Synergistic foam stabilization and transport improvement in simulated fractures with polyelectrolyte complex nanoparticles: Microscale observation using laser etched glass micromodels

摘要

Inaccessibility to direct pore scale observation in hydrocarbon recovery of tight shale formations poses a great challenge to water-energy nexus initiatives and necessitates the use of high throughput technologies to emulate environmentally friendly processes. Herein, we employ a precise glass micromodel fabrication and visualization method to isolate the supercritical CO2 bubbles surrounded by CO2-water lamella prepared in saline produced water stabilized with molecular complexation of zwitterionic surfactants (ZS) and polyelectrolyte complex nanoparticles (PECNP).The Selective Laser Enhanced Etching (SLE) technique was selected for micromodel simulation of highpressure flow. Two representative designs, (1) fracture/micro-crack network and (2) fracture/matrix were etched on fused silica glass with a laser printing machine and scCO2 foam was injected to study the foamability, propagation, stability, and fluid loss properties.The highly monodispersed and uniformly distributed array of scCO2 bubbles were detected in flow of scCO2 foam in highly saline brine containing ionic complexes of positively charged PECNPs and ZS, whereas foam flow with the lamella containing ZS in fractures offered a noticeably large and polydisperse array of scCO2 bubbles. scCO2 bubble motion and deformation were traced, and local description of foam flow was visually examined. The confined array of scCO2 bubbles stabilized by ZS in microcracks was affected by bubble growth and coalescence, whereas the super-populated array of monodispersed scCO2 bubbles with lamella containing complexes of PECNP and ZS were able to fill the channels with stable configurations within the timeframe of comparative stability measurements. The ability of complex fluid to prevent the formation damage was evaluated through fluid loss visualization in micromodels. Probing scCO2 foam transport in homogenous porous media revealed smaller volume leak-off for scCO2 foam containing PECNP-ZS ionic complexes.