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Hydrodynamic
Shape of Oil Stringers
Z. He, I. Lerche
A discussion is presented of the behavior of a thin oil stringer under
hydrodynamic conditions in a confined aquifer. The appropriate formulae for
describing the length of an oil stringer are presented, and the conditions of
derivation and application of the relevant results are spelled out. A novel
formula is provided to predict the maximum oil column that can be trapped by a
downdip flow of water in a stratigraphic trap.
We also present a discussion of the shape of an oil stringer in terms of the
stringer's width variation along the aquifer under different hydrodynamic and
stratigraphic conditions. To understand the influence
of various factors on the
shape of the oil stringer, several synthetic cases are simulated. The variables
include (1) lateral stratigraphic variation in terms of permeability changes,
(2) flow rate through the aquifer, (3) interfacial tension between oil and
water, (4) amount of oil in the stringer, (5) tilt angle of the aquifer, (6)
densities of oil and water, and (7) viscosity of water. The shape and stability
of the oil stringer can be predicted, thus providing useful constraints in
hydrocarbon migration assessments.
AAPG Search and Discovery Article #91022©1989 AAPG Annual Convention, April 23-26, 1989, San Antonio, Texas.