In order to develop high-performance water-based drilling fluid with the aim of meeting the increasing requirement of drilling industry, highly inhibitive and high-temperature-resistant shale inhibitors are essential. In this study, 4, 4 0 -methylenebis-cyclohexanamine was introduced as a potential shale inhibitor. The inhibitive properties of the amine compound in comparison with currently available polyether diamine inhibitor were evaluated using bentonite inhibition test, shale cuttings hot-rolling dispersion test, linear swelling test, and pressure transmission test. The inhibitive mechanism was investigated with zeta potential measurement, X-ray diffraction analysis, and contact angle measurement. The results indicated that 4, 4 0 -methylenebis-cyclohexanamine can inhibit shale hydration and dispersion effectively, and prevent pressure transmission to a certain extent, performing better than that of polyether diamine. Furthermore, the new diamine provides reliable thermal stability as high as 220°C, preserving the benefits of high-temperature wells application. This novel diamine inhibits shale hydration and dispersion with the combination of chemical inhibition and physical plugging. The intercalation into the interlayer of clay with monolayer collapses the hydrated clay structure and expels the water molecules. After adsorption, clay surface became more hydrophobic, which prevents the imbibition of water. The variation of solubility separates the compound from the solution, which can plug the micro-pores of shale and prevent fluid invasion.

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Interest in using nanomaterials to improve shale stability during drilling operations has been increasing.Herein, a polymer microsphere emulsion (PME) as a high-performance shale stabilizer for water-based drilling fluids (WDFs) was prepared via emulsion polymerization. The particle sizes in PME in aqueous solution ranged from 90 to 320 nm. PME was found to exhibit excellent salt tolerance and temperature resistance. The plugging performance of PME was tested through pressure transmission tests. The results indicated that the polymer microspheres in PME could effectively plug shale pores and reduce shale permeability. In addition, rolling recovery tests were used to evaluate the shale hydration inhibition performance of PME. It was found that PME showed great performance for decreasing shale hydration potential. These factors make PME a promising shale stabilizer for WDFs used to drill shale formations.

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Research on using nanotechnology to solve shale instability problems in drilling engineering has been increasing. The combination of amphiphilic polymer and silica nanoparticles may be a new way to improve shale stability. Herein, an amphiphilic polymer/nano-silica composite (poly(styrene-methyl methacrylate-acrylamide)/nano-SiO2) was introduced as a novel shale stabilizer SMA/SiO2 for water-based muds, which possessed the advantages of both physical plugging and chemical inhibition during the drilling operations. The SMA/SiO2 was prepared and characterized by Fourier transform infrared spectra (FT-IR), nuclear magnetic resonance (1H-NMR), transmission electron microscope (TEM), particle size distribution (PSD) and thermogravimetric analysis (TGA) experiments, which confirmed that SMA/SiO2 was regularly spherical with nano-scale and showed good high-temperature resistance. To evaluate the plugging capacity of SMA/SiO2, the pressure transmission test and BET analysis were applied. The results indicated SMA/SiO2 was capable of effectively plugging the pores and fractures in shale. To evaluate the hydration inhibition capacity of SMA/SiO2, the rolling dispersion experiment and contact angle test were adopted. The results demonstrated that SMA/SiO2 could reduce the tendency of shale hydration, which was better than potassium chloride (KCl) and polymeric alcohol (JHC). In addition, SMA/SiO2 only created slight variations on the rheological parameters of the water-based muds (WBMs) and showed a significant filtration control performance. Due to the outstanding performance of physical plugging and chemical inhibition, SMA/SiO2 was expected to be a novel shale stabilizer to solve shale instability problems.