Research Of Insulated Tubing Vacuum Test

Steam process oil extraction was the vital method of thick oil exploitation. The vacuum level of insulated tubing affected heat insulation capability, and then affected the exploit effect of steam process oil extraction. Therefore, how to test the vacuum level of oil pipeline is the important research direction of steam process oil extraction. In the project, we used capacity vacuum micro sensor as test cell, adopted PZT piezoelectric crystal converse piezoelectric effect on its resonant frequency, and combined PIC16F876A with some related signal processing circuit. Thus measured the vacuum level of insulated tubing successfully. This dissertation launches the following research:1,Analyzed factors that affect the oil pipeline's heat insulation capability, such as heat conduction,convection current and radiation. Confirmed that convection current was the main cause of heat elimination, and that vacuum level was the main performance index of oil pipeline's heat insulation capability. According to enclosed property of the oil pipeline, the test project. was designed.2,The capacitance that tested by capacitive vacuum micro sensor was smaller than the parasitic capacitance, so a capacitance voltage converter that was composed of preamplifier,correlated double sampling technology and delta modulator was adopted as capacitance test circuit. Another compensatory capacitance was added in this circuit to eliminate the influence of the parasitic capacitance. Correlated double sampling technology and delta modulator were applied to attenuate low-frequency and high-frequency noise, and realized the capacitance-voltage conversion3,Within the insulated tubing, signal that generated from CVC capacitance test circuit was collected and analyzed by PIC16F876A. Through PZT piezoelectric crystal converse piezoelectric effect on its resonant frequency, the system can communicate with outside by USART. 4,The principle and structure of PZT piezoelectric crystal had some defects. The impulse signal that pass through it were distorted and interfered. So a signal process circuit that can process the output signal generated by PZT piezoelectric crystal was designed, and it solved the signal distortion and interference.5,The test system required small bulk and low power consumption. In software, MCU system work mode and I/O port were analyzed and set. In hardware, system power and clock frequency were analyzed and set. A power system based on monocell and Dickson charge pump was designed, and it reduced system bulk and system power consumption.6,The signal from the after-signal processing circuit by MATLAB was collected and analyzed according to moving average and least squares theory, the contradiction between the maintenance of signal integrity and the removal of signal interference under high-speed test was solved.According to the existing literature, there were some progresses about the study of insulated tubing vacuum test on abroad. some of those methods cost, and some difficult to achieve, some only qualitative measurement, not quantitative measurement. There were few related research reports at home. Therefore, there is certain practical and theoretical significance about the issue.