Interaction Between
Salt Diapir Growth and Sedimentation: an Example from Côte Blanche Island
Field, Louisiana
Radim A. Kolarsky, Texaco Exploration and Production
Inc.
- First presented at the Annual Convention of the American
Association of Petroleum Geologists (AAPG) in Dallas, March 1997
- Also presented at
- The
Southeastern Geophysical Society in New Orleans (August 1997)
- The University of Texas Institute for Geophysics (UTIG) in
Austin (March 1997)
- The Gulf Coast Association of Geological Societies (GCAGC)
in New Orleans (September 1997)
Abstract
This
paper presents a detailed study of the evolution of a salt diapir from the
Late Oligocene to Present based on 3D seismic, well logs and biostratigraphic
information.
There is a notable lack of faulting
associated with the diapir. The only faults are a large counter-regional normal
fault dissecting the diapir and a small number of synthetic and antithetic
faults. This observation is in striking contrast with older interpretations
of this field since its discovery in 1948. Those proposed a large number of
radial faults extending outward from the diapir; in concert with the thinking
of the time that all diapirs have to actively breach their overburden on their
way to the surface, causing intense faulting. This study presents evidence
that a diapir can reach the surface and enter a mature state without causing
extensive faulting. This study suggests that the faults observed in the field
are coeval with diapirism, but are related to deeper, lateral withdrawal of
salt that is feeding the growing diapir. The faults are not caused by emplacement,
but are related to diapir growth.
This re-interpretation of the field
changes the reservoir interpretation. Missing section observed in wells high
on structure does not represent normal faults, but rather unconformities caused
by differential salt uplift. Individual reservoirs are not constrained laterally
by faulting. Rather, complexities in their behavior are due to depositional
facies variations. Most of the reservoirs are constrained updip by either
salt or uplift-induced onlap. The new interpretation of the field has led
to an intensive workover and development drilling program that has revitalized
this mature field.
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