Surface Expressions of Vertical Migration Containing Moderate Lateral Components

Gary K. Rice
GeoFrontiers Corporation, Dallas, TX

Vertical migration is the cornerstone of near-surface geochemical exploration. Below the water table gases migrate vertically in a separate phase with upward movement due to buoyancy. The pattern of hydrocarbon gases rising vertically from reservoirs to the near-surface makes detecting and mapping petroleum reservoirs possible.

Lateral migration along bedding planes often is moderate compared with the vertical migration component. Some Permian age reservoirs on the Eastern Shelf of the Midland Basin illustrate moderate lateral migration. Examples show how lateral migration affects interpretation of the petroleum reservoir information.

Wages Dreamfield (Tannehill Ss) in King County, Texas, included five producing wells surrounded by dry holes. Geochemical interpretation integrated with subsurface geology recognized a slight eastern (up-dip) lateral migration and successfully predicted a narrow channel between two dry holes.

Grantham field (Tannehill Ss) in Dickens County, Texas, focused on a dry hole and regional mapping. Geochemical data indicated microseepage over the prospective area and was one of the primary tools used during development. A local southerly dip influenced the surface expression of this reservoir.

Cheeseburger field (Frye Ss), Stonewall County, Texas, showed dispersal-type lateral migration which occurred in multiple directions, apparently along bedding planes. Lateral migration was determined during integration of 3D seismic data, subsurface geology, and surface geochemical data.

Regional dip helps predict lateral migration and its direction. Local dip also can influence surface patterns. Dispersion may exaggerate reservoir areal extent. Identifying lateral migration patterns will improve geochemical data interpretation.

AAPG Search and Discovery Article #90078©2008 AAPG Annual Convention, San Antonio, Texas