碳酸盐岩储气库储层微粒运移对酸化的响应

Response of fines migration to acidizing in carbonate underground gas storage

地下储气库投产前,需进行酸化,清除近井地带损害;投产后注采强度高、气体流速快、多周期注采的特点易诱发微粒运移损害。选取四川盆地石炭系黄龙组某储气库碳酸盐岩岩心,开展了模拟储气库井酸化前、后多周期注采过程的岩心流动实验,利用岩心出口端产出流体的浊度,监测微粒运移程度,结合扫描电镜和X射线衍射等手段,进一步分析了多周期注采条件下酸化对碳酸盐岩储层微粒运移的影响机理。结果表明:盐酸酸化和胶凝酸酸化岩样渗透率都有不同程度的增加,其产出流体的浊度分别增加了19.3倍和21.0倍;酸化降低碳酸盐岩裂缝表面结构的稳定性,在高强度注采条件下,诱发裂缝表面的石英和黏土矿物等微粒的脱落或运移。建议钻井、完井过程中,降低储层损害,要优选酸液类型并降低酸化规模,预防微粒运移。

Before the underground gas storage is put into operation,acidizing should be carried out to clean up the pollution in the near wellbore area.After putting into production,the characteristics of high injection-production intensity,high-velocity gas flow and cyclic injection-production lead to the damage of fines migration.The carbonate core of a gas storage in Huanglong Formation of Carboniferous in Sichuan Basin is selected to carry out the core flow experiment of simulating the cyclic injection-production process before and after acidizing of gas storage well.The turbidity of the fluid produced at the outlet of the core is used to monitor the degree of the migration of fines.The influence mechanism of acidizing on the migration of the fines in carbonate reservoir under the condition of cyclic injection-production is further analyzed by means of scanning electron microscope and X-ray diffraction.The results show that:the permeability of both hydrochloric acid acidizing and gelling acid acidizing rock samples increased in different degree;the degree of the fines migration in the acidized rock with hydrochloric acid and gelling acid increased by 19.3 and 21.0 times respectively;acidizing reduces the stability of fracture surface structure of carbonate rock,and induces the exfoliation/migration of quartz and clay minerals on fracture surface under the condition of high-strength injection-production.It is suggested to reduce reservoir damage during drilling and completion,optimize the type of acid fluid and reduce the scale of acidizing,and to prevent the fines migration.