Analysis of a Steam Drive Project, Inglewood Field, California

Abstract

This is the first reported California field data on the vertical extent and residual oil saturation of the steam swept zone. Field-derived data on reservoir heat distribution support the published theoretical data. Introduction The Inglewood field, discovered in 1924, occupies a faulted anticline along the Newport-Inglewood Fault System on the western edge of the Los Angeles basin (Fig. 1). The Upper Investment zone, UB sand, selected for this test is the shallowest producing reservoir in the field and lies about 1,000 ft below surface ( 650 subsea). The UB sand productive limit are defined by an updip sand pinchout, the Inglewood Fault, and by down-dip water. The UB sand is 40 to 60 ft thick, consists of fine- to coarse-grain sand with occasional pebbles, ranges from soft to unconsolidated, is overlain by a thick siltstone section and has bottom water. The reservoir properties are shown in Table 1, and electric log characteristics in Fig. 2. The air permeability ranges from 3.3 to 14.3 darcies in the top 40 ft of the reservoir, and porosity averages 39 percent. The primary producing mechanism is pressure depletion with primary producing mechanism is pressure depletion with water encroachment. Oil in place at start of project was 1,930 bbl/acre-ft. The Investment zone oil is asphalt base, 14 degrees API gravity with an in-situ viscosity of 1,200 cp. The high oil viscosity, low reservoir pressure, shallow depth and high oil saturation are all favorable for application of thermal recovery methods. Preliminary laboratory studies of steamflooding in Inglewood cores indicated that residual oil saturations of approximately 20 percent could be achieved with throughput of 1 PV of water converted to steam. Chevron Oil Field Research Co. and Standard Oil Co. of California, WOI conducted the Investment zone lost to learn if the low laboratory residual saturations could be obtained in the field and to determine the oil displacement efficiency in the project area. The test was designed to obtain data on vertical and areal coverage, heat losses, and rate of steam front advance, and to evaluate producing problems associated with continuous steam injection. Design Project Area Project Area Fig. 3 shows the steamflood pilot layout. It is an inverted six-spot containing 2.6 acres within the five first-line producing wells. The project area of the reservoir has essentially no dip. Injection Well 270 and Temperature Observation Wells 271, 272, 273 and 293, were newly drilled for the project. The location of Wells 304 and 304A, which were drilled specifically to obtain post-steam saturation, is also shown in Fig. 3. Well Completions The injection well was completed in only the top 40 ft of sand to avoid water and was perforated in a 30-ft interval 10 ft below the top of the sand. The four temperature observation wells were completed by cementing 3 1/2-in. tubing through the UB sand to surface. Observation Well 271 also was cored to establish presteam saturations in the pilot area. JPT P. 1141