Hyperbranched polyethylenimine modified with silane coupling agent as shale inhibitor for water-based drilling fluids

Abstract

Hyperbranched polyethylenimine modified with a silane coupling agent (Si-HPEI) as a shale inhibitor was synthesized by the Michael addition reaction of hyperbranched polyethylenimine (HPEI) and methacryloxypropyltrimethoxysilane. The structure of Si-HPEI was characterized by Fourier transform infrared spectroscopy and proton nuclear magnetic resonance. The inhibitory properties of Si-HPEI in comparison with currently available inhibitors were evaluated using linear swelling tests, cuttings dispersion tests, and bentonite inhibition tests. The inhibitory mechanism was investigated via X-ray diffraction measurements, adsorption measurements, and atomic force microscopy observations. The results indicated that Si-HPEI effectively inhibited the hydration and expansion of shale and exhibited excellent temperature resistance in comparison with HPEI and traditional shale inhibitors. The shale cuttings recovery in the case of Si-HPEI remained above 68% up to a hot rolling aging temperature of 140 °C, which demonstrated an excellent ability to inhibit hydration and dispersion that was significantly less affected by the hot rolling aging temperature than in the cases of other inhibitors. In addition, Si-HPEI inhibited the formation of a bentonite slurry more effectively at high temperatures. A mechanistic analysis showed that the siloxane groups present in the molecular chains of Si-HPEI caused strong and stable chemical adsorption of Si-HPEI on water-sensitive clay minerals, which thus hindered the penetration of water molecules and ultimately inhibited the hydration expansion and dispersion of water-sensitive clay minerals. In field application, Si-HPEI was successfully applied on Su 4-4HF well.