| As an important part of unconventional oil and gas exploration and development,shale oil is an indispensable part of unconventional oil and gas in China.At present,shale oil is mainly developed elastically by large-scale fracturing,and the initial recovery rate is low.Gas huff-n-puff injection is an important method of recovery.Gas huff-n-puff injection is mainly established after volume fracturing of the reservoir.However,due to the existence of artificial fractures and natural fractures,field tests show that gas channeling is serious in adjacent wells during gas huff-n-puff injection.With the continuous expansion of the gas injection volume,the effect of enhanced oil recovery has not been improved continuously.Therefore,it is urgent to deal with the gas channeling problem in the existing gas injection huff and puff process,so as to avoid the waste of channeling of injected gas,and further improve the recovery factor.Based on the experiments conducted on fractured cores obtained from the Permian Lucaogou Formation shale reservoir in Jimsar Sag,Junggar Basin,Xinjiang,the gas channeling law of fractured cores during gas huff-n-puff injection was explored from the perspectives of different injection flow rates and different injection pressures.The screening experiment of foaming agents is carried,the foaming ability and foam stabilization ability of each foaming agent are evaluated.The foaming agent with the best comprehensive foam performance is selected,and the plugging performance of fractured cores after foaming is clarified,in order to explore the application potential of using foam to prevent gas channeling in the process of gas huff-n-puff injection in shale cores to improve oil recovery.The research shows that the injection of foam can effectively reduce gas mobility,increase the volume of huff-n-puff,and inhibit the gas channeling in the fractures.The AOS foaming agent with a mass fraction of 0.4% was screened out of the four foaming agents with the best stability;when the gas-liquid ratio was 1:1,the pressure difference of the foam generated after the gas-liquid co-injection increased to 6.67 MPa,The gas breakthrough time increased by 13.72times;on the basis of foam plugging,5 rounds of huff and puff could increase the total recovery factor by 11.43%. |
