Lacustrine Basin Exploration

(AAPG, see registration information)

Location: Beginning and ending in Salt Lake City, UT with field localities in and around Salt Lake City, UT and Rock Springs, WY.  

Who Should Attend: Geologists, geophysicists, reservoir engineers, managers and anyone working with lacustrine petroleum source rocks, oil shale, lacustrine or fluvial reservoirs, and nonmarine basin stratigraphy.

Objectives:

Lake basins contain some of the most prolific hydrocarbon resources in the world, including super-giant fields in the South Atlantic, Caspian Sea, and in China and SE Asia.  Even larger resources are associated with oil shale deposits in the western U.S.  Despite their growing importance, the petroleum geology of lake basins has received far less attention than marine basins.  This course therefore aims at developing an understanding of the unique aspects of lacustrine source rocks, reservoirs, and basin evolution that will aid future exploration and development efforts.  We will do so using the world-famous record of Quaternary Lake Bonneville to gain insight on controls on lacustrine deposition, and the similarly famous Eocene Green River Formation to examine the preserved deposits of a well-exposed ancient lake basin.

Specific learnings to be emphasized in this field seminar include:

  • Genetic controls on lake basin evolution
  • Recognition of the three principal lacustrine facies associations, based on surface, subsurface, or geochemical data. 
  • Source rock characteristics associated with the three facies associations
  • Carbonate reservoir characteristics in lacustrine basins
  • Clastic reservoir (fluvial and deltaic) characteristics in lacustrine basins.
  • Lacustrine stratal geometries and distribution patterns of source rock and reservoir facies.

Content:

The Lacustrine Basin Exploration field seminar has been developed on a number of classic field localities in Utah and Wyoming.  Localities outside of Salt Lake City, UT will be used to illustrate key geomorphic and stratigraphic features of pluvial lake Bonneville (Gilbert deltas and other shoreline features) and modern Great Salt Lake (playa-lake environments).  These “actualistic” observations will help provide context for understanding the deposits of Eocene Lake Gosiute in Wyoming, where recent radioisotopic work has established a chronostratigrahic framework of unprecedented resolution.  There we will focus on basin margin to basin center transects of the Bridger and Washakie basins, based on excellent exposures of fine-grained lacustrine carbonate mudstone facies and alluvial to deltaic sandstone facies. Participants will build two basin-scale cross sections of Lake Gosiute strata by recording their own guided outcrop observations on the chrono-stratigraphic framework provided.

At the outcrop scale, we will examine the heterogeneous reservoir architecture of alluvial, deltaic, and lake-marginal carbonate deposits associated with overfilled, balanced-fill, and underfilled lacustrine basins.  These deposits range in style from classic Gilbert deltas to more “dryland” fluvial facies that are dominated by upper flow regime deposition, to mounded carbonate strata. Laterally equivalent mudstone facies are similarly heterogeneous, ranging from laminated oil shale with abundant fish fossils to pedogenically modified playa facies associated with nonmarine evaporites.  Distinctive biological marker compounds (biomarkers) are associated with each of these facies, and can be used to help determine paleoenvironmental setting.

In addition to field studies, several classroom lectures will be used to illustrate the main course concepts and to provide geologic background information on the field areas.  Because fine-grained rocks can appear rather different in core than in outcrop, we will also conduct a half-day core workshop based on representative examples of the major facies associations. We will spend some time developing criteria for subsurface recognition using wire-line logs, seismic, and organic geochemistry.

26-Jan-2010