Saikosaponin improves the anti-collapse performance of water-based drilling fluids for shale gas

Abstract

Shale gas formations often exhibit well-wall instability during drilling, particularly when using water-based drilling fluids, due to the high water sensitivity of the rock and the propensity for fractures to collapse. In this paper, our study delved into the impacts of saikosaponins (SS) on enhancing the anti-collapse efficacy of water-based drilling fluids for shale gas. Our experimental findings revealed that the incorporation of 3% SS into the water-based drilling fluid led to a 71.7% reduction in bentonite swelling and a significant increase in shale rolling recovery to 98.9%. Furthermore, the water-based drilling fluid enhanced with SS could maintain a shale strength at 96.8% of its original value. Moreover, the inclusion of SS elevated the dynamic shear force of the drilling fluid, bolstered its chip-carrying capacity, and reduced its filtration loss. This is attributed to SS's ability to adhere to the shale surface via hydrogen bonding, resulting in the formation of a hydrophobic film that impedes water molecules from infiltrating the shale. Simultaneously, SS's unique multi-hydroxyl structure endowed it with robust adhesion, forming a reinforcing layer on the shale surface to fortify the wall of the well. Consequently, SS effectively heightens the anti-collapse capabilities of drilling fluids. Moreover, SS as a plant-extracted ingredient is environmentally friendly and holds immense promise for the eco-conscious advancement of shale gas.