基于CSAMT结果的川东大池干井构造浅部电性结构特征分析

摘要

为揭示川东大池干井构造的浅部地质构造及岩石的电性特征和电磁响应规律,探索电磁法在油气探测中的应用,将可控源音频大地电磁法(CSAMT)应用于大池干井构造油气区,采用多种新技术进行CSAMT数据处理,获得地下电性体真实的电阻率特征,揭示该区的构造具有横向分段、纵向分层的电性特征.研究结果表明:东南部高陡背斜核部表现出相对高阻,此部分侏罗系地层较薄,主要是三叠系和二叠系地层呈层性分布;控制背斜的断层在电阻率上表现出次低阻的特性;西北翼表现出大范围低阻特性,主要是相对较厚的侏罗系上统和中统地层;在中部明显反映出单斜存在,主要表现为次高阻的侏罗系下统和三叠系上统地层.通过CSAMT法研究电性差异并结合地质构造可达到探测油气藏的目的.本工作可为大池干井构造地区从电性资料识别油气构造圈闭提供参考.%In order to study the shallow geoelectric structure of Dachiganjing structure in east Sichuan and the electrical characteristics and electromagnetic response laws of rocks, as well as explore the application of electromagnetism in oil and gas detection, the controlled source audio-frequency magneto-telluric (CSAMT) survey over the Dachiganjing area was carried out and resistivity characteristics of underground electrical bodies were obtained by processing CSAMT data using variety of new techniques. The transverse section of study area showed bed-delineating electric characteristics and piecewise distribution laterally were revealed. The results show that the resistivity of steeply dipping anticline in southeastern part of the study area is relatively high, which means that the Jurassic stratum in this place is relatively thin and the main stratums are Triassic and Dyas. The fault controlled anticline is characterized as second-rate low-resistivity layer. The upper-middle Jurassic series, which mainly locate in the northwestern part of the study area, present as a large low-resistivity zone. There exists an obvious homocline in the middle part of the study area, showing a second-rated high resistivity and it can be inferred from the lower Jurassic and upper Triassic stratum. The potential region of oil and gas accumulation can be detected from subsurface electrical characteristics by combining a priori information of geological structure with CSAMT survey results. This work provides a way to recognize the structural traps, which is related to gas and oil accumulation through the resistivity structure of Dachiganjing area.