Journal articles: 'Sedimentary rocks Fluid dynamics'

1

Prezbindowski, Dennis R., and J. Bryan Tapp. "Dynamics of fluid inclusion alteration in sedimentary rocks: a review and discussion." Organic Geochemistry 17, no. 2 (January 1991): 131–42. http://dx.doi.org/10.1016/0146-6380(91)90071-q.

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Zhao, Luanxiao, Yirong Wang, Qiuliang Yao, Jianhua Geng, Hui Li, Hemin Yuan, and De-hua Han. "Extended Gassmann equation with dynamic volumetric strain: Modeling wave dispersion and attenuation of heterogeneous porous rocks." GEOPHYSICS 86, no. 3 (April 27, 2021): MR149—MR164. http://dx.doi.org/10.1190/geo2020-0395.1.

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Sedimentary rocks are often heterogeneous porous media inherently containing complex distributions of heterogeneities (e.g., fluid patches and cracks). Understanding and modeling their frequency-dependent elastic and adsorption behaviors is of great interest for subsurface rock characterization from multiscale geophysical measurements. The physical parameter of dynamic volumetric strain (DVS) associated with wave-induced fluid flow is proposed to understand the common physics and connections behind known poroelastic models for modeling dispersion behaviors of heterogeneous rocks. We have derived the theoretical formulations of DVS for patchy saturated rock at the mesoscopic scale and cracked porous rock at microscopic grain scales, essentially embodying the wave-induced fluid-pressure relaxation process. By incorporating DVS into the classic Gassmann equation, a simple but practical “dynamic equivalent” modeling approach, the extended Gassmann equation, is developed to characterize the dispersion and attenuation of complex heterogeneous rocks at nonzero frequencies. Using the extended Gassmann equation, the effect of microscopic or mesoscopic heterogeneities with complex distributions on the wave dispersion and attenuation signatures can be captured. Our theoretical framework provides a simple and straightforward analytical methodology to calculate wave dispersion and attenuation in porous rocks with multiple sets of heterogeneities exhibiting complex characteristics. We also demonstrate that, with the appropriate consideration of multiple crack sets and complex fluid patches distribution, the modeling results can better interpret the experimental data sets of dispersion and attenuation for heterogeneous porous rocks.

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Digby, P. J., and K. Walton. "Wave Propagation Through Elastically-Anisotropic Fluid-Saturated Porous Rocks." Journal of Applied Mechanics 56, no. 4 (December 1, 1989): 744–50. http://dx.doi.org/10.1115/1.3176167.

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An elastically-anisotropic sedimentary rock is modeled by a simple cubic packing of identical, contacting spherical particles. The connected pore space is filled with an inviscid, compressible fluid. A set of averaged equations is derived to relate the constitutive and dynamic coupling coefficients, and hence also the effective wave speeds in any given direction explicitly to the microstructural properties of the rock considered. Simple, explicit results are obtained when the propagation of either a purely longitudinal or a purely transverse wave is considered.

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Angus, Doug A., James P. Verdon, Quentin J. Fisher, and J. M. Kendall. "Exploring trends in microcrack properties of sedimentary rocks: An audit of dry-core velocity-stress measurements." GEOPHYSICS 74, no. 5 (September 2009): E193—E203. http://dx.doi.org/10.1190/1.3183940.

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Rock-physics models are used increasingly to link fluid and mechanical deformation parameters for dynamic elastic modeling. We explore the input parameters of an analytical stress-dependent rock-physics model. To do this, we invert for the stress-dependent microcrack parameters of more than 150 sedimentary rock velocity-stress core measurements taken from a literature survey. The inversion scheme is based on a microstructural effective-medium formulation defined by a second-rank crack-density tensor (scalar crack model) or by a second- and fourth-rank crack-density tensor (joint inversion model). Then the inversion results are used to explore and predict the stress-dependent elastic behavior of various sedimentary rock lithologies using an analytical microstructural rock-physics model via the initial modelinput parameters: initial crack aspect ratio and initial crack density. Estimates of initial crack aspect ratio are consistent among most lithologies with a mean of 0.0004, but for shales they differ up to several times in magnitude with a mean of 0.001. Estimates of initial aspect ratio are relatively insensitive to the inversion method, although the scalar crack inversion becomes less reliable at low values of normal-to-tangential crack compliance ratio [Formula: see text]. Initial crack density is sensitive to the degree of damage as well as the inversion procedure. An important implication is that the fourth-rank crack-density term is not necessarily negligible for most sedimentary rocks and evaluation of this term or [Formula: see text] is necessary for accurate prediction of initial crack density. This is especially important because recent studies suggest that [Formula: see text] can indicate fluid content in cracks.

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Holford, Simon P., Nick Schofield, and Peter Reynolds. "Subsurface fluid flow focused by buried volcanoes in sedimentary basins: Evidence from 3D seismic data, Bass Basin, offshore southeastern Australia." Interpretation 5, no. 3 (August 31, 2017): SK39—SK50. http://dx.doi.org/10.1190/int-2016-0205.1.

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There is growing evidence that intrusive magmatic bodies such as sills and dikes can influence the migration of fluids in the deep subsurface. This influence is largely due to permeability contrasts with surrounding sedimentary rocks or because of interconnected open fractures within and around intrusions acting as conduits for migrating fluids. The role of buried volcanoes in influencing crossstratal fluid migration in sedimentary basins is less well-established. However, several studies have highlighted spatial linkages between extinct hydrothermal vent complexes and fluid seepage, suggesting that buried extrusive features can also influence subsurface fluid-flow pathways, potentially leading to migration of hydrocarbon fluids between the source and reservoir. We have developed 3D seismic reflection data from the Bass Basin in offshore southeastern Australia that image an early Miocene volcanic complex with exceptional clarity. This volcanic complex is now buried by [Formula: see text] of younger sediments. The largest volcano within this complex is directly overlain by a vertical feature interpreted to be a fluid escape pipe, which extends vertically for approximately 700 m across the late Miocene-Pliocene succession. We suggest that the buried volcanic complex was able to focus vertical fluid migration to the base of the pipe because its bulk permeability was higher than that of the overlying claystone sequence. The fluid escape pipe may have initiated through either (1) hydraulic fracturing following fluid expulsion from a deep, overpressured subvolcanic source region, (2) differential compaction and doming of the overlying claystones, or (3) a combination of these processes. Our results suggest a hitherto unrecognized role for buried volcanoes in influencing dynamic subsurface processes in sedimentary basins. In particular, our study highlights that buried volcanoes may facilitate cross-stratal migration of hydrocarbons from source to reservoir, or through sealing horizons.

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Radkovets, Nataliya, Kostyantyn Hrygorchuk, Yuriy Koltun, Volodymyr Hnidets, Ihor Popp, Marta Moroz, Yuliya Hayevska, et al. "Dynamics of lithogenesis of Phanerozoic sedimentary sequence of the Carpathian-Black Sea region in the aspect of their oil- and gas-bearing potential." Geology and Geochemistry of Combustible Minerals 1-2, no. 183-184 (2021): 60–75. http://dx.doi.org/10.15407/ggcm2021.01-02.060.

