Internal drilling riser centralizer

Abstract

The method of centralizing a rotating string within the bore of a subsea blowout preventer stack and a drilling riser comprising providing a multiplicity of rollers having a first position and a second position, when the rollers are in the first position the rollers defining a first circle which is proximately the size of the bore of the drilling riser, when the rollers are in the second position the rollers defining a second circle which is smaller than the first circle, and when the rollers are in the second position the rollers prevent the rotating string from contacting the bore of the subsea blowout preventer stack or the drilling riser proximate the rollers.

Description

TECHNICAL FIELD[0001]This invention relates to the general subject of centralizing the rotating pipe within a deepwater drilling riser to prevent key seating damage.CROSS-REFERENCE TO RELATED APPLICATIONS[0002]Not applicable.STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT[0003]Not applicableREFERENCE TO A “MICROFICHE APPENDIX”[0004]Not applicableBACKGROUND OF THE INVENTION[0005]The field of this invention is that of offshore floating drilling systems for drilling oil and gas wells in offshore waters. These have a blowout preventer stack landed on a wellhead on the ocean floor with a drilling riser attached to the top and continuing up to a vessel floating at the ocean surface.[0006]At the connection of the riser to the top of the blowout preventer stack there is typically a flex joint to keep the riser from being overstressed due to surface vessel movement, side forces from currents, or when the riser is allowed to be momentarily slack. An example of this type flex j...

AI Technical Summary

Benefits of technology

[0011]The object of this invention is to provide a method to centralize an rotating drill string within the bore of a drilling riser and blowout preventer stack to prevent wear damage or key seating to the bore of the drilling riser or blowout preventer stack.

Problems solved by technology

A key seat in the bore of the drilling riser or blowout preventer stack can literally wear all the way through the metal.

Unfortunately a hole to the seawater will cause substantial pollution of the drilling mud into the seawater and loss of drilling mud pressure to control the pressure in the well.

This loss of drill mud pressure will allow oil and gas to enter the well and require that the well be closed in or a blowout will occur.

In some cases such as drilling in the water off the coast of Alaska tidal movement of the vessels in relatively shallow water cause substantial deflection.

This inflicts substantial wear on the drilling components which simply must be withstood.

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