Method of handling a gas influx in a riser

• US 9,605,502 B2
• Filed: 04/10/2013
• Issued: 03/28/2017
• Est. Priority Date: 04/11/2012
• Status: Active Grant

• Current Assignee: Grant Prideco Incorporated (NOV, Inc.)
• Original Assignee: Managed Pressure Operations Pte. Ltd. (Akastor ASA)
• Inventors: Leuchtenberg, Christian, Chandra, Michael, Goncalves, Carlos
• Primary Examiner(s): Buck, Matthew R
• Assistant Examiner(s): Wood, Douglas S
• Application Number:
  US14/394,038
• Publication Number:
  US 20150068758A1
• Time in Patent Office: 1,448 Days
• Field of Search: None
• US Class Current: 1/1
• CPC Class Codes: E21B 17/01 Risers
• CPC Class Codes: E21B 21/001 specially adapted for underwater drilling dual gradient drilling E21B21/082
• CPC Class Codes: E21B 21/08 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 Class Codes: E21B 33/06 Blow-out preventers , i.e. apparatus closing around a drill pipe, e.g. annular blow-out preventers rotating blow-out preventers E21B33/085
• CPC Class Codes: E21B 34/025 Chokes or valves in wellheads and sub-sea wellheads for variably regulating fluid flow
• CPC Class Codes: E21B 44/00 Automatic control systems specially adapted for drilling operations, i.e. self-operating systems which function to carry out or modify a drilling operation without intervention of a human operator, e.g. computer-controlled drilling systems; Systems specially adapted for monitoring a plurality of drilling variables or conditions
• CPC Class Codes: E21B 47/06 Measuring temperature or pressure

Abstract

A method of operating a system for handling an influx of gas into a marine riser during the drilling of a well bore includes the steps of operating a first riser closure apparatus to close the riser at a first point above a flow spool provided in the riser, there being a riser gas handling line extending from the riser at the flow spool to a riser gas handling manifold, operating a second riser closure apparatus to close the riser at a second point below the flow spool, pumping fluid into an inlet line which extends into the riser at a point above the second point but below the flow spool, and operating a choke provided in the riser gas handling manifold to maintain the pressure in the inlet line or the riser at a substantially constant pressure.

Claims

1. A method of operating a system for handling an influx of gas into a marine riser during the drilling of a well bore, the method including the steps of:

operating a first riser closure apparatus to close the riser at a first point above a flow spool provided in the riser, there being a riser gas handling line extending from the riser at the flow spool to a riser gas handling manifold;

operating a second riser closure apparatus to close the riser at a second point below the flow spool so as to form a volume in the riser between the first riser closure apparatus and the second riser closure apparatus, and to shut-in the well bore so that a flow of fluid from the well bore below the second riser closure apparatus into the volume between the first riser closure apparatus and the second riser closure apparatus does not occur;

pumping fluid into an inlet line that extends into the riser at a point above the second point but below the flow spool; and

operating a choke provided in the riser gas handling manifold to maintain the pressure in the inlet line or the riser at a substantially constant pressure,

wherein,

the pumping of the fluid into the inlet line that extends into the riser at the point above the second point but below the flow spool, and the operating of the choke provided in the riser gas handling manifold to maintain the pressure in the inlet line or the riser at the substantially constant pressure are each performed when the first riser closure apparatus has closed the riser at the first point above the flow spool, and the second riser closure apparatus has closed the riser at the second point below the flow spool to shut-in the well bore so that a flow of fluid from the well bore below the second riser closure apparatus into the volume between the first riser closure apparatus and the second riser closure apparatus does not occur.

2. The method according to claim 1, wherein the first riser closure apparatus is an annular blow out preventer.

3. The method according to claim 1, wherein the step of operating the first riser closure apparatus further comprises the step of operating the first riser closure apparatus so that the first riser closure apparatus seals around a drill string extending down the riser.

4. The method according to claim 1, wherein the second riser closure apparatus is a blow out preventer in a subsea blowout preventer stack.