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The objective of this work was to study the environments and processes of ancient sedimentation in the epi- and mesopelagic basins of the Carpathian-Black Sea region and to clarify the conditions of oil and gas basins formation within the study region as well as the main aspects of hydrocarbon generation. The burial history of the basins, some aspects of their fluid regime, issues of lithogenetic record, features of transformation of sedimentary basins into the rock-formation basins and the development of the latter during the Phanerozoic are considered. The spatial and temporal peculiarities of the evolution of epi-mesopelogic systems and their influence on the formation of oil- and gas-bearing strata within the Carpathian-Black Sea region have been studied. It has been established that in the sedimentary basins of the Carpathian-Black Sea continental margin of the Tethys Ocean during the long geological history the different intensity structural and morphological changes took place: changes of the subsidence rate of the basin bottom, inversion uplifts, sedimentation pauses, deformation of the sedimentary fill. This was reflected both in the peculiarities of the development of sedimentary environments and in the processes of substance differentiation with the formation of certain post-sedimentary mineral-structural parageneses. It was proved that discrete processes of differentiated compaction and defluidization of sediments cause a number of deformation phenomena, which can be reflected in the features of the morphology of the sedimentary basin bottom, influencing the nature of sediment transportation and accumulation. On the basis of the conducted investigations a number of practical results were obtained which will allow forming new approaches to criteria of hydrocarbons prospecting, in particular the lithophysical aspect which is concentrated on the reservoir properties of rocks; sedimentary reconstructions and the diversity of cyclicity of the studied sediments as a factor of the establishment of prospective areas, reconstruction of the burial history, which provides an information on the state of transformation of organic matter and hydrocarbons, and therefore the range of prospective depths for oil and gas occurrence.

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Claes, Steven, Fadi H. Nader, and Souhail Youssef. "Coupled experimental/numerical workflow for assessing quantitative diagenesis and dynamic porosity/permeability evolution in calcite-cemented sandstone reservoir rocks." Oil & Gas Science and Technology – Revue d’IFP Energies nouvelles 73 (2018): 36. http://dx.doi.org/10.2516/ogst/2018027.

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Some of the world best hydrocarbon reservoirs (carbonates and siliciclastics) are also believed to be valuable for subsurface storage of CO2 and other fluids. Yet, these reservoirs are heterogeneous in terms of their mineralogy and flow properties, at varying spatial-temporal scales. Therefore, predicting the porosity and permeability (flow properties) evolution of carbonates and sandstones remains a tedious task. Diagenesis refers to the alteration of sedimentary rocks through geologic time, mainly due to rock-fluid interactions. It affects primarily the flow properties (porosity and permeability) of already heterogeneous reservoir rocks. In this project a new approach is proposed to calculate/quantify the influence of diagenetic phases (e.g. dissolution, cement plugging) on flow properties of typical sandstone reservoir rocks (Early Jurassic Luxembourg Formation). A series of laboratory experiments are performed in which diagenetic phases (e.g. pore blocking calcite cement in sandstone) are selectively leached from pre-studied samples, with the quantification of the petrophysical characteristics with and without cement to especially infer permeability evolution. Poorly and heavily calcite-cemented sandstone samples, as well as some intermediate cemented samples were used. The results show a distinctive dissolution pattern for different cementation grades and varying Representative Elementary Volumes (REVs). These conclusions have important consequences for upscaling diagenesis effects on reservoirs, and the interpretation of geochemical modelling results of diagenetic processes. The same approach can be applied on other type of cements and host-rocks, and could be improved by integrating other petrophysical analyses (e.g. petroacoustic, NMR).

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Kholodov, V. N. "Thermobaric Depth Settings of Sedimentary Rock Basins and Their Fluid Dynamics: Communication 2. Superhigh Pressures and Mud Volcanoes." Lithology and Mineral Resources 54, no. 1 (January 2019): 38–52. http://dx.doi.org/10.1134/s0024490219010036.

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Kholodov, V. N. "Thermobaric depth settings of sedimentary rock basins and their fluid dynamics: Сommunication 2. Superhigh pressures and mud volcanoes." Литология и полезные ископаемые 1, no. 1 (February 16, 2019): 44–59. http://dx.doi.org/10.31857/s0024-497x2019144-59.

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The article discusses the patterns of placement of mud volcanoes, their spatial connection with tectonic faults, anticlinal uplifts, oil and gas fields. The connection of mud volcanic activity with ultrahigh pressures arising in the clay strata of the stratisphere as a result of phase transformations of clay minerals and organic matter is argued. The role of earthquakes in the formation of fractured clays, increasing their permeability and the formation of mud crates is emphasized. On the example of the mud volcano Aligula (Turkmenistan), the processes of dilution of sandstones and clays, the formation of volcanic mud-crates are considered.

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Kholodov, V. N. "Thermobaric depth settings of sedimentary rock basins and their fluid dynamics: Communication 3. Superhigh pressures in the stratisphere and salt diapirs." Литология и полезные ископаемые, no. 2 (March 28, 2019): 130–48. http://dx.doi.org/10.31857/s0024-497x20192130-148.

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The article discusses the patterns of location and the conditions for the formation of salt diapirs. Their formation is associated with thick salt cjmpleses in which phase transformations within closed physicochemical systems form ultrahigh pressures. The latter are the cause of the flow of salts and their penetration through tectonic cracks and fractures to the earth's surface. The similarity of the formation of salt diapirs and mud volcanoes is emphasized. The possibility of the influence of ultrahigh pressures on the autonomous folding of the sedimentary cover is assumed.

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Kholodov, V. N. "Thermobaric Depth Settings of Sedimentary Rock Basins and Their Fluid Dynamics: Communication 3. Superhigh Pressures in the Stratisphere and Salt Diapirs." Lithology and Mineral Resources 54, no. 2 (March 2019): 103–18. http://dx.doi.org/10.1134/s0024490219020032.

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Kholodov, V. N. "Thermobaric Depth Settings of Sedimentary Rock Basins and Their Fluid Dynamics: Communication 1. Zonation of the Stratispheric Structure and Constraints of Anomalous High and Superhigh Fluid Pressures." Lithology and Mineral Resources 53, no. 6 (November 2018): 489–506. http://dx.doi.org/10.1134/s0024490218060044.

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13

Yildirim, Elif Cihan, Kyungjae Im, and Derek Elsworth. "The influence of fault reactivation on injection-induced dynamic triggering of permeability evolution." Geophysical Journal International 223, no. 3 (September 15, 2020): 1481–96. http://dx.doi.org/10.1093/gji/ggaa382.

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SUMMARY Mechanisms controlling fracture permeability enhancement during injection-induced and natural dynamic stressing remain unresolved. We explore pressure-driven permeability (k) evolution by step-increasing fluid pressure (p) on near-critically stressed laboratory fractures in shale and schist as representative of faults in sedimentary reservoirs/seals and basement rocks. Fluid is pulsed through the fracture with successively incremented pressure to first examine sub-reactivation permeability response that then progresses through fracture reactivation. Transient pore pressure pulses result in a permeability increase that persists even after the return of spiked pore pressure to the null background level. We show that fracture sealing is systematically reversible with the perturbing pressure pulses and pressure-driven permeability enhancement is eminently reproducible even absent shear slip and in the very short term (order of minutes). These characteristics of the observed fracture sealing following a pressure perturbation appear similar to those of the response by rate-and-state frictional healing upon stress/velocity perturbations. Dynamic permeability increase scales with the pore pressure magnitude and fracture sealing controls the following per-pulse permeability increase, both in the absence and presence of reactivation. However, initiation of the injection-induced reactivation results in a significant increase in the rate of permeability enhancement (dk/dp). These results demonstrate the role of frictional healing and sealing of fractures at interplay with other probable processes in pore pressure-driven permeability stimulation, such as particle mobilization.

