摘要
含流体孔隙介质因双电层的存在可引发一种弹性-电磁耦合效应(震电效应).该效应产生的转换波场兼具弹性波的空间分辨率和电磁波的电化学敏感性,进而受到地球物理学界的广泛关注.然而当前有关震电效应的理论模拟及实验测量大多基于单一流体饱和模型展开,这与多种流体夹杂饱和的实际复杂地层情况不符.因此,本文重点针对部分流体饱和情况下的震电响应问题,在实验室内开展岩样内部震电波场的观测分析研究.根据地下流体饱和度的渐变分布形式,设计一种可实现部分流体饱和的实验模型,并通过内嵌电极的布置方式,开展岩样内部随震电场和界面电磁波的实验测量,记录这两种转换波场的时域波形,讨论他们在部分饱和情况下的传播特性,分析他们的幅值衰减变化规律,对比二者对饱和度差异的敏感性,研究饱和界面对震电耦合波场的影响.实验结果表明:在岩样内部可以观测到直达随震纵波、岩石上表面的反射震电场及饱和度界面激发的界面电磁波,其幅值衰减符合指数变化规律.随震纵波振幅和波速对饱和度敏感性较低,但界面电磁波在不同饱和度岩样中传播时存在明显的幅值差异.因此可利用震电转换信号识别复杂储层中的饱和度分界面,这为油气定位和储量判断提供了重要参考依据.
Fluid-containing porous media induce an elastic-electromagnetic coupling effect(Seismoelectric effect)due to the presence of the double electric layer.This effect produces a converted wavefield that combines the spatial resolution of elastic waves with the electrochemical sensitivity of electromagnetic waves,thus attracts widespread attention in the geophysical field.However,most of the current theoretical simulations and experimental measurements of the seismoelectric effect are based on a single-fluid saturation model,which is inconsistent with the actual complex stratigraphic situation where multiple fluids are saturated.Therefore,we focus on the seismoelectric response of partially saturated condition and analyze the seismoelectric wavefields inside the rock sample in the laboratory.According to the gradual distribution of underground fluid saturation,we design a kind of experimental model that can realize the partial fluid saturation,then conduct experimental measurements of the coseismic waves and the interfacial electromagnetic waves inside the rock through the embedded electrodes.After recording the time-domain waveforms of these two converted wavefields,we discuss their propagation characteristics under the condition of partial saturation,analyze their amplitude attenuation laws,and compare their sensitivity to differences in saturation,so as to study the effect of saturated interfaces on the seismoelectric coupled wavefields.The experimental results show that the direct coseismic longitudinal wave,the reflected seismoelectric waves on the upper surface of the rock and the interfacial electromagnetic waves excited by the saturation interface can be observed inside the rock sample,and their amplitude attenuation matches the pattern of exponential law.The amplitude and velocity of the coseismic longitudinal waves are less sensitive to the saturation,but there are significant amplitude differences of interfacial electromagnetic waves in the rock with different saturations.Therefore,the seismoelectric conversion signals can be used to identify the saturation interface in complex reservoirs,which provides an important reference for the oil and gas localization and the reserve determination.
作者
聂成洋
王军
韦庆华
关威
胡恒山
NIE ChengYang;WANG Jun;WEI QingHua;GUAN Wei;HU HengShan(Department of Astronautics and Mechanics,Harbin Institute of Technology,Harbin 150001,China)
出处
《地球物理学报》
北大核心
2025年第8期3258-3267,共10页
Chinese Journal of Geophysics
基金
国家自然科学基金项目(42374140,41974136,12272107)资助.
关键词
震电效应
部分饱和
界面电磁波
伴随震电场
Seismoelectric effect
Interfacial electromagnetic wave
Coseismic electric fields
Partial saturation
