可控源时域电磁剖面成像方法与应用

Imaging method and application for the source-controlled time-domain electromagnetic profile

为了提高可控源时域电磁成像方法的分辨能力,实现对油气储层的有效识别,在多道瞬变电磁法的研究基础上,开展可控源时域电磁剖面成像方法与实际应用研究,以期提高视电阻率成像的稳定性与可靠性,解决油气储层与油水分界面识别难题。首先,以瞬变电磁场扩散理论为基础,将阶跃电流激发条件下得到的电场响应做微分运算,得到电场分量二次场波峰幅值与其走时的对应关系,定义了该方法视电阻率计算公式及其成像方法;其次,确立了该方法的野外资料采集方式,即保持地面观测点不动,依次移动发射源,将采集到的数据进行归一化处理,结合视电阻率成像方法,获取地下地质构造视电阻率剖面;最后,利用该成像方法对大庆宋芳屯油田可控源时域电磁法试验资料进行了处理,获取了试验区视电阻率拟断面图。结果表明,通过与试验区测井资料及瞬变电磁二维反演电阻率剖面对比认为,该方法成像简单快速,降低了反演的非唯一性,增强了资料解释的可靠性,成像结果具有良好的地质效果。

In order to enhance the resolution capability of the source-controlled time-domain electromagnetic imaging method and realize the effective identification of the oil and gas reservoir,on the basis of the theory of multichannel transient electromagnetic method,the imaging method stated above and its actual application were studied to improve the stability and reliability of the apparent resistivity imaging and solve the identification problem between the petroleum reservoir and oil-water interface. Firstly,based on the diffusion theory of the transient electromagnetic field,the electric field response obtained under the step current excitation condition was calculated differentially and the corresponding relationship between the quadratic field peak of the electric field component and its travel time was achieved,and moreover the calculating formula of the apparent resistivity and the imaging method for this method were defined;secondly,the field data collecting method was established,such as keeping the observation point still and moving the source in turn,then taking the collected data to normalize,combing with the imaging method of the apparent resistivity,the resistivity profile of underground geological structure was obtained;finally,with the help of this imaging method,the data of the source-controlled time-domain electromagnetic test in Daqing Songfangtun Oilfield were processed,and pseudo-section map of the apparent resistivity profile in the tested area was obtained. The results show that compared with the logging data of this area and the resistivity section by the transient electromagnetic two-dimensional inversion,this imaging method is considered to be simple and fast,reduce the non-uniqueness of the inversion,enhance the reliability of the data interpretation and furthermore possess much better geological effect for the imaged result.