Distribution of alternating injection fluid in rough fractures

Alternate injection acid pressure technology is an effective means to modify deep carbonate reservoirs, when the injected fluid flows inside the rough seam, the phenomenon of fingering occurs, which can make the acid fluid unevenly with the distribution inside the fracture and improve the effect of non-uniform etching. Based on the unidirectional flow finite element method, a multinomial flow VOF model is used to study the fluid distribution law in the slit with different roughness, number of injection stages and injection flow rate. The results show that: with the increase of roughness, the length of the front edge gradually increases and the average flow rate gradually decreases; with the increase of the number of injection stages, the length of the front edge gradually increases and the average flow rate gradually increases; with the increase of the injection flow rate, the furthest distance of the slit length and the length of the front edge gradually increase. Therefore, for acid fracturing of carbonate reservoirs, we can consider optimising the injection displacement and the number of injection stages to improve the effective distance of acid, so as to optimise the effect of acid fracturing. [Received: March 1, 2024; Accepted: April 19, 2024]