California Flood Yields Profitable Recovery of Heavy Oil from Multilayered Reservoir

Abstract

Abstract The Vickers East zone water flood, Inglewood field, Calif., is a project in which oil with reservoir viscosity of 65 cp is being profitably recovered by water flooding an unsegregated 1,200 ft thick zone. The multilayered reservoir consists of interbedded soft shale and unconsolidated sand with a maximum of 520-ft net sand and few shale intervals greater than 20-ft thick. The pool covers 250 acres and contains approximately 73,500 acre-ft of oil sand. The structure dips about 20 degrees and is cut by interior faults with relatively small displacements. A pilot water flood was initiated in 1954 and expanded to a full-scale operation in 1957. As of July 1, 1963, pool injection was 42,000 BWPD, and oil production was 3,400 B/D, or 2,500 B/D above the estimated natural depletion rate. Introduction The Inglewood field is located about 10 miles southwest of the Los Angeles Civic Center (Fig. 1). The Vickers zone is the second shallowest zone of eight major producing intervals in the field. The Vickers East pool lies between 1,000 and 2,200-ft drilled depth. It contains 78 producing wells and 24 injection wells drilled on 300-ft average spacing. A pilot water flood was started in the pool during 1954 and expanded during 1957. Operating problems encountered in this water flood are:running sand conditions in producing wells;casing failures and sanding in injection wells;incomplete areal injection coverage; and50 per cent effective vertical injection coverage. These problems, with the exception of the vertical coverage, have been satisfactorily solved, and current efforts are being directed toward improving vertical coverage. This paper reviews the performance of the water flood to date and presents the approaches used for solution of problems as encountered. The authors hope that experience gained in this project may be of benefit in planning or operating other water floods with similar reservoir characteristics. Reservoir Characteristics Structure and StratigraphyThe Inglewood field is an elongated anticline lying along the Newport-Inglewood uplift, a major regional feature. The eight oil producing horizons in the field (or their stratigraphic equivalents) are cut by the Inglewood fault, which is a right lateral, strike-slip barrier fault with 2,800-ft of horizontal displacement. Producing zones range in depth from 900 to 11,000 ft, and are of Pliocene or Upper Miocene age (Fig. 2). The Vickers zone is the second shallowest producing horizon and is divided into east and west blocks by the Inglewood fault. The east block comprises about one-fourth of the total Vickers zone productive acreage. The Vickers East pool (Fig. 3) is internally cut by relief faults generated by the Inglewood fault movement. The three faults shown in Fig. 3 are now recognized as fluid barriers as a result of waterflood performance. The other faults, which are not fluid barriers, generally parallel Faults III and V. These are shown in Fig. 4, a structural cross section normal to the Inglewood fault. Relatively small vertical displacement of 40 to 80 ft along the interior faults has made them difficult to discern and map, even though electric log correlations from well to well can easily be followed. JPT P. 509ˆ