Importance

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Abstract

The invention provides a method and fluid for drilling or servicing a well in a subterranean formation containing lost circulation zones or depleted, low pressure reservoirs. A method of decreasing the density of the fluid circulated in a borehole, decreasing the invasion of fluid into formations contacted by the fluid, or decreasing the lost circulation potential of the fluid is provided by using as the fluid an aqueous liquid having dispersed therein a polymer which increases the low shear rate viscosity of the fluid to the extent that the thixotropic index of the fluid is at least about 10 and a surfactant, and wherein the fluid contains aphrons preferably generated by the turbulence and pressure drop as the fluid exits the drill bit in the vicinity of the formation.

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First Claim