Subsalt exploration potential, Walker Ridge and Keathley Canyon areas, deep water Gulf of Mexico

Liro, Louis, Mary Kadri, Peter Montecchi, Nathan Weber, Steve O’Hara, Mo Etemadi, Susan Lock Williams, and Mary Cubanski, Veritas Exploration Services

Abstract

We describe the exploration plays associated with the salt nappe, canopy, and massif systems of Walker Ridge and Keathley Canyon areas in the deepwater Gulf of Mexico. 3D depth imaging of seismic allows definition of the salt emplacement and deformation history, and the associated subsalt trap styles.

Salt emplacement in the region follows a simple history: relatively evenly spaced inferred paleo salt stocks have fed salt canopy, nappe, and massif systems. In this region, salt is emanating directly from the Jurassic Louann layer. Mapping of the salt allows division of the present–day salt masses into discrete salt ‘cells’. Emplacement and extrusion occurred in a series of low-angle and high-angle surfaces, dominantly lateral in the canopy and nappe systems, and dominantly vertical in the massif system.

Subsalt structural traps are divided into three major types, from deepest to shallowest: (1) anticlinal salt–cored folds of Mesozoic and Paleogene strata; (2) structural inversions ("turtles") of Paleogene and Neogene strata; and (3) counter regional dip and truncation of Neogene strata against the vertical salt emplacement to lateral salt emplacement transition. Mesozoic anticlines are located basinward of a regional low in the MCSB. These structures are fully detached from the superjacent lateral salt masses. These structures are on–trend with recent significant discoveries in shallower waters. Structural inversions are associated with paleo salt stocks. Salt truncation traps are shallower and offset from the crest of the inversion structures. Definition of salt ‘cells’ allows an understanding of the development of each structure in the trend, which may imply subtle differences in structural timing and trap competency prior to hydrocarbon emplacement.