The Key Technology Research On Signal Measurement Of Measurement While Drilling System

Oil and gas are important national energy and strategic resources, which relate to national production and daily life, even relate to national security. Measurement While Drilling (MWD) system is a high-ech and essential measurement system for directional well, which combines drilling, logging, signal processing, mechanical processing, automatic controling, mathematical modeling and circuit designing.MWD system, summing up the advantages and disadvantages of siphon inclinometer, camera, electronic single inclinometer and electronic multi-inclinometer to make better, is the foundation of Logging While Drilling (LWD) and rotary steerable technology. Moreover, the system is an intelligent control system, which includes signal measurement, signal transmission and mechanical control, involving software systems, electronic components, and mechanical control, etc. In this thesis, the principle of MWD system is described, and measurement errors are analysised and calibrated at first. Then, for the sake of filtering the noise signal in the mud pulse signal transmission technology, a wavelet transform based on pulse code denoising and signal extraction algorithm is proposed, which can effectively restore the original signal. Finally, an introduction is made to introduce mechanism, system structure and system using. The emphases of this thesis are errors correction methods on MWD signal measurement system and mud pulse signal denoising.MWD system measures signal, using the earth gravity field and magnetic field by three axis gravity sensor (MEMS accelerometer) and three axis magnetic sensors (fluxgate magnetometer) to measure the acceleration of gravity and magnetic field strength component, which are converted into current signal and digital signal to compute inclination, azimuth and other parameters. In order to accurately get the bottom of parameter information, there is need to ensure the accuracy of the sensor installation and the sensors work well in different states. However, there are certainly some errors in the production of measuring instruments. For example, there are installation errors due to non orthogonal between sensors and measurement errors caused by microelectronic sensors (MEMS) drift phenomenon. Therefore, the key problem in the signal measurement module is to eliminate or reduce the error as much as possible. This paper presented Angle difference compensation algorithm based on sensor to correct installation errors (three vector sensors are not mutually orthogonal and the coordinate system of sensor and earth coordinate system do not coincide) and warming curve fitting method to correct the measurement error (MEMS drift phenomenon). Combining with the actual production, a set of simple calibration methods and rapid implementation process are presented.Referred to the mud pulse noise signal, mud pulse transmission technology is introduced firstly. Then, according to the actual situation in the oil drilling, the mud pulse signal is captured by a pressure sensor and recorded by the software. After analyzing the type of noise signal, some simulation experiments are made to compare performances of different de-nosing method. Finally, wavelet transform method is used to remove high frequency noise in the actual signal firstly. Hereafter, based on pulse code, a method is used to reshape the mud pulse signal wave and decode the data at last.In the last part, the principle of MWD System is summarized. Then some hardware equipments of MWD and physical map are shown. Finally, we introduce the framework of the MWD software and the software interface.