The Study Of Calibration Method And Energy Spectrum Drifting Problem Of Litho-Density Logging Toll

With the development of science and technology, the oil is used in more and more industries. Due to the non-renewable nature of the oil, we can only obtain it through mining. Therefore, the development of oil exploration technologies becomes increasingly important. In all logging technology, nuclear logging technology is more widely studied and applied because of its’ ability to quickly get stratigraphic information. In order to obtain a stratigraphic-lithologic information and density information in one-time, we can obtain the information only through the litho-density logging tool. Therefore, litho-density logging tool have been developed as one of the important logging tolls.The content of this paper is based on litho-density logging project of CPL Logging Company. The inaccuracy of the calibration of the instrument will cause unpredictable error in the final result. And the drifting of gamma ray spectrometry will cause great deviation in the spectroscopy data. Therefore, this study aimed at resolving the energy spectrum drifting problem of Litho-Density Logging Toll and research the calibration method of the instrument.This paper first introduces the study of litho-density logging tool calibration method. First, find out the reasons of energy spectrum drifting problem in the logging process through a large number of experiments according to the project requirements. Then look for an instrument debugging method to eliminate the impact of energy spectrum drift in the process of logging as much as possible. On this basis, we study the instrument calibration method and fit the appropriate algorithm of density calculating and lithology calculating. And then solve the error of the test result caused by the inaccuracy of the calibration of the instrument. After solving the problem of the calibration of the instrument, we must to continue study to solve the energy spectrum drifting problem.On the aspect of hardware and software, introduce the improvement of the circuit of Litho-Density Logging Toll and the program. Increase the bias adjustment control function and baseline recovery function. Use FPGA to get the baseline of the signal and recover the baseline and then form the energy spectrum. Use MCU to control a DAC with single SPI bus to adjust the height of the baseline of the analog signal. And then solve the drifting problem of energy spectrum. Then introduce the control circuit of the instrument specifically. Include amplifying and filtering circuit, high-speed sampling circuit, FPGA data processing circuit, MCU controlling circuit and communication circuit. And describe the process control module. Include figure baseline recovery module, spectroscopy forming module, data communication module and so on.After completion the improvement of the entire circuit, we test the system. First, we test the baseline data obtained by FPGA. Then on the basis of the correct baseline data, we test then energy spectrum. Analyze the test results, we find the energy spectrum data is stable. And then solve the energy spectrum drifting problem of the instrument in the logging process. Achieve the expected goals.