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致密砂岩气藏在开采时因地层能量衰竭导致有效应力增加,储层物性相应地发生变化,其电学参数也随之改变.以往在常规围压下进行的岩电实验,其结果包含了岩样微裂缝等因素对电阻率的贡献,获取的电学参数不能客观反映原地储层性质.本文以鄂尔多斯盆地上古生界二叠系典型致密砂岩气藏为研究对象,测定了不同有效应力下完全饱和地层水71块致密砂岩样品的电学参数.结果表明,岩样电阻率随有效应力增加而变大,且与常规砂岩相比,致密砂岩电学性质受有效应力影响更大;随有效应力增加,岩性系数a增大,地层胶结指数m减小,原地有效应力(25.86MPa)下a和m分别是常压(3.5MPa)下的2.7和0.7倍;高有效应力状态下,电阻率达到稳定值所需测试时间更长;电阻变化幅度直观表征了其骨架结构变形程度,也是致密砂岩应力敏感时间效应的直接体现.因此,应根据储层原地有效应力确定致密砂岩气藏的电学参数.
Tight sandstone gas reservoir increases its effective stress due to the energy failure of strata during mining, and the reservoir physical properties change correspondingly, and its electrical parameters also change. In the past, the rock electric experiments conducted under the conventional confining pressure included rock samples Micro-cracks and other factors on the resistivity of the electrical parameters obtained can not objectively reflect the nature of the reservoir.Based on the Upper Ordos Basin Permian typical tight sandstone gas reservoir as the research object, measured under different effective stress fully saturated The results show that the electrical resistivity of rock samples increases with the increase of effective stress, and the electrical properties of tight sandstone are more affected by effective stress than conventional sandstone. With the increase of effective stress, The coefficient a increases and the formation cementation index m decreases, a and m are respectively 2.7 and 0.7 times at normal pressure (3.5MPa) at the effective site stress (25.86MPa), and the resistivity reaches stable under high effective stress The value of the required test time is longer; resistance change range intuitively characterizes the extent of the deformation of the skeleton structure, but also a direct reflection of the time-sensitive sandstone stress-sensitive effect.Therefore, Determining electrical parameters of tight gas sands.