1 Rock Deformation Research, Department of Earth Sciences, University of Leeds, Leeds LS2 9JT, UK
2 Japanese National Oil Corporation, 1-2- Hamada, Miharna-Ku, Chiba 261, Japan
Abstract: Fault Systems and Migration
Processes
Fault zones are usually considered to influence hydrocarbon
migration
in two ways. Either they are assumed to be open pathways
of high permeability or they are considered as barriers to the
flow. A third important possibility is introduced here. In this
case, inactive faults can allow hydrocarbons to migrate across them
when activity on an adjacent fault induces a pressure pulse that
can promote
migration
of hydrocarbons across the inactive fault. In
other words, the seal is viewed as a temporary barrier (or
retardation feature), which leaks when a fault related fluid
pressure event allows the entry pressure to be exceeded. This is in
contrast to the normal model where a seal leaks because of an
increase in hydrocarbon column, so that the buoyancy force exceeds
the entry pressure of the fault rock. Under the new model
hydrocarbons may migrate across the inactive fault zone for the
time period that the fluid pressure difference is above the
critical entry pressure during the earthquake cycle. Numerical
models of this process are presented to demonstrate the impact of
this mechanism and its role in filling traps with bounding sealed
faults.
AAPG Search and Discovery Article #90928©1999 AAPG Annual Convention, San Antonio, Texas