Stimulation of Water Injection Wells in the Los Angeles Basin By Using Sodium Hypochlorite and Mineral Acids
Authors: Clementz David M. , Patterson David E. , Aseltine Richard J. , Young Roger E. 
Published: December 2007

Summary
A stimulation program was developed to improve injectivity and vertical coverage of water injection wells in the East Beverly Hills and San Vicente fields. Damage materials were removed by stimulating the wells with bleach and acid using a variety of tools and techniques. Two- to three-fold injectivity improvements were common, and vertical distribution was typically improved from an initial coverage of 0 to 30 % to 85 to 95 % after stimulation.

Introduction
Numerous methods have been proposed for stimulation of water injection wells to improve performance. Successful application of these methods requires a reasonable understanding of the nature and the cause of poor performance. However, a clear understanding of poor performance. However, a clear understanding of the problem often doesn't develop until the job is underway and further evidence is obtained. Flexibility in job design and implementation is essential to successful improvement of well performance.Early in 1980, a program was initiated to stimulate water injection wells in the East Beverly Hills field in the Los Angeles basin. As the work progressed, we found evidence that the damage mechanism was complex, requiring that the wells be treated in a series of steps using bleach, acid, and solvent applied with several mechanical techniques. As more wells were stimulated successfully, a strategy was developed that also proved effective in the nearby San Vicente field.This paper describes the stimulation strategy, which may have widespread application, and illustrates its usefulness by examples from the Los Angeles basin. Further, the importance of using oxidizing agents, especially bleach, to remove bacterial damage is reemphasized.

Reservoir Description
East Beverly Hills Field. This field is in an urban area of west Los Angeles. The basic geologic structure is a plunging asymmetric anticline, approximately 2.3 miles plunging asymmetric anticline, approximately 2.3 miles (3.7 km) long and 0.7 miles (1.1 km) wide. The primary target of the stimulation program was the Main primary target of the stimulation program was the Main (Hauser) zone. This zone contains 13 major sand units separated by impermeable siltstone layers 25 to 200 ft (7.6 to 60 m) thick. The average sand unit thickness is 100 ft (30 m). These sandstone layers have average porosity of 25% and average permeability of 58 md, porosity of 25% and average permeability of 58 md, ranging from 2 to 1,000 md, and contain significant amounts of water-sensitive clay minerals, including illites and montmorillonites.The Main zone was developed primarily from the Packard drillsite during 1967-70. All wells are Packard drillsite during 1967-70. All wells are directionally drilled at drift angles up to 60 deg. and course changes up to 180 deg. The average measured depths to the top and bottom of the zone are 7,200 and 8,500 ft (2200 and 2600 m), respectively [equivalent to vertical depths of 6,200 and 7,300 ft (1890 and 2230 m)]. Injection wells were completed by selectively perforating 7-in. (180-mm) cemented casing with four 1/2-in. (13-mm) jet holes per foot (0.3 m).Initial production of the 28 deg. API (887-kg/m3) oil resulted primarily from solution gas drive with some natural water influx. A peripheral water injection program began in Jan. 1970, and it now involves 14 program began in Jan. 1970, and it now involves 14 injectors injecting 25,000 B/D (4000 m3/d) at approximately 2,800 psi (19 000 kPa).
San Vicente Field. This field is located approximately 3 miles (4.8 km) northwest of the Beverly Hills field. The basic geologic feature is a faulted stratigraphic trap. The objective of this stimulation program is the Clifton Zone.
JPT
P. 2087