Development of Synthetic Layer Dip Adjacent to Normal Faults
David A. Ferrill, Alan P. Morris, Darrell W. Sims, Deborah J. Waiting, Shutaro Hasegawa, 2005. "Development of Synthetic Layer Dip Adjacent to Normal Faults", Faults, Fluid Flow, and Petroleum Traps, Rasoul Sorkhabi, Yoshihiro Tsuji
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Field analyses of normal faulting illustrate that synthetic layer dip associated with normal faults is a common feature of extensional fault systems. These synthetic dip panels are developed where layers on upthrown, downthrown, or both sides of a normal fault dip toward the downthrown side of the fault. Synthetic dip panels adjacent to normal faults should be expected at some scale in all normal fault systems. In addition to faults that developed in the strata with a regional dip, five fault-related mechanisms for the development of synthetic dip are faulted monocline (fault tip-line folding), antilistric fault bend, distributed shear, shear in relay zone of vertically and/or laterally segmented faults, and fault block impingement and lateral contraction. Development of synthetic dip accommodates a component of throw by tilting or folding, thereby reducing the offset or true displacement on the related normal faults. Fault block deformation is strongly dependent on the mechanisms that produce synthetic dip panels and may influence fault zone and fault block permeability. Depending on strat-igraphic and structural relationships, synthetic dip panels can produce a downthrown closure for hydrocarbon trapping, provide fluid migration and/or production communication pathways across faults, or produce barriers to fluid communication across 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.