Fault Zone Architecture and Permeability Distribution in the Neogene Clastics of Northern Sarawak (Miri Airport Road Outcrop), Malaysia
Rasoul Sorkhabi, Shutaro Hasegawa, 2005. "Fault Zone Architecture and Permeability Distribution in the Neogene Clastics of Northern Sarawak (Miri Airport Road Outcrop), Malaysia", Faults, Fluid Flow, and Petroleum Traps, Rasoul Sorkhabi, Yoshihiro Tsuji
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The Miri Airport Road outcrop in Miri, Sarawak, exposes a weakly consolidated sandstone-mudstone sequence of Miocene age in the form of a gentle anticline cut by a series of normal faults. An outcrop study of the normal faults shows that fault zones in porous sandstones are characterized by a combination of shale smear and anastomosing deformation bands. The continuity of shale smear on fault offset was observed as having a shale-smear factor (fault throw divided by shale layer thickness) of at least 5. Deformation bands occur as solitary planar structures in the host sandstone away from fault zones but increase markedly in density and linkage toward the fault slip plane, possibly indicating that faulting evolves from individual bands to a high-strain zone characterized by anastomosing deformation bands and culminating in the fault slip plane. Gas-permeability measurements show that individual deformation bands have an order of magnitude lower permeability than in the nearby sandstone matrix, and that the lowest permeability of fault zones defined by anastomosing deformation bands is in traverses nearly perpendicular to fault planes. It was found that the sandstone matrix in the fault zone has a lower permeability than individual deformation bands outside the fault zone, indicating that as a whole, the fault zone undergoes tectonic compaction and porosity collapse. The development of major normal faults was also accompanied by reactivation of bedding-perpendicular joints as small-displacement, simple-shear faults between the major faults.
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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.