Abstract
Foamy solution-gas drive processes in heavy oil reservoirs are very complex. The influence of some microscopic factors on this process is not fully understood due to limitations of traditional depletion tests. This study aims to investigate foamy solution-gas drive by experiments and simulations. First, the effects of the pressure depletion rate on critical gas saturation and foamy solution-gas drive processes were investigated by laboratory experiments. Second, a new three-dimensional foamy oil model that captures many important characteristics of foamy solution-gas drive, such as non-equilibrium behavior, gas evolution kinetics, and the effect of viscous forces on gas mobility, was developed. Last, the effects of some important parameters on foamy solution-gas drive were systematically investigated,and a model application was conducted in a typical foamy oil reservoir. The results indicate that the new model is capble of simulating many of the unusual behaviors observed in foamy solution-gas drive on a laboratory and field scales. High oil recoveries were obtained with a high oil viscosity, high depletion rate, long sandpack, and low solution gas-oil ratio. Foamy solution-gas drive processes are sensitive to the depletion rate, length, and critical gas saturation. The oil viscosity, solution GOR and diffusion coefficient are not sensitive factors.
Highlights
In solution gas drive reservoirs, gas is released from solution when the reservoir pressure is below the bubble-point pressure
Kumar et al.[13] concluded that high oil recovery can be achieved with high depletion rates
Once the pressure is below Pb (Stage 2), the cumulative gas-oil ratio (GOR) remains nearly constant for a period of time, and the cumulative oil produced and oil production rate rapidly increase
Summary
In solution gas drive reservoirs, gas is released from solution when the reservoir pressure is below the bubble-point pressure. Tang et al.[15] investigated the effect of overburden pressure by comparing foamy solution-gas drive in consolidated rock and foamy solution-gas drive in unconsolidated rock They discovered that overburden pressure influences the features of flowing gas bubbles, critical gas saturation and oil recovery. Alshmakhy and Maini[16] reported an experimental study of the effect of gravity on oil recovery They determined that gravity has a beneficial effect on recovery in some conditions because it increases the mobilizing force that is exerted on gas bubbles and encourages foamy oil flow. In addition to these factors, oil, gas and rock properties influence foamy solution-gas drive. The oil recoveries are achieved with CH4 saturated oil are higher than the oil recoveries achieved with CO2 saturated oil[21,22]
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