Research On Measurement While Drilling Method For Adjacent Wells Ranging Based On Current Excitation

The drilling technology of complex structure wells has been widely used in the drilling of oil and gas wells such as horizontal wells,cluster wells,infill wells and relief wells.In the process of operation,problems such as multi-well anti-collision,obstacle detour and connection will inevitably be encountered.Therefore,during the critical period of drilling,accurate measurement and control of the offset well distance must be carried out to avoid accidents or deviations from the preset trajectory caused by the gradual accumulation of wellbore trajectory errors,thereby ensuring the safety and efficiency of the downhole drilling process.In order to meet the application requirements of drilling engineering for complex structural wells,the purpose of this thesis is to realize real-time measurement of wellbore trajectory and adjacent well distance,ensure operation safety and efficiency,and reduce operation time and cost.On the basis of in-depth analysis of the principle and characteristics of the existing ranging methods for adjacent wells,comprehensive research methods including theoretical algorithm analysis,finite element model simulation(FES)and simulation test experiments have been adopted to carry out the research on measurement while drilling(MWD)method of adjacent wells ranging based on current excitation.For cluster well anti-collision and relief well connectivity ranging applications,two new ranging methods while drilling are proposed respectively: the "current excitation of casing in adjacent wells" ranging method and the "current excitation of dual-electrode in drilling" ranging method.The ranging method based on casing current excitation can solve the problem of positioning between drilling and multiple adjacent wells in cluster well development by means of "time division multiplexing" or "frequency division multiplexing";the ranging method based on dual-electrode current excitation in drilling well,can greatly save time and cost by using synchronous excitation,which is efficient and safe,and more suitable for the connection operation of relief wells with safety risks.Ranging while drilling positioning models corresponding to the two excitation methods are established,the calculation formulas for the attenuation of the casing current amplitude of the target well and the distribution of the induced magnetic field in the formation are derived,and the calculation methods for the distance and direction of the target well are obtained.Through numeral calculations and finite element simulations,the influence degree of each key factor is analyzed,and thus the correctness and effectiveness of the two ranging methods are verified.Furthermore,in order to promote the engineering application of the MWD method for ranging based on current excitation,the overall structure and circuit design scheme of the two-electrode current excitation distance MWD prototype are proposed,and the structure design method and key circuit design principle of each part of the system are given,and high-precision measurement circuits for weak magnetic ranging signals are designed,which can run stably and reliably.Finally,a ground simulation test device for ranging of adjacent wells is constructed.The results of the simulated ranging experiment show that the actual measured values and the theoretical calculated values match well,which further verifies the effectiveness of the ranging method.At the same time,the test results of the magnetic field strength measurement resolution also show that the measurement accuracy of the measurement circuit is as high as 0.1n T,thus ensuring the effective detection distance of more than 10 meters.The research results have laid a core theoretical and technical foundation for the ranging of adjacent well while drilling in cluster wells and relief wells.