5. The method according to claim 1, wherein the step of operating the second riser closure further apparatus comprises the step of operating the second riser closure device so that the second riser closure device seals around a drill string extending down the riser.

6. The method according to claim 1, wherein the first point is below a slip joint provided in the riser.

7. The method according to claim 1, wherein the second point is just above a well head.

8. The method according to claim 1, wherein the riser gas handling manifold is located on a drilling rig from which the riser is suspended.

9. The method according to claim 1, wherein the inlet line comprises a booster line that extends from a pump located on a drilling rig from which the riser is suspended, to a portion of the riser just above the uppermost blowout preventer in a subsea blowout preventer stack at the lowermost end of the riser.

10. The method according to claim 1, further including the step of opening a riser gas handling line isolation valve that is operable to permit or substantially prevent flow of fluid along the riser gas handling line after operating the first riser closure apparatus.

11. The method according to claim 10, wherein the step of opening the riser gas handling line isolation valve is carried out before operating the second riser closure apparatus.

12. The method according to claim 1, further including the step of ceasing the pumping of fluid into the riser prior to the step of operating the second riser closure apparatus.

13. The method according to claim 12, wherein the step of ceasing the pumping of fluid into the riser is carried out after the step of operating the first riser closure apparatus.

14. The method according claim 1, wherein the rate of pumping of fluid into the riser via the inlet line is increased to a predetermined level, and, at the same time, the choke is operated to maintain a substantially constant pressure in the riser.

15. The method according to claim 14, wherein the step of operating the choke to maintain a substantially constant pressure in the inlet line is commenced once the rate of pumping of fluid into the riser via the inlet line has reached the predetermined value.

16. The method according to claim 1, wherein there is a second riser gas handling line extending from the riser at the flow spool to the riser gas handling manifold.

17. The method according to claim 16, further including the step of opening a second riser gas handling line isolation valve that is operable to permit or substantially prevent flow of fluid along the second riser gas handling line after operating the first riser closure apparatus.

18. The method according to claim 1, wherein the step of operating the choke provided in the riser gas handling manifold to maintain the pressure in the inlet line at a substantially constant pressure further comprises the steps of using a pressure sensor to measure the fluid pressure in the inlet line, and transmitting an inlet pressure signal representative of the fluid pressure in the inlet line to a controller, the controller being programmed to operate the choke in accordance with the inlet pressure signal.

19. The method according to claim 1, further including the steps of monitoring the rate of pumping of fluid into the inlet line, and, if this rate of pumping deviates from a predetermined value or range of values, using a pressure sensor to measure the fluid pressure in the riser, and operating the choke to maintain the pressure in the riser at a substantially constant pressure.

20. The method according to claim 19, further including the steps of returning to operating the choke to maintain the pressure in the inlet line at a substantially constant pressure if the pumping rate returns to the predetermined value or range of values.

21. The method according to claim 1, further including the step of directing fluid discharged from the riser gas handling manifold to a mud gas separator located on the floor of a drilling rig from which the riser is suspended.

22. The method according to claim 21, wherein the fluid discharged from the riser gas handling manifold is directed to a diverter before being directed to the mud gas separator, the diverter acting to separate a proportion of entrained gas from the remainder of the fluid.

23. The method according to claim 22, wherein all the fluid from the diverter is directed to the mud gas separator.

24. The method according to claim 23, wherein the mud gas separator is provided with baffle plates in a lowermost end thereof.

25. The method according to claim 21, further comprising the step of directing the denser fluids from the mud gas separator to a solids processing apparatus.

26. The method according to claim 21, further comprising the step of directing the lighter fluid from the mud gas separator to a vent line that exhausts to atmosphere.

27. The method according to claim 21, wherein the mud gas separator is provided with a drain at a lowermost end thereof, the drain having a liquid seal to retain pressure in the mud gas separator.

28. The method according to claim 21, further comprising the step of pumping extra fluid into the mud gas separator, in addition to the fluid entering from the riser gas handling manifold.