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Amphiphilic nanosheets have gained great attraction in diverse applications owing to their unprecedented performance. In this paper, amphiphilic molybdenum disulfide (CTAB−MoS 2 ) nanosheets were prepared through a one-step simple hydrothermal method, and the physicochemical properties were systematically investigated. The results showed that the CTAB−MoS 2 nanosheets displayed a distinct ultrathin flakelike structure and a lateral size in the range of 95 nm. More specifically, the presence of defect sites over the surfaces of MoS 2 nanosheets facilitated linkage with CTAB molecules, which made MoS 2 amphiphilic. Because of the amphiphilic nature, the CTAB− MoS 2 nanosheets could be steadily dispersed in water phase, reduce the oil−water interfacial tension, alter wettability of the solid surface, and stabilize emulsions at ultralow concentrations (50 mg/L). By observing and analyzing the interfacial behavior of CTAB−MoS 2 nanosheets in a simulated oil/brine system, it was found that CTAB−MoS 2 nanosheets could be adsorbed at the oil− water interface in the form of multilayer adsorption, and the adsorption layer (oil−water interfacial film) exhibited higher strength elasticity. This work provides a scalable method for preparing amphiphilic nanosheets and reveals the physicochemical properties of CTAB−MoS 2 amphiphilic nanosheets.

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Microemulsion with excellent properties has shown significant potential in enhancing oil recovery from tight formations by spontaneous imbibition. High temperature resistant and permeable flooding nanofluid (HTPF-NF) was prepared through microemulsion dilution method. Firstly, an evaluation process of HTPF-NF properties was evaluated through the particle size and high temperature resistant experiments, interfacial tension (IFT) and wettability measurements, as well as the static adsorption experiment. Meanwhile, Transmission Electron Microscope (TEM) was utilized to characterize the particle size and morphology of HTPF-NF before and after solubilization of the crude oil. Optical Microscope (OM) was also used to observe the morphological characteristics of emulsified oil droplets. Then, the spontaneous imbibition oil recovery (SIOR) mechanisms of- HTPF-NF were proposed ulteriorly by adopting imbibition tests and CT scanning technology. Moreover, the field application effects of HTPF-NF micro-fracture huff and puff in Shengli Oilfield were also analyzed. The results show that the optimum concentration of HTPF-NF is 0.2wt% with excellent comprehensive performances. Under this concentration, the particle size is 7.5 nm, the IFT value reaches ultra-low IFT, the wettability alteration ability is remarkable and the adsorption loss is minimized. Afterwards, adhesion work reduction factor (AWRF), solubilization coefficient (SC) and the self-driving force (SDF) are defined and calculated based on the IFT and contact angle for quantitatively analyzing the SIOR mechanisms. Furthermore, the data and images of spontaneous imbibition and CT scanning present that the longer the imbibition distance, the higher SIOR of HTPF-NF. In conclusion, the SIOR mechanisms of HTPF-NF are summarized as follows: remarkable property of solubilizing crude oil, brilliant ability of reducing oil/solid adhesion work by synergistic effect of IFT reduction and wettability alteration, and excellent capability of increasing imbibition distance by larger self-driving force. After soaking for two months, YB well was produced with the dramatic increase of the liquid production from 9.55 bbl/d to 34.5 bbl/d, the oil production from 5.15 bbl/d to 19.1 bbl/d and the water cut from 27.3% to 40.8%.

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The formation of the dominant channel of water is a severe problem for most of the oilfields. Recently, gel and nanoparticles regarded as conformance water materials have attracted more attention to control water-cut and enhance oil recovery (EOR) in many water invasion reservoirs. However, nanogel particles possessing synergic properties of nanoparticles and gel are currently unavailable, which causes barrier to EOR. Here, high viscosity α-starch nanogel particles were synthesized to play the synergistic role of gel and nanoparticles economically. The average diameter of nanogel particles was 30 nm with dispersion viscosity of 250 mPa·s at 90°. Through flooding experiments, we demonstrated both light and heavy oil recovery rates reached around 30%. The nanogel particles promotes to displace oil droplets from the rock surface due the creation of the structural disjoining pressure. Also, its high viscosity properties help to drag oil clusters out of the oil phase.

Spontaneous imbibition is an effective method to improve the oil recovery of tight reservoirs.The development and research of nano-emulsion provide a new technical direction for improving spontaneous imbibition oil recovery (SIOR) in tight reservoirs.The salinity has a significant effect on the properties and spontaneous imbibition of nano-emulsion, but the effect on the imbibition mechanisms is still unclear.In the paper, thelower nano-emulsion system with core-shell structures, called HS-LNE,is prepared by nano-emulsion dilution method.Afterwards,the properties and imbibition mechanisms of HS-LNE under different salinitiesare studied.Firstly,the particalsize andstability of the HS-LNE system are evaluated by centrifugation and spectroscopy. What's more, the interfacial tension (IFT), wettability,and adsorption experiments under diffierent salinitiesare carried out, and the salinity influences on the physicochemical properties of the HS-LNE system is systematically analyzed.At the same time, the SIORvariationlaw of the HS-LNE system under different salinitiesis comprehensively explored through static spontaneous imbibition experiments.The experimental results show that the HS-LNE system has excellent stability at high salinity. Moreover, as the salinity increasing, the IFT of the HS-LNE system decreased, and the wettability alternationincreased.However, the adsorption on solid interfaceswas not significantly changed and SIOR reached the highest value of 50.27% at the optimal salinity (50×103mg/L). Finally, the HS-LNE system with the optimal salinity was selected for the field test forpermeability enhancement and flooding in Well Gan 128 in Jilin Oilfield. The oil production was increased by 450 t after 5 months, with an estimated validity period of 24 months and a cumulative oil production increase of 1900 t.