Research Of Ultrasonic Logging While Drilling Tool

In recent decades,in order to solve the logging problems of highly deviated wells and horizontal wells,accurately obtain the original formation information,and timely guide the drilling work,logging while drilling technology has been more and more applied in oil and gas exploration.In many logging parameters,the well diameter is an important decision parameter.In addition to high-temperature and high-pressure and anti-vibration,it is also required to have the characteristics of non-contact measurement,high real-time performance and strong anti-interference.In this dissertation,according to the principle of ultrasonic reflection ranging,using its characteristics of non-contact,non-destructive,real-time and accurate,a prototype of ultrasonic logging while drilling tool is designed,and some problems are studied.The main work and innovations of this dissertation are as follows:1.Aiming at the space constraint of slim hole(diameter less than 216mm)logging environment,this dissertation designs a data acquisition circuit board with the width of 26mm.It mainly includes system control circuit,excitation signal generation circuit,echo signal receiving circuit,transducer switching control circuit,signal amplification circuit and signal sampling storage circuit.The feasibility of the system circuit design is verified by experiments.2.In order to overcome the problem that the echo amplitude is too large or too small in different environments,this dissertation designs the automatic gain control algorithm of the echo signal to ensure that the echo signal is in a reasonable range.At the same time,based on the cross-correlation algorithm,the diameter detection of ultrasonic logging tool is realized.Based on this algorithm,the transit time measurement experiment is carried out,and compared with threshold method.The results show that the error of cross-correlation algorithm is smaller,within 2%.3.In order to overcome the situation that the primary echo signal can not be used to measure the transit time due to the partial loss of the primary echo signal in the near distance,this dissertation uses the secondary echo signal to measure the distance.The results show that the distance can be measured when the ultrasonic transducer is close to the borehole wall,so as to improve the measurement range of the instrument.4.The prototype of ultrasonic logging while drilling tool is built.On the basis of the prototype,the well diameter measurement experiment is carried out,and the experimental results show that the prototype can get more accurate well diameter,and the error is less than 3%,no matter in large diameter or small diameter wells,for the drill collar in different eccentric positions,which verifies the feasibility and effectiveness of the prototype of ultrasonic logging while drilling tool.