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Abstract

Three of Chevron's successful Kern River Field Steam Drive Projects (Section 3, Monte Cristo II, and American Naphtha) have been converted to either hot waterfloods or low quality (10%) steam injection projects. The projects' net oil production has projects. The projects' net oil production has increased significantly because of the reduced oil consumption at the steam generators. In general, the conversion to low quality steam or hot water injection has improved the oil production response of each project.

Production and reservoir data suggest that improved Production and reservoir data suggest that improved sweep efficiency in the lower part of the steam driven sands occurred as a result of the switch from high steam quality injection to reduced steam quality. This paper discusses the performance of these three projects. Production and reservoir parameters are identified which can be used to parameters are identified which can be used to determine the timing for conversion of a mature steamflood to a lower quality steam injection project. project

Introduction

This paper discusses the performance of Chevron's Section 3 (Ten-Pattern), American Naphtha, and Monte Cristo II steam drive projects located within the Kern River Field. Sections (patterns) of the American Naphtha and Monte Cristo II steam drive projects were converted from high quality steam projects were converted from high quality steam (greater than 40%) to low quality steam (10% quality steam at the wellhead) injection in September 1981 and February 1982, respectively. The Phase I area (Ten-Pattern) of the Section 3 steam drive project was converted from high quality steam to hot water injection in October 1975. The objectives of the study presented in this paper were to:

  1. define reservoir characteristics;

  2. review the field performance, reservoir behavior, and overall performance, reservoir behavior, and overall operating costs; and

  3. develop guidelines for selecting candidates for the conversion of mature steam drive projects (generally where steam qualities greater than 40% were being injected) to low quality steam and/or hot water injection.

In general, the projects did not experience any significant loss in production as a result of the conversion to low quality steam and/or hot water injection. This appears to be the result of improved vertical sweep efficiency in the lower drive sands and reduced gravity override effects as a consequence of thermal distribution changes that occurred since the conversion. Converting from high to low quality steam and/or hot water injection resulted in reduced fuel oil consumption which enhanced the net oil production and overall operating economics of the three projects.

The performances of these three projects were analyzed to develop some general guidelines which could be used to determine the optimum time to convert mature steam drives to low quality steam injection or hot waterflood projects. Parameters for these guidelines include reservoir properties, heat input, temperature profiles, steamflood maturity, and steam-oil ratio.

RESERVOIR AND PROJECT DESCRIPTIONS

The three Chevron projects discussed in this paper were chosen for analysis because they are currently under low quality (10%) steam injection or hot water injection after high quality steam injection. The projects are located in the Kern River Field (see projects are located in the Kern River Field (see Figure 1). Section 3 Ten-Pattern (Phase I) project is Chevron's oldest steam drive project and has been discussed in previous publications. The Monte Cristo II project is located within Chevron's Monte Cristo II property and consists of nine 2.5 acre 5 spot inverted patterns. This project is surrounded by other steam drive patterns on the Monte Cristo II property. The American Naphtha project consists of property. The American Naphtha project consists of sixteen 2.5 acre 5-spot patterns and is located on the American Naphtha lease.

The steam drive sands are part of the Kern River Series. These sands are Mio-Pliocene in age and are composed of unsorted, coarse grained, angular and silty sands. The steam drive sands have an average porosity of about 34 percent, a pre-steam drive oil porosity of about 34 percent, a pre-steam drive oil saturation of 50 percent and permeability ranging from 1,000-2,000 millidarcies.

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