تزریق همزمان گاز غیر هیدروکربنی و بخار برای ازدیاد برداشت

Non-hydrocarbon gas injection followed by steam–gas co-injection forheavy oil recovery enhancement from fractured carbonate reservoirs
Abstrat
Considerable heavy oil is accumulated in naturally fractured carbonate reservoirs, with very low oil recovery efficiencythrough costly production techniques. In this experimental study, the effects of different non-hydrocarbon gases on theperformance of gas injection process followed by steam–gas coinjection on heavy oil recovery from low permeable full sizedcarbonate cores were investigated at reservoir conditions in a long fractured laboratory model. Three different gases: pure CO2, pure N2, andtheir mixtures as syntheticflue gas were used to study the performance of gas injection process. Also, thetests were continued by steam–gas co-injection process that gas was injected with specific steam/gasratio at steam saturation temperature condition. In the course of experiments, oil and water productions,pressure and temperature were monitored carefully.It was found that during fracture depletion, the piston-like displacement by N2 injection and oilfoaming by CO2 injection are the most important mechanisms affecting the oil recovery performancebefore gas breakthrough. The results showed that after gas breakthrough (GBT),the ultimate oil recoverybased on residual oil at GBT for CO2 injection was 58.4% (14.8% by gas injection and 43.6% by steam–gasco-injection),forflue gas injection was 73.8% (9.8% by gas injection and 64% by steam–gas co-injection)and for N2 injection was 47% (13.5% by gas injection and 33.5% by steam–gas co-injection). The results ofoil recovery and production rate indicated that theflue gas injection during gas injection and steam–gasco-injection processes was outperforming for heavy oil recovery enhancement from fractured reservoirs