Research and evaluation of fracturing fluid compounded by oil-reservoir water

A formulation of hydroxypropyl guanidine gum fracturing fluid system compounded by oil-reservoir water is developed,in which oil-reservoir water is used based liquid,hydroxypropyl guar gum as thickener,organic boron as crosslinking agent,and biological enzyme as gel-breaking agent.The fracturing fluid system can suit for different formation temperature.The experiments indicated that the optimal mass fraction of hydroxypropyl guanidine gum is 0.4%,the mass fraction of organic boron is 0.5%,and the dosage of biological enzyme can decrease with the rising of formation temperature,when the formation temperature is 25 ℃,its mass concentration is 100 mg/L,and when the formation temperature is up to 40 ℃,its mass concentration is only 50 mg/L.at the formation of temperature of 40 ℃,the retained viscosity of the fracturing fluid system after shearing 30 min at the shearing rate of 170 s-1 is greater than 50 mPa·s.The gel-broken fracturing fluid has a viscosity of less than 5 mPa·s(measured with capillary viscometer),the residue content in gel-broken fluid is 450 mg/L,and the average particle size of the residue is 2.8 μm.The damage of the fracturing liquid to the permeability of core matrix is 22.6%.