Abstract

This paper describes a feasibility study for pressure maintenance in the E-22 reservoir of the Ardjuna Field, Offshore Northwest Java. Results of a black-oil reservoir simulation study have been used as the basis for evaluation of pressure maintenance project alternatives.

Various operating schemes have been examined for their efficiencies in terms of recovery and cost. Alternatives considered ore:

  1. continued natural depletion,

  2. gas injection,

  3. water injection, and

  4. simultaneous injection of gas and water.

Production is derived from a combination of gas cap expansion, gravity drainage, solution gas drive, and water influx. The study concludes that gas injection into the gas cap will be the most efficient pressure maintenance program. Water injection only and/or simultaneous injection of gas and water would be either less efficient or economically unattractive.

Introduction

The E-22 reservoir is located offshore in 140 ft of water in the Ardjuna "E" field, Northwest Java - Indonesia (Figure 1). The field is located about 80 miles east-northeast of Jakarta and was discovered by Sinclair Exploration Company in 1968. The field was later put on production in 1971 by Atlantic Richfield Indonesia Inc. (ARII), the operator of the Offshore Northwest Java Contract Area, on behalf of its co-venturers and Pertamina.

Since its production start-up in 1971, 55 MMSTB oil or about 24% of the E-22 original oil in place has been produced. The reservoir pressure has declined from 1090 psig initially to about 590 psig in May 1983. Various pressure maintenance alternatives have been examined to arrest reservoir pressure maintenance alternatives have been examined to arrest reservoir pressure decline and to optimize the ultimate oil recovery of the E-22 pressure decline and to optimize the ultimate oil recovery of the E-22 reservoir.

This paper presents prediction results of the E-22 reservoir model using a three-dimensional, three-phase, black-oil simulator. Results of a comparable compositional model study are also briefly discussed. Conceptual design of each pressure maintenance alternative and comparative the investment requirements are described. The E-22 reservoir description and performance history are presented first.

RESERVOIR DESCRIPTION

The subject reservoir is located in the Main fault block of the E structure, which is a horst adjoined by the EQ-EZ and E-9 fault blocks (Figure 2).

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