Investigation of the effect of asphaltenes, the natural surfactant in crude oil, on the methane hydrate formation is crucial for flow assurance in deep-water oil and gas field. However, most of recent studies on hydrate growth mainly focused on the impact of artificial and commercial surfactants. Limited attention has been given to the effect of the important natural surfactants presented in crude oil on hydrate film growth, such as asphaltenes. In this study, the influences of dissolved asphaltenes on the properties of oil-water interface and the growth of methane hydrate film were investigated. The morphology of methane hydrate film on the water droplet in the oil phase with different asphaltene concentrations was in-situ visualized in a visual autoclave equipped with microscopic imaging, and the lateral growth rate of the methane hydrate film was measured. The results showed that the addition of asphaltenes could increase the hydrophobicity of the methane hydrate film, inhibit the growth of hydrate, and change the morphology of the hydrate film. The growth rate of the hydrate film was negatively correlated with the asphaltene concentration (0–200 ppm), but stabilized above 200 ppm. In addition, this inhibition effect on the lateral growth rate was negatively correlated with temperature.

AbstractThe efficacy of CO2‐switchable surfactants in reducing viscosity of heavy crude oil has received widespread attention due to its switchable surface activity for constructing reversible emulsion. However, the intricate synthesis processes of these surfactants pose a significant challenge in their practical application. The present investigation involved the preparation of surfactants that are responsive to CO2, specifically dimer acid (DA)/tetramethylpropylenediamine (TMPDA), through a facile mixing approach. These surfactants were subsequently employed to mitigate the high viscosity of heavy crude oil. The study employed a surface tension meter to examine the surface behavior of DA/TMPDA, which demonstrated the potential for reducing viscosity. The study examined the CO2 responsiveness of DA/TMPDA through the application of alternating CO2 and N2. It confirmed the reversible CO2 responsiveness of the surface activator. The results from the emulsification and viscosity reduction assessments suggest that the amalgamation of DA and TMPDA in a 1:1 molar ratio yielded a surfactant. This surfactant demonstrated favorable stability in water and heavy crude oil emulsions, as well as low viscosity and rapid emulsion breaking upon exposure to CO2. This investigation demonstrates that it is feasible to produce surfactants that are responsive to CO2 and possess the ability to reduce viscosity through a straightforward mixing process. This presents a viable approach to utilizing oligomeric surfactants that are CO2‐responsive for the purposes of emulsifying and breaking down heavy crude oil.

Ultra-thin silicon slicing technology plays a critical role in achieving high-efficiency and low-cost solar cells in the photovoltaic (PV) industry. However, the surface phase evolution of silicon wafers under an ultra-thin slicing process and resulting etching behavior remains unclear. In this study, the surface phase evolution of different surface thicknesses of silicon wafers was carefully studied. As the thickness of silicon wafers became relatively thin, the degree of surface stress-induced amorphous silicon (ST-α-Si) significantly increased. Moreover, the UPS test showed that the ST-α-Si layer had an orbital energy level relatively lower than that in monocrystalline silicon, thereby having lower reduction performance during metal-assisted chemical etching (MACE). A copper deposition experiment was conducted to study the etching hindering effect caused by silicon surface ST-α-Si phases. The result showed that the presence of ST-α-Si adversely affected copper deposition. To improve the MACE uniformity, a pretreatment involving the use of HF/H2O2 mixed solution to remove the surface ST-α-Si layer was investigated. After HF/H2O2 pretreatment, the uniformity of inverted pyramids formed through MACE on the silicon wafer surface was significantly improved. Moreover, the reflectance of the MACE-textured surface was reduced to 7.67 % from 10.1 % compared with that without pretreatment. Therefore, this study provides reference guidelines and useful approaches for preparing uniform inverted pyramid surfaces using MACE in ultra-thin silicon wafers.

The adsorption thermodynamics and kinetics of CO2 and six combustion products (H2O, SO2, N2, O2, NO and NO2) of two most commonly used commercial zeolites (13X and 5A) were studied based on validated molecular simulations. Adsorption isotherms at wide range of temperatures (253–333 K) were fitted by a Langmuir model, obtaining equilibrium parameters including the adsorption capacity, strength, heterogeneity and CO2 selectivity from the mixture. The diffusion coefficients, isosteric adsorption heats and distributions of potential energy were simulated for further explanation. The comprehensive evaluation results suggest that, in actual combustion product mixtures, the presence of H2O in combustion products has a significant impact on CO2 capture efficiency. Under the influence of water, the adsorption capacity of CO2 was reduced by over 80%.

