青西油田X井堵塞分析评价及解堵方案

Blockage Analysis and Blockage Removal Scheme of Well X in Qingxi Oilfield

针对玉门青西油田X井储层伤害的主要原因,实验评价了使用现场的压井液、压裂液与储层的配伍性及伤害程度。根据实验结果得出:对于X井,高密度的氯化钙盐水进入地层引起地层的强力敏感,导致渗透率下降,同时大量的滤失液有可能造成水堵和乳化堵。通过表面活性剂和醇将油溶湿表面转化为水溶湿表面,解除水堵;压裂液在盐酸和高密度盐水的作用下,溶解度大幅度降低,固体胍胶和残渣吸附在微裂缝的壁面上,造成了压裂液固体堵塞;针对盐酸溶液与压裂液发生反应生成难溶解絮团所致的储层堵塞,可采用双氧水进行降解,解除残渣堵塞;十水四硼酸钠对5%双氧水有防腐作用,但是在高温时可与双氧水发生反应,生成白色沉淀物,不宜作缓蚀剂。硝酸钠与硝酸钾对5%双氧水有一定的防腐作用,且钢试片的腐蚀速率也比较小。以青西油田X井为例,开展了实验评价,并制定了可行的解堵方案。

Aiming at the main causes of reservoir damage in Well X of Qingxi Oilfield, Yumen, the compatibility between killing fluid,fracturing fluid used in field and reservoir and their damage degree to reservoir are evaluated experimentally. The experimental results show that for well X, high density calcium chloride brine enters the formation, resulting in a decline in permeability, while a large number of filtration liquid may cause the water plugging and emulsification plugging of reservoir. Oil-soluble wet surface is transformed into water-soluble wet surface by surfactants and alcohols to relieve water plugging. Under the action of hydrochloric acid and high density brine, the solubility of fracturing fluid decreases dramatically, and solid guar gum and residue are adsorbed on the wall of micro-cracks,resulting in solid plugging of fracturing fluid. The reservoir blockage caused by the reaction of hydrochloric acid solution and fracturing fluid to form insoluble flocs can be removed by the degradation of hydrogen peroxide. Sodium tetraborate decahydrate has antiseptic effect on 5% hydrogen peroxide, but it can react with hydrogen peroxide to form white precipitate at high temperature, so it is not suitable as an inhibitor. Sodium nitrate and potassium nitrate have a certain anti-corrosion effect on 5% hydrogen peroxide, and the corrosion rate of steel specimens is relatively small. They can be used as inhibitors. Feasible plugging removal schemes are worked out.