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US 6,422,326 B1Granted
Aphron-containing well drilling and servicing fluids of enhanced stability
AssigneeActisystems, Inc.
InventorsTommy F. Brookey, Roy F. House
Life of this patent
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AssigneeActisystems, Inc.
InventorsTommy F. Brookey, Roy F. House
Estimating the term…
The invention provides a method and fluid for drilling or servicing a well in a subterranean formation, particularly 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 shear thinning index of the fluid is at least about 10, a surfactant, and aphrons, wherein the aphrons are preferably generated by the turbulence and pressure drop as the fluid exits the drill bit in the vicinity of the formation, the fluid having a low shear rate viscosity of at least 40,000 centipoise. The fluid additionally contains 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 Preferably the oligosaccharide mixture is the water soluble portion of thermally hydrolyzed lignocellulose.
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.
A well drilling and servicing fluid which can be continuously circulated in a borehole comprising an aqueous liquid, 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, a surfactant foaming agent, 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 aphrons which are generated by the encapsulation of gas in the fluid by a thin aqueous surfactant-containing shell wherein the surfactant molecules are so positioned that they produce an effective barrier against coalescence with adjacent aphrons, wherein the fluid has a low shear rate viscosity of at least 40,000 centipoise, and wherein the oligosaccharide mixture concentration is sufficient to enhance the thermal stability of the fluid as evidenced by the low shear rate viscosity of the fluid.
Dependencies are inferred from the claim text.