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Salt
Diapir Growth and Sedimentation:
an Example from Cote Blanche Island Field, Louisiana
KOLARSKY, RADIM A.
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.