基于分形理论的高煤阶煤层气储层气-水相渗计算方法及应用
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摘要
通过理论推理和室内实验,研究了利用分形理论计算高煤阶煤储层气-水相渗的方法,结果表明:煤样孔、渗物性越好,最大进汞饱和度越高,两相渗流区越大,等渗点水相饱和度越小;通过分形理论利用毛管压力曲线计算煤岩气-水相渗曲线是可行的,实验样品相渗曲线的计算值与实验值非常接近;分形维数主要影响水相渗透率,分形维数越大,水相渗透率曲线越向右偏移,且气水两相等渗点饱和度越大。这表明,煤储层分形维数越大,水相渗流难度越大,应控制井底流压在解吸压力以上,避免两相流出现,充分排水,扩大煤层气井降压、解吸面积。
This paper studies the calculation method of gas-water relative permeability using fractal theory, through theoretical analysis and laboratory experiments. The results show that the higher the porosity and permeability of coal sample, the higher the largest mercury saturation, the larger the two phase flowing area, and the smaller the isosmotic water-gas saturation. It is feasible to calculate gas-water relative permeability curves of coal rock by using capillary pressure curve through fractal theory. The fractal dimension mainly affects the relative permeability of water phase. The larger the fractal dimension is, the more the water phase permeability curve deviates to the right section and the greater the saturation of the isosmotic water-gas saturation points.This suggests that the bigger the fractal dimension of coal reservoir, the greater the difficulty of water seepage. So the bottom hole flowing pressure should be controlled above the desorption pressure to avoid two phase flow which can expands the de-pressured and desorption area.
This paper studies the calculation method of gas-water relative permeability using fractal theory, through theoretical analysis and laboratory experiments. The results show that the higher the porosity and permeability of coal sample, the higher the largest mercury saturation, the larger the two phase flowing area, and the smaller the isosmotic water-gas saturation. It is feasible to calculate gas-water relative permeability curves of coal rock by using capillary pressure curve through fractal theory. The fractal dimension mainly affects the relative permeability of water phase. The larger the fractal dimension is, the more the water phase permeability curve deviates to the right section and the greater the saturation of the isosmotic water-gas saturation points.This suggests that the bigger the fractal dimension of coal reservoir, the greater the difficulty of water seepage. So the bottom hole flowing pressure should be controlled above the desorption pressure to avoid two phase flow which can expands the de-pressured and desorption area.
引文
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[2]徐欣,徐书奇,邢悦明,等.煤岩孔隙结构分形特征表征方法研究[J].煤矿安全,2018,49(3):148-150.
[3]江丙友,林柏泉,吴海进,等.煤岩超微孔隙结构特征及其分形规律研究[J].湖南科技大学学报(自然科学版),2010,25(3):15-18.
[4]袁哲,刘鹏程,冯高城.分形维数定量表征煤岩储层非均质性[J].中国科技论文,2015,10(9):1010-1013.
[5]贾慧敏.高煤阶煤岩孔隙结构分形特征研究[J].石油化工高等学校学报,2016,29(1):53-56.
[6]杨露,冯文光,李海鹏.毛管压力曲线与相渗曲线相互转化的分形实现[J].断块油气田,2008,15(2):64.
[7]何坤.基于分形模型油水相对渗透率计算的新方法[J].科学技术与工程,2012,27(12):7058-7060.
[8]赵明国,王海栋,贾慧敏,等.考虑最大与最小孔隙半径比的相渗曲线计算模型[J].数学的实践与认识,2016,46(12):95-99.
[9]杨宇,孙晗森,彭小东,等.煤层气储层孔隙结构分形特征定量研究[J].特种油气藏,2013,20(1):31-33.
[10]王文峰,徐磊,傅雪海.应用分形理论研究煤孔隙结构[J].中国煤田地质,2002,14(2):26-33.
[11]何琰,吴念胜.确定孔隙结构分形维数的新方法[J].石油实验地质,1999,21(4):372-375.
[12]Brooks R H,Corey A T.Hydraulic properties of porous media[J].Colorado State University Hydrology Papers,1964:72-80.
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