Reaction Kinetics Control of Alkaline Activated Materials by Activator Encapsulated Microcapsules for EGS Well Construction

Abstract

During EGS well construction, cement slurry is pumped into a well between a tubular metal body (casing) and geologic formations to provide zonal isolation, to protect metal casing from corrosion and to support the well structure. One of the most important material design considerations for geothermal wells is material pumpability to enable its placement into an underground well. The LBNL team at the Center for Coupled Chemo- Mechanics of Cementitious Composites for EGS (C4M) is addressing this gap with research on delayed solidification of alkaline activated materials (AAMs) in the high-temperature downhole environment of EGS reservoirs. Microencapsulation technology involves entrapment of a substance within microscopic (1 to 1000 μm size) particles of continuous shell with specific properties. For controlling the rection kinetics of AAMs, encapsulation of the reactants (alkaline activator) can be a potentially powerful strategy. The shell can be engineered/functionalized to protect the core materials and prevent reaction for a controlled duration of time, and denatured/breached by specific triggering events. By using a large number of sufficiently small capsules with a diameter less than 500 μm, the reaction sites can be well dispersed within the mixture. In this study, we present our microfluidic-based microencapsulation technology and demonstrate its performance for producing alkaline encapsulated microparticles. Once triggered by elevated temperature, the diffusion characteristics of alkaline solution and reaction with surrounding precursors are investigated via an in-situ HPHT visualization cell. A control test without the microcapsules will be compared, along with characterizations by transmission electron microscopy on the nano-scale structures to gain gaining fundamental understanding the reactions’ pathways.