Empirical Oil Recovery Forecast Models for Waterflood Infill Drilling In West Texas Carbonate Reservoirs

Empirical oil recovery forecast models were developed for waterflood infill drillings in San Andres and Clearfork carbonate reservoirs of Permian Basin. The models were developed using field waterflood databases and the geographical distributions of the ultimate recovery efficiencies. The study evaluated the incremental oil recovery by infill drilling without acceleration of expected oil recovery. Results of testing the empirical oil recovery forecast models indicated an average error of less than six per cent. The forecast models are applicable to a wide range of unit sizes. They are useful for initial evaluations of waterflood infill drilling performance and for property evaluation. The dominant factors affecting the infill drilling ultimate recovery are found to be primary ultimate recovery (geology, pay connectivity, rock properties, etc.), well spacing and development strategies. When the well spacing is to be reduced to below 20 acres, a targeted infill drilling based on reservoir geology, reservoir properties and past production performance should be contemplated instead of a blanket pattern infill drilling.