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Wiemer, Daniel, Steffen G. Hagemann, Nicolas Thébaud, and Carlos Villanes. "Role of Basement Structural Inheritance and Strike-Slip Fault Dynamics in the Formation of the Pataz Gold Vein System, Eastern Andean Cordillera, Northern Peru." Economic Geology 116, no. 7 (November 1, 2021): 1503–35. http://dx.doi.org/10.5382/econgeo.4839.

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Abstract New regional- to vein-scale geologic mapping and structural analysis of the Carboniferous Pataz gold vein system (~10 Moz Au) reveal critical insights into the structural control on gold mineralization along the Eastern Andean Cordillera of northern Peru. The Pataz basement comprises continental volcanic arc and marginal to marine sedimentary rocks, which experienced intensive D2 deformation associated with Late Famatinian northeast to southwest compressive fold-and-thrust belt development. The D2 event produced an E-NE–dipping structural grain, including (1) tilted and F2 folded S1 foliations, (2) local F2 axial planar S2 foliations, and (3) subparallel D2 thrust faults. Intrusions, constituting the ca. 342 to 332 Ma (Mississippian) Pataz batholith, were emplaced along strike of the prominent Río Marañón fault and inherited the D2 basement structures, as evident in the orientation of suprasolidus magmatic flow zones and intrusive contacts within the batholith. Progressive horst-and-graben development affecting the volcanic carapace of the Pataz batholith records late syn- to postmagmatic uplift and transition into a NW-SE–extensional regime. We show that the E-NE–dipping, batholith-hosted gold vein system formed through synchronous activation of two geometric fault-fill vein types, following (1) the moderately E-NE–dipping D2 basement-inherited competency contrasts within the batholith and (2) shallow NE-dipping Andersonian footwall thrusts, during NE-directed shortening (D3a). Both geometric vein types display an early paragenetic stage (I) of quartz-pyrite, progressing texturally from hydraulic breccia into crack-seal laminated shear veins. A second (II), undeformed quartz-pyrite-sphalerite-galena paragenetic stage is observed to fill previously established dilational sites adjacent to newly formed D3b normal faults, which likely formed during regional NW-SE–extensional horst-graben development. Kinematics and relative timing indicate that, upon batholith solidification, D3a transpressional dextral strike-slip ruptures along the Río Marañón fault superimposed a lower-order Riedel-type fault system. Fluid-assisted fault activation preferentially impinged on the D2 basement-inherited competency contrasts within the batholith. Subsequent transition into a transtensional regime led to the D3b normal faulting, providing a feeder system for stage II fluid influx. The tectonic switch may be explained either by increasing tensile strain accommodation upon progressive strike-slip movement within a regional dilational jog or by larger-scale crustal relaxation of the late Gondwana margin upon final Pangea assembly. Our new structural model for the Pataz vein system evolution highlights the importance of basement structural inheritance in controlling the localization of gold mineralization along polycyclic supercontinent margins. We provide valuable insights for exploration targeting of complex vein arrays within rheologically heterogeneous host rocks.

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Albu, István, and Antal Pápa. "Application of high‐resolution seismics in studying reservoir characteristics of hydrocarbon deposits in Hungary." GEOPHYSICS 57, no. 8 (August 1992): 1068–88. http://dx.doi.org/10.1190/1.1443319.

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In preparing for the production of hydrocarbons, there is an increasing demand for surface geophysics. We studied the potential of seismic reflection—and within this, how to increase resolution—when the reservoir is very inhomogeneous and is covered with a thick (∼2 km) young sedimentary sequence of high energy absorption. For high and nearly uniform resolution the lower frequency limit of sweep should be increased to at least 16–18 Hz, in addition to extending the frequency band upward. We carried out measurements over a gas‐capped reservoir made up of Badenian sandstone and a conglomerate of primary and Precambrian metamorphic rocks of secondary porosity, using a sweep from 18–92 Hz. Time sections contain high frequencies, with the upper frequency limit of trace spectra reaching 80 Hz. These time sections enabled us to extrapolate well data laterally. The structure of the reservoir can be mapped and zones barren because of geometric reasons delineated. Not only can rock units of primary and secondary porosity be distinguished but identifiable reflections could be obtained from the boundaries of sandstone and conglomerate beds about 25-m thick in the Badenian sequence. The dynamic features of reflections from the hydrocarbon‐water boundary observed in the region of secondary porosity indicate the grade of tectonization almost independently of pore fluid, and brecciated parts could be distinguished. Velocity anomalies in the Lower Pannonian sequence reveal a 10–18-m thick gas‐bearing sandstone layer. Wells drilled after our studies confirmed our conclusions.

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Raven, K. G., K. S. Novakowski, R. M. Yager, and R. J. Heystee. "Supernormal fluid pressures in sedimentary rocks of southern Ontario – western New York State." Canadian Geotechnical Journal 29, no. 1 (February 1, 1992): 80–93. http://dx.doi.org/10.1139/t92-009.

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Fluid pressures up to 1.7 times greater than hydrostatic have been measured in argillaceous Paleozoic rocks of low permeability in southern Ontario and western New York State. These supernormal formation fluid pressures were measured at depths of 50–310 m using submersible pressure transducers with straddle packers and multiple-packer casings isolating the test intervals. Measurements were obtained over periods of 7–46 months following casing installations. The pressure measurements from 11 monitoring wells are compiled and supporting hydrogeologic data for 5 selected wells are used as examples to illustrate the occurrence of supernormal fluid pressures in the Ordovician, Silurian, and Devonian sedimentary sequence of southern Ontario and western New York State. Possible explanations for the occurrence of supernormal fluid pressures in sedimentary rock are evaluated considering the available geologic and hydrogeologic information obtained from the monitoring wells. Based on this review, it is hypothesized that gas migration and accumulation from deeper distant sources via permeable vertical pathways is the most plausible explanation for the observed fluid pressures, although secondary contributions from local neotectonic activity are also possible. The implications of such supernormal fluid pressures on regional groundwater flow in sedimentary rocks and related activities such as waste disposal in sedimentary rock are briefly discussed. Key words : supernormal fluid pressure, sedimentary rocks, gas migration.

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Walton, K., and P. J. Digby. "Wave Propagation Through Fluid Saturated Porous Rocks." Journal of Applied Mechanics 54, no. 4 (December 1, 1987): 788–93. http://dx.doi.org/10.1115/1.3173118.

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A sedimentary rock is modeled by a random packing of identical spherical particles. The connected pore space is filled with an inviscid, compressible fluid. A low-frequency expansion technique is used to calculate the effective wave speeds explicitly in terms of the microstructural properties of the rock considered. The effect of both the pore fluid and the initial confining pressure to which the rock is subjected can be included in the calculations.

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Li, Qiang. "Geochemistry and Diagenetic Pattern of Ore-Bearing Rocks about Two Types of Gold Deposit in Fengxian-Taibai Basin, South Qinling." Advanced Materials Research 616-618 (December 2012): 240–45. http://dx.doi.org/10.4028/www.scientific.net/amr.616-618.240.

