Coiled Tubing Gas Lift Revives Dead Wells in South Pakistan

Abstract

This article, written by JPT Technology Editor Judy Feder, contains highlights of paper IPTC 19930, “Coiled Tubing Gas Lift: An Innovative Solution for Reviving Dead Wells in Southern Pakistan,” by Aizaz Khalid, Nestor Molero, SPE, and Ghassan Hassan, et al., Schlumberger, prepared for the 2020 International Petroleum Technology Conference, Dhahran, Saudi Arabia, 13-15 January. The paper has not been peer reviewed. Copyright 2019 International Petroleum Technology Conference. Reproduced by permission. This paper describes a coiled tubing gas lift (CTGL) technique successfully used to restart production from two pilot wells in a mature field in Pakistan that had been shut in since 2015. The project yielded production gains that resulted in a short payback period and verified that the technique represents an effective and economical solution to restart production in mature fields where conventional artificial-lift methods challenge well economics. The pilot results have encouraged the operator to further implement CTGL in Pakistan. According to the authors, suitable candidate selection, including data accuracy for nodal analysis and production forecast, and proper planning played fundamental roles in the project’s success. Introduction Exploration and production companies in Pakistan struggle with multiple challenges including pressure from regulatory bodies to increase oil and gas production to meet requirements of an energy-starved country in a period of historically low oil prices. With little new significant discovery, operators are challenged to produce economically from mature and declining fields. Several fields in south Pakistan have been forced to shut down because of uneconomical production rates. Most of the wells in these mature fields do not flow naturally because reservoir pressure is insufficient to overcome the hydrostatic column. Existing techniques have their own challenges, including very high associated costs. Realizing these challenges, the government of Pakistan recently prioritized developing mature fields and optimizing production in declining fields. Artificial-Lift-System Selection A detailed screening of candidate wells was carried out to identify innovative artificial-lift solutions. The deployment of gas-lift (GL) valves using coiled tubing (CT) soon emerged as the best option, offering the highest return in a cost-benefit analysis. CTGL is a rigless solution that enables setting GL valves at the required depth during any stage of a well’s life. CTGL strings can be installed without making permanent changes to already-existing wellbore tubulars, and make it easy to install in wells with either monobore or through-tubing completions. The technique allows gas to be injected through CT with production through the CT-to-tubing annulus. The system also is retrievable and replaceable when needed. Gas-lift mandrels (GLMs) and valves are added to the CT in a similar fashion to any traditional GL completion. A work-over rig is not required, and installation of the CT string also provides the opportunity to modify well cross-sectional flow areas, thus improving well hydraulics and production flow. Two flow configurations are possible: (a) tubing flow (i.e., production flow up the insert tubing string, gas injection down the newly created annulus) or (b) annular flow (i.e., gas injection down the insert string, production flow up the newly created annulus between parent tubing and the CT insert string).