Preparation And Performance Evaluation Of Organic Zirconium Crosslinker For Fracturing

Compared with the traditional water-based fracturing fluid viscosifier guanidine gum, the price of synthetic polymer polyacrylamide is relatively low. Organic metal crosslinker has delayed crosslinking effect on polyacrylamide. The fracturing fluid made by polyacrylamide has better shear-resistance, heat-resistance and viscoelasticity. Therefore, the fracturing fluid crosslinked by synthetic polymer HPAM and organic metal crosslinker will become one of hot topics in the study of water-based fracturing fluid.Oxygen zirconium chloride, citric acid, acetic acid and triethanolamine as raw material, were used to synthesize citric acid organic zirconium crosslinker and acetic acid organic zirconium crosslinker. Polymer gel cross-linked by the organic zirconium crosslinker and polymer KY-5S solution has different viscosity and delayed crosslinking time, compareing these performance, acetic acid organic zirconium crosslinker was eventually choosed to prepare fracturing fluid. Acetic acid organic zirconium crosslinker and fracturing fluid additives were added into the polymer KY-5S solution to prepare fracturing fluid. The shear-resistance and heat-resistance, viscoelasticity, static filtration performance, gel breaking performance, carrier performance and core damage of fracturing fluid were evaluated.By discussing crosslinking time, viscosity and cross-linking phenomena of polymer gel, the influence factors on synthesis of the organic zirconium crosslinker were researched. The optimum synthesis condition of organic zirconium crosslinker prepared by citric acid and triethanolamine as follows:the mass concentration of oxygen zirconium chloride was 5wt%, the mass concentration of citric acid and triethanolamine was 2wt% and 5wt%, respectively, the reaction temperature was 80?, the value of pH was 7, the reaction time was 5h. The optimum synthesis condition of organic zirconium crosslinker prepared by acetic acid and triethanolamine as follows: the mass concentration of oxygen zirconium chloride was 5wt%, the mass concentration of acetic acid and triethanolamine was 2wt% and 3wt%, respectively, the reaction temperature was 75?, the value of pH was 7, the reaction time was 5h.Polymer KY-5S as thickener, citric acid organic zirconium and organic zirconium acetate as crosslinker, the polymer gel system performance was studied, organic zirconium acetate crosslinker had better crosslinking time, about 10min. Finally concentration of polymer KY-5S solution was 0.3wt%, poly-cross ratio of acetic acid organic zirconium crosslinker was 60, and fracturing fluid additives were used to prepare fracturing fluid, and its performance was evaluated.The performance evaluation results of fracturing fluid show that when the shear rate was 170s-1, the temperature was 140? for 2h, the viscosity of fracturing fluid remains in more than 100mPa·s. When the temperature was 20?, the shear stress was 0.1 Pa, frequency f changed from 10 to 0.1 Hz, the minimum elastic modulus of fracturing fluid was 11.6Pa, the minimum viscous modulus was 8.54Pa. When the dosage of breaker was 0.01wt%, the gel-breaking time was 3h, the viscosity of gel-breaking liquid was 4.05mPa·s, the damage rate of gel-breaking liquid on the core permeability was about 13%. When the shear rate changed from 0 to 170s-1, the viscosity of fracturing fluid remains in more than 200mPa·s. The above performance was consistent with the requirement of "Oil and gas industry standards SY/T 6367-2008 fracturing fluid general technical conditions".