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In order to achieve the multiple purposes of the highest CO2 flooding recovery and the largest CO2 storage in high water cut reservoirs， an objective function of collaborative CO2 flooding and storage optimization for high water cut reservoirs based on economic net present value （NPV） was established by considering CO2 injection cost， CO2 flooding and storage benefits. Combined with the reservoir numerical simulation method， we used simultaneous perturbation stochastic approximation （SPSA） to solve the objective function iteratively. Taking a high water cut reservoir in Shengli Oilfield as an example， the different injection timings of water transferring to CO2 were set according to the different characteristics of water cut in the reservoir at different times. The optimization of water injection and CO2 injection schemes was carried out， respectively， and the differences in production behavoir and NPV under the two injection methods were compared. The influence of gas injection timing on cumulative oil production and CO2 storage was analyzed， and the optimal gas injection timing was determined. In addition， the effects of different gas injection prices and CO2 storage subsidy schemes on their economic benefits were analyzed. The results show that the water cut should be lower than 0.97 during waterf transferring CO2 injection to make the CO2 flooding project profitable in high water cut reservoirs. The high project profit can be guaranteed as CO2 is injected earlier when the CO2 injection price is 1.2 yuan/m3， and the carbon subsidy is 0.114 yuan/m3.

CO2 flooding technology is an effective technical means to enhance the recovery of low permeability reservoirs. After CO2 comes into contact with crude oil， the asphaltene in the system is deposited in a solid form， which causes a certain blockage to the reservoir， but the dissolution improves the flow capacity of the reservoir as a whole at the same time. The damage of CO2 flooding to low permeability reservoirs under different injection methods is different. The organic scale plugging mechanism， reservoir wettability， and CO2-water solution corrosion evaluation experiments were carried out after continuous CO2 injection and CO2-water alternating injection. The variation characteristics of relative permeability curve parameters were evaluated， and the damage of different injection methods of CO2 flooding to low permeability reservoirs was quantitatively characterized. The results show that the organic scale produced by CO2 flooding would block the pore throat of the rock， but on the whole， the dissolution caused by the reaction of CO2 and chlorite is stronger， which makes the recovery of the low permeability reservoirs effectively enhanced. Moreover， the organic scale blockage caused by CO2-water alternating injection is weaker than that caused by continuous CO2 injection， and the dissolution effect is better. The permeability loss rate is lower. It could achieve a better oil displacement effect in pores with a radius of more than 0.2 μm and increase the pore space and flow channel of the rock so that the recovery of low permeability reservoir could be effectively improved.

C27H20FN3S2Sn, monoclinic, P21/n (no. 14), a = 15.631(4) Å, b = 9.865(3) Å, c = 17.256(3) Å β = 108.335(11)°, V = 2525.8(10) Å3, Z = 4, Rgt(F) = 0.0398, wRref(F2) = 0.0917, T = 298 K.