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Dissertations / Theses on the topic 'Rock physics; Seismic data'
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Said, Dhiya Mustafa Mohamed. "Reservoir geophysics of the Clyde field : the development and application of quantitative analysis techniques." Thesis, University of Aberdeen, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.327396.
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Fanka, Walter Roye Taju. "Well Log and Seismic Data Interpretation : Rock Physics Study of Poorly Consolidated Sandstones in The North Sea." Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for petroleumsteknologi og anvendt geofysikk, 2012. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-18608.
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We use rock physics models for poorly consolidated rocks to diagnose reservoir sandstones in the Alvheim Field, North Sea. Geological factors that will control the rock physics and seismic properties include clay content, sorting, diagenesis, mineralogy, and bedding configuration. The various geologic factors will affect the fluid and stress sensitivity in these rocks. We investigate the interrelationships between various geological factors and seismic fluid and stress sensitivity, by combining well log data and rock physics models. Finally, we determine inter-well characteristics in terms of varying geological factors at different locations and discuss the results in terms of expected seismic signatures in the area.
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Yan, Jun. "Improved rock physical models for the integration of core, log and seismic data." Thesis, University of Edinburgh, 2003. http://hdl.handle.net/1842/11633.
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In this thesis, I propose the following: - The P and S-wave velocities can provide a suitable link between reservoir parameters and rock properties using core, log and seismic data. - The pore aspect ratios as key parameters of rock geometry can be used to explain the different responses of elastic properties in clay-sand rocks (especially for thin and varying lithology formations). The use of fixed aspect ratio for physical velocity models will result in obvious errors in the prediction of elastic moduli and velocities (in particular for formations at shallow depth, or in loose and thin layers). - The time-average equation (Wyllie et al., 1956) ignored the effects of pore geometry, degree of consolidation fluid and clay content. It results in a hidden defect in the transformation between porosity (form core and well-log) and velocity (from seismic) when the rock contains clay. - The current models of Gassmann (1951), Kuster & Toksöz (1974) and Xu-White (1995) have some difficulties in calculating elastic moduli for rocks containing aligned pores and minerals in anisotropic formations. To investigate these, I first use method of multiple regression and artificial networks to establish an empirical correlation between reservoir parameters and P and S-wave velocities. This correlation includes porosity, clay content, aspect ratio and velocities, which can be used as an extension of the empirical model of Han et al (1956). Second, in order to overcome the weakness of empirical models, physically realistic theoretical models are established. The first theoretical model is the isotropic dual porosity model (IDP). The aim of the IDP is to develop a general rock physical model that provides a satisfactory integrated approach to the evaluation and prediction of reservoir parameters and rock properties for the purpose of reservoir characterization. Third, because the IDP model does not consider the effects of pore orientation, clay content and velocity anisotropy etc., a refined anisotropic dual porosity model (ADP) is then developed for anisotropic porous media.
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Adrian, Jorge Isaac. "Applicability of rock physics models in conjunction with seismic inverted data to characterize a low poro-perm gas-bearing sandstone reservoir for well location optimization, Bredasdorp Basin, SA." Master's thesis, University of Cape Town, 2015. http://hdl.handle.net/11427/19963.
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The primary focus of this dissertation is to develop a predictive rock physics theory that establishes relations between rock properties and the observed seismic and to present the results of different seismic characterization techniques to interpret a tight gas sand reservoir off the south coast of South Africa using as input rock physics analysis and inverted seismic outcomes. To perform the aims and goals of this study a workflow that involves the execution of three main processes was implemented: (1) rock physics modelling, (2) a simultaneous seismic inversion, and (3) seismic reservoir characterization techniques. First, a rock physics model was generated as a bridge between the seismic observables (density, Vp and Vs) and reservoir parameters such as fluid content, porosity and mineralogy. In situ and perturbational log - derived forward modelling was performed. Both in situ and perturbational forward modelling were used to generate synthetic seismic gathers, which were used to study the AVA attribute responses. Overall, the effect of fluid fill on this tight gas sand seismically is modest compared with the effect of porosity changes. Second, there follows a detailed description of a workflow implemented to simultaneously invert P and S pre - stack seismic data. The derived elastic properties (acoustic impedance, Vp/Vs and density) were then used in combination with the rock physics analysis to characterize seismically the reservoir. The predicted acoustic impedance and Vp/Vs volumes show a good tie with the log data. However, the density outcome was of limited quality compared with the two mentioned above. Finally, using outcomes from rock physic s analysis and/or inverted data, four seismic techniques to characterize the reservoir were conducted. The techniques involved are: (1) AVO cross - plotting to generate a good facies property based on AVO attributes (intercept - gradient) and rock physics in the area of study , (2) rock physics templates (RPTs) to compute discrete rock property volumes (litho - Sw, litho - porosity) using a collection of curves that cover all possible "what if" lithology - fluid content - porosity scenarios for the reservoir and the inverted data, (3) a lithological classification to calculate litho - facies probability volumes based on a litho - facies classification using petrophysical cut - off s , multivariate probability functions (PDFs) and inverted data, and (4) an extended elastic impedance (EEI) inversion to derive rock property volumes (Vclay, porosity) based on AVO attributes (intercept, gradient). Despite differences in the input and theory behind each technique, all outcomes share parallels in the distribution of good and poor facies or reservoir and non - reservoir zones.
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Zhang, John Jianlin. "Time-lapse seismic surveys, rock physics basis." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2001. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp05/MQ65147.pdf.
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Hoang, Phuong. "Rock physics depth trend analysis using seismic stacking velocity." Thesis, Norwegian University of Science and Technology, Department of Petroleum Engineering and Applied Geophysics, 2006. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-1631.
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Quantitative seismic interpretation is becoming more and more important in exploration and characterization of petroleum reservoirs. In this technology, rock physic analysis combined with seismic attributes has become a key strategy.
Nature creates inhomogeneous anisotropic rocks where the rock physics properties vary at different positions and directions. It is important to analyze and quantify the property changes as a function of depositional and burial trends in order to improve our detectability of petroleum reservoirs from seismic data.
In this thesis, we have presented a new methodology to obtain rock physics properties as a function of burial depth, i.e., rock physics depth trends (RPDTs), from well log and seismic data. To obtain RPDTs, several authors have suggested using rock physics models calibrated to well log data or constrained by diagenetic models. We present an alternative way to extract these from seismic stacking velocities. This is the main focus of the thesis.
We apply our methodology to extract RPDTs from seismic stacking velocities in the Njord Field area, located in the Norwegian Sea. We find that the seismic interval velocity trend matches nicely to the sonic velocity at the well location, especially above Base Cretaceous. By combining empirical RPDTs with seismic RPDTs, we are able to interpret and quantify the rock properties of different rock physics events that have occurred in Njord Field at well location and in the areas without well log information.
