This paper will describe the successful application of cement packers in Offshore Northwest Java Sea (ONWJ) field to recover by-passed reserves that are located above the production packer. Previously, conventional completion techniques required a workover to re-complete these new zones. However, due to their marginal reserves or the well still has good production from existing zones (ex: in dual completion case where long string is still a good producer while short string is already shut-in), a workover is not a good option to recover these by-passed zones. A new treatment technique in ONWJ field, Indonesia, has been developed to re-complete and treat these zones that are located above the production packer without pulling out completion strings. Isolation of potential zones is accomplished by cementing in the tubing-casing annulus above the production packer. The cement above the zone replaces the production packer and conventional perforating is then used to complete the well.
The advantages of this technique are: inexpensive (no rig required), no need to wait for the well to achieve economic limit rates before recovering the zones, and – most importantly – it still allows access into the lower completions. On the other hand, the disadvantages of this technique are: less gun penetration (has to penetrate tubing-cement-casing-cement-formation), and workover/sidetracking below packer is difficult to carry out once the packer has been covered by cement.
To date, a total of 7 wells have been reactivated using this technique to recover the zones/reserves. The jobs have been done successfully in both single and dual completions. The average cost was only 20%–60% of conventional workover jobs and savings of up to US$ 400,000 have been achieved. The production results have also been encouraging. These successful results have brought new opportunities for reactivating many more shut-in wells with by-passed reserves that are economically marginal.
The Offshore North West Java Production Sharing Contract (ONWJ PSC) area is located off of the North Coast of Java Island in Indonesia (see Fig. 1). The contract area is about 18,000 sq-km. The first exploration well was drilled in 1967 while the first production occurred in 1971. The ONWJ PSC is divided into four main areas: Ardjuna, Arimbi, Bima and North West Corner. It consists of about 50 fields, most of them are oil, distributed in three productive formations, Parigi, Upper and Lower Cibulakan. Throughout its 30 years of production history, 13 flow stations, 150 production platforms, 700 wells with 1013 production string and more than 1,000 miles of sub-sea pipelines have been built in a sea depth of up to 40 meters. Gas lift is the primary artificial lift method in this area.
ONWJ reached its peak crude production rate of 180,000 BOPD in 1984 but now it has declined to around 56,000 BOPD. The continuous decline of crude production is a challenge to the company goal of being a low cost offshore operator.
Only 43% of the strings are currently still producing while the rest of them have been shut in because production has reached economic limit rates or have watered out. Re-evaluations of these shut-in wells have identified potential reserves above the production packers. Previously, a conventional workover job was required to recover these zones. However due to marginal reserves a workover is not an option to develop these zones. In some dual completion cases where one of the strings is still producing, a workover can not be done without sacrificing the other strings. This condition has challenged the company to find a better technique to recover those reserves and re-activate shut-in wells without sacrificing production in the other strings/wells.