致密砂岩油藏压裂液伤害实验研究

致密砂岩油藏孔喉半径细小、连通性差,水力压裂过程中由于压裂液滤失、返排不彻底等因素极易造成储层伤害,有必要针对常用压裂液体系对储层基质和支撑裂缝导流能力的伤害进行评价。利用压裂液注入实验和导能能力测试仪测试了滑溜水压裂液、线性胶压裂液和交联胍胶压裂液的储层基质伤害、滤饼伤害和支撑裂缝导流能力伤害,结合核磁共振技术分析了压裂液滤失的孔径范围,揭示了三种压裂液对储层和支撑裂缝的伤害机理。三种压裂液对储层基质伤害和滤饼伤害与滤失系数有关,滤失系数越大,基质伤害越大,滤饼伤害越小。储层的滤饼伤害要大于基质伤害。针对致密砂岩储层,压裂液对储层基质的伤害主要是对储层中孔和大孔的伤害。三种压裂液对支撑裂缝导流能力的伤害大小和破胶液的残渣含量有关,残渣含量越高,对支撑裂缝导流能力的伤害也就越大。闭合压力越高,支撑裂缝导流能力伤害率也越高。对于致密砂岩油藏,减小滤饼形成和残渣的滞留是降低压裂液伤害的主要途径。

Experimental study on fracturing fluid damage in tight sandstone reservoir

Due to the small pore throat radius and poor connectivity of tight sandstone reservoirs, it is easy to cause reservoir damage due to fracturing fluid filtration and incomplete flowback during hydraulic fracturing. Therefore, it is necessary to evaluate the damage of commonly used fracturing fluids on reservoir matrix and propping fracture conductivity.SThrough fracturing fluid injection and flow conductivity measuring instrument, the reservoir matrix damage, filter cake damage and propped fracture conductivity damage of slickwater fracturing fluid, linear gel fracturing fluid and cross-linked guar fracturing fluid were measured. The pore size range of three fracturing fluids filtration were analyzed with nuclear magnetic resonance technology. The damage mechanism of three fracturing fluids to reservoir and propped fracture were revealed. The reservoir matrix damage and filter cake damage of three fracturing fluids is related to the filtration coefficient. The greater the filtration coefficient, the greater the matrix damage and the smaller the filter cake damage. The damage of filter cake is greater than that of matrix.SFor tight sandstone reservoir, the damage of fracturing fluid to reservoir matrix is mainly the damage to middle and large pores.SThe damage of the three fracturing fluids to the conductivity of the propped fracture is related to the residue content of the glue breaking fluid, and the higher the residue content, the greater the damage to the conductivity of the propped fracture.SThe higher the closure pressure is, the higher the damage rate of propped fracture conductivity is.SFor tight sandstone reservoir, reducing filter cake formation and residue retention is the main way to reduce fracturing fluid damage.