Abstract: Stratigraphy and Entrapment of Hydrocarbons in San Miguel Sandstones of Southwest Texas

J. O. Lewis

The San Miguel section in the Maverick basin of the Rio Grande embayment is a series of overlapping sand bars striking NE-SW. Grain-size plots and core descriptions indicate that these bars developed in a shallow marine-shelf environment. There are as many as seven discrete sandstones, all but one having production established. These sandstones have a cumulative production of over 50 million bbl of oil since 1948. Over 30 million bbl of oil has been produced from stratigraphic-type fields discovered since 1970. Stratigraphic-type fields have produced over 90% of the total production. Structural traps caused by differential compaction over volcanic necks account for the rest.

Torch field, a volcanic neck in Zavala County, and Sacatosa field, a stratigraphic trap in Maverick County, are typical fields.

The depth and density of control, as well as the subtle expression of the traps, indicate many prospective areas.

AAPG Search and Discovery Article #90967©1977 GCAGS and GC Section SEPM 27th Annual Meeting, Austin, Texas