Stratigraphic Architectural Patterns and Hydrocarbon Plays in Salt Withdrawal Basins within Rift Settings- Examples from the Middle East

CSATO, ISTVAN and CHRISTOPHER KENDALL

Salt withdrawal basins are special sites of sediment deposition which form in response to salt evacuation, diapirism and subsequent collapse of overlying sedimentary beds. Using subsurface data, the specific architectural patterns related to salt movement have been investigated.

Diachronous movement of salt has been recognized as an essential factor in formation of salt withdrawal architectures. Diapir growth is marked by onlapping sediments at their flanks, while a pause in diapiric activity involves deposition of conformable layers. Different periods of growth and pause associated with salt diapir movement produce the various three-dimensional architectures of the salt evacuation zone. Architectures of salt withdrawal basins have been termed: symmetrical sinks when diapirs grow synchronously; wedge basins when on diapir onlaps another due to diachronous growth; and in alternate evacuation basins when the relative rate of diapir activity changes with time.

This classification of salt withdrawal basins can be used to build play concepts for exploration. Fan-aprons formed in the pinchout zones of wedge basins and interfingering zones of alternate evacuation basins may be important exploration targets.

Integrated computer modeling of salt movement, sedimentation, fluid and heat flow has revealed that salt movement has a marked effect on the thermal and fluid flow processes. Salt focuses heat from below diapirs into the overlying area masking thermal maturation around diapirs. Rapid sedimentation in the collapse zones induces intense compaction driven flow towards the flanks of salt withdrawal basins. The diachronous nature of diapirism and the consequent architectural patterns determine the timing of heat and fluid flow processes. 

AAPG Search and Discovery Article #91021©1997 AAPG Annual Convention, Dallas, Texas.