The amount of fresh water used in hydraulic fracturing can be significantly reduced by employing produced water compatible supercritical CO2 (scCO2) foams. Foams generated using surfactants have suffered from long term stability issues resulting in low viscosity and proppant carrying problems. In this work, foam lamella stabilization with polyelectrolyte complex nanoparticles (PECNP) and wormlike micelles (WLMs) was investigated. Electrostatic interactions were studied as the defining factors in improvement of the foam performance using the PECNP system prepared in produced water. Two oppositely charged polyelectrolytes were investigated to generate a more stable lamellae between the aqueous phase and the scCO2 while degrading in the presence of crude oil. The strong compatibility of the synthesized PECNP with zwitterionic surfactants prepared in highly concentrated brine in the form of WLMs above Critical Micelle Concentration (CMC) helps to develop a highly viscous, dry foam, improving fracture propagation, proppant transport, and fracture cleanup compared to the base case foam system without PECNP. The formation of nanoparticles was verified via zeta potential, particle size analysis, and transmission electron microscopy (TEM) where the underlying mechanism was identified via Raman spectroscopy. Enhanced bulk viscosity and improved foam stability as a result of complexation at the interface was identified with rheometry in addition to sand pack experiments with PECNP-surfactant ratios of 1:9 and 4:6, in 33.3 kppm and 66.7 kppm salinity brines, respectively. The PECNP-surfactant foams reduce fluid loss volume significantly in a tight Kentucky sandstone. Subsequently, morphology and structural parameters of foam bubbles including size, size distribution and lamella thickness as well as film drainage and rate of deformation were studied via visualization techniques. Therefore, the mechanistic study of lamella stabilization and visualization of foam stability in hydraulic fracturing application is presented.

Environmentally friendly waterless fracturing with supercritical CO2 foam prepared in produced water: Mechanistic study

2019 Fall National Meeting

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