PREDICTING RESERVOIR PRESENCE IN THE DEEP-DOWNDIP TERTIARY ALONG THE TEXAS - LOUISIANA STATE LINE AREA OF THE GULF OF MEXICO BASIN

The Gulf of Mexico Basin is a prolific hydrocarbon-producing province in the U.S. Significant undiscovered oil and gas resources in conventional and continuous reservoirs potentially remain in its onshore and State waters area. Recent discoveries in near-offshore areas of Louisiana demonstrate industry interest in deep Tertiary strata. Results of the 2007 USGS National Oil and Gas Assessment (NOGA) indicated that the greatest undiscovered gas resources sit in slope and basin floor assessment units (AUs), located primarily in the deep-downdip strata of the onshore and State waters. The Paleocene-Eocene Wilcox Group and Lower Miocene slope and basin floor AUs had the highest estimated means for undiscovered natural gas of the areas assessed. Nevertheless, due to significant AU depths, well and production data were sparse or completely lacking, and efforts to develop a total petroleum system framework including regional stratigraphy, reservoir quality, and thermal maturity were hampered.

The goals of the current NOGA project include updating the 2007 geologic framework for the Tertiary and developing a model for deep-downdip strata focusing on selected areas of the central Gulf Coast. Since the 2007 assessment, we have acquired new seismic lines, well logs, and biostratigraphic data for limited onshore and State waters areas. This study focuses on predicting reservoir presence in the deep downdip Tertiary, and specifically on interpretation of a regional seismic line along the Texas - Louisiana State line and supported by regional well log formation picks when available. Interpretation focuses on recognizing three AU models developed for onshore and State waters areas, including an updip AU consisting of thin reservoir intervals deposited in mostly highstand and transgressive systems tracts with minimal to no fault block expansion, an intermediate dip AU consisting of thin to thick reservoir intervals deposited in mostly highstand and lowstand systems tracts with major fault block expansion, and a downdip AU consisting of thin to moderate reservoir intervals deposited in mostly distal highstand and lowstand systems tracts with minimal to no fault block expansion. Ultimately USGS assessment of significant hydrocarbon resources is critical to domestic energy supply and national energy policy.