Synthesis and Inhibitive Mechanism of a Novel Clay Hydration Inhibitor for Water-based Drilling Fluids

In order to solve wellbore instability problem, a novel clay hydration inhibitor PDWC for water-based drilling fluids was synthesized by copolymerization of tris hydroxyethyl diallyl ammonium bromide (THDAB), sodium allyl sulfonate (AS) and methyl methacrylate (MMA) initiated by redox initiation in an aqueous solution. PDWC was characterized by Fourier transform infrared spectroscopy (FT-IR), Gel Permeation Chromatography (GPC) and Thermo-gravimetry-Differential Scanning Calorimetry (TGA-DSC), respectively. Evaluation of experiments indicated that PDWC showed superior clay hydration inhibition ability compared to some polymer and inorganic inhibitors. Characterization methods included particle size analysis, FT-IR, X-ray diffraction (XRD) and Scanning Electron Microscope (SEM) were utilized to study the inhibition mechanism of PDWC, it was observed that PDWC can be adsorbed on the surface of sodium montmorillonite (Na-MMT) by its hydroxyl functional group, which changed the micro-structure of Na-MMT and made the clay particles increased obviously. However, results of XRD demonstrated that it was difficult for PDWC to enter the inner layer crystal of Na-MMT.