First Application of Water Shut Off Method from Perforated Shale Zone at Gravel Pack Section: Offshore Case History from Bekapai-Mahakam Field, Indonesia
Authors: Rahmadhani M. I. , Supratman M. R. , Suprapto E. , Kurniawati P. S. , Kusuma R. , Kristanti F. Y. , Surahman A. , Fairuz N. D. , Ramadhan A. , Hidayat D. 
Published: August 2024

Abstract
The Mahakam Block in East Kalimantan, Indonesia, has been producing oil and gas since the mid-1970s, now in its mature phase. Numerous wells installed with gravel pack (GP) completions dot the landscape of Mahakam. Given the massive history of water production, a reliable water shut-off (WSO) strategy is imperative to revive these wells, particularly those with target of unperforated reservoirs behind the GP zone. Squeeze cementing through a perforated sliding sleeve door (SSD) was once a common WSO method at the GP zone. However, due to concerns such as the need to damage the sleeve and integrity of GP completion, this method declined in preference. An alternative approach involving squeeze cementing from perforated shale zones poses a risk of cement contamination inside the annulus. Hence, for GP completion, the first application of annulus cementing with a circulation method as a WSO strategy is set for implementation.
The B-X well, with a 6 GP zones completion and gas lift system, has been producing since early 2015, with cumulative oil production exceeding 1 million barrels of oil (Mbo). The primary target lies within unperforated reservoirs behind GP zone No. 3. The open reservoir within GP zone No. 3 is currently inactive and has a significant history of water production. Given the risk of cement contamination and micro-annulus formation considering the close distance of 85-feet between these reservoirs, a circulation cementing method is preferable to ensure the cement integrity, using inflatable packer & plug for bottom hole assembly and sand consolidation (SCON) due to the high sand risk. Preparation prior cementing have been performed, such as pulsed neutron logging (PNL), close SSD, and temporary plugging prior cementing. Despite three attempts using tubing punchers, neither injectivity nor circulation was observed at the surface. Injectivity was achieved after perforating the shale zone, indicating previous tubing puncher failures. Different tubing puncher configurations were attempted to create the bottom circulation hole, but still no return was observed at the surface. Consequently, the circulation method was changed to squeeze method. Due to the low injectivity result from the injectivity test, the squeeze method was done by displace the cement inside the tubing using coiled tubing (CT) string, then squeezing the cement via CT flow cross while maintaining wellhead pressure during cement thickening time. Cement was not fully displaced to the annulus based on pumping schedule; thus, drill out was required to clear restrictions until perforation target. However, drill out made no significant progress in depth and got overpull, prompting tubing clearance using slickline, which found a half-circle marking suspected of tubing parting. Due to this finding and narrow operational window, the operation has been suspended for the next campaign.
This paper assesses the WSO strategy at GP completion with significant water production and unperforated reservoirs target behind the completion. Both successful and failed technology applications in this operation will be reviewed, offering recommendation, and lessons learned for future endeavors.