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Salt Dynamics: Simulation of Mushroom Caps on Salt and an Application in Barents Sea, Norway

YU, Z., and I. LERCHE, University of South Carolina, Columbia, SC

Various shapes of moving salt were simulated in response to gravity contrast and tectonic movement, and the deformations and fractures of the surrounding sediments were examined. The varying parameters in the model include the burial depth of the salt base, the overhang depth of the salt cap, the salt body's size, the salt speed, and the sediment depositional rate, as well as variation of the surrounding rock properties with depth, such as Lame constants, shearing strength, and internal friction. Mohr's criterion for failure was applied, allowing an indication of where fractures occur and their orientations.

Including the thermal effects of salt yields features favorable to hydrocarbon accumulation sites as shown by the simulations. Fractures near the vertical salt body and below the mushroom cap salt provide a continuous pathway for hydrocarbon migration due to the enhancement of permeability. The overhanging cap salt sheet provides a good chance of trap formation in terms of seals. The thermal effect of salt enhances the maturity of the source rocks. The observed faulting behaviors around salt are accounted for by primary and secondary features, as exhibited through the simulations.

In the study of Barents Sea, Norway, we find that the salt would most likely start to rise during the Early-Middle-Triassic and Jurassic when the sediment cover was 1700-2400 m. Depositional faulting was associated with salt diapir motion. The modeling also indicates that at least 1000 m of the salt cap was eroded based on the dip angles of sedimentary strata against the salt stock.

 

AAPG Search and Discovery Article #91006 © 1991 GCAGS and GC-SEPM Meeting, Houston, Texas, October 16-18, 1991 (2009)