Brian J. Harder

Regional Chronostratigraphic and Depositional Hydrocarbon Trends in Offshore Louisiana State Waters

ABSTRACT Successful exploration for hydrocarbons in the Northern Gulf of Mexico basin requires a systematic understanding of hydrocarbon producing trends, sand body geometries and the geologic, engineering and reservoir parameters of the producing sands. This study forms part of the Offshore Atlas project in progress at the University of Texas at Austin, Bureau of Economic Geology, Texas, in cooperation with the U.S. Department of Interior, Minerals Management Service, and the Geological Survey of Alabama, and is aimed at achieving this goal. In this study, 26 chronozones were grouped into 12 sub-groups. The chronozones were defined on the basis of the benthic foraminiferal biostratigraphic zones and were correlated across the Gulf using well and seismic data and were projected from the Federal offshore into the State waters. The chronozones on each well log in the 22 cross sections constructed from West Cameron area eastward to the Chandeleur Sound, Breton Sound and Main Pass areas, were subdivided as applicable into four depositional groups consisting of aggradational, progradational, transgressive and submarine fan facies based primarily on SP log shapes. In the Louisiana State waters there are 92 fields containing 685 reservoirs. This includes 214 oil, 347 gas, 33 condensate and 91 combination type reservoirs. Total combined cumulative production is 1,44l,091,263 barrels of oil, 117,641,457 barrels of condensate and 11,802,821,997 thousand cubic feet of gas. Total assigned production (1977-1995) shows the progradational facies to be most productive yielding 51.69% oil, 93.84% condensate, and 77.47% gas. The aggradational facies sands produced 46.98% oil, 1.70% condensate and 15.76% gas. The submarine fan facies yielded 1.21% oil, 4.45% condensate, and 6.74% gas. Production from the transgressive facies sands was less than 0.2% of the total assigned production of oil, gas and condensate.

MISSING WELL LOCATIONS: AN ENVIRONMENTAL RISK ASSESSMENT AND REGULATORY PROBLEM FOR LOUISIANA

The focus of this project is to examine 48,953 well permits and create a digital database of the locations from various public records. The Basin Research Institute (BRI), Louisiana State University, in cooperation with the Louisiana Department of Natural Resources, Office of Conservation, will obtain paper records of each well permit. Using various purchased commercial oil and gas, mapping and surveying software and data management programs, (Geographix, Arcview, AutoCad Map and ProCogo) a digital latitude and longitude for each of the missing wells is being obtained. Current status of the project is that all 48,953 permits have been examined. Of that total 48,559 have been completed and digital locations have been obtained, 270 need additional information to be completed, and no determination is possible for 124 well permits. Upon completion each permit is placed in one of the following databases determined by status-Active Producers (11,450) of which 11,444 are complete or 99.99%, Shut-in Producers (2,305) of which 2,300 are complete or 99.78%, Abandoned Previous Producer (17,513) of which 17,332 are complete or 98.96%, Abandoned Dry (9,029) of which 8,883 are complete or 98.38%, Permit Expired (7,083) of which 7,040 are complete or 99.39%, and Miscellaneous Wells (1,573) of which 1,560 are complete or 99.17%. The databases will be available in both digital and hard copy format. The completed database will help Louisiana implement risk-based regulatory policies and streamline existing policies, and provide industry and the public with access to information for all phases of the oil and gas business.

ABSTRACT: Occurrence and Structural Control of Hydrocarbon Production Associated with the Baton Rouge Fault Zone, Louisiana

The Baton Rouge fault forms part of a regional east-west trending, down-to-the-basin contemporaneous fault zone known as the Baton Rouge - Tepetate Fault System. The Baton Rouge fault zone traverses the eastern to central portions of south Louisiana; the Tepetate fault zone traverses the western portion of south Louisiana. Together, these fault zones form a continuous fault system across the state that exhibits syndepositional growth in late Eocene to Oligocene time. Pronounced surface expression of the Baton Rouge fault indicates recent renewed structural fault movement. Several hydrocarbon productive fields occur along the Baton Rouge fault trend. Most of the fields are small rollover structures downthrown to the fault, however, some large rollover features and anticlinal structures have produced significant amounts of hydrocarbons. Stratigraphically trapped accumulations of hydrocarbons near, but downdip, of the Baton Rouge fault indicates some hydrocarbons migrated updip along sedimentary layers into structures along the Baton Rouge fault. However, the hydrocarbon bearing rollover and anticlinal structures could have been charged by hydrocarbon migration updip toward the fault, hydrocarbon migration along the fault as a conduit, or both. Recent studies of freshwater aquifers adjacent to the Baton Rouge fault indicate the fault is a barrier to freshwater flow, but that increased freshwater pumpage has moderated its behavior as a barrier. The fault is also recently inferred to act as a conduit for saltwater intrusion; it may play a similar dual role in hydrocarbon migration.