Development Strategies of Soft-Friable Carbonate Gas Reservoirs Through Horizontal Open Hole Gravel Packed Completions: APN Field - Offshore West Java
Authors: Mansur Achmad , Susilo Yoliandri , Wulan Retno Sri , Hendra Yasri Satria , Sudarmono _ , Ramdan Dadan 
Published: February 2016

A gas-bearing carbonate reservoir was found spread over the Offshore West Java (OWJ) field, Indonesia. A new area in the field, the APN area, has been successfully developed recently to recover gas from this reservoir. The APN reservoir is a shallow (~1500 ft), low pressure (~700 psig) carbonate reservoir with 70 ft net pay, comprised of foraminiferal grainstones and packstones, having excellent reservoir quality with average porosities of 38% and permeabilities of up to 1000 md. Unlike any other carbonate reservoir in OWJ, the carbonate reservoir in this area is very weak. An evaluation of solid production potential suggested that the well should be completed with solid control since the formation rock has failed and there is no allowable drawdown pressure. It would require compliant borehole support and a large inflow surface area to minimize drawdown. It also needed to be screened to mitigate solids production. A Horizontal Open Hole Gravel Packed (HZOHGP) was chosen as the optimal solution for particle size range, cost and long term integrity.

Five horizontal wells were drilled and successfully completed with a 1,000 ft open hole section and 7-inch production tubing. The gravels were placed using circulating pack (alpha-beta wave) technique. All the wells were started-up smoothly and each well could deliver 40 MMCFD, which is quadruple conventional well production. No solid production was observed.

This paper discusses the design phase, execution, start-up and results. It also shows how, through integrated multidiscipline team work, the previously marginal APN field could be developed with good economic results using the implementation of several new technologies.

Background

The APN field was discovered in 1968 with the A-1 well by ARCO. It is situated within the Offshore North West Java PSC (ONWJ) of which BP is the current operator. The APN Development was sanctioned in April 2004, thirty six years after the field was discovered. The field was previously categorized as economically marginal, but through multi-dicipline evaluations and applications of the right technologies, the field has been turned into a world class field with good economic margins.

The APN consists of three separate gas fields (water depth 45m) in the northern area of the ONWJ PSC (Production Sharing Contract). It is a remote field located approximately 70 km north of Jakarta and 40–50 km north of the nearest infrastructure at Papa flowstation.

Figure 1 - ONWJ Field Location

This asset is strategically located to supply cost effective gas to PLN's (Indonesia's nationalized power generator) power plants in the Jakarta bay. ONWJ is in its late life and the strategy is to efficiently harvest the remaining oil reserves while sustaining gas production. Significant compression and export infrastructures exist that enable BP to produce the remaining gas reserves with quality margins.

Five horizontal wells were drilled to develop the reserves from this field. The project achieved first gas on August 17, 2005 and is now successfully in production, delivering 40% of the gas production in West Java underpinning the assets and economic viability.