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Source Rock Study of Smackover Formation from East Texas to Florida

Roger Sassen, C. H. Moore

Analyses of core and crude oil samples indicate that the laminated lime mudstone facies of the lower Smackover Formation is a significant source rock across the trend. The source facies was deposited in an anoxic and hypersaline environment that permitted preservation of algal kerogen. Moreover, source potential also occurs in undifferentiated Gilmer-Smackover rocks of east Texas deposited in a carbonate slope environment.

Thermal maturity is the key factor that controls the generation of crude oil by the carbonate source facies and the eventual destruction of hydrocarbons in upper Smackover and Norphlet reservoirs. Once the regional thermal maturity framework is understood, it is possible to construct a source rock model that explains the distribution of crude oil, gas condensate, and methane across the trend. Calculated thermal maturity histories provide insight to the timing of hydrocarbon generation and migration and to the timing of hydrocarbon destruction and sulfate reduction in deep reservoirs.

Basic geochemical strategies for exploration are suggested. One strategy is to focus exploration effort on traps formed prior to the time of crude oil migration that were nearest to effective source rocks. Another strategy is to avoid drilling reservoir rocks that are thermally overmature for preservation of hydrocarbons.

AAPG Search and Discovery Article #91038©1987 AAPG Annual Convention, Los Angeles, California, June 7-10, 1987.