ABSTRACT

Red Fish Bay field exemplifies the tremendous bypassed hydrocarbon potential in supposedly depleted sandstone reservoirs of the Frio Formation in South Texas. Since discovery in 1950, Red Fish Bay field has produced nearly 19 MMBBL of oil and 32 BCF of gas from more than 50 stacked Frio sandstone reservoirs. Upper Frio oil and gas reservoirs account for 80% of total field production, although these reservoirs were recently abandoned in favor of deeper Frio targets.

This study focused on delineating bypassed hydrocarbons in these prolific upper Frio reservoirs. The sandstone reservoirs are 7,300 to 8,500 ft deep and consist of stacked and amalgamated shoreface to inner-shelf sandstones interbedded with shelf mudstones. Geological mapping and analysis of well log and production data document underexploited areas with excellent hydrocarbon saturation. Analysis of logs from recently drilled wells that targeted deeper Frio pay confirm that upper Frio hydrocarbons have been bypassed.

Conservative estimates of the remaining hydrocarbon potential indicate that nearly 47 MMSTB (average 87% of OOIP for reservoirs on primary recovery alone) and 44.5 BCF (> 90% of OGIP) remain in the reservoirs. The better developed oil and gas reservoirs have attained primary recovery efficiencies of 25% and 90%, respectively. Using these primary recovery factors, recommended recompletion and infill drilling strategies are expected to add 6.3 MMBBL of oil and 40 BCF of gas to the estimated ultimate recovery from Red Fish Bay field. An estimated 26.7 MMBBL of mobile oil will remain in the reservoirs following primary production, and implementation of a waterflood recovery program will further increase ultimate hydrocarbon recovery.