Structure Design And Performance Analysis Of Electromagnetic Wave Resistivity Logging Tool While Drilling

It cost a lot of working time of drilling machine to conduct conventional cable logging activity.The quality of conventional logging data and the correct assessment of actual reservoir conductivity seriously depended on factors such as borehole environment,surrounding rock condition and the invasion of mud filtrate.Technology of logging while drilling(LWD)could provide real-time information to reflect the actual situation of formation.It was of great significance in several aspects,such as the evaluation of the formation characteristics,geological orientation,minimizing operation risk and cost.Electromagnetic resistivity logging while drilling was an important part of LWD.Foreign companies had already launched relative commercial product,yet domestic technology accumulation in this field was limited.Thus,our research group aimed to develop an electromagnetic resistivity logging device of IPR.The paper constructed the coil system structure of logging device,determined its coil system parameters,and further investigated the logging response problem.All above research was based on the modeling and simulation of logging process.The details of major work in this paper were as follows.For the problem of structure design and performance analysis of electromagnetic resistivity logging tool while drilling,the method of finite difference time domain was applied to modeling and simulation.Firstly,a homogeneous stratum model was established,and the reliability of the selected method was verified by analyzing the simulation results.Then,a logging simulation model under homogeneous formation was established.Based on the theory of electromagnetic wave propagation and simulation results,the parameters and structure of the coil system were determinedIn order to solve the problem of performance determination and logging response curve interpretation of the designed logging tool,in this paper,several complex stratum models were developed.With the simulation result of different logging formation model,the paper gave detailed analysis about the influence of borehole and mud invasion,formation thickness,wellbore collapse and other factors affecting the logging response,as well as the detection depth of well logging instrument specific formation model,vertical resolution and borehole compensation detection performance.These analyses were of theoretical significance for the interpretation of logging data,the determination of logging tool performance and the optimization of coil system parameters.Aiming at the reliability verification problem design and performance analysis of logging instrument structure by simulation modeling,an indoor response test was designed.The method of FFT was selected under under-sampling to extract amplitude ratio and phase difference through simulation analysis.Then,the response test was carried out,by comparing the experimental results with the simulation results,it was proved that the structure design and performance analysis of logging tool were reliable and the function of the logging instrument prototype could be realized,these provided some theoretical basis and guarantee for the improvement of the prototype and outdoor experiments.