Abstract

Development of the Central Luconia gas fields, located offshore Sarawak, started in 1982. To data three gas fields have been developed, E11, F23 and the third and largest gas field, F6, which came on stream in January 1987. The daily production rate averages some 1000 MMscf/d.

The gas is delivered via a single 36" trunkline from E11 to the Malaysian LNG liquefaction plant for the Manufacture of LNG at approximately 6 million tonnes per year for a period of 20 years. Gas is also distributed to the ASEAN Bintulu Fertilisation plant for the production of urea and ammonia, and to Sarawak Electricity Supply Corporation for power generation.

This paper describes the 3D simulation study that has been carried out for the F6 field which forms the basis for the development planning of the field. The plan proposed a total of ten producer and one observation well to be drilled from the drilling platform F6DP-A located near the crestal part of the field.

Despite the large reservoir areal extent of about 168 km2, it is expected that the field can be adequately drained from a single platform with ten producers.

The main uncertainties which may affect the field performance are the transmissibility of a tight argillaceous layer which may separate the gas bearing part of the field into two zones and the possibility of water drive. The likely impact of these uncertainties on the development plan and gas recovery has been addressed in the simulation study.

Taking the above uncertainties into consideration, recovery factors are estimated to be between 61% and 75%.

The Central Luconia province is situated some 100 miles offshore Sarawak. Malaysia in 230 - 290 ft of water (Fig. 1). During the late 1960's, Sarawak Shell Berhad (SSB) carried out exploration drilling in Central Luconia. Numerous gas accumulations were found in carbonate buildups and the gas reserves were evaluated to be large enough for a viable LNG scheme. Proposals were presented to the Malaysian government in 1971, which eventually led to the formation of Malaysian LNG Sendirian Berhad (MLNG) in 1978. Petronas (the Malaysian national petroleum company) took up 60% equity in this venture, while Shell Gas B.V. and Mitsubishi Corporation of Japan took up 17.5% each, and the State of Sarawak 5%.

Central Luconia gas is further distributed to the ASEAN Bintulu Fertiliser plant for the production of urea and ammonia, and to Sarawak Electricity Supply Corporation to generate power for local use.

The results of seismic surveys taken during the mid - 1960's indicated the possibility of large carbonate structures in Central Luconia. Exploration drilling in 1968 confirmed the existence of these carbonate structures. The first significant gas accumulation was discovered by well F6.1X in 1969. Exploration drilling in 43 carbonate structures within the period 1968-1975 led to the discovery of 20 gas accumulations, of which 10 contained significant quantities of non-associated gas.

Appraisal drilling in the five largest gas fields, E11, F23, F6, ES and F13, which are committed to the LNG project. was completed before end 1978 to better define geology, reserves, productivities and wellstream compositions.

E11 was the first gas field to be developed, being closest to shore. By 1982, the installation of offshore platform and associated facilities, and the 78 miles long 36" trunkline to shore was completed.

P. 849^

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