Subsea mud pump and control system

• US 6,505,691 B2
• Filed: 08/06/2001
• Issued: 01/14/2003
• Est. Priority Date: 03/27/1998
• Status: Expired due to Term

• Current Assignee: Hydril USA Manufacturing LLC (GE Aerospace)
• Original Assignee: Hydril Company L P (General Electric Company)
• Inventors: Judge, Robert A., Peterman, Charles P.
• Primary Examiner(s): SCHOEPPEL, ROGER J
• Application Number:
  US09/923,287
• Publication Number:
  US 20020066596A1
• Time in Patent Office: 526 Days
• Field of Search: 175/70, 175/7, 175/213, 175/214, 175/216-218, 166/350, 166/359, 166/367, 166/84.3, 166/84.4, 166/84.5, 138/26, 138/30, 138/31, 137/565.13, 137/565.16, 137/565.19, 220/720, 220/721, 251/129.01, 251/282, 251/324, 251/331, 417/390, 417/392, 417/395, 417/401, 417/505, 417/521, 417/533
• US Class Current: 175/70
• CPC Class Codes: E21B 21/001 specially adapted for underwater drilling dual gradient drilling E21B21/082
• CPC Class Codes: E21B 21/01 Arrangements for handling drilling fluids or cuttings outside the borehole, e.g. mud boxes
• 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 21/085 Underbalanced techniques, i.e. where borehole fluid pressure is below formation pressure
• CPC Class Codes: E21B 33/085 Rotatable packing means, e.g. rotating blow-out preventers
• CPC Class Codes: F04B 19/003 free-piston type pumps
• CPC Class Codes: F04B 43/06 Pumps having fluid drive
• CPC Class Codes: Y10T 137/86027 Electric
• CPC Class Codes: Y10T 137/86059 Hydraulic power unit

Abstract

The invention is a subsea pump that includes pumping elements, each pumping element including a pressure vessel with a first and a second chamber therein and a separating member disposed between the first and second chambers. The first and second chambers are hydraulically connected to receive and discharge a hydraulic fluid and a drilling fluid, respectively. The separating member moves within the pressure vessel in response to a pressure differential between the first and second chambers. A hydraulic power supply is arranged to pump the hydraulic fluid to the first chamber of each of the pumping elements. A valve assembly is hydraulically coupled to the first chambers of the plurality of pumping elements and to the hydraulic power supply. Volume measurement devices are arranged to measure volumes of each of the first chambers and the second chambers. A valve controller is connected to the valve assembly and to the volume measurement devices, and the valve controller is arranged to control a rate and timing of a flow of the hydraulic fluid into the first chambers and a rate and timing of a flow of the hydraulic fluid out of the first chambers in response to the volume measurements. The valve controller is configured to maintain at least one of a substantially constant pump inlet pressure, a substantially constant pump discharge pressure, and a substantially constant total volume of the first chambers.

Claims

1. A subsea pump comprising:

a plurality of pumping elements, each pumping element comprising a pressure vessel with a first and a second chamber therein and a separating member disposed between the first and second chambers, the first and second chambers being hydraulically coupled to receive and discharge a hydraulic fluid and a drilling fluid, respectively, wherein the separating member moves within the pressure vessel in response to a pressure differential between the first and second chambers;

a hydraulic power supply adapted to pump the hydraulic fluid to the first chamber of each of the pumping elements;

a valve assembly hydraulically coupled to the first chambers of the plurality of pumping elements and to the hydraulic power supply;

volume measurement devices adapted to measure volumes of each of at least one of the first and second chambers; and

a valve controller operatively coupled to the valve assembly and to the volume measurement devices, the valve controller adapted to control a rate and timing of application of the hydraulic fluid to each of the first chambers and a timing of discharge of hydraulic fluid therefrom in response to the measurements of volume so as to maintain at least one of a substantially constant pump inlet pressure, a substantially constant pump discharge pressure, and a substantially constant total volume of the first chambers.

2. The subsea pump of claim 1, wherein the valve assembly comprises a dump valve adapted to control a pressure of the hydraulic fluid, the pressure of the hydraulic fluid adjustable to select the rate of application.

3. The subsea pump of claim 1, further comprising at least one sequencing device operatively coupled to the volume measurement devices and the valve assembly, the at least one sequencing device adapted to determine a fill status of the first and second chambers from the volume measurements and to operate inlet and outlet valves connected to the first chambers and second chambers at selected times so as to enable filling and emptying of the first and second chambers with hydraulic fluid and drilling fluid, respectively.

4. The subsea pump of claim 1, wherein the plurality of pumping elements comprise diaphragm pumps.

5. The subsea pump of claim 4, wherein each separating member comprises a rolling diaphragm.

6. The subsea pump of claim 1, wherein each separating member comprises a piston.

7. The subsea pump of claim 1, wherein the volume measurement devices comprise position measuring sensors operatively coupled to each of the separating members.

8. The subsea pump of claim 7, wherein the position measuring sensors comprise magnetostrictive transducers.

9. The subsea pump of claim 7, wherein the volume measurement devices comprise an integrator.

10. The subsea pump of claim 1, wherein the hydraulic power supply comprises a submersible pump disposed proximate the subsea pump on the seafloor.

11. The subsea pump of claim 1, further comprising compression valves hydraulically coupled to the hydraulic power supply and to each of the first chambers, the valve controller being operatively coupled to the compression valves and adapted to open the compression valves and apply hydraulic fluid at a selected rate and time after the second chambers are substantially full of drilling fluid so as to pressurize the drilling fluid in the second chambers to a selected pressure substantially equal to a pressure in a drilling fluid discharge line hydraulically coupled to the second chambers, the valve controller adapted to close the compression valves after pressurization and before opening hydraulic fluid inlet valves coupled to the first chambers and to a hydraulic fluid inlet line and drilling fluid outlet valves coupled to the second chambers and to the drilling fluid discharge line.

