Analysis Of EM-MWD Signal Transmission Characteristics In Oil Horizontal Well Drilling

Electromagnetic measurement while drilling(EM-MWD)can transmit real-time engineering parameters(hole angle,azimuth and tool face angle)and geological parameters(formation resistivity and natural gamma ray of formation,etc.)during drilling,and is an important technical means for monitoring and controlling wellbore trajectory.EM-MWD is not affected by drilling fluid and drilling fluid displacement,and has high transmission rate.Reasonable signal transmission models can be used to study electromagnetic signal transmission rule of EM-MWD,and it is the basis for design and improvement of EM-MWD.At present,the theory models include electric field model and circuit model.Traditional models apply to signal transmission channel for axis-symmetry structure,but the signal transmission channel is not axis-symmetry structure in horizontal well.Therefore,traditional model is not suitable for horizontal wells.In order to analyze electromagnetic signal transmission characteristics in horizontal well,this paper puts forward an three-dimensional finite element model,combining with field experiment to validate its feasibility.The research results can offer kind of guidance and reference on relevant designing or improving.The experiment result shows that the simulation results are consistent with the experimental results.Chapter one is the introduction.It states the research significance of establishing the three-dimensional finite element model in horizontal well.The research content,the technical route and the innovation point are stated in the chapter,on the basis of full investigation and analysis of the research status of EM-MWD system and its signal transmission theory models.Chapter two is the basic principle of signal transmission of EM-MWD.It mainly states the signal excitation methods,signal transmission theory model and signal transmission channel analysis in horizontal well.Chapter three is the simulation analysis of signal transmission characteristic in horizontal well,which first states the basic principle of simulation analysis.Then signal transmission characteristic in horizontal well are analyzed,from aspects of the orientation of electrodes,receiving distance,the length of horizontal section,vertical depth and the resistivity of drilling stratum.Chapter four is the experimental verification.The three-dimensional finite element model is validated from aspects of the orientation of electrodes,receiving distance and length of horizontal interval,and the EM-MWD system is the independent research and developmentChapter five is the conclusion and prospect.It mainly expounds the research results of establishment and validation of the new signal transmission theory model,and proposes the next research work in the future,in order to supplement and improve the new signal transmission characteristics of EM-MWD in horizontal well.