ABSTRACT: The Role of Oil-to-Oil Correlation in the Development of the Safah Field, Oman

F. A. Lindberg, A. S. Ahmed, C. T. Bluhm

The Safah field, located in northwestern Oman, is a large carbonate reservoir on a gently dipping structural nose. To date, more than 90 wells have been drilled in the field, which is operated by Occidental (Chevron share 35%). The Lower Cretaceous Shuaiba Formation limestone forms the reservoir.

Differences in the productivity of the wells in the Safah field is controlled by depositional and diagenetic processes that produced differences in the character of the carbonate.

To better understand the distribution of the reservoir rocks in the field, oil-to-oil correlation studies, involving samples from the first 35 wells in the field, were done in 1986 and 1988. Peak height ratios from gas chromatograms were plotted on star diagrams and used for the correlation.

Three different oil groups were found in the field. The presence of three different oils in what was thought to be a continuous reservoir implied that some barriers to oil mixing are present. Subsequent drilling revealed several areas in the field that may be parts of these barriers. In these areas, which often occur within a few hundred meters of good producing wells, the top of porosity is often very low and the reservoir is of very poor quality. These characteristics may be attributable to either lateral facies changes or diagenetic differences.

By indicating these barriers to oil mixing occur in the field, geochemical analysis may prove useful for locating areas in the field which may be less desirable to develop.

AAPG Search and Discovery Article #91003©1990 AAPG Annual Convention, San Francisco, California, June 3-6, 1990