DRILLING FLUID

摘要

1. A water-based drilling fluid comprising as additive a reaction product of a linear polyhydroxyalkane based on a monosaccharide.and alkylene oxide. 2. A drilling fluid according to Claim 1 or 2, wherein the polyhydroxyalkane comprises, erythreitol, threitol, ribitol, sorbitol, mannitol or galactitol. 3. A drilling fluid according to Claim 1, 2 or 3, the alkylene oxide comprises ethylene oxide (EO). propylene oxide (PO) and/or buylene oxide (BO). 4. A drilling fluid according to any one of the preceding Claims, wherein the additive comprises up to 30 alkylene oxide units per polyhydroxyalkane molecule. 5. A drilling fluid according to any one of the preceding Claims, wherein the additive is selected from a group comprising Sorbitol + 18EO, Sorbitol + 9PO, Sorbitol + 4EO + 6BO, Sorbitol + 6EO + 6BO, Sorbitol + 6BO. 6. A drilling fluid according to any one of the preceding Claims, wherein the additive is present in an amount in the range 1 to 10% by weight. 7. A drilling fluid according to Claim 6, wherein the additive is present in an amount in the range 1 to 5% by weight. 8. A drilling fluid according to any one of the preceding Claims, comprising aqueous medium of fresh water, salt water, other salt solutions or mixtures thereof. 9. A drilling fluid according to any one of the preceding Claims, comprising one or more further additives. 10. A drilling fluid according to Claim 9, comprising potassium salt additive. 11. A drilling fluid according to Claim 10, wherein the potassium salt comprises potassium chloride.