Low permeability reservoirs are widely distributed in Subei（northern Jiangsu province） Basin. There are some problems such as insufficient natural energy and fragmented structures

which make it difficult to form an effective injection-production well pattern. Therefore

the effect of water injection is poor. The CO

2

huff and puff technology can effectively solve these problems with less investment

simple process and rapid results. Choosing the proper wells to execute is the key to the success of this technology. Based on the comparative analysis of CO

2

huff and puff in low permeability reservoirs in Subei Basin in recent years

combined with indoor physical simulation experiments and numerical simulation results

it

is considered that closed reservoirs with medium-deep burial depth and fracture development are more suitable for CO

2

huff and puff. Fractures have a greater impact on huff and puff effect. There is an appropriate interval for formation pressure

not the bigger the better

whether miscibility can be achieved or not. It has no decisive effect on the throughput effect. Oil wells with high initial production and water cut of 30 %~70 % in lower structure are more conducive to huff and puff

and the huff and puff effect of horizontal wells is better than that of vertical wells.