Discovery of volcanic glass detritus in fluvial deposits of the middle Frio Formation (Seeligson and Stratton fields) of South Texas has resulted in a new classification of reservoir types (type I and type II) within this formation.

The wide variability in structural styles within the growth-faulted, geopressured trends of the Texas Gulf Coast is illustrated by detailed structural maps of selected areas of the Wilcox and Frio growth-fault trends and quantified by statistical analysis of fault compartment geometries.

Sandstone reservoirs deposited in microtidal barrier systems contain large oil and gas reserves in several Gulf Coast Basin plays.

Many modern shore zones comprise a continuum of depositional environments that encompass both strandplain and barrier-island systems. Strandplains are further subdivided into two classes: sand-rich beach-ridge plains and mud-rich chenier plains.

The Frio Formation is one of the major Tertiary progradational wedges of the Texas Gulf Coast Basin and has yielded nearly 6 billion bbl of oil and 60trillion ft30f gas.

Reservoir quality of lower Teritary sandstone reservoirs along the Texas Gulf Coast is controlled by sandstone depositional environment, mineralogical composition, and consolidation history (compaction, cementation, and leaching).

The objective of this study is to identify major sand trends, which, along with subsurface temperatures and pressures, aid in evaluating the potential of producing geothermal energy from the Frio Formation, Upper Texas Gulf Coast.

Knowledge of the regional sand distribution and its relationship to formation temperature and pressure is a preliminary step in evaluating the geothermal resources of the Frio Formation.

A preliminary study of the Frio sand distribution and formation temperatures and pressures was undertaken in order to define prospective areas in which a more detailed reservoir analysis is necessary prior to the selection of a site for a geothermal well.