Abstracts: 2005

Integrated Reservoir Studies & "Re-Exploration" in Mature Oil & Gas Fields: Brief Notes.
A program has been designed for evaluating mature oil/gas fields of Louisiana with the collaboration of independent producers. The ultimate goal will be to increase recovery efficiencies and to achieve optimum exploitation of remaining oil/gas resources. Aimed at reducing operational and production costs, the application of the appropriate technologies will be recommended. Also, case study examples will be generated using those fields in which the applied methodologies or technologies have proven to be successful. These examples will aid in the selection of future fields where similar studies may be performed.
With the cooperation of the operator and based on the availability of geological/geophysical, engineering and production data, an initial phase of data evaluation and integration can begin on each individually selected project. The tasks will include validation of the field data, which will be used for defining the principal objectives of the project. During a second phase, a model will be developed that describes the geological and the engineering characteristics of the reservoir. The tasks needed for carrying out each project may include geophysical, sedimentological, structural and stratigraphic mapping updates, cross section construction, analysis of reservoir engineering and production profiling. The results of these important, basic tasks will provide the appropriate reservoir description and characterization much needed for arriving at meaningful estimates of remaining reserves. Ultimately, this information will allow the integrated team to appraise the economic feasibility of continuing with a new development plan. The recommendations may include one or more of the following field projects: 1) 2D/3D seismic acquisition, 2) secondary recovery, 3) cased hole logging, 4) transient pressure testing, 5) installation of artificial lift, 6) workover/drilling operations.
Regarding technological challenges, the principal objective of this plan is the optimum production of the remaining hydrocarbons in any given field. Using such a mutidisciplinary team of experts, all the data must be integrated in order to obtain a thorough understanding of the field's reservoir conditions. Detailed characterization of the reservoirs will be required in order to take advantage of the use of modern technologies and fresh ideas for reducing future drilling risks and workover costs. Also, a successful development plan may include the reactivation of inactive wells.

Remaining Hydrocarbon Potential in Oligocene Reservoirs of Mature Fields, West Baton Rouge Parish, Louisiana.
West Baton Rouge parish contains several mature fields that produced from Oligocene reservoirs from the 1940s to the late 1980s. Port Allen and Lobdell fields, located approximately seven miles from Baton Rouge on the west side of the Mississippi River, are examples of such production. At present, all the wells in both fields are plugged and abandoned. Production was mostly oil with associated gas and minor amounts of condensate from the Oligocene Upper and Lower Frio formations.
Gas was not considered an important energy resource between 1950 and the 1980s, and because of low prices, many of the gas reservoirs that were tested in the Frio interval in these fields were immediately shut-in. Most of the associated gas produced with the oil was vented and minor quantities were used for gas lift. The calcareous sandstone reservoirs containing oil and gas are readily evident on the wireline logs and corroborated by test data. From the size of the fields (640 to 2000 acres), the well spacing, thickness of the reservoirs (10-20 ft), and the reported cumulative production, it is estimated that the remaining potential in these fields is approximately 4.0 billion cubic feet of gas (BCFG) and 3.0 million barrels of oil (MMBO). Most of the reserves are located in Port Allen Field. Based on such observations and because of today's relatively high oil and gas prices, reservoirs of such mature fields have become attractive economic targets when state of the art drilling and production technologies are applied.

Basin Analysis and Petroleum System Characterization and Modeling, Interior Salt Basins, Central and Eastern Gulf of Mexico.
The principal research effort for Year 2 of the project has been data compilation and the determination of the burial and thermal maturation histories of the North Louisiana Salt Basin and basin modeling and petroleum system identification. In the first nine (9) months of Year 2, the research focus was on the determination of the burial and thermal maturation histories, and during the remainder of the year the emphasis has basin modeling and petroleum system identification. Existing information on the North Louisiana Salt Basin has been evaluated, an electronic database has been developed, regional cross sections have been prepared, structure and isopach maps have been constructed, and burial history, thermal maturation history and hydrocarbon expulsion profiles have been prepared. Seismic data, cross sections, subsurface maps and related profiles have been used in evaluating the tectonic, depositional, burial and thermal maturation histories of the basin. Oil and gas reservoirs have been found to be associated with salt-supported anticlinal and domal features (salt pillows, turtle structures and piercement domes); with normal faulting associated with the northern basin margin and listric down-to-the-basin faults (state-line fault complex) and faulted salt features; and with combination structural and stratigraphic features (Sabine and Monroe Uplifts) and monoclinal features with lithologic variations. Petroleum reservoirs are mainly Upper Jurassic and Lower Cretaceous fluvial-deltaic sandstone facies and Lower Cretaceous and Upper Cretaceous shoreline, marine bar and shallow shelf sandstone facies. Cretaceous unconformities significantly contribute to the hydrocarbon trapping mechanism capacity in the North Louisiana Salt Basin. The chief petroleum source rock in this basin is Upper Jurassic Smackover lime mudstone beds. The generation of hydrocarbons from Smackover lime mudstone was initiated during the Early Cretaceous and continued into the Teritary. Hydrocarbon expulsion commenced during the Early Cretaceous and continued into the Tertiary with peak expulsion occurring mainly during the Late Cretaceous.

Petroleum Source Rocks of the Onshore Interior Salt Basins, North Central and Northeastern Gulf of Mexico.
Understanding the burial and thermal maturation histories of the strata in the onshore interior salt basins of the north central and northeastern Gulf of Mexico area is critical in petroleum source rock identification and characterization. The burial and thermal maturation histories of the strata in these basins and subbasins are consistent with the rift-related geohistory of these features. Source rock analysis and thermal maturity modeling indicate that lime mudstone of the Upper Jurassic Smackover Formation served as an effective regional petroleum source rock in the North Louisiana Salt Basin, Mississippi Interior Salt Basin, Manila Subbasin and Conecuh Subbasin. The Upper Cretaceous marine shale was an effective local petroleum source rock in the Mississippi Interior Salt Basin and a possible local source bed in the North Louisiana Salt Basin given the proper organic facies. Lower Cretaceous lime mudstone was an effective local petroleum source rock in the South Florida Basin, and these rocks were possible local source beds in the North Louisiana Salt Basin and Mississippi Interior Salt Basin given the proper organic facies. Uppermost Jurassic strata were effective source rocks in Mexico, and therefore, were possible source beds in the North Louisiana Salt Basin given the proper organic facies. Lower Tertiary shale and lignite have been reported to have been source beds in south Louisiana and southwestern Mississippi, but these beds have not been subjected to favorable burial and thermal maturation histories required for petroleum generation in the North Louisiana Salt Basin, Mississippi Interior Salt Basin, Manila Subbasin, and Conecuh Subbasin.