Research On Data Acquisition Of Well-earth Potential And Wireless Communication Protocol

China is a big oil consumption country, but domestic oil production is decreasingfor years. China has become a net oil importing country importing more than60%,which make oil energy security situation is very grim. In response to this situation,Development Plan Outline for Medium and Long Term Science and Technologypropose to mining oil resources of complex geology, improve oil recovery of old fields,and to ease the tight situation of oil energy supply. Water injection is an importantmean for improving the recovery of old wells. Resistivity Tomography method takeadvantage of excitation electric field, measuring the potential of the surface throughinstrument, than we could know the change of the ground resistivity. Finally the towardand range of water injection will be tested. Potential data acquisition is a key part ofthe whole technology, which is the focus of this paper.The main content of this paper is divided into two parts: One is the research ofpotential data acquisition, and the other is study on the wireless communicationprotocol of ZigBee. This paper compares a variety of similar instrument and proposesa new design of distributed data acquisition and wireless transmission node. Theexperimental results show that the design meet the requirements, which can fullymeet the requirements of well ground potential data acquisition. The second partstudys on the ZigBee communication protocol, comparing with similar protocols andanalysising its advantages. Than pointed out its disadvantage under the condition ofthis paper, specially the CSMA/CA channel mechanism. Finally we test it viasimulation. The experimental results show that the packet loss rate, network responsetime, throughput of the network performance has been improved.The acquisition node use “MSP430master controller+FPGA slave controller” asthe core of the system. It takes modular design for various functional parts, includingsystem calibration module, analog-to-digital converter module, the timing control unit, high-capacity storage module, wireless transceiver module, power supply andpower-down protection module. System calibration module includes DC offsetcompensation and ground resistance testing capabilities. Amplifier circuit removesamplifier offset voltage and1/f noise by chopper technology. ADC module uses themode of “Modulator+digital filter”, which contains a delta-sigma modulation techniqueand oversampling acquisition technology. The result will be the improvement ofresolution and signal-to-noise ratio of the system acquisition. Finally we verified theacquisition accuracy and the stability of the system by experiment. FPGA logic devicecontrols the timing of the analog-to-digital acquisition. It also solves the problem ofrate matching between the ADC and the master controller via designing cache. FPGAlogic device controls large-capacity SRAM and makes a large-capacity, high-speedmemory module which solves the problem of the storage of local data. Designedwireless transceiver module by ZigBee wireless communication module which calledSZ05, solved the problem of data transmission. The paper tests loss rate and otheraspects of performance of wireless module. Experimental results show that thewireless transceiver module meets the design requirements. Each power module wasdesigned individually to ensure perfect performance. The reference voltage of theanalog-to-digital converter module was taked special shielding and protectionmeasures to ensure its accuracy. The paper designed power-down protection circuitfor volatile memory SRAM to ensure reliable storage.In this paper, ZigBee wireless communication protocol was researched. Itanalyzed the improved channel access mechanism. Finally the paper described indetail the method of avoiding channel conflict. The experiments were carried outunder the conditions of simulation and tested the network performance of thestar-shaped network. The two mechanisms were compared in three aspects of thepacket loss rate, network start-up time and throughput. Experiment results show thatthe new mechanism can enhance network performance at each of these threeaspects.Later tested the performances of potential data acquisition node, including thecorrection function test, short-circuit noise test, square wave acquisition test and oil-field field test. The correction function test results show that the system has a goodcompensation effect for DC offset. The short-circuit noise test results show that thesystem acquisition error in the μV level. Electrode short-circuit tests show thatnoise stabilization process will take some time in this environment, and graduallysmooth. Square-wave acquisition tests show that the system can distinguish signal inthe μV level. Achieve the desired results.