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Baguamiao and Shuangwang gold deposit are two important gold types in Fengxian-Taibai basin. The gold deposits are all located at the bottom of the Upper-Devonian Xing-hongpu Formation. However the ore-bearing rocks are different between them. The ore-bearing rock of Baguamiao gold deposit is ankerite rocks, which is concordant with the strata by bedded or stratoid and assume rhythmic layering form. The ore-bearing rock of Shuangwang gold deposit is albite breccias, which are mostly lens-shaped. The data of petrochemistry show that both of them are poor in Fe2O3 and K2O, which are different from normal sedimentary rocks. The elements contents of Cu, Pb and Zn are close to Clarke value. But the content of dispersed element Ge is rich in rocks, which reflect hydrothermal sedimentary origin. The characteristic of REE are different between them. The REE contents of ankerite rocks are low and elements of Ce and Eu are positive anomaly. The REE contents of albite breccias are close to regional strata and elements of Ce and Eu are middle negative. The chondrite-normalized REE patterns are also alike. It’s shown that the diagenetic fluid are high-density which been mixed by sea water slightly. So the ankerite rocks hold the REE characteristic of thermal fluid. The diagenetic fluid of albite breccias are low-density thermal fluid which been mixed by sea water intensively. It has same REE characteristic to normal sedimentary rocks.

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Ignatov, P. A., K. V. Novikov, N. R. Zaripov, M. S. Khodnia, A. A. Burmistrov, L. V. Liskovaya, and O. K. Kilizhekov. "Eruptive fluid fracture formations of Nakyn diamondiferous field of Yakutia." Moscow University Bulletin. Series 4. Geology, no. 6 (December 28, 2018): 37–44. http://dx.doi.org/10.33623/0579-9406-2018-6-37-44.

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In Nakyn diamondiferous field of West-Yakutian province various fluid fracture rocks determined, including kimberlites, eruptive breccias of basites, fluid fracture carbonate breccias and accompanying fluidizite streaks. Shown their characteristic petrographic features and regularity of distribution in the rocks of the lower Paleozoic sedimentary cover. Revealed a predominant tectonic control of fluid fracture formations with bi — and confocal distribution. Suggested the formation of these fluid fracture rocks as a result of different ages directed at faults phreatic explosions.

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Wang, J. A., and H. D. Park. "Fluid permeability of sedimentary rocks in a complete stress–strain process." Engineering Geology 63, no. 3-4 (March 2002): 291–300. http://dx.doi.org/10.1016/s0013-7952(01)00088-6.

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Brigaud, Frédéric, and Guy Vasseur. "Mineralogy, porosity and fluid control on thermal conductivity of sedimentary rocks." Geophysical Journal International 98, no. 3 (September 1989): 525–42. http://dx.doi.org/10.1111/j.1365-246x.1989.tb02287.x.

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Muller, J., and J. L. McCauley. "Implication of fractal geometry for fluid flow properties of sedimentary rocks." Transport in Porous Media 8, no. 2 (June 1992): 133–47. http://dx.doi.org/10.1007/bf00617114.

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House, L. S., and R. Flores. "Seismological Studies of a Fluid Injection in Sedimentary Rocks, East Texas." Pure and Applied Geophysics 159, no. 1 (January 2002): 371–401. http://dx.doi.org/10.1007/pl00001257.

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Murphy, William F., Kenneth W. Winkler, and Robert L. Kleinberg. "Acoustic relaxation in sedimentary rocks: Dependence on grain contacts and fluid saturation." GEOPHYSICS 51, no. 3 (March 1986): 757–66. http://dx.doi.org/10.1190/1.1442128.

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Partial fluid saturation affects absorption and dispersion in sandstones. The proposed theoretical model describes acoustic relaxation due to local fluid flow. Previously proposed models of local flow were based on microgeometries not representative of sedimentary rocks; they were unable to describe the behavior of partially saturated sandstones. The new model is based upon observed microstructures in sandstones. A fraction of the grain contacts in sandstones are permeated by sheet‐like gaps. The incomplete solid‐solid contact allows an interconnected fluid film to exist between the grain surfaces. The model consists of a narrow gap connected to a finite annular pore. An acoustic stress wave drives the film out of the narrow contact region and into the adjacent pore. The viscous flow results in a dissipation of energy. The model predicts the real and imaginary parts of the complex frame moduli as a function of frequency and fluid saturation. The predictions agree well with experimental results.

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Hall, P. L., D. M. Astill, and J. D. C. McConnell. "Thermodynamic and structural aspects of the dehydration of smectites in sedimentary rocks." Clay Minerals 21, no. 4 (October 1986): 633–48. http://dx.doi.org/10.1180/claymin.1986.021.4.13.

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AbstractThe diagenetic conversion of smectite to illite in shales has been proposed as a mechanism for generating overpressure (fluid pressure above hydrostatic) in sedimentary basins. However, the mechanism and rate-controlling factors of the reaction and the magnitude of the resulting volume change are not known. In this paper the thermodynamics of the reversible hydration/dehydration of smectite are analysed in the pressure/temperature regime of sedimentary rocks. If the interlamellar water is more dense than bulk water, and the pressures on the solid and fluid phases are equal, the dehydration temperature should increase with increasing confining pressureviathe Clapeyron-Clausius equation. However, either fluid pressures below the pressure on the solid matrix or high pore-fluid salinities can reduce the dehydration temperature. Experiments on Ca2+-montmorillonite compacted in the presence of distilled water in a steel autoclave fitted with a sensitive pressure transducer failed to detect any overall volume change due to dehydration up to 185°C and 1400 bar. This finding, which is consistent with recent high-pressure DTA and XRD studies on Na+-montmorillonite, suggests that reversible loss of the last two water layers does not occur in sedimentary basins except as part of the more complex diagenetic conversion of smectite to illite. Some recent evidence from high-resolution TEM and microprobe analyses regarding the mechanism of the reaction is also discussed.

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Sheng, Ping. "Consistent modeling of the electrical and elastic properties of sedimentary rocks." GEOPHYSICS 56, no. 8 (August 1991): 1236–43. http://dx.doi.org/10.1190/1.1443143.

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An effective medium theory is formulated which reproduces many of the observed electrical and elastic characteristics of sedimentary rocks within a unified framework. The effective medium consists of fluid, solid, and cement components, with the component material properties related to those of the composite through a differential effective medium (DEM) scheme. The resulting microstructure of the composite both conducts electricity through the fluid phase and supports shear. Besides deriving Archie’s law, the theory gives an excellent account of the shear‐wave and compressional‐wave velocity correlations, and predicts corrections to the Wyllie equation that are consistent with observed deviations. The three‐component DEM also accommodates clay conductivity and finite‐frequency dielectric behavior.

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LIFSHITS, Sara. "Deep fluids and their role in hydrocarbon migration and oil deposit formation exemplified by supercritical СO2." Earth and Environmental Science Transactions of the Royal Society of Edinburgh 112, no. 1 (March 2021): 1–11. http://dx.doi.org/10.1017/s1755691021000013.

