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GeoMark Research, Houston and Dallas, Texas

Abstract: Identification of Under-Explored Petroleum Systems in "Mature" Trends A South Texas Example

Geochemical analysis of large collections of crude oils from areas of specific exploration interest provides an opportunity to identify oils under-represented by production. Oils compositionally reflect the geochemistry of their sources, and their analysis permits mapping of the geographic and stratigraphic extent of the petroleum systems to which they belong. The analysis also permits prediction of the depositional environments of the oils' source rocks, evaluation of the thermal history of the oils, and determination of geochemical and geological controls on crude oil quality.

A study of Mesozoic oils from South Texas is presented as an example of the use of oil geochernistry as an important element of an exploration strategy. Oils from the Maverick Basin were analyzed in context of a larger framework study of the greater Gulf of Mexico Basin (750+ oils). The larger study helped define many problems relating to the distribution of various hydrocarbon source intervals. The abrupt "disappearance" of Jurassic sources and the irregular distribution of sources of Lower Cretaceous age were addressed using additional oils from South Texas.

The South Texas study leaves the Jurassic problem unresolved; however, the study contributes important information about the character and distribution of Lower Cretaceous sources in Texas. Simply stated, exploration for new Lower Cretaceous production should be concentrated in specific areas where oils derived from related sediments have been observed to occur.

AAPG Search and Discovery Article #90918©1999 AAPG Southwest Section Meeting, Abilene, Texas