Patent EA-001186-B1 (EA)
Title: Non-toxic inexpensive drilling fluid
Inventor: VAN SLYKE DONALD C
IPC: E21B43/267
Filed: 1996-07-10
Abstract: 1. A drilling fluid comprising a base fluid; and at least one additive where the base fluid is a non-toxic, inexpensive, synthetic fluid, containing a paraffin mixture, synthesized, at least, partially in the Fischer-Tropsch process and having a pour point below 10 degree C, said additive is selected from the group consisting of emulsifiers, wetting agents, viscosifiers, weighting agents, fluid loss control agents, proppants for use in hydraulically fracturing subterranean formations, and particulate agents for use in forming a gravel pack, organophilous clays, inhibitor salts for shale swelling. 2. The drilling fluid of claim 1 where synthetic fluids having a pour point greater than about -30 degree C and a cetane index greater than about 60, and comprising at least about 95 weight percent hydrocarbons containing 11 or more carbon atoms, greater than 5 weight percent hydrocarbons containing 18 or more carbon atoms, at least about 50 weight percent isoparaffins, at least about 90 weight percent total paraffins, about 1 or less weight percent naphthenics, less than 0.1 volume percent aromatics, and at least 2 hydrocarbons containing a consecutive number of carbon atoms. 3. The drilling fluid of claim 1 where synthetic fluids having a pour point greater than about -30 degree C and a cetane index greater than about 60, and comprising at least about 95 weight percent hydrocarbons containing 10 or more carbon atoms and at least about 90 weight percent n-paraffins. 4. The drilling fluid of claim 3 comprises greater than 5 weight percent hydrocarbons containing 18 or more carbon atoms, at least about 90 weight percent total paraffins, less than 0.1 volume percent aromatics, and at least 2 hydrocarbons containing a consecutive number of carbon atoms, wherein the base fluid comprises at least about 95 weight percent hydrocarbons containing 11 or more carbon atoms. 5. The drilling fluid of claim 3 comprises greater than 5 weight percent hydrocarbons containing 18 or more carbon atoms, at least about 90 weight percent total paraffins, less than 0.1 volume percent aromatics, and at least 2 hydrocarbons containing a consecutive number of carbon atoms, wherein the base fluid comprises at least about 50 weight percent isoparaffins. 6. The drilling fluid of claim 3 comprises greater than 5 weight percent hydrocarbons containing 18 or more carbon atoms, at least about 90 weight percent total paraffins, less than 0.1 volume percent aromatics, and at least 2 hydrocarbons containing a consecutive number of carbon atoms, wherein the base fluid comprises about 1 or less weight percent naphthenics. 7. The drilling fluid of claim 3 comprises greater than 5 weight percent hydrocarbons containing 18 or more carbon atoms, at least about 90 weight percent total paraffins, less than 0.1 volume percent aromatics, and at least 2 hydrocarbons containing a consecutive number of carbon atoms. 8. The drilling fluid of any one of claims 1-7 where the base fluid has a flash point less than about 121.1 degree C. 9. The drilling fluid of any one of claims 1-8 where the base fluid has a viscosity at 40 degree C of less than about 10. 10. The drilling fluid of any one of claims 1-9 where the base fluid has an API gravity at 15 degree C greater than about 40 degree . 11. The drilling fluid of any one of claims 1-10 where the base fluid comprises less than 1 weight percent polar activator. 12. The drilling fluid of any one of claims 1-11 where the base fluid has an initial boiling point of at least about 160 degree C. 13. The drilling fluid of any one of claims 1-11 where the base fluid has a final boiling point from about 350 degree C to about 375 degree C. 14. The drilling fluid of any one of claims 1-11 where the base fluid comprises at least about 95 weight percent hydrocarbons containing 12 or more carbon atoms. 15. The drilling fluid of any one of claims 1-14 where the base fluid comprises greater than 10 weight percent hydrocarbons containing 18 or more carbon atoms. 16. The drilling fluid of any one of claims 1-15 where the base fluid comprises greater than 15 weight percent hydrocarbons containing 18 or more carbon atoms. 17. The drilling fluid of any one of claims 1-16 where the base fluid comprises at least about 91 weight percent total paraffins  18. The drilling fluid of any one of claims 1-17 where the base fluid comprises at least about 92 weight percent total paraffins. 19. The drilling fluid of any one of claims 1-18 where the base fluid comprises about 0.5 or less weight percent naphthenics, and less than 0.05 volume percent aromatics. 20. The drilling fluid of any one of claims 1-19 where the base fluid comprises less than 95 weight percent isoparaffin. 21. The drilling fluid of any one of claims 1-19 where the base fluid comprises less than 90 weight percent isoparaffin. 22. The drilling fluid of any one of claims 1-21 where the base fluid comprises at least 5 weight percent normal paraffin. 23. The drilling fluid of any one of claims 1-21 where the base fluid comprises at least 10 weight percent normal paraffin. 24. The drilling fluid of any one of claims 1-23 where the base fluid has a pour point less than about 6 degree C. 25. The drilling fluid of any one of claims 1-24 where the C11 or less isoparaffin content of the base fluid is composed of least about 90 weight percent mono-an poly-methyl isomers. 26. The drilling fluid of any one of claims 1-25 where the base fluid has a sulfur content of less than about 1 weight percent. 27. The drilling fluid of any one of claims 1-26 where the base fluid has a nitrogen content of less than about 1 weight percent. 28. The drilling fluid of any one of claims 1-27 where the base fluid has an oxygenate content of less than about 1 weight percent. 29. The drilling fluid of claim 1 where the base fluid comprises at least about 95 weight percent hydrocarbons containing 10 or more carbon atoms and at least about 90 weight percent n-paraffins. 30. The drilling fluid of any one of claims 1-29 where the base fluid further comprises water. 31. A method for drilling a borehole in a subterranean formation, the method comprising the steps of rotating a drill bit at the bottom of the borehole and introducing the drilling fluid of any one of claims 1-30 into the borehole to pick up drill cuttings and to carry at least a portion of the drill cuttings out of the borehole. 32. A method for treating a well, the method comprising the step of injecting the wellbore fluid of one of claims 1-30 into the well. 33. A method for treating a well, the method comprising the step of injecting a synthetic fluid into the well, the synthetic fluid having a pour point greater than about -30 degree C and a cetane index greater than 60, and comprising at least about 95 weight percent hydrocarbons containing 11 or more carbon atoms, greater than 5 weight percent hydrocarbons containing 18 or more carbon atoms, at least about 50 weight percent isoparaffins, at least about 90 weight percent total paraffins, about 1 or less weight percent naphthenics, less than 0.1 volume percent aromatics, and at least 2 hydrocarbons containing a consecutive number of carbon atoms. 34. A method for reducing friction between two surfaces in relative motion comprising the step of lubricating the surfaces with a lubricant selected from the group consisting of (A) fluids having (I) a pour point greater than about -30 degree C and a cetane index greater than 60, and comprising at least about 95 weight percent hydrocarbons containing 11 or more carbon atoms, greater than 5 weight percent hydrocarbons containing 18 or more carbon atoms, at least about 50 weight percent isoparaffins, (iv) at least about 90 weight percent total paraffins, about 1 or less weight percent naphthenics, less than 0.1 volume percent aromatics, and at least 2 hydrocarbons containing a consecutive number of carbon atoms.