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ABSTRACTHydrocarbon migration mechanism into a reservoir is one of the most controversial in oil and gas geology. The research aimed to study the effect of supercritical carbon dioxide (СО2) on the permeability of sedimentary rocks (carbonates, argillite, oil shale), which was assessed by the yield of chloroform extracts and gas permeability (carbonate, argillite) before and after the treatment of rocks with supercritical СО2. An increase in the permeability of dense potentially oil-source rocks has been noted, which is explained by the dissolution of carbonates to bicarbonates due to the high chemical activity of supercritical СО2 and water dissolved in it. Similarly, in geological processes, the introduction of deep supercritical fluid into sedimentary rocks can increase the permeability and, possibly, the porosity of rocks, which will facilitate the primary migration of hydrocarbons and improve the reservoir properties of the rocks. The considered mechanism of hydrocarbon migration in the flow of deep supercritical fluid makes it possible to revise the time and duration of the formation of gas–oil deposits decreasingly, as well as to explain features in the formation of various sources of hydrocarbons and observed inflow of oil into operating and exhausted wells.

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Denge, Elelwani, and Christopher Baiyegunhi. "Geochemical and Petrographical Characteristics of the Madzaringwe Formation Coal, Mudrocks and Sandstones in the Vele Colliery, Limpopo Province, South Africa: Implications for Tectonic Setting, Provenance and Paleoweathering." Applied Sciences 11, no. 6 (March 19, 2021): 2782. http://dx.doi.org/10.3390/app11062782.

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The sedimentary rocks of the Madzaringwe Formation in the Tuli Basin have been investigated using geochemical and petrographic methods to reveal their source area composition, tectonic setting, provenance and paleoweathering conditions. The petrographic studies show that the rocks consist mostly of clay minerals and quartz. The major elements geochemistry indicates that the rocks of the Madzaringwe Formation have the same source area. Based on the discriminant function plots, it can be inferred that the rocks are of quartzose sedimentary provenance, suggesting that they were derived from a cratonic interior or recycled orogen. The binary plots of TiO2 versus Zr and La/Sr against Th/Co shows that the rocks were derived from silicic or felsic igneous rocks. The tectonic setting discrimination diagrams of SiO2 against Log (K2O/Na2O), Th–Sc–Zr/10, and TiO2 versus (Fe2O3 + MgO) support passive-active continental margin settings of the provenance. The A–CN–K (Al2O3–CaO + Na2O–K2O) ternary diagram and binary plot of the index of compositional variability (ICV) against chemical index of alteration (CIA) shows that the rocks have been subjected to moderate to intensive weathering. Geochemical and petrographic characteristics of the rocks point to uplifted basement source areas predominantly composed of sedimentary rocks and/or granite-gneiss rocks. These source areas might have been from adjacent areas near the Tuli coalfield which include the Limpopo Belt (igneous and sedimentary rocks), and basement uplifted rocks of the Beit-Bridge Complex, consisting of the granite, granite-gneisses and schists.

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Wang, Zhijing. "Seismic anisotropy in sedimentary rocks, part 1: A single‐plug laboratory method." GEOPHYSICS 67, no. 5 (September 2002): 1415–22. http://dx.doi.org/10.1190/1.1512787.

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A single‐plug method for measuring seismic velocities and transverse isotropy in rocks has been rigorously validated and laboratory tested. The method requires only one sample to measure the velocities needed to derive the five independent elastic constants for transversely isotropic materials. In this method, piezoelectric transducers are fitted to the top, bottom, and sides of the cylindrical sample. Laboratory velocity and anisotropy can be measured as functions of pressure, temperature, fluid saturation, and fluid displacement. Because this method uses a horizontal core plug that has much higher permeability than a vertical core plug, it is especially suitable for low‐permeability shale measurements. It reduces the sample preparation and velocity measurement time by more than two‐thirds.

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Vo-Thanh, Dung. "Influence of fluid chemistry on shear-wave attenuation and velocity in sedimentary rocks." Geophysical Journal International 121, no. 3 (June 1995): 737–49. http://dx.doi.org/10.1111/j.1365-246x.1995.tb06435.x.

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SAEIN, ALI FARZIPOUR, and ZAHRA TAJMIR RIAHI. "Controls on fracture distribution in Cretaceous sedimentary rocks from the Isfahan region, Iran." Geological Magazine 156, no. 06 (May 25, 2017): 1092–104. http://dx.doi.org/10.1017/s0016756817000346.

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AbstractIn this study, relationships between fracture patterns, lithology, thickness, diagenetic processes and grain size are evaluated within Cretaceous sediments in two sections of Dizlu and Kolah Ghazi of Isfahan. This study area was selected based on its outcrops of different rock units and its well-developed tectonic fractures. The fracture patterns within stratigraphic units of these sections are studied using geometrical and statistical analyses. This study finds that variable fracture spacing and fracture spacing ratios can be affected by lithology, thickness, grain size of sediments and diagenetic processes. A study of fracture stratigraphy based on fracture pattern evaluation within different cropped-out sedimentary rocks can be used to improve understanding of the same types of sedimentary rock units below the surface or throughout other sedimentary basins. Consequently, this could improve information regarding storage and fluid flow pattern throughout sedimentary rocks in different regions, even for subsurface purposes.

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Bayer, U., D. Gajewski, and R. Littke. "Sedimentary basin evolution: subsidence, salt dynamics, fluid flow and deformation." International Journal of Earth Sciences 97, no. 5 (February 20, 2008): 883–86. http://dx.doi.org/10.1007/s00531-008-0300-9.

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Posenato Garcia, A., and Z. Heidari. "Multifrequency Analytical Forward Modeling of Dielectric Permittivity Dispersion in Mixed-Wet Sedimentary Rocks." SPE Reservoir Evaluation & Engineering 24, no. 02 (January 12, 2021): 450–61. http://dx.doi.org/10.2118/205002-pa.

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Summary The dominant wettability of reservoir rocks is one of the main factors affecting the spatial distribution of fluids inside the pore space. More specifically, wettability controls the fluid type that coats the surface of the grains and, hence, the establishment of an electric double layer (EDL) at the solid–liquid interface. These factors, namely fluid distribution and EDL, affect the conductivity and permittivity of the rock in unique ways. Therefore, interpretation of multifrequency complex permittivity measurements can be used to quantify the wettability and parameters affecting the double layer (e.g., grain size) in addition to porosity and fluid saturation. In this paper, we introduce an analytical model to reliably characterize the dielectric permittivity dispersion of mixed-wet sedimentary rocks. The analytical derivation of the rock-physics model results in physically meaningful parameters, associated with either microscopic polarization mechanisms or pore-network geometry. We incorporate the contribution of the complex impedance associated with the EDL to the complex permittivity of the rock through a mechanistic model of Stern and Gouy-Chapman layers. Then, we quantify the contribution of different fluid and grain types to the electrical response of sedimentary rocks through Hanai–Bruggeman effective medium model. The sequential application of Hanai-Bruggeman is specifically designed to make the dependence of complex permittivity on wettability explicit. We successfully verified the reliability of the new analytical model using experimental measurements performed on two water-wet and two hydrocarbon-wet sandstone core samples. The experimental measurements were in agreement with the complex permittivity calculated using the new analytical model in the frequency range of 100 Hz to 10 MHz. Furthermore, the introduced model provides a physical interpretation to the experimentally detectable influence of wettability on the complex dielectric permittivity of rocks. Consequently, the outcomes of this paper will enhance petrophysical evaluation in mixed-wet formations by providing a novel interpretation method for complex permittivity dispersion measurements.

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Lentz, David R., and Wayne D. Goodfellow. "Intense silicification of footwall sedimentary rocks in the stockwork alteration zone beneath the Brunswick No. 12 massive sulphide deposit, Bathurst, New Brunswick." Canadian Journal of Earth Sciences 33, no. 2 (February 1, 1996): 284–302. http://dx.doi.org/10.1139/e96-022.

