The Effect of Various Polymers and Salts on Borehole and Cutting Stability in Water-Base Shale Drilling Fluids

Abstract

ABSTRACT Shale hydration tests have been carried out at confining pressures, ranging from 0 to 350 bar. The results show a high swelling pressure, without significant expansion, at high confining pressure and a large expansion without swelling pressure in the unconfined situation. It is also shown that different salts have different effects on swelling and that the effect of mud additives other than salts is negligible. The test results indicate that, for the shales tested, water structure modification and not ion exchange is principally responsible for the inhibitive effect of salts. In addition, borehole erosion and cutting disintegration tests have been carried out. The results of these tests show a significant effect of various polymeric mud additives in terms of cohesion.