深层页岩伊利石孔隙中甲烷吸附相密度特征

Adsorption phase density characteristics of methane in illite pores of deep shale

杨琴 黄亮 周文 邹杰 王璐 刘逸盛 冯鑫霓

成都理工大学油气藏地质及开发工程全国重点实验室，四川 成都 610059 成都理工大学能源学院，四川 成都 610059

State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation, Chengdu University of Technology, Chengdu 610059, China College of Energy, Chengdu University of Technology, Chengdu 610059, China

页岩纳米孔隙中超临界甲烷的吸附相密度特征是明确页岩真实含气量的基础。基于伊利石纳米孔隙中甲烷吸附相的分子模拟数据，在温度333.15~423.15 K和压力0~90 MPa区间内，分别利用Langmuir三元模型法、过剩吸附曲线截距法、密度剖面积分法计算了甲烷吸附相的密度和绝对吸附量，分析温度、压力和孔径对甲烷吸附相的影响规律，系统检验甲烷吸附相密度计算方法的合理性。研究表明：1）温度的升高减弱了甲烷受到的孔壁吸引作用，降低了甲烷吸附相的密度和绝对吸附量；2）甲烷吸附相的密度和绝对吸附量随压力增大而增加，深层页岩中地层高压对甲烷吸附相的密度和绝对吸附量仍有重要影响；3）受甲烷吸附相扩展和孔壁耦合吸引作用影响，甲烷在2 nm和4 nm孔隙中的吸附相密度和绝对吸附量更大；4）基于分子模拟的积分法适用于深层页岩纳米孔隙中甲烷吸附相密度的确定和绝对吸附量的校正。研究结果对页岩气储量准确评价具有重要意义。

Adsorption phase density characteristics of supercritical methane in shale nanopores are fundamental to the determination of accurate shale gas contents. Based on molecular simulation of methane adsorption in illite nanopores, the Langmuir ternary model fitting method, excess adsorption curve intercept method and density profile integration method were utilized to calculate the methane adsorption phase densities and absolute adsorption capacities in the temperature range of 333.15￣423.15 K and pressure range of 0￣90 MPa. The effects of temperature, pressure and pore size were discussed, and the rationality of various calculation methods for adsorption phase densities was validated. The results show that:(1) The increase of temperature weakens the pore wall attraction towards methane, reducing the methane adsorption phase densities and absolute adsorption capacities. (2) The methane adsorption phase densities and absolute adsorption capacities increase with increasing pressure, the effects of pressure on the methane adsorption phase densities and absolute adsorption capacities remain significant at high pressures of deep shale gas reservoirs. (3) Due to the expansion of adsorption phases and the coupling attraction of pore walls, the adsorption phase densities and absolute adsorption capacities of methane in 2 nm and 4 nm pores are larger than those in pores with other sizes. (4) The integration method coupled with molecular simulations is suitable for the determination of methane adsorption phase density and absolute adsorption capacity in deep shale nanopores. The research results are of great significance for the accurate evaluation of shale gas reserves.

10.6056/dkyqt202305012