Deep Opportunities in the South Louisiana
Fangjian 'Jack' Xue1, Kim Hemsley1, David Chi2, and Dan Shan1
1Schlumberger, 1325 S. Dairy Ashford, Houston, Texas 77077
2El Paso Corporation, 1001 Louisiana Street, Houston, Texas 77002
The South Louisiana land/water transition zone, covers an area of about 18,000 square miles (Figure 1). The region has nearly one hundred years of production history. Daily production has declined from 10 BCFG and 1 MMBO of oil at its peak time in 1972 to 2 BCFG and 0.2 MMBO today. About 90% of the wells in the study area have been abandoned and approximately 50% of its fields are inactive. Most of the major oil companies have left this area to pursue deep-water opportunities in the nearby Gulf of Mexico. This hydrocarbon province has all the signs of a mature.
However, during the last decade, deep wells drilled below or adjacent to existing fields have resulted in some significant deep discoveries. Among them are some newly found deeper reservoirs that have increased the production rate hundreds of fold and added reserves in excess of hundreds of BCFG to individual field. These new discoveries have generated tremendous returns for the operators and significantly increased the value of their assets. Some depleted fields have been rejuvenated with the deep discoveries and once again generate tremendous income for their operators. These new discoveries have caused the industry to re-evaluate at the potential of the deep opportunities in south Louisiana.
To gain a better understanding of the deep prospectivity of the South Louisiana Transition Zone, regional studies of the Miocene production trends, along with high-quality deep-targeted 3D seismic data and relevant publications from the industry and academics have been combined with proprietary analysis and interpretation techniques. The study indicated that the structural and stratigraphic framework of the area is characterized by a regional detachment surface at about 5.2 seconds (~22,000 feet) under sand-rich Tertiary sediments. Above this surface, syndepositional salt movement and associated growth fault systems have created extensive structural deformation. The lowstand system tracts dominate the deep section below 12,000 feet of depth. The complex evolution history of the interaction between salt tectonics and slope sedimentation resulted in stacked reservoirs, high-density traps, multiple-play types, and abundant migration pathways in the deep section. The excellent geological conditions, together with relatively high pressure, created numerous high-productive deep targets through most of the study area.
With more than 70,000 wells drilled, this area seems to be extensively drilled and developed. But the deep section has not been properly evaluated More than 95% of the wells have been drilled without the benefit of 3D seismic data and less than 20% of the wells have penetrated deeper than 12,000 feet., Especially for the deeper section below 15,000 feet, the reservoirs typically consist of lower-slope basin-floor fan sands. These deep-plays are analogous in many aspects to the stratigraphically younger deep-water plays in the present-day Gulf of Mexico. But only less than 10% of the wells have penetrated deeper than 15,000 feet.
This deep frontier province lies below existing infrastructure. It represents a unique opportunity for development of highly productive reservoirs in an onshore environment that has similar production capabilities of the deep-water plays but without the high cost and hazards associated with deep-water developments. With available new technology, knowledge and data, the under-explored deep plays in south Louisiana provide innumerable and more economic targets for oil and gas exploration and production.
AAPG Search and Discovery Article #90080©2005 GCAGS 55th Annual Convention, New Orleans, Louisiana