Coordination of geological and engineering research in support of the Gulf Coast co-production program. Annual report, June 1986-May 1987

Complex and heterogenous Hackberry reservoirs at Port Arthur field were deposited in a submarine canyon/fan setting. Conventional fieldwide hydrocarbon recovery efficiencies are low, but the potential for secondary gas recovery is high. Free gas remains trapped in uncontacted and untapped compartments at reservoir abandonment. The total fieldwide resource amounts to 13.9 Bcf. The probable and possible resource for a single infill well is 6.5 Bcf in four separate stringers. Three optimum brine-disposal sands and the best brine-disposal site were selected in Northeast Hitchcock field on the basis of sand-body complexity, thickness, depth, and brine-disposal capacity. The equilibrium distribution of inorganic species in different combinations in the produced waters at surface and formation temperatures and pH were estimated from chemical analyses. SOLMNEQ computations suggest carbonate scaling may occur in surface equipment of Miocene disposal sandstones unless inhibitors are used. At Northeast Hitchcock field, well-winnowed sandstones of shallow-marine origin compose the major reservoir sands and act as preferential conduits for fluid migration. Dislodged, abundant authigenic kaolinite in these sands can plug pores during production, suggesting a maximum rate of production will need to be determined to avoid reservoir damage.