron, France), fault zones with small vertical offsets and complex shape have been identified from underground works. However, 3D high-resolution surface seismic methods have limitations in this context that led us to consider the detection and characterization of the faults directly from underground works. We investigated the potential of seismic full-waveform inversion (FWI) applied in a transmission configuration to image the clay rock medium in a horizontal plane between galleries and compared it with first-arrival traveltime tomography (FATT). Our objective was to characterize seismic velocities of a block of argillites crossed by a subvertical fault zone with a small vertical offset. The specific measurement configuration allowed us to neglect the influence of the galleries on the wave propagation and to simplify the problem by considering a 2D isotropic horizontal imaging domain. Our FWI scheme relied on a robust adaptation of early arrival waveform tomography. The results obtained with FATT and FWI were in accordance, and both correlated with the geologic observations from the gallery walls and boreholes. We found that even though various simplifications was done in the inversion scheme and only a part of the data was used, FWI allowed us to get higher resolution images than FATT, and it was especially less sensitive to the incomplete illumination because it also used diffracted energy. Our results highlighted the complexity of the fault zone, showing a complex interaction of the main fault system with a secondary system composed of decimetric fractures associated with the presence of water.
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Gubaidullin, A. A., O. Y. Boldyreva, and D. N. Dudko. "Linear wave propagation in a cylindrical waveguide in a porous medium with layer containing the hydrate." Proceedings of the Mavlyutov Institute of Mechanics 12, no. 1 (2017): 9–14. http://dx.doi.org/10.21662/uim2017.1.002.
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Pressure waves propagating along a cylindrical cavity in a porous medium with hydrate layer are investigated in the linear approximation. Dispersion relations for the basic acoustic mode in a cylindrical cavity in each layer constituting the porous medium are obtained. On the basis of the dispersion relations the coefficients of reflection and transmission through the layer boundaries inside the cavity are calculated. The influence of rock properties, frequency, and length of hydrate layer on the total reflection coefficient from the layer is studied. The obtained results can be used in the interpretation of well data to locate the boundary of layers crossed by the borehole, in particular, layer containing the hydrate.
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Parra, Jorge O., Brian J. Zook, Pei‐Cheng Xu, and Raymon L. Brown. "Transmission and detection of guided seismic waves in attenuating media." GEOPHYSICS 63, no. 4 (July 1998): 1190–99. http://dx.doi.org/10.1190/1.1444419.
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We can use guided seismic waves to map properties of reservoirs between wells, with the low‐velocity layers acting as waveguides. When guided waves are detected, they are an indication of the continuity of the bed examined. Guided waveforms are characterized by time‐frequency representations to study important physical properties of the beds acting as waveguides. We used full waveform seismic modeling in viscoelastic media to examine the required velocity contrasts and distances over which guided‐wave signals can be used. In one set of models, sandstones are the central waveguide lithology; in another set, shales. We applied these models, referred to here collectively as shaly sandstone waveguides, to a range of geological circumstances where either the sands or the shales represent the low‐velocity layers within a reservoir. To study the distances over which guided waves can be detected, we compared the amplitudes of the signals computed for the models, using a realistic source strength, to the signal levels determined from published borehole noise studies. In shaly sandstone waveguides, we find it is feasible to use particle velocity measurements to record guided waves above seismic noise levels in the frequency range of 60 to 800 Hz at well separations exceeding a distance of 800 m. However, pressure detectors such as hydrophones may only be useful up to distances of 400 m between wells. In addition to the issues of shaly sandstone waveguides and practical distances between wells, we present an application of guided waves using crosswell seismic data from the Gypsy test site in Oklahoma (a site originally established by British Petroleum). In this field example within a sandstone reservoir, we demonstrate the sensitivity of leaky mode amplitudes to source‐receiver location. Another telltale characteristic of continuity in the type of reservoir studied at the Gypsy test site, where there is a low shear velocity contrast between the host medium and the waveguide, is the head wave followed by the leaky mode.
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Mason, William P., Alexander J. Shturmakov, Jay A. Johnson, and Scott Haman. "A new 122 mm electromechanical drill for deep ice-sheet coring (DISC): 2. Mechanical design." Annals of Glaciology 47 (2007): 35–40. http://dx.doi.org/10.3189/172756407786857640.
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AbstractThe deep ice-sheet coring (DISC) drill consists of four major mechanical drilling subsystems and four subsystems supporting on-surface activities. The mechanical drilling subsystems are a drill sonde, a drill cable, a tower and a winch. The drill sonde is the down-hole portion of the drill system and consists of six distinct sections: (1) the cutter head, (2) the core barrel, (3) the screen section, (4) the motor/pump section, (5) the instrument section and (6) the upper sonde, which includes anti-torques and drill cable terminations. The drill cable not only provides the means of supporting the drill sonde in the borehole, but also provides conduits for electrical power and data transmission. The tower tilts to allow the drill sonde to be serviced in the horizontal position without removing it from the tower. The winch provides a means of quickly raising the sonde from the borehole and providing the fine control necessary for coring operations.
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Jackson, Christopher A. L., Clara R. Rodriguez, Atle Rotevatn, and Rebecca E. Bell. "Geological and geophysical expression of a primary salt weld: An example from the Santos Basin, Brazil." Interpretation 2, no. 4 (November 1, 2014): SM77—SM89. http://dx.doi.org/10.1190/int-2014-0066.1.
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Primary salt welds form at the base of minibasins in response to complete evacuation of autochthonous salt. Analytical and numerical models suggest it is difficult to completely remove salt from a weld by viscous flow alone, which is especially true in multilayered evaporites, within which flow is likely heterogeneous due to lithologically controlled viscosity variations. Welds are important in the hydrocarbon industry because they may provide a hydrodynamic seal and trap hydrocarbons, or may allow transmission of fluids from source to reservoir rocks. Few papers document the subsurface expression of welds, principally because they have not been penetrated by wells or because the associated data are proprietary. We use 3D seismic and borehole data from the Santos Basin, offshore Brazil to characterize the geological and geophysical expression of a primary weld associated with flow of Aptian salt. The seismic data that we evaluated suggested that, locally, presalt and postsalt rocks are in contact at the base of an Upper Cretaceous minibasin, implying that several apparent welds, separated by low-relief salt pillows, are present. However, borehole data indicated that 22 m of anhydrite, carbonate, and sandstone are present in one of the welds, indicating that this and other welds may be incomplete. We find that seismic data may be unable to discriminate between a complete and incomplete weld, and we suggested that, during the subsurface analysis of welds, the term apparent weld is used until borehole data unequivocally proves the absence of salt. Furthermore, we speculate that preferential expulsion of halite and potash salt from the autochthonous layer during viscous flow and welding resulted in the formation of an incomplete weld, which, when compared with the initial autochthonous layer, is volumetrically enriched in nonevaporite lithologies and relatively viscous evaporite lithologies (anhydrite). The composition and stratigraphy of the autochthonous layer may thus dictate weld thickness and seal potential.