In this thesis we have successfully demonstrated how stacking velocities can be used to improve our understanding about normal mechanical compaction trends, tectonic activity and diagenetic events. This information is important for improved overburden and reservoir characterization, especially in areas with sparse or no well log data.
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Gloria, Lopez Juan Carlos. "Integrating AVO, Seismic Inversion, and Rock Physics in Agua Fría 3D Seismic Cube." Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for petroleumsteknologi og anvendt geofysikk, 2014. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-26114.
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Ten exploratory wells have been drilled in the Agua Fría area, led by amplitude anomalies and structural highs. Five of them resulted in dry wells and the other five in gas and oil discoveries. In some of these wells, water sands respond seismically as amplitude anomalies. On the other hand, some oil and gas sands are not easily recognizable from post-stack seismic data. Bright spots are also observed in the study area.Seismic interpretation can be uncertain if no geology is related to elastic response of the subsurface rocks. The purpose of this thesis is to integrate diagenesis data from log and core data, rock physics models, AVO analysis and seismic inversion information to characterize the Agua Fría 3D seismic cube. Mechanical compaction and sorting are the main factors affecting the porosity trend in the selected wells according to the rock physics modeling. AVO class III are the main class present in the study area. However, these responses can be related to brine, oil or gas sands. Rock physics templates and seismic inversion data are useful to understand these responses and to decrease uncertainty to the analysis of these anomalies.The integration of these methodologies allow to improve the understanding of the seismic amplitude response to different geological facies present in the study area.
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Harrison, Christopher Bernard. "Feasibility of rock characterization for mineral exploration using seismic data." Curtin University of Technology, Western Australia School of Mines, Department of Exploration Geophysics, 2009. http://espace.library.curtin.edu.au:80/R/?func=dbin-jump-full&object_id=129417.
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The use of seismic methods in hard rock environments in Western Australia for mineral exploration is a new and burgeoning technology. Traditionally, mineral exploration has relied upon potential field methods and surface prospecting to reveal shallow targets for economic exploitation. These methods have been and will continue to be effective but lack lateral and depth resolution needed to image deeper mineral deposits for targeted mining. With global need for minerals, and gold in particular, increasing in demand, and with shallower targets harder to find, new methods to uncover deeper mineral reserves are needed. Seismic reflection imaging, hard rock borehole data analysis, seismic inversion and seismic attribute analysis all give the spatial and volumetric exploration techniques the mineral industry can use to reveal high value deeper mineral targets.In 2002, two high resolution seismic lines, the East Victory and Intrepid, were acquired along with sonic logging, to assess the feasibility of seismic imaging and rock characterisation at the St. Ives gold camp in Western Australia. An innovative research project was undertaken combining seismic processing, rock characterization, reflection calibration, seismic inversion and seismic attribute analysis to show that volumetric predictions of rock type and gold-content may be viable in hard rock environments. Accurate seismic imaging and reflection identification proved to be challenging but achievable task in the all-out hard rock environment of the Yilgarn craton. Accurate results were confounded by crocked seismic line acquisition, low signal-to-noise ratio, regolith distortions, small elastic property variations in the rock, and a limited volume of sonic logging. Each of these challenges, however, did have a systematic solution which allowed for accurate results to be achieved.
Seismic imaging was successfully completed on both the East Victory and Intrepid data sets revealing complex structures in the Earth as shallow as 100 metres to as deep as 3000 metres. The successful imaging required homogenization of the regolith to eliminate regolith travel-time distortions and accurate constant velocity analysis for reflection focusing using migration. Verification of the high amplitude reflections within each image was achieved through integration of surface geological and underground mine data as well as calibration with log derived synthetic seismograms. The most accurate imaging results were ultimately achieved on the East Victory line which had good signal-to-noise ratio and close-to-straight data acquisition direction compared to the more crooked Intrepid seismic line.
The sonic logs from both the East Victory and Intrepid seismic lines were comprehensively analysed by re-sampling and separating the data based on rock type, structure type, alteration type, and Au assay. Cross plotting of the log data revealed statistically accurate separation between harder and softer rocks, as well as sheared and un-sheared rock, were possible based solely on compressional-wave, shear-wave, density, acoustic and elastic impedance. These results were used successfully to derive empirical relationships between seismic attributes and geology. Calibrations of the logs and seismic data provided proof that reflections, especially high-amplitude reflections, correlated well with certain rock properties as expected from the sonic data, including high gold content sheared zones. The correlation value, however, varied with signal-to-noise ratio and crookedness of the seismic line. Subsequent numerical modelling confirmed that separating soft from hard rocks can be based on both general reflectivity pattern and impedance contrasts.
Indeed impedance inversions on the calibrated seismic and sonic data produced reliable volumetric separations between harder rocks (basalt and dolerite) and softer rock (intermediate intrusive, mafic, and volcaniclastic). Acoustic impedance inversions produced the most statistically valid volumetric predictions with the simultaneous use of acoustic and elastic inversions producing stable separation of softer and harder rocks zones. Similarly, Lambda-Mu-Rho inversions showed good separations between softer and harder rock zones. With high gold content rock associated more with “softer” hard rocks and sheared zones, these volumetric inversion provide valuable information for targeted mining. The geostatistical method applied to attribute analysis, however, was highly ambiguous due to low correlations and thus produced overly generalized predictions. Overall reliability of the seismic inversion results were based on quality and quantity of sonic data leaving the East Victory data set, again with superior results as compared to the Intrepid data set.
In general, detailed processing and analysis of the 2D seismic data and the study of the relationship between the recorded wave-field and rock properties measured from borehole logs, core samples and open cut mining, revealed that positive correlations can be developed between the two. The results of rigorous research show that rock characterization using seismic methodology will greatly benefit the mineral industry.
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Rimstad, Kjartan. "Bayesian Seismic Lithology/Fluid Inversion Constrained by Rock Physics Depth Trends." Thesis, Norwegian University of Science and Technology, Department of Mathematical Sciences, 2008. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-9772.
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In this study we consider 2D seismic lithology/fluid inversion constrained by rock physics depth trends and a prior lithology/fluid Markov random field. A stochastic relation from porosity and lithology/fluid to seismic observations is established. The inversion is done in a Bayesian framework with an approximate posterior distribution. Block Gibbs samplers are used to estimate the approximate posterior distribution. Two different inversion algorithms are established, one with the support of well observations and one without. Both inversion algorithms are tested on a synthetic reservoir and the algorithm with well observations is also tested on a data set from the North Sea. The classification results with both algorithms are good. Without the support of well observations it is problematic to estimate the level of the porosity trends, however the classification results are approximately translation invariant with respect to porosity trends.
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Spikes, Kyle Thomas. "Probabilistic seismic inversion based on rock-physics models for reservoir characterization /." May be available electronically:, 2008. http://proquest.umi.com/login?COPT=REJTPTU1MTUmSU5UPTAmVkVSPTI=&clientId=12498.
