英南2井预防水锁水敏的钻井液配方室内试验研究

在英南2井储层地质特征、储层伤害特征及程度研究的基础上,针对储层具有严重的水锁效应和水敏效应,确定使用低密度钾基聚磺钻井液体系,设计了防止水锁效应和水敏效应的钻井液配方,并对其进行了室内静态伤害实验.实验结果表明,储层在束缚水含水饱和度为63%时和原始含水饱和度为43%时,岩心渗透率的恢复率均大于86%.因此,钾基聚磺钻井液能较好地控制储层孔隙喉道中的黏土矿物膨胀,相对增大了孔隙和喉道大小,减轻了储层的水锁与水敏伤害程度,提高了气相渗透率.所确定的钻井液体系与配方较好地满足了英南2井钻井工程的现场要求.

Experimental study on drilling fluid formulation for preventing the water-lock & water-sensitivity of the gas reservoir in Yingnan-2 well

The reservoir of Yingnan-2 well is seriously damaged by water lock and water sensitivity during drilling and completing. Based on the study of the geological characteristics, damage characteristics and damage degree of the gas reservoir, a low-density potassium base sulphonated polymer drilling fluid formulation is designed for preventing the water lock and water sensitivity damage. The static performance of the cores damaged by the drilling fluid is measured in laboratory. The experimental results show that the permeability restoration rates of the cores are all higher than 86 % when the irreducible water saturation of the cores is 63 % and when the original water saturation of the cores is 43 %. So the drilling fluid system can well control the expansion of the clay mineral in the pore throat of the gas reservoir, which relatively increases the sizes of pore and throat, reduces the degree of the water lock damage, and enhances gas phase permeability of the reservoir. The drilling fluid system well meets the requirement of the drilling engineering of Yingnan-2 well.