Salt-tolerant surfactant for dilute surfactant flooding in high-salinity reservoirs: Residual oil stripping and displacement mechanism and efficiency by ultra-low interfacial tension

© 2020, Society of Petroleum Engineers Dilute surfactant flooding is a promising EOR method. It is more economical and easier to be controlled in reservoirs compared with microemulsion flooding where high surfactant concentration is needed. In this work, we present a salt-tolerance surfactant that can attain ultra-low interfacial tension (IFT) by a low surfactant concentration (0.2wt%) under high salinity condition. And its oil stripping and displacement mechanism and efficiency under ultra-low IFT condition were investigated. A novel anionic-nonionic surfactant with a low concentration of 0.2 wt% was used to prepare surfactant solutions at different salinity conditions. Ultra-low IFT (10-3 mN/m) was obtained at high salinity condition. These surfactant solutions were used for oil film stripping experiments in visual oil-wet quartz cell and filtration experiments in transparent sand pack model as well as two-parallel core flooding model under heterogeneous permeability conditions to study oil stripping and displacement mechanism and efficiency by ultra-low IFT. Oil film can be effectively stripped only under ultra-low IFT condition at high salinity condition with the occurrence of wettability reversal (from oil-wet to water-wet). Oil film is stripped in the form of oil drops by automatically shrinking. The stripping mechanism by ultra-low IFT can be attributed to the reduction of water-oil IFT, water-solid surface IFT, and wearability reversal, which thus reduces the work of adhesion. Filtration experiments showed that a high displacement efficiency (additional oil recovery is about 16-23% depending on the heterogeneity) was yielded under ultra-low IFT condition at high salinity condition in dilute surfactant flooding process. In addition, a new EOR mechanism was found that ultra-low IFT can re-mobilize the trapped oil in low-permeability layer that cannot be displaced by water flooding under heterogeneous permeability conditions without any additional conformance treatment. This anionic-nonionic surfactant can obtain ultra-low IFT at high salinity condition at a low surfactant concentration (0.2 wt%), which can effectively strip residual oil film and re-mobilize trapped oil in low-permeability zone that cannot be mobilized by water flooding under heterogeneous permeability. The development of this salt-tolerance surfactant and finding of its EOR mechanism will improve the application of dilute surfactant flooding in those reservoirs with high salinity

New behavioral forms of sportsman students identification in university digital educational reality

The relevance of the research is due to a wide range of changes in the University educational reality caused by the influence of the Internet, computers, smartphones, mobile devices and modern gadgets on the behavioural forms of student identification. These processes are becoming a matter of particular concern to the public and University teachers. In this regard, this study reveals the features of the value priorities of the University digital educational reality, which modify the behavioural forms of student identification. In the course of pedagogical modelling, which is the leading research method, the phenomenon of new behavioural forms of student identification is identified as the leading idea of the University digital educational reality. This article reveals the key values of student identity identification in the University digital educational reality. The structure and content of new behavioural forms of student identification are established. Based on the research materials, the correction module of new behavioural forms of student identification in the University digital educational reality is justified. The module effectiveness is proved by the results of using new behavioural forms of student identification in the University educational process. The materials of the article are recommended to teachers, methodologists, organizers of the educational process and University students. © Faculty of Education. University of Alicante

A bidomain threshold model of propagating calcium waves

We present a bidomain fire-diffuse-fire model that facilitates mathematical analysis of propagating waves of elevated intracellular calcium (Ca) in living cells. Modelling Ca release as a threshold process allows the explicit construction of travelling wave solutions to probe the dependence of Ca wave speed on physiologically important parameters such as the threshold for Ca release from the endoplasmic reticulum (ER) to the cytosol, the rate of Ca resequestration from the cytosol to the ER, and the total [Ca] (cytosolic plus ER). Interestingly, linear stability analysis of the bidomain fire-diffuse-fire model predicts the onset of dynamic wave instabilities leading to the emergence of Ca waves that propagate in a back-and-forth manner. Numerical simulations are used to confirm the presence of these so-called "tango waves" and the dependence of Ca wave speed on the total [Ca]. The original publication is available at www.springerlink.com (Journal of Mathematical Biology