USGS GOMSC Abstracts: Energy (plus alternate energy

Introduction: The terms “energy” and “minerals” usually bring to mind classic geologic studies – prospecting for oil and gas or gold or iron ore. These kinds of applied studies are remote from much of the work done in the Water or Biological Disciplines in the Gulf of Mexico. The recent USGS Science Strategy (USGS Circular 1309) challenges us to think more broadly than these traditional views of energy and minerals. A building block of the Science Strategy is that “the Earth behaves as a system in which oceans, atmosphere and land, and the living and non-living parts therein, are all connected.” (Steffen et al, 2005). Energy and minerals therefore need to be viewed in their larger environmental and global context.

Energy and minerals form one of the 6 primary goals of the Science Strategy, specifically that “the USGS energy and minerals resource research will be broadened to contribute more comprehensively to discourse and decisions about future natural resource security, environmental impacts of resource use, the economic vitality of the Nation, and management of natural resources on U.S. Department of the Interior, Federal and other lands.” (Circular 1309, p. 22). The USGS Gulf of Mexico symposium speaks to this broader and more comprehensive understanding of the role of energy and minerals in society. Of the four topics covered in this session, the first will look studies in the Gulf of Mexico to understand a potentially new and environmentally clean source of energy (gas hydrates); the second and third will cover the kinds of detailed framework studies and basic science that underlie the USGS assessment of oil and gas resources in onshore lands and State waters around the northern Gulf of Mexico for two geologic time periods: the Paleogene (~65 - ~24 million years ago) and the Neogene (~24 to ~2 million years ago); the final topic will look at how offshore aggregate resources are identified, characterized and utilized in the northern Gulf. These presentations will therefore deal with larger spatial (both two- and three-dimensional) and temporal scales than most of the other presentations at this meeting.

Deborah R. Hutchinson, Session Chair

Deborah R. Hutchinson, U.S. Geological Survey, Woods Hole Science Center, Woods Hole, Massachusetts

For more than a decade, the U.S. Geological Survey (USGS) has partnered with other entities to study the occurrence of gas hydrates in the Gulf of Mexico. Gas hydrates are ice-like forms of water and gas, usually methane, which occur in most continental margins of the world where appropriate temperature and pressure conditions exist, usually in the uppermost few hundred meters of sediments. In the northern Gulf of Mexico, studies were initially driven by concerns about hazards associated with penetrating gas hydrates during conventional oil and gas drilling in water depths >500 m where gas hydrates are typically stable. More recently, interest exists in gas hydrates as a potential unconventional energy resource. USGS research aims to define the geologic framework for gas hydrate occurrence, to quantify its occurrence, and to anticipate impacts of its dissociation. A major drilling program in 2005 in cooperation with the Department of Energy and the Joint Industry Project on Gas Hydrates in the Gulf of Mexico yielded strong evidence for a fault-controlled gas-hydrate accumulation in the minibasin province at about 1300 m water depth. A second exploratory drilling and logging campaign is planned in 2009 to better understand gas hydrate-bearing sands. Three areas will test alternative geological models and geophysical interpretations supporting the existence of potential high gas hydrate saturations in reservoir-quality sands. The three sites are near existing drill holes which provide geological and geophysical constraints in Alaminos Canyon (AC) lease block 818, Green Canyon (GC) 955, and Walker Ridge (WR) 313. In addition to testing geological methods and models used to infer the occurrence of gas hydrate in different settings in the northern Gulf of Mexico, the drilling results will be used to (a) calibrate geophysical models used to detect gas hydrate sands, map reservoir thicknesses, and estimate the degree of gas hydrate saturation; and (b) delineate potential locations for subsequent JIP drilling and sampling. The northern Gulf of Mexico gas hydrates research program focuses on quantifying the complex interactions of physical, chemical, geological, hydrological, and biological processes controlling the formation, occurrence, and dissociation of gas hydrate.

Contact Information: Deborah Hutchinson, U.S. Geological Survey, Woods Hole Science Center, 384 Woods Hole Rd, Woods Hole, MA 02543; phone: 508 457 2263; email: dhutchinson@usgs.gov

Peter D. Warwick, James L. Coleman, Paul C. Hackley, Daniel O. Hayba, Alexander W. Karlsen, Elisabeth L. Rowan, and Sharon M. Swanson

