In order to clarify the effectiveness of CO2 injection at high temperature and high pressure in Gulong shale oil, the conversion coefficient between shale T2 value and pore throat radius is first given based on the results of shale mercury injection and nitrogen adsorption experiments. Based on the T2 spectrum characteristics of saturated shale, shale pores are divided into small pores, medium to large pores, and lamellation fractures. At the same time, a calculation method for shale oil recovery is provided. Then, the effects of huff and puff cycle, soak time, and fractures on huff and puff oil displacement effect are examined, And analyze the degree of change in core pore structure after huff and puff, and finally compare the oil displacement effects of shale oil CO2 huff and puff and CO2 displacement, and provide the optimal oil displacement method. The experimental results show that the shale oil in the middle to large pores and lamellation fractures has the highest recovery after huff and puff, while the shale oil in the small pores has the lowest recovery. Increasing the soaking time only increases the shale oil recovery by0.81%, and fracturing can increase the shale oil recovery in the small pores by 11.33%, effectively utilizing the shale oil in the small pores, and improving the recovery of shale oil in small pores is the key to improving the recovery of Gulong shale oil; Compared to CO2displacement, CO2huff and puff can increase shale oil recovery by 30.98%, and shale oil in dry rock samples can be utilized, with better huff and puff effects than displacement; The combination of displacement and huff-n-puff can increase the recovery rate by more than 12.88% compared to only using huff-n-puff, and can significantly increase the recovery of shale oil in small pores; The pore structure of the core undergoes significant changes after huff and puff, and the difference in shale gravel content is an important reason for the significant differences in pore structure changes before and after shale huff and puff. The experimental results can provide important basic parameters for the practice of the Gulong shale oil field.
Keywords Shaleoil, pore structure, CO2 displacement, CO2 huff-n-puff, nuclear magnetic resonance