Echo Signal Detection And Digital For Ultrasonic Drilling Logging Instrument

In the process of oil&gas exploration and development, logging must be carried out after drilling, in order to understand the formation of oil and gasbut the acquisition of logging data always after drilling completion,using the cable put the instrument into the well to measure.However, in some situations,such as a slope of more than65degrees highly deviated wells and horizontal wells, cable is difficult to put down the instrument.Due to drilling fluid circulation in drilling process out of the drill out cuttings, drilling fluid filtrate invasion formation, so the formation of drill again after the log by the various parameters of drilling and formation is different.In logging while drilling to obtain formation parameters is just drilled formation parameters, it is the most close to the formation of the original state, used for complex formation of oil and gas evaluation more advantageous than ordinary wireline logging.At present, the logging while drilling technology in the application process has been facing a series of technical problems, so the research and development with independent intellectual property rights of ultrasonic caliper with drilling instrument is of great significance.Ultrasonic drilling logging instrument mainly by detecting the echo time and echo amplitude information to reflect the subsurface structure and characteristics of the borehole wall.Instrument as a whole design can be divided into the following several modules:Excitation and receiving module.Excitation signal generated by FPGA,transducer receives the echo signal into the signal acquisition module for related processing.Signal acquisition module:Receives the echo signal from Excitation and receiving module,according to echo attenuation regularity of signal voltage controlled amplifier and bandpass filter and then sent to the A/D converter after level polarity conversion to digital.Control and storage module:According to the command from the ground system, produce the corresponding control command and temporal logic control circuit according to the requirements of the underground work pattern, at the same time the temperature signal is digitized and underground power supply voltage,then the detection of echo data, the temperature data formatting, location information and data set of frames,for storage and sample sending,Finally, in the module of echo data real-time processing extract hole diameter information. Transport module:Main implementation USES QBUS and RS485bus structure and ground systems for communications and data transmission, at the same time to facilitate the debugging of the circuit design of underground a RS323communication interface, easy to communicate with PC.Power supply module:Provide downhole circuit need three sets of power supply.Logging while drilling technology is first introduced in this thesis, both at home and abroad development situation, through the analysis in this paper, the necessity of ultrasonic logging instrument design, pointed out that in the process of instrument research and development required to achieve the indicators and the problems faced by.Then proposed the overall scheme of the system design, tells the story of excitation and receiving module, signal acquisition module hardware circuit design, FPGA logic sequence control module design.Finally, experiments verify the feasibility of hardware circuit design, and puts forward the design of the deficiencies and to improve.Compared with the traditional cable ultrasonic imaging logging instrument, its main technical improvement is:1.On the choice of electronic devices as far as possible a military level chip, high integration devices instead of separation of the original, the device as far as possible on the encapsulation of the patch.2.Reduce the frequency of transducer, to facilitate the measurement of heavy mud environment.3.Adopted a new trigger circuit, improve the efficiency of the electroacoustic transformation, strengthen excitation waves of energy.4.According to the attenuation law of ultrasonic wave in the medium over time, USES the high performance voltage controlled amplifier, along with the change of time for continuous variable gain amplifier, of echo signal attenuation of the signal compensation mud medium.