Drilling fluid and method for drilling in coal-containing formations
First Claim
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1. 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.
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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.
25 Citations
35 Claims
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1. A method for drilling in a coal containing formation, the method comprising:
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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. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16)
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17. A method for drilling a wellbore, the method comprising:
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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. - View Dependent Claims (18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28)
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29. A method for drilling a wellbore, the method comprising:
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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. - View Dependent Claims (30, 31, 32, 33, 34, 35)
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Specification