W.H. Hart¹, M.L Albertin¹

(1) BP Exploration, Houston, TX

ABSTRACT: Subsalt Trap Archetype Classification: A Diagnostic Tool for Predicting and Prioritizing Gulf of Mexico Subsalt Traps

Gulf of Mexico (GOM) 3D seismic datasets, subsalt well results, and kinematic models were integrated into a calibrated methodology for assessing subsalt trap geometry and prospectivity. Subsalt traps can be grouped into genetically distinct archetype families, a classification that reveals the predictable influence of common salt styles on specific trap attributes. The archetypes are qualitatively ranked for exploration value according to their inherent trap risks, forming a basis for evaluating subsalt prospectivity even in areas obscured by overlying salt.

Across the spectrum of GOM subsalt trap styles, steeply dipping strata and sinuous subsalt "ribbon closures" pose exploration risks. Inversion, counter-rotation, and lateral flexure of subsalt strata can dramatically improve subsalt prospectivity. Structural elements that enhance or destroy subsalt trap viability evolve with the deformation of ubiquitous, deeper allochthonous and autochthonous salt. The concept of "vertical linkage" describes this systematic relationship between deep salt movement and the magnitude and mode of subsalt trap deformation. Kinematic models and seismic analogs demonstrate that vertical linkage is, in turn, dictated by local salt root geometry. Three kinematically distinct root types are recognized: 1) allochthonous ramping back-roots, 2) allochthonous ramping fore-roots, and 3) autochthonous roots. End member trap archetypes are grouped according to root type, defining distinct subsalt play families with differing trap prospectivity. Recognition of root style allows the prediction of critical subsalt trap attributes that may remain unresolved on seismic datasets

AAPG Search and Discovery Article #90906©2001 AAPG Annual Convention, Denver, Colorado