The Authigenic Co <sub> 2 </ Sub> Technology Systems And Oil Displacement Efficiency Study

In-Situ Generation of Carbon Dioxide is a new technology of enhancing oil recovery, which generate CO₂ in place by means of injecting of gas-generation reagent system, then enhance the oil recovery by the effects of oil swelling, viscosity break, pressurizing and so on. This technology have the virtue of simple process, controllable influx, unlimited gas source and adaptability, the potential of application is strong.This text select the reacting system by the guideline of gas-generation efficiency and cost factor and so on, and have study on the optimum system further. The optimum system of single-fluid method is salt A, the gas-generation rate and gas-generation efficiency improves along with the temperature increasing and the concentration augmenting. The best mass concentration of salt A is 20 percent. At the temperature of 50 to 80℃, the gas-generation efficiency all can exceed 80 percent the gas-generation efficiency can be enhanced by injecting acid follow-up. The best system of double-fluid method is salt B-acid M, the gas-generation rate increases along with the injection rate speeding and the temperature increasing and the reaction fluid concentration augmenting, but these factors is impervious to gas-generation efficiency of double-fluid method, it can exceed 90 percent by and large. At the condition of reservoir, the result of oil swelling and viscosity break experiment shows that the effect of in-Situ Generation of Carbon Dioxide is obvious, the oil more viscous, the better. When temperature at 70℃, pressure at 6MPa, the oil with 12904mPa·s viscosity swelled about 32.5 percent. When temperature at 70℃, pressure at 10MPa, the oil's viscosity breaked 54.3 percent from 3120mPa·s. Making a study of the infection of the pH value, salt concentration and salt category to the gas-generation rate and gas-generation efficiency of the gas-generation system, and study on the formation damage caused by the existence of bivalent cation using sand packed model. The results of the experiments improve that the pH value within 4 to 10, and the existence of Na⁺ ion,K⁺ ion,Cl^- ion,SO₄^2- ion,NO₃^- ion have no influence to the the gas-generation rate and gas-generation efficiency of the gas-generation system. If the concentration of Ca²⁺ ion in formation water is higher than 1000mg/L, the damage of single-fluid method to the formation is obvious, the permeability of the model fall by 47.3 percent when the concentration of Ca²⁺ ion is 5000 mg/L and the permeability is 336.5×10^-3μm² and the influx is 0.5PV with mass concentration of 10 percent. Single-fluid method with injecting acid follow-up and double-fluid method causes no damage on the whole. Having a study on the oil displacement mechanism by the microcosmic model, as a result, the displacement capacity of In-Situ Generation of Carbon Dioxide is strong, taking on the effects of oil swelling, viscosity break, displacement and so on. Making a study on the oil displacement efficiency by the sand packed model, the results shows that the oil recoveries enhance 7.6 to 14.2 percent after water flooding by the method of displacement. To the method of huff and puff, the effect is better when huff and puff first and water flooding following, the recoveries of water flooding is about 29.5 to 32.3 percent, and the recoveries raised to about 36 to 43.7 percent. Having carried on a field test by the means of single-fluid method and injecting acid follow-up, the result improve that the method of in-Situ Generation of Carbon Dioxide is effective to a certain extent.