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AbstractUnderstanding mechanical degradation is crucial for successful polymer flooding. In this study, the effects of stretching velocity, pore-throat ratio, polymer concentration, and migration distance on the mechanical degradation of HPAM were studied using a pore-throat model. Additionally, the contribution of tensile degradation at the entry point of the pore-throat model to the overall mechanical degradation was assessed through extrapolation. The experimental results indicate that tensile degradation at the entry point is the primary cause of the mechanical degradation, and its contribution is positively related to the flow rate. The mechanical degradation correlates positively with the stretching velocity (0.41 ∼ 6362s−1), pore-throat ratio (6 ∼ 60), and polymer concentration (500 ∼ 2200mg/L). Moreover, higher flow rate amplify the effects of changes in polymer concentration and pore-throat ratio on mechanical degradation. As the migration distance increases, the mechanical degradation initially increases and then stabilizes in the pore-throat model, whereas in the sand-packed model, the mechanical degradation continues to increase with increasing migration distance. This study enhances our understanding of polymer mechanical degradation and offers insights for developing strategies to reduce mechanical degradation and improve polymer-enhanced oil recovery. [ABSTRACT FROM AUTHOR]

AbstractInterfacial tension (IFT) reduction and emulsification are two important mechanisms of surfactant flooding. However, for light oil reservoirs with different permeabilities, whether which mechanism is more important in improving displacement efficiency remains unclear. In this study, surfactants with strong emulsifying properties and ultralow IFT were screened using an interfacial tensiometer and a self-developed emulsification performance tester. The ability of the two surfactants to improve displacement efficiency was compared through a series of core flooding experiments. Experimental results showed that the surfactant with ultralow IFT did not have strong emulsifying properties. With the decrease in permeability, the oil displacement efficiency improved by emulsification increased first and then decreased, whilst that improved by IFT reduction declined. Moreover, IFT reduction was the dominant mechanism to improve oil displacement efficiency in medium-high and ultralow permeability reservoirs, whilst emulsification was dominant in low permeability reservoirs. The comprehensive utilization of multiple mechanisms and the combination of technologies should be considered when surfactant flooding is used in reservoirs with ultralow permeability. This work advances our current understanding of surfactant flooding and provides a reference for the formulation of plans to enhance oil recovery in light oil reservoirs. [ABSTRACT FROM AUTHOR]

Anomalous solid-like liquids at the solid–liquid interface have been recently reported. The mechanistic factors contributing to these anomalous liquids and whether they can stably exist at high vacuum are interesting, yet unexplored, questions. In this paper, thin slices of silica tubes soaked in hexadecane were observed under a transmission electron microscope at room temperature. The H-spectrum of hexadecane in the microtubules was measured by nuclear magnetic resonance. On the interior surface of these silica tubes, 0.2–30 μm in inside diameter (ID), a layer (12–400 nm) of a type of non-volatile hexadecane was found with thickness inversely correlated with the tube ID. A sample of this anomalous hexadecane in microtubules 0.4 μm in ID was found to be formable by an ion beam. Compared with the nuclear magnetic resonance H-spectroscopy of conventional hexadecane, the characteristic peaks of this abnormal hexadecane were shifted to the high field with a broader characteristic peak, nuclear magnetic resonance hydrogen spectroscopy spectral features typical of that of solids. The surface density of these abnormal hexadecanes was found to be positively correlated with the silanol groups found on the interior silica microtubular surface. This positive correlation indicates that the high-density aggregation of silanol is an essential factor for forming the abnormal hexadecane reported in this paper. [ABSTRACT FROM AUTHOR]

