PERTAMINA - IIAPCO has an expanding complex of offshore production PERTAMINA - IIAPCO has an expanding complex of offshore production platforms in the South-east Sumatra Contract Area of the Java Sea. One of platforms in the South-east Sumatra Contract Area of the Java Sea. One of the requirements for this complex is a treatment facility for water to be used in secondary recovery operations. Because of the water quality required, the water treatment system is substantially larger than that normally used offshore. Instead of constructing one or more platforms for the treatment system, a small coral Island named Pabelokan Island has been utilized for this purpose. Although the water treatment system is the primary reason for the base, other facilities were co-located to primary reason for the base, other facilities were co-located to centralize: electrical power generation, living quarters and recreation facilities, and facilities for storage and maintenance of offshore equipment. Future plans for the Island include a gal-liquids recovery system. This paper describes the Island facilities, and provides a case study in responsible planning and construction techniques in the development of a coral Island for use as an offshore base. The experience gained should be useful in the planning of other coral Islands for similar purpose.

Introduction

Development studies performed by PERTAMINA and the IIAPCO Division of Natomas International Corporation indicated the need for, and method of, secondary recovery operations in the Rama Field. Because of the weight of and the space required by, the water treatment system designed to supply the field, a land base was the most desired location. Pabelokan Island, a conveniently located and uninhabited island covered with coconut trees, was acquired in June 1980 as the site for the base. Pabelokan Island is not only near the center of IIAPCO's operational area, it also has adequate area for centralizing support facilities required by IIAPCO's multi-platform complex.

Pabelokan Island is one of the Thousand Island group shown in Figure 1, and Pabelokan Island is one of the Thousand Island group shown in Figure 1, and is located with respect to the IIAPCO platform complexes as shown in Figures 2 Figures 3 and 4 show the major facilities on the island which are described in the first part of this paper and include the following:

A water treatment and injection for the intake, filtering, and pumping of230,000 barrels of sea water per day to a subsea pipeline. A 42 MWelectrical power generating station, fueled by natural gas from RAMA "B",providing power to facilities on the island, and to all offshorefacilities, be means of a network of submarine power cables. Logistics support for the warehousing, repair, and transportation of materials. Quarters accommodations for 400 persons, inclusive of messing, recreation, and medical facilities. Island support facilities which include potable water, fire protection, security, communications, and sewage treatment.

Maintenance of the local environment was a prime consideration in the location and design of the island facilities. A large number of the original coconut palms were preserved. In addition, a variety of types of indigenous vegetation was transported to the island and planted, and Indonesian culture was reflected in the architecture of the buildings.

Soil studies were made before construction began. These studies showed that the subsoil consists largely of coral clumps embedded in soft clay, a factor to be considered in planning foundation for heavy construction. Environmental studies showed that before construction began, the coral sand fringing the island was in a state of "dynamic equilibrium". Although the sand shifted with seasonal winds and currents, there had been no long-term change in island shape or loss of sand over the edge of the reef. The environmental studies showed that special consideration should be given to any structures placed around the island perimeter. These structures include the wharf, piers, and the water treatment intake sump. Without these considerations there would have been excessive loss of beach sand and serious damage to the coral reef.

These soil and environmental problems are described in the second part of the paper.

ISLAND FACILITIES
Injection Water Treatment System

The water used for injection must meet rigid requirements. It must have a low count of suspended particles, it must not be corrosive, and to prevent clogging of the lines, marine organisms must be eliminated. An elaborate water treatment system was designed to meet these requirements. The injection water system draws seawater from outside the island coral reef, filters it, and treats it for marine organisms. The system has been designed to handle input water with up to 250 ppm of suspended particles. After going through the injection water treatment system, the water has a maximum of 0.2 ppm suspended particles, 0.05 ppm dissolved oxygen, and no significant biological activity. The treated seawater is pumped offshore through a submarine pipeline system for distribution to the injection wells. The water treatment system also provides water for a potable water supply and a backup saltwater fire protection system. Injection water system data are shown in Table 1. The injection water treatment system, which is shown in block diagram on Figure 5, consists of three subsystems:

  1. The seawater input subsystem provides source water and initial treatment. Just downstream of the input subsystem, a bypass valve routes the water either to the dissolved air flotation subsystem or the filter subsystem.

  2. The dissolved air flotation subsystem provides the equivalent of coarse filtering

  3. The filter subsystem provides fine filtering.

The injection water system receives the incoming seawater by gravity flow through a seawater intake 75 feet below sea level. The seawater intake is connected to a 36-inch diameter, 600-foot pipeline. This pipeline carries water to the concrete sump on the north side of the island.

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