A Miscible WAG Project Using Horizontal Wells in a Mature, Offshore, Carbonate Middle East Reservoir

Abstract This paper summarizes the design, operation, results, and reservoir modeling of a miscible hydrocarbon gas injection pilot using horizontal wells in the Fateh Mishrif, a large carbonate reservoir in an offshore operating environment.The pilot included a single horizontal water-alternating-gas (WAG) injector flanked by two horizontal producers drilled near the base of the reservoir.The three-well pattern was surrounded by four water injectors which provided confinement and pressure control.Produced gas from the field was used for injection without supplemental enrichment. The pilot began operations in 1997. Commencing in 1999, gas was injected in three cycles over a period of four years. A clear incremental oil rate response to the gas injection was first observed in early 2003, peaking with a 400% incremental oil rate increase from the two producers. Pilot results have been history matched with a compositional reservoir model to reconcile reservoir characterization interpretations and to provide prediction of ultimate recovery. Incremental recovery over waterflood operations is predicted to be 6% of original oil-in-place for 0.15 hydrocarbon pore volumes of gas injection.