AbstractThe addition of salt can irreversibly disrupt the stability of both emulsions and polymer latex. The reversible conversion of amines into organic ammonium salts can be induced by CO2 stimulation, thereby enabling the switching of colloids. The switchable amine, tris[2‐(dimethylamino)ethyl]amine (Me6TRAN), was selected for the study. The electrical conductivity of an aqueous solution of Me6TRAN is modulated by the introduction and removal of CO2. The critical micelle concentration of sodium dodecyl benzene sulfonate (SDBS) was observed to decrease from 1.0 × 10−3 to 5.0 × 10−4 M upon the introduction of Me6TRAN, as confirmed by surface tension measurements conducted under CO2. The emulsion of crude oil, which comprised of SDBS and Me6TRAN, underwent reversible destruction and restoration upon exposure to CO2 and N2. The PMMA latex exhibited a clear phase separation subsequent to CO2 sparging, but attained homogeneity upon N2 sparging. This study is anticipated to introduce a novel avenue for emulsion or polymer latex that can undergo demulsification and emulsification through CO2 stimulation.

Tight oil extraction and offshore oil spills generate large amounts of oil–water emulsions, causing serious soil and marine pollution. In such oil–water emulsions, the resin molecules are bound by π–π stacking and bind to interfacial water molecules via hydrogen bonds, which impede the aggregation between water droplets and thereby the separation of the emulsion. In this study, strongly electronegative oxygen atoms (in ethylene oxide, propylene oxide, esters, and hydroxyl groups) were introduced through poly(propylene glycol)-block-polyether and esterification with acrylic acid to attract negative charges in order to form electron-rich regions and enhance interfacial hydrogen bond recombination. The potential distribution in the demulsifier molecules and their space occupancy were regulated by the polymerization reaction to destroy the π–π stacking interaction between resin molecules. The results show that the binding energies (binding free energy and hydrogen bonding energy) of oxygen-containing demulsifier molecules with water molecules were higher than those of resin molecules with water molecules, resulting in the fission of the hydrogen bonds between resin and water molecules. The introduction of demulsifier molecules that occupied large interfacial space reduced the binding energy between resin molecules from −2176.06 to −110.00 kJ·mol−1. Noteworthy, the binding energy between demulsifier molecules and resin molecules was −1076.36 kJ·mol−1 lower than that between resin molecules (−110.00 kJ·mol−1), indicating the adsorption of the surrounding interfacial resin molecules by the demulsifier molecules and destruction of the π–π stacking between them, thus favoring the collapse of the interfacial structure of the oil–water emulsion and achieving its separation. This study provides important theoretical support for the treatment of oil-contaminated soil and offshore oil spill pollution.

Numerous hydrocarbon discoveries in the lower Urho Formation of the western Mahu Slope, China indicate that potential petroliferous reservoirs may exist in that region. However, issues concerning the reservoir characteristics and associated controlling factors remain unclear. To determine the characteristics and associated controlling factors of these reservoirs, we conducted integrated analysis of the 3D seismic volume, wireline logs, mud logs, cores, thin sections, porosity, and permeability data. Several lithologic types were identified from the core, casting thin section, and mud-log data (including mudstone, sandstone, gravity flow-derived glutenite, transitional glutenite, and traction flow-derived glutenite). The contact relationship was determined from the casting thin section data, and it included point contact and lineal contact, followed by concavo-convex contact and suture contact. We found the dominant pore types were found to be intergranular pores, followed by intragranular pores, intramatrix pores, and cracks. The porosity and permeability data reveal that sandstone and traction flow-derived glutenite commonly form low-porosity and low-permeability reservoirs, whereas transitional glutenite commonly forms low-porosity and ultralow-permeability reservoirs and gravity flow-derived glutenite generally forms low-porosity and ultralow-permeability reservoirs. This integrated analysis finds that tectonic movements and a sedimentary environment control the physical properties of the reservoirs. The tectonic movements control reservoir characteristics through thrust fault systems and large-scale provenance, and the sedimentary environment controls reservoir characteristics via facies distribution and lacustrine fluctuation. The insights gained from this study can provide knowledge about the characteristics and associated controlling factors of the reservoirs in the Permian Lower Urho Formation within the western Junggar Basin. These insights can also benefit petroleum reserve and hydrocarbon production exploration in the study area and further petroleum exploration in other areas with similar sedimentary/tectonic settings.

