Research On Electromagnetic Wave Resistivity Logging Tool

The disadvantages of wireline logging can be compensated by logging-while-drilling(LWD)technology which is more widely applied for the measurement of complex strata or special wells.Formation resistivity is an important measurement parameter of LWD,and it is an evaluating indicator of formation properties.This thesis aim is to develop an electromagnetic wave resistivity logging tool with independent intellectual property rights.The content of this thesis mainly includes the theoretical analysis and circuit design.Firstly,the principle of electromagnetic wave logging tool is analyzed in detail,the phase difference and amplitude ratio of the received signal in the homogeneous medium are simulated.Secondly,the model of electromagnetic wave resistivity tool is designed with single-transmitter and double-receiver model structure,which mainly includes transmitting module and receiving module,and achieve the electromagnetic emission,propagation,reception,conditioning,digital signal processing and so on.To guarantee the transmission quality of signal system and driving power,the high-precision direct digital frequency synthesis(DDS)as signal generating source and class C resonant power amplification system have been used.The digital signal processing chip was used to realize the phase and amplitude detection of the receiving signal in received module.Thirdly,the commonly used digital phase and amplitude detection methods and related algorithm are introduced.Based on the application analysis and simulation results,the quadrature sampling algorithm for digital signal processing was selected,which greatly simplifies the hardware structure.Finally,the experimental platform is built up,which include the single-transmitter and double-receiver model,the digital processing system and a simulator of strata property.The simulator consists of a water tank,distilled water and salt.A series of experiments have been carried out,the experimented results showed that the function of our LWD model was feasible and this work would lay the foundation for the next step.