Abstract: A Reservoir Study of the Friendswood Field

By

E. A. Blair, B. K. Enquist, Jr., L. W. Good, and E. C. Walton, Jr.
Humble Oil and Refining Company
Houston, Texas

A geologic and engineering study of the Friendswood field, located immediately south of Houston, has shown that significant increased oil reserves in the tens of millions of barrels can be realized by unitized projects designed to halt oil migration into the gas cap, increase oil recovery efficiency, and maintain reservoir pressure.

The study involved zoning the 700 feet of upper Frio oil and gas productive section, locating current fluid contacts, and then mapping oil and gas volumes in each zone at original and current conditions. Reservoir behavior was analyzed principally by material balance and unsteady state water influx calculations. The study showed that oil was being displaced into the gas cap on the east side by a strong water drive, while gas cap expansion, although 14 percent less efficient than water in displacing oil, is being experienced in several zones on the west side due to a limited water drive.

An interim gas injection project has been installed to stop oil migration. A water pressure maintenance program will be initiated as soon as unitization can be accomplished.

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