Variations in Oil Composition During Production and Water Flooding: A Case Study in the Prairie Gem Field, Central Oklahoma

Elli Chouparova

Reservoir geochemistry is a relatively new application of geochemistry to the solution of production and reservoir characterization problems. Oil production decreases often are related to reservoir heterogeneities caused by compositional changes of the oils and their interactions with the mineral matrix. The aim of present study is to evaluate compositional changes occurring in oils during production before and after water flooding and the influence of these changes on reservoir performance.

The Prairie Gem Field, located in Lincoln Co. of Central Oklahoma, where the water flooding had started in 1993 was selected for this study. The oils were collected from well-heads at different stages of production before and after the water flooding and analyzed by gas-chromatography, high temperature gas chromatography and gas chromatography - mass spectrometry. Detailed geochemical studies of the oils collected prior to water flooding enabled various oil families related to different production zones to be differentiated and to determine the extent of reservoir continuity. The changes in relative abundances of alkanes, asphaltenes and waxes content during different stages of production will be further discussed in relation to the vertical and horizontal heterogeneity of the reservoirs and the fractionation effects on the mobile oils.

AAPG Search and Discovery Article #91020©1995 AAPG Annual Convention, Houston, Texas, May 5-8, 1995