Waterflooding a Thick, Heterogeneous Reservor in the Los Angeles Basin: A Case History
Authors: Parsons A.R. , Lucidi N.A. , Maloney T.R. , Patterson D.E. 
Published: December 2007

The history of waterflooding the Vickers East pool is presented. The role of clean injection water in improving oil recovery, the development of an effective waterflood pattern, and the techniques used to optimize vertical coverage of water-injection wells are discussed in terms of completions, downhole equipment, and stimulation. An extensive realignment project involving an active drilling program is currently under way in the Vickers East pool.

Introduction

The Vickers East pool is located in the Los Angeles basin. One of several oil-producing horizons within the Inglewood field, it is a thick (1,000- to 1,400-ft [305- to 425-m] gross interval), unconsolidated, highly faulted sandstone reservoir. Finely laminated with siltstones and shales, most of its individual sand bodies are &lt;6 ft [&lt;1.8 m] thick and many are &lt;2 ft [&lt;0.6 m] thick.

Because of the numerous sand bodies and their heterogeneous nature (permeability variation =0.6), water injection wells historically tended to exhibit poor vertical distribution of injected water. To compound the problem further, unfiltered produced brine was injected for many years, resulting in plugged perforations, formation damage, and scale/corrosion problems. Although waterflooding of the Vickers East began in 1954, a consistent fieldwide injection pattern was never established.

Clean injection water was obtained for the flood in the late 1970's, resulting in a sharp increase in oil production. An extensive realignment program was undertaken in 1985 to establish an effective waterflood pattern. Through 1987, 21 injectors and 14 producers were drilled. Completions and downhole equipment used in the new injectors are tailored to optimize vertical coverage, while stimulation is used as necessary to modify injection profiles.

Field Discovery and Reservoir Development

The Inglewood field is located about 10 miles [16 km] southwest of downtown Los Angeles. The field's broad anticlinal structure covers 1,215 acres [492 ha] of surface and is transected by the Inglewood fault, a major strike-slip fault that is part of the northwest-trending Inglewood-Newport fault system (Fig. 1). This fault, which act as a barrier to fluid migration, divides the Inglewood field into east and west blocks and has about 2,500 ft [760 m] of horizontal and 1,000 ft [305 m] of vertical displacement. The two most striking features of the reservoirs within the Inglewood field are their large gross thicknesses and numerous faults, most of which parallel the Inglewood fault.

The field was discovered in 1924 with a completion in the Vickers zone. Wells with initial production rates of more than 1,000 BOPD [160 m3/d oil] were common. Peak field production of 50,000 BOPD [7950 m3/d oil] occurred in 1925. The Inglewood field had original oil in place (OOIP) of about 1 billion bbl [160×106 m3], of which about 33% has been produced.

Vickers East Pool.

Spanning a surface area of 250 acres [100 ha] (Fig. 2), the Vickers East pool has its topmost sand located at depths ranging from 900 to 1,100 ft [275 to 335 m]. As shown in Fig. 3, it encompasses 14 distinct sand packets, called Alpha through O, each with a characteristic, correlatable log response found throughout the reservoir. Each sand packet is vertically isolated by shale barriers 20 to 50 ft [6 to 15 m] thick. The pool is highly faulted, as shown by cross section in Fig. 4. Net sand ranges from 30 to 60% of the gross interval. Currently under waterflood, production from the pool averages 1,150 BOPD [180 m3/d oil] and 24,000 BWPD [3800 m3/d water] with an injection rate of 29,000 BWPD [4600 m3/d water].

Primary Recovery.

The OOIP of the Vickers East pool was 152 million bbl [24.2×106 m3] with no gas cap present at discovery. The original reservoir pressure was 570 psi [3930 kPa], and the initial solution GOR was 90 ft3/bbl [16 m3/m3]. Solution-gas drive was the predominant mechanism of primary recovery, with a weak waterdrive in the northwesterly portion of the reservoir. Gravity drainage was of minor importance because of the low dip of the sands and the high degree of faulting, which limited continuity.

The pool was developed from 1924 to 1929 on 4-acre [1.6-ha] spacing. An infill drilling program, conducted from 1947 to 1954, reduced the well spacing to 2 acres [0.8 ha]. At the time of the pilot waterflood in 1954, reservoir pressure had declined to 20 to 100 psi [140 to 690 kPa]. Primary recovery had accounted for 17.3% of the OOIP, with ultimate recovery expected to reach 21.9%.1

Secondary Recovery.

