In hydraulic fracturing operations, proppants coated with resin are used to enhance their crush strength, chemical resistance, and proppant flow back control. The majority of resin-coated proppants are prepared using phenol-formaldehyde resin (Novolac) hardened with hexamine at an elevated temperature of 380-425 oF in a plant setting. The objective of this study is to disclose a simple method to coat proppant at ambient temperature to provide free-flowing curable and pre-cured proppant without loss of any performance.<br/>In this work, a free-flowing resin-coated proppant was prepared by coating 40/70 mesh sand substrate with liquid resin in a 1 Kg batch mixer. The coating was crosslinked with a hardener assisted by a catalyst and an accelerator for curing at ambient temperature. In some cases, diluents were mixed to lower the viscosity of resins, for easy and uniform coating onto the sand grains. Reinforcement of resin coating with carbon nanotube was also studied. Curable and the pre-cured proppants were prepared at room temperature. Coated sand was evaluated by sieve distribution, melt point, loss on ignition, fluid compatibility test, API proppant crush, and API long-term conductivity tests. Microscopy was used to ascertain the full dispersion of nanomaterial in the resin.<br/>The liquid epoxy resin used for coating sand with a viscosity of 12,000 cp was diluted with 10-12.5% reactive diluents to lower its viscosity to 2500-3000 cp. Different kinds and combinations of Lewis acids and alcohols were employed for the quick curing and hardening of the resin. The free-flowing resin-coated sand was prepared from epoxy resin within 5 minutes by employing the catalyst accelerator. The melt point of the fully cured coated sand was greater than 450 oF which indirectly indicated that the prepared coating had a high glass transition temperature (Tg). API Crush resistance test on coated sand provided crush fines of less than 3% at 12k psi. In the unconfined crush resistance test cell, the coated sand did not form the consolidated pack under elevated closure stress and temperature indicating the proppant was fully pre-cured. Dilution of epoxy resin with reactive diluents helped in the uniform dispersibility of nanotubes in the resin as determined by microscopy. API long-term proppant pack conductivity showed improvement in the strength of the coated sand.

Method to produce resin coated proppants at ambient temperature for hydraulic fracturing

ACS Spring 2022

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.