底水砂岩气藏注CO2驱气提高采收率机理及埋存效果OA北大核心CSTPCDEI

CO2 flooding has been widely applied to EOR,but so far,few researches have been carried out on the collaborative development of CO2 flooding and storage in bottom-water sandstone gas reservoirs,and the natural gas displacement mechanisms of gaseous CO2 and supercritical CO2 and their differences have not been clarified.In order to improve water intrusion of bottom-water sandstone gas reservoirs and clarify the gas recovery enhancement and CO2 storage mechanisms of gaseous CO2 flooding and supercritical CO2 flooding,this paper takes X bottom-water sandstone gas reservoir as an example to evaluate the suitability of CO2 flooding and propose the optimal CO2 flooding development scheme.Then,gaseous CO2 flooding and supercritical CO2 flooding are compared in terms of EOR mechanism and effect.Finally,the production and storage capacities of the optimal CO2 flooding development scheme are predicted.And the following research results are obtained.First,as for X gas reservoir,CO2 flooding is suitable,with the optimal scheme as follows.The injection and production well pattern is in the form of low injection and high production.The well shall be shut down when the CO2 concentration of the produced gas reaches 10%-20%,and injection conversion shall be performed when the formation pressure is 7.5 MPa.The pressure buildup level is 7.5 MPa.0.25 HCPV CO2 is injected at the rate of 3.5×104m3/d.The optimal scheme is expected to increase the gas recovery factor by 13.83%compared with depletion development.Second,supercritical CO2 flooding is superior to gaseous CO2 flooding in inhibiting bottom water coning and enhancing recovery factor.Third,according to the optimal CO2 flooding scheme,the total CO2 storage in this gas reservoir is 4.7×106 t,among which supercritical storage,dissolved storage and mineralized storage account for 86.05%,11.33%,and 2.62%,respectively.In conclusion,supercritical CO2 flooding can effectively improve water intrusion and recovery factor of bottom-water sandstone gas reservoirs after the gas well is watered out.These research results provide theoretical support for the efficient development of bottom-water sandstone gas reservoirs.