| The heavy oil is characterized by high viscosity, big density and poor fluidity whichcauses that the routine thermal recovery cannot satisfy the exploitation requirement of theexisting oil reservoir for its defects of high cost, low efficiency and high consumption. CO2has received more and more researchers’ attention as a new technology of improving theproduction effect of super heavy oil. This paper first studies the influence of CO2on thephysical properties of heavy oil and reservoir flow properties which demonstrates that thedissolving ability of CO2in crude oil appears to be four times more than that of natural gasand twelve times or so more than that of N2; the viscosity reduction rate of CO2for crude oilcan reach96.15%, much higher than that of N2which can reduce the viscosity by21.9%; thevolume factor of oil after dissolving CO2increases more than14%, much higher than theeffect of N2and natural gas; CO2can extract the light weight fractions of super heavy oil inthe formation and therefore, enhance the oil recovery. The experimental results show that CO2affects the reservoir flow properties, and that the temperature and pressure, compared withsalinity, which has a greater impact on the solubility of CO2in water. And also, the CO2injected has little influence on the permeability of core. This paper carries on the study onimproving the production effect of super heavy oil with CO2and the mechanism analysis ofenhancing oil recovery in the indoor experiments. To inject CO2and surfactant concurrentlyover the process of high-temperature steam flooding, not only can it enhance the recovery ofcore barrel with high permeability, but also it can enhance that of core barrel with lowpermeability, and the ultimate recovery appears to be40%higher, compared with that ofsingle steaming flooding. The results of field application show that the technology of CO2auxiliary steam thermal recovery effectively develops some super heavy oil blocks in Shenglioilfield with significant application effect. |
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