A biomimetic drilling fluid for wellbore strengthening

Based on biomimetic technology, wellbore strengthener GBFS-1 and shale inhibitor YZFS-1 were synthesized imitating the mussel protein which has super adhesion. A new drilling fluid system centering on the two biomimetic agents was designed and prepared in order to enhance the strength of shale rocks near wellbore and maintain wellbore stability. Various inhibition evaluation tests show that YZFS-1 can strongly inhibit clay hydrated swelling and the resulting shale dispersion, due to the adsorption and self-polymerization of YZFS-1 molecules in the interlayer of clay. Besides the ability of controlling fluid loss, GBFS-1 can also adhere to shale rock, produce dense and water impermeable biomimetic shell that has relative strong cohesion strength after spontaneous cure. The shear strength tests show that the shear strength of two shale pieces glued together by the biomimetic shell in aqueous environment is obviously stronger than glued by several commonly-used binders. Through compatibility evaluation and dosage optimization of the additives, the formula of biomimetic drilling fluid was established, and its performance was evaluated and compared with another anti-caving drilling fluid. The results show the biomimetic drilling fluid is better in all basic performances than the anti-caving drilling fluid on the whole, and can effectively inhibit shale swelling and dispersion.