Abstract

The Dulang field discovery wells were drilled by PETRONAS Carigali Sdn Bhd, (Carigali) and Esso Production Malaysia, Inc., (EPMI) during 1981 - 82 in thei.r respective portions of the field. Results of seismic interpretation and Subsequent appraisal drilling, revealed an extensive, eastwest trending, complexly faulted anticline plunging westwards. It was recognized early that the optimal field development plan must be predicated on an integrated reservoir description spearheaded by the acquisition of J-D seismic data to accurately define the structure. Early data indicated that both fluid and pressure communication existed between the EPMI and Carigali sections of the field. Unitization was inevitable and the agreement was reached in 1998. Carigali was appointed operator of the Unit Area.

This paper describes the application of an integrated multidisciplinary approach to the development of the Dulang oil field offshore Peninsular Malaysia. The staged development of this complex field, with two of the planned total four platforms currently onstream, is an innovative approach to offshore development, involving synergism of disciplines, and placed a premium on flexibility in approach. The practical issue addressed was the full utilisation of available information and expertise, involving the full range of geophysical, geological, and engineering expertise, to ensure optimum field development onschedule and on budget.

The major issue in field development at the Dulang oil field was that of reservoir description. Seismic interpretation, even with a high degree of well control, was complicated by the presence of shallow gas and dense faulting continuous geological reviews were able to resolve reservoir structure and lithology beyond that provided by applied geophysics. Engineering analyses of pressure data identified fluid contacts and established interwell continuity. Uncertainties in petrophysical properties are being addressed by a special drilling and core recovery program involving the use of bland water-base and bland low-toxicity oil-base muds, advanced reservoir mechanics analysis and integrated log analysis programs. An integrated reservoir study of the Dulang field is ongoing, and comprises comprehensive analyses of the geology, petrophysics, geophysics, reservoir engineering and production engineering aspects of the field.

The staged development of the field has been justified by the reserves potential. The original oil-in-place has been estimated at 685 MMSTB and 495 BSCF, including the recent discovery of oil in the Lower D reservoirs, which were previously appraised as non-associated gas. The uncertainties associated with, and the caution applied to parameters used in the resource evaluation, compel a conclusion that the current reserve estimates may be conservative optimized depletion strategies developed through reservoir description and numerical simulation studies have formed the basis for the staged development concept now in use of the Dulang field.

Introduction

The Dulang field is located in the South China Sea, 130 km. offshore Kuala Terengganu, on the east coast of Peninsular Malaysia, in water depths of about 76 meters (Fig. 1). The f1eld discovery wells were drilled by. PETRONAS Carigali sdn Bhd, carigali and Esso Production Malaysia, Inc, EPMI during 1981/82, in their respective portions of the field.

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