Polymer Coating over Solid Particles with In Situ Thermal Curing

Abstract

Solid particles coated by cross-linked polymer layers find applications in many areas, including hydraulic fracturing operations. In this study, a hot-melt resin coating process for solid particles is developed and optimized for hydraulic fracturing applications. Phenolic resin is used to coat the particles above its melting point and is subsequently cured in situ by hexamethylenetetramine (HMTA). The coating quality is then characterized by the surface morphology, acid solubility, and crush resistance of the resin-coated particles. The effects of various operating parameters on the coating performance are systematically studied. Among them, temperature is shown to play an especially important role. The coating process involves intricate coupling between resin rheology, HMTA mass transfer, and curing kinetics, all of which are profoundly influenced by temperature. Different constant temperature levels as well as controlled temperature ramps are investigated, and the results show a complex dependence. Higher temperature leads to stronger coating layers with better barrier properties, whereas lower temperature is preferable for better surface morphology. These two trends can be partially reconciled with ramping temperature profiles; the improvement is, however, eventually limited by the rate of heat transfer. This study not only provides insight into the physical and chemical processes underlying the resin coating operation, it also demonstrates a generalizable strategy suitable for various particle coating processes.

Constructing low-cost and high-strength ultra-low-density proppants based on the modification of activated carbon framework with in situ hydrolyzed silane

“…As is well known, the main function that thermoset resins, such as phenolic resin, perform is surface protection. 26 Thus, the phenolic resin was further applied to enhance the KH-ACs and improve the environmental resistance. As is shown in the SEM images of Fig.…”

“…4 Resin-coated proppant is a type of proppant where a thermoset resin is applied to coat quartz sand or ceramic microspheres. 5 The coating on resin-coated sand provides both strength support to the original microspheres and protection against corrosion. However, this type of proppant is not widely used due to the high performance requirements of the resin and the associated high costs.…”

Progress of Polymer Application in Coated Proppant and Ultra-Low Density Proppant

“…Due to its hollow structure, the crushing rate increased to 17.01% at 55 MPa. The influence of curing conditions on the performance of phenolic resin coated ceramic proppant was deeply investigated by Zhang and co-workers [33]. The obtained results revealed that high temperature is conducive to forming a coating with excellent barrier properties, and low temperature is benefit for improving the sphericity and roundness.…”

Facile and Controllable Preparation of Poly(St-co-MMA)/FA Microspheres Used as Ultra-Lightweight Proppants

“…Proppants should have sufficient strength to keep cracks open that will form channels to make the oil and gas flow through conveniently, causing the well production to be increased significantly [ 6 ]. However, traditional proppants such as quartz sand [ 7 ], walnut shells, gravel- and resin-coated sands [ 8 , 9 ], and sintered ceramic [ 10 , 11 , 12 , 13 ] are prone to settling in hydraulic fracturing operations because of their high density, which seriously affects the efficiency of oil and gas exploitation. Therefore, it is significant to develop ultra-lightweight (ULW) proppants with good performance [ 3 , 14 ].…”