Controls on Carbonate Play Development in the Paleozoic of West Texas and New Mexico
Jeffrey J. Dravis
A carbonate play is the juxtaposition of a limestone or dolostone reservoir facies sealed by a carbonate or shale facies, with its hydrocarbons sourced from a nearby organic-rich carbonate or siliciclastic mudstone. Understanding the controls on carbonate play type distribution and geometry is critical to more successful exploration in any basin. As such, delineating potential carbonate plays from seismic or wireline logs requires a sound understanding of the depositional and diagenetic controls that create the reservoir facies, but it must be obtained within the context of geological age and physiographic setting. Specifically, one must appreciate the environmental controls on carbonate facies development, and potential pathways for diagenesis and porosity evolution. For this reason, strategies employed in the search for sandstone or mudstone reservoirs never work for carbonate sequences, including application of sequence stratigraphic models that assume sea level changes overridingly control carbonate facies and sequence evolution.
This one-day short course reviews the key controls on carbonate facies occurrence and distribution, and demonstrates the strong influence of physiographic setting, both at the global and local scale. Because most carbonate reservoirs were developed within tropical or subtropical settings, paleotrade winds often were a major influence on their occurrence and distribution. In addition, the key controls influencing limestone diagenesis and dolomitization are reviewed, but with focused emphasis on how porosity and permeability evolve. The diagenesis discussion also will stress how to resolve the relative timing of secondary porosity development in these carbonates, which is key to exploiting regional porosity trends. The diagenesis discussion will further evaluate the role that deep-seated faulting often plays in carbonate diagenesis and development of reservoir quality, as well as hydrocarbon entrapment.
This short course culminates with a discussion relating carbonate play type occurrence, geometry and distribution to geological age, but in the context of physiographic setting (platform versus ramp). This approach will be supported by case studies from different basins, and then applied to Paleozoic play type examples from West Texas and New Mexico.
- Introductory Comments (Distinctive Aspects of Carbonates; Constituents and Textures; Classification Schemes)
- Limestone Diagenesis and Porosity Evolution: Controls, Processes and Products, and Timing
- Dolomitization: Popular Models; Porosity Evolution and Timing Relationships.
- Carbonate Facies: Controls and Attributes; Review of Carbonate Facies Models
- Established (Rock-Based) Principles of Carbonate Depositional Sequences and Cyclicity
- Classification of Carbonate Play Types and Analogs, with Applications to the Paleozoic of West Texas and New Mexico
Pioneer Drive Baptist Church
701 S. Pioneer Dr.
Abilene, TX 79605
Texas Christian University
Kelly Alumni Center
2820 Stadium Dr.,
Ft Worth, TX 76129
Jeffrey J. Dravis
Jeff Dravis is a consultant in Carbonate Sedimentology and Marine Geology, primarily focused on searching for oil and gas deposits, or helping to develop them once they are discovered.
Jeff's academic training in geology was purposely designed to gain experience with both modern environments and processes and ancient sedimentary sequences. He received his BS degree in Geology from St. Mary's University San Antonio, Texas, in 1971. He received a Master of Science degree in Marine Geology from the University of Miami's Rosenstiel School of Marine and Atmospheric Sciences in 1977. Dr. Harold R. Wanless was his thesis supervisor. His thesis was entitled "Holocene Sedimentary Depositional Environments on Eleuthera Bank, Bahamas."
In the summer of 1976, Jeff entered Rice University to begin work under Dr. James Lee Wilson on ancient deep-water carbonates. In 1980, he was awarded a Ph D from Rice University, Houston, Texas. His dissertation was entitled " Sedimentology and Diagenesis of the Upper Cretaceous Austin Chalk Formation, South Texas and Northern Mexico."
In 1978, Jeff began his professional career with Exxon Production Research Company in Houston where he conducted applied research on carbonate facies, diagenesis and porosity evolution, and headed up Exxon's worldwide training efforts in carbonates.
In 1986, he started his own consulting practice in Houston. In 1988, he founded Dravis Interests, Inc. to provide technical expertise and training in applied carbonate petroleum geology to the oil and gas industry. In May of 2000, Dravis Geological Services was created to handle all technical consulting projects; Dravis Interests, Inc. is now responsible for all training activities. Jeff has been involved in technical projects worldwide, working in sequences ranging in age from Cambrian to Tertiary. He has presented over 183 applied seminars. His clients are domestic and foreign oil companies, both majors and independents.
Jeff has been an adjunct Professor of Geology at both Rice University and the University of Miami, Florida, since 1987. He teaches at both schools, takes students into the field, and periodically serves on thesis committees.