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Intensely silicified volcaniclastic mudstones that underlie the Brunswick No. 12 massive sulphide deposit in northern New Brunswick resemble silicified rocks described in the immediate footwall of many ancient and modern massive sulphide deposits. The white to grey, cryptocrystalline silica in the silicified rocks becomes more common with proximity to the vent, and is most abundant immediately below the massive sulphide zone. Mass-balance analysis of altered footwall sedimentary rocks on the 850 m level of the mine shows that SiO2 increases up to 300%. The high silica enrichment in the feeder zone is consistent with the presence of cherty silica in the massive sulphides and in associated exhalative iron formation. Coincident with silicification are enrichments in S, FeOt, MgO, MnO, CaO, P2O5, F, Cl, Y, Cu, Co, Cr, and Ni, as well as light rare earth elements and Eu. Oxygen isotope analyses of chloritized and silicified footwall sedimentary rocks suggest that the hydrothermal fluid had a δ18O composition of approximately 4[Formula: see text] and probably was dominated by chemically modified sea water. Rapid oversaturation of the silica-bearing fluid likely explains the intensity and fine-grained nature of this silicification, although the actual mechanism for this oversaturation is uncertain.

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Batzle, Michael L., De-Hua Han, and Ronny Hofmann. "Fluid mobility and frequency-dependent seismic velocity — Direct measurements." GEOPHYSICS 71, no. 1 (January 2006): N1—N9. http://dx.doi.org/10.1190/1.2159053.

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The influence of fluid mobility on seismic velocity dispersion is directly observed in laboratory measurements from seismic to ultrasonic frequencies. A forced-deformation system is used in conjunction with pulse transmission to obtain elastic properties at seismic strain amplitude ([Formula: see text]) from 5 Hz to 800 kHz. Varying fluid types and saturations document the influence of pore-fluids. The ratio of rock permeability to fluid viscosity defines mobility, which largely controls pore-fluid motion and pore pressure in a porous medium. High fluid mobility permits pore-pressure equilibrium either between pores or between heterogeneous regions, resulting in a low-frequency domain where Gassmann's equations are valid. In contrast, low fluid mobility can produce strong dispersion, even within the seismic band. Here, the low-frequency assumption fails. Since most rocks in the general sedimentary section have very low permeability and fluid mobility (shales, siltstones, tight limestones, etc.), most rocks are not in the low-frequency domain, even at seismic frequencies. Only those rocks with high permeability (porous sands and carbonates) will remain in the low-frequency domain in the seismic or sonic band.

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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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Merlani, Antonio Luigi, Guiseppe Natale, and Ettore Salusti. "Pressure and temperature dynamics in fluid-saturated porous-permeable rocks." Physica D: Nonlinear Phenomena 90, no. 1-2 (January 1996): 154–69. http://dx.doi.org/10.1016/0167-2789(95)00228-6.

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Posenato Garcia, Artur, and Zoya Heidari. "Numerical modeling of multifrequency complex dielectric permittivity dispersion of sedimentary rocks." GEOPHYSICS 86, no. 4 (June 10, 2021): MR179—MR190. http://dx.doi.org/10.1190/geo2020-0444.1.

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The dielectric response of rocks results from electric double layer (EDL), Maxwell-Wagner (MW), and dipolar polarizations. The EDL polarization is a function of solid-fluid interfaces, pore water, and pore geometry. MW and dipolar polarizations are functions of charge accumulation at the interface between materials with contrasting impedances and the volumetric concentration of its constituents, respectively. However, conventional interpretation of dielectric measurements only accounts for volumetric concentrations of rock components and their permittivities, not interfacial properties such as wettability. Numerical simulations of the dielectric response of rocks provide an ideal framework to quantify the impact of wettability and water saturation ([Formula: see text]) on electric polarization mechanisms. Therefore, we have developed a numerical simulation method to compute pore-scale dielectric dispersion effects in the interval from 100 Hz to 1 GHz including effects of pore structure, [Formula: see text], and wettability on permittivity measurements. We solve the quasielectrostatic Maxwell’s equations in 3D pore-scale rock images in the frequency domain using the finite-volume method. Then, we verify simulation results for a spherical material by comparing to the corresponding analytical solution. Additionally, we introduce a technique to incorporate [Formula: see text]-polarization to the simulation and we verify it by comparing pore-scale simulation results to experimental measurements on a Berea sandstone sample. Finally, we quantify the impact of [Formula: see text] and wettability on broadband dielectric permittivity measurements through pore-scale numerical simulations. The numerical simulation results show that mixed-wet rocks are more sensitive than water-wet rocks to changes in [Formula: see text] at sub-MHz frequencies. Furthermore, permittivity and conductivity of mixed-wet rocks have weaker and stronger dispersive behaviors, respectively, when compared to water-wet rocks. Finally, numerical simulations indicate that conductivity of mixed-wet rocks can vary by three orders of magnitude from 100 Hz to 1 GHz. Therefore, Archie’s equation calibrated at the wrong frequency could lead to water saturation errors of up to 73%.

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LEDEVIN, MORGANE, NICHOLAS ARNDT, MARK R. COOPER, GARTH EARLS, PAUL LYLE, CHARLES AUBOURG, and ERIC LEWIN. "Intrusion history of the Portrush Sill, County Antrim, Northern Ireland: evidence for rapid emplacement and high-temperature contact metamorphism." Geological Magazine 149, no. 1 (September 19, 2011): 67–79. http://dx.doi.org/10.1017/s0016756811000537.

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AbstractThe gabbroic Portrush Sill in Northern Ireland, part of the North Atlantic Igneous Province, intruded Lower Jurassic mudstones and siltstones about 55 Ma ago. We used petrologic observations and geochemical analyses to study how the sill interacted with the sedimentary rocks. Field relationships show that an Upper Sill and numerous associated Minor Intrusions were emplaced in the sedimentary host rocks before intrusion of the Main Sill, some 10 m above its upper contact. Geochemical analyses reveal two magma contamination processes: Nb and Ta anomalies, coupled with incompatible element enrichment, record contamination by deep crustal rocks, whereas Li, Pb and Ba anomalies reveal a superficial contamination through fluid circulation at the contact between magmatic and sedimentary rocks. Analysis of mineral assemblages and geochemical data from the contact aureole demonstrate uniform metamorphic conditions between the two main intrusions and an absence of a thermal gradient. The identification of pyrrhotite by magnetization analyses and of orthopyroxene by microprobe analyses indicates very high temperatures, up to 660°C. Thermal modelling explains these temperatures as the coupled effects of the Main Sill and the earlier intruded Upper Sill and Minor Intrusions. Even though the chemical composition of the Main Sill suggests another type of parental liquid, all three units were emplaced in a very short time, certainly less than five years.

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Giuliani, Gaston, Lee A. Groat, Dan Marshall, Anthony E. Fallick, and Yannick Branquet. "Emerald Deposits: A Review and Enhanced Classification." Minerals 9, no. 2 (February 13, 2019): 105. http://dx.doi.org/10.3390/min9020105.

