Design Of Downhole Telemetyr Unit In The Single-core Logging System For High-speed Communication

As a valuable and non-renewable resource,oil has played an irreplaceable role in human societies. The continuous development of modern industry increases our demands for oil, however, we are facing a great shortage of original oil resources, many oilfields entered the late-stage development. How to grasp the underground oil storage situation accurately, developing oil as efficiently as possible are the problems which need to be solved in the current oil well logging technology. The research content of this paper is based on this background.Low cost and easiness to go down into well make single-core cable become an important part of oil well logging technology. The data transmission rate of the currently used single-core cable logging system is very low, with imaging logging and combination logging technology evolved, more and more data in well logging is needed, low-rate transmission can not meet the actual requirement of application development. How to improve the transmission rate of single-core cable logging system is one of the contents in this paper. The gamma spectroscopy logging instrument and azimuth instrument we currently used in the cable logging system are two separate instruments, in order to shorten the length of the downhole tool string, the design of digital azimuth-gamma instrument combining with the digital signal processing technology is anther content described in this paper.This paper mainly focus on downhole telemetry unit of single-core cable logging system, the main work is as follows:1、Using a network analyzer to measure the S-parameters of 7,000 m single-core cable and analyzing its transmission characteristics, This help me determine the available bandwidth during transmission.2、When having enough knowledge of channel transmission characteristics, this paper hope to make the upstream rate up to moer than 200 kbps or and then determining the overall communication solution of logging system. OFDM modulation is used in the uplink channel transmission. Designing the downhole modem, doing the programming and debugging based on the CCS. After the final system testing, the transmission rate of single-core cable telemetry system can achieve 221.6kbps, meeting the requirement of the project, the transmission rate has greatly improved.3、In order to shorten the length of the downhole tools string, this paper analyzes the working principle of traditional gamma spectroscopy logging tool and azimuth instrument, integrates the gamma spectroscopy logging instrument and azimuth instrument into the telementry uint with the digital signal processing technology and digital signal processing(DSP),this will make the structure of downhole tools more simple, the system will be more stable.