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US 9,850,416 B2Granted
Drilling fluid and method for drilling in coal-containing formations
AssigneeCanadian Energy Services L.P.
InventorCarl Keith Smith
Life of this patent
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Abstract
A drilling fluid and method for drilling in a coal containing formation with a mixed metal-viscosified drilling fluid including at least 0.05% calcium sulfate.
Claims35
A method for drilling in a coal containing formation, the method comprising:
- providing a mixed metal-viscosified drilling fluid including clay, a mixed metal-viscosifier and at least 0.05% (w/v) calcium sulfate;
- circulating the drilling fluid through the well;
- and
- drilling into the coal containing formation,
- provided that the calcium sulfate is added to protect an electrostatic interaction between the clay and the mixed metal-viscosifier, thereby maintaining the viscosity of the drilling fluid at a yield point of greater than 10 Pa.
2 more elements
A method for drilling a wellbore, the method comprising:
- providing a mixed metal-viscosified drilling fluid including clay and a mixed metal-viscosifier;
- monitoring rheology of the mixed metal-viscosified drilling fluid;
- and,
- adding calcium sulfate in an amount of at least 0.05% (w/v) to the mixed metal-viscosified drilling fluid to avoid adverse rheological changes, provided that the calcium sulfate is added to protect an electrostatic interaction between the clay and the mixed metal-viscosifier, thereby maintaining the viscosity of the drilling fluid at a yield point of greater than 10 Pa.
1 more element
A method for drilling a wellbore, the method comprising:
- providing a drilling fluid, the drilling fluid being aqueous and clay-based including 15 to 50 kg/m3 clay and a mixed metal viscosifier at a weight ratio of 1:8 to 1:12 viscosifier to clay;
- monitoring rheology of the drilling fluid;
- and
- adding to the drilling fluid calcium sulfate at a weight ratio of 1:2.5 to 1:90 calcium sulfate to clay to avoid adverse rheological changes,
- provided that the calcium sulfate is added to protect an electrostatic interaction between the clay and the mixed metal-viscosifier, thereby maintaining the viscosity of the drilling fluid at a yield point of greater than 10 Pa.
2 more elements
Dependencies are inferred from the claim text.