Study On The Rock Resistivity Measurement System Based On DSP

Formation resistivity is one of the important parameters of oil and gas evaluation inpetroleum logging interpretation. With the deepening of fine oil and gas exploration, theelectrical anisotropy reservoirs such as conglomerate formation, thin interaction layerinteraction, tight formation, porosity formation, fractured formation, etc are becoming theimportant development direction.It is urgent to strengthen the study of the formation electricalanisotropy, establish the quantitative relationship between the anisotropic tensor resistivity andthe formation oil and gas evaluation parameters and provide the theoretical basis of oil and gasinterpretation evaluation. This thesis finishes the design and implementation of the measuringsystem with the multichannel data acquisition based on a DSP control unit. The device formeasuring the rock anisotropic resistivity is designed. The main research contents andachievements are as followings.The first part studies the numerical method for calculating the rock resistivity based onthe COMSOL finite element software. Build the physical and methmetical model based on thereal device for measuring rock resistivity. Study the method of adding source on the sourceelectrode and the techniques of mesh generation. Using COMSOL’s powerful postprocessingfunction of calculating and ploting, through plotting the flow lines of the electric currentgenerated by the emission electrode in space, we reveal the forming mechanism of theelectrical anisotropy. It lays the foundation for the measurement and analysis of electricalanisotropy.The second part is the measuring device and its structural design. On the basis ofanalyzing the present four electrodes resistivity measurement method, a new four electrodesmethod is proposed. It can measure the nine components of resistivity tensor. The new methoduses the ring-measuring electrodes which surround the emission or return electrode. It caneliminate the influence of electrode polarization.The third part finishes the multichannel data acquisition circuit designing on the basis ofTMS320F2812DSP’s control. It includes circuit design and parts selection such asanalog-to-digital conversion AD choice, the power filter, signal conditioning circuit, externalcircuit, serial circuit, external memory, protracting PCB board, weldingthe test circuit. The forth part firstly designs the procedure of DSP acquisition software on basis of DSPdevelopment environment. Then through comparing and analyzing the traditional theadjustment principle of two point-one line and the least square, we chose the least squaremethod to improve the acquisition precision. Finally, develop the software based on the VB,and achieve functions such as serial communication, command control, show waveform anddata storage and data processing.Finally, use the design device and the measuring system to measure resistivity of rock.Comparing and analyzing the measuring results with the theory simulation results based onCOMSOL software, it shows only in the ideal condition the theory results are consistent withthe real measuring results perfectly. As a general rule, there exists some different in the theoryand the actual, it deponds on the various factors. The test and data analysis show that thedeveloped system can finish the fundamental design requirements.