Data Acquisition And Network Transmission Technology Research Of Down-hole Geomagnetic Receiver

With logging technology is playing an increasingly important role in oilexploration proc ess, improving the accuracy of downhole data acquisition hasimportant practical significance and application value. SP logging is a conventionaland extremely important industrial logging method, the spontaneous potential curvecan be used to determine the lithology, determine the penetration layer, calculatewater resistivity, estimate shale content and judge flooded layer. However, magnitudeof the natural potential signal is very weak, low to mV or even μV level, and its bandis very wide, ranging between10-2-103Hz, so the completion of precision acquisitionof underground natural potential for is very difficult.On the basis of unstanding general performance requirements of the logging tool,referlencing logging tool design ideas at home and abroad, and combining with thenatural potential signal characteristics, this paper designe a set of well-potential datacollection instruments, compared to similar products, which greatly improves theaccuracy of data acquisition and long-distance high-speed transmission capability.Among them, the hardware circuit complete the acquisition, storage, and transmissionof natural potential wells signals, mainly include the front-end amplifying circui,cut-off frequency of1000Hz active low-pass filter circuit, cutoff frequency of1000HzRC low-pass filter circuit, programmable gain main amplifier circuit, high-precisionA/D conversion unit of left and right channels, temperature and pressure acquisitionunit, digital isolation unit, SD card storage unit, the industrial Ethernet transmissionunit. The software part may control hardware circuit of natural potential acquisitionand display and save obtained data.The design implementate borehole2natural potential signal acquisition, may useindu-strial Ethernet interface of AT91RM9200to ransmit collected data to thecomputer for real time display and save, and also directly stored data in SD card ofthe control circuit board. The test results show that the system is of high precision,stable, and the indicators meet the design requir ements.