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Gopalakrishnan, Manoj, Eldho Jacob, and Sona Kundukulam. "Relay based Coupling Scheme of High Speed Communication data, High voltage DC And High Power Pulsed AC for Coaxial Cable." Defence Science Journal 68, no. 5 (September 12, 2018): 487–93. http://dx.doi.org/10.14429/dsj.68.11907.
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Coaxial cable telemetry is most commonly used in the field of underwater applications like data logging in oil rigs, underwater wireless modem, underwater acoustic measurements, borehole measurements, deep sea telemetry for sediment analysis, airborne sonars, imaging sonars etc. In all the above applications coaxial multicore cables are used. The design and development of relay based coupling scheme which helps to replace the multi core cable with a single core coaxial cable for telemetry application is described. Single core cable is suitable for long distance data communication. Multi core cables are generally heavy and due to the size, may not meet space constraints in complex systems. They are not economical too. The relay based coupling scheme is used to mix or separate the high speed bi-directional communication data, high voltage DC and high power pulsed AC. In single relay scheme one relay is used to switch the centre core of single core coaxial cable. Here the ground is common for both high power AC transmission and high speed bi-directional data path. A dual relay scheme is discussed where two relays are used to switch both the centre core and ground of the single core coaxial cable. This provides more ground isolation and can avoid ground lifting issues while high power AC transmission occurs. The simulation of the coupling scheme was done using PSpice®. A prototype of the coupling scheme was also made for analysis. Filter responses were analysed for each coupling path. The DC coupling filter has 85 Hz cut-off frequency at -3 dB. The cut-off frequency of high speed data coupler is 500 KHz at -3 dB. A 4.3KV peak to peak of 3 KHz and 7 KHz AC signals were transmitted and measurements were taken to analyse the effect of high voltage over different coupling paths. The 3 KHz signal has a peak of 61.88 dB and that of 7 KHz signal, the peak is 62.50 dB. The signal components of 3 KHz signal in the DC path has a voltage level of 9.375 dB and that of 7 KHz signal is 25.63 dB.
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Wang, Gong Li, and Aria Abubakar. "Rapid simulation of borehole electromagnetic response in axially symmetric and transversely isotropic formations." GEOPHYSICS 83, no. 4 (July 1, 2018): E245—E257. http://dx.doi.org/10.1190/geo2017-0095.1.
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Downhole well-logging data acquired by modern electromagnetic (EM) tools enables determining not only conductivity but also conductivity anisotropy of reservoirs. The most popular anisotropic model for EM data interpretation is a horizontally layered model with transverse isotropic conductivity in each layer. Such a model ignores the conductivity change caused by the mud-filtrate invasion that often occurs in a permeable layer. The invasion effect can be so strong that the conductivity derived using the 1D model can be substantially affected. We have developed an efficient forward-modeling approach that includes the invasion in the formation model so that the invasion effect can be properly accounted for in data interpretation and inversion. The approach uses a Fourier series expansion for the electric field in the azimuthal direction to take advantage of the invariance of conductivity in this direction. Each harmonic in the expansion is expressed in terms of numerical eigenmodes in the radial direction and exponential functions in the vertical direction. Physically, the latter describes a set of plane waves propagating upward or downward in the vertical direction. This property allows us to use reflection and transmission matrices to couple EM fields from layer to layer, making it highly efficient to simulate EM logging response because the two matrices are computed only once for all logging points. The approach is best suited for a multilayer and transversely isotropic formation in which each layer can have an arbitrary number of radial discontinuities. Numerical experiments demonstrate that the new approach can accurately model the response of induction and propagation tools in various formations. A speedup of two orders of magnitude is obtained in a multilayer case compared with a previous 2D method using a different hybridization strategy.
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Bache, Thomas C., Peter D. Marshall, and John B. Young. "High-frequency seismic noise characteristics at the four United Kingdom-type arrays." Bulletin of the Seismological Society of America 76, no. 3 (June 1, 1986): 601–16. http://dx.doi.org/10.1785/bssa0760030601.
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Abstract The noise spectra are described from 0.3 to 8 Hz for the United Kingdom (UK)-type medium aperture arrays EKA, YKA, GBA, and WRA. These arrays have been operating in the same configuration since the mid-1960's and therefore provide a unique source of high-quality data for frequencies in this range. The array noise spectra are compared to spectra recorded at sites (Lajitas, NORSAR, and RSTN) specifically selected for high-frequency signal recording. At nearly all of these stations and arrays (borehole or near-surface), the characteristic noise spectrum follows a linear trend above 2 Hz, with displacement amplitude slope varying from f−1.7 to f−2.5. The GBA spectrum is an exception in that it flattens above 4 Hz, apparently due to locally generated high-frequency noise trapped near the surface. This shows that spectral flattening is not an infallible indicator of system noise contamination. System noise imposes no significant limitation on the ability to recover seismic signal or noise spectra to at least 8 Hz for EKA, GBA, and YKA. The WRA seismic noise spectra are contaminated by system noise above 3 to 4 Hz, apparently due to transmission link problems. It seems likely that borehole seismometers at YKA, GBA, and WRA would achieve noise levels between those recorded at NORSAR and the very quiet Lajitas site; i.e., similar to those at the quieter RSTN sites RSNT, RSON, and RSSD.
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MARTEL, S. J. "Analysis of Fracture Orientation Data From Boreholes." Environmental & Engineering Geoscience V, no. 2 (June 1, 1999): 213–33. http://dx.doi.org/10.2113/gseegeosci.v.2.213.
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Weir, F. M. "The future of structural data from boreholes." International Journal of Geotechnical Engineering 9, no. 3 (March 18, 2014): 223–28. http://dx.doi.org/10.1179/1939787914y.0000000049.
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Schamper, Cyril, Flemming Jørgensen, Esben Auken, and Flemming Effersø. "Assessment of near-surface mapping capabilities by airborne transient electromagnetic data — An extensive comparison to conventional borehole data." GEOPHYSICS 79, no. 4 (July 1, 2014): B187—B199. http://dx.doi.org/10.1190/geo2013-0256.1.