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Werthmüller, Dieter. "Bayesian estimation of resistivities from seismic velocities." Thesis, University of Edinburgh, 2014. http://hdl.handle.net/1842/8932.
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I address the problem of finding a background model for the estimation of resistivities in the earth from controlled-source electromagnetic (CSEM) data by using seismic data and well logs as constraints. Estimation of resistivities is normally done by trial-and-error, in a process called “inversion”, by finding a model of the earth whose responses match the data to within an acceptable error; what comes out of the inversion is what is put into the model by the geophysicist: it does not come out of the data directly. The premise underlying this thesis is that an earth model can be found that satisfies not only the CSEM data but also the seismic data and any well logs. I present a methodology to determine background resistivities from seismic velocities using rock physics, structural constraints, and depth trends. The physical parameters of the seismic wave equation are different from those in the electromagnetic diffusion equation, so there is no direct link between the governing equations. I therefore use a Bayesian framework to incorporate not only the errors in the data and our limited knowledge of the rock parameters, but also the uncertainty of our chosen and calibrated velocity-to-resistivity transform. To test the methodology I use a well log from the North Sea Harding South oil and gas field to calibrate the transform, and apply it to seismic velocities of the nearby Harding Central oil and gas field. I also use short-offset CSEM inversions to estimate the electric anisotropy and to improve the shallow part of the resistivity model, where there is no well control. Three-dimensional modelling of this resistivity model predicts the acquired CSEM data within the estimated uncertainty. This methodology makes it possible to estimate background resistivities from seismic velocities, well logs, and other available geophysical and geological data. Subsequent CSEM surveys can then focus on finding resistive anomalies relative to this background model; these are, potentially, hydrocarbon-bearing formations.
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Todorov, Todor I. "Integration of 3C-3D seismic data and well logs for rock property estimation." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape4/PQDD_0015/MQ55246.pdf.
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Varela, Gutierrez Isabel. "Fracture studies from amplitude versus offset and azimuth and vertical seismic profile data." Thesis, University of Edinburgh, 2009. http://hdl.handle.net/1842/4080.
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In this thesis I address the problem of determining fracture properties of subsurface rocks from geophysical surface seismic and vertical seismic profile (VSP) data. In the first part of this thesis I perform multi-attribute analysis, including frequency content, amplitude, travel time and angle of rotation studies on field VSP data from two different carbonate fields, both containing time-lapse surveys. I compare the findings to independent data available in the region and find that the interpreted fracture orientations from the attribute analyses correlate with independent fracture studies in the area, the principal axis of major faults, or the maximum horizontal stress of the area studied. Although I show the existence of these correlations, due to the limited knowledge of the rock properties, these correlations are only qualitative. A more robust inversion of fracture properties requires more knowledge of the physical properties of the medium and forward modelling of the seismic response. A rock physics theory would be required to model the elastic response of the fractured rock; hence a more quantitative fracture characterisation is necessary. In the second part of this thesis I address this need by developing and testing a method for fracture density inversion. Linearised approximations are commonly used in azimuthal amplitude versus offset (AVO) analysis. However, these approximations perform poorly at large angles of incidence where the effect of fractures is more significant. The method proposed here uses a model based approach that does not use these approximations but calculates the exact azimuthal AVO response based on prior knowledge of the elastic constants of the medium, assumed to be known, and a range of fracture densities. A rock physics theory is used for modelling the elastic constants of the fractured rock. I then create a linearized relationship for a specific model that separates the effect due to fracture density from the modelled AVOZ responses. This separation is key to the method, as it provides both a new set of orthogonal basis functions that can be used to express the AVOZ response of field data, and a set of coefficients that are related to fracture density. In general, the inversion is based on these coefficients. The coefficient or coefficients which present the highest correlation with fracture density must be determined on a case by case basis, as they will vary depending on the contrast between the elastic constants across the boundary of interest. I develop and test the method on synthetic surface seismic data and then apply it to seismic data acquired from a laboratory-scale physical geological model. Due to the prior knowledge of the rock properties and structure of the physical geological model, I am able to corroborate that the inverted fracture density from the seismic data matches that of the physical model within the error. I compare the inversion for two different levels of uncertainty in the velocities and densities of the modelled reflection coefficients and show that the inversion results are more precise and accurate when there is less uncertainty in the rock properties of the modelled reflection coefficients. In both the synthetic and physical geological model studies I find that the inversion is optimal for a certain range of offsets/angles of incidence. This means that the optimal range for inversion must be found on a case by case basis, as it depends on the behaviour of the data. Finally, as the inversion relies on the input modelled azimuthal AVO curves, a careful choice of the input rock properties is essential for the inversion process. The inverted fracture density values will only be valid if the rock properties of the field data fall within the range of the modelled ones. This is a limitation of the method, as adequate knowledge of the rock properties is not always available.
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Mikkelsen, Espen Rødland. "Monitoring of CO2 Sequestration at the Longyearbyen CO2 Lab by Time-lapse Seismic : An Interdisciplinary Rock Physics Study." Thesis, Norwegian University of Science and Technology, Department of Electronics and Telecommunications, 2009. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-9931.
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Yuh, Sung H. "Time-lapse seismic monitoring of subsurface fluid flow." [College Station, Tex. : Texas A&M University, 2004. http://hdl.handle.net/1969.1/430.
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Ohta, Yusuke. "Development of Resource Evaluation Technology by Integration of Geophysical Exploration Data and Rock Physics." Doctoral thesis, Kyoto University, 2021. http://hdl.handle.net/2433/263636.
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Rechlin, Aissa Jemela [Verfasser]. "Rock-mass classification in tunneling based on seismic velocities and tunnel-driving data using support vector machines / Aissa Jemela Rechlin." Berlin : Freie Universität Berlin, 2013. http://d-nb.info/1033672211/34.
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Queisser, Manuel Peter. "Quantitative monitoring of CO2 injection at Sleipner using seismic full waveform inversion in the time lapse mode and rock physics modeling." Paris, Institut de physique du globe, 2012. http://www.theses.fr/2012GLOB0001.
