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研究饱水过程中岩石波速和电阻率变化规律及其相互关系,对实际工程中岩石物性判断和地球物理探测资料综合分析解释具有重要意义。为防止原岩试样的矿物组成、原生裂隙等其他因素对试验结果的影响,采用水泥砂浆制作30组孔隙率不同的类岩石材料试样,系统测试饱水过程中不同试样的波速和电阻率变化情况,分别揭示波速和电阻率随饱和度、孔隙率的变化规律。采用常用的基于Wood理论假设的Gassmann方程得到波速与饱和度、孔隙率的理论关系,但与试验实测结果相比,该理论关系不能较好地描述饱水达到门槛值之后波速快速上升的特征。对此,考虑重力等影响对试样中孔隙水的分布状态做出合理假设,修正饱水全过程中波速与饱和度、孔隙率的关系式,与试验实测数据变化特征较一致。同时采用Archie的非饱和岩石电阻率模型公式对电阻率随饱和度和孔隙率变化规律进行了较好拟合。在此基础上,针对以往波速与电阻率关系研究中仅以孔隙率为纽带的问题,综合考虑孔隙率和饱水状态对波速–电阻率变化规律的影响,建立以试样孔隙率和饱水状态为桥梁的波速–电阻率关系,与试验实测数据拟合较好,并通过石灰岩原岩试样测试验证其合理性。
Studying the variation law of rock wave velocity and resistivity in the process of saturated water and their correlations are of great significance for the comprehensive analysis and interpretation of rock petrophysical properties and geophysical exploration data in practical engineering. In order to prevent the influence of other factors such as mineral composition, primary cracks and other factors on the test results, 30 samples of rock-like materials with different porosity were made by using cement mortar. The wave velocity and resistance of different samples Rate of change, respectively, reveal the wave velocity and resistivity with saturation, porosity changes. The theoretical relationship between wave velocity and saturation and porosity was obtained by using the commonly used Gassmann equation based on the Wood theory hypothesis. However, compared with the experimental results, this theoretical relationship can not describe the feature that the wave velocity rapidly increases after the saturated water reaches the threshold value. In this regard, taking into account the influence of gravity on the distribution of pore water in the sample to make reasonable assumptions, to amend the whole process of saturated water wave velocity and saturation, the porosity of the relationship between the measured data and experimental changes in the characteristics of more consistent. At the same time, Archie’s unsaturated rock resistivity model formula is used to better fit the resistivity with the variation of saturation and porosity. On the basis of this, aiming at the problem that the porosity is only the bond in the relationship between the wave velocity and the resistivity in the past, considering the influence of the porosity and the saturated water on the wave velocity-resistivity variation, The state is the wave velocity-resistivity relationship of the bridge, which is better fitted with the measured data. The rationality of the rock samples is verified by testing the raw rock samples.