The Jay field produces a light, sour crude from the Smackover carbonate at a depth of 15,000 feet [4600 meters]. Jay has been undergoing a miscible flood using alternating nitrogen and water injection since 1981. A third-party air liquefaction plant supplies the nitrogen; current injection rates are 77×106 scf/D [2.2×106 m3/D] of nitrogen and 170,000 bbl/D [27 000 m3/D] of water. The overall oil recovery at Jay is expected to approach 60% of OOIP with recoveries approaching 70% in the Upper Smackover formation. Incremental recovery from miscible nitrogen injection is estimated to be 7-10% of OOIP.

Most wells in the Jay field were cored, providing detailed rock properties for construction of valid and useful geologic and reservoir simulation models for reservoir management. Extensive core descriptions have identified cemented zones associated with stylolites as baffles to vertical flow. Recognizing, the resulting low vertical permeability, coupled with high horizontal permeability in the dolomite facies, has been the key to the high oil recovery.

Reservoir simulation has been an integral part of the development and operation of the Jay field. The latest full-field flow simulation model is derived from a new geologic model that incorporates sequence stratigraphy, the latest geostatistical methods, and a stylolite model. The flow simulation model is also more finely gridded than previous models and includes an updated fluid characterization treatment making possible simulation of processes that could not be accurately modeled previously. The history match of this model entailed well by well matches of production and pressure data for all 137 wells in the field.

Full-field flow simulation models of Jay have historically been used to evaluate the benefits of extending nitrogen injection, recycling produced nitrogen, and increasing water injection rate. Recent studies using the updated full-field model have been performed to optimize nitrogen distribution among patterns, investigate low-pressure operation, evaluate dedicated Lower Smackover wells, assess full-wellstream injection, and evaluate conversion of producers to injectors. Based in large part on these simulation studies, several major initiatives have been undertaken that extended field life by more than ten years.

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