title: Effect of pH on the rheological properties of borate crosslinked hydroxypropyl guar gum hydrogel and hydroxypropyl guar gum.
abstract: pH is an important factor affecting the performance of polymer fluid. The rheological properties of hydroxypropyl guar gum (HPG) base fluid and the structural strength, rheological properties, viscoelastic properties and thixotropy properties of HPG gel depend largely on the pH values. For the base fluid, an apparent viscosity-increasing effect was observed over the pH range from 7 to 11, and the apparent viscosity gradually decreased at pH 11.5-14, exhibiting electrostatic repulsion behavior and steric effects. For the HPG gel, at pH 7-12.5, the gel possessed higher apparent viscosity, higher elastic modulus (G'), lower tanδ (the ratio of the viscous modulus to the elastic modulus) and an "8"-shaped hysteresis loop, indicating stronger gel structure strength and the elastic dominant property. At pH 13-13.5, the gel samples exhibited the transition from a pseudoplastic fluid to a Newtonian fluid, and their viscosity, elastic modulus decreased but tanδ increased with the increase in pH values, exhibiting gradually weakened elastic properties. When the pH was 14, the gel mainly exhibited viscous characteristics.
authors.affiliation: State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation, Southwest Petroleum University, Xindu, Chengdu, Sichuan 610500, PR China. Electronic address: wangshb07@163.com.
authors.forename: Shibin
authors.initials: S
authors.lastname: Wang
authors.affiliation: State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation, Southwest Petroleum University, Xindu, Chengdu, Sichuan 610500, PR China.
authors.forename: Hongbiao
authors.initials: H
authors.lastname: Tang
authors.affiliation: State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation, Southwest Petroleum University, Xindu, Chengdu, Sichuan 610500, PR China.
authors.forename: Jianchun
authors.initials: J
authors.lastname: Guo
authors.affiliation: State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation, Southwest Petroleum University, Xindu, Chengdu, Sichuan 610500, PR China.
authors.forename: Kunjie
authors.initials: K
authors.lastname: Wang
mesh_terms: D001881:Borates / Q000737:chemistry*; D020136:Hydrogel, Polyethylene Glycol Dimethacrylate / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D011134:Polysaccharides / Q000737:chemistry*; D012212:Rheology; D014783:Viscosity
chemical_list: D001881:Borates; D011134:Polysaccharides; C519976:hydroxypropyl guar; D020136:Hydrogel, Polyethylene Glycol Dimethacrylate
keywords: Borate crosslinked hydroxypropyl guar gum hydrogel; Hydraulic fracturing; Hydroxypropyl guar gum; Rheological properties; pH