| Downhole TV is a kind of logging tool for understanding,evaluating and intervening in the oil and gas wells.That uses the downhole camera to obtain video images directly.It has been applied to the monitoring and detection of oil and gas wells successfully.At present,downhole TV is dominated by single-camera and dual-camera logging tools.Single-camera and dualcamera logging tools can obtain intuitive and smooth video images and the satisfactory results are achieved,but there are still some shortcomings.The logging tool of single-camera can not take images at a vertical angle to the well wall.There are large distortion and indistinct details in the acquired images.The camera coverage of the dual-camera logging tool is finite and the viewport may be selectively rotated 360 degrees by a motor assembly positioned within the logging tool to obtain side-view images.Therefore,the operation efficiency is low and it is easy to miss the target.In this paper,a multi-camera combined logging method is proposed,and a prototype of visual logging tool that uses down-view cameras and array side-view cameras to obtain axial ultra-wide-angle and 360 degrees video images around the well is designed.The whole axial and radial high-definition video image data of wellbore are successfully obtained in one well logging,which improves the efficiency of logging.The main work can be summarized as follows:(1)The overall scheme design is proposed.The composition and principle of Video Log visual logging system are introduced,the design requirements of multi-camera combined logging are proposed,the feasibility of the scheme is demonstrated,and the overall scheme of the system is obtained.According to the specific scheme,the module is refined and the device selection of each module is completed.(2)The hardware circuit of the system is designed.The hardware circuit design of video image acquisition,SD card storage and Ethernet transmission are realized based on the Hi Silicon Hi3516 chip.The hardware circuit design of the measurement and control module is completed based on the STM32 main control chip,including the hardware circuit of temperature measurement and light source brightness control.Finally,the network switch module circuit and the power supply system of the logging tool are designed to realize the packet forwarding of multi-channel data and the power supply of each module of the prototype system.(3)The software design of the system is completed.The main program and subroutine of video acquisition and processing,SD card storage program and video data transmission program are designed.The communication control and communication protocol design of the main controller of the measurement and control module are realized.The measurement and control data transmission program,the temperature acquisition program and the light source brightness control program are designed.(4)The function of the prototype system is verified.An experimental test platform is built to complete the basic functions and temperature resistance of the video acquisition and processing module,the measurement accuracy of the temperature acquisition module,the dimming operation of the light source module and the data transmission test of the switch module.The test results are analyzed.Finally,the overall function of the prototype system is verified.In order to obtain high-definition,smooth and accurate downhole video image materials and improve the efficiency of logging tool operation,a prototype system is designed based on the method of multi-camera combination logging in this paper.The results of the laboratory experiment show that the prototype system can transmit video images with a frame rate of 25f/s and a resolution of 1280?960 in real time.The temperature measurement accuracy is ?0.5℃,which can achieve four-level dimming and achieve the expected results.It is helpful to improve the accuracy of downhole TV image measurement and provide a more intuitive and accurate video basis for the formulation and implementation of downhole operations. |
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