Simulation of Fault Patterns in Offshore Oil Fields of the Arabian Gulf

Darrell W. Sims¹, Alan P. Morris², David A. Ferrill¹, Danielle Y. Wyrick¹, Yoshihiko Tamura³, and Mamoru Takanashi^4
1 CNWRA, Southwest Research Institute, San Antonio, TX
² University of Texas San Antonio, San Antonio, TX
³ Japan Oil Development Company, Tokyo, Japan
⁴ Japan Oil, Gas and Metals National Corporation (JOGMEC), Japan

Diapirism of Hormuz salt has produced giant hydrocarbon traps in the Arabian Gulf, and influences fault and fracture patterns in overlying Mesozoic carbonate strata. Characterization of faulting in these fields is crucial for optimizing production. Variable fault geometry from dome to dome has led to the interpretation that domes reflect the reactivation of pre-Hormuz basement faults. We use physical analog models to characterize fault and fracture patterns interpreted from seismic data over two adjacent domes in offshore Abu Dhabi. Important variables are: (i) geometric shape of the dome, (ii) regional strain affecting the domes and (iii) rates and timing of regional strain versus dome uplift. Results indicate that both domes grew during NE-SW directed regional extension. Variations between the structures result from differences in the above variables, rather than reactivation of faults rooted in basement. Stratigraphic data indicate that both domes were most active between 90 and 80 Ma. The elliptical dome is characterized by a near-unimodal normal fault population consistent with the regional extension direction. The irregularly shaped dome has a variety of fault patterns from en echelon arrays, to rectilinear fault networks, to fanning radial patterns, with significant variability throughout the structure. Duplication of these fault patterns by analog modeling demonstrates that these fault populations reflect a combination of regional extension, crestal (outer arc) extension bending strain, and radial displacement associated with dome growth. Characteristics of the analog fault networks were used to inform simulations of sub-seismic scale fault populations for reservoir models.

AAPG Search and Discovery Article #90039©2005 AAPG Calgary, Alberta, June 16-19, 2005