电性源瞬变电磁快速反演解释方法

电性源瞬变电磁法是俄罗斯等国家油气勘探的主要手段,国内相关解释和应用技术研究较少.在现有条件下,瞬变电磁法观测的是场源变化在接收线圈里产生的感应电动势,但是利用感应电动势计算全区电阻率往往出现双解或无解现象.实际计算中将实测的感应电动势转换成磁场,利用磁场计算全区视电阻率和电阻率反演.目前瞬变电磁反演主要采用“烟圈”反演方法,“烟圈”反演方法把感应涡流场在地表引起的磁场看作为地下各个涡流层的总效应,并认为近似等效于向下传播的一个个简单的电流环,地表瞬变电磁响应可以由某时刻地下的镜像电流环作为源来进行计算.文中给出电性源瞬变电磁测深一维“烟圈”反演解释方法的基本原理、计算方法和应用实例.

A RAPID INVERSION TECHNIQUE FOR GROUNDED SOURCE TRANSIENT ELECTROMAGNETIC METHOD

Grounded source transient electromagnetic method is the leading means of oil and gas exploration adopted by Russia and other countries, but less related interpretation and applied research are found in our country . At present, we measure the voltage induced in a re- ceiving coil owning to source field varying through the transient electromagnetic method. However, it is difficult to calculate the resistivity from induced voltage. So we change induced voltage measured in field to magnetic field in actual calculation, and then compute the apparent resistivity and proceed to inverse resistivity from magnetic field. Today, smoke ring inversion is one of the most important transient electromagnetic inversion methods. It sees magnetic field at the surface of the Earth owing to induced vortex field as the total effect of each underground vortex layer , and suggests that the total effect equate each simple current ring moving downward . It can be calculated from the underground current ring of images of the source that transient electromagnetic response at the surface of the Earth at each delay time. This article introduces the ultimate principle and calculation method technique of 1-Dsmoke ring inversion technique for grounded source transient electromagnetic method and the applied examples.