Scheme Design Of Ultrasonic Logging While Drilling Caliper Detector And The Implementation Of The Processing And Storage

Diameter is an important decision-making information in the drilling process, there are many applications on rock physicists, geologists and drilling team. However, real-time measuring diameter is still a difficult problem in LWD, mainly in the drilling process can only be measured diameter wells in a non-contact measurement method, and the available non contact measurement method is very limited. On the other hand, during drilling downhole high temperature and high pressure, rotation, vibration environment make the detection condition is very harsh, resulting in accurate real-time measurement becomes very difficult; furthermore, the downhole drill collar for detecting instrument circuit space is very narrow, it puts forward higher integration requirements to the existing scheme detection device. Ultrasonic ranging is currently the only alternative, but because the environment in the drilling mud ultrasonic attenuation great, how to detected the weak ultrasonic echo signal has become a key issue.In this paper, the subject of ultrasound caliper measurements in LWD was analyzed, focusing on the research of full waveform ultrasonic echo data real time storage and weak ultrasonic echo signal detection. First, according to modern digital signal processing theory, proposed a first ultrasonic echo signal arrival time detection method. Second, in view of the problem to a large number of data real-time transmission to the ground, proposed a large capacity data storage solution based on Nand Flash and developed the corresponding storage circuit. Third, according to the instrument with low power requirements, processing and storage module uses the power saving mode, greatly reduces the power consumption equipment.Prototype has passed the high temperature (155℃), high pressure (140MPa) and vibration (20G) tests and several field log tests. The results show that the scheme can detected the first wave arrival time accurately from the weak echo signal under the large proportion of mud environment, make real-time storage of full wave train echo is very accurate, and make the whole instrument working current is lower than150mA. It meets the requirements of LWD, and has important practical value in the drilling diameter measurement.