Effects of Crosslinking Chemistry on Proppant Suspension in Guar Networks

Abstract

Dynamic proppant suspension behavior of carboxymethyl hydroxypropyl guar (CMHPG) crosslinked with labile (reversible) and inert (irreversible) crosslinkers are quantified and compared in this work. In reversibly crosslinked CMHPG by borate, particle settling slows with increased imposed orthogonal shear rate and proppants remain suspended for long periods above a critical shear rate. On the contrary, in irreversible zirconium crosslinked CMHPG, particle settling is negligible at low shear rates, dramatically accelerating above a critical shear rate. Local flow field data was obtained to provide insight into the dramatically different particle settling behavior. It was observed that the slowing of particle settling with increased shear rate in borate crosslinked CMHPG originates from shear-induced gelation, which leads to significant increases to both viscosity and elastic stresses. For zirconium crosslinked CMHPG sheared at low shear rates, the local velocity profile is flat, indicating that the network remains intact with negligible flow in the bulk. Above the critical shear rate, the velocity profile becomes sloped, indicating breakup of the network. Therefore, reversibly crosslinked polymers suspend proppant better at high shear rates with an upper critical shear rate for proppant suspension, whereas irreversibly crosslinked polymers suspend proppant better at low shear rates with a lower critical shear rate for proppant suspension. These findings provide valuable guidance in terms of optimizing fracture fluid design to help maximize proppant transport into fractures.

Chelating Agents Usage in Optimization of Fracturing Fluid Rheology Prepared from Seawater

“…CMHPG is reversibly crosslinked by borate, which allows the proppant to be suspended for longer times at high shear rates. While zirconium irreversibly crosslinked with CMHPG where the minimal proppant settling is noticed at low shear rates [ 26 ].…”

Laboratory Evaluation of a Low pH and Low Polymer Concentration Zirconium-CMHPG Gel System for Hydraulic Fracturing

“…Moreover, transition metal cross-linked polymer fluids are shear-sensitive, from which leads to an irreversible loss of viscosity. 40,41 To overcome this shortcoming, several types of delay agents, also called ligands once they have been coordinated to the metal center, are introduced to retard the cross-linking process of guar derivatives with metal ions, such as polyhydroxy compounds, alpha hydroxy acids, and alkanolamines, or their hybrid. 38,42−48 Delay characteristics are related to the original bonds formed by the ligands.…”

Understanding the temperature–resistance performance of a borate cross-linked hydroxypropyl guar gum fracturing fluid based on a facile evaluation method

“…borate, Ti(IV), Zr(IV), and Al(III) ions are oen used to crosslink water soluble polymers. [19][20][21] Guar gum and its derivatives, such as hydroxypropyl guar (HPG), carboxymethyl guar (CMG) and carboxymethyl hydroxypropyl guar (CMHPG), are the most-common polymers used in fracturing uid, accounting for up to 90% of all gelled fracturing uids. 1,22 Meanwhile, to satisfy the criterion to fracture deeper and hotter wells, synthetic terpolymer of 2acrylamido-2-methylpropanesulfonic acid (AMPS), acrylamide and acrylate cross-linked by Zr has been developed and used as a fracturing uid.…”