元坝海相超深水平井均匀布酸技术研究及应用

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

碳酸盐岩水平井酸化改造的关键问题是水平段如何均匀布酸,常用方法是采用多级暂堵工艺。但元坝海相长兴组气藏由于埋藏超深、温度高,常规的暂堵剂无法满足施工要求。为此,研制了新型有机纤维暂堵剂,输送介质采用高黏压裂液,室内实验测试可降低岩心渗透率1 000倍以上,具有较好的物理暂堵效果,同时纤维在高温酸液中溶解率高,实现了暂堵后零残留。酸化前利用液氮诱喷钻井液净化水平井井筒,酸化工艺采用多级暂堵交替注入,依据水平段储层分布及衬管段确定暂堵级数,暂堵液与胶凝酸以"初期低排量、暂堵定排量、后期大排量"的方式交替注入,实现水平段的均匀布酸。该工艺在现场实施4口井,暂堵有效率近80%,增产有效率100%,表明对深层碳酸盐岩水平井改造有较好的针对性。

The key point of carbonates horizontal wells acidizing stimulation is how to distribute the acid uniformly in the horizontal sec- tion, and the conventional solution is to adopt multistage temporary plugging technology. The regular temporary plugging agent cannot satisfy the requirements ofYuanBa 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. Be- sides, 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, tem- porary 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.