瓜胶压裂液携砂微观机理研究

Microscopic Mechanism of Proppant Carrying Capacity of Fracturing Fluid

何春明 才 博 卢拥军 段贵府 刘 哲

HE Chun-Ming Cai Bo LUYong-Jun DUAN Gui-Fu LIU Zhe

本研究通过对瓜胶压裂液进行静态支撑剂沉降实验、动态黏弹性测试、屈服应力测试、分子结构表征，研究了瓜胶压裂液的宏观性能、分子结构与压裂液携砂性能间的关系。支撑剂沉降实验表明，压裂液黏度的变化与支撑剂沉降速率呈非线性关系，用黏度指标很难准确表征压裂液的携砂性能。动态黏弹性测试表明，压裂液损耗模量的增加有利于降低支撑剂沉降速率，而储能模量的大幅度提高赋予流体弹性特征，这才是支撑剂能够长时间保持均匀悬浮状态的根本原因。压裂液微观结构分析表明，压裂液基液具有杂乱、松散、多孔洞的网络堆砌结构，而交联压裂液具有均匀、紧密的整体堆砌结构，该结构赋予交联压裂液弹性，使其携砂能力发生本质变化。图8表1参15

The relationship between macroscopic properties of fracturing fluid, molecular microstructure and fracturing fluid proppant carrying capacity was studied through static state proppant settlement experiment, dynamic viscoelastic test, yield stress test, scanning electronic microscope observation. Proppant settlement experiments showed that?a?nonlinear?relationship?existed?between the change of viscosity of fracturing fluid and proppant settling rate, which indicated that viscosity index could not characterize the carrying capacity of fracturing fluid accurately. Dynamic viscoelastic tests showed that the increase of loss modulus was favorable of reducing the rate of proppant settling, while a significant increase of storage modulus which endowed the fluid elasticity maybe the main reason for proppant keeping suspension for a long time in crosslinked fracturing fluid. Fracturing fluid microstructure analysis showed that the fracturing base fluid possessed a disorder, loose, plurilocellate, and mesh-stacked structure, while the crosslinked fracturing fluid possessed a well-distributed, close and the whole-stacked structure, endowing the elasticity of crosslinked fracturing fluid and causing a essence change of fracturing fluid proppant carrying capacity.