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A newly developed helicopter transient electromagnetic (TEM) system has the ability to measure very early times within just a few μs after the turn off of the primary current. For such a system, careful calibration and accurate modeling of the electromagnetic (EM) response is critical to get true resistivities of the very shallow geologic layers. We discovered that this leads to resolution of the same level or in some cases even better than what can be obtained from airborne frequency EM systems. This allowed a range of important applications where high and accurate resolution is mandatory, e.g., geotechnical applications such as urban planning, railroad and road investigations, landslides or distribution of raw materials, and assessing aquifer vulnerability. We evaluated the results of a pilot survey covering the Norsminde catchment south of Aarhus, Denmark, where we found that near-surface layers (top 30 m) can be mapped with an accuracy of a few meters in a complicated glacial sedimentary environment. The mapping of the geologic layers was assessed by a detailed analysis in which we developed a general methodology for crosschecking the EM and borehole data. This methodology is general and can easily be adapted to other data types and surveys. After rating the quality of the boreholes based on a list of predefined criteria, we concluded that the EM data matched with about three-quarters of the boreholes located within less than 15 m from the closest EM soundings. The remaining quarter of the boreholes fell into two groups in which half of the boreholes were of very poor quality or had inaccurate coordinates. Only eight of all the boreholes could not be reproduced by the data, and we attributed this to be caused by very strong lateral or vertical geologic variations not resolvable by the TEM technique.
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Liu, Jing Hua, Sheng Nan Huang, and Gang Chen. "Data Analysis and Evaluation to Water-Sealed Underground Storage Cavern Water Curtain Efficiency Test." Applied Mechanics and Materials 744-746 (March 2015): 956–61. http://dx.doi.org/10.4028/www.scientific.net/amm.744-746.956.
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Water curtain efficiency test is the key method to evaluate the tightness and reliability of water curtain system. This thesis taking the cavern in Yantai as an example, based on the data of three different hydrodynamic condition stages during efficiency test, in combination with the important judgment parameter of water curtain efficiency-critical pressure value, the low efficiency of rock area was revealed by analyzing and evaluating the conduction effect of fissure water pressure. In order to improve the efficiency, drilled additional boreholes in low efficiency area. At last, through the test to evaluate efficiency improvement of new drilled boreholes. The test result shows that: the water curtain efficiency test can able to accurately determine the low efficiency area in rock mass, additional boreholes can significantly improve the pressure of low efficiency boreholes and can achieve the tightness requirements of cavern.
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Gao, Mingzhong, Wencheng Jin, Ru Zhang, Jing Xie, Bin Yu, and Hongfei Duan. "Fracture size estimation using data from multiple boreholes." International Journal of Rock Mechanics and Mining Sciences 86 (July 2016): 29–41. http://dx.doi.org/10.1016/j.ijrmms.2016.04.005.
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Dong, Wenjie, and M. Nafi Toksöz. "Borehole seismic‐source radiation in layered isotropic and anisotropic media: Real data analysis." GEOPHYSICS 60, no. 3 (May 1995): 748–57. http://dx.doi.org/10.1190/1.1443813.
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The source and receiver boreholes in crosshole seismology are usually considered unimportant except for their effects on body wave radiation and reception patterns. We present counter examples by analyzing a real crosswell data set from Buckhorn, Illinois, using computer simulations. The algorithm used is a combination of the boundary element method (for the source borehole) and the borehole coupling theory (for the receiver borehole) in transversely isotropic media. We find that most of the strong events in the data are inexplicable unless both boreholes are included in the modeling. The importance of the boreholes stems from the local geology which consists of highly contrasted sedimentary rocks. At a high‐contrast interface, wave conversion is no longer a negligible secondary effect. In fact, converted waves can be stronger than the primaries.
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Kabir, C. S., and A. R. Hasan. "Does Gauge Placement Matter in Downhole Transient-Data Acquisition?" SPE Reservoir Evaluation & Engineering 1, no. 01 (February 1, 1998): 64–68. http://dx.doi.org/10.2118/36527-pa.
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Summary Transient pressure data are often collected at various points in the wellbore, including the wellhead, for test interpretation. When data gathering takes place at a point other than the midpoint of producing (MPP) interval, either inadvertently or by design, serious interpretation problems may arise because of wellbore thermal effects. Many field tests conducted on gas, oil, and water injection wells show the severity of this wellbore-induced problem. This paper explores the consequences of thermal effects upon test analysis in some cases and presents new insights into both data collection and their interpretation. Existing methods do not capture the borehole physics to allow us to study this problem. We present interesting synthetic and field cases. One field example shows that pressure actually can decrease during buildup tests in a gas well in a high-transmissivity reservoir. In this test, data were collected about 1,200 ft above the MPP in a 9,000-ft well because of mechanical restrictions downhole. We reproduced this observed behavior with the simulator. Pressure decrease in a buildup is caused by the dominating influence of thermal diffusion over pressure diffusion in a high-transmissivity system when measurements are made away from the MPP. For the same reason, pressure increases during a drawdown test. Equally important, results of the computation show that even if data were collected at the MPP, the gauge's ability to resolve small changes in pressure would have been tested severely. Introduction Pressure transient testing as practiced today is rooted in fundamental works of Muskat,1 van Everdingen and Hurst,2 Theis,3 Horner,4 and Miller et al.5 Hundreds of papers have been published since the early 1950's to address many issues, such as characterizing lateral and vertical reservoir heterogeneity, completion as related to hydraulic fractures and partial completion, and flow of multiphase fluids. Wellbore-induced problems, such as storage,6 masking the early-time data, and phase segregation,7 were also recognized early on. Despite the plethora of publications, very few papers have discussed issues related to pressure sensors used to collect transient data. In other words, integrity of pressure sensors is always implicit in any modeling and data analysis. Use of mechanical recorders of the bourdon gauge type dawned the beginning of data collection. In the past, poor resolution of mechanical sensors, especially while testing high-transmissivity formations, rendered many tests unworthy of analysis. Introduction of digital quartz sensors in the early 1970's paved the way for improved field application of both single-well multitransient and multiwell pulse testing. These sensors, while having superior ability to resolve small changes in