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Carbon capture and sequestration is a technology to achieve a considerable deceleration of CO2 emission promptly. Since 1996 one of the largest CO2 storage projects is taking place at Sleipner in the Norwegian North Sea. In order to monitor injected CO2, time lapse surface seismic monitoring surveys have been carried out. Estimating subsurface parameters from the Sleipner seismic data is a challenging problem due to the specific geology of the storage reservoir, which is further complicated by injected CO2. Most seismic imaging methods enable only qualitative insights into the subsurface. Full waveform inversion is well known in the seismic community but not well established yet. Presented results are mostly of demonstrative character. Applying full waveform inversion as an actual tool to a complex problem such as Sleipner is novel. Motivated by the need for a quantitative seismic monitoring of the injected CO2, I have applied 2D seismic full waveform inversion to seismic data sets from Sleipner from 1994 (baseline), 1999 and 2006 along three seismic lines to infer subsurface parameters and parameter changes in the storage reservoir. The P-wave velocity is the major parameter, as it is the most sensitive to CO2 injection. An energy preconditioning of the gradient has been implemented. The usual source wavelet calibration did not prove to be reliable. An alternative source calibration has been successfully applied. By comparing seismic images with inversion results, I found that using seismic images to locate CO2 accumulations in the subsurface may be misleading. The quantitative imaging approach using full waveform inversion resulted in a consistent evolution of the model parameter with time. Major reductions in Pwave velocity and hence the CO2 accumulations could be quantitatively imaged down to a resolution of 10 m. Observed travel time shifts due to CO2 injection are comparable to those derived from the inversion result. In order to estimate CO2 saturations, rock physical concepts have been combined and extended to arrive at a rock physical formulation of the subsurface at Sleipner. I used pseudo Monte Carlo rock physics modeling to assess the influence of lithologic heterogeneity on the CO2 saturations as well as to generate pseudo well logs to estimate confidence intervals of the inverted parameters. The rock physics modeling has been used to relate inverted parameters to CO2 saturations. The injected CO2 is buoyant. The highest CO2 saturations are in the upper half of the storage reservoir but not necessarily at the top. Non-uniqueness of the saturation maps associated with the density scenario has been assessed. As a result, the distribution of the maximum saturation values remains the same. The quantity of dissolved CO2 in the reservoir water is a key parameter from both a security and optimization point of view. A quantitative estimation of dissolved CO2 by seismic means has not been undertaken yet to our knowledge. Based on the seismic inversion result of a seismic line, I found that along the line at least 20% of the injected CO2 mass was dissolved in 2006, after 10 years of injection. Such a high value indicates enhanced solubility trapping, which is very advantageous for storage safety at Sleipner. The results of this work represent a further step towards ultimate goals of quantitative monitoring, such as the estimation of the injected CO2 in-situ volume.
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Tönsing, Tobias R. "Using rock physics to determine uncertainties in pore-fluid and lithology-estimates from seismic attributes in the Bredasdorp Basin, offshore South Africa." Master's thesis, University of Cape Town, 2006. http://hdl.handle.net/11427/4227.
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This study is aimed at developing a workflow for quantitative seismic interpretation. The workflow generated probability maps of various facies and pore-fluid by combining seismic attributes and wireline log data through rock physics relationships and supervised statistical classification. The workflow was developed mainly for hydrocarbon exploration, but could be used for other purposes, provided the target is seismically detectible. Any prior regional geological knowledge is built into the workflow, by extending the training date appropriately. The workflow aims to maximize the extraction of quantitative geological parameters from data that are most commonly acquired for hydrocarbon exploration, namely seismic and wireline log data. The workflow is presented using 3D seismic data from the Bredasdorp Basin offshore South Africa's south-coast. Wireline log data from the E-BX1 borehole are also used in the study, as well as regional geological interpretations. The study focused on the siliciclastic Aptian "13B" sequence, which was encountered at a depth of 2500 m below sea level at borehole E-BX1. Two massive 13B sandstone units were encountered at E-BX1. The lower unit is 50 m, and the upper 20 m thick. Both are water wet. The results of this study suggest that there are two oil accumulations at the 13X level around E-BX1. This is indicated by the high probability predicted for oil-bearing sandstone in these two areas.
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Brajanovski, Miroslav. "Effects of fractures on seismic waves in poroelastic formations." Curtin University of Technology, Department of Exploration Geophysics, 2004. http://espace.library.curtin.edu.au:80/R/?func=dbin-jump-full&object_id=15309.
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Naturally fractured reservoirs have attracted an increased interest of exploration and production geophysics in recent years. In many instances, natural fractures control the permeability of the reservoir, and hence the ability to find and characterize fractured areas of the reservoir represents a major challenge for seismic investigations. In fractured and porous reservoirs the fluid affects elastic anisotropy of the rock and also causes significant frequency dependent attenuation and dispersion. In this study we develop a mathematical model for seismic wave attenuation and dispersion in a porous medium in a porous medium with aligned fractured, caused by wave induced fluid flow between pores and fractures. In this work fractures in the porous rock are modelled as very thin and highly porous layers in a porous background. Dry highly porous materials have low elastic moduli; thus dry skeleton of our system contains thin and soft layers, and is described by linear slip theory. The fluid saturated rock with high-porasity layers is described by equations of poroelasticity with periodically varying coefficients. These equations are analyzed using propagator matrix approach commonly used to study effective properties of layered system. This yields a dispersion equation for a periodically layered saturated porous medium taking into account fluid communication between pore spaces of the layers. Taking in this dispersion equation a limit of small thickness for high-porosity layers gives the velocity and attenuation as a function of frequency and fracture parameters. The results of this analysis show that porous saturated rock with aligned fractures exhibits significant attenuation and velocity dispersion due to wave induced fluid flow between pores and fractures.At low frequencies the material properties are equal to those obtained by anisotropic Gassmann theory applied to a porous material with linear-slip, interfaces. At high frequencies the results are equivalent to those for fractures with vanishingly small normal slip in a solid (non-porous) background. The characteristic frequency of the attenuation and dispersion depends on the background permeability, fluid viscosity, as well as fracture density and spacing. The wave induced fluid flow between pores and fractures considered in this work has exactly the same physical nature as so-called squirt flow, which is widely believed to by a major cause of seismic attenuation. Hence, the present model can be viewed as a new model of squirt-flow attenuation, consistent with Biot’s theory of poroelasticity. The theoretical results of this work are also limited by the assumption of periodic distribution of fractures. In reality fractures may be distributed in a random fashion. Sensitivity of our results to the violation of the periodicity assumption was examined numerically using reflectivity modelling for layered poroelastic media. Numerical experiments for a random distribution of fractures of the same thickness still show surprisingly good agreement with theoretical results obtained for periodic fractures. However this agreement may break down if fracture properties are allowed to vary from fracture to fracture. The results of this thesis show how to compute frequency dependences of attenuation and velocity caused by wave induced fluid flow between pores and fractures. These results can be used to obtain important parameters of fractured reservoirs, such as permeability and fracture weakness, from attenuation measurements. The major requirement for the success of such an approach is that measurements must be made in over a relatively broad frequency range.
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Heider, Sven [Verfasser], and T. [Akademischer Betreuer] Bohlen. "2D Elastic Full-Waveform Tomography of Vibro-Seismic Data in Crystalline Host Rock at the GFZ-Underground-Lab, Freiberg / Sven Heider. Betreuer: T. Bohlen." Karlsruhe : KIT-Bibliothek, 2014. http://d-nb.info/1056955902/34.
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Dye, Brian Christopher. "Identifying Strombolian Eruptions through Cross-Correlation of Seismic Data and Machine Learning of Infrared, Lava-Lake Images on Mount Erebus, Antarctica." Thesis, University of Louisiana at Lafayette, 2019. http://pqdtopen.proquest.com/#viewpdf?dispub=10815582.
