Research On Detection Method Of Target Casing In The U-shaped Connected Well

With the increasing demand for energy in the world,the drilling technology of U-shaped connected well has become particularly important.However,the common drilling technology of U-shaped connected well has the shortcomings of close detection distance.In order to solve this problem,this paper proposes a method for accurately detecting the target casing at a relatively distant position by using plasma impulse sound source while drilling,thereby guiding the precise connection of the U-shaped connected wells and reducing the requirements for the steering ability of drilling tool.Firstly,this paper introduces the basic principle of impulse depth detection technology while drilling in U-shaped connected wells,deduces the arrival time of various mode waves in the case of vertical reflection interface and oblique reflection interface outside the well,and deduces the calculation formula of plasma impulse sound field while drilling in radially varying media by Thomson-Hanskell propagation matrix method;Secondly,based on the finite element calculation theory of borehole sound field,the three-dimensional numerical simulation of U-shaped connected wells is completed,and the accuracy of finite element numerical simulation is verified by comparing the results of numerical simulation and real axis integral method.Finally,the effects of frequency,source distance,propagation medium,distance between reflecting target casing and detecting well axis,receiving array and energy gathering device on received signal are studied by numerical simulation method.The key parameters such as optimum frequency,source distance,detection distance and azimuth resolution of plasma impulse sound source depth detection technology while drilling are obtained by numerical calculation,which can roughly determine the azimuth of the reflecting target casing well and its relative distance with the detection well,and provide a theoretical basis for the design of the detection instrument while drilling and the subsequent data processing.