Research On Realtime Calibration System Of Pressure Sensor In MWD

With mass application of digital drilling technology of MWD system, standpipe pressure sensor for detecting downhole data transmission is becoming an important approach for data acquirement. Accurately getting pressure value is an important insurance for system operation. This system make the test with two pressure sensors distinguished from traditional test method with single pressure sensor. On the one hand measuring accuracy of pressure sensor can be improved, on the other hand real time calibration and monitor of pressure sensor can be performed on site. The pressure sensor under proof can be replaced at any time without affecting to the normal directional drilling operation, which has practical significance to the field service.This paper analyzes research significance, present situation and development trend of MWD pressure sensor calibration system. On this basis, this paper makes detail description about the research of MWD pressure sensor calibration system according to the actual work requirements for the well service, especially focus on the calibration of in-house standard pressure sensor and the procedure how to use two pressure sensors to perform real time calibration on site. This paper represents selection and certification of nonlinear calibration method and scientifically sets study content and technical description. This paper corrects the system error about nonlinearity and temperature by using BP neural net and makes calibration by using tool kit of the MATLAB neural net. This paper introduces how the chip MC9S12DG128 of Motorola company complete the circuit design for dealing with low noise signal and implementation of calibration data processing software.Finally, characteristic and indication of the system were verified by performing in-house simulation experiment and practical application on site.