Research into the Impact of Seawater Ionic Composition on the Rheological Characteristics of a Cationic Guar Gum-Based Fracturing Fluid

This study examined the effects of salt content and salt type on the properties of the hydroxypropyl guar gum fracturing fluid. In this study, we conducted a thorough analysis of the impact that various ions in seawater have on the performance of fracturing fluids. We identified the cross-linked polymer that performs optimally at a specific concentration of the binding agent. The experimental conditions, with a constant temperature of 90 °C and a shear rate of 100 s^-1, were designed to simulate harsh reservoir environments. The results indicated that high concentrations of inorganic salt impede the swelling of guava gum, consequently reducing the viscosity of the solution. Initially, the addition of sodium sulfate enhances the viscosity of the guar-based solution; however, as the concentration increases, the effect becomes less pronounced. Solution containing multivalence cations exhibited a more substantial adverse impact on viscosity. In addition, the presence of SO₄ ^2- and Ca²⁺ influenced the temperature resistance of the fracturing fluid. While a minimal concentration of SO₄ ^2- can boost the viscosity, excessive amounts lead to a reduction. The addition of tetrasodium ethylenediamine tetraacetate (EDTA-4Na) first chelates the calcium ions in the salt solution and then increases the viscosity of cationic guar gum by electrostatic action. SEM cryo-electron microscope revealed that the fracturing fluid network became denser after the addition of EDTA-4Na, although the viscosification effects varied among different ions.