Downhole Gas Compression: A New Artificial-Lifting System for Gas Wells

Abstract

This article, written by Assistant Technology Editor Karen Bybee, contains highlights of paper SPE 121815, "Downhole Gas Compression: World's First Installation of a New Artificial-Lifting System for Gas Wells," by M.T. Di Tullio, SPE, S. Fornasari, and D. Ravaglia, Eni SpA E&P Division, and N. Bernatt, SPE, and J.E.N. Liley, SPE, Corac Group plc, originally prepared for the 2009 SPE EUROPEC/EAGE Annual Conference and Exhibition, Amsterdam, 8-11 June. The paper has not been peer reviewed. Downhole gas compression (DGC) is a new artificial-lift technology designed specifically for natural-gas wells and is an as yet unrealized opportunity within the upstream gas industry. The technology offers the opportunity to increase production by 30 to 50%, improve reserves significantly, and delay the onset of liquid loading. Although it can be used at any time during the life cycle of a gas asset, it will find particular favor during the decline phase. Introduction The upstream gas industry often is faced with the challenge of selecting an optimum artificial-lift system from various alternatives available for gas-well production enhancement. These challenges become more complex with increasing dynamic changes in well flow characteristics over the life of the well. Application of DGC technology in suitable wells offers value for the following reasons.Acceleration of early production and extension of production plateau in new gas developments.Cost-effective rejuvenation of mature gas reservoirs characterized by low reservoir pressure and liquid accumulation in wells.Improvement of gas-well production and maximization of recovery factor from gas reservoirs with low environmental impact.Identification of incremental reserves and for monetization of stranded gas. As part of an ongoing development through a joint-industry program, the first field trial of the new technology was conducted in an onshore gas well. The program has been completed in phases, including the design, building, and testing in a full-scale flow loop that closely replicated downhole conditions. The prototype has been tailored to suit the expected gas-flow range, composition, and condition of the selected field-trial well. Fig. 1 shows an internal view of one of the three compressor modules, with the gas path indicated in red. Why Compress Gas Downhole Operators of a producing asset always are seeking to maximize its value. In natural-gas fields, optimum gas production at low intervention cost and frequency is the ultimate objective in gas-well production management. To maximize production, the flowing bottomhole pressure (FBHP) should be kept as low as operationally possible. There are many challenges to achieving this objective.