Permeability Evolution during Deformation of Siliciclastic Sandstones from Moab, Utah
O. Kwon, B. T. Ngwenya, I. G. Main, S. C. Elphick, 2005. "Permeability Evolution during Deformation of Siliciclastic Sandstones from Moab, Utah", Faults, Fluid Flow, and Petroleum Traps, Rasoul Sorkhabi, Yoshihiro Tsuji
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We conducted triaxial deformation experiments on large (0.1-m; 0.33-ft)-diameter cores of four sandstones from the Moab area to investigate the effect of total axial strain and effective confining pressure on the evolution of bulk permeability of faulted samples. Sandstones with low bulk porosities (Dewey Bridge and Slickrock Subkha) exhibited an increase in permeability with increasing inelastic axial strain at low effective confining pressures, whereas those with high porosity (Navajo and Slickrock Aeolian) showed a decline in permeability. However, all samples showed permeability decline with increasing inelastic axial strain at high effective confining pressures. Meanwhile, microstructural observations revealed no systematic dependence of the width of the shear zone and the number of deformation bands on either strain or effective confining pressure, although grain-size reduction was more intense at high effective confining pressures. A new geometric model has been developed based on these observations for a constant effective confining pressure and is shown to provide excellent agreement with the experimental data at all effective confining pressures. However, the parameters of the model depend only weakly on effective confining pressure for low-porosity sandstones, suggesting that cataclastic fault seals in low-porosity rocks have a low sensitivity to burial depth in the range studied here.
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Faults, Fluid Flow, and Petroleum Traps
Japan National Oil Corporation (JNOC) (presently Japan Oil, Gas and Metals National Corporation) launched a multidisciplinary and international project on the Evaluation of Traps and Seals in 1997. The project ended in 2003. This publication resulted from that project and includes JNOC research articles as well as contributions from industry and academia. The 17 papers in this volume cover topics such as a method to estimate the amount of oil/gas accumulation using the concept of equivalent grain size in seal rock, and oil/gas migration to and spill-point geometry of petroleum traps; two case studies of fault seal assessment applied to normal faults in Tertiary clastic reservoirs in offshore Sarawak and offshore Gulf of Thailand; and physical analog studies of the development of extensional faults. This publication also contains a valuable bibliography of nearly 1000 additional articles and books published on fault traps, fault seal processes, and fault-related fluid flow in sedimentary basins, for use as a reference tool to delve into publications preceding this volume.