Enhancement of Tight Oil Recovery by Amphiphilic Janus Nanosheets

Abstract

Abstract Recently, nanofluid flooding has become one of the promising technologies in enhanced oil recovery. The agglomeration and the insufficient interfacial activity of nanoparticles in an aqueous solution are two major concerns affecting the application effect of nanofluids. Amphiphilic Janus nanomaterials make up for the deficiencies in both aspects compared with homogeneous modified nanomaterials. In this work, we investigate the potential use of an amphiphilic Janus molybdenum disulfide (MoS2) nanosheet (JMDN) as an enhanced oil recovery agent. JMDN was synthesized by the SiO2 Template Method. Firstly, molybdenum disulfide nanosheets were adsorbed on the surface of SiO2 nano-microspheres as a single-sided modification. Then KOH was used to dissolve the SiO2 nano-microspheres, and the other side of the nano-sheet was modified to obtain JMDN. The scanning electron microscope (SEM) and transmission electron microscope (TEM) were used to systematically characterize the morphology and structure of molybdenum disulfide nanosheets. The properties such as wettability, stability and interfacial tension were tested. The effect of using JMDN on low-permeability reservoir recovery was emphasized. Low-permeability core flooding and microfluidic experiments were conducted with a concentration of 50ppm nanofluids. The JMDN with 40nm particle size was synthesized under certain conditions. The results of SEM showed it has 5–6 layers of nanostructures and TEM indicates that hydrophilic carboxyl group and hydrophobic alkyl group respectively exist in two sides of the nanosheet. The modified nanosheet can be stable for 7 days at 90°C. The contact angle experiment shows that the JMDN could effectively change rocks from oil-wet to water-wet. Oil-water interfacial tension is as low as 2.87 mN/m. The core flooding experiment show that the nanofluid could significantly increase oil recovery. Numerous studies focused on the uniform modification of nanomaterials in tight oil recovery. Compared with conventional nanomaterials, the JMDN could strip oil from rock surfaces more efficiently due to its amphiphilic structure. This paper reveals the physical and chemical properties of JMDN and provides a new and efficient nanofluid system for EOR.