The Magnetic Flux Leakage Testing Method And System For Washover Pipe Thread

Washover pipes are widely used in workover operations field as a special device for dealing with the well drilling accident and malfunction. The thread of washover pipe easily produces different types of defects and fails to work because of the harsh and changeable working condition which is full of alternating impact load and the influence of its own structural. Till now, an accurate and reliable inspection method which is easy to realize and can be carried out quickly in the field nondestructive testing is still in lack. The existent method which is most for the disengaging thread testing is hard to be used in the testing of the thread in meshing. But engaging and disengaging thread is time consuming and costly which can't meet the demand for the using in the workover field. So, in this paper, an inspection method based on magnetic flux leakage (MFL) testing is proposed, which can accomplish the inspection of the washover pipe thread under meshing quickly. This method has the character of engaging testing, strong penetrating ability and high efficiency.Starting with the forming course of the MFL of defects, the MFL testing method for thread are presented. Then, by the finite element analysis and experiments on the two stacked steel plates and the sampling pipes, the feasibility and effectiveness of the method have been confirmed. The result shows that scanning on one side by interlayer detection can realizes the testing of the internal and external thread in meshing. Further, magnetization and scanning modes which is the two key parts in the process of the implement of this testing method are analyzed and the signal form in all scanning ways is given. The experiment result of the actual testing of the washover pipe indicates that inspecting different part thread should take corresponding scanning ways to get best testing effect.On the base of the research above and according to the character of washover pipe thread and site requirements, a testing scheme of through-coil magnetization and circular scanning is provided. Then, depending on the well locale situation, the mobile testing system is designed and successfully used in Daqing oilfield workover field. This system has characters of convenient operation, high efficiency, stabilization and reliableness , which will lead to a wide application foreground.