Chemomechanical effects of oxidizer‐CO₂ systems upon hydraulically fractured unconventional source rock

Abstract

Carbon dioxide (CO2) as supercritical (scCO2) or foamed (CO2‐Foam) fluid has been tested many times as a fracturing fluid, though it has not yet proven viable. Many challenges have been identified with scCO2 as a fracturing fluid, including poor additive solubility, low viscosity, and limited accessibility. However, CO2 is known to adsorb to organic matter (OM) and displace methane (i.e., enhanced coal bed methane [ECBM] operations), or to mobilize oil as in tertiary enhanced oil recovery. In this study we augment the efficacy of the kerogen control fluid (KCF) for stimulating unconventional rock formations by alternating aqueous oxidizing fracturing fluid with CO2 injection or by combining oxidizers directly with CO2 as a new additive. To this end, KCF‐CO2 tests were designed to treat OM and extend the depth of permeability enhancement. We report the first attempt to combine oxidizer with CO2 in the presence of source shale rocks at elevated temperature and pressure. Scanning electron microscopy imaging of the treated shale sample surfaces demonstrate potential porosity and permeability enhancement, though some mineral and organic deposits are also observed, which may prove to be detrimental. Meanwhile, alternating water‐based KCF with CO2 provides a potential improvement to the KCF as predicted by early lab results on OM. The KCF‐CO2 concept has no equivalent to date in unconventional hydraulic fracturing operations. This technology will contribute to reducing the footprint of anthropogenic CO2 and enhancing its permanent sequestration in unconventional stimulated reservoirs, compliant with our global clean energy initiative of carbon capture, utilization, and storage.

A ReaxFF Potential for Modeling Organic Matter Degradation with Oxybromine Oxidants

“…The other transition of oxygen from BrO À 3 to an oxygen-derived propyl backbone leads to the formation of a CÀ O bond while a CÀ C bond of the propyl species breaks apart, as observed in the TS profile of both ReaxFF and DFT. This step releases ethoxy radical and formaldehyde molecules, which contain a hydrophilic carbonyl polar functional group, in agreement with 13 C solid-state NMR measurements by Hull et al [18] Oxidation of an aromatic hydrocarbon In Figure 4(b), we observe a proton transfer to the oxygen atom of BrO À 4 in the first stage of the oxidation reaction. This reaction structure illustrates how the presence of BrO À 4 can strongly influence the structural deformation of benzene and induce intense vibrations.…”

“…Notably, dicoronylene exhibits fewer instances of CÀ C bond breakage and less fragmented molecular species, underscoring the greater energetic stability of aromatic hydrocarbons against bond breaking compared to aliphatic hydrocarbons. This was experimentally observed in 13 C solid-state NMR measurements by Hull et al that showed aromatic moieties of kerogen remain less degraded after three hours of exposure to oxyhalides as compared to aliphatic moieties. They showed aromatic structures substantially degraded after twenty hours, indicating a more sluggish reaction.…”

“…[32] The CÀ C bond within benzene will likely exhibit epoxidation while undergoing reversible valence tautomerism exhibiting an energy barrier of ~0.13 eV. [56] Oxidative ringopening of the oxygen-derived benzene takes place to form trans, trans-muconaldehyde [32,57] and the linear-like hydrocarbon configuration includes carbonyl hydrophilic polar parts at the end of the backbone as a reaction product similar to those observed in 13 C solid-state NMR measurements. [18] Fourier Transform Infrared (FTIR) spectroscopy experiments of oxidation of a model organic system and organo-kaolin complexes with oxyhalide oxidizers also suggest ring-opening of aromatic moieties during the degradation process.…”

“…[9][10][11] Hence, it is imperative to devise efficient technologies for stimulating kerogen within shale formations to sustain productivity and enhance their suitability for carbon dioxide sequestration. [12,13] Recognition of the complexity of unconventional source rock reservoirs, where hydrocarbon reserves are intricately adsorbed under nanoconfinement within the kerogen matrix, [14] is the driving force to reevaluate and innovate enhanced recovery technologies. Conventional hydraulic fracturing techniques, tailored for more permeable reservoirs, face limitations when applied to kerogen's dense, polymeric structure in these unconventional formations.…”

Preface for the Special Issue Honouring Professor Hisham Nasr‐El‐Din

“…The Canadian Journal of Chemical Engineering is acknowledged for dedicating this special issue to the living memory of Dr. Nasr‐El‐Din. This acknowledgment is also extended to the authors who contributed to this special issue [ 1–28 ] as well as the guest editors:…”