Waterflooding of the Vickers East pool began with a pilot five-spot pattern in June 1954. Within 2 years, production from the central producer and surrounding first-line producers had increased to about twice that expected from primary recovery. A second pilot carried out on larger spacing in 1956 also exhibited strong oil response. The two pilot floods combined to increase production by a peak of 250 B/D [40 m3/d] and cumulative 119,000 bbl [18 900 m3] oil over primary production by the end of 1956.

Because of the encouraging results from the pilots, commercial waterflooding began in 1957. Peak production was forecasted to reach 8,000 BOPD [1270 m3/d oil] in 1961, a gain of 6,000 B/D [950 m3/d] over the Oct. 1956 rate of 2,000 BOPD [320 m3/d oil]. A recovery of an additional 20.8 million bbl [3.3×106 m3] of waterflood oil was predicted, with the project expected to reach its economic limit in 1975.

Actual production figures, however, fell short of expectations. Peak production occurred in April 1964 at a rate of 4,000 B/D [635 m3/d] (Fig. 5). Estimates of ultimate waterflood gain were reduced in 1967 to 10.5 million bbl [1.7×106 m3] oil, or roughly one-half the 1956 estimate.

Vickers East Pool.

Spanning a surface area of 250 acres [100 ha] (Fig. 2), the Vickers East pool has its topmost sand located at depths ranging from 900 to 1,100 ft [275 to 335 m]. As shown in Fig. 3, it encompasses 14 distinct sand packets, called Alpha through O, each with a characteristic, correlatable log response found throughout the reservoir. Each sand packet is vertically isolated by shale barriers 20 to 50 ft [6 to 15 m] thick. The pool is highly faulted, as shown by cross section in Fig. 4. Net sand ranges from 30 to 60% of the gross interval. Currently under waterflood, production from the pool averages 1,150 BOPD [180 m3/d oil] and 24,000 BWPD [3800 m3/d water] with an injection rate of 29,000 BWPD [4600 m3/d water].

Primary Recovery.

The OOIP of the Vickers East pool was 152 million bbl [24.2×106 m3] with no gas cap present at discovery. The original reservoir pressure was 570 psi [3930 kPa], and the initial solution GOR was 90 ft3/bbl [16 m3/m3]. Solution-gas drive was the predominant mechanism of primary recovery, with a weak waterdrive in the northwesterly portion of the reservoir. Gravity drainage was of minor importance because of the low dip of the sands and the high degree of faulting, which limited continuity.

The pool was developed from 1924 to 1929 on 4-acre [1.6-ha] spacing. An infill drilling program, conducted from 1947 to 1954, reduced the well spacing to 2 acres [0.8 ha]. At the time of the pilot waterflood in 1954, reservoir pressure had declined to 20 to 100 psi [140 to 690 kPa]. Primary recovery had accounted for 17.3% of the OOIP, with ultimate recovery expected to reach 21.9%.1

Secondary Recovery.

Waterflooding of the Vickers East pool began with a pilot five-spot pattern in June 1954. Within 2 years, production from the central producer and surrounding first-line producers had increased to about twice that expected from primary recovery. A second pilot carried out on larger spacing in 1956 also exhibited strong oil response. The two pilot floods combined to increase production by a peak of 250 B/D [40 m3/d] and cumulative 119,000 bbl [18 900 m3] oil over primary production by the end of 1956.

Because of the encouraging results from the pilots, commercial waterflooding began in 1957. Peak production was forecasted to reach 8,000 BOPD [1270 m3/d oil] in 1961, a gain of 6,000 B/D [950 m3/d] over the Oct. 1956 rate of 2,000 BOPD [320 m3/d oil]. A recovery of an additional 20.8 million bbl [3.3×106 m3] of waterflood oil was predicted, with the project expected to reach its economic limit in 1975.

Actual production figures, however, fell short of expectations. Peak production occurred in April 1964 at a rate of 4,000 B/D [635 m3/d] (Fig. 5). Estimates of ultimate waterflood gain were reduced in 1967 to 10.5 million bbl [1.7×106 m3] oil, or roughly one-half the 1956 estimate.