连续流动碱性流体与碳酸盐岩作用的碱敏损害实验研究

碳酸盐岩储层粘土矿物含量低，普遍认为其储层碱敏性弱。然而在富含H2S和CO2的碳酸盐岩储层中，在酸性介质条件下长期存在于碳酸盐岩储层中的粘土矿物，所接触的钻井完井液pH值一般高于11，碱敏损害研究的意义尤为重要。为了模拟高pH钻井完井液对储层造成的损害，文中以四川盆地中部雷口坡组和嘉陵江组碳酸盐岩气层为研究对象，实验评价了连续流动下碱性流体与碳酸盐岩储层作用的损害行为，并与常规碱敏实验对比。实验表明，常规碱敏实验随着流体pH值的升高，损害率61％-85％，连续流动实验损害率91％-97％，比常规碱敏实验损害率增加12％-30％。连续流动加快了反应速率和反应进程，有利于碱液与自云石和粘土矿物的反应进行, 生成新矿物相，从而降低储层渗透率。对于富含H2S和CO2的碳酸盐岩气藏，采用近平衡钻井技术、快速钻井技术与屏蔽暂堵技术结合是保护储层的重要途径。

Experimental Research on Alkali Sensitivity Damage from Interactions Between Continuously Flowing Alkaline Liquids and Carbonate Rocks

The content of clay mineral in carbonate rock reservoirs is usually lower than that in clastics, so it is generally thought that alkaline sensitivity of carbonate reservoirs is weak. Considered the fact that most carbonate reservoirs are enriched in H2S and CO2, and clay minerals consist in carbonate reservoirs for a geological time under acid environments, the pH of drilling-in fluids contacted with reservoir is generally higher than 11, so the studies on alkali sensitivity damage is particular importance. For simulating the reservoir damage of drill-in fluids with high pH, rock samples are selected from carbonate gas reservoirs of T2l and T1j formations in Sichuan Basin, and experiments are conducted under continuous flowing alkali fluids by compared with regular alkali sensitivity experiment program. The experimental results indicate that the alkaline damage degree with regular experiment program during rising of fluid pH ranges 61%-85%, and that with continuous flowing alkali fluid experiment is up to 91%-97%. The increment of alkaline damage degree is 12%-30%, because continuous flowing of alkaline fluids can accelerate reaction rates and increase reaction progress in contacts of alkaline fluids with dolomite and clay minerals. Under continuous flowing condition, reactions can be sustained, and new minerals can be formed continuously, which resulted in decrease of reservoir permeability. For carbonate reservoirs rich in H2S and CO2, using near balanced drilling technology, fast drilling with temporary shielding plugging technology are recommended to control formation damage from drill-in fluids with high pH.