The Etchegoin reservoir in the Coalinga Field contains over 40MMB of 10–11° API oil-in-place. The reservoir dips at about 14–20°. Following an infill program in 1991, remapping of the reservoir showed significant remaining oil in the downdip area.
Two downdip horizontal wells were planned and drilled in the Basal sand member. Together the wells develop a 25 acre area containing 1.1 MMBO. Production forecasts were generated using a simple analytical model. The model can predict initial production rates but is not adequate for gravity drainage situations. The paper discusses a number of special well design considerations.
Post-soak well performance was promising but showed the need for additional reservoir heat. Slim-hole injectors were added updip and near the horizontal wellbore. Today the two wells add 500 BDO to Coalinga production. This represents 10% of Etchegoin total production.
The Coalinga Team continues to look for additional horizontal well opportunities. Additional potential includes: 1) a new development area with multiple stacked sands of varying continuity, 2) a hot portion of the reservoir where steam entry into vertical wells causes impairment, 3) more downdip extension potential, and 4) a new thin reservoir with limited extent that might be a candidate for multi-lateral well technology.