不同pH值下交联胍胶压裂液的性能研究

碱性硼交联压裂液是目前油田广泛采用的压裂液体系,但是随着低渗透油气藏开采的增加,最大程度地降低压裂液对地层的伤害显得十分重要,酸性压裂液体系具有有效抑制粘土膨胀的特性,且能够适用于CO2增能体系或泡沫体系,因而也受到广泛关注。本文将酸、碱性交联胍胶压裂液体系的耐温抗剪切性能、破胶性能、残渣含量、滤失性能、粘弹性能和粘土稳定性能进行对比评价,酸性体系在170s-1下剪切120min后,冻胶粘度保持率在50%左右,而碱性体系粘度保持率在70%左右,碱性体系的抗剪切性能更好;酸性体系耐温能力大于140℃,而碱性体系耐温能力只有120℃左右,酸性体系的耐温性能更好;酸性体系静态滤失系数小于6.0×10-4m/min1/2,碱性体系滤失系数大于6.5×10-4m/min1/2,酸性体系的滤失性能更好;酸性体系的残渣含量小于350mg/L,碱性体系在400mg/L左右,酸性体系的残渣更少,且酸性体系的粘土稳定性能更好,对地层的伤害更小,因此酸性体系更加适用于埋藏较深的低渗透地层压裂。

Properties Research on Guar-Crosslinked Fracturing at Different pH Value

The alkaline borate crosslinking fracturing fluid has been widely used in the oilfield.But with the development of low-permeability reservoirs,it is more and more important to reduce the formation damage from fracturing fluid.The acid fracturing fluids for its good capacity of inhibit clay swelling and application in CO2 energization system or foam system has aroused extensive concerns.This paper evaluates the performance of guar-crosslinked fracturing fluids in the alkaline or acid condition,including their temperature stability,shearing resistance,gel breaking capability,residue content,filtration property,viscoelastic property and clay swelling property.The results show that gel viscosity maintains about 50% at 170s-1 continuous shearing for 120min under acid condition,but the viscosity can maintain about 70% under alkaline condition.The alkaline system has better shearing resistance property.As to the temperature stability,the acid fracturing is better for above 140℃ than the alkaline system for only about 120℃.The coefficient of static filtrate loss is below 6.0×10-4m/min1/2 to the acid system and is above 6.5×10-4m/min1/2 to the alkaline system.The acid system’s residue content is below 350mg/L,while the alkaline system is about 400mg/L.The acid fracturing fluid has better performance of inhibit clay swelling and less formation damage,so it is more effective for deep,low-permeability fracturing well.