含砂压裂液流变规律实验研究

为了达到较理想的压裂效果，现场施工会泵注携带支撑剂的压裂液进入地层，研究含砂压裂液的流变规律可以为压裂液在管道和裂缝中的携砂能力预测提供更加准确的理论依据。将压裂液和支撑剂看作整体进行流变实验，研究混合流体表观黏度随剪切速率变化的规律和机理。含砂压裂液流变实验结果显示，压裂液在加入支撑剂后，在一定剪切条件下黏度低于压裂液本身黏度，另外实验还观察到含砂压裂液表观黏度随剪切强度的变化呈现先降低后升高的“V”形趋势，这是由于固液混合流体的内部结构变化与支撑剂颗粒扰动共同作用的结果。含砂压裂液特有的流变行为同样受到支撑剂浓度、粒径和液体温度等因素的影响。强剪切条件下颗粒碰撞作用明显，含砂压裂液表观黏度随浓度增大而增大，弱剪切条件下，含砂压裂液由于支撑剂造成的附加剪切破坏，表观黏度随浓度增加会先下降后升高。并且含砂压裂液黏度与颗粒粒径以及流体温度呈现反相关关系。 

Experimental Study on Rheology of Sand-content Fracturing Fluids

Fracturing fluids with proppants are commonly used in field operations for better fracturing efficiency. Study on the rheological pattern of sand-content fracturing fluids is expected to provide a better theoretical basis on which accurate prediction of the sand carrying capacity of fracturing fluids in pipe and in fracture can be made. Taking the fracturing fluid and the sands in it as a whole, the mixed fluids were studied for the patterns and mechanisms of the change of apparent viscosity with shearing rate. It was found that after mixing with proppants, the viscosity of the mixture of a fracturing fluid and the proppants under certain shearing condition is lower than the viscosity of the fracturing fluid itself, the apparent viscosity first decreases with shearing strength and then increases, showing a "V" pattern. This is the result of the synergy between the change of the internal structure of the solid-liquid mixture and the disturbance of the proppant particles. The special rheological behavior of the sand-content fracturing fluids is also influenced by the concentration and particle size of the proppant and the liquid temperature. At high shearing rate, the collision of proppant particles is frequent, and the apparent viscosity of the sand-content fracturing fluid increases with the concentration of the sand. At low shearing arte, the apparent viscosity of the sand-content fracturing fluid first decreases and then increases with the concentration of the sand because of the additional shearing action of the sand particles, and the viscosity of the sand-content fracturing fluid is reversely related with the particle size of the proppant and the temperature of the fluid.