In-situ Laser Detection Of Component Content Of Multi-thermal Fluid For Heavy Oil Recovery

For the enhancement of heavy oil recovery,the multi-thermal fluid injection technology is usually adopted relying on the comprehensive effects of multi-component mixed gas（mainly including water vapor,carbon dioxide,and nitrogen）,such as viscosity reduction by heating and dissolution,pressurization and thermal insulation,and expanding the spread range.However,it has been proven that the effects of the stimulation efficiency and the production increase of heavy oil are significantly affected by the component content in the multi-thermal fluid.Therefore,detecting the typical component content of the multi-thermal fluid in real time and accurately provides basic data for the dynamic regulation of injection parameters,which is one of the effective ways to reasonably evaluate the injection capacity.In this regard,the laser absorption spectroscopy technology is believed as a promising way which can deal with the online measurement for the component content within the multi-thermal fluid.Considering the non-infrared activity of nitrogen,water vapor and carbon dioxide are taken as the measured targets.However,there still remains the following problem for the implementation of the laser absorption spectroscopy technology:Firstly,high uncertainties exist in the spectral inversion of component content in conditions of high temperature and high pressur.Additionally,the influence law of laser transmission in a complex flow field environment is unclear.Besides,the optical path layout of laser online detection in limited space is difficult.Given the above problems,the main investigations of the present work are included as follows:1)Spectral inversion method of component content.Based on the screening principle of absorption spectral lines,the absorption peaks of water vapor at 7181.15 cm^-1and carbon dioxide at 4989.97 cm^-1are determined as the measurement spectral lines,which solve the problem of mutual absorption and interference of mixed gases in the process of laser detection of typical component content of the multi-thermal fluid.An improved Savitzky-Golay filtering algorithm based on multiple iterations of the smooth window is proposed to solve the noise reduction and distortion of the original absorption signal in fixed window point mode.The multi peak sampling point mapping method is used to realize the time-frequency conversion,which reduces the complexity of the dual optical path system caused by the addition of F-P etalon.2)High-temperature and high-pressure absorption spectral characteristics of components content.The effects of temperature and pressure on the peak and full width at half maximum of spectral absorbance curve are investigated,and the solution to the failure of high-pressure environment detection and the internal mechanism of high-temperature environment line strength reduction are discussed.A multi physical field coupling model of"non isothermal flow surface to surface radiation"is established,the non-uniformity of the heat flow field in the high-temperature spectrum measuring chamber is analyzed;the spectral absorption discretization model of non-uniform temperature distribution is established,and the main sources and levels of measurement uncertainty of line intensity caused by temperature parameters are analyzed.The line intensity measurement experiments of 7181.15 cm^-1water vapor spectrum and 4989.97 cm^-1carbon dioxide spectrum under medium and high-temperature conditions（326～596 K）are carried out,and the linear correlation between line intensity and temperature with the goodness of fit higher than 0.99 is obtained.3)Influence of complex flow field on the propagation characteristics of the laser beam.The high-temperature stray radiation energy level of the outlet flow field of multi-thermal fluid generator is evaluated,and the stray radiation suppression structure of an off-axis optical receiving system is optimized by using the evaluation method of point source transmittance via an off-axis angle.Based on the numerical model of computational fluid dynamics,the motion distribution characteristics of particles in the flow field and the deformation behavior of droplets attached to the optical window are analyzed.Combined with the Monte Carlo ray tracing method,the influence of nonparticipating media on laser beam propagation is analyzed.The results show that the waveform distortion of spectral signal and burr signal noise is stronger when the particle size is smaller;the larger the droplet shape factor,the more serious the refraction of the optical path.4)Laser detection of typical component content of multi-thermal fluid with the two-dimensional optical path.The structure of multi reflection gas cell with a pipeline embedded annular prism array is proposed.The best optical path layout is obtained by the fuzzy comprehensive evaluation method,and the effective absorption optical path of 173 cm in 15 cm flow section is realized.The feasibility of this scheme in improving the detection signal-to-noise ratio,measurement stability and sensitivity is verified by performance test experiments.According to the dual optical path switching and time division multiplexing,the diesel fuel production system for multi-thermal fluid is designed,and the simultaneous detection experiment of water vapor and carbon dioxide content under combustion injection conditions is implemented.The feasibility of laser detection technology in online detection of typical component content of multi-thermal fluid and dynamic feedback of injection parameters is preliminarily verified.Through the above research work,the tunable laser absorption spectroscopy technology has been successfully applied to the measurement of typical component content in the multi-thermal fluid injection process.It overcomes the shortcomings of the traditional contact sampling method,such as the probe intrusion easily interfering with the flow field to be measured,and the aging extension of the measurement results.It solves the technical problem that the high temperature and complex environment of the flow field in the multi-element hot fluid injection process interfere with the detection results of component content.The on-line dynamic measurement of water vapor and carbon dioxide injection content is realized.It can provide data support for real-time monitoring and optimization control of heavy oil injection multi-thermal fluid.