The Effects of Salt Bodies and Faults to In-situ Sub-salt Stress Field

Drilling sub-salt wells in deepwater Gulf of Mexico, the industry has constantly faced challenges of salt inclusions, rapid pore pressure changes, and lost wellbores. All of the geomechanical related issues require an understanding of the in-situ stress field, in terms of orientation and magnitude. Without any well controls, we typically assume the direction of the maximum horizontal stress to follow the strike of major faulting patterns in the Gulf of Mexico. Once well control is available, we commonly extrapolate linearly along the orientation of borehole breakout to the area of interest, without considering stress re-orientations due to salt movements and structural effects. To address these geomechanical questions, we build 3D Mechanical Earth Model (MEM) over the K2 development area in the Gulf of Mexico. The MEM describes the geological structure, how mechanical properties are distributed across the field, and 3D pore pressure field. A finite-element modeling technique was applied to examine the complex stress distribution and stress changes due to geological features such as salt bodies, faults, or reservoir depletion. The study reveals complex stress rotations due to salt placement and the presence of faults; however the sub-salt stress field is predicable.