Design Of Advanced Geological Exploration System For Drilling Based On Array Electrode Method

Drilling exploration is a common geological detection method,and the detection results are reliable and intuitive.There are a few of different drilling modes,including core drilling and non core drilling,or geotechnical mechanical parameters testing.However,drilling can get point-to-line geological information according to the depth of drilling.The direct current electric Method is a reliable exploration method.How to combine the two methods organically and to extend the exploration geological information from 2-dimension to 3-dimensiona around the borehole is a wide application prospect research topics.To solve the above problems,this paper combines the advantages of DC electrical exploration and drilling,and establishes the array electrode MWD(Measurement while drilling)detection system.By the electromagnetic finite element simulation software Maxwell,to measures and calculates the influence and variation law of resistivity of different geology resistivity on the electrical parameters between the drill pipe as A electrode and the reference B electrode around the borehole,and the twodimensional/three-dimensional geological model have been analyzed.In array electrode method,drill pipe is used as A electrode,and a lot of reference B electrodes are evenly arranged around the borehole.Single electrode,four electrode and eight electrode modes can be adopt.With the increase of number of electrodes,the space resolution of the detection will improve.With the increase of drill pipe length,the physical parameters of different rock and soil layers are different,and the current and voltage parameters between AB electrodes are measured,according to the electrical parameters collected between AB electrodes,the apparent information of rock layers can calculate,to obtain the plane and three-dimensional geological information around the borehole.The micro-controller STM32F429 completes the electrode switching and data acquisition.The H-bridge circuit is designed to transmit positive and negative high voltage electric pulse t through A and B electrode,and the B electrode switching circuit is controlled by a microcontroller STM32F103.The H-bridge drive circuit of the system is driven by I / O port line of microcontroller,when the microcontroller sends the signal,the signal is reshaped through the logical AND gate first,and then through the isolated driver SI8233 output,the output signal controls the H-bridge to establish the positive and negative alternating electric field.The switch of reference B electrode is completed by relay,which complete switch and access the electrodes in different directions.The master control circuit adopts the master-slave working mode.The host sends the switching command through the defined communication protocol.The ADS1274 analog-to-digital conversion chip collects the current and voltage between the AB electrodes and the voltage between the MN detection electrodes respectively.The collected data is saved in the TF card,and sent to the tablet computer through wireless transmission to save in a file format to analysis.The main control circuit of data acquisition communicate with upper computer by Wifi module.Through the SDK development tool of CC3200 module,the SPI interface is designed to interact with the main control chip,and realize the wireless data transmission between the host computer and upper computer,which can realize the rapid information transmission.In the main control chip,RT-Thread real-time embedded operating system is used for program design.Through multi thread mode,command and data are sent and received.For data transmission,the communication protocol between the main control circuit and the host computer,and the communication protocol between the main control circuit and the electrode switching circuit are designed respectively.According to those protocols,the reliable transmission of data is realized.The main control software of upper computer is designed with QT application development framework based on QML language and C + +.The performance of the detection system is tested,and the related functions are achieved.In the field test,the system collects the data information of the formation drilled in the early stage,calculates the apparent resistivity of the data,and uses draw the equipotential apparent resistivity diagram of four sections of the detection body with drill pipe as the axis,which can directly observe the geological change information,and the test results are basically consistent with the drilling geological data.In the future work,in the detection method,we can increase the polarizability detection to compare the apparent resistivity to achieve better detection effect.In terms of data analysis and inversion,3D geological stereogram can be established to make the detection results more intuitive.