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Formation Evaluation by Compositional Analysis of Residual Hydrocarbon

BELL, BRYAN A., Goode Core Analysis Service, Bakersfield, CA

Many techniques have been developed to provide detailed measurements of the properties of reservoir rock brought to the surface. Little attention has been paid to the composition of the residual hydrocarbons contained in the matrix of these reservoir rocks. Detailed examinations of changes in composition of residual hydrocarbon present will aid in predicting the types of production and potential commericality of the hydrocarbons encountered.

A procedure has been developed to provide a rapid compositional analysis of residual hydrocarbons. Very small quantities of rock (0.01 to 0.2 g) are used. Samples are vaporized and the evolved gases passed directly onto a chromatographic column. The components separated between C5 and C35 are detected by a flame ionization detector and recorder.

Data can be derived from the integration of the recorded output, which indicates changes in the quantity and composition of the oil found in the matrix. Data on the composition of the oil can be related vertically and aerially. Produced crude can also be analyzed by the same procedure for comparison to the oil found in the rock matrix.

Data on the composition provides three areas of information. First, the distribution of light, intermediate, and heavier components can predict types of hydrocarbon production (gas, oil, or water). Second, the relative percentages of the light hydrocarbons can give indications of the rock quality present. Third, the quality can be ascertained from the composition of the residual hydrocarbon in the rock matrix. The quality of crude oil is dictated by one or more of the alteration processes which affect oil subsequent to their accumulation in reservoirs. The changes in the hydrocarbons from these alteration processes is reflected in the composition of the residual hydrocarbon in the rock matrix.


AAPG Search and Discovery Article #91009©1991 AAPG-SEPM-SEG-SPWLA Pacific Section Annual Meeting, Bakersfield, California, March 6-8, 1991 (2009)