The U.S. Geological Survey (USGS) recently conducted an assessment of the technically recoverable undiscovered conventional oil and gas resources in Paleogene sediments underlying the U.S. Gulf of Mexico Coastal Plain and State waters. For purposes of the assessment, an Upper Jurassic-Cretaceous-Tertiary total petroleum system (TPS) was defined for the Gulf of Mexico basin. Paleogene strata were divided into the following stratigraphic study intervals: 1) Wilcox Group (including Midway Group and the basal Carrizo Sand of the Claiborne Group; Paleocene-Eocene); 2) Claiborne Group (Eocene); 3) Jackson and Vicksburg Groups (Eocene-Oligocene); and 4) Frio-Anahuac Formations (Oligocene). Based on a generalized structural and stratigraphic model, each assessed Paleogene stratigraphic interval was subdivided into an updip, stable shelf assessment unit (AU), a middip, expansion (extension) zone AU, and a downdip, slope and basin floor AU. A significant controlling factor for the location of the middip expansion zone AU is the location of underlying, stratigraphically older shelf margins. Using the geology-based assessment methodology, the USGS estimated mean a of 83.8 trillion cubic feet of undiscovered natural gas, a mean of 396 million barrels of undiscovered oil, and a mean of 3.1 billion barrels of undiscovered natural gas liquids in the assessed Paleogene strata. A significant portion of the undiscovered resources (53 % or 48.7 trillion cubic feet of gas) is estimated to occur in Paleogene slope and basin floor AUs. The Wilcox Slope and Basin Floor AU is estimated to hold about one third of the undiscovered hydrocarbon resources for the assessed intervals.

Contact Information: Peter Warwick, U.S. Geological Survey, Reston, VA 20192; phone: 703 648 6469; email: pwarwick@usgs.gov

A study of the geologic controls on undiscovered conventional oil and gas resources in Neogene strata of the onshore coastal plain and State waters of the Gulf Coast of the United States included evaluations of: (1) hydrocarbon source rocks (source-rock maturation, hydrocarbon generation and migration), (2) reservoir rocks (sequence stratigraphy and petrophysical properties), and (3) hydrocarbon traps (trap formation, timing, and seals). Principal factors controlling the distribution of both known and undiscovered fields include the distribution of paleo-drainage systems, pre-existing shelf margins, salt-related structures, minibasins, top of the overpressured zone, and climate-influenced eustatic sea level fluctuations. Components of the study included well-log cross sections, sequence stratigraphy, reservoir quality, existing production data, field-size distributions, analogs in offshore federal waters, source rock and thermal modeling, seismic interpretation, and structural modeling. Sequence stratigraphic interpretations, coupled with geophysical studies of overpressured reservoirs and geochemical studies of hydrocarbons and source rocks, indicate that known oil and gas fields reside primarily in highstand and transgressive systems tracts in clastic reservoirs deposited on continental shelves and shelf-margin deltas. In contrast, the majority of undiscovered conventional oil and gas resources are thought to reside in stratigraphically deeper clastic reservoirs that were deposited primarily in slope fans and basin-floor fans that formed as low-stand systems tracts in response to episodic fluctuations of sea level.

Contact Information: Russell F. Dubiel, U.S. Geological Survey, MS 939 Box 25046 DFC, Denver, CO 80225; phone: 303 236 1540; email: rdubiel@usgs.gov

1 U.S. Geological Survey, Florida Integrated Science Center, St. Petersburg, Florida
2 U.S. Geological Survey, Woods Hole Science Center, Woods Hole, Massachusetts
3 Department of Earth and Environmental Sciences, University of New Orleans, New Orleans, Louisiana

The wetlands, bays, and barrier islands of the northern Gulf of Mexico were formed through the interaction of modern coastal processes with a geologic framework that began with the erosion and redistribution of Pleistocene fluvial-deltaic deposits during Holocene sea-level rise. As a result, the Mississippi River Delta Plain and adjacent Mississippi-Alabama Shelf are a complex arrangement of progradational facies (prodelta, delta front, distributary channel, and marsh deposits), and transgressive facies (inlet channel fills, shoal deposits, and nearshore marine deposits).

Continued sea-level rise, increased storm impact, human alteration of the landscape, and a finite sediment-supply have resulted in a measurable net loss of land area in the Northern Gulf of Mexico over the past few centuries. To accommodate the loss, a key component of coastal management is shoreline renourishment through recovery and redistribution of suitable sediments from submerged and buried sand deposits. Understanding the stratigraphic architecture is necessary to identify subsurface features that can be classified into distinct units of predominant grain-size and texture for use in stabilization and management efforts. Over the past two decades the U.S. Geological Survey has been actively developing technologies to characterize this near-surface geology and understand the process-response of the coastal zone. Remote sensing through acoustic profiling, direct sampling through coring, and the management, synthesis and distribution of existing information is key to characterizing the shallow stratigraphy and indentifying spatially distinct deposits that are potential resources for shoreline and wetland restoration. This presentation is an overview of efforts by the Coastal and Marine Geology Program and it’s collaborators to provide information that can be utilized by coastal managers to protect the fragile ecosystem of the Northern Gulf of Mexico coastal zone.

Contact Information: James Flocks, U.S. Geological Survey, Florida Integrated Science Center, Coastal and Watershed Studies Team, 600 4th Street South, St. Petersburg, FL 33701; phone: 727-803-8747; email: jflocks@usgs.gov

3: Energy (plus alternate energy - Wind) and Mineral Resources