注CO_2开采煤层气产能预测及影响因素分析
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摘要
在对注CO2开采煤层气过程所涉及的双组分气体吸附/解吸,扩散和运移等理论调研的基础上,考虑有效应力、气体吸附/解吸对煤层渗透率影响,建立了描述注CO2开采煤层气生产过程的数学模型,研究了注CO2条件下煤层气的储集、扩散和运移机理。运用数值模拟方法,分析了初始孔隙度、泊松比、杨氏模量等储层物性参数对储层渗透率变化的影响,研究了注CO2开采煤层气生产过程中CH4产量及CO2注入量的变化规律。结果表明:储层渗透率变化受孔隙压力降低、CH4解吸、CO2吸附3个因素共同作用;储层压力一定时,游离气中CO2摩尔分数越大,储层渗透率越低;同时明确了注产井间距、煤层初始渗透率和煤层温度等因素对产能的影响规律,可为现场生产提供理论借鉴。
Based on investigation of theories on dual-component gas adsorption/desorption,diffusion and migration involved during coalbed methane(CBM) extraction by CO2 injection,a mathematical model describing this process was built with consideration of the impacts of effective stress and gas adsorption/desorption on coal seam permeability,thus to study the mechanisms of CBM accumulation,diffusion and migration under CO2 injection.Numerical simulation was conducted to analyze the effects of initial porosity,Poisson's ratio and Young's modulus on reservoir permeability,and to research the variations of CH 4 production and CO2 injection during the process of CBM extraction.The results show that reservoir permeability is subjected to the combined action of pore pressure reduction,CH 4 desorption and CO2 adsorption;at a given reservoir pressure,the greater the CO2 mole fraction in free gas is,the lower the reservoir permeability is;and the impacts of injector-producer spacing,initial permeability and temperature of coal seam on productivity are understood.This research provides theoretical reference for field production.
Based on investigation of theories on dual-component gas adsorption/desorption,diffusion and migration involved during coalbed methane(CBM) extraction by CO2 injection,a mathematical model describing this process was built with consideration of the impacts of effective stress and gas adsorption/desorption on coal seam permeability,thus to study the mechanisms of CBM accumulation,diffusion and migration under CO2 injection.Numerical simulation was conducted to analyze the effects of initial porosity,Poisson's ratio and Young's modulus on reservoir permeability,and to research the variations of CH 4 production and CO2 injection during the process of CBM extraction.The results show that reservoir permeability is subjected to the combined action of pore pressure reduction,CH 4 desorption and CO2 adsorption;at a given reservoir pressure,the greater the CO2 mole fraction in free gas is,the lower the reservoir permeability is;and the impacts of injector-producer spacing,initial permeability and temperature of coal seam on productivity are understood.This research provides theoretical reference for field production.
引文
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[2]池卫国,吴松钦.对我国煤层气勘探前景的再认识[J].石油实验地质,2000,22(2):131-135.
[3]高慧梅,何应付,周锡生.注二氧化碳提高原油采收率技术研究进展[J].特种油气藏,2009,16(1):6-11.
[4]张亚蒲,杨正明,鲜保安.煤层气增产技术[J].特种油气藏,2006,13(1):95-98.
[5]傅雪海,等.多相介质煤层气储层渗透率预测理论与方法[M].徐州:中国矿业大学出版社,2003:9-10.
[6]马志宏,等.注入二氧化碳及氮气驱替煤层气机理的实验研究[J].太原理工大学学报,2007,32(4):335-338.