The effect of different reservoir minerals on in-situ hydrothermal upgrading of heavy oil in simulated stratigraphic environment

Abstract

In-situ hydrothermal upgrading of heavy oil using nanocatalysts in reservoirs represents a promising future technology for enhanced oil recovery. However, the influence of reservoir minerals on upgrading products remains unclear. This study employed a physical simulation apparatus to investigate the effects of three layered silicate clay minerals (clay, montmorillonite, illite) on hydrothermal upgrading under reservoir conditions with permeability of 2000 (±100) mD, porosity of 25 %, reaction temperature of 240°C, 0.1 wt% nano-Fe₂O₃ catalyst, oil-water ratio of 1:1, and 24-hour duration. Experimental results demonstrate that layered silicate minerals synergistically enhanced the catalytic performance of nano-Fe₂O₃ for heavy oil upgrading. Clay exhibited the most significant upgrading effect, achieving 10.31 % reduction in heavy components with 3.92 % decrease in asphaltene content, followed by montmorillonite (9.69 %) and illite (9.28 %). Mechanistic analysis reveals that clay minerals functioned as effective supports for Fe₂O₃ nanoparticles, preventing aggregation and maintaining catalytic stability. Furthermore, interlayer-adsorbed water molecules decomposed under high temperature to generate active hydrogen species (H⁺), while iron oxide facilitated hydrogen release through Fe²⁺/Fe³ ⁺ redox cycling. These synergistic effects collectively promoted hydrocracking of heavy oil macromolecules and heteroatom (S, N, O) removal. This study elucidates the critical role of layered silicate minerals in nanocatalyst-assisted in-situ heavy oil upgrading, providing theoretical support for improving oil quality and recovery efficiency through mineral-catalyst synergies.