Research and Practice of UGS Construction In Low Permeability and Sulfur-bearing Gas Reservoir

摘要

With a rapid growth of natural gas industry in China, due to tremendous seasonal fluctuations in demand, the peak-shaving and gas supply in winter has become increasingly severe. Hence, it has been carried out a large scale of UGS construction in China since 2010. Among these constructions, PetroChina Changqing Oilfield Company (PCOC), located in Ordos Basin, is a priority of UGS planning and construction. However, the gas reservoirs developed in Ordos Basin are characterized by low permeability, strong heterogeneity, containing hydrogen sulfide, and without obvious sealed boundary. As a result, all these lead to poor resource for qualified UGS construction. To find a solution for these challenges, PCOC made a thorough research on carbonate reservoirs in Jingbian Gas Field, and conducted a system of the whole life-cycle evaluation, protection and monitoring for the sealing performance, selected horizontal wells to inject and withdraw, enhanced the injection-withdrawal capacity by optimizing horizontal section trajectory design, precise geosteering, coiled tubing jet acidizing, as well as established numerical simulation model of UGS acid gas components to predict the variation of acid gas components content during multi-cycles operation, and clarified corrosion type of well string to select appropriate ones and anti-corrosion techniques. As a pioneering UGS in low permeability and sulfur-bearing reservoir in the world, S224 UGS, mainly using horizontal wells for injection and withdrawal, has been successfully operated based on seven years of research and practice. This UGS, with 260 million m~3 working gas volume currently, is a good case which indicates that, although due to unique challenge, even with poor resource for qualified UGS construction, in China, it still has great potentialities to build UGS in low permeability and sulfur-bearing gas reservoirs, when it is adopted appropriate and suitable countermeasures.