Characterization of a novel aluminum-based shale stabilizer

A novel aluminum-based shale stabilizer used in drilling fluid composed of humic acid and aluminum (HA–Al) was synthesized. HA–Al is soluble under alkaline conditions, however, it can precipitate as microsphere pseudoboehmite and humic acid floc under neutral and acidic conditions or after the addition of Ca2+ and Mg2+ ions in solution. Due to these chemical features, HA–Al can dissolve in drilling fluid and precipitate in the shale pore throats when exposed to shale pore fluid to reduce pore pressure transmission, as is proven by SEM test. Comparing to other two samples of sodium silicate and poly alcohol, HA–Al is the best one to maintain wellbore stability due to its better properties of decreasing pore pressure transmission and increasing actual osmotic pressure of shale sample, as is indicated by pore pressure transmission and shale membrane efficiency tests.