惠州26-6区块低渗储层保护钻井液技术研究

RESEARCH ON DRILLING FLUID TECHNOLOGY FOR PROTECTING LOW PERMEABILITY RESERVOIR IN BLOCK 26-6 OF HUIZHOU

针对惠州26-6区块古近系低渗储层保护技术难题,采用储层岩心矿物组成、微观结构、理化性能及敏感性评价实验,探讨了其储层损害机理,提出了相应的储层保护钻井液技术对策,构建了适合惠州26-6区块的储层保护钻井液体系。结果表明:储层岩石矿物组成以石英为主,黏土矿物含量较低,储层岩心为强速敏损害,临界流速0.1 cm^(3)/min;弱水敏损害,最大水敏损害率为21.29%,临界矿化度为120 g/L;中等偏弱碱敏损害,临界pH值为9,无酸敏损害。提高钻井液封堵性以减小滤液侵入、优选高效防水锁剂是保护储层的主要技术措施。所构建的储层保护钻井液热滚前后黏度、切力适中,且滤失性及润滑性能较好,单一钻井液静态和动态污染后岩心渗透率恢复值分别为84.06%和85.39%,钻井液具有较好的储层保护性能。

Aiming at the technical challenges of protecting low permeability reservoirs in the Paleocene of 26-6 block in Huizhou,the mechanism of reservoir damage was explored through experiments on the mineral composition,microstructure,physicochemical properties and,sensitivity evaluation of the reservoir core.Corresponding drilling fluids technical strategies for reservoir protection were proposed,and a reservoir protection drilling fluid system suitable for Huizhou 26-6 block was constructed.The results indicate that the mineral composition of the reservoir rock is dominated by quartz,with low clay mineral content.The reservoir core exhibits strong velocity sensitive damage,with a critical flow rate of 0.1 cm^(3)/min;Weak water sensitive damage,with a maximum water sensitive damage rate of 21.29%and a critical mineralization degree of 120 mg/L;Moderate to weak alkali sensitive damage,with a critical pH value of 9,and no acid sensitive damage.Improving the plugging performance of drilling fluid to reduce filtrate invasion and selecting efficient waterproof locking agents are the main technical measures to protect the reservoirs.The constructed reservoir protection drilling fluid has moderate viscosity and shear force before and after hot rolling,and good filtration and lubrication performance.The recovery values of core permeability after static and dynamic contamination of a single drilling fluid are 84.06%and 85.39%,respectively,indicating that the drilling fluid has good reservoir protection performance.