While it is generally known that aging protocols have an important impact on the interaction between crude oil (CRO), brines, and mineral surfaces, the microscopic consequences of the various steps of aging have hardly been described. In this study, we characterize the properties of fluids and carbonate mineral surfaces throughout a series of equilibration steps at 95 °C and correlate these microscopic observations with macroscopic contact angle measurements. Chemical equilibration of CRO (eqCRO) and FW (eqFW) leads to transfer of organic molecules from the former to the latter, causing also a pH change in the eqFW. Confocal Raman microscopy, atomic force microscopy, and infrared spectroscopy are used to reveal how consecutive aging of calcite in eqFW and eqCRO induces: first, in eqFW, considerable surface reconstruction and precipitation of mineral particles with colocalized organic species, and second, upon exposure to eqCRO, the formation of a second adlayer primarily composed of polyaromatic hydrocarbon-rich particles. Our results show how these interconnected microscopic chemical and topographical surface modifications give rise to more "oil wetting" contact angles after the two-step aging procedure.

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Summary Within reservoirs, spatial variations related to mineralogy and fluid chemistry determine the success of improved oil recovery (IOR) technologies. However, the composition and structure of mineral-adsorbent/fluid interfaces, which fundamentally determine the wettability of reservoir rocks and crude oil (CRO) displacement, are unclear. Replicating the diagenetic alterations of carbonates, this study addresses the temperature dependence of the inorganic and organic modifications of calcite by reservoir pertinent fluids as well as its consequences on mineral wettability and reactivity. We apply a suite of characterization methods, namely confocal Raman, scanning electron, and atomic force microscopy (AFM) as well as infrared spectroscopy, to investigate the modifications of carbonates on aging in formation water (FW), CRO-equilibrated FW, and FW-equilibrated CRO. The microscopic modifications of carbonates show a strong dependence on the aging temperature and are varied, encompassing topographical alterations, substitution of lattice Ca2+ ions by Mg2+ ions and the deposition of particles enriched with polyaromatic hydrocarbons (PAHs) as organic adlayers. Aging in the FWs leads to substantial reconstruction of calcite surfaces, with the deposition of magnesium calcite layers at elevated temperatures. Subsequent aging in FW-equilibrated CRO produces an organic coating on the mineral surfaces, which is composed of PAH-enriched particles. Deposited most strongly at high temperature, these organic layers render contact angles more “oil-wet.” In addition, these layers present a limited permeability for ionic species and substantially reduce the dissolution rates of calcite. The multilayer deposition of organic particles, which thus turns out as a key factor for wettability alteration, is attributed to the interconnected bulk and surface reactions for interfacially active constituents of CRO and the surface precipitation of organo-calciumcomplexes. Results of this study are relevant to multiple aspects of reservoir development and maintenance, including laboratory scale wettability and coreflooding experiments, and in-silico modeling. The observed nano- and microscopic surface alterations of carbonates within reservoir mimetic environments improve our understanding of the physicochemical relations between mineralogy and fluid chemistry at the mineral-sorbent/fluid interfaces within reservoirs and thereby provide a starting point for the development of novel advanced IOR strategies.

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Molecularly imprinted polymer-modified glassy carbon electrode (GCE)-based electrochemical sensor is prepared using the electropolymerization of aniline in the presence of melamine (MA) as a template. In this work, the advantages of molecularly imprinted conducting polymers (MICPs) and electroanalytical methods were combined to obtain an electronic device with better performances. The sensor performance was evaluated by cyclic voltammetry (CV) and square wave voltammetry (SWV) with the linear range of 0.6-16 × 10 −9 M, quantification limit of 14.9 × 10 −10 M, and detection limit of 4.47 × 10 −10 M (S/N = 3). The selectivity of the sensor was tested in the presence of acetoguanamine (AGA), diaminomethylatrazine (DMT), casein, histidine, and glycine interfering molecules taken at the triple concentration with MA that demonstrated too small current response compared with that of the analyte indicating high specificity of the sensor towards the template. The sensor was successfully applied to determine MA in infant formula samples with significant recovery greater than 96% and relative standard deviation (RSD) less than 4.8%. Moreover, the good repeatability, recyclability, and stability make this sensor device promising for the real-time monitoring of MA in different food stuffs. K E Y W O R D Selectrochemical sensor, glassy carbon electrode, imprinted polyaniline, melamine

Within reservoirs, spatial variations related to mineralogy and fluid chemistry determine the success of improved oil recovery (IOR) techniques. However, the composition and structure of mineral-adsorbent-fluid interfaces, which fundamentally determine the initial and IOR-altered wettability of reservoir rocks as well as the displacement of crude oil (CRO), are unclear. Replicating the diagenetic alterations of carbonates, this study addresses the temperature dependence of the inorganic and organic modifications of calcite by reservoir pertinent fluids as well as its consequences on mineral wettability and reactivity. We utilize a suite of characterization methods, such as confocal Raman, scanning electron and atomic force microscopy as well as Fourier-transform infrared spectroscopy, to investigate the modifications of carbonates on aging in formation water (FW), CRO-equilibrated FW and FW-equilibrated CRO. The microscopic modifications of carbonates present positive correlations with aging temperature and also are varied, encompassing topographical alterations, cation substitution of lattice Ca2+ ions by Mg2+ ions and the deposition of particles enriched with polyaromatic hydrocarbons (PAHs) as organic adlayers. Aging in the formation waters produce substantial reconstruction of calcite surfaces, with the formation of Mg-calcite layers at elevated temperatures. Subsequent aging in brine-equilibrated CRO produces an organic coating on calcite surfaces, which is composed of PAH-enriched particles. The organic adlayers, deposited at high temperature, produce a transition in the macroscopic contact angles towards a more ‘oil wet’ tendency. In addition, the organic adlayer presents limited permeability and serves as a diffusion barrier to the reactivity of the bound mineral, as evident from substantially reduced rates of calcite dissolution. The multilayer deposition of organic particles is attributed to an interplay between bulk and surface reactions for interfacially active constituents of CRO. With the enrichment of PAHs even observed for mineral grains within reservoir rocks, the permeability and stability of organic adlayers emerge as key factors determining the wettability of carbonates as well as the diffusion behavior of ionic and molecular species at mineral-fluid interfaces. Results of this study are relevant to multiple aspects of reservoir development and maintenance, encompassing laboratory scale wettability and core flooding experiments, in silico models as well as the advancement of IOR strategies. The observed nano- and microscopic surface alterations of carbonates within reservoir mimetic environments facilitate our understanding of the physicochemical relations between mineralogy and fluid chemistry as well as elucidate the organization of mineral-adsorbent-fluid interfaces within reservoirs.

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