Application of Borehole Transient Electromagnetic System in Relief Well Drilling: a Case Study

In the process of offshore and land drilling, once the blowout out of accident occurs, oil and gas resources will be seriously damaged, which will be easy to cause catastrophic events such as casualties and environmental pollution. Drilling a relief well beyond a certain distance around the blowout well to achieve connection is an effective way to control blowout. Affected by the error ellipse, it is difficult for the relief well to hit the accident well directly only depending on the trajectory information, where the relative distance and azimuth information of two wells should be measured in real time. In this paper, the borehole transient electromagnetic system is used to measure the resistivity of surrounding medium in relief well, and the relative distance of two wells can be inversed by using the influence of the accident well casing on the resistivity of surrounding formation. On this basis, the relative azimuth can be calculated in real time by using the spatial geometric positioning algorithm. Moreover, the experiments demonstrated that the proposed system can measure and calculate the relative distance and azimuth between the relief well and the blowout well, and finally guide the successful connection between two wells.