October 31, 1975 - Gerald R. Ford Presidential Library and Museum

The Tom O'Connor oil field is located in Refugio County, Texas, within
the Oligocene belt of the Texas Gulf Coast.
The principal producing zones are the 5,500; 5,800; and 5,900 foot
Upper and Middle Frio sandstonesof Oligocene age.
The structure at Tom O'Connor is an elon9ated anticline with almost
15,000 productive acres (23 square miles).
The oil recovery mechanism is an active water drive. There were
small original gas caps in the 5,500 and 5,800 foot reservoirs.
Hydrocarbons originally in place were estimated using the volumetric
method. The study team utilized volumetric information which was
furnished by the operators and also that from the Texas Railroad
Commission files. Based upon their own examination, the study team
reduced estimates of net pay thickness and increased estimates of
connate water saturation from the amounts which. previously had been
generally reported. This is most important in the case of the 5,900
foot zone. A material balance analysis of hydrocarbons originally in
place was not considered diagnostic because of poor water production
records and complications caused by migration of fluids between zones.
Oil production rates have apparently peaked in the 5,500 and 5,800
foot zones, but the period of production decline has not been long
enough to establish a predictable trend. The estimate of future
reserves in these zones depends, of course, on the average future
decline rate which has been estimated at about 15 percent per year.
Over half of the reserves at Tom O'Connor are allocated to 5,900 foot
sand which has current capacity to produce in excess of its MER of
30,000 barrels daily. The reserves estimate for this zone .is based
upon an oil recovery efficiency of about 67 percent, which was
determined by empirical correlation methods.
The FEA report on the Tom O'Connor Field was prepared by the Region
VI Office of the Federal Energy Administration located in Dallas, Texas.
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