Patent ID: 6422326
Filing Date: 2002-07-23
Classification: C09K,E21B

Abstract:
In a process of drilling a well wherein a drilling fluid is circulated in a borehole, the drilling fluid comprising an aqueous liquid having dispersed therein a polymer which increases the low shear rate viscosity of the fluid to the extent that the shear thinning index of the fluid is at least about 10 and the low shear rate viscosity is at least 40,000 centipoise, the method of bridging and sealing subterranean formations contacted by the fluid, or decreasing the lost circulation potential of the fluid, which comprises adding to the fluid a surfactant and an oligosaccharide mixture composed of pentosans and/or hexosans containing from one to about 10 combined sugar units selected from the group consisting of arabinose, mannose, galactose, glucose, xylose, cellobiose, and mixtures thereof, and thereafter generating aphrons in the fluid.