Gulf of Mexico Salt Structures and their Impact on Reservoir Quality—An Evaluation Methodology
Zehui (Tim) Huang¹, Ursula Edwards¹, Steve Carson¹, David Eickhoff², and Tobi Kosanke¹
¹Marathon Oil Corporation, 5555 San Felipe St., Houston, Texas 77056–2701
²Consultant, Houston, Texas
A major risk in exploring the Paleogene play in the Gulf of Mexico is reservoir quality. In addition to source provenance and sedimentary facies, temperature and pressure history are important controlling factors on sandstone porosity loss/preservation. Heat transfer in the Gulf of Mexico has been strongly influenced by the large contrast in thermal conductivity between salt and other sediments (mainly shale and silt/sandstone). Pressure transfer in the Gulf of Mexico is controlled by lithostratigraphic architecture, the geometry of base allochthonous salt, development of welded salt, and the deposition rate of the post-Miocene/Pliocene minibasins. As a result of complex evolution of salt emplacement/withdrawal and depositional history, there can be considerable variation in both present-day temperature/pressure, and thermal histories in various parts of the Gulf of Mexico.
Since the understanding of these factors is critical to successful reservoir quality prediction in the Paleogene play, a multi-disciplinary approach to integrate data and model geological processes was taken. Full 3D geocellular basin models were built, using geological maps and salt surfaces generated by geologists and geophysicists, and the evolution of basin geometries that includes the emplacement and movement of salt was reconstructed. The 3D basin model was calibrated to temperature and pressure measurements in exploration wells. For geological uncertainties, such as timing of mini-basin development and existence of salt stocks, different geological scenarios were modeled to assess the model’s sensitivity. Based on petrographic data and the reservoir temperature and pressure history from 3D basin model, numeric models were constructed to predict reservoir diagenetic history. We first calibrated the reservoir rock’s numeric model to offset well locations, and then modeled reservoir quality at the prospect locations using end-member reservoir rock composition and texture and temperature/ pressure histories of geological scenarios.
AAPG Search and Discovery Article #90158©2012 GCAGS and GC-SEPM 6nd Annual Convention, Austin, Texas, 21-24 October 2012