Effect Of Polyisobutylenesuccinimide On The Colloid Behavior Of Clay Particles In Nonpolar Solvent

In low-temperature condition, maintaining of proper rheological properties of drilling fluids is of great importance in the drilling process. However, the dispersion viscosity of organoclay in mineral oil increases significantly and is often out of control in the process of deepwater drilling. In order to solve this problem, a dichain polyisobutylenesuccinimide with sufficient viscosity lowering performance was synthesized and it can alter the low temperature rheological properties from shear thinning behavior to Newtonian behavior. Therefore polyisobutylenesuccinimide is an effective rheological modifier and dispersant at low temperatures in nonpolar solvents. In low-temperature condition, the polyisobutylenesuccinimide molecules adsorb on the surface of organoclay particles by hydrogen bonding interactions. The combination of steric stabilization and modification of the Hamaker constant of the particles leads to stable organoclay dispersions. In contrast, polyisobutylenesuccinimide has no significant impact on the long-term dispersibility of unmodified montmorillonite in mineral oil, because of the lower surface coverage.The main content of the dissertation includes the following parts:i) The montmorillonite sample was purified with sedimentation method and the organoclay was synthesized by the cationic exchange interactions.ii) A dichain polyisobutylenesuccinimide was synthesized by a two-step synthesis method and purified by column chromatography. The product was characterized by Fourier transform infrared spectroscopy and gel permeation chromatography.iii) The effects of polyisobutylenesuccinimide on low-temperature rheology and dispersibility of organoclay particles in mineral oil were investigated by rheological measurements, sedimentation experiments, optical microscopic observation and transmission electron microscopy. The dispersion mechanism was investigated by Fourier transform infrared spectroscopy, adsorption measurements and X-ray diffraction.iv) The effect of polyisobutylenesuccinimide on the dispersibility and rheological properties of unmodified montmorillonite in mineral oil at low temperatures was also investigated by rheological measurements, sedimentation experiments, and adsorption measurements, with the same methods as organoclay.