pressure, have their own problems. Some of these problems8,9 relate to short- and long-term gauge drift, hysteresis, and large step changes in pressure and/or temperature. Gauge resolution and data-sampling frequency, however, are tied to the data transmission capacity of an acquisition system.10 Use of permanent11,12 downhole pressure sensors with increasing frequency is a testament to the continuous improvement of this technology. Analytic models have been the backbone for routine transient data interpretation, aided by ever-improving downhole data acquisition with quartz sensors. In a typical analytic wellbore/reservoir coupling, we have a rigorous reservoir or pD model and a simplistic nonphysical wellbore model describing transient fluid flow in the reservoir and wellbore, respectively. While interpreting, we assume implicitly that the acquired data reflect information from an isothermal reservoir. That assumption generally holds if the gauge is placed across perforations, preferably at the MPP. Only Joule-Thompson heating or cooling can introduce temperature change in the fluid. Clearly, the simple analytic formulation is not designed to study cases when gauges are hung higher up in the wellbore. Here, considerable heat transfer can occur between the hot reservoir fluids and the cold formation as a gauge is placed at increasing distance away from the MPP. Consequently, pressure data may not be interpretable by conventional methods. Method Used To study the wellbore-induced transient flow problems, we developed and reported13–15 a number of coupled wellbore/reservoir simulators that conserve mass, momentum, and energy in the wellbore. These simulators can handle single-phase gas,13 oil,14 and two-phase15 gas-oil flow problems. Conductive heat transport occurs through the tubular, annular fluid, cement sheath and into the formation, while convective heat transport occurs through the tubular and annular fluids. Similarly, heat transfer also can take place through the seawater and air for an offshore well. Joule-Thompson heating or cooling of fluids in the wellbore is also modeled. In this formulation, we treat the reservoir-fluid flow analytically and the wellbore heat and fluid flows numerically. Measured-temperature transients suggest that the gauge carrier stores or releases heat just as the tubulars do. We used an innovative approach to model the combined gauge and carrier response. Thus, in our method, we match both pressure, p, and temperature, T, transients to capture the wellbore physics at both ends of the wellbore, wellhead and downhole. In other words, when both p and T transients are matched by forward simulation, dynamics of fluid density in the entire well column are captured, leading to reliable solutions. We also resort to reverse simulations (i.e., translate either the wellhead or the off-bottom downhole data to the MPP for interpretation). Example Applications First, we present a synthetic example involving two-phase wellbore flow. Thereafter, we discuss two field cases, one involving single-phase gas flow and the other experiencing single-phase liquid flow throughout the wellbore. Example 1 - Synthetic Two-Phase Case. We simulated two cases with the two-phase simulator. In the first case, two-phase flow dominates nearly the entire 4,475-ft wellbore. By contrast, two-phase flow is confined toward the well top in an 11,500-ft well producing a highly undersaturated oil. Table 1 reports some relevant parameters for both cases. Fig. 1 presents the buildup transients after a producing time of 350 hours. Here, the gauge is placed about 1,400 ft above the MPP in this wellbore, producing from a high-transmissivity formation. Fig. 2 shows the characteristic dip in the derivative, induced by thermal storage. This signature often can be confused with that of a reservoir with dual-porosity or -permeability type. Clearly, correct gauge placement is essential to avoid misdiagnosis of a reservoir system. In the second example, the gauge is placed at various depths, including at the wellhead and the MPP, in a deep well. For clarity, we present only the derivative signatures. As Fig. 3 shows, the derivative signature exhibits larger excursion from the plateau as the gauge moves higher up in the borehole. Example 1 - Synthetic Two-Phase Case. We simulated two cases with the two-phase simulator. In the first case, two-phase flow dominates nearly the entire 4,475-ft wellbore. By contrast, two-phase flow is confined toward the well top in an 11,500-ft well producing a highly undersaturated oil. Table 1 reports some relevant parameters for both cases. Fig. 1 presents the buildup transients after a producing time of 350 hours. Here, the gauge is placed about 1,400 ft above the MPP in this wellbore, producing from a high-transmissivity formation. Fig. 2 shows the characteristic dip in the derivative, induced by thermal storage. This signature often can be confused with that of a reservoir with dual-porosity or -permeability type. Clearly, correct gauge placement is essential to avoid misdiagnosis of a reservoir system. In the second example, the gauge is placed at various depths, including at the wellhead and the MPP, in a deep well. For clarity, we present only the derivative signatures. As Fig. 3 shows, the derivative signature exhibits larger excursion from the plateau as the gauge moves higher up in the borehole.
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Pujol, J., B. N. Fuller, and S. B. Smithson. "Interpretation of a vertical seismic profile conducted in the Columbia Plateau basalts." GEOPHYSICS 54, no. 10 (October 1989): 1258–66. http://dx.doi.org/10.1190/1.1442585.
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Seismic reflection data are often of poor quality when recorded in areas where volcanic rocks are present at or near the surface. In order to investigate this phenomenon, a vertical seismic profiling (VSP) experiment was conducted in the Columbia Plateau basalts so that the behavior of seismic energy in subsurface volcanic rocks could be observed directly, thus giving insight into data acquisition in volcanic terrains. The lithologic section at the VSP site consists of low‐velocity (400 m/s to 900 m/s) alluvium in the uppermost 50 m, beneath which are layers of high‐velocity (about 5800 m/s), high‐density basalts interbedded with clay layers with much lower velocities (about 1700 m/s) and densities. These large velocity and density contrasts dramatically influence wave generation and propagation. In spite of the small source‐borehole offset (61 m), large‐amplitude S waves are generated by the downgoing P waves when they reach a shallow (250 m) clay‐basalt boundary. These S waves, in turn, generate strong reflected P waves when they interact with another clay layer at 500 m. On the other hand, strong primary P‐wave reflections are also present in the data but are affected by various interfering effects which reduce their amplitudes. The VSP data are also characterized by large‐amplitude reverberations caused by seismic energy trapped in the upper 250 m of the lithologic section. Reverberations are also observed in surface data recorded near the VSP site. We conclude from our analysis that volcanic rocks, at least in the Columbia Plateau, do not exhibit unusual energy transmission characteristics and that the observations can be explained in terms of the large contrast in the elastic properties of interbedded clay and basalt.
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Feizi, Faranak, Amir Abbas Karbalaei-Ramezanali, and Sasan Farhadi. "Application of multivariate regression on magnetic data to determine further drilling site for iron exploration." Open Geosciences 13, no. 1 (January 1, 2021): 138–47. http://dx.doi.org/10.1515/geo-2020-0165.
