Study On Phase Phase And Seepage Mechanism Of Improved Oil Recovery In Gas - Buried Gas Reservoir

This paper comes from a gas condensate reservoir development subject of Northwest Oilfield Branch, Sinopec. The purpose is to discover the phase behavior and flow mechanism in gas injection of Dalaoba2nd gas condensate reservoir, then provide a technical support in gas injection for Northwest Branch.In the middle-late period of gas condensate reservoir development, when formation pressure deplete to the dew point pressure, anti-condensate becomes serious, thus resulting a large accumulation of condensate in the wellbore-near section, condensate recovery is very low, so we need to find a way to improve condensate recovery in this period. In this paper, we use a series of comprehensive analysis methods to analyzed the mechanism of gas injection in Dalaoba2nd gas condensate reservoir, such as gas injection phase behavior experiments-flow characteristics experiment and long core flood experiments. Then analyzed the inject and production capacity in Dalaoba2nd gas condensate reservoir. Finally, we briefly analyzed the effective case in field pilot test. Through the above research. we conduct the following conclusions and understanding:(1) Phase experiments in well DLK4shows a high level of intermediate hydrocarbons and heavy component in the well stream, which belongs to a low gas-oil ratio with high condensate content system; when deleption to10MPa. the condensate recovery degree only reaches18.74%, the gaseous water content increased significantly while deleption.(2) Considered porous medium effect’s phase test shows:Porous media has an obvious effect on composition and anti-condensate degree, while has little effect on dew point, viscosity and solution gas-oil ratio, etc. In actual development, should consider the impact of the porous medium in formation.(3) Gas injection long core flooding experiments shows:depletion development in Dalaoba2nd gas condensate reservoir gets a low condensate recovery, which is unsuitable for development. Inject gas in the current formation pressure, the condensate recovery improved marginally, so appropriately increase the injection pressure to maximize condensate recovery is necessary.(4) Condensate anti-evaporation experiments shows that:injecting2PV dry gas in formation pressure condition, the total condensate recovery reaches86.22%; component analysis shows that gas injection can evaporate the intermediate hydrocarbons and heavy component, and the presence of porous medium is advantageously for the anti-evaporation.(5) The injection and production ability analyze showes that gas injection is feasible in the2nd gas condensate reservoir, and the reasonable production pressure drop is1.23.3MPa.(6) Gas injection effect analysis shows that in the2nd gas condensate reservoir to improve condensate recovery by gas injection have achieved initial success.Thus, in the middle-late development period of Dalaoba2nd gas condensate reservoir, there’s lots of oil condensated, and large edge-bottom water yield, so we should consider a dry gas flooding at high pressure to improve condensate oil recovery. improve condensate recovery...