Mechanistic Study of Oil/Brine/Solid Interfacial Behaviors during Low-Salinity Waterflooding Using Visual and Quantitative Methods

Despite the many studies of low-salinity waterflooding (LSWF), its underlying mechanisms are not well understood as a result of the complexity of the oil/brine/solid interfacial behaviors. Moreover, the widely held belief that LSWF is effective only under certain conditions has not been conclusively proven. Therefore, the static and dynamic interfacial behaviors during LSWF were visually and quantitatively studied in this work to elucidate the underlying mechanism(s). The results showed that LSWF effectively promotes oil recovery by causing double-layer expansion (DLE) and hydrocarbon solubilization. The DLE resulted from multicomponent ion exchange (MIE), as revealed by contact angle, ζ potential, and conductivity measurements. Emulsions prepared with low-salinity brines (≤0.21 wt %) were noticeably heavier and quite stable, demonstrating the significant solubilization effect of LSWF. The oil displacement dynamics observed in a visual micromodel indicated that LSWF increased the oil recovery factor by 4% (secondary) and 1.7% (tertiary) in water–wet porous media, whereas in oil-wet porous media, LSWF was even more efficient than high-salinity waterflooding (HSWF) when employed as the secondary mode. Moreover, the macroscopic sweep and microscopic displacement efficiencies were quantitatively determined using an image analysis technique to verify the proposed mechanisms

The Potential of a Novel Nanofluid in Enhancing Oil Recovery

A surface-active and “green” flooding agent, modified nanocellulose (NC), which is expected to be an alternative to the current flooding systems for enhancing oil recovery (EOR), was provided in this work. The physical properties of the NC samples including dispersity, rheology, phase behavior, emulsifiability, etc., as a function of mass fraction and charge density, were comprehensively studied to evaluate their EOR potential. The results indicate that this modified nanomaterial could be well dispersed in 1 wt % NaCl brine, forming a series of homogeneous nanofluids at the concentration above 0.4 wt %. Rheological analysis evidenced the viscoelastic properties and pronounced shear-thinning behavior of the nanofluids. Because of the presence of the active groups, the dynamic interfacial tension (Oil/Nanofluid) decreased to an order of 10^–1mN/m, which accordingly promotes the microscopic recovery efficiency through an emulsification effect. It was also observed that the emulsifiability of the nanofluids was closely related to the charge density. Visual EOR experiments were conducted in a micromodel, from which two mechanisms, (1) sweep volume improvement and (2) emulsification and entrainment, were established for NC nanofluid flooding. As an eco-friendly material, this nanofluid is supposed to be a promising flooding agent in the near future

Prognostic value of plasma EGFR ctDNA in NSCLC patients treated with EGFR-TKIs

<div><p>Objective</p><p>Epidermal growth factor receptor (EGFR) specific mutations have been known to improve survival of patients with non-small-cell lung carcinoma (NSCLC). However, whether there are any changes of EGFR mutations after targeted therapy and its clinical significance is unclear. This study was to identify the status of EGFR mutations after targeted therapy and predict the prognostic significance for NSCLC patients.</p><p>Methods</p><p>A total of forty-five (45) NSCLC patients who received EGFR-TKI therapy were enrolled. We identified the changes of EGFR mutations in plasma ctDNA by Amplification Refractory Mutation System (ARMS) PCR technology.</p><p>Results</p><p>In the 45 cases of NSCLC with EGFR mutations, the EGFR mutation status changed in 26 cases, in which, 12 cases (26.7%) from positive to negative, and 14 cases (31.1%) from T790M mutation negative to positive after TKI targeted therapy. The T790M occurance group had a shorter Progression -Free-Survival (PFS) than the groups of EGFR mutation undetected and EGFR mutation turned out to have no change after EGFR-TKI therapy (p < 0.05).</p><p>Conclusions</p><p>According to this study, it’s necessary to closely monitor EGFR mutations during follow-up to predict the prognosis of NSCLC patients who are to receive the TKI targeted therapy.</p></div

Influence of Individual Ions on Oil/Brine/Rock Interfacial Interactions and Oil–Water Flow Behaviors in Porous Media

The low salinity effect (LSE) in enhanced oil recovery (EOR) is widely accepted. However, its underlying mechanisms remain unclear due in part to the complex interactions at the oil/brine/rock interface. The chemistry of brine largely depends on the ionic composition. Thus, in this work, attention was placed on the roles of individual ions and salinity in LSE through direct measurements of oil/brine/rock interfacial behaviors, oil displacement efficiencies, and oil–water relative permeability in sandstone porous media. The results showed that the oil/water interfacial tensions (IFTs) were weakly dependent on ion and the lowest IFTs were generated at the salinities of 0.2–0.5 wt %. In contrast, the interfacial dilational modulus varied significantly with ion types and salinities due to the adsorption of polar components at the oil/water interface. Moreover, wettability alteration of the sandstone surface was found to be associated with the divalent ions in our work. As a result of the viscoelastic interfaces, the breakage of oil column into oil droplets or ganglia was delayed, which subsequently led to the improvement of the oil–water relative permeability and oil displacement efficiencies. Based on the analysis, it was concluded that HCO₃^–, Mg²⁺, and SO₄^2– were potential-determining ions (PDIs) in LSE. The results of the tests, to our knowledge, are the first that particularly emphasize the roles of individual ions at the interfaces and oil–water flow patterns in porous media

A Scalable “Junction Substrate” to Engineer Robust DNA Circuits

Versatile building blocks are essential for building complex and scaled-up DNA circuits. In this study, we propose a conceptually new scalable architecture called a “junction substrate” (J-substrate) that is linked by prepurified double-stranded DNA molecules. As a proof-of-concept, this novel type of substrate has been utilized to build multi-input DNA circuits, offering several advantages over the conventional substrate (referred to as a “linear substrate”, L-substrate). First, the J-substrate does not require long DNA strands, thus avoiding significant synthetic errors and costs. Second, the traditional PAGE purification method is technically facilitated to obtain high-purity substrates, whereby the initial leakage is effectively eliminated. Third, the asymptotic leakage is eliminated by introducing the “junction”. Finally, circuits with the optimized J-substrate architecture exhibit fast kinetics. We believe that the proposed architecture constitutes a sophisticated chassis for constructing complex circuits