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Although emerald deposits are relatively rare, they can be formed in several different, butspecific geologic settings and the classification systems and models currently used to describeemerald precipitation and predict its occurrence are too restrictive, leading to confusion as to theexact mode of formation for some emerald deposits. Generally speaking, emerald is beryl withsufficient concentrations of the chromophores, chromium and vanadium, to result in green andsometimes bluish green or yellowish green crystals. The limiting factor in the formation of emeraldis geological conditions resulting in an environment rich in both beryllium and chromium orvanadium. Historically, emerald deposits have been classified into three broad types. The first andmost abundant deposit type, in terms of production, is the desilicated pegmatite related type thatformed via the interaction of metasomatic fluids with beryllium-rich pegmatites, or similar graniticbodies, that intruded into chromium- or vanadium-rich rocks, such as ultramafic and volcanic rocks,or shales derived from those rocks. A second deposit type, accounting for most of the emerald ofgem quality, is the sedimentary type, which generally involves the interaction, along faults andfractures, of upper level crustal brines rich in Be from evaporite interaction with shales and otherCr- and/or V-bearing sedimentary rocks. The third, and comparatively most rare, deposit type is themetamorphic-metasomatic deposit. In this deposit model, deeper crustal fluids circulate along faultsor shear zones and interact with metamorphosed shales, carbonates, and ultramafic rocks, and Beand Cr (±V) may either be transported to the deposition site via the fluids or already be present inthe host metamorphic rocks intersected by the faults or shear zones. All three emerald depositmodels require some level of tectonic activity and often continued tectonic activity can result in themetamorphism of an existing sedimentary or magmatic type deposit. In the extreme, at deepercrustal levels, high-grade metamorphism can result in the partial melting of metamorphic rocks,blurring the distinction between metamorphic and magmatic deposit types. In the present paper,we propose an enhanced classification for emerald deposits based on the geological environment,i.e., magmatic or metamorphic; host-rocks type, i.e., mafic-ultramafic rocks, sedimentary rocks, andgranitoids; degree of metamorphism; styles of minerlization, i.e., veins, pods, metasomatites, shearzone; type of fluids and their temperature, pressure, composition. The new classification accountsfor multi-stage formation of the deposits and ages of formation, as well as probable remobilizationof previous beryllium mineralization, such as pegmatite intrusions in mafic-ultramafic rocks. Suchnew considerations use the concept of genetic models based on studies employing chemical,geochemical, radiogenic, and stable isotope, and fluid and solid inclusion fingerprints. The emerald occurrences and deposits are classified into two main types: (Type I) Tectonic magmatic-relatedwith sub-types hosted in: (IA) Mafic-ultramafic rocks (Brazil, Zambia, Russia, and others); (IB)Sedimentary rocks (China, Canada, Norway, Kazakhstan, Australia); (IC) Granitic rocks (Nigeria).(Type II) Tectonic metamorphic-related with sub-types hosted in: (IIA) Mafic-ultramafic rocks(Brazil, Austria); (IIB) Sedimentary rocks-black shale (Colombia, Canada, USA); (IIC) Metamorphicrocks (China, Afghanistan, USA); (IID) Metamorphosed and remobilized either type I deposits orhidden granitic intrusion-related (Austria, Egypt, Australia, Pakistan), and some unclassifieddeposits.

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Kim, Wonnyon, Seong-Jae Doh, Yongjae Yu, Jeong Jick Lee, and Dongwoo Suk. "Hydrothermal fluid-controlled remagnetization of sedimentary rocks in Korea: Tectonic importance of pervasive Tertiary remagnetization." Tectonophysics 474, no. 3-4 (September 2009): 684–95. http://dx.doi.org/10.1016/j.tecto.2009.05.014.

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Masurel, Quentin, Paul Morley, Nicolas Thébaud, and Helen McFarlane. "Gold Deposits of the ~15-Moz Ahafo South Camp, Sefwi Granite-Greenstone Belt, Ghana: Insights into the Anatomy of an Orogenic Gold Plumbing System." Economic Geology 116, no. 6 (September 1, 2021): 1329–53. http://dx.doi.org/10.5382/econgeo.4829.

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Abstract The ~15-Moz Ahafo South gold camp is located in southwest Ghana, the world’s premier Paleoproterozoic gold subprovince. Major orogenic gold deposits in the camp include Subika, Apensu, Awonsu, and Amoma. These deposits occur along an ~15-km strike length of the Kenyase-Yamfo shear zone, a major tectonostratigraphic boundary juxtaposing metamorphosed volcano-plutonic rocks of the Sefwi belt against metamorphosed volcano-sedimentary rocks of the Sunyani-Comoé basin. In this study, we document the geologic setting, structural geometry, and rheological architecture of the Ahafo South gold deposits based on the integration of field mapping, diamond drill core logging, 3-D geologic modeling, and the geologic interpretation of aeromagnetic data. At the camp scale, the Awonsu, Apensu, and Amoma deposits lie along strike from one another and share similar hanging-wall plutonic rocks and footwall volcano-sedimentary rocks. In contrast, the Subika gold deposit is hosted entirely in hanging-wall plutonic rocks. Steeper-dipping segments (e.g., Apensu, Awonsu, Subika) and right-hand flexures (e.g., Amoma, Apensu) in the Kenyase-Yamfo shear zone and subsidiary structures appear to have represented sites of enhanced damage and fluid flux (i.e., restraining bends). All gold deposits occur within structural domains bounded by discontinuous, low-displacement, sinistral N-striking tear faults oblique to the orogen-parallel Kenyase-Yamfo shear zone. At the deposit scale, ore-related hydrothermal alteration is zoned, with distal chlorite-sericite grading into proximal silica-albite-Fe-carbonate mineral assemblages. Alteration halos are restricted to narrow selvages around quartz-carbonate vein arrays in multiple stacked ore shoots at Subika, whereas these halos extend 30 to 100 m away from the ore zones at Apensu and Awonsu. There is a clear spatial association between shallow-dipping mafic dikes, mafic chonoliths, shear zones, and economic gold mineralization. The abundance of mafic dikes and chonoliths within intermediate to felsic hanging-wall plutonic host rocks provided rheological heterogeneity that favored the formation of enhanced fracture permeability, promoting the tapping of ore fluid(s). Our interpretation is that these stacked shallow-dipping mafic dike arrays also acted as aquitards, impeding upward fluid flow within the wider intrusive rock mass until a failure threshold was episodically reached due to fluid overpressure, resulting in transient fracture-controlled upward propagation of the ore-fluid(s). Our results indicate that high-grade ore shoots at Ahafo South form part of vertically extensive fluid conduit systems that are primarily controlled by the rheological architecture of the rock mass.

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Matt, Peter, Wayne Powell, Richard Volkert, Matthew Gorring, and Al Johnson. "Sedimentary exhalative origin for magnetite deposits of the New Jersey Highlands." Canadian Journal of Earth Sciences 54, no. 9 (September 2017): 1008–23. http://dx.doi.org/10.1139/cjes-2017-0004.

