David A. Ferrill¹, Alan P. Morris², Darrell W. Sims¹, Deborah Waiting¹, Shutaro Hasegawa³

(1) CNWRA, Southwest Research Institute, San Antonio, TX
(2) Division of Earth and Physical Sciences, University of Texas at San Antonio, San Antonio, TX
(3) Japan National Oil Corporation, Chiba, Japan

ABSTRACT: Development of synthetic layer dip adjacent to normal faults and implications for traps, barriers, and migration pathways

Field analyses of normal faulting in the Paradox Basin of southeastern Utah (vicinity of Moab, Utah) and northern Rio Grande Rift of New Mexico (vicinity of Albuquerque, New Mexico), considered with examples from new analog modeling and seismic reflection data, illustrate the importance of synthetic layer dip associated with normal faults. These synthetic dip panels are developed where layers on upthrown, downthrown, or both sides of a normal fault dip in the same direction as the fault. Synthetic dip panels adjacent to normal faults should be expected at some scale in all normal fault systems. In addition to faults developed in strata with a regional dip, six fault-related mechanisms for the development of synthetic dip are: antilistric fault bend, faulted monocline, distributed shear, shear in overlap between vertically or laterally segmented faults, fault block impingement and contraction, and differential subsidence by footwall or hanging wall collapse. 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 stratigraphic and structural relationships, synthetic dip panels can produce downthrown closure for hydrocarbon trapping, provide fluid migration and/or production communication pathways across faults, or produce barriers to fluid communication across faults.

AAPG Search and Discovery Article #90906©2001 AAPG Annual Convention, Denver, Colorado