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Mount Erebus, Antarctica, is a volcano with frequent lava-lake eruptions known as strombolian eruptions. The larger of these eruptions create strong seismic waves and have a characteristic seismic signature that can be analyzed through three-component cross-correlation to distinguish smaller strombolian eruptions from the background noise of the volcano. The addition of an infrared camera on the rim of Mount Erebus allows for the confirmation of strombolian eruptions as opposed to unrelated seismic activity. This research finds that eruption events can also be detected categorizing the images using machine learning. Machine learning in seismology is now a commonly used technique, yet to date, no research using machine learning has ever been used in volcanology. Image categorization along with cross-correlation can improve automatic detection of strombolian eruptions.
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Gautre, Christy. "Time-Lapse Depletion Modeling Sensitivity Study: Gas-Filled Gulf of Mexico Reservoir." ScholarWorks@UNO, 2010. http://scholarworks.uno.edu/td/1187.
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Time-lapse seismic allows oil/gas reservoir monitoring during production, highlighting compaction and water movement. Time-lapse modeling, using a stress-dependent rock physics model, helps determine the need and frequency of expensive repeat seismic acquisition. We simulate a Gulf of Mexico gas reservoir time-lapse response for depletion and water flooding using uncertainty ranges in water saturation, porosity, stress-induced velocity changes, and pore compressibility. An analysis is conducted to see if a water-swept region could have been predicted. Findings show the swept and un-swept monitor cases amplitude differences range from 6% to 15%, which is higher than the actual monitor seismic noise level. Thus, it is unlikely these cases could be differentiated. However, the modeled amplitude changes from base to monitor cases do not match measured amplitude changes. This suggests the rock property model requires pressure-variance improvement and/or the changes in seismic amplitudes are associated with pressure/porosity, thickness, or saturation cases not modeled.
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Barbouteau, Sandra. "Suivi de substitution de fluides dans les roches par corrélation de bruit : Expériences ultrasonores au laboratoire et surveillance continue en cours d’exploitation du sous-sol." Thesis, Grenoble, 2014. http://www.theses.fr/2014GRENU045/document.
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L'interférométrie sismique, tout comme l'interférométrie optique, étudie les phénomènes d'interférence entre des couples de signaux sismiques afin de mettre en évidence des différences entre ces signaux (par exemple Curtis et al. 2006). Les traitements utilisés consistent le plus souvent à corréler les enregistrements entre différents capteurs pour remonter aux fonctions de Green, (ou réponse impulsionnelle) entre ces récepteurs (par exemple, Derode et al. (2003), Wapenaar et al. (2004), Larose et al. (2006), Sanchez-Sesma et Campillo (2006)). Ce principe a déjà été appliqué avec succès dans les domaines de la sismologie (Campillo et Paul (2003)), des ultrasons (Weaver et Lobkis (2001)), de l'exploration sismique (Schuster (2001) et Wapenaar et al. (2004)), et même de l'hélio-sismologie (Duvall et al. (1993)) Dans tous ces cas, l'analyse des corrélations a conduit à une description détaillée des milieux de propagation, en l'occurrence l'intérieur de la Terre dans le cas de la sismologie. La sismique passive, par opposition à la sismique active utilisant les sources cohérentes artificielles (explosifs, canons à air, vibrateurs...), exploite les sources cohérentes naturelles (séismes...). Depuis peu la sismique passive exploite également des champs d'ondes aléatoires engendrées à des temps inconnus par une multitude de sources inconnues dans le sous-sol qui sont enregistrées à différentes positions de récepteurs. L'analyse par interférométrie sismique des enregistrements à deux capteurs permet de remonter aux fonctions de Green, ou réponse impulsionnelle, entre ces deux récepteurs (Derode et al. (2003)). Cette thèse, à vocations à la fois expérimentale et applicative, a deux buts : - vérifier au laboratoire, sur des expériences ultrasonores et avec différents types de roches, l'efficacité du monitoring de substitution de fluides par l'analyse interférométrique ultrasonore - appliquer sur le terrain les méthodes d'interférométrie sismique passive à des expériences ponctuelles de surveillance sismique passive d'exploitation du sous-sol. Ce manuscrit présente, après une synthèse bibliographique, la mise au point d'une nouvelle méthode de mesure des constantes élastiques d'un échantillon de roche (sèche ou saturée de fluide) basée sur les principes de l'interférométrie ultrasonore et de la spectroscopie par résonance ultrasonore. La méthode a été testée et validée (reproductibilité, fidélité, fiabilité…) sur un matériau standard de propriétés connues (aluminium). On expose que les effets de substitution fluide sont tout-à-fait mesurables avec la méthode sur divers échantillons de roches sèches puis saturées (en eau ou en éthylène glycol) et les résultats sont en accord raisonnable avec la théorie poroélastique de Biot-Gassmann. En outre, un certain nombre de faiblesses de la méthode ont été mises en évidence, à savoir la limitation à des roches assez homogènes et peu atténuantes. La dernière partie de ce manuscrit met en évidence des variations de vitesse des ondes dans un champ d'hydrocarbures (informations relatives à ce champ confidentielles) concomitantes avec le début de l'injection de vapeur dans celui-ci (pour récupération assistée de l'huile)Seismic interferometry, like optic interferometry, studies the interferences phenomena between couples of seismic signals, with the aim of pointing at differences between those signals (Curtis et al. 2006 for instance). The data processing consists, generally, in correlating the recordings between different stations to retrieve the Green's function between these sensors (Derode et al. (2003), Wapenaar et al. (2004), Larose et al. (2006), Sanchez-Sesma et Campillo (2006)). This principle has already been successfully applied in the field of seismology (Campillo and Paul (2003)), ultrasound (Weaver et Lobkis (2001)), seismic exploration and even helioseismology (Duvall et al. (1993)). In all these cases, the analysis of the correlations leads to a detailed description of the propagation medium. Contrary to active seismic which uses artificial coherent sources (explosives, air guns…), passive seismic exploits natural coherent sources (seisms…). Since a few years, passive seismics also exploits random wave fields generated at unknown times by many unknown sources in the ground, and recorded at different stations positions. The analysis with cross-correlation of pairs of recordings, from pairs of sensors, leads to the Green's function between the two sensors (Derode et al. (2003)). This thesis has two objectives: -to check, at the lab scale, the effectiveness of monitoring of fluids substitution with noise correlation (ultrasound scale) in rocks -to apply noise correlation methods to passive seismic monitoring of a hydrocarbons field. This thesis presents, after a state of the art, the set-up of a new method to measure elastic constants of a rock sample (dry or fluid-saturated), based on ultrasound interferometry principle and resonant ultrasound spectroscopy. The method has been tested and validated (reproducibility, accuracy, precision…) on a standard material (aluminium). We show that the effects of a fluids substitution are measurable on various rock samples (dry or saturated, with water or with ethylene glycol) with this method. Plus the results are in agreement with Biot-Gassmann's theory. Besides, several weaknesses of the method were pointed, that is to say the method does not work on heterogeneous or attenuating medium. The last part of this thesis exposes speed of waves variations in a hydrocarbons field, when steam is injected simultaneously inside the reservoir (enhanced oil recovery operation)
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Banda, Sraj Umar. "Caving mechanisms for a non-daylighting orebody." Doctoral thesis, Luleå tekniska universitet, Geoteknologi, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-63994.
