| 摘要 |
A method for controlling drilling mud density at a location either at the seabed (or just above the seabed) or alternatively below the seabed of wells in deep water and ultra deep water applications are disclosed. The mud recirculation system may be used in conventional drill bit drilling operations or with drilling with casing operations. The present invention combines a base fluid of lesser density than the mud required at the wellhead to produce a diluted mud in the riser. By combining the appropriate quantities of drilling mud with base fluid, a riser mud density at or near the density of seawater may be achieved. The present invention also includes a wellhead injection device for attachment to the wellhead and for injecting the base fluid into the rising drilling mud at a location below the seabed. The riser charging lines are used to carry the low-density base fluid to the injection device for injection into the drilling mud below the seabed. The cuttings are brought to the surface with the diluted mud and separated in the usual manner. The diluted mud is then passed through a centrifuge system to separate the heavier drilling mud from the lighter base fluid.
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