Depositional Systems and Associated Facies Characteristics of the Deep -Water Paleocene to Miocene Gulf of Mexico: An Example of Unconfined and Confined Flows
Speaker: Dr. John B. Wagner
Chief Geologist, Nexen Petroleum
Biography:
Dr. Wagner received both his B.S. and M.S. degrees in geology from Louisiana State University in Baton Rouge and his Ph.D. in geology at The University of Texas at Dallas. He joined Nexen Petroleum in December of 2000 as Sedimentologist for Deep-water Exploration and Development and is currently Chief Geologist for Nexen Petroleum U.S.A. Prior to joining the petroleum industry with Mobil Research & Development in 1987, his work ranged from field geologist in Alaska, to manager of a seismic crew, to coastal geologist for the Louisiana Geological Survey Coastal Geology Program. John was a scientist on board the 1985 USGS/IOS GLORIA survey of the deep-water Mississippi Fan, Gulf of Mexico which was a significant expedition in regards to our understanding of deep-water submarine fan systems. He is a member of both the AAPG and SEPM and has served on Program Committees for the Gulf Coast Section Society of Economic Paleontologists and Mineralogists (GCSSEPM) Foundation Annual Research Conferences and was the 2009 President of GCSSEPM. In addition to his role as Chief Geologist for Nexen Petroleum U.S.A., John is currently a Research Associate Professor at Southern Methodist University in Dallas, Texas, where he serves as graduate advisor and teaches graduate courses in the field of sedimentology and has published over 30 papers and abstracts. His work travels have taken him from the rivers and streams of Sakhalin Island Russia, to the coast of Vietnam, to the jungles and mountains of Bolivia and Argentina. His primary research interests are focused on siliciclastic depositional systems both modern and ancient, sandstone sedimentology, reservoir architecture, depositional systems analysis, and understanding the various allocyclic and autocyclic controls that influence deposition.
Abstract:
The seaward expression of the Lower Tertiary Wilcox trend represents an excellent example of an extremely high-depositional rate deep-water depositional system. Core data from several Wilcox wells indicate deposition associated with an organized deep-water fan system dominated by gravity-flow deposits. Facies range from amalgamated sheet facies to low-relief channelized lobes (sheets) producing an overall tabular reservoir architecture of high correlation lengths over fairly large areas. Primary porosity/permeability development is important for preservation of good reservoir quality at these burial depths and pressures within the overall evaluation of these Paleocene to Eocene age rocks.
Recent drilling of a seismically defined Miocene channel/levee system in the deep-water Gulf of Mexico has provided new insight into their architectural development and associated reservoir distribution. Both asymmetry of channel morphology and degree of channel sinuosity (straight vs. curve) lend to varying distributions of net/gross ratios of sand in relation to proximity to channel margin. Early development of channel systems favors deposition within channel bases and is attributed to weaker confinement of sustained flow deposition. Also at this time, overbank deposition has more attributes of crevasse splay (high net/gross) deposition rather than true levee facies typically dominated by highly ripple laminated facies. As channel continues to aggrade, system becomes more confined with only the larger flows contributing to the levee/overbank environment with channel axis acting as a zone of bypass and only passively infilling during waning flow and abandonment. This abandonment phase is attributed to updip avulsion and results in rapid shale deposition within channel and overbank setting creating a master top seal over the entire channel/levee complex.