Full textAbstract:
The sublevel caving mining method is a mass production method with potentially very low operational costs. The success of this method is dependent on, among other factors, the cavability of the orebody and the overlying rock mass. However, caving of the surrounding rock mass also results in deformations in the cap rock as well as on the ground surface above the orebody being mined. From this follows that any existing infrastructure on the ground surface must be relocated as not to be affected by the mining-induced deformations.This thesis work was undertaken to bring about a better understanding of the rock mass behavior in the cap rock of non-daylighting orebodies, with particular application to the Printzsköld orebody as part of the LKAB Malmberget Mine. Rock testing, field observations and underground mapping was conducted to characterize the rock mass in the caving environment. A methodology for identifying the caving front based on seismic monitoring data was derived by studying the Fabian orebody (which has caved to surface), and using laser scanning data for validation. The methodology was then applied to the Printzsköld orebody to identify the caving front.Numerical modeling was performed for various scenarios of the rock mass as mining proceeded. Modeling included (i) stress analysis to understand stress changes and their effects on the rock mass behavior, (ii) discontinuum numerical modeling to quantify the influence of large-scale geological structures on the cave progression, and (iii) discontinuum cave modeling to simulate possible cave mechanisms in the cap rock more explicitly. Laser scanning together with seismic event data were used to calibrate the numerical models.The numerical simulation results showed that as mining progresses, the cap rock and hangingwall were exposed to stress changes that resulted in yielding. Two failure mechanisms were predominantly at play (i) shear failure (dominant in the cap rock) and (ii) tensile failure (dominant in the hangingwall). The presence of the large-scale structures affected thenearfield stresses through slip along the cave boundaries. The effect of the structures on the far field stresses were less significant.Discontinuum modeling to explicitly simulate failure and caving involved simulating the rock mass as a jointed medium using Voronoi tessellations in 2D, and bonded block modeling (BBM) in 3D. Both the 2D and the 3D modeling results showed fair agreement when comparing the inferred boundary of the seismogenic zone, with that identified from seismic monitoring data. Predictive numerical modeling was conducted for future planned mining to assess future cave development in the cap rock. The results from 3D modeling indicated that cave breakthrough for the Printzsköld orebody is expected when mining the 1023 m level, corresponding to approximately year 2022, as per current mining plans. The 2D model was non-conservative with cave breakthrough predicted to occur when mining the 1109 m level, corresponding to the year 2028.The estimated boundary between the seismogenic and yielded zones, as defined in the Duplancic and Brady conceptual model of caving, was coinciding with, or was close to, the cave boundary in the Printzsköld orebody. This may imply that in some areas the yielded zone was not present and that the Duplancic and Brady model may not be universally applicable. Additional work is required to verify this indication, as well as to fine-tune the modeling methodology.
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Dou, Qifeng. "Rock Physics-Based Carbonate Reservoir Pore Type Evaluation by Combining Geological, Petrophysical and Seismic Data." Thesis, 2011. http://hdl.handle.net/1969.1/ETD-TAMU-2011-05-9502.
Full textAbstract:
Pore type variations account for complex velocity-porosity relationship and intensive permeability heterogeneity and consequently low oil and gas recovery in carbonate reservoir. However, it is a challenge for geologist and geophysicist to quantitatively estimate the influences of pore type complexity on velocity variation at a given porosity and porosity-permeability relationship. A new rock physics-based integrated approach in this study was proposed to quantitatively characterize the diversity of pore types and its influences on wave propagation in carbonate reservoir. Based on above knowledge, permeability prediction accuracy from petrophysical data can be improved compared to conventional approach. Two carbonate reservoirs with different reservoir features, one is a shallow carbonate reservoir with average high porosity (>10%) and another one is a supper-deep carbonate reservoir with average low porosity (<5%), are used to test the proposed approach.
Paleokarst is a major event to complicate carbonate reservoir pore structure. Because of limited data and lack of appropriate study methods, it is a difficulty to characterize subsurface paleokarst 3D distribution and estimate its influences on reservoir heterogeneity. A method by integrated seismic characterization is applied to delineate a complex subsurface paleokarst system in the Upper San Andres Formation, Permian basin, West Texas. Meanwhile, the complex paleokarst system is explained by using a carbonate platform hydrological model, similar to modern marine hydrological environments within carbonate islands.
How to evaluate carbonate reservoir permeability heterogeneity from 3D seismic data has been a dream for reservoir geoscientists, which is a key factor to optimize reservoir development strategy and enhance reservoir recovery. A two-step seismic inversions approach by integrating angle-stack seismic data and rock physics model is proposed to characterize pore-types complexity and further to identify the relative high permeability gas-bearing zones in low porosity reservoir (< 5%) using ChangXing super-deep carbonate reservoir as an example. Compared to the conventional permeability calculation method by best-fit function between porosity and permeability, the results in this study demonstrate that gas zones and non-gas zones in low porosity reservoir can be differentiated by using above integrated permeability characterization method.
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Kim, Ji Soo. "Processing and imaging of reflection seismic data from crystalline rock terranes." 1993. http://hdl.handle.net/1993/29431.
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Jiang, Meijuan. "Seismic reservoir characterization of the Haynesville Shale : rock-physics modeling, prestack seismic inversion and grid searching." Thesis, 2014. http://hdl.handle.net/2152/24987.
