Almost all the wells in the Offshore North West Java (ONWJ) field penetrate multi-layer reservoirs. To accommodate reservoir management issues, most of these wells were therefore completed in multiple packer completions (dual or single string with multiple packer). As the field is getting mature, more wells are becoming wet and consequently more wells are dying due to water encroachment. Therefore, remedial actions to revive dead wells play an important role to maximize the revenue. To address this issue, thru-tubing cement squeeze and polymer squeeze using coiled tubing have proved to be efficient methods to reduce water production by isolating watered out zones in the ONWJ field.
However, the operation of this job can be more complicated when done in multiple packer completion or in dual completion cases, especially when the tubing has leaks in order to avoid the cement or polymer from penetrating other places or productive zones. In several cases, the condition of old tubing that has experienced deformation (buckling/collapse) has made the task even more challenging. Therefore, treatment strategies must be designed carefully for successful cement/polymer placements into the target zone without affecting production from the other string or zones.
From 1999 to 2003, a total of 36 thru-tubing zonal isolation & water shut-off jobs utilizing coiled tubing were done with a high degree of success, although in many cases the tubing had leaks and mechanical problems. Several methods were used and modified to ensure proper cement or polymer placement. Through the use of the innovative "cement packer" technique and inflatable packer, the jobs were accomplished successfully. The coiled tubing has proven to be an effective solution to deal with well conditions in the ONWJ field.
This paper will also discuss three case histories, with each case representing different operational challenges.