Experimental Study On Enhanced Gas Recovery By Gas Injection In Tahe Fracture-cavity Super-heavy Oil Reservoir

The reserve of heavy oil is rich, and it plays an important role in global oil and gas resources. At the same time, the increasing world oil demand and declining production in conventional oil recovery lead to heavy oil resource has received increasing attention. The conventional exploitation techniques for heavy oil are difficult to apply in extra-heavy oil reservoirs with large buried depths, so gas injection has received considerable attention to develop this kind of reservoir. In recent years, gas injection to enhance oil recovery is still in infant stage for Tahe fractured-cavity carbonate extra-heavy oil reservoir, and its basic theoretical research hasn't been systematic yet, so it is necessary to expand related theory research, including feasibility, displacement mechanisms and so on.Therefore, in order to effectively exploit Tahe fractured-cavity carbonate extra-heavy oil reservoir, this study has carried out a number of investigations based extensive summaries of displacement mechanisms and research status as follows:(1) The author investigates the basic physical properties of Tahe extra-heavy oil, including density, contents of SARA fractions, rheological properties under the condition of atmospheric pressure and high pressure, and analyzes the influence of temperature and pressure on the oil viscosity. On the basis of high-pressure rheology test, the modified viscosity prediction model for heavy oil under the condition of high pressure is established.(2) The paper analyzes the influence of gas injection on oil physical properties, investigates the effect of temperature and pressure on solubilities and swelling factors of oil with different gas saturation. Then, the viscosities of oil with gas saturation are measured, and the viscosity prediction models for heavy oil with different gas saturation are established.(3) On the basis of above studies, gas flooding physical simulation experiments of fractured-cavity carbonate core are conducted to analyzes displacement mechanisms and feasibility. At the same time, the author finds different extraction phenomena in CO2 flooding processes, and by comparing the oil phase and exhaust gas composition characteristics, the paper analyzes the effect of gas injection parameters on extraction.This paper investigates the oil basic physical properties and the influence of gas injection on oil physical properties, establishes the modified viscosity prediction model for heavy oil under the condition of high pressure and the viscosity prediction models for heavy oil with different gas saturation, and gas flooding experiments are conducted to analyzes displacement mechanisms and feasibility. The study results contributed to give beneficial references to related theoretical study and field application.