RETURN LINE MOUNTED PUMP FOR RISERLESS MUD RETURN SYSTEM

• US 20090032301A1
• Filed: 08/02/2007
• Published: 02/05/2009
• Est. Priority Date: 08/02/2007
• Status: Active Grant

• Current Assignee: Enhanced Drilling, Inc.
• Original Assignee: AGR Subsea, Inc.
• Inventors: Smith, David E., Hufthammer, Harald, Stave, Roger, Rolland, Nils Lennart
• Granted Patent: US 7,913,764 B2
• Time in Patent Office: Days
• US Class Current: 175/7
• CPC Class Codes: E21B 21/001 specially adapted for underwater drilling dual gradient drilling E21B21/082
• CPC Class Codes: E21B 21/10 Valve arrangements in drilling-fluid circulation systems

Abstract

Systems and methods for drilling a well bore in a subsea formation from an offshore structure positioned on a water surface with a drill string that is suspended from the structure and includes a bottom hole assembly adapted to form a top hole portion of the well bore. A drilling fluid source on the offshore structure supplies drilling fluid through the drill string to the bottom hole assembly where the drilling fluid exits from the bottom hole assembly during drilling and returns up the well bore. A suction module is disposed at the sea floor and collects the drilling fluid emerging from the well bore. A pump module is disposed on a return line, which is in fluid communication with the suction module, at a position below the water surface and above the sea floor. The pump module is operable to receive drilling fluid from the suction module and pump the drilling fluid through the return pipe to the same offshore structure or a different offshore structure

Claims

1. A system for use in drilling a well bore in an offshore location having a water surface and a sea floor, comprising:

a first offshore structure at the water surface;

a drill string suspended from said first offshore structure, said drill string coupled to a bottom hole assembly adapted to form a top hole portion of the well bore;

a drilling fluid source for supplying drilling fluid through said drill string to the bottom hole assembly, said drilling fluid exiting from the bottom hole assembly during drilling and returning up the well bore;

a suction module for collecting the drilling fluid emerging from the well bore;

a return line in fluid communication with said suction module;

a second offshore structure; and

a pump module disposed on said return line at a position below the water surface and above the sea floor, wherein said pump module is operable to receive drilling fluid from said suction module and pump the drilling fluid through said return pipe to said second offshore structure.

2. The system of claim 1, further comprising a docking joint coupled to said return line, wherein said pump module is releasably coupled to said docking joint.

3. The system of claim 2, wherein said docking joint comprises isolation valves that are operable to isolate said pump module from said return line.

4. The system of claim 3, wherein said docking joint further comprises:

an inlet line operable to couple an inlet of said pump module to said docking joint;

an outlet line operable to couple an outlet of said pump module to said docking joint, wherein both said inlet line and said outlet line have an isolation valve disposed therein.

5. The system of claim 4, wherein said pump module is operable to pump drilling fluid from the inlet line to the outlet line when the isolation valves are open.

6. The system of claim 2, wherein said pump module comprises a frame that partially surrounds said return line and is operable to engage said docking joint.

7. The system of claim 6, wherein said docking joint comprises a helix that aligns said pump module with said docking joint.

8. The system of claim 2, wherein said pump module further comprises:

an inlet operable to couple to said docking joint;

a pump in fluid communication with said inlet; and

an outlet in fluid communication with said pump and operable to couple to said docking joint.

9. The system of claim 8, wherein said pump module comprises a plurality of pumps in fluid communication with said inlet and said outlet.

10. The system of claim 8, wherein the pump is one of a group consisting of a disc pump and a centrifugal pump.

11. The system of claim 1, wherein said first offshore structure and said second offshore structure are the same structure.

12. The system of claim 1, wherein said return line is rigid

28. The system of claim 1, wherein said return line is rigid.

13. A method for drilling offshore, comprising:

driving a bit to form a top hole portion of a well bore in a subsea formation, said bit being coupled to a drill string;

injecting a drilling fluid into the drill string from a first offshore structure located at a water surface;

collecting the drilling fluid with a suction module after the drilling fluid passes through the drill string; and

lifting the drilling fluid from the suction module via a return line using a pump module disposed on the return line at a position below the water surface and above a sea floor.

14. The method of claim 13, further comprising isolating the pump module from the return line.

15. The method of claim 13, further comprising retrieving the pump module to the first offshore structure without retrieving the return line.

16. The method of claim 13, wherein the pump module is coupled to the return line after the return line has been installed.

17. The method of claim 13, wherein the return line comprises a docking joint that provides fluid communication between the pump module and the return line.

18. The method of claim 13, wherein said return line is rigid.

19. The method of claim 13, further comprising retrieving the pump module to a second offshore structure without retrieving the return line.

20. A system for processing drilling fluid in underwater operations comprising:

a suction module for mounting over a wellbore in sealed relation to the surrounding seawater to prevent leakage of drilling fluid from the wellbore;

a first offshore structure operable to supply a drilling fluid to a drill string disposed in the wellbore;

at least one pump module coupled to said suction module to effect a differential pressure therein for pumping drilling fluid from said suction module upwardly to a second offshore structure, wherein said pump module is positioned above the sea floor.

21. The system of claim 20, further comprising a docking joint coupled a return line, wherein said pump module is releasably coupled to said docking joint.

22. The system of claim 21, wherein said pump module comprises a frame that partially surrounds said return line and is operable to engage said docking joint.

23. The system of claim 22, wherein said docking joint comprises a helix that aligns said pump module with said docking joint.

24. The system of claim 21, wherein said pump module further comprises:

an inlet operable to couple to said docking joint;

a pump in fluid communication with said inlet; and

an outlet in fluid communication with said pump and operable to couple to said docking joint.

25. The method of claim 21, further comprising actuating isolation valves to cease lifting the drilling fluid.

26. The method of claim 25, further comprising disengaging the pump module from the docking joint without dismantling the return line.

27. The system of claim 20, wherein the first offshore structure and the second offshore structure are the same offshore structures.