Key Technologies for Enhance Gas Recovery of Large Low Permeability Heterogeneous Carbonate Gas Reservoirs

Abstract

AbstractSystematic enhance gas recovery (EGR) strategies are important technical means to improve the effect of low permeability carbonate gas reservoir and keep stable production in the middle- late development period. Lower paleozoic carbonate gas reservoirs of M gas field in Ordos Basin are one of typical low permeability reservoirs in China, which are located at the hub of the onshore natural gas network, with area nearly 10000 km2. As the crucial contributor of natural gas production, 1000 gas wells have been put into operation in total with accumulated gas production nearly 1000 × 108 m3 over the years. However, as the whole gas field enters the middle and late stage of development, the proved reserves have been basically used up, which are bringing the new problems such as serious unbalanced exploitation, large amount low pressure and low yield wells, rapid rate decline and water production. In the meanwhile, considering complex development of erosion trenches, strong horizontal and vertical heterogeneity and large scale of gas area, the application of existing EGR technologies are difficult. Therefore, due to characteristics and difficulties of geology and production performance in the middle and late development of these kind of gas reservoirs, systematic EGR technical strategies, as tapping potential reserves, reservoir classification, well pattern optimization and drainage recovery, which are mainly from improving the degree of reserve production and reducing the abandonment pressure two aspects, are putted forward. The innovated key technologies such as paleogeomorphology restoration based on dynamic monitoring, three-excellent reservoirs evaluation, well pattern optimization of multi-layer heterogeneous gas reservoirs, and optimization of working system of water producing gas wells based on early wellbore liquid loading identification have been formed. It is estimated that the reserves can be increased by 220.3 × 108 m3, gas production by 303.4 × 108 m3 and gas recovery by 6.8%. The research contents have guiding significance for the development and practice of similar gas reservoirs in China.KeywordsEnhance gas recoveryReservoirs classification and evaluationWell pattern optimizationLiquid loading identificationWorking systemLow permeability gas reservoir