This paper presents empirical infill drilling forecast models and infill well economics for Permian Basin Clearfork and San Andres waterflood units. Four infill recovery indicators were analyzed: 1) ultimate recovery, 2) incremental recovery, 3) recovery per well, and 4) recovery per acre-ft. It was estimated from these forecast models that an additional 6.9% OOIP or 710 MMSTB could be recovered by infill development to 10 acre well spacing in those units studied.

Infill recovery forecast models developed have waterflood recovery and fraction reduction in well spacings as independent variables. The forecast results match actual field data reasonably well. Reductions in well spacings seemed to play a more significant role in determining infill performance in Clearfork than in San Andres.

Economic analyses were performed on an infill well basis. Breakeven economic analysis was conducted for the first guantile reserve level of 70 MSTB and by varying initial production rates. A set of curves were generated for each formation as a quick reference.

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