--> ABSTRACT: Migration Pathways, the Principle of Least Work, and Near-Vertical, Low-Throw Normal Faults, by Joel S. Watkins, Yuqian Li, and Carrie L. Decker; #90906(2001)

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Joel S. Watkins1, Yuqian Li1, Carrie L. Decker1

(1) Texas A&M University, College Station, TX

ABSTRACT: Migration Pathways, the Principle of Least Work, and Near-Vertical, Low-Throw Normal Faults

Conventional wisdom says that hydrocarbons enter a growth fault near the "foot" of the fault then migrate upward until they intersect reservoirs. Theoretical considerations, computer simulations and reservoir studies suggest this model is often incorrect.

Fluids follow the path of least resistance. For listric normal faults, pressure perpendicular to the lower, near-horizontal portion of the fault roughly equals overburden pressure. Pressure perpendicular to near-vertical faults is significantly less, thereby favoring migration along these faults. At all levels, thickness and capillary pressure across large-throw faults are generally greater than pressure perpendicular to small-throw, near-vertical faults. Thus, small-throw vertical faults will usually be the path of least resistance.

Studies of reservoir structure, physical properties, hydrocarbon geochemistry and computer simulations of hydrocarbon migration in Ship Shoal 274/293, a South Texas field and in the deepwater Gulf of Mexico data confirm the effectiveness of small-throw near-vertical faults as migration pathways. In SS 274/293, antithetic faults are the main pathways. In South Texas, a combination of transfer, compaction and antithetic faults form pathways whereas GOM compaction faults are the pathways.

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