Yann Lagalaye1,
Eric Chaput1,
Thierry Rives1
(1) Elf Exploration Production, Pau, France
Abstract: Segmented faults: Dynamic behavior in well
test
simulations
Well
testing is commonly used to
infer the presence of lateral barriers like sealing faults. Indeed, in
classical
well
test interpretations, faults are modeled as simple homogeneous
linear reduction of transmissibility. Nevertheless, geological observations
indicate faults are very often segmented leaving a path to flow. The
availability of
well
testing to discriminate different
types
of faults has been
investigated. Four synthetic cases have been modeled with a dynamic flow
simulator: infinite continuous sealing and partially sealing faults, finite
sealing fault and segmented fault. The
well
test signatures are very similar in
all cases and differentiation on a
well
test interpretation is difficult. When
the reduction of transmissibility due to partially sealing fault is high
(inferior to 0.001) or when the relay zone of a segmented fault is far from the
well
, the derivative signature is similar to the sealing fault case. Small
reduction of transmissibility for partially sealing faults or short distance
between
well
location and relay zone of a segmented fault induce differences of
the derivative compared to the sealing fault case. In both cases, a Linear Composite
three Zones model fit
well
with the simulation curves. Meanwhile, the
calculated distance to the fault plane, or to other limits, will be wrong if
the segmented fault is not identified. Consequences for production strategies
could be dramatic in particular for multiphase reservoirs, where the
possibility of very localized flow within relay zones can lead to gas or water
breakthrough. Case studies illustrate possible misinterpretation of
well
test
without geological input.
AAPG Search and Discovery Article #90914©2000 AAPG Annual Convention, New Orleans, Louisiana