| 摘要 |
A method of preventing drilling fluid overflow when adding or removing drill pipe sections to or from a drill string disposed in a well bore comprising the steps of introducing gasified drilling fluid into the drill string until a predetermined volume thereof is introduced therein at a predetermined pressure thereby displacing non-gasified drilling fluid in the drill string downwardly and displacing drilling fluid from the annulus, releasing the pressurized gasified drilling fluid from the drill string whereby the gasified drilling fluid flows upwardly through the drill string and drilling fluid and gas are removed therefrom whereby the resulting equalized level of drilling fluid in the drill string is below the level at which the drill pipe sections are added to or removed from the drill string and then adding or removing drill pipe sections to or from the drill string.
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