Environmentally friendly bio-based additives in oil-based drilling fluids: Efficient synthesis, well-ordered self-assembly, exceptional ultra-high-temperature resistance, and excellent anti-settling properties

Skillfully designing weak interaction forces offers an effective approach to realize efficient and green oil exploration. In order to solve the problems such as the high-temperature instability of the drilling fluid, the easy sedimentation of barite in the system, and the pollution caused by the synthesized additives, novel bio-based rosin and tannin derivatives were simply and effectively synthesized by introducing nitrogen containing functional groups such as sulfonamide, amine and nitrile. The obtained compounds exhibited notable self-assembly capabilities in organic solvents and industrial white oil. The microstructures of supramolecular materials displayed micrometer-sized, crystal-like lamellar structures and rod-like three-dimensional network structures driven by hydrogen bonding and π-π stacking in an ordered and spontaneous manner. Notably, emulsion gels showed they were filled gels with enhanced elasticity and higher viscosity. Furthermore, the rosin-based derivatives added in oil-based drilling fluid could efficiently maintain the viscosity and emulsion stability. The maximum change in rotational viscosity was limited to 9 mPa·s after aging for 72 hours at 180 ℃. By modifying a number of non-covalent interactions, such as hydrogen bonding and π-π stacking, and especially covalent interactions coordination bonding, the composite additives made from rosin and tannin greatly enhanced the heavy spar's ultra-high temperature resistance and anti-settling properties. The emulsion breaking voltage reached more than 1800 V and settling factors was only 0.502 after hot rolling at 200 ℃ ultra-high temperature. The stability and sedimentation of heavy spar in oil-based drilling fluids at extremely high temperatures were successfully addressed by the environmentally friendly nitrogen-containing bio-based additives in oil-based drilling fluids. This allowed for the regular and stable operation of oil and gas exploration in extremely hot and deep wells.