Ultrasonic Imaging Logging Instrument Based On OFDM Communication

With the exploration and development of oil and gas field,the oil well testing ismore and more important means of achieving in geological information, detecting thedamage condition of the wall. A complete oil well testing system includes function ofacquisition, transmission, storage, analysis. It constitute by underground instrument,data transmission, ground equipment, auxiliary equipment. With the rapiddevelopment of well logging technology, the underground instrument needs a greatspeed of the real-time data transmit to the ground instrument. Single core cable supplythe electricity of the instruments underground. At the same time, it also need totransmit the data and command control of the instruments underground. Because thelogging cable channel environment is awful, the frequency of communication is low.In order to increase the speed of communication, orthogonal frequency divisionmultiplexing technology to solve these problems.Ultrasonic borehole scanning imaging measuring instrument is scanning imagingof borehole wall using the ultrasonic echo signal. The instrument detect the receivingthe ultrasonic signal.Data processing and compression should be need, because datacan not be transmit by analog signal. A high speed data transmission could be realizedby the technology of OFDM carrier communication. Ground instrument of thedemodulated data transfer to PC. It is processed by the host computer.Computercharge to display the wall thickness, corrosion and damage. This ultrasonic imaginglogging instrument is mainly designed for the borehole wall. Satisfied fieldenvironment of the temperature and other stringent requirements, the system is stableand reliable.It has certain practical and reference value.This paper introduces the technology of orthogonal frequency divisionmultiplexing. A simulation and experiment on the sub carrier modulation anddemodulation had been made. The production log channel had been analyzed. Makefull use of single core cable bandwidth. The rate of single core cable logging had beenimproved. The transmitting and receiving circuit and data transmission circuit hadbeen designed. Ultrasonic transmitting and receiving circuit is mainly composed of aboosting circuit, drive circuit, a limiter circuit, amplifying circuit. Transmission circuit is mainly composed of a coupling circuit, filter circuit, the analog front-endcircuit, a modulation and demodulation circuit, interface circuit. Test shows that, byultrasonic transmitting and receiving circuit can accurately measure the thickness ofspecimen. Through the modulation and demodulation of communication circuit,logging cable can be transmitted in a high-speed data transmission rate. Theexperimental conclusion is relatively detection of the small diameter borehole wall. Ithas the certain reference value.