Managed pressure drilling with rig heave compensation

Patent metadata

Field	Value
Publication number	US-2016348452-A1
Application number	US-201615232316-A
Country	US
Kind code	A1
Filing date	Aug 9, 2016
Priority date	Mar 24, 2011
Publication date	Dec 1, 2016
Grant date	—

Abstract

A method for maintaining pressure in a wellbore drilled from a drilling platform floating on a body of water includes the steps of pumping fluid at a determined flow rate into a drill string disposed in a wellbore and measuring fluid pressure within a fluid discharge line of fluid returning from the wellbore. The fluid discharge line has a variable length corresponding to an elevation of the floating platform above the bottom of the body of water. The wellbore pressure is determined at a selected depth in the wellbore or at a selected position along a drilling riser or variable length portion of the fluid discharge line using known parameters/methods. The determined wellbore pressure is adjusted for changes in length of the fluid discharge line corresponding to changes in the elevation of the floating platform relative to the bottom of the body of water. A backpressure system may be operated to maintain the adjusted determined wellbore pressure at a selected (or set point) value by applying backpressure to the wellbore.

First claim

What is claimed is:

1 . A method for maintaining pressure in a wellbore drilled from a floating drilling platform, the method comprising the steps of:
pumping fluid at a determined flow rate into a drill string disposed in a wellbore; the drill string being suspended from a drilling platform floating on a body of water; measuring fluid pressure of fluid returning from the wellbore within a fluid discharge line, the fluid discharge line having a variable length portion arranged and designed to vary the length of the fluid discharge line to correspond to a change in elevation of the drilling platform above a bottom of the body of water; determining a wellbore pressure at a position selected from the group consisting of a selected depth position in the wellbore, a position along a drilling riser and a position along the variable length portion of the fluid discharge line, the wellbore pressure being determined using at least one of the determined flow rate, the measured fluid pressure, a hydraulics model or rheological properties of the fluid; and adjusting the determined wellbore pressure to account for changes in length of the fluid discharge line corresponding to changes in elevation of the drilling platform above the bottom of the body of water.

2 . The method of claim 1 wherein,
the step of adjusting the determined wellbore pressure comprises the steps of determining a change in length of the fluid discharge line and calculating a change in hydrostatic pressure of fluid in the fluid discharge line caused by the change in the length of the fluid discharge line.

3 . The method of claim 2 wherein,
the step of determining the change in length of the fluid discharge line is conducted using an elevation sensor disposed on the variable length portion of the fluid discharge line.

4 . The method of claim 1 further comprising the step of,
operating a backpressure system to maintain the adjusted determined wellbore pressure at a selected value.

5 . The method of claim 4 wherein,
the step of operating the backpressure system comprises the steps of measuring a fluid pressure in the wellbore proximate a blowout preventer and measuring a fluid pressure in the fluid discharge line at a position prior to a controllable orifice choke disposed therein.

6 . The method of claim 5 further comprising the step of,
determining time derivatives of the measured fluid pressure in the wellbore proximate the blowout preventer and the measured fluid pressure in the fluid discharge line at the position prior to the controllable orifice choke disposed therein.

7 . The method of claim 6 further comprising the step of,
operating the choke to maintain adjusted well bore pressure at a selected value, the choke operation being guided at least by the determined time derivatives.

8 . The method of claim 1 further comprising the steps of,
measuring fluid pressure in an elevatable portion of the fluid discharge line in at least two longitudinally spaced-apart positions at substantially a same elevation above the bottom of the body of water, and
determining at least one of a change in fluid viscosity, an entry of fluid into the wellbore from a subsurface formation or a loss of pumped fluid into the subsurface formation based on differences between the measured fluid pressure at the spaced-apart positions.

9 . The method of claim 8 further comprising the steps of,
measuring fluid pressure in the elevatable portion of the fluid discharge line at a third position at a different elevation than the at least two longitudinally spaced-apart positions, and
determining a change in fluid density of fluid being discharged from the wellbore based upon the measured fluid pressure from the third location and the measured fluid pressure from at least one of the at least two longitudinally spaced-apart positions.

10 . The method of claim 1 further comprising the steps of,
measuring fluid flow rate through the fluid discharge line, and
adjusting the measured fluid flow rate for changes in volume resulting from changes in the length of the fluid discharge line.

11 . The method of claim 1 further comprising the steps of,
measuring a fluid level in a tank receiving fluid from the wellbore, and
adjusting the measured fluid level for changes in volume resulting from changes in the length of the fluid discharge line.

12 . A method for controlling wellbore pressure while conducting drilling operations on a floating drilling platform, the method comprising the steps of:
pumping fluid through a drill string extended from a drilling platform into a wellbore drilled through a subsurface formation; measuring a flow rate of the pumped fluid; measuring a first fluid pressure in an annular space between the drill string and a wall of the wellbore at a position proximate a bottom of a body of water on which the drilling platform floats; measuring a second fluid pressure proximate a variable orifice flow restriction disposed in a fluid outlet from the annular space, the annular space arranged and designed to change length as a result of heave of the floating drilling platform; determining time derivatives of the first and second fluid pressures; and controlling the variable orifice flow restriction to maintain a selected pressure in the wellbore based upon at least the time derivatives of the first and second pressures.

Assignees

• Smith International

Inventors

• Reitsma Donald G
• Sehsah Ossama Ramzi
• Couturier Yawan

Classifications

• E21B21/001

  specially adapted for underwater drilling (dual gradient drilling E21B21/082) · CPC title

• E21B21/08 Primary

  Controlling or monitoring pressure or flow of drilling fluid, e.g. automatic filling of boreholes, automatic control of bottom pressure (valve arrangements therefor E21B21/10) · CPC title

• E21B21/003

  Means for stopping loss of drilling fluid (plastering the borehole wall E21B33/138) · CPC title

• E21B33/06

  Blow-out preventers {, i.e. apparatus closing around a drill pipe, e.g. annular blow-out preventers (rotating blow-out preventers E21B33/085)} · CPC title

• E21B47/06

  Measuring temperature or pressure · CPC title