A Reservoir Study of the Hawkins Woodbine Field

Abstract

Abstract In-depth studies of the prolific Hawkins Woodbine Reservoir have revealed the need for unitization and pressure maintenance with gas. Observed recovery efficiency is over 80% by gas cap drive with gravity drainage whereas recovery is less than 50% at breakthrough in water-invaded areas. Repressuring by injection of over 100 MMcf/day of gas should increase recovery by more than 150million barrels of oil, including substantial oil lost by migration into the original gas cap, and will extend peak productivity of the field by at least 3productivity of the field by at least 3 years. Prior to unitization, an interim Prior to unitization, an interim program is being implemented to stop oil program is being implemented to stop oil migration into gas sands in areas of the field having strong water influx. This interim program consisting of an oil production rate increase of 25,000 barrelsper scheduled day, production of an additional 10,000 barrels per day of saltwater, and gas injection of 20,000 Mcf per day will stabilize gas-oil contacts in loss areas for 3 to 5 years. A team of engineers and geologists studied fluid contact movement using neutron logs and well test data and analyzed past and future reservoir behavior. These studies revealed that an underlying asphalt layer has caused the western part of the field to exhibit an unusual production performance. This part of the field performance. This part of the field initially produced by gas expansion but subsequent reservoir pressure decline has caused substantial water influx through the thinner asphalt in the north. This directional water drive caused oil to migrate into the original gas cap on the north. In order to maximize recovery and permanently stop migration, along-range program of gas injection under unitized operations will be required.