Variations Of Physical Properties And Control Measures Of Formation Damages During Steam Injection In Heavy Oil Reservoirs

According to geology characteristics and recovery processes of heavy oil reservoirs in Henan oil field, some experiments, such as oil-water and gas-liquid relative permeability behavior, wetting behavior, variations of petroleum components and physical properties, alteration of formation properties, water-rock reactions and water-liquid reactions, are carried out to summarize the mechanisms of formation damages in heavy oil reservoirs during injection steam. At last, the measures of improving recovery efficiency are brought forward aiming at formation damages during injection steam in heavy oil reservoir.Firstly, recovery mechanisms of steam flooding are researched to analyze high-temperature relative permeability behavior according to the displacement experimental results on conventional heavy oil, extra heavy oil and super heavy oil during injection steam and hot water. Reservoir temperature gradually increases to result in variation of rock surface wettability from oil wetting to water wetting. Therefore, irreducible water saturation increases and residual oil saturation gradually decreases as reservoir temperature increases.Secondly, physical simulation experiments at high temperature are employed to studied formation damages resulting from water-rock reactions, water-liquid reactions and asphalt deposition during steam injection. The content of light hydrocarbon obviously decreases but the content of heavy hydrocarbon and asphalt largely increases in steam swept formation during steam injection.Thirdly, the methods such as mercury penetration, casting sample, scanning electron micrographs, grain size analysis and etc are utilized to analyzed variations of pore structure and formation properties during steam injection. Many new effective technologies are promoted to decrease formation damages and to increase recovery efficiency according to the mechanisms of formation damages and variations of reservoir properties during steam injection.Because new technologies were employed in Jinglou and Gucheng oil field in the lastst three years, accumulative oil production got to 9.4138×10~4t and accumulative oil-steam ratio was to over 0.36. The technologies can be widely applied in enhanced oil recovery during injection steam in heavy oil reservoirs.