Design Of Main Control System Of Logging While Drilling Caliper Tool Based On Ultrasonic

In the process of petroleum exploration,logging technology plays an important role.Logging while drilling(LWD)tool has been developed rapidly in recent decades because of its unique advantages,which can overcome the shortcomings of cable logging tool that can't measure horizontal wells and highly deviated wells.In many petroleum well information,well diameter is an important parameter.When using LWD tool to measure the diameter of a well,in addition to high temperature resistance,high pressure resistance and vibration resistance,the instrument is also required to have the characteristics of non-contact measurement,high real-time performance and strong anti-interference ability,so it is a feasible method to measure the diameter of the well by using the ultrasonic distance measurement.Ultrasonic LWD caliper tool is mainly composed of main control circuit board,acquisition circuit board and transmission circuit board.and the main control system is the core,which connects the acquisition board and the central control system.The instrument not only measures the caliper value,but also measures the tool face angle and other auxiliary parameters.The main works and the study of this thesis are as follows: According to the attenuation law of ultrasonic echo signal,the echo signal compensation method based on time-varying gain(TVG)amplifier is designed;According to the characteristics of the tool face angle under the well,magnetic north mode and high side mode are adopted,and the error correction method of electronic compass and inertial sensor is designed to reduce the measurement error of the tool face angle;According to the connection characteristics of the instrument communication interface,the above-well communication bus and the under-well communication bus are designed;According to the characteristics of the collection process of the instrument,the control program of the overall working process of the instrument is designed;In order to solve the problem that the instrument can only upload a small amount of critical data to the ground while a large amount of logging data can't be transmitted in real time,a large-capacity data storage module is designed to mark the data with time stamps and then store it in a fixed format under the well.In the thesis,the development of LWD tool and the research status at home and abroad are introduced,and the necessity of developing the instrument is pointed out.Then the working principle of Ultrasonic LWD caliper tool,the compensation method of echo signal and the basic principle of tool face angle measurement are intruded.The source of measurement error of tool face angle is analyzed,and the correction method is put forward.Next,the design of each module of the instrument is introduced emphatically from the hardware design and software design.According to the functional requirements of the instrument,the MCU with DSP unit as the core of the hardware circuit is designed.The peripheral circuit includes data storage module,tool face angle acquisition module,multi-channel communication interface,power monitoring module and auxiliary parameters acquisition module.At the end of the thesis,each functional module of the instrument is tested,and the test results are analyzed.Through the analysis of the test results,the integrity of the instrument function is verified,and the design indexes are basically achieved.