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US 6,745,857 B2Granted
Method of drilling sub-sea oil and gas production wells
AssigneeNational Oilwell Norway AS
InventorJon G. Gjedebo
Life of this patent
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Abstract
A method of drilling sub-sea oil and gas production wells in which a liquid hydrocarbon substance, such as a natural gas liquid, is injected into the drilling mud supplied to the well in order to reduce the mud density. The method of the present invention enables reduction and control of the hydraulic pressure of the drilling mud while drilling production wells in deep water, thereby to require fewer casing runs which eventually yields better oil productivity.
Claims18
A method of reducing the density of mud supplied to a well during drilling for the production of oil and gas from a subsea reservoir comprising:
- injecting a liquid hydrocarbon substance which is lighter than the mud into the flow of mud supplied to the well while drilling;
- and
- adjusting at least one of the injection rate and the point of injection of the liquid hydrocarbon substance into the mud flow to reduce the density of the mud and reach a desired pressure gradient in the mud flow.
Dependencies are inferred from the claim text.