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The New Jersey Highlands and contiguous Hudson (New York) Highlands host hundreds of small, worked-out magnetite mines, and the major zinc-oxide deposits of Franklin and Sterling Hill. The origin of the magnetite ore remains controversial. Two temporally distinct genetic models have been proposed for magnetite: (1) a pre-Ottawan, sedimentary exhalative model in which ores were deposited on the seafloor as precipitates from iron-enriched hydrothermal fluids; (2) a late-Ottawan, fluid alteration model in which the current mineral composition of ores was derived from Fe-rich, alkaline fluids, associated with late episodes of granitic plutonism (low-Ti Kiruna-type deposits), or in which deposits derived from metamorphogenic fluids circulating in a regional shear zone leached metals from host rocks and precipitated them in veins and faults. Detailed mapping of ore deposits and host rocks near Wanaque and Ringwood, New Jersey, and Warwick, New York, reveal that ore bodies are hosted by supracrustal rocks deposited in a back-arc basin. At Wanaque and Warwick, ores are strataform and stratabound. Discordant ore bodies at Ringwood are associated with a feeder zone, presumed to have intersected the paleosurface at a steep angle. Sharply layered quartz–diopside gneiss is spatially associated with ore at Wanaque and Warwick, and massive diopsidite is spatially associated with ore at all three locations. Diopsidite in these rocks is nonaluminous, iron enriched, and shares these characteristics with modern metalliferous sediments. Massive diopsidite and quartz–diopside gneiss are interpreted to be metamorphosed carbonate facies iron formation, and associated magnetite to be metamorphosed oxide-facies iron formation.

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Sutanto, E. "Cryo-SEM of liquid-bearing rock." Proceedings, annual meeting, Electron Microscopy Society of America 46 (1988): 104–5. http://dx.doi.org/10.1017/s0424820100102602.

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Scanning electron microscopy has been used to examine microstructure of dry soils, sedimentary rocks and other porous materials for three decades. There are many studies of sand grain surface texture, pore morphology, and clay swelling. However, pore geometry and surface topography are only part of the story of how two or more fluids flow through porous media, whether they be unconsolidated or consolidated. The other part is how the fluids distribute in the pore space. Fluid distribution in pore space is largely governed by relative wettability of pore walls. Wetting fluid tends to reside on walls as a thin film and to occupy small pores totally, whereas nonwetting fluid tends to occupy the center of larger pores. Which fluid is more strongly wetting depends on the local nature of the wall. Contact angles indicate wettability of planar, homogeneous solid surfaces, but roughness and compositional heterogeneity, which seem to be common in sedimentary rock, complicate matters.

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Cao, Xiao Feng, Xin Biao Lu, Shen Tai Liu, Ping Zhang, Xiang Gao, Yue Gao Liu, and Qi Tao Hu. "Ore Genesis of Caixiashan Pb-Zn Deposit in Middle Tianshan, NW China." Advanced Materials Research 455-456 (January 2012): 1366–70. http://dx.doi.org/10.4028/www.scientific.net/amr.455-456.1366.

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Caixiashan Pb-Zn deposit is the largest Pb-Zn deposit discovered in the middle Tianshan area. Examples of Carboniferous magmatic and tectonic activity are widely distributed. The ore bodies are controlled by EW trend faults, based on field observations. The main ore minerals are galena, sphalerite, pyrrhotite, pyrite and chalcopyrite, while quartz, sericite and calcite are the main alteration minerals. The ore also exhibits minerals zoning. In addition, the wide range of S isotopic composition, high temperature and moderate salinity of fluid inclusions, and good correlation of ore and wall rock Pb isotopes together with H, O, C isotopic compositions indicate mixing of magmatic origin and upper sedimentary rocks. Combined with high concentration of pyrite and pyrrhotite and some argentite, the Pb-Zn deposit may be controlled by the Hercynian orogeny, which controlled the EW-NEE faults and Carboniferous igneous rocks. The faults provided the channel for fluid transport and the igneous rocks provided heat and main source of the metals. When the fluid passed through metal-bearing rocks, it extracted Pb, Zn, Ag etc.. Interaction of the metal-bearing fluid with the brecciated and fractured marble caused the metals to be deposited. Thus the Caixiashan Pb-Zn deposit is a fault-controlled hydrothermal deposit.

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SUN, YUE-FENG. "A TWO-PARAMETER MODEL OF ELASTIC WAVE VELOCITIES IN ROCKS AND NUMERICAL AVO MODELING." Journal of Computational Acoustics 12, no. 04 (December 2004): 619–30. http://dx.doi.org/10.1142/s0218396x04002432.

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Acoustic wave propagation is sensitive to many rock properties including fluid content, porosity, and pore structure, among others. Pore structure is one of the important parameters in controlling both seismic wave velocity and permeability in sandstones and carbonate rocks. For a given porosity of two similar rocks with different pore structure, their acoustic wave speeds can differ 2 km/s and permeability can span nearly six orders of magnitude from 0.01 mD to 20 D in both sandstones and limestones. In this paper, we introduce a two-parameter velocity model defined by porosity and a new pore structure parameter called as frame flexibility factor. Using this model, we define three pore structure types (PST) to quantify the pore structure effects on elastic properties of sedimentary rocks. These three PSTs have their distinct characteristics on synthetic shot gathers and common midpoint gathers. This study indicates that it may be feasible to use this new concept and method to detect pore structure variations in reservoir rocks from field seismic data. This study also helps explain why analysis of amplitude variation with offset (AVO) in some cases fails for fluid detection: pore structure effect on seismic waves can mask all the fluid effects, especially in carbonate rocks.

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Zhang, Shawn, Lyn Canter, and Mark Sonnenfeld. "Capillary fluid dynamics within unconventional rocks investigated by scanning electron microscopy." AAPG Bulletin 101, no. 11 (November 2017): 1759–65. http://dx.doi.org/10.1306/01111716095.

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Dimmen, Vilde, Atle Rotevatn, and Casey W. Nixon. "The Relationship between Fluid Flow, Structures, and Depositional Architecture in Sedimentary Rocks: An Example-Based Overview." Geofluids 2020 (July 14, 2020): 1–19. http://dx.doi.org/10.1155/2020/3506743.

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Fluid flow in the subsurface is fundamental in a variety of geological processes including volcanism, metamorphism, and mineral dissolution and precipitation. It is also of economic and societal significance given its relevance, for example, within groundwater and contaminant transport, hydrocarbon migration, and precipitation of ore-forming minerals. In this example-based overview, we use the distribution of iron oxide precipitates as a proxy for palaeofluid flow to investigate the relationship between fluid flow, geological structures, and depositional architecture in sedimentary rocks. We analyse and discuss a number of outcrop examples from sandstones and carbonate rocks in New Zealand, Malta, and Utah (USA), showing controls on fluid flow ranging from simple geological heterogeneities to more complex networks of structures. Based on our observations and review of a wide range of the published literature, we conclude that flow within structures and networks is primarily controlled by structure type (e.g., joint and deformation band), geometry (e.g., length and orientation), connectivity (i.e., number of connections in a network), kinematics (e.g., dilation and compaction), and interactions (e.g., relays and intersections) within the network. Additionally, host rock properties and depositional architecture represent important controls on flow and may interfere to create hybrid networks, which are networks of combined structural and stratal conduits for flow.

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Fernø, M. A., J. Gauteplass, L. P. Hauge, G. E. Abell, T. C. H. Adamsen, and A. Graue. "Combined positron emission tomography and computed tomography to visualize and quantify fluid flow in sedimentary rocks." Water Resources Research 51, no. 9 (September 2015): 7811–19. http://dx.doi.org/10.1002/2015wr017130.

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Sadhukhan, Supti, Philippe Gouze, and Tapati Dutta. "Porosity and permeability changes in sedimentary rocks induced by injection of reactive fluid: A simulation model." Journal of Hydrology 450-451 (July 2012): 134–39. http://dx.doi.org/10.1016/j.jhydrol.2012.05.024.

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Journal articles on the topic 'Sedimentary rocks Fluid dynamics'

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