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Abstract In this study, a new approach of the multivariate regression model has been applied to make a precise mathematical model to determine further drilling for the detailed iron exploration in the Koohbaba area, Northwest of Iran. Furthermore, to figure out the additional drilling locations, the ore length to the total core ratio for the drilled boreholes has been used based on the geophysical exploration dataset. Hence, different regression analyses including linear, cubic, and quadratic models have been applied. In this study, the ore length to the total core ratio of the chosen drilled boreholes has been considered as a dependent variable; besides, the outputs of the magnetic data using the UP10 (10m upward-continuation), RTP (reduction to the pole), and A.S. (analytic signal) techniques have been designated as independent variables. Based on probability value (p-value), coefficients of determination (R 2 and R adj 2 {R}_{\text{adj}}^{2} ), and efficiency formula (EF), the fourth regression model has revealed the best results. The accuracy of the model has been confirmed by the defined ratio of boreholes and demonstrated by four additional drilled boreholes in the study area. Therefore, the results of the regression analysis are reasonable and can be used to determine the additional drilling for the detailed exploration.
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Brohi, Imad Ali, Muzafar Ali Kalwar, Muhammad Hassan Agheem, Shafique Ahmad Junejo, and Ali Ghulam Sahito. "Study of Geotechnical Assessments for The Foundation and Construction of Civil Work at Tharparkar District, Sindh, Pakistan." International Journal of Economic and Environmental Geology 11, no. 4 (March 11, 2021): 18–21. http://dx.doi.org/10.46660/ijeeg.vol11.iss4.2020.510.
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This study evaluates engineering properties of soils for the foundation in Tharparkar district. Three boreholes were investigated in the study area at the depths of 8m, 9m and 9m respectively. The area is mainly divided into three zones, i.e. BH-01, BH-02 and BH-03. Groundwater was not encountered in any borehole. The soil profile of all three boreholes are low dense to medium dense at 2.0m to 6.0m and the 7.0m to 9.0m depths respectively. Overburden depth was very dense (N-values ranges from 8 to 17 and 33 to more than 50 numbers). Laboratory results reveal that moisture content goes 4.8 to 6.4%, Soils are non-plastic in all three boreholes. The granular soils specify the angles of internal friction (ø) varying from 240 – 330in respective boreholes; while in the collected samples granular soils have cohesion of 2.4 to 2.5kPa. According to AASHTO soil classification, the material belongs to the type of granular soil and in the group of A-3. Furthermore, finding of the examinations is robust for the development of structures, transmission line foundations and other civil works to observe the stability and quality of good foundation for the most part in Thar zone, particularly in the studied area.
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Li, Yaoguo, and Douglas W. Oldenburg. "Joint inversion of surface and three‐component borehole magnetic data." GEOPHYSICS 65, no. 2 (March 2000): 540–52. http://dx.doi.org/10.1190/1.1444749.
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The inversion of magnetic data is inherently nonunique with respect to the distance between the source and observation locations. This manifests itself as an ambiguity in the source depth when surface data are inverted and as an ambiguity in the distance between the source and boreholes if borehole data are inverted. Joint inversion of surface and borehole data can help to reduce this nonuniqueness. To achieve this, we develop an algorithm for inverting data sets that have arbitrary observation locations in boreholes and above the surface. The algorithm depends upon weighting functions that counteract the geometric decay of magnetic kernels with distance from the observer. We apply these weighting functions to the inversion of three‐component magnetic data collected in boreholes and then to the joint inversion of surface and borehole data. Both synthetic and field data sets are used to illustrate the new inversion algorithm. When borehole data are inverted directly, three‐component data are far more useful in constructing good susceptibility models than are single‐component data. However, either can be used effectively in a joint inversion with surface data to produce models that are superior to those obtained by inversion of surface data alone.
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Winbow, G. A. "Seismic sources in open and cased boreholes." GEOPHYSICS 56, no. 7 (July 1991): 1040–50. http://dx.doi.org/10.1190/1.1443112.
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Theoretical modeling, based on the equations of linear elasticity, is used to analyze the performance of downhole seismic sources, specifically, symmetrical radial sources which exert outward pressure on a length of the borehole wall and vertically driven sources clamped to the borehole wall. Torsional sources radiate pure S-waves whose form is independent of the existence of the borehole, and therefore requires no special discussion. The radial sources discussed are airguns, waterguns, and implosive sources. Such sources are in widespread use and development at present. From the calculations we find that radial sources emit almost all (>99 percent) their energy as tube‐waves which travel along the borehole and not out into the formation. Vertical sources radiate almost all their energy into the formation as P- and S-waves. However, if the casing bond slips, the vertical sources lose efficiency and radiate energy as extensional waves along the casing. The radial sources are little affected by the quality of cement bonding. Radial sources may be used at or near the surface to direct tube‐waves down the hole. Conversion of the tube‐waves to P-waves and S-waves either from the end of the hole or from a specially configured converter such as a constriction placed in the hole theoretically represents a viable downhole seismic source for reversed VSP (RVSP) and crosshole imaging. Little energy is lost in tube wave transmission and high acoustic power may be injected into a well.
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Doetsch, Joseph A., Ilaria Coscia, Stewart Greenhalgh, Niklas Linde, Alan Green, and Thomas Günther. "The borehole-fluid effect in electrical resistivity imaging." GEOPHYSICS 75, no. 4 (July 2010): F107—F114. http://dx.doi.org/10.1190/1.3467824.
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Fluid that fills boreholes in crosswell electrical resistivity investigations provides the necessary electrical contact between the electrodes and the rock formation but it is also the source of image artifacts in standard inversions that do not account for the effects of the boreholes. The image distortions can be severe for large resistivity contrasts between the rock formation and borehole fluid and for large borehole diameters. We have carried out 3D finite-element modeling using an unstructured-grid approach to quantify the magnitude of borehole effects for different resistivity contrasts, borehole diameters, and electrode configurations. Relatively common resistivity contrasts of 100:1 and borehole diameters of 10 and [Formula: see text] yielded, for a bipole length of [Formula: see text], apparent resistivity underestimates of approximately 12% and 32% when using AB-MN configurations and apparent resistivity overestimates of approximately 24% and 95% when usingAM-BN configurations. Effects are generally more severe at shorter bipole spacings. We report the results obtained by either including or ignoring the boreholes in inversions of 3D field data from a test site in Switzerland, where approximately 10,000 crosswell resistivity-tomography measurements were made across six acquisition planes among four boreholes. Inversions of raw data that ignored the boreholes filled with low-resistivity fluid paradoxically produced high-resistivity artifacts around the boreholes. Including correction factors based on the modeling results for a 1D model with and without the boreholes did not markedly improve the images. The only satisfactory approach was to use a 3D inversion code that explicitly incorporated the boreholes in the actual inversion. This new approach yielded an electrical resistivity image that was devoid of artifacts around the boreholes and that correlated well with coincident crosswell radar images.
