Serial Cross-Section Trishear Modeling: Reconstructing 3-D Kinematic Evolution of the Perdido Fold Belt

He, Dian; Brandenburg, John Paul

Fault interpretations in seismic data wipe-out zones are commonly non-unique, particularly in contractional structures. This consequently leads to increased risk in hydrocarbon exploration. Trishear modeling provides a quantitative method to constrain the geometries and locations of faults in wipe-out zones using the data set of horizons interpreted from well-imaged areas. Here, we examine a pair of opposing fault propagation folds in the Perdido fold belt, northwest Gulf of Mexico. The two opposing fault zones are poorly imaged in seismic data. However, some geometric observations such as footwall thickening and well imaged hanging wall anticlines enable us to constrain the fault geometries using an optimized kinematic trishear model. The structure is well represented by two opposing trishear models with curved faults. Best-fit models are determined using global optimization. Finite strains are estimated by implementing strain markers (small circles) in the double trishear models. We modeled 8 parallel cross sections that are perpendicular to the strike of the structure. Each cross section is modeled independently, but some of the parameters (e.g., initial fault tips, trishear apical angles, and P/S ratio, etc.) are constrained in fixed small ranges for all cross sections in order to obtain consistent geometries and kinematics in 3-D. The results show that the modeled horizons in the best-fit models match the interpreted horizons very well for all 8 cross sections. 3-D fault surfaces and modeled horizons are generated by interpolating the best-fit models of all 8 cross sections. The 3-D model constrains the starting tip position and slip on both faults, and reveals that both faults show relatively high slips at the two ends of the structure and low slips in the middle. Shortening strains produced by thrust faulting are from 20% to 40%, concentrated on the areas adjacent to the two faults and ahead of the final fault tips. These high strain zones may correspond to degraded reservoir performance.

AAPG Search and Discovery Article #90163©2013AAPG 2013 Annual Convention and Exhibition, Pittsburgh, Pennsylvania, May 19-22, 2013