Nowadays, the unconventional shale-oil and shale-gas reservoirs are developed by fracking technology, using sand as proppant particles in order to improve the hydraulic fractures conductivity. The use of sand as proppant particles has been conceived for a conventional sandstone reservoir and then transfer the knowledge and practice to unconventional reservoirs, generating several operational and technical challenges, such as a low ratio of stimulated volume to propped up volume, sand proppant embedded in the fracture walls, proppant flowback, supply and logistics problems. Several unconventional reservoirs around the world have natural fractures filled with diagenetic CaCO3 (mainly calcite and aragonite) with a characteristic "dog-tooth" texture, which confers high fracture conductivity, as well as mechanical resistance and no proppant flowback. The reservoirs associated to natural fracture systems filled with these carbonates have a high production rate due to high fracture conductivity. Geomimetic is a technique based on the imitation of natural geological processes. In this work, geomimetic has been applied to generate in situ crystal network proppants during hydraulic fracturing of shale reservoirs from the fluid fracture. We present the results obtained in the laboratory of fracture conductivity under confinement tests of plugs propped with the novel Y-Calcite technology vs. plugs propped with the standard sand proppant technology. This technology can provide a geological solution for a geological problem, taking nature as a source of inspiration. Moreover, the CO2 fixation underground by CO2 mineralization converted this development into an environmentally friendly technology.
The development of unconventional reservoirs has largely been carried out using hydraulic fracturing technology developed for conventional reservoirs. Hydraulic stimulation techniques using sand as proppant particles have been widely applied to shale reservoirs, which generated several operational and technical challenges (i.e., low stimulated vs. propped up volume ratio, embedding effect, proppant flowback) (Cooke, 1973; Cutler et al., 1985; Much et al., 1987; Kurz et al., 2013; Fan et al., 2021; Zhang et al., 2015.; Marco et al., 2018). Proppants are responsible for enhancing the conductivity of hydraulic fractures once the stimulation was realized on low-permeability unconventional shale reservoirs.