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Fenta, Mulugeta C., David K. Potter, and János Szanyi. "Fibre Optic Methods of Prospecting: A Comprehensive and Modern Branch of Geophysics." Surveys in Geophysics 42, no. 3 (March 9, 2021): 551–84. http://dx.doi.org/10.1007/s10712-021-09634-8.
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AbstractOver the past decades, the development of fibre optic cables, which pass light waves carrying data guided by total internal reflection, has led to advances in high-speed and long-distance communication, large data transmission, optical imaging, and sensing applications. Thus far, fibre optic sensors (FOSs) have primarily been employed in engineering, biomedicine, and basic sciences, with few reports of their usage in geophysics as point and distributed sensors. This work aimed at reviewing the studies on the use of FOSs in geophysical applications with their fundamental principles and technological improvements. FOSs based on Rayleigh, Brillouin, and Raman scatterings and fibre Bragg grating sensors are reviewed based on their sensing performance comprising sensing range, spatial resolution, and measurement parameters. The recent progress in applying distributed FOSs to detect acoustic, temperature, pressure, and strain changes, as either single or multiple parameters simultaneously on surface and borehole survey environments with their cable deployment techniques, has been systematically reviewed. Despite the development of fibre optic sensor technology and corresponding experimental reports of applications in geophysics, there have not been attempts to summarise and synthesise fibre optic methods for prospecting as a comprehensive and modern branch of geophysics. Therefore, this paper outlines the fibre optic prospecting methods, with an emphasis on their advantages, as a guide for the geophysical community. The potential of the new outlined fibre optic prospecting methods to revolutionise conventional geophysical approaches is discussed. Finally, the future challenges and limitations of the new prospecting methods for geophysical applications are elucidated.
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Oristaglio, Michael L. "A guide to current uses of vertical seismic profiles." GEOPHYSICS 50, no. 12 (December 1985): 2473–79. http://dx.doi.org/10.1190/1.1441878.
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Vertical seismic profiles (VSPs) are small‐scale seismic surveys in which geophones are lowered into a well to record waves traveling both down into the earth (direct waves from the surface source and downgoing multiples) and back toward the surface (primary reflections and upgoing multiples). VSPs thus contain information about the reflection and transmission properties of the earth with a coverage that depends upon the geometry of the VSP experiment and the structure near the well. This article describes the uses of VSPs in seismic exploration that have been published in the last three years and is designed to complement the more detailed surveys by Hardage (1983) and Balch and Lee (1984). When the earth is horizontally layered, the well is vertical, and the source is close to the wellhead, upgoing and downgoing waves recorded by the VSP travel vertically, and the VSP can be used to calibrate surface seismic sections by providing the time‐to‐depth curve and allowing a detailed analysis of reflection and transmission properties of the earth at a given location. These applications rely heavily on signal processing to separate the upgoing and downgoing waves and to study their relationships to data recorded at the surface. When the earth varies laterally or when the source is offset from the well, the VSP can be used to complement surface surveys by providing high‐resolution images of structure near the well. Current work has concentrated on forming images from the reflected waves by the methods of common‐depth‐point (CDP) stacking and migration. Tomographic methods for inverting the traveltimes and amplitudes of transmitted waves are also being developed and will become important when downhole arrays and powerful downhole sources are available. The most significant advance in the next few years, however, will be the development of a reliable three‐axis tool with internal devices for determining both the orientation of the tool and the quality of its coupling to the borehole wall.
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Daneshvar Saein, Lili, Iraj Rasa, Nematolah Rashidnejad Omran, Parviz Moarefvand, Peyman Afzal, and Behnam Sadeghi. "Application of Number-Size (N-S) Fractal Model to Quantify of the Vertical Distributions of Cu and Mo in Nowchun Porphyry Deposit (Kerman, Se Iran) / Zastosowanie modelu fraktalnego n-s (liczba-rozmiar) do ilościowego określenia pionowego rozkładu Cu i Mo w złożu porfirowym (Kerman, Iran)." Archives of Mining Sciences 58, no. 1 (March 1, 2013): 89–105. http://dx.doi.org/10.2478/amsc-2013-0006.
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Determination of the vertical distribution of geochemical elemental concentrations is of fundamental importance in mineral exploration. In this paper, eight mineralized boreholes from the Nowchun Cu-Mo porphyry deposit, SE Iran, were used to identify of the vertical distribution directional properties of Cu and Mo values using number-size (N-S) fractal model. The vertical distributions of Cu and Mo in the mineralized boreholes show a positively skewed distribution in the former and a multimodal distribution in the latter types. Elemental threshold values for the mineralized boreholes were computed by fractal model and compared with the statistical methods based on the data obtained from chemical analysis of samples. Elemental distributions are not normal in these boreholes and their median equal to Cu and Mo thresholds. The results of N-S fractal analysis reveal that Cu and Mo values in mineralized boreholes are multifractals in nature. There are at least three geochemical populations for Cu and Mo in the boreholes and Cu and Mo thresholds have ranges between 0.07%-0.3% and 50-200 ppm, respectively. The results obtained by N-S fractal model were compared with geological observations in the boreholes. Major Cu and Mo enrichment correlated by monzonitic rocks and high amounts of observed Cu and Mo ores (Chalcopyrite and molybdenite) in the boreholes.
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Nwachukwu, Patrick Chinyeaka, BON C. OKORO, JOACHIM CHINONYE OSUAGWU, and STEVE I. NWANKWO. "Correlation of Surface Geophysical and Logging Data of Some Selected Boreholes in Imo State, South Eastern Nigeria." Journal of Geography and Geology 7, no. 4 (December 2, 2015): 1. http://dx.doi.org/10.5539/jgg.v7n4p1.
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Boreholes have become a major source of water supply in South Eastern Nigeria, an area with diversity in geology, topography and climatic conditions. The common approaches in borehole investigations are surface survey and logging. The two approaches are supposed to be complementary. However, for small schemes of groundwater development, logging is hardly considered.. Six boreholes were selected from locations at the three geographical zones of Imo state. The selected locations are Umueze, Umuduru, Ogbor-Ugiiri, Ngor Okpuala and Eziama. Geophysical survey and logging were carried out. Electrical resistivity method was adapted for geophysical survey. ABEM Terrameter (SAS) 300B with digital read-out was used for logging. The degree of correlation between the variables was determined by computing the coefficient of correlation denoted as R<sup>2</sup>. The results indicate generally poor correlations between logging and geophysical surface values for the selected boreholes except for the one located at Ngor Okpala with R<sup>2</sup> value of 0.7408. At this location, geophysical surface method for borehole locations can be carried without any Logging exercise to establish the Total Drilling Depth (TDD). This will help reduce the total cost for the drilling of the boreholes and also save time and much desired energy. In those areas where no correlation exists, there is need for Government Financial support in drilling sustainable borehloes as much costs are involved in investigation and construction works.
