Application of Field-Wide Conventional Coring In the Jay-Little Escambia Creek Unit

Abstract

This paper discusses the application of data obtained from a field-wide conventional coring program in the Jay-Little Escambia Creek Unit. Benefits derived from the program far exceed the $5 million cost. Conventional coring of every well has proven the key factor for effective reservoir management of this major reserve. Introduction Early drilling and conventional coring in the Jay and Little Escambia Creek fields indicated that large oil deposits were contained in a thick, pressure depletion reservoir. Unitization and pressure maintenance would be necessary to increase the anticipated low primary recovery. To develop a basis for unitization and to plan the pressure maintenance program, a comprehensive pressure maintenance program, a comprehensive reservoir description was desirable. Field operators decided to expand early conventional coring field-wide to provide the necessary data. During development in 1970-74, 102 wells were drilled and cored conventionally through the Smackover carbonate formation. Average core recovery was 82%. Porosity and permeability were measured from more than 23,000 ft of core.Results of field-wide conventional coring were applied successfullyfor developing a basis for unitization,for planning the pressure maintenance program,for planning and evaluating well completion programs,for constructing a three-dimensional programs, (4) for constructing a three-dimensional reservoir description model,for analyzing and predicting waterflood behavior, andfor selecting infill-drilling well locations.A 12-well infill-drilling program began in 1977. Seven infill wells were drilled successfully and two drilling rigs now operate in the fields. Each well was cored conventionally to supplement reservoir description and to provide necessary data for optimum completion provide necessary data for optimum completion planning. Conventional coring continues for the rest of the planning. Conventional coring continues for the rest of the program. program. Field Description Jay Field is located in northwest Florida about 35 miles north o Pensacola. A small portion of this field extending into Alabama was named Little Escambia Creek. Jay Field was discovered by Exxon Co., U.S.A., in June 1970 and contained about 730 million STB of original oil in place.Oil accumulation in the Jay-Little Escambia Creek fields is located in the Smackover carbonate and Norphlet sand formations. Oil occurs mostly in the dolomitized portions of the Smackover carbonate. Fig. 1 is a structure portions of the Smackover carbonate. Fig. 1 is a structure map contoured on top of the Smackover formation. This formation is found slightly below 15,000 ft, and its average thickness is about 350 ft. The formation is layered with high permeability contrast among layers. Table 1 presents a summary of rock and fluid properties, presents a summary of rock and fluid properties, reservoir properties, and production-injection data for the field. Five operators were active during development from 1970-74: Exxon Co., U.S.A.; Louisiana Land and Exploration Co.; Chevron U.S.A., Inc.; Sun Co.; and Amerada-Hess Corp. After analyses of early drilling and conventional coring established the need for unitization and pressure maintenance, these operators decided to expand conventional coring field-wide. A total 102 wells eventually were drilled as the field was developed on 160-acre well spacing. JPT P. 1774