| Electromagnetic wave propagation logging(also called dielectric logging)is one of the key technologies for evaluating oil and gas layers.When the salinity of formation water is low,it can distinguish oil and water layers better than ordinary resistivity logging.In the formation,the resistivity and dielectric constant of the medium change,which leads to changes in phase difference and amplitude.Dielectric logging transmits signals to the formation through the transmitting coil,and then receives the signal from the coil,and converts it into phase resistivity and amplitude resistivity by analyzing the received signal.The phase signal can well reflect the change of formation resistivity.Based on this,this paper makes an in-depth study on the amplitude and phase detection module in the receiving circuit of the dielectric logging tool,and develops and designs related circuits.Through literature research,the previous measurement methods mostly used trivial circuits to detect the phase difference and amplitude ratio,which not only failed to meet the accuracy requirements,but also could not be applied to actual production.Analyze the current research situation at home and abroad,and finally select the AD8302 monolithic integrated chip manufactured by American Analog Devices,which can work stably in the high-frequency environment,up to 2.7 GHz.The measurement accuracy is higher and the circuit is simpler.This article also made a part of optimization to extend the phase difference measurement range to 0-360 °,avoiding the problem of difficult to identify the phase difference lead lag,this function is completed by the zero-crossing comparator and D flip-flop.The thesis completed the design,programming,plate making and debugging of the above circuits,and the programming test of related algorithms.The final results show that the amplitude and phase detection circuit designed in this paper is reasonable and feasible,and basically meets the design requirements. |
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