致密砂岩气藏纳米封堵型低伤害压裂液研究

针对常规胍胶压裂液对致密砂岩气藏伤害大的难题,通过分子结构设计和正交实验,研制了一种纳米封堵型低伤害压裂液,在致密气藏压裂施工中能封堵部分压裂液于储层基质外,施工后液体能快速返排,从而有效降低稠化剂分子的滞留吸附与液相伤害。该压裂液在35～140℃、170 s^-1条件下剪切120 min,终黏度大于80 mPa.s:能彻底破胶,残渣含量低,破胶液表面张力为25.91 mN/m,对致密砂岩岩芯伤害率低于15%,封堵性能及其他综合性能满足现场施工要求。该压裂液在ZJ125井现场应用,效果良好,施工后液体返排快,返排率高达75.94%,比邻井提高47%,天然气产量1.647 5×10⁴ m³/d,是邻井JS316HF井产量的两倍,显示了其在致密砂岩气藏中良好的低滞留特性。

Nano-plugging Low Damage Fracturing Fluid for Tight Sandstone Gas Reservoir

To solve the problem that conventional guar gum fracturing fluid is harmful to tight sandstone gas reservoir, a kind of low damage nano-sealing fracturing fluid was developed by means of molecular structure design and orthogonal experiment. During the fracturing of tight gas reservoir, fracturing fluid can be blocked out of the reservoir matrix, and the liquid can be drained back quickly after the fracturing, so as to effectively reduce the retention and adsorption of thickener molecules and the damage of liquid phase. The fracturing fluid is sheared for 120 min at 35$sim$140℃ and 170 s$^{-1}$, the final viscosity is over 80 mPa$cdot$s, the gel can be broken thoroughly, the residue content is low, the surface tension of the GEL breaker is 25.91 mN/m, the damage rate to the tight sandstone core is less than 15%, and plugging performance and other comprehensive performance meet the requirements of field construction. Using this fracturing fluid in ZJ125 Well, the fluid performance is good, and the fluid flowing back is quick after the operation, the flowing back rate being as high as 75.94%, 47% higher than adjacent well; the natural gas output is 1.647 5 $times$10$^4$ m$^3$/d, 2 times of adjacent Well JS316HF, showing that the gas reservoir has a good low retention property in tight sandstone gas reservoirs.