LAUSR

Abstract Currently, the global oil & gas sector is focused on enhanced natural gas exploration from unconventional rock formations. The potential deposits are located within large-scale basins of impermeable shales (hydrocarbons accumulated in closed pores) with plastic zones at great depths with high reservoir pressure. These severe geological conditions determine the application of granulated propping agents, named “proppants”. They are pumped with hydraulic fluid during hydraulic fracturing and subsequently locate tightly inside created rock fractures. Proppants function as a prop to facilitate gas flow up the wellbore. Quartz sands are applied mainly for low pressure basins. However, only ceramic proppants, granules produced from raw clays in a mechanical granulation and sintering process, are proper for deeper shales due to their homogeneity, higher sphericity, and mechanical and chemical stability. Aim of this research was verification of the impact of natural loamy resources (aluminosilicates in powder form) mixed with binder on ceramic proppants quality. Utility of the clays was estimated by their particle size distribution (PSD by laser diffraction method) and thermal stability (thermogravimetry - TGA). The unique platy morphology was determined by scanning electron microscopy (SEM), while energy dispersive spectroscopy (EDS), X-ray fluorescence (XRF) and X-ray diffraction (XRD) revealed chemical-phase composition. Moreover, aluminosilicates were subjected to analysis of specific surface area (BET method) – very crucial for powder consolidation into granules in mechanical granulation. Quality of the granulated, and consequently sintered, bodies was evaluated by calculations of roundness and sphericity coefficient, specific gravity and bulk density, combined with microtomography (μCT) - a key investigation of porosity and proppant settlement in fracture. SEM studies also revealed phase transitions due to high temperature exposition of the green proppants and the correlation with proppant strength, evaluated in crush tests. Moreover, measurements of turbidity and solubility in acids revealed risk of the granules' decay in the shale gas wells. The obtained outcomes show dependence of the proppant's structure on the binder and the loamy materials ratio, proving the utility of the applied natural resources in the granules production. In consequence, these proppants can be used for hydraulic fracturing in severe mining conditions in accordance to the strict international ISO standards.