Abstract
In the existing research, there are few studies on the factors affecting the effect of the CO(2) huff and puff based on the law of crude oil utilization in microscopic pores. We will carry out this research on tight sandstone based on NMR. In this work, based on the law of crude oil production in microscopic pores, the relationship between various factors and huff and puff efficiency was studied, and the influence law of each factor was clarified. We characterize the dynamic changes in crude oil mobility, microporous crude oil mobilization characteristics, and huff and puff efficiency during CO(2) huff and puff under different conditions based on nuclear magnetic resonance technology (NMR). The experimental results show that the injection pressure is the main factor affecting the effect of the CO(2) huff and puff. The original pore structure characteristics of rock and soaking time also affect the huff and puff efficiency, but they are not the main influencing factors. In the process of CO(2) huff and puff, the reservoir with better macropore development will have a better huff and puff effect. For the core with medium pore and smaller pore development, the injection pressure can be increased and the soaking time can be prolonged appropriately to improve the huff and puff effect. When the injection pressure reaches the minimum miscible pressure (MMP), the utilization degree of crude oil with larger pores reaches the maximum, and the effect of increasing the injection pressure on the huff and puff efficiency is limited. With the increase in soaking time, the huff and puff efficiency increases first and then decreases, but the overall change range is small. From the perspective of the utilization degree of crude oil in different pores, increasing the soaking time has little effect on the utilization degree of crude oil in each pore. When the injection pressure is constant, the huff and puff efficiency increases with the increase of huff and puff cycles. However, after the huff and puff cycle is increased to the third cycle, it is not helpful to improve the huff and puff efficiency and the degree of crude oil utilization. Therefore, the best condition for CO(2) huff and puff is that the injection pressure reaches the minimum miscible pressure, the soaking time is 6h, and the huff and puff cycles are 3 cycles. When these conditions are reached, the utilization degree of pore crude oil in the core can reach the maximum, and the huff and puff efficiency will also reach the best. Through the experimental study of CO(2) huff and puff in tight sandstone reservoirs, the influence of various factors on the production characteristics of porous crude oil was analyzed, and the mechanism of CO(2) huff and puff to improve oil recovery was clarified. The research results provide a theoretical basis for optimizing the CO(2) huff and puff mining system and the CO(2) huff and puff mining tight sandstone reservoirs.