| Tight oil refers to clip in or close to the density of the high quality source sequence clastic rock and carbonate reservoir, without long distance migration and formation of oil accumulation. in continental sedimentary basins China are widely distributed tight oil, and has been in Ordos, Songliao, Junggar Basin, so as to obtain some important discoveries. This natural energy is generally small, properties of crude oil is better, mainly light crude oil-based, underground flowing condition is better. The occurrence state of tight oil mainly displays in three aspects:First, crude smeared on the surface of the particles in film form; Second crude oil develop within the pores between particles in short columnar collection, sticking together; Third crude oil bond in the two wall of cracks. Dense oil reservoir, because of its reservoir lithology density, high seepage resistance, pressure conduction ability is poor, In reservoir is difficult to establish effective displacement system.Then dissolves oil by supercritical fluid strong force to carry and spread out through the hole, in the process, to realize the exchange between supercritical fluid and crude oil. Making it available in not need through the establishment of effective displacement pressure system, Used for oil extraction (extraction) function exploitation of crude oil, so that they don’t need through the establishment of displacement pressure system, can realize the extraction of crude oil. First of all, the supercritical fluid dissolved molecules by molecular diffusion into the reservoir in the matrix, and the inside of the matrix oil mass transfer effect, make its dense oil dissolved in supercritical fluid. Supercritical CO2with the dual characteristics of gas-liquid two-phase, which has relatively high gas diffusion coefficient, low viscosity, similar density as the liquid and good ability of dissolve material, showing a great excellent solubility, delivery and flowability. The application of mature supercritical fluid extraction technology in other fields apply in dense medium crude oil extraction, providing some useful guidance for studying mining this type of crude oil.The paper analyze the conventional fluid extraction mechanism of solid materials, base on the view of the association of the solvated, proposing association of supercritical fluid extraction mechanism, resulting in establish a mathematical model of the association supercritical extraction of solid materials. By analyzing and solving the momdel of extraction mathematical, macro extraction rate of mathematical equations are obtained; and then the experiments have been carried out to verify the established mathematical model. We find that within30min-120min, macro extraction rate decreasing gradually, in the period of120min-180min, macro extraction rate keeping unchanged.Based on the basic understanding of the tight oil reservoir properties, we depth study the laws of supercritical CO2extraction of oil saturated core through experiments, and analyze the influence of various parameters on the extraction rate. The research results have shown:When extracting the oil saturated core, the extraction rate increases with increasing pressure, and increases fastest in the vicinity of the critical point; The influence of temperature on the extraction rate is relatively complex, there will be a extraction rate decreaseing situation; Extraction rate will prolonge with immersion time and cycle time increases,120min is best, and there is no last increase basically. Optimal parameters under the experimental conditions of the program is:pressure20MPa, temperature50℃, immersion time120min, cycle time150min, reaching maximum extraction rate at this time. Compared with common solvent wash oil rate, the efficiency of supercritical CO2extraction has great advantage. |
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