Thru-Tubing Isolation and Perforating in Large Casing Diameter

Abstract

Well-11 produced gas from the Kujung-2 and Kujung-3 (K-2 and K-3) carbonate formation of Ujung Pangkah Field. Even though it was producing from the biggest reservoir zone, the well had to be shut in due to watering out in two years. High molecular weight polymer was injected to shut off the water zone but with no success. The work over job aimed to isolate the watered out zone (K-2 and K-3) and to access K-1 formation which had never been produced. This rigless operation was carried out on an-manned production platform. Thru-tubing isolation inside the 9-5/8-in. casing was the biggest operational hurdle of the project. The challenges addressed were; high expansion ratio of the inflatable plug; uncertainty of the casing's condition due to the sour gas environment; and a cement bailer operation to permanently isolate the formation. Perforating was successfully executed in the selected zone using deep-penetrating shaped charges. The results were satisfactory and the well produced three times more gas than expected. This paper presents the strategies, challenges and the lessons learned for zonal isolation using a thru-tubing inflatable bridge plug combined with cement and the perforating of the K-1 formations to optimize the gas recovery factor.