Full textAbstract:
This dissertation focuses on interpreting the spatial variations of seismic amplitude data as a function of rock properties for the Haynesville Shale. To achieve this goal, I investigate the relationships between the rock properties and elastic properties, and calibrate rock-physics models by constraining both P- and S-wave velocities from well log data. I build a workflow to estimate the rock properties along with uncertainties from the P- and S-wave information. I correlate the estimated rock properties with the seismic amplitude data quantitatively. The rock properties, such as porosity, pore shape and composition, provide very useful information in determining locations with relatively high porosities and large fractions of brittle components favorable for hydraulic fracturing. Here the brittle components will have the fractures remain opened for longer time than the other components. Porosity helps to determine gas capacity and the estimated ultimate recovery (EUR); composition contributes to understand the brittle/ductile strength of shales, and pore shape provides additional information to determine the brittle/ductile strength of the shale. I use effective medium models to constrain P- and S-wave information. The rock-physics model includes an isotropic and an anisotropic effective medium model. The isotropic effective medium model provides a porous rock matrix with multiple mineral phases and pores with different aspect ratios. The anisotropic effective medium model provides frequency- and pore-pressure-dependent anisotropy. I estimate the rock properties with uncertainties using grid searching, conditioned by the calibrated rock-physics models. At well locations, I use the sonic log as input in the rock-physics models. At areas away from the well locations, I use the prestack seismic inverted P- and S-impedances as input in the rock-physics models. The estimated rock properties are correlated with the seismic amplitude data and help to interpret the spatial variations observed from seismic data. I check the accuracy of the estimated rock properties by comparing the elastic properties from seismic inversion and the ones derived from estimated rock properties. Furthermore, I link the estimated rock properties to the microstructure images and interpret the modeling results using observations from microstructure images. The characterization contributes to understand what causes the seismic amplitude variations for the Haynesville Shale. The same seismic reservoir characterization procedure could be applied to other unconventional gas shales.text
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Carter, Russell Wirkus. "Fluid Characterization at the Cranfield CO₂ Injection Site : Quantitative Seismic Interpretation from Rock-Physics Modeling and Seismic Inversion." Thesis, 2014. http://hdl.handle.net/2152/28099.
Full textAbstract:
This dissertation focuses on quantitatively interpreting the elastic properties of the Cranfield reservoir for CO₂ saturation. In this work, quantitative interpretation starts by examining the relationship between CO₂ saturation and the elastic properties of the reservoir. This relationship comes from a rock-physics model calibrated to measured well data. Seismic data can then be inverted using a model for CO₂ saturation and rock-property estimates. The location and saturation of injected CO₂ are important metrics for monitoring the long-term effectiveness of carbon capture utilization and storage. Non-uniform CO₂ saturation is a contributing factor to both lateral and time-lapse changes in the elastic properties of the Cranfield reservoir. In the Cranfield reservoir, CO₂ saturation and porosity can be estimated from the ratio of P-wave velocity (Vp) to S-wave velocity (Vs) and P-impedance (Ip), respectively. Lower values of Ip for a given rock matrix often correlate to higher porosity. Similarly, for a given area of the reservoir, lower Vp/Vs frequently can be associated with higher CO₂ saturation. If a constant porosity from the baseline to the time-lapse survey is assumed, changes in Ip over time can be attributed to changes in CO₂ saturation in lieu of using Vp/Vs. Decreases in Ip between the baseline and time-lapse survey can be attributed to increases in CO₂ saturation. With a rock-physics model calibrated to the reservoir, Ip and Is from a vertical seismic profile were correlated to statistical ranges of porosity and CO₂ saturations. To expand the lateral interpretation of reservoir porosity and CO₂ saturation, the time-variant changes in Ip between baseline and time-lapse surface seismic datasets were compared to changes in CO₂ saturation calculated from the rock-physics model. Characterizing the CO₂ saturation of the Tuscaloosa sandstones helped to establish a workflow for estimating reservoir properties and fluid saturation from multiple types of geophysical data. Additionally, this work helped establish an understanding for how CO₂ injected into a reservoir alters and changes the elastic properties of the reservoir and the degree to which those changes can be detected using geophysical methods.text
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Mammadova, Elnara. "Influence of Rock Types on Seismic Monitoring of CO2 Sequestration in Carbonate Reservoirs." Thesis, 2011. http://hdl.handle.net/1969.1/ETD-TAMU-2011-08-10019.
Full textAbstract:
Although carbonates hold more than 60 percent of the world's oil reserves, they, nevertheless, exhibit much lower average recovery factor values than terrigenous
sandstone reservoirs. Thus, utilization of advanced enhanced oil recovery (EOR) techniques such as high pressure CO2 injection may normally be required to recover oil in place in carbonate reservoirs. This study addresses how different rock types can influence the seismic monitoring of CO2 sequestration in carbonates.
This research utilizes an elastic parameter, defined in a rock physics model of poroelasticity and so-called as the frame flexibility factor, to successfully quantify the carbonate pore types in core samples available from the Great Bahama Bank (GBB). This study shows that for carbonate samples of a given porosity the lower the frame flexibility factors the higher is the sonic wave velocity. Generally, samples with frame flexibility values of <4 are either rocks with visible moldic pores or intraframe porosity; whereas, samples with frame flexibility values of >4 are rocks with intercrystalline and microporosity. Hence, different carbonate pore geometries can be quantitatively predicted using the elastic parameters capable of characterizing the porous media with a representation of their internal structure on the basis of the flexibility of the frame and pore connectivity.
In this research, different fluid substitution scenarios of liquid and gaseous CO2 saturations are demonstrated to characterize the variations in velocity for carbonate-specific pore types. The results suggest that the elastic response of CO2 flooded rocks is mostly governed by pore pressure conditions and carbonate rock types. Ultrasonic P-wave velocities in the liquid-phase CO2 flooded samples show a marked decrease in the order of 0.6 to 16 percent. On the contrary, samples flooded with gaseous-phase CO2 constitute an increase in P-wave velocities for moldic and intraframe porosities, while establishing a significant decrease for samples with intercrystalline and micro-porosities. Such velocity variations are explained by the stronger effect of density versus
compressibility, accounting for the profound effect of pore geometries on the acoustic properties in carbonates.
The theoretical results from this research could be a useful guide for interpreting the response of time-lapse seismic monitoring of carbonate formations following CO2
injection at depth. In particular, an effective rock-physics model can aid in better discrimination of the profound effects of different pore geometries on seismic monitoring of CO2 sequestration in carbonates.
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Coyle, Sarah Bryson. "Reservoir characterization of the Haynesville Shale, Panola County, Texas using rock physics modeling and partial stack seismic inversion." Thesis, 2014. http://hdl.handle.net/2152/26918.
Full textAbstract:
This thesis investigates the relationship between elastic properties and rock properties of the Haynesville Shale using rock physics modeling, simultaneous seismic inversion, and grid searching. A workflow is developed in which a rock physics model is built and calibrated to well data in the Haynesville Shale and then applied to 3D seismic inversion data to predict porosity and mineralogy away from the borehole locations. The rock physics model describes the relationship between porosity, mineral composition, pore shape, and elastic stiffness using the anisotropic differential effective medium model. The calibrated rock physics model is used to generate a modeling space representing a range of mineral compositions and porosities with a calibrated mean pore shape. The model space is grid searched using objective functions to select a range of models that describe the inverted P-impedance, S-impedance, and density volumes. The selected models provide a range of possible rock properties (porosity and mineral composition) and an estimate of uncertainty. The mineral properties were mapped in three dimensions within the area of interest using this modeling technique and inversion workflow. This map of mineral content and porosity can be interpreted to predict the best areas for hydraulic fracturing.text
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Meillieux, Damien Yves Justin. "Wellbore seismic and core sample measurement analysis integrated geophysical study of the Lake Bosumtwi impact structure /." Master's thesis, 2009. http://hdl.handle.net/10048/427.
