Proved Recovery From the Seventy-Six West Field by Geologically Targeted Infill Drilling and Waterflood Optimization

The Seventy-Six West field, Duval County, Texas, has produced 4.6 MMstb of oil from the Cole "B" and "C" sands of the Jackson Group of Eocene age. Due to the complex reservoir geometry, mobile oil has been trapped in the reservoir in compartments poorly contacted by the current well spacing or in zones poorly swept by waterflood. If operated in its current mode, the field is projected to produce an additional 347 Mstb, for a total of 4.9 MMstb. This represents approximately 20% of the OOIP, indicating that there is much potential for development This study evaluated the current status of the northeastern part of the field, and examined schemes for efficient recovery of the remaining oil by geologically targeted infill drilling and waterflood optimization. Waterflooding has the potential for improving recovery by repressurizing the reservoir. Infill drilling should provide access to inefficiently drained areas and possibly untapped compartments. Simulation results indicate that waterflooding can significantly improve oil recovery. Recovery can further be improved by combining infill drilling with a waterflood. The waterflood can be optimized by an appropriate injection scheme to reduce the amount of water injected without significantly reducing the amount of oil recovered.