页岩注入超临界CO2渗流及增透实验

Study on supercritical CO2 seepage and antireflection of shale injection

以四川省长宁县双河镇燕子村龙马溪组页岩为研究对象,采用自行研制的三轴渗流装置,开展了考虑注入压力和体积应力影响的页岩中超临界CO2渗流及增透规律实验研究。结果表明:页岩中超临界CO2渗透率随着孔隙压力增大呈现先减小后增大趋势,当孔隙压力较小时存在Klinkenberg效应;随体积应力的增大渗透率逐渐减小,曲线基本呈现负指数变化规律。开展不同增透条件下页岩中CH4渗流实验,宏观量化分析超临界CO2注入压力对于页岩增透效果的影响,可以得出随着超临界CO2注入压力的增加,CH4渗透率呈现上升趋势,但增长幅度先上升后下降,即超临界CO2注入压力为9.5MPa时增透效果最为明显。通过微观分析页岩元素含量得出超临界CO2可以萃取和溶解页岩中的O、Ca、Mg等矿物元素,有效促进页岩内部微孔隙的发育,致使页岩渗透能力增强。

In this paper,taking the Longmaxi Formation shale in Yanzicun of Shuanghe Town,Changning County,Sichuan Province as the object of study,the supercritical CO2 percolation and antitransmittance regularity tests in shale considering the influence of injection pressure and volume stress are carried out by using a triaxial percolation apparatus developed by ourselves.The experimental results show that the supercritical CO2 permeability in shale decreases first and then increases with the increase of pore pressure.When the pore pressure is small,the Klinkenberg effect is obvious,and the permeability decreases with the increase of volume stress.The curve basically presents the law of negative exponential change.CH4 percolation experiments were carried out in shale under different antireflection conditions,and macroscopic quantitative analysis of supercritical CO2 was carried out.The effect of injection pressure on the antitransmittance of shale was analyzed.It can be concluded that with the increase of supercritical CO2 injection pressure,the permeability of CH4 increases,but the increasing range increases first and then decreases.That is,supercritical CO2 injection pressure of 9.5MPa is the most obvious antireflection effect.According to the microanalysis of shale element content,supercritical CO2 can extract and dissolve mineral elements such as O,Ca,Mg in shale,promote the development of micropores in shale effectively,and enhance the permeability of shale.