Publication Date:
2004-11-01
Description:
In the northeastern Gulf of Mexico, Upper Jurassic Smackover inner ramp, shallow-water thrombolite buildups developed on paleotopographic features in the eastern part of the Mississippi Interior Salt basin and in the Manila and Conecuh subbasins. These thrombolites attained a thickness of 58 m (190 ft) and were present in an area of as much as 6.2 km2 (2.4 mi2). Although these buildups have been exploration targets for some 30 yr, new field discoveries continue to be made in this region. Thrombolites were best developed on a hard substrate during a rise in sea level under initial zero to low background sedimentation rates in low-energy and eurytopic paleoenvironments. Extensive microbial growth occurred in response to available accommodation space. The demise of the thrombolites corresponded to changes in the paleoenvironmental conditions associated with an overall regression of the sea. The keys to drilling successful wildcat wells in the thrombolite reservoir play are to (1) use three-dimensional seismic reflection technology to find paleohighs and to determine whether potential thrombolite reservoir facies occur on the crest and/or flanks of these features and are above the oil-water contact; (2) use the characteristics of thrombolite bioherms and reefs as observed in outcrop to develop a three-dimensional geologic model to reconstruct the growth of thrombolite buildups on paleohighs for improved targeting of the preferred dendroidal and chaotic thrombolite reservoir facies; and (3) use the evaporative pumping mechanism instead of the seepage reflux or mixing zone models as a means for assessing potential dolomitization of the thrombolite boundstone. Ernest A. Mancini is regional director of the Eastern Gulf Region of the Petroleum Technology Council, director of the Center for Sedimentary Basin Studies, and professor in petroleum geology in the Department of Geological Sciences at the University of Alabama. His research focus is on reservoir charactertization and modeling, petroleum systems, and the application of stratigraphic analysis to petroleum exploration.Juan Carlos Llinás obtained his B.A degree from the National University of Colombia in 1995 and his M.S. degree in 2003 from the University of Alabama, and he is currently working on his Ph.D. at the University of Alabama. He is studying Smackover oil fields associated with microbial reef buildups and genetically related depositional facies using well and seismic data. William Parcell is an assistant professor in the Department of Geology at Wichita State University. His research integrates sequence stratigraphy, microbial sedimentology, and soft-computing techniques in stratigraphic modeling. He received his B.S. degree (1994) from the University of the South (Sewanee, Tennessee), his M.S. degree (1997) from the University of Delaware, and his Ph.D. from the University of Alabama (2000). Marc Aurell received his B.A. degree (1985) and his Ph.D. (1990) in geology from Zaragoza University. He is currently working at Zaragoza University as a professor. Most of his work in the last 20 years has been concentrated on facies and sequence-stratigraphic analysis of the Mesozoic and Cenozoic carbonate platforms developed in the Iberian basin and in the Pyrenees (Spain). Beatriz Bádenas obtained her B.A. degree (1991) and her Ph.D. (1999) in geology at Zaragoza University, where she teaches courses in stratigraphy and sedimentology. Her major research interests include facies and sequential analysis of carbonate sediments in shallow platform settings. She is currently studying the application of high-resolution sequence stratigraphy and cyclostratigraphy to Upper Jurassic carbonate platform strata of the Iberian basin. Reinhold Leinfelder, paleontologist, carbonate sedimentologist, and basin analyst, specializes in Jurassic reef systems. He received his Diploma degree from the University of Munich in 1980 and his Ph.D. in 1985 and a postdoctoral habil degree in 1989 from the University of Mainz. He was an associate professor at the University of Stuttgart (1989–1998), and he is now a full professor at the University of Munich. Joe Benson is a professor in the Department of Geological Sciences and senior associate dean of the College of Arts and Sciences at the University of Alabama. His research interests lie in carbonate sedimentology and sedimentary petrology. He received a B.A. degree from the College of Wooster and an M.S. degree and a Ph.D. from the University of Cincinnati.
Print ISSN:
0149-1423
Electronic ISSN:
1943-2674
Topics:
Geosciences
Permalink