Suspension characteristics of borate‐crosslinked gels: Rheology and atomic force microscopy measurements

Abstract

Borate-crosslinked guar gels were prepared and characterized to understand their capability to suspend and transport sand particles through a fracture created in a petroleum reservoir. In this study the crosslinked gels were formulated by varying the borate crosslinker concentrations that were selected such that the gels satisfied the minimum viscosity criteria (100 cP at 100/s) used to evaluate crosslinked gels for their suspension capabilities. However, some of these gels did not exhibit satisfactory particles transport through a slot that models a parallel fracture. These gels were then characterized using oscillatory measurements and atomic force microscopy (AFM) to understand the influence of the microscopic behavior of the crosslinked gels on their macroscopic performance in the slot. The results showed that the suspension transport characteristics of these gels could be described through crosslinked networks formed across the guar polymer. The AFM images and rheological measurements of these gels suggest that the elastic modulus provides more useful information than the viscosity about the crosslinked gel structure and their capability to suspend sand particles.

Rheological properties of konjac glucomannan/SiO2/organic-borate gels

“…Therefore, the sol-gel transition of KGM solutions in the presence of organic borate can be observed, attributing to the formation process of sufficient crosslinking points. The delayed crosslinking function of crosslinker to hydrocolloid was very important in the application as fracturing fluids [5,26] . The organic coordination agent which was called delay additive served to mask the presence of at least a portion of the borate ions at first, thereby providing a reserve of borate ions for crosslinking the fluids as time went on [26] .…”

“…Of necessity, fracturing fluids are prepared on the surface and pumped through tubing in the wellbore to the hydrocarbon-bearing subterranean formation. While high viscosity is a desirable characteristic of a fluid within the formation in order to efficiently transfer fracturing pressures to the rock as well as to reduce fluid leak-off, large amounts of power are needed to pump such high viscosity fluids through the well tubing to the subterranean formation or the earth's surface [5] . In order to save power, several methods were adopted to reduce the friction pressure such as delaying the crosslinking of the polymers.…”

Gelation Behavior Study of a Resorcinol–Hexamethyleneteramine Crosslinked Polymer Gel for Water Shut-Off Treatment in Low Temperature and High Salinity Reservoirs

“…Metallically crosslinked gels, with crosslinkers including Cr 3+ , Al 3+ and Zr 4+ , etc. [18][19][20] typically have lower thermal stability, due to the ionic bonding between the negatively charged carboxylate groups and the multivalent cations. In addition, at elevated temperatures (>70 • C), the reaction rate of metallic crosslinkers with polymers is too fast to place the gel system in the target zones.…”

Potential applications of poly(vinyl alcohol)‐congo red aqueous solutions and hydrogels as liquids for hydraulic fracturing

“…One of the main usages is the suspension of solids in these systems to carry particles to specific sites, avoiding them to settle down 5. In the particular case of hydraulic fracturing,6–8 a fluid is used to create a fracture in a reservoir, and then to transport sand particles through the fractured formation. The sand particles, when placed and uniformly distributed in the fracture, keep it open after the fracturing treatment, allowing oil, gas, or soil contaminants to easily flow to the surface.…”

“…Guar gum suspensions crosslinked with borate ions are the most widely used fracture fluid systems available today 6, 10–13. These gels exhibit viscoelastic fluid characteristics.…”