In order to alleviate the contradiction between injectability of the profile control agent and its profile control performance, a novel core‐shell heterogeneous structure colloidal particles (CSA) were synthesized, and the mechanism of self‐aggregation plugging was proposed. Cross‐linking inside the nanoparticles and chain‐growth polymerization via capturing acrylamide in the aqueous phase result in the formation of core‐shell heterogeneous structures as proved by TEM observation and XPS analysis. Moreover, CSA nanoparticles exhibit good hydrophilic properties, outstanding thermal stability and limited expansion capacity. Effects of different metal cations and surface group on the self‐aggregation time of CSA nanoparticles were systematically studied. Results showed that divalent cations contributed to more significant aggregation of CSA nanoparticles in comparison to monovalent cations. The increasing cations concentration and valency decreased the thickness of electric double layer, which lead to a decrease in the zeta potential. Core flooding test shows that the injection of nanoparticles which diameter is much smaller that of pore‐throats into the target reservoir can not only successfully enter the depth of porous media, but also effectively block the high permeability areas by the formation of self‐aggregation particle clusters. This study provides a new method for the equilibrium between nanoparticles injectivity and in‐depth profile control of nanoparticles. [ABSTRACT FROM AUTHOR]

To solve the contradiction between the injectability of the profile control agent and its profile control ability in low-permeability reservoirs, a novel in-situ polymeric microsphere profile control agent is proposed. In-situ-polymeric microsphere (ISPM) emulsion was injected into the formation by polymerization to form microspheres for profile control. The emulsion was composed of divinylbenzene, acrylamide monomer, surfactant fatty acid polyoxyethylene ether sulfate, sorbitan oleate and p-hydroxyanisole. An ISPM particle diameter of 1.88 to 30.60 μm was achieved by adjusting the amount of Span80. The ISPM emulsion polymerization time was set to a maximum of 8.4 hours to ensures that the microsphere emulsion could be successfully injected into the formation. Polymerization reaction time increased with the increase of salinity. pH has no significant effect on the reaction time in the range of 5 to 8. Fourier transform infrared spectroscopy (FT-IR) experiments showed that the ISPM emulsion could be polymerized in tiny pores to form microspheres. Furthermore, multipoint pressure measurement experiment and electron microscopy results showed that the ISPM emulsion presented good injectability in low-permeability cores, and the microspheres formed after emulsion polymerization achieved deep plugging in cores. The injectability and blocking effect of the core with ISPM was found to be better than with microspheres (61.7%) for the blocking rate of the core at 10–15 cm deep reached 81.55%. The double-layer heterogeneous core flooding experiments showed that ISPM could expand the sweep volume of subsequent injection fluids and achieve improved oil production and water control. The composite slug composed of surfactant BA and ISPM demonstrated better profile control effect than the ISPM slug alone, and the enhanced oil recovery factor reached 15.65%. [ABSTRACT FROM AUTHOR]

In this letter, we present new insight into the response behaviors of triaxial induction tools. The symmetrical measurements by two sets of receiving coils fixed on both sides of the transmitting coils are simulated in deviated wells. Theoretical analysis and numerical simulations show that some cross-components of two symmetrical receivers satisfy reciprocity principle, while other corresponding components have the same response behavior with both the shoulder-bed effects and borehole effects. The reciprocity can be applied to data processing of existing triaxial induction tools with unilateral configuration. A rule is provided to determine a triaxial receiver as Up-receiver or Down-receiver before data processing. [ABSTRACT FROM PUBLISHER]

Sodium-ion batteries (SIBs) are promising candidates for large-scale energy storage systems due to the abundance and wide distribution of sodium resources. Various solutions have been successfully applied to revolve the large-ion-size-induced battery issues at the mid-to-low current density range. However, the fast-charging properties of SIBs are still in high demand to accommodate the increasing energy needs at large to grid scales. Herein, a core-shell Co 2 VO 4 /carbon composite anode is designed to tackle the fast-charging problem of SIBs. The synergetic effect from the stable spinel structure of Co 2 VO 4 , the size of the nanospheres, and the carbon shell provide enhanced Na + ion diffusion and electron transfer rates and outstanding electrochemical performance. With an ultrahigh current density of 5 A g -1 , the Co 2 VO 4 @C anode achieved a capacity of 135.1 mAh g -1 and a >98% capacity retention after 2000 cycles through a pseudocapacitive dominant process. This study provides insights for SIB fast-charging material design and other battery systems such as lithium-ion batteries.