| More than 35%of the proven natural gas resources in the Tarim Basin are condensate gas reservoirs,accounting for 40%of the country’s total proven condensate gas reserves.It is an extremely important strategic oil and gas resource base in my country.The oil and gas reservoirs in the Tarim Basin are mainly carbonate fracture-cavity reservoirs.Compared with homogeneous sandstone condensate gas reservoirs,this type of reservoir space is mainly composed of fractures,pores and large caves,and has a type of storage space.With the characteristics of diversity,deep burial,strong reservoir heterogeneity,and poor inter-well connectivity,gas reservoir development conditions are harsh and difficult.Whether the fracture-cavity structure of the carbonate reservoir and the filling medium inside the pores will affect the depletion of condensate oil and gas.How to formulate a reasonable gas injection method based on the actual characteristics of block gas reservoirs and improve the recovery rate of condensate oil requires in-depth research.In this paper,based on the PVT test report of condensate gas well flow provided by the oil field,the condensate gas fluid of ZG43 well was prepared in the laboratory,and the phase state test experiment was carried out on the PVT phase state analyzer,and the phase state characteristics of the condensate gas were obtained.Then,the carbonate rock outcrop is used to make fracture-cavity pore media model,and the influence of fracture-cavity pore media on the dew point pressure and the recovery rate of condensate oil and gas during the depletion of condensate gas is studied.Then,based on the characteristics of isolated caves in the target oil and gas reservoir as the main body,the wells are disconnected,and the storage space is affected by the fault-controlled karst structure,and the beads are distributed beside the fault,a single well gas injection huff and puff is selected as the method to improve the recovery rate.Studied the effect of different gas injection factors on the improvement of condensate oil recovery,and provided experimental basis and theoretical support for the gas injection development of the Tarim condensate gas reservoir.Depletion experiments in fracture-cavity pores have found that the existence of fracture-cavity pore media will affect the depletion mining process of condensate gas:（1）The fracture-cavity pores formed by carbonate rocks will increase the dew point pressure of the condensate gas system.High,the pressure increase of the dew point is greater when the fractures and pores are filled than the pores without filling.（2）Carbonate rock pores and filling media will aggravate the phenomenon of retrocondensation and hinder the production of condensate oil.Pore filling is less produced than unfilled condensate oil.Gas injection huff and puff experiments show that:（1）Different injected gas has different extraction and anti-evaporation capabilities for the condensate in the pores.CO2 has the strongest anti-evaporation ability,followed by CH4,and N2 is the weakest,but considering the construction of gas source stations.In addition to the cost of denitrification and CO2 removal of produced gas,CH4 or dry gas with CH4 as the main component is the best choice for injected gas;（2）The experimental results of gas injection timing show that gas injection can effectively prevent the reaction from depletion to above the dew point pressure.The occurrence of condensate phenomenon keeps the produced gas-oil ratio low and maintains the productivity of the production well;（3）The gas injection rate experiment results show that increasing the gas injection rate increases the reservoir pressure and can increase the degree of condensate oil recovery. |
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