克拉苏气田超致密砂岩气储层水锁损害

超致密砂岩微米、纳米级孔喉发育且连通性差,气层具有毛细管压力高、黏土矿物含量高、含水饱和度低等特征,水锁是这类气藏重要的损害方式。现有的水锁损害评价标准存在未建立初始含水饱和度、地层水盐析、水敏伤害与水锁伤害叠加耦合、渗透率测试具有系统误差、评价不全面等问题,文中以克拉苏气田克深9井区K1bs组超致密砂岩为研究对象,利用核磁成像技术实时监测岩样毛细管自吸过程,运用高温钝化、高速离心、恒压驱替、核磁共振等手段建立该类气藏水锁损害评价方法,并据此进行室内实验,对比评价蒸馏水、质量分数8%的KCl溶液与破胶压裂液等流体对超致密砂岩气层基质的损害程度。结果表明,气层孔喉半径越小,流体黏度越大、矿化度越高,初始含水饱和度与束缚水饱和度差异越大,气层水锁损害越强。

Water blocking damage of hyper-tight sandstone gas reservoir in Kelasu gas field

Because of the poor connectivity of the hyper-tight sandstone nano-pores,the gas layer has the characteristics of high capillary pressure,high clay mineral content and low water saturation,and the water blocking is an important form of damage to this type of gas reservoir.The existing water blocking damage evaluation standard has the problems,such as the initial water saturation,formation water salting-out,water sensitive damage and water blocking damage superposition coupling,permeability test system error,incomprehensive evaluation and other issues.In this study,the Klbs Formation of hyper-tight sandstone in Keshen-9 well area was used as the research object,and the spontaneous imbibition process of the capillary was monitored by MRI technique;the damage of water blocking in the gas reservoir was evaluated by means of high temperature passivation,high speed centrifugation,constant pressure displacement and nuclear magnetic resonance.The indoor experiment was carried out to evaluate the damage degree of distilled water,8％ mass fraction potassium chloride solution and fractured fracturing fluid to the hyper-tight matrix.The results show the smaller the pore throat radius,the greater the viscosity of the fluid,the higher the degree of mineralization,the greater the difference between the initial water saturation and the irreducible water saturation,the stronger the water blocking damage.