Design And Implementation Of Centered Gamma Rays Logging While Drilling Instrument

Logging While Drilling(LWD)instrument is to judge and control the borehole trajectory in real time through the actual geological features of the drilling process,for the target formation has high accurate directivity.Generally,in normal drilling speed,logging while drilling instrument measurement speed is lower than the speed of the cable logging,so data in unit time get large amount,not only the high real-time,but also to avoid the logging cable first drilling logging generated by the time interval in the mud and the influence of drilling fluid for borehole washout.Thus,the logging while drilling instrument can provide more detailed and accurate logging data.Centered Gamma Rays(CGR)logging while drilling instrument under the condition of drilling measuring formation natural gamma ray intensity,and the measured values from Measurement While Drilling(MWD)system in real time and uploaded to a ground system and ground system for on-site geological engineer provides data of the analysis of the current drilling bit stratigraphic lithology,formation evaluation and assessment.At present,only a few LWD with the introduction of foreign equipment and near bit parameters and the drilling tool instrument of geological parameters,logging while drilling centered Gamma rays instrument is still blank in China.So the development of a complete system of domestic LWD instrument has very important significance.This dissertation first systematic introduces the theoretical basis of radioacti-ve logging while drilling technology development status both at home and abroad,expounds the design methods of logging while drilling centered Gamma rays measuring instruments and measures to improve reliability.It has an in-depth analysis on the development significance of the logging while drilling centered Gamma rays instrument,radioactive logging geological foundation,and the interaction principle between rays and matter,scintillation detector working principle and signal processing method and software control process,calibration method,and the calibration of the measured values and so on.In order to satisfy the requirements of the logging while drilling,the main of the design:Firstly,to study the principle of detector and selection of detector and high voltage module through a lot of experiments,under the condition of complete the basic function of the circuit,and focuses on the characteristics of gamma detector for some details of the circuit design to keep the Gamma detector count rate reliable and stable,secondly,microcontroller usesCode Warrior IDE tools for development,real-time response of down hole MWD control commands and through the IIC bus connection memory,real-time storage of measurement data,parameter storage,preliminary data processing and other functions;third,based on the design codes of Mechatronics,Cooperating with mechanical staff to discuss the design scheme for a processing of CGR.The mechanical parts will continue other designs with the same size instrument,vibration resistance and compression to achieve a unified standard and consistent interface between power supply and communication;forth,the influence of the environment and the well thickness to the gamma value of the instrument measurement is corresponding to the calibration and correction,writing the calibration factor which we get into the instrument with serial port to make the minimum error.This project provides a new logging while drilling tool for the petroleum geological exploration and development drilling,which has an important role in improving the drilling rate and reducing the total cost of exploration and development.