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Hunze, Sabine, and Thomas Wonik. "Sediment Input into the Heidelberg Basin as determined from Downhole Logs." E&G Quaternary Science Journal 57, no. 3/4 (April 1, 2009): 367–81. http://dx.doi.org/10.3285/eg.57.3-4.5.
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Abstract. The Upper Rhine Graben, and the Heidelberg Basin in particular, play an important role in the investigation of climate change and tectonic activity during the Tertiary and Quaternary periods. Several research boreholes were recently drilled to acquire data for a new interpretation of the geology of the northern Upper Rhine Graben. This paper investigates in detail the boreholes at Heidelberg, Viernheim and Ludwigshafen-Parkinsel, as well as the shallower boreholes at Pfungstadt, Stadtwerke Viernheim and Hüttenfeld, in terms of their geophysical parameters. The physical properties of the lithologies described in the cores are characterised on the basis of borehole logging data. A hole-to-hole correlation between adjacent boreholes is then conducted, using the characteristic changes in the ‘natural radioactivity’ parameter to acquire information on changes in sediment provenance (Rhine, Neckar, Pfälzerwald and Odenwald). An interpretation applying the statistical method of cluster analysis allows identifi cation of sections with homogenous physical properties from downhole measurements and thus the determination of possible sediment provenance.
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Pallikarakis, A., I. Papanikolaou, M. Triantaphyllou, C. Grützner, G. Migiros, K. Reicherter, J. Mason, and S. Schneiderwind. "MAGNETIC SUSCEPTIBILITY CHANGES CORRELATED WITH PALEOENVIRONMENTAL AND LITHOLOGICAL CHANGES, WITHIN BOREHOLE CORES ON EITHER SIDES OF THE KALAMAKI-ISTHMIA FAULT IN CORINTH CANAL." Bulletin of the Geological Society of Greece 50, no. 1 (July 27, 2017): 104. http://dx.doi.org/10.12681/bgsg.11706.
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Τhe most important active fault that intersects the eastern tip of Corinth Canal,the Kalamaki-Isthmia fault, is studied in detail, involving data analysis from nine boreholes, magnetic susceptibility measurements within boreholes and paleoenvironmental interpretations. Samples taken from boreholes were analysed and paleoenvironmental changes in the sequence are described. We correlate magnetic susceptibility (MS) measurements with paleoenvironmental and lithological alternations within the boreholes. We have ascribed low MS values to marine highstand deposits and high MS values to lowstand terrestrial deposits. Glacioeustatic sea level changes and tectonic movements have led to a very complicated lithosedimentary pattern that involves subaerial exposure, fluvialterrestrial, lagoonal, shallow marine environments and possibly even some lake sediments. Our results indicate that the Kalamaki fault is active and has a low slip rate of 0.05±0.02 mm/yr.
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Kononenko, M. M., O. Ye Khomenko, I. L. Kovalenko, and M. V. Savchenko. "Control of density and velocity of emulsion explosives detonation for ore breaking." Naukovyi Visnyk Natsionalnoho Hirnychoho Universytetu, no. 2 (2021): 69–75. http://dx.doi.org/10.33271/nvngu/2021-2/069.
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Purpose.Development of a new procedure for calculating the density of emulsion explosives (EE), that will allow determining the detonation velocity along the charging length, depending on the inclination of boreholes during ore breaking. Methodology.A calculation method for the redistribution of EE density and mass in boreholes at different angles of inclination has been developed by using the well-known laws of hydrostatics. Measurement of the detonation velocity of the EE Ukrainit-PP-2B was conducted by using the method of polygon experimental tests. The numerical simulation of changes in the detonation velocity of explosives in boreholes was conducted by using the proposed method and established regularities. Findings.Methods of calculation of EE density changing along the charging column length under the action of hydrostatic pressure at different angles of inclination of both ascending and descending boreholes have been developed. Based on experimental data, regularities of detonation rate changing from density and charge diameter for EE Ukrainit-PP-2B, varying according to exponential law have been established. The rational initial density of EE Ukrainit-PP-2B has been established for ores breaking by boreholes, which is equal to 8001000 kg/m3, at which the detonation rate along the length of the charge column at different angles of inclination of the boreholes is maintained. The obtained results will allow controlling density and detonation velocity during ore breaking. Originality.The density of EE increases in the formed charging column under the action of hydrostatic pressure: in ascending boreholes from the face, while in descending boreholes from the brow. Practical value.Application of the calculation results of EE density at different inclination angles of boreholes makes it possible to determine in the charge column sections with its critical values more than 1410 kg/m3, at which a sharp attenuation of the detonation rate begins. Consideration of this phenomenon makes it possible to prevent the occurrence of failures at the explosion of charges in boreholes during ore breaking.
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Robinson, Judith, Timothy Johnson, and Lee Slater. "Challenges and opportunities for fractured rock imaging using 3D cross-borehole electrical resistivity." GEOPHYSICS 80, no. 2 (March 1, 2015): E49—E61. http://dx.doi.org/10.1190/geo2014-0138.1.
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There is an increasing need to characterize discrete fractures away from boreholes to better define fracture distributions and monitor solute transport. We performed a 3D evaluation of static and time-lapse cross-borehole electrical resistivity tomography (ERT) data sets from a limestone quarry in which flow and transport are controlled by a bedding-plane feature. Ten boreholes were discretized using an unstructured tetrahedral mesh, and 2D panel measurements were inverted for a 3D distribution of conductivity. We evaluated the benefits of 3D versus 2.5D inversion of ERT data in fractured rock while including the use of borehole regularization disconnects (BRDs) and borehole conductivity constraints. High-conductivity halos (inversion artifacts) surrounding boreholes were removed in static images when BRDs and borehole conductivity constraints were implemented. Furthermore, applying these constraints focused transient changes in conductivity resulting from solute transport on the bedding plane, providing a more physically reasonable model for conductivity changes associated with solute transport at this fractured rock site. Assuming bedding-plane continuity between fractures identified in borehole televiewer data, we discretized a planar region between six boreholes and applied a fracture regularization disconnect (FRD). Although the FRD appropriately focused conductivity changes on the bedding plane, the conductivity distribution within the discretized fracture was nonunique and dependent on the starting homogeneous model conductivity. Synthetic studies performed to better explain field observations showed that inaccurate electrode locations in boreholes resulted in low-conductivity halos surrounding borehole locations. These synthetic studies also showed that the recovery of the true conductivity within an FRD depended on the conductivity contrast between the host rock and fractures. Our findings revealed that the potential exists to improve imaging of fractured rock through 3D inversion and accurate modeling of boreholes. However, deregularization of localized features can result in significant electrical conductivity artifacts, especially when representing features with a high degree of spatial uncertainty.
