Patent EA-002815-B1 (EA)
Title: Polysaccharide-containing oil and gas well drilling and servicing fluids, method of increasing the thermal stability or decreasing the fluid loss of aqueous-base fluids
Inventor: HOUSE ROY F
IPC: C09K8/26
Filed: 1999-05-07
Abstract: 1. An aqueous-base drilling fluid for the drilling or servicing of oil or gas wells comprising an aqueous liquid having incorporated therein one or more polysaccharides in an amount to increase the low shear rate viscosity at low shear rates, an oligosaccharide mixture and a magnesium oxide, wherein the concentration of the oligosaccharide mixture is sufficient to increase the thermal stability or decrease the fluid loss of the fluid. 2. The fluid of Claim 1 wherein there is added at least about 0.7 kg/m<3> of the oligosaccharide mixture. 3. The fluid of Claim 1 wherein there is added from about 1.4 kg/m<3> to about 428 kg/m<3> of the oligosaccharide mixture. 4. The fluid of Claim 1 wherein there is added from about 1.4 kg/m<3> to about 57 kg/m<3> of the oligosaccharide mixture. 5. The fluid of Claim 1 which has a pH from about 7.5 to about 11.5. 6. The fluid of Claim 1 wherein the polysaccharide is a biopolymer which imparts an elevated low shear rate viscosity at low shear rate to the fluid as evidenced by the fluid having a shear thinning index greater than about 10. 7. The fluid of Claim 6 wherein the biopolymer is xanthan gum. 8. The fluid of Claim 6 wherein oligosaccharide mixture is selected from the group composed of arabinose, mannose, galactose, glucose, and xylose sugar units, the oligosaccharide mixture consisting of pentosans and hexosans containing from one to four combined sugar units. 9. An aqueous base fluid for the drilling or servicing of oil or gas wells wherein comprising an aqueous liquid having incorporated therein one or more polysaccharides in an amount to increase the low shear rate viscosity, increase the high shear rate viscosity, or decrease the fluid loss of the fluid, and an oligosaccharide mixture, wherein the polysaccharide is a biopolymer produced by the action of bacteria, fungi, or other microorganisms on a suitable substrate, and the concentration of the oligosaccharide mixture is sufficient to increase the thermal stability of the fluid. 10. The fluid of Claim 9 wherein there is added at least about 0.7 kg/m<3> of the oligosaccharide mixture. 11. The fluid of Claim 9 wherein there is added from about 1.4 kg/m<3>to about 57 kg/m<3>of the oligosaccharide mixture. 12 The fluid of Claim 9 wherein the biopolymer imparts an elevated low shear rate viscosity to the fluid as evidenced by the fluid having a shear thinning index greater than about 10. 13 The fluid of Claim 9 wherein the biopolymer is a xanthan gum. 14. The fluid of Claim 9 wherein the biopolymer is selected from the group consisting of xanthan gum, welan gum, gellan gum, schleroglucan gum, and succinoglycan gum. 15. The fluid of Claim 9 wherein oligosaccharide mixture is selected from the group composed of arabinose, mannose, galactose, glucose, and xylose sugar units, the oligosaccharide mixture consisting of pentosans and hexosans containing from one to four combined sugar units. 16. The method of enhancing the thermal stability or decreasing the fluid loss of an aqueous fluid comprising adding to the aqueous fluid at least one polysaecharide in an amount sufficient to provide the fluid the required characteristics wherein comprises incorporating into the aqueous-base fluid sufficient to increase the thermal stability of the fluid and sufficient to increase the thermal stability of the fluid, and wherein the polysaccharide is a biopolymer produced by the action of bacteria, fungi, or other microorganisms on a suitable substrate. 17. The method of Claim 16 wherein there is added at least about 0.7 kg/m<3> of the oligosaccharide mixture. 18. The fluid of Claim 16 wherein there is added from about 1.4 kg/m<3> to about 428 kg/m<3> of the oligosaccharide mixture. 19. The fluid of Claim 16 wherein there is added from about 1.4 kg/m<3> to about 57 kg/m<3> of the oligosaccharide mixture. 20. The fluid of Claim 16 wherein the biopolymer is selected from the group consisting of xanthan gum, welan gum, gellan gum, schleroglucan gum, and succinoglycan gum. 21. The fluid of Claim 16 wherein the biopolymer is a xanthan gum. 22. The fluid of Claim 16 wherein oligosaccharide mixture is selected from the group composed of arabinose, mannose, galactose, glucose, and xylose sugar units, the oligosaccharide mixture consisting of pentosans and hexosans containing from one to four combined sugar units.