Non-Conventional Engineering Approaches to Effectively Shut Off Highly Deviated Gas Producer Wells in One of the World Oldest Gas Producers: Andaman Sea Experiences
Authors: Venugopalan Pravin Nair , Safwan Wan Mohamad , Min Htun Yin , Winn Hset , Abdul Ghani Siti Aisyah , Yahaya Fadzil , Sy M Shahril Sy Ahmad , Kamal Khairil Anuar , Singh Kelvinder , Yong Nigel , San Wong Kai , Kalidas Sanggeetha 
Published: February 2023

The aim of this project is to reduce the water cut in highly deviated well and subsequently enhance gas production of an offshore gas producer. Well A is located in a mature field in the Andaman Sea and contains 10% CO2 and 400 μg/m3 mercury. Due to the high-water cut, the well was struggling to meet its daily gas nomination, and any further decline in production would reduce the national daily gas supply, thus leading to penalties to the operator if not tackled properly.

With limited historical data acquisition opportunities at the location, adjacent well performance and well test data were correlated to pinpoint the problematic zones that were contributing to the high-water production being shut off. The well construction posed several challenges for installation, as severe completion ovality and minimum internal diameter (ID) at landing nipple restricted conventional plug application. Elastomers with high expansion capability were made-to-order to fully seal around the casing liner ID for effective downhole barrier isolation. Furthermore, the presence of CO2 content in produced gas may potentially cause elastomer swelling and embrittlement, leading to downhole failure. Guided by the lessons learned from previous operations, a structured engineering approach was undertaken to select a bridge plug with a customized deployment method to ensure the successful zonal shut-off operation for Well A.

A high expansion mechanical plug (&gt;30% ratio) dressed in customized swellable elastomers was selected instead of conventional inflatable plugs to tackle swelling and embrittlement concerns due to high CO2. The elastomer was required to meet the gas-tight requirement without the need to spot cement above it and should be economically viable. The plug was to be deployed through coiled tubing to enable activation of the plug mechanism via the hydraulic setting tool and cater for contingencies post-plug setting such as nitrogen kickoff. During execution, the water production layers were successfully shut off within the planned duration while meeting safety objectives. Upon flowing the well, the instantaneous gas gain increased by 190% and WGR (Water Gas Ratio) reduced by 70%, allowing production to flow without any unplanned shutdown. Despite the successful operation, it is highly recommended that production logging is performed post-operation to confirm the state of the downhole condition.

Dealing with a mature well with declining production due to water loading is a problem for any operator. Every solution must lead to cost savings & able to prolong the production life of well. As iterated above, zone shut-off using the high expansion mechanical plug was able to enhance production from Well A, thus meeting the gas nomination supply. This paper will help other operators who are experiencing the same problem and drive replication efforts.