Gas Chromatography as a Tool for Reservoir Continuity Determination and Field Management

R. L. Kaufman, A. S. Ahmed

Determining reservoir continuity is important for planning an effective field development program and subsequent field management. The question of where the fluids are coming from is inevitably encountered. The traditional approach to establishing reservoir continuity is a combination of wireline log correlations and pressure tests for hydraulic communication. An alternative approach, though not as well known, is analyzing the reservoir fluids. This paper deals specifically with crude oil analysis, but similar applications exist for formation waters.

In our worldwide experience over the past 20 years, we have determined that oils in a continuous reservoir have a uniform hydrocarbon composition in the C⁷-C³⁵ range when sampled away from the oil-water or gas-oil contacts. Furthermore, oils in separate reservoirs have hydrocarbon compositions that are significantly different, although the differences may be small. The most successful technique for determining reservoir continuity is whole-oil-gas chromatography. Oil correlations using the chromatographic fingerprints can be made using various graphical and multivariate statistical techniques. The chromatographic technique is inexpensive, especially compared to other field evaluation costs. The technique is a simple and rapid analysis, which can be performed in field production laboratories by using oil samples from well tests (DST and RFT), production samples, and core extracts. Case histories illustrate how this technique has been used to solve development and production problems.

AAPG Search and Discovery Article #91030©1988 AAPG Annual Convention, Houston, Texas, 20-23 March 1988.