Heavy Oil/Bitumen Recovery by Alternate Injection of Steam and Solvent (Hydrocarbon and CO2) in Fractured Carbonates and Oilsands.

摘要

The world energy demand is constantly increasing and fossil fuels are still by far the main energy resource that supplies the world energy consumption market, therefore increasing oil recovery from all types of reservoirs is an important matter. The burning of fossil fuels for energy purposes, on the other hand, emerges another issue: the accumulation of greenhouse gases into the atmosphere which is considered to be the primary cause of climate change. CO2 sequestration is a way of mitigating this greenhouse gas from the environment and storing it in underground reservoirs. Naturally fractured reservoirs may be worthy locations for CO2 storage and if a suitable method of injection is applied, both oil recovery and CO 2 sequestration goals can be met simultaneously.;Steam-Over-Solvent Injection in Fractured Reservoirs (SOS-FR) is a recently proposed method for heavy oil recovery from fractured reservoirs. This method normally consists of three phases: Phase-I, initial thermal phase that produces oil by thermal expansion and viscosity reduction; Phase-II, solvent phase to dilute and drain oil and; Phase-III, final thermal phase for additional oil recovery and solvent retrieval.;This dissertation extends and modifies the SOS-FR method to employ CO 2 as solvent through extensive experimental and numerical analyses. The experiments were conducted under various pressure and temperature conditions on different porous media including preserved oilsand ores, unconsolidated sandpacks, sandstone, and carbonate cores. While CO2 was of central interest, different solvent types were investigated to form a range of comparisons. Solvents were examined in both liquid and gas forms. Temperature was changed for thermal stages to consider hot water, low temperature steam, and high temperature steam. Pressure was also changed in solvent stage. Oil, gas, and porous medium analysis were performed to see the effects of SOS-FR on fluid and matrix properties, as well. Numerical analysis was also done for history matching of experimental data and field scale application of this method to see the results of various injection schemes on both oil recovery and CO 2 sequestration in larger scales.;This work presents the applicability of carbon dioxide as solvent in the SOS-FR method which gives acceptable oil recoveries while reducing the costs of solvent and steam with an additional value of CO2 storage in naturally fractured reservoirs or post-CHOPS oilsands applications. It is shown that the method is viable and effective for a wide range of applications from unconsolidated sands to fractured carbonates containing heavy-oil and bitumen through vigilant selection of steam-solvent injection strategy ad solvent type under general SOS-FR concept.