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.
This paper evaluates the maximum flow rate before the sand production initiates while flowing back a reservoir after the hydraulic fracturing treatment. The experiments are performed in a high pressure slot which simulates a fracture. The slot is a parallel plate device, which is 7 ft high and 9 1/3 ft long with provisions for varying fracture gap width. The slot is filled with proppant to simulate a propped fracture, then, the closure pressure is applied with 12 actuators to simulate confining pressure on the proppant pack. Water is pumped into the slot to simulate flowing back of the fracturing fluid. The water flow rate is varied till the proppant pack destabilizes, and the sand production begins. The sand distribution is observed in the fracture with a vision system.
The experimental results show that the critical water flowback rate decreases as the closure pressure increases, or when the fracture gap width increases. However, the sand-free maximum water flow rate increases as the sand size increases for a given fracture gap width. Lastly, the cumulative sand production decreases as the closure stress decreases at a particular flow rate. The visual observations of the proppant flowback phenomena show that the sand production initiates close to the perforation. After the initiation of the sand flow, continued pumping of the water results in sand production through a channel formed in the proppant pack.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.