In the study, hydroxypropyl guar gum (HPG) gel is prepared by using Nano-ZrO 2 particles as the cross-linking agent. The Nan-ZrO 2 particles are prepared by using oil-water interface method. The physical properties such as morphology, particle size, and crystal structure of the Nano-ZrO 2 particles are analyzed by SEM, particle size analyzer, FT-IR, and XRD, respectively. The results show that the Nano-ZrO 2 particles are spherical particles with a little agglomeration; these spherical particles have a tetragonal structure and higher crystallinity, and the mean diameter of the first-level grain is 24 nm. The rheological properties including shear stress, complex modulus, elasticity modulus (G′), and viscosity modulus (G′′) of the Nano-ZrO 2 cross-linked HPG gel are investigated. The results show that the Nano-ZrO 2 cross-linked HPG gel is a pseudo-plastic non-Newtonian fluid with higher elastic modulus (G′ > G′′) and lower tanδ (tanδ < 1, the ratio of viscous and elastic modulus), which indicate that the Nano-ZrO 2 cross-linked HPG gel may have potential application in fracturing.
KEYWORDSHPG gel, Nan-ZrO 2 particles, rheological properties
| INTRODUCTIONHydroxypropyl guar gum (HPG) is not only the abundant green natural polymer in the world; it is also a kind of low-cost, renewable, environmentally friendly, and non-toxic material.1 In addition, HPG also has great mechanical property and good swelling capacity. Because of these advantages, HPG has aroused great concern in many applications, especially in oil and gas exploitation industry. However, in the process of fracturing flow-back, it is well known that these cross-linking ions still remain in the fracturing fluid, which has a serious impact on the reuse of fracturing fluid. As people pay more attention to the environment increasingly, the reuse of fracturing fluid is becoming a serious and urgent issue in oil field, and one of the most critical issues is to eliminate the influence of the remaining cross-linking agent. While the Nano-ZrO 2 cross-linked HPG gel is broken, nanoparticles can easily be eliminated by some simple means such as centrifugal separation and filtration, and the fracturing fluid can be used to reconfigure the fracturing gel, which not only protects the environment, but also improves the utilization efficiency of water resources.However, there are just few researches about physical nanoparticles used as a cross-linking agent in fracturing fluid.Some significant properties of zirconia, including the high temperature resistance, insulation, and shade resistance, have been widely studied. 5 However, the performance of cross-linking with HPG has not gained enough attention. Therefore, in this perspective, the objective of this paper is to synthetize a kind of zirconia with good dispersion in a convenient, cheap, and safe method and study on the crosslinking properties of Nano zirconia with HPG. For this purpose, the properties of the Nano-ZrO 2 are researched by SEM, XRD, FTIR, and particle size analysis. The viscoelastic property of the N...