Acidizing fluid uniform distribution technique research and its application in Yuanba ultra deep horizontal well

The key point of carbonates horizontal wells acidizing stimulation is how to distribute the acid uniformly in the horizontal section, and the conventional solution is to adopt multistage temporary plugging technology. The regular temporary plugging agent cannot satisfy the requirements of YuanBa Changxin group marine formation due to the ultra deep buried depth and high temperature of gas reservoir. This paper developed an organic fiber temporary plugging agent, which took high viscosity fracturing fluid as transmission medium. Laboratory test figured out that the temporary plugging agent can reduce the permeability of more than 1 000 times, and have well physical plugging effect. Besides, fiber dissolution rate is very high in high temperature and acid environment, which realize zero residues after temporary blocking. Using jet drilling fluid induced by liquid nitrogen to induce flow mud in horizontal wellbore before acidification process, and then multistage plugging alternating injection technology was conducted. The stages number of temporary plugging was determined according to reservoir distribution and liner segments. Temporary plugging fluid and gelled acid were injected by following the method of “the initial low discharge capacity, temporary plugging constant flow, later large volume” to realize the acid distributing uniformly. This technology has been applied in four wells, and the temporary plugging efficiency is up to 80% with 100% stimulation efficiency. The well field results illustrate that the multistage plugging alternating injection technique was more suitable for deep carbonate horizontal well stimulation.