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Morin, Roger H., Guillaume E. Descamps, and L. DeWayne Cecil. "Acoustic televiewer logging in glacier boreholes." Journal of Glaciology 46, no. 155 (2000): 695–99. http://dx.doi.org/10.3189/172756500781832684.
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AbstractThe acoustic televiewer is a geophysical logging instrument that is deployed in a water-filled borehole and operated while trolling. It generates a digital, magnetically oriented image of the borehole wall that is developed from the amplitudes and transit times of acoustic waves emitted from the tool and reflected at the water–wall interface. The transit-time data are also converted to radial distances, from which cross-sectional views of the borehole shape can be constructed. Because the televiewer is equipped with both a three-component magnetometer and a two-component inclinometer, the borehole’s trajectory in space is continuously recorded as well. This instrument is routinely used in mining and hydrogeologic applications, but in this investigation it was deployed in two boreholes drilled into Upper Fremont Glacier, Wyoming, U.S.A. The acoustic images recorded in this glacial setting are not as clear as those typically obtained in rocks, due to a lower reflection coefficient for water and ice than for water and rock. Results indicate that the depth and orientation of features intersecting the boreholes can be determined, but that interpreting their physical nature is problematic and requires corroborating information from inspection of cores. Nevertheless, these data can provide some insight into englacial structural characteristics. Additional information derived from the cross-sectional geometry of the borehole, as well as from its trajectory, may also be useful in studies concerned with stress patterns and deformation processes.
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Hou, Shao Jie, Yu Wei Zhang, and Yuan Ping Cheng. "A Novel Tracking and Warning Method for Gas Pre-Drainage Project Based on X-Rs Control Chart." Advanced Materials Research 868 (December 2013): 361–64. http://dx.doi.org/10.4028/www.scientific.net/amr.868.361.
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To well develop coal gas and prevent gas outburst accidents, gas pre-drainage project has become the prerequisite of coal mining in underground collieries. Its construction quality determined drainage effect as well as touched miners lives closely. Based on the X-Rs control chart, a novel tracking and warning method for the gas pre-drainage project was proposed. Firstly, the data structure of upward cross-seam boreholes that were widely used in gas pre-drainage project was built. As time went by, the construction data of boreholes formed multivariable time series. Using the difference transformation between construction and design, the inspection data series of boreholes construction was designed. After that, the complete X-Rs control chart was implemented, in which by three types of anomaly characteristics the tracking and warning of the construction quality was accomplished.
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McMillan, Michael S., and Douglas W. Oldenburg. "Cooperative constrained inversion of multiple electromagnetic data sets." GEOPHYSICS 79, no. 4 (July 1, 2014): B173—B185. http://dx.doi.org/10.1190/geo2014-0029.1.
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We evaluated a method for cooperatively inverting multiple electromagnetic (EM) data sets with bound constraints to produce a consistent 3D resistivity model with improved resolution. Field data from the Antonio gold deposit in Peru and synthetic data were used to demonstrate this technique. We first separately inverted field airborne time-domain EM (AEM), controlled-source audio-frequency magnetotellurics (CSAMT), and direct current resistivity measurements. Each individual inversion recovered a resistor related to gold-hosted silica alteration within a relatively conductive background. The outline of the resistor in each inversion was in reasonable agreement with the mapped extent of known near-surface silica alteration. Variations between resistor recoveries in each 3D inversion model motivated a subsequent cooperative method, in which AEM data were inverted sequentially with a combined CSAMT and DC data set. This cooperative approach was first applied to a synthetic inversion over an Antonio-like simulated resistivity model, and the inversion result was both qualitatively and quantitatively closer to the true synthetic model compared to individual inversions. Using the same cooperative method, field data were inverted to produce a model that defined the target resistor while agreeing with all data sets. To test the benefit of borehole constraints, synthetic boreholes were added to the inversion as upper and lower bounds at locations of existing boreholes. The ensuing cooperative constrained synthetic inversion model had the closest match to the true simulated resistivity distribution. Bound constraints from field boreholes were then calculated by a regression relationship among the total sulfur content, alteration type, and resistivity measurements from rock samples and incorporated into the inversion. The resulting cooperative constrained field inversion model clearly imaged the resistive silica zone, extended the area of interpreted alteration, and also highlighted conductive zones within the resistive region potentially linked to sulfide and gold mineralization.
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Monnier, Sébastien, and Christophe Kinnard. "Internal structure and composition of a rock glacier in the Andes (upper Choapa valley, Chile) using borehole information and ground-penetrating radar." Annals of Glaciology 54, no. 64 (2013): 61–72. http://dx.doi.org/10.3189/2013aog64a107.
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Abstract This study uses boreholes, ground temperature monitoring and ground-penetrating radar (GPR) in order to understand the internal structure and composition of a rock glacier in the upper Choapa valley, northern Chile. The rock glacier is a small valley-side feature, 200 m long and ranging between 3710 and 3780 ma.s.l. Two boreholes were drilled down to depths of 20 and 25 m, respectively, using the diamond drillhole technique. An ice-rock mixture was encountered in the boreholes, with heterogeneous ice content averaging 15-30%. Data from common-midpoint (CMP) and constant-offset (CO) GPR surveys acquired, respectively, near the boreholes and across the whole rock glacier were processed to highlight the internal stratigraphy and variations in the radar-wave velocity. The GPR profiles depict a rock glacier constituted of stacked and generally concordant layers, with a thickness ranging from 10 m in its upper part to ∼30m towards its terminus. The CMP analysis highlights radar-wave velocities of 0.13-0.16 m ns–1 in the first 20 m of the structure. Larger vertical and lateral velocity variations are highlighted from CO data, reflecting the heterogeneous composition of the rock glacier and the likely presence of unfrozen water in the structure. Given the average air temperature registered at the site (+0.5°C), the near-melting-point temperature registered in the boreholes over more than a year and the presence of locally high water content inferred from GPR data, it is thought that the permafrost in the rock glacier is currently degrading.