Partially hydrophobized hyperbranched polyglycerols as non-ionic reactive shale inhibitors for water-based drilling fluids

Abstract The oil and gas industry demands drilling fluids that would be able to minimize the wellbore instability faced during the drilling of reactive shales. In this work we describe the synthesis of hydrophobized hyperbranched polyglycerols (HPG) with unique design and properties to be used as non-ionic reactive shale inhibitors. In association with KCl, HPG showed a superior performance in comparison with unmodified hyperbranched polyglycerol and with the commercial clay reactivity inhibitors PEG400 and PDADMAC. Intact cuttings recoveries were around 80%. The proposed inhibition mechanism suggests the formation of a complex between HPGs and K + ions and its penetration into the clay interlayer spacing to minimize the shale-water interactions and remove water molecules present in the clay galleries. In addition, these aggregates formed by the amphiphilic structures would cause obstruction of the clay minerals pore throats, thereby making it even more difficult for the penetration of water molecules.