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Thesis (M. Sc.)--University of Alberta, 2009.Title from pdf file main screen (viewed on July 16, 2009). "A thesis submitted to the Faculty of Graduate Studies and Research in partial fulfillment of the requirements for the degree of Master of Science in Geophysics, Department of Physics, University of Alberta." Includes bibliographical references.
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Pecher, Ingo A., Reem Freij-Ayoub, Jinhai Yang, Ross Anderson, Bahman Tohidi, Colin MacBeth, and Ben Clennell. "SEISMIC TIME-LAPSE MONITORING OF POTENTIAL GAS HYDRATE DISSOCIATION AROUND BOREHOLES - COULD IT BE FEASIBLE? A CONCEPTUAL 2D STUDY LINKING GEOMECHANICAL AND SEISMIC FD MODELS." 2008. http://hdl.handle.net/2429/1552.
Full textAbstract:
Monitoring of the seafloor for gas hydrate dissociation around boreholes during hydrocarbon production is likely to involve seismic methods because of the strong sensitivity of P-wave velocity to gas in sediment pores. Here, based on geomechanical models, we apply commonly used rock physics modeling to predict the seismic response to gas hydrate dissociation with a focus on P-impedance and performed sensitivity tests. For a given initial gas hydrate saturation, the mode of gas hydrate distribution (cementation, frame-bearing, or pore-filling) has the strongest effect on P-impedance, followed by the mesoscopic distribution of gas bubbles (evenly distributed in pores or “patchy”), gas saturation, and pore pressure. Of these, the distribution of gas is likely to be most challenging to predict. Conceptual 2-D FD wave-propagation modeling shows that it could be possible to detect gas hydrate dissociation after a few days.
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Davidson, Daniel. "A Rock Physics Based Investigation of Pore Structure Variations Associated with a CO2 Flood in a Clastic Reservoir, Delhi, LA." Thesis, 2013. http://hdl.handle.net/1969.1/151283.
Full textAbstract:
The permeability in siliclastic rocks can vary due to different pore geometries. The pore properties of a formation can also have significant effects on reflection coefficient. The pore structure of clastic rock may be predicted from a wave reflection using mathematical models. Biot-Gassmann and Sun’s equations are examples of two models which were used in this research to quantify the pore property. The purpose of this thesis is to measure variations in porosity and permeability using 3-D time lapsed seismic during a CO_(2) flood.
CO_(2) sequestration EOR will most likely cause permanent diagenetic effects that will alter pore geometry and permeability. This research shows compelling evidence that the pore structure changes in an active CO_(2) flood at the Delhi Holt-Bryant reservoir can be measured with acoustic data. The pore property change is measured by using the Baechle ratio, the Gassmann model, and the Sun framework flexibility factor. The change in the pore properties of the formation also indicates a increase in the permeability of the reservoir as a result of CO_(2) interaction.
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Bui, Hoa Q. "The Asperity-deformation Model Improvements and Its Applications to Velocity Inversion." 2009. http://hdl.handle.net/1969.1/ETD-TAMU-2009-05-425.
Full textAbstract:
Quantifying the influence of pressure on the effective elastic rock properties
is important for applications in rock physics and reservoir characterization. Here I
investigate the relationship between effective pressure and seismic velocities by performing
inversion on the laboratory-measured data from a suite of clastic, carbonate
and igneous rocks, using different analytic and discrete inversion schemes. I explore
the utility of a physical model that models a natural fracture as supported by asperities
of varying heights, when an effective pressure deforms the tallest asperities,
bringing the shorter ones into contact while increasing the overall fracture stiffness.
Thus, the model is known as the ?asperity-deformation? (ADM) or ?bed-of-nails?
(BNM) model. Existing analytic solutions include one that assumes the host rock is
infinitely more rigid than the fractures, and one that takes the host-rock compliance
into account. Inversion results indicate that although both solutions can fit the data
to within first-order approximation, some systematic misfits exist as a result of using
the rigid-host solution, whereas compliant-host inversion returns smaller and random
misfits, yet out-of-range parameter estimates. These problems indicate the effects of
nonlinear elastic deformation whose degree varies from rock to rock. Consequently,
I extend the model to allow for the pressure dependence of the host rock, thereby
physically interpreting the nonlinear behaviors of deformation. Furthermore, I apply
a discrete grid-search inversion scheme that generalizes the distribution of asperity
heights, thus accurately reproduces velocity profiles, significantly improves the fit and helps to visualize the distribution of asperities. I compare the analytic and numerical
asperity-deformation models with the existing physical model of elliptical ?pennyshape?
cracks with a pore-aspect-ratio (PAR) spectrum in terms of physical meaning
and data-fitting ability. The comparison results provide a link and demonstrate the
consistency between the use of the two physical models, making a better understanding
of the microstructure as well as the contact mechanism and physical behaviors of
rocks under pressure. ADM-based solutions, therefore, have the potential to facilitate
modeling and interpretation of applications such as time-lapse seismic investigations
of fractured reservoirs.
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Ile, Anthony. "Petrophysics and fluid mechanics of selected wells in Bredasdorp Basin South Africa." 2013. http://hdl.handle.net/11394/3573.
Full textAbstract:
Magister Scientiae - MScPressure drop within a field can be attributed to several factors. Pressure drop occurs when fractional forces cause resistance to flowing fluid through a porous medium. In this thesis, the sciences of petrophysics and rock physics were employed to develop understanding of the physical processes that occurs in reservoirs. This study focussed on the physical properties of rock and fluid in order to provide understanding of the system and the mechanism controlling its behaviour. The change in production capacity of wells E-M 1, 2, 3, 4&5 prompted further research to find out why the there will be pressure drop from the suits of wells and which well was contributing to the drop in production pressure. The E-M wells are located in the Bredasdorp Basin and the reservoirs have trapping mechanisms of stratigraphical and structural systems in a moderate to good quality turbidite channel sandstone. The basin is predominantly an elongated north-west and south-east inherited channel from the synrift sub basin and was open to relatively free marine circulation. By the southwest the basin is enclose by southern Outeniqua basin and the Indian oceans. Sedimentation into the Bredasdorp basin thus occurred predominantly down the axis of the basin with main input direction from the west. Five wells were studied E-M1, E-M2, E-M3, E-M4, and E-M5 to identify which well is susceptible to flow within this group. Setting criteria for discriminator the result generated four well as meeting the criteria except for E-M1. The failure of E-M1 reservoir well interval was in consonant with result showed by evaluation from the log, pressure and rock physics analyses for E-M1.iv Various methods in rock physics were used to identify sediments and their conditions and by applying inverse modelling (elastic impedance) the interval properties were better reflected. Also elastic impedance proved to be an economical and quicker method in describing the lithology and depositional environment in the absence of seismic trace.