The Hutubi gas field was put into production in 1998 and then converted into an underground gas storage (UGS) facility in 2013, and since then a cluster of earthquakes associated with seasonal injection and extraction activities have been recorded nearby. To evaluate the fault stability and seismic potential, we established a pseudo-3D geomechanical model to simulate the process of seasonal injection and extraction. Reservoir pore pressures from 1998 to 2019 were obtained through multiphase reservoir simulation and validated by history matching the field injection and production data. We then imported pore pressures into the geomechanical model to simulate the poroelastic perturbation on faults for over 20 years. The fidelity of this model was validated by comparing the simulated surface deformation with global positioning system (GPS) measured data. We used Coulomb failure stress (CFS) as the indicator for the likelihood of fault slippage. The simulation results show that the location of the induced earthquake cluster was within the positive Coulomb stress perturbation (ΔCFS) area, in which fault slippage was promoted. In addition, ΔCFS at the earthquake location kept increasing after the injection began. These findings could explain the induced earthquakes with the Coulomb failure stress theory. Furthermore, we conducted a parameter sensitivity study on the dominant factors such as the maximum operating pressure (MOP), frictional coefficient, and dip angle of the pre-existing fault. The results indicate that the magnitude of ΔCFS caused by seasonal injection and extraction decreases with distance; MOPs are constrained to 32.9, 36.2, and 39.5 MPa according to different ΔCFS thresholds; the critical dip angle ranges are 0–20° and 80°–100°; and strengthening the fault friction can either increase or decrease the seismic potential. This study can help determine the MOP for Hutubi underground gas storage (HTB UGS) and provide a framework for simulating the potential causes of induced seismicity for other sites.

AbstractFor switchable surfactant to be reusable, its property must be activated by a stimulus after it has been utilized. Nonetheless, a plenty of switchable surfactants are environmentally harmful tertiary amines. This study investigates the biocompatible amino acid derivatives, lauroyl arginate ethyl (LAE) as a new biodegradable CO2‐switchable surfactant. In the study, LAE was prepared and its structure was characterized. The variation of pH value was measured to determine the responsiveness to CO2. The surface tension and interfacial tension were measured to determine the surface activity of the material. Finally, CO2 and N2 were injected into the solution to determine reversible emulsification of emulsion. Not only does the LAE have reversible emulsification capacity, but it is also non‐toxic and biodegradable. In the future, its applications in everyday life and industry will expand.

Tight oil is an important unconventional oil resource. However, during the extraction process of tight oil, a large amount of tight oil emulsion is generated, combined with offshore oil releases, have caused serious environmental problems. Owing to the high content of resin molecules, which adsorbed the interfacial water molecules in the form of hydrogen bonds, as well as tightly bound resin molecules via π–π stacking, the interface structure is stable; hence, it is difficult to separate oil and water. In this study, the hydrogen-bond energy of O atoms in common groups and water molecules was analyzed, and the efficient separation of oil and water was realized by the regulation of hydrogen-bond energies of the demulsifier molecules and interfacial water molecules. The O atoms in EO, PO, ester group and hydroxyl group were named as Type 1–6 O atoms. The compatibility of the demulsifier and tight oil was improved by the introduction of an aromatic structure, which combined with the tight oil molecules via π–π stacking. At the same time, by the introduction of Types 1–6 O atoms, the electronegativity (Hydrogen bond acceptor ability) of the demulsifier molecules was optimized to improve the hydrogen-bond energy formed between the demulsifier and water molecules effectively; then, the interfacial resin molecules were replaced to form stronger hydrogen bonds with water molecules, weakening the π-π stacking interaction between resin molecules for clipping the interfacial film; thus, the mass-transfer efficiency of water molecules at the oil–water interfacial is enhanced.