Method and apparatus for varying the density of drilling fluids in deep water oil drilling applications
First Claim
1. A method employed at the surface for varying the density of fluid in a subsea riser of a drilling system comprising the steps of:
- a. introducing at the surface a first fluid having a first density into a drill tube, such fluid being released from the drill tube and into the riser;
b. introducing at the surface a second fluid having a second density into the riser, for producing a combination fluid having a density that is defined by a selected ratio of the first fluid and the second fluid, such combination fluid rising to the surface; and
c. separating the combination fluid after it has risen to the surface into the first fluid and the second fluid and storing same in separate storage units at the surface.
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Accused Products
Abstract
A method and apparatus for controlling drilling mud density at or near the seabed of wells in deep water and ultra deep-water applications 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. No additional hardware is required below the surface. The riser charging lines are used to inject the low-density base fluid at or near the BOP stack on 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.
91 Citations
19 Claims
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1. A method employed at the surface for varying the density of fluid in a subsea riser of a drilling system comprising the steps of:
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a. introducing at the surface a first fluid having a first density into a drill tube, such fluid being released from the drill tube and into the riser;
b. introducing at the surface a second fluid having a second density into the riser, for producing a combination fluid having a density that is defined by a selected ratio of the first fluid and the second fluid, such combination fluid rising to the surface; and
c. separating the combination fluid after it has risen to the surface into the first fluid and the second fluid and storing same in separate storage units at the surface. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13)
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14. An apparatus for generating at the surface a riser fluid for use in a subsea well, said riser fluid having a density different from the drilling fluid, comprising:
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a. a drilling platform;
b. a wellhead on the seabed;
c. a drilling string connecting the platform to the well and including a drillstem, drill tube and casing for defining the riser;
d. charging lines associated with the riser;
e. a source of drilling fluid on the platform, said drilling fluid of a first density for providing drilling fluid to be introduced into the drill tube; and
f. a source of additional fluid on the platform, said additional fluid of a second density for providing said additional fluid to be introduced into the charging lines, whereby the first fluid and the second fluid are combined in the riser for producing a combined fluid having a density different from the density of the drilling fluid; and
g. a separator on the platform for separating the combined fluid into its components as the combined fluid is discharged from the riser. - View Dependent Claims (15, 16, 17, 18, 19)
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Specification