Preparation and inhibition mechanism of bis-quaternary ammonium salt as shale inhibitor used in shale hydrocarbon production

Abstract

Countries around the world have shown great enthusiasm for shale gas and shale oil. Their production accounts for an increasing proportion in the output of unconventional oil and gas resources in the past several years. The clay minerals with large content in shale will be hydrated and swelled when encountering the external working fluid, thus causing water-sensitivity damage, which is the main problem that the efficient development of shale hydrocarbon resources reservoirs faces. Polyether amine is a kind of newly developed clay stabilizer in recent years, which exhibiting good shale inhibition performance. However, it was found in experiments that changing the pH value of polyether amine solution can strengthen or weaken its shale inhibition property. In response to this finding, the bis-quaternary ammonium salt was prepared with polyether amine as raw material. Its anti-swelling rate on sodium bentonite was 95.2%, which was 24.8%, 7.7%, 12.5% and 17.8% higher than that of the commonly used clay stabilizers such as tetramethyl ammonium chloride, poly epichlorohydrin-dimethylamine, poly dimethyl diallyl ammonium chloride, and polyether amine respectively. And bis-quaternary ammonium salt can effectively inhibit the hydration, swelling and dispersion of shale samples in water. The inhibition mechanism was studied systematically from the aspects of adsorption characteristics of bis-quaternary ammonium salt on clay surface, effect of bis-quaternary ammonium salt on clay hydration, and effect of bis-quaternary ammonium salt on clay swelling. This study provides an excellent shale inhibitor to reduce the permeability damage for efficient and sustainable development of shale gas and shale oil.