A Design And Optimization Of Acquisition And Transmission System For Adjacent Well Distance Electromagnetic Detection

Complex structure wells such as cluster wells,double horizontal wells and connected wells can greatly improve oil and gas well production and ultimate recovery In the process of drilling complex structure wells,it is necessary to detect the distance between adjacent wells accurately in real time to ensure that they are drilled according to the predetermined trajectoryBased on the analysis of the characteristics of the original signal for detecting the distance between adjacent wells,a design scheme of high-precision data acquisition and transmission system based on denoising is proposed in this paper,aiming at the characteristics of very low frequency,very weak and narrow-band signals.The scheme includes three parts:data acquisition,data transmission and data processing of upper computer.It is optimized from three aspects:noise reduction of in-board circuit,electrical isolation of board-level circuit and power supply of the systemIn the design of underground high-precision data acquisition circuit,firstly,chopper amplifier with automatic correction feedback loop is selected to eliminate 1/f noise which has a great impact on VLF signal;secondly,high-order filtering technology is used to filter out noise and interference outside useful frequency band,which greatly improves the signal-to-noise ratio of narrow-band signal;thirdly,multi-channel 24-bit sigma-delta ADC is adopted to realize the design.The high-resolution synchronous acquisition of three-axis signals is carried out.Finally,the Chirp-Z transform with frequency focusing characteristic is embedded in the microcontroller to realize the accurate extraction of signal amplitude.In addition,the noise is analyzed and simulated in power management,device selection and PCB design,which further suppresses the noise.After testing,the short-circuit noise of the designed sampling circuit system is reduced to less than 5 ?V,and the acquisition accuracy is improved to 20 bitsThe data transmission link uses a single-core cable,which is responsible for the power supply of underground sensors and boards.The data is encoded by differential Manchester code,and the communication rate can reach 40 kbps.The hardware codec circuit make a flexible conversion of differential encoding and single-end decoding.In order to avoid interference to the acquisition circuit,electrical isolation is used between the acquisition board and the communication board.The data processing system of the upper computer designed in this paper can complete the real-time receiving,visual display,processing and storage management of underground data.A simulation facility for electromagnetic detection system of adjacent well distance is constructed by using self-made magnetic sub and signal acquisition and transmission system.The experimental results show that the effective detection distance can reach 60 m,which can meet the requirements of measurement and control of the distance between adjacent wells in the actual application.