Coiled Tubing Gas Lift: An Innovative Solution for Reviving Dead Wells in Southern Pakistan

Abstract

In southern Pakistan, most wells in mature fields do not flow naturally and require delivery of supplemental energy into the wellbore through an artificial lift system. The existing portfolio of techniques, however, faces technical and economic challenges. Operators have tried numerous methods of deliquification such as soap injection, jet pumps, electrical submersible pumps, and conventional gas lift (GL). Those solutions differ in methodology and efficiency, but they unfortunately have failed either technically or economically in Pakistan. Because reviving dead wells is key to maximizing production with the most efficient and cost-effective method in Pakistan, a detailed screening of candidate wells was carried out to identify innovative artificial lift solutions. The deployment of GL valves using coiled tubing (CT) soon emerged as the best option, because it offered the highest returns in a cost-benefit analysis. Coiled tubing gas lift (CTGL) is a rigless solution that enables setting GL valves at the required depth, during any stage of a well life. It allows gas to be injected through CT with production through the CT-to-tubing annulus. This technology is also retrievable and replaceable when needed. Two pilot wells, that had been shut in since 2015, were selected from four shortlisted candidates through nodal analysis. Each system consisted of one CT string with multiple stations of unloading and orifice valves, spaced out at depths engineered to maximize each well’s productivity. In addition to a GL valve, each station included two CT external connectors and one self-aligning connector, which enabled efficient and safe connection between both CT ends during the deployment of the CTGL station. Additionally, specific CT pressure control equipment and wellhead adapters were used to secure and hang the CT string in the production tree and provide connection with the gas injection facilities at the surface. The first installation was conducted in a vertical well originally completed 4 1/2-in. monobore, deploying 1 1/2-in. CT string with four CTGL stations. The second installation was performed with 1 1/4-in. CT and five CTGL stations in a well originally completed with 7-in. liner and 2 7/8-in. production tubing. The wells were commissioned using existing surface infrastructure and were unloaded smoothly until the production stabilized at optimum rates near 420 B/D and 325 B/D respectively. This innovative artificial lift technique represents an effective and economical solution to restart production in mature fields where conventional artificial lift methods challenge well economics. This approach greatly rests on a thorough candidate selection process. The design and installation of two new CTGL systems was a first in the Middle East region and helped identify numerous best practices and lessons learned, which will speed up implementation of the methodology in other parts of the world.