Extracting Lessons Learned of 35 Water Shut-off Jobs in Mature Fields to Improve Success Ratio of Water Shut-off Job

Abstract

Abstract Increasing water production in a mature field means an increasing burden of operating cost because that water production must be processed and treated before it is discharged or injected1. One common solution to overcome this problem is conducting water shut-off jobs which consist of mechanical and chemical water shut-off. Mechanical water shut-off is preferred to be carried out over chemical water shut-off because of lower costs. An example of mechanical water shut-off is using cup packer, squeezing-cement, and reperforating over a shorter interval. In Central Sumatra, there were approximately 35 mechanical water shut-off jobs executed from 2010 – 2012. Those jobs were varied from mature fields having different geological conditions, recovery mechanisms, drive mechanisms, and operating-rate conditions which may be influencing the rising of current oil water contact (COWC). Based on the completed water shut-off jobs, some lessons learned were to have perforation interval above current oil water contact (COWC), have good historical water shut-off performance at surrounding wells, have good production performance at surrounding wells, have good structural location, and have by-pass oil identified from CO/RST log if it is below COWC. Those lessons learned will be applied to upcoming water shut-off candidates. This paper further explains of some lessons learned which will be useful for selecting candidate of water shut-off jobs and compares the result of water shut-off jobs after implementing lessons learned which significantly increased its success ratio and oil gain.