APN Field Reservoir Gas Management, The Challenges of Development Optimization
Authors: Anantokusumo F. , Parhusip B. , Herbudianto S. , Do S.H. 
Published: December 2007

This paper presents the strategy of developing the APN gas reservoir. The APN gas reservoir is relatively shallow, 1450 feet subsea with an initial reservoir pressure of 730 psia. The APN structure is located in the North Seribu Platform area, approximately 50 miles Northeast of Jakarta in the ARCO Indonesia Inc. Offshore Northwest Java (ONWJ) Sea contract area. The gas deposit in the APN area is characterized as thin (15 to 70 feet) and widely dispersed over a large Pre-Parigi carbonate limestone area of 620 sq miles. The range of reservoir drive mechanism is from a weak peripheral water drive in the southeast region to an active bottom water drive in the northeast region of the APN area. The APN Pre-Parigi limestone has very good permeability of one Darcy and porosity of 38%.

It is a challenging task to commercially developed a thin and low pressure gas reservoir such as APN. Optimizing reservoir development while meeting gas demand is the critical factor for APN development.

A Multi Disciplinary Team (MDT) of reservoir engineers, geoscientists, production engineers and facility engineers was formed for the commercial development of APN. The MDT built a fullfield simulation model incorporating reservoir description data from the geoscientists, surface facility data from the facility engineers, and tubing hydraulics data from production engineers. The gridding of the full field model was based on the results from a single well model grid sensitivity study.

The APN Fullfield model gas and water production forecasts were used for studying optimum well locations and surface facility design and planning. APN development is planned to occur after the year 2000 (as local market demand dictates).

Introduction

ARCO Indonesia (ARII) has been operating the Offshore Northwest Java (ONWJ) concession since 1971. Up until September 1993, when the Indonesian State Electricity Company (PLN) awarded ARlI with its first gas sales contract, the emphasis was on exploiting the oil assets. Before getting the first gas sales contract the produced gas was used for fueling compressors and other platforms utilities. Currently ARII is contracted to deliver 260 MMSCFD with a 20% swing to Muara Karang for Power generation, 25 MMSCFD to Indonesian State Gas Company (PGN) for small to medium industries and 50 MMSCFD to Pertamina at Cilamaya for manufacturing fertilizer. These gas delivery contracts will expire in 2007. Developing gas assets such as APN, to meet the gas sales contract has become one of the highest priority in ONWJ development.

The gas development in ONWJ calls for sequential development of 19 different gas and oil fields over the life of the project. About 35% of the gas deliverability is from the non associated gas. APN's reserves is about 14% of the total non associated gas. APN is expected to deliver 50 MMSCFD to the sales point.

The APN structure is located in the North Seribu Platform area and it lies approximately 50 miles north of Jakarta, Java (see Figure 1). The closest gas network pipeline is 27 miles away at Papa Flow station. The water depth in the APN area is approximately 135 feet. P. 277^