贵州省过饱和煤层气藏产气规律研究
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摘要
基于过饱和煤层气藏的排采过程兼具游离气与吸附气的生产特征,为弄清此类过饱和气藏产气特征的内在原因和机理,探索影响其高产、稳产的主控因素,为后期此类气藏的勘探选区、井位部署、压裂及排采工程设计提供指导,通过深入剖析游离气与吸附气的产出机理,将等温吸附曲线划分为2种经典类型,并结合现场生产实例,系统阐述了各自的产出特征及产能主控因素。研究结果表明:煤储层的等温吸附特征决定吸附气快速解吸释放的时间及储层导流能力的变化趋势,从而影响压力降的传播及游离气与吸附气的有效产出;过饱和煤层气藏具有排采初期见气快,产气增长快的特征,中后期的稳产气量、稳产期及衰减速率主要取决于产层的等温吸附特征、煤体结构及排采制度的合理性,其中等温吸附特征为主控因素。
The discharge process based on supersaturated CBM reservoirs has the characteristics of production of free gas and adsorbed gas.In order to understand the inherent causes and mechanisms of gas production characteristics of such supersaturated gas reservoirs,and explore the main controlling factors affecting high yield and stable production,and provide guidance for the exploration and selection of wells,well location,fracturing and drainage design of such gas reservoirs,the production mechanism of free gas and adsorbed gas are deeply analyzed and the isothermal adsorption curves are therefore divided into two classic types. Combining with the on-site production examples,their output characteristics and capacity control factors are wholly described respectively. The results of the study show that the isothermal adsorption characteristics of coal reservoirs determine the time of rapid desorption of adsorbed gas and the trend of reservoir diversion capacity,thus affecting the propagation of pressure drop and the effective output of free gas and adsorbed gas. The supersaturated CBM reservoir has the characteristics of rapid gas production and fast growth of gas production in the early stage of drainage. The stable gas production,stable production period and decay rate in the middle and later stage of drainage mainly depend on the isothermal adsorption characteristics of the production layer,the structure of coal and the rationality of the drainage system,among which the isothermal adsorption characteristics are the main controlling factor.
The discharge process based on supersaturated CBM reservoirs has the characteristics of production of free gas and adsorbed gas.In order to understand the inherent causes and mechanisms of gas production characteristics of such supersaturated gas reservoirs,and explore the main controlling factors affecting high yield and stable production,and provide guidance for the exploration and selection of wells,well location,fracturing and drainage design of such gas reservoirs,the production mechanism of free gas and adsorbed gas are deeply analyzed and the isothermal adsorption curves are therefore divided into two classic types. Combining with the on-site production examples,their output characteristics and capacity control factors are wholly described respectively. The results of the study show that the isothermal adsorption characteristics of coal reservoirs determine the time of rapid desorption of adsorbed gas and the trend of reservoir diversion capacity,thus affecting the propagation of pressure drop and the effective output of free gas and adsorbed gas. The supersaturated CBM reservoir has the characteristics of rapid gas production and fast growth of gas production in the early stage of drainage. The stable gas production,stable production period and decay rate in the middle and later stage of drainage mainly depend on the isothermal adsorption characteristics of the production layer,the structure of coal and the rationality of the drainage system,among which the isothermal adsorption characteristics are the main controlling factor.
引文
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[2]李小彦,司胜利.我国煤储层煤层气解吸特征[J].煤田地质与勘探,2004,32(3):27-29.LI Xiaoyan,SI Shengli.Coalbed gas desorption characteristics of coal reservoir in China[J].Coal Geology&Exploration,2004,32(3):27-29.
[3]刘世奇,赵贤正,桑树勋,等.煤层气井排采液面-套压协同管控-以沁水盆地樊庄区块为例[J].石油学报,2015,36(1):98-101.LIU Shiqi,ZHAO Xianzheng,SANG Shu Xun,et al.Cooperative control of working fluid level and easing pressure for coalbed methane production:a case study of Fanzhuang Block in Qinshui Basin[J].Acta Petrolei Sinica,2015,36(1):98-101.
[4]陈振宏,王一兵,孙平.煤粉产出对高煤阶煤层气井产能的影响及其控制[J].煤炭学报,2009,34(2):231-232.CHEN Zhenhong,WANG Yibing,SUN Ping,Destructive influences and effectively treatments of coal powder to high rank coalbed methane production[J].Journal of China Coal Society,2009,34(2):231-232.
[5]王运海.延川南深部煤层气井排采制度研究[J].煤炭科学技术,2018,46(6):132-137.WANG Yunhai.Study on drainage and production system of deep coalbedmethane well in South Yanchuan Block[J].Coal Science and Technology,2018,46(6):132-137.
[6]屈绍忠,林建东.浅谈煤层气与游离气共同开发新思路[J].中国煤炭地质,2013,25(2):64-65.QU Shaozhong,LIN Jiandong.A discussion on new ideas in CBMand free gas joint exploitation[J].Coal Geology Of China,2013,25(2):64-65.
[7]梁宏斌,林玉祥,钱铮,等.沁水盆地南部煤系地层吸附气与游离气共生成藏研究[J].中国石油勘探,2010,14(2):72-77.LIANG Hongbin,LIN Yuxiang,QIAN Zheng,et al.Study on coexistence of absorbed gas and free gas in coal strata south of Qinshui Basin[J].China Petroleum Exploration,2010,14(2):72-77.
[8]陈振宏,王一兵,郭凯,等.高媒阶煤层气藏储层应力敏感性研究[J].地质学报,2008,82(10):1390-1394.CHEN Zhenhong,WANG Yibing,GUO Kai,et al.Stress sensitivity of high-rank coalbed methane reservoir[J].Adta Geologica Sinica I,2008,82(10):1390-1394.
[9]孟艳军,汤达祯,李治平,等.高煤阶煤层气井不同排采阶段渗透率动态变化特征与控制机理[J].油气地质与采收率,2015,22(2):66-70.MENG Yanjun,TANG Dazhen,LI Zhiping,et al.Dynamic variation characteristics and mechanism of permeability in highrank CBM wells at different drainage and production stages[J].Petroleum Geology and Recovery Efficiency,2015,22(2):66-70.
[10]孟艳军,汤达祯,许浩,等.煤层气解吸阶段划分方法及其意义[J].石油勘探与开发,2014,41(5):614-617.MENG Yanjun,TANG Dazhen,XU Hao,et al.Division of coalbed methane desorption stages and its significance[J].Petroleum Exploration and Development,2014,41(5):614-617.