In this study, a new type of amphiphilic copolymer SPXFJ, with amide and sulfonate functional groups, was synthesized via the free radical polymerization method. And the chemical structure and properties of this new polymer were characterized by elemental analysis (EA), X-ray photoelectron spectroscopy (XPS), intrinsic viscosity tests, and thermogravimetric analysis (TGA). The hydrophobic association and thermo-thickening properties of SPXFJ copolymer were investigated through viscometer, contact angle tester, highresolution scanning electron microscope analysis, and X-ray laser static scattering (XLSS) test. The test results indicated that SPXFJ copolymer showed superior amphiphilic properties, especially in the solution condition. Furthermore, a thermo-associative behavior was found in the solution that aged at 180 C. Thus, SPXFJ-based drilling fluid showed a higher temperature resistance. The test results, in both high-temperature aging tests and hightemperature high-pressure (HTHP) downhole simulation tests, showed that the water-based drilling fluid showed excellent anti-sedimentation properties with the use of SPXFJ polymer and can be improved significantly, especially in the high-pressure condition. The water-based drilling fluid of 2.0 g/cm 3 showed no sedimentation of barite powders at 180 C/100 MPa, of which the density deviation just reached approximately 0.06 g/cm 3 .

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Quasi-brittle behaviors of cement-based material can be reinforced through diverse methods due to its unique multiscale features. Among them, reinforcing agents are the most direct and effective means, such as slag, metakaolin, and fly ash. These materials can improve the performance of cement stone to a certain extent, but their chemical composition is still mainly silica, which does not in essence change the defects of cement. Therefore, in this experiment, magnesium borate whisker (Mg2B2O5) was used as reinforcer of 90°C class G oil well cement and magnesium borate whisker reinforced cement-based material (MBWRC) was prepared. On the one hand, the performance of mechanical strength was controlled, and the resistance to compression, traction, and bending was included. Furthermore, static stress-strain behaviors analysis and toughness behaviors analysis (dynamic multicycle loading test) were further conducted. Second, mercury intrusion porosimetry (MIP) and scanning electron microscope (SEM) were used to test the characteristics of pores and interfaces of cement-based materials. Through multiscale microstructure analysis, MBWRC was found to have excellent 90°C mechanical performances when compared to control sample’s, for which tensile strength increased to 235% of controlled sample’s, and flexural strength increased to 130%, plus a healthy developed compressive performance, and MBWRC showed much denser pore structure, in which harmless micropore increased from 13.3% to 14.40%, porosity decreased from 17.01% to 16.20%, and permeability decreased from 0.2533% to 0.0205%. Furthermore, MBWRC showed resistance capability to mechanical loading, which can be attributed to the formation of denser pore structure and more excellent mechanical performance.