12. The subsea pump of claim 11, wherein the hydraulic power supply comprises a flow regulated hydraulic power supply hydraulically coupled to the hydraulic fluid inlet valves and a non-flow regulated hydraulic power supply hydraulically coupled to the compression valves, the flow regulated hydraulic power supply comprising a dump valve adapted to control a pressure of hydraulic fluid supplied therefrom.

13. The subsea pump of claim 1, further comprising decompression valves hydraulically coupled to the hydraulic power supply and to each of the first chambers, the valve controller being operatively coupled to the decompression valves and adapted to open the decompression valves and release hydraulic fluid at a selected rate and time after the first chambers are substantially full of hydraulic fluid so as to depressurize the hydraulic fluid in the first chambers to a selected pressure substantially equal to a pressure in a hydraulic fluid discharge line hydraulically coupled to the first chambers, the valve controller adapted to close the decompression valves after depressurization and before opening hydraulic fluid outlet valves coupled to the first chambers and to the hydraulic fluid discharge line and drilling fluid inlet valves coupled to the second chambers and to a drilling fluid inlet line.

14. The subsea pump of claim 1, wherein the valve controller is adapted to maintain a selected differential pressure between hydraulic fluid supplied by the hydraulic power source and drilling fluid in a drilling fluid discharge line so as to reduce pressure surges into the second chambers when drilling fluid outlet valves are opened.

15. The subsea pump of claim 14, wherein the differential pressure is selected from a range comprising approximately 50 psi to approximately 150 psi.

16. The subsea pump of claim 1, wherein the valve controller is adapted to maintain a selected differential pressure between hydraulic fluid supplied by the hydraulic power source and drilling fluid in a drilling fluid discharge line so as to reduce hydraulic hammering when hydraulic fluid outlet valves are opened.

17. The subsea pump of claim 16, wherein the differential pressure is selected from a range comprising approximately 50 psi to approximately 150 psi.

18. The subsea pump of claim 1, further comprising an accumulator hydraulically coupled to a hydraulic fluid supply line, the hydraulic fluid supply line hydraulically coupling the hydraulic power supply to each of the first chambers, the accumulator adapted to minimize pressure fluctuations in the hydraulic fluid supply line.

19. The subsea pump of claim 1, further comprising a pressure transducer operatively coupled to the valve controller and adapted to measure a hydrostatic pressure proximate the subsea pump, the valve controller adapted to maintain the hydraulic fluid in a hydraulic fluid supply line at a pressure at least equal to the measured hydrostatic pressure.

20. A method for operating a subsea pump comprising a plurality of pumping elements, each pumping element comprising a pressure vessel with a first and a second chamber therein and a separating member disposed between the first and second chambers, the first and second chambers being hydraulically coupled to receive and discharge a hydraulic fluid and a drilling fluid, respectively, wherein the separating member moves within the pressure vessel in response to a pressure differential between the first and second chambers, the method comprising:

measuring a volume of at least one of the first and second chambers; and

applying hydraulic fluid to each of the first chambers at a selected rate and time, and enabling discharge of the hydraulic fluid at a selected time therefrom in response to the measurements of volume so as to maintain at least one of a substantially constant pump inlet pressure, a substantially constant pump discharge pressure, and a substantially constant total volume of the first chambers.

21. The method of claim 20, wherein the rate and timing of the application of the hydraulic fluid is controlled to maintain a substantially constant total volume of the drilling fluid in the second chambers.

22. The method of claim 20, wherein the rate and timing of the application of the hydraulic fluid is controlled to maintain a selected pressure differential between the hydraulic fluid applied to the first chambers and drilling fluid in a drilling fluid discharge line.

23. The method of claim 20, wherein applying hydraulic fluid comprises determining a fill status of the first and second chambers from the volume measurements and operating inlet and outlet valves connected to the first chambers and second chambers at selected times in response to the fill status so as to enable filling of the first chambers with hydraulic fluid and emptying of drilling fluid from the second chambers.

24. The method of claim 20 wherein enabling discharge of hydraulic fluid comprises determining a fill status of the first and second chambers from the volume measurements and operating inlet and outlet valves connected to the first chambers and second chambers at selected times in response to the fill status so as to enable emptying of hydraulic fluid from the first chambers and filling of the second chambers with drilling fluid.

25. The method of claim 20, further comprising applying the hydraulic fluid to the first chambers at a selected rate and time after the second chambers are substantially full of drilling fluid so as to pressurize the hydraulic fluid in the first chambers and the drilling fluid in the second chambers to a selected level substantially equal to a pressure of drilling fluid in a drilling fluid discharge line hydraulically coupled to the second chambers before enabling an inflow of hydraulic fluid into the first chambers and an outflow of drilling fluid from the second chambers.

26. The method of claim 25, further comprising delaying the application of the hydraulic fluid by a selected time so as to ensure that a flow path has been established between a hydraulic fluid supply line and the first chambers.

27. The method of claim 25, further comprising delaying the inflow of hydraulic fluid by a selected time so as to ensure that a flow path has been established between a hydraulic fluid supply line and the first chambers.

28. The method of claim 25, further comprising delaying the outflow of the drilling fluid by a selected time so as to ensure that a flow path has been established between the second chambers and the drilling fluid discharge line.

29. The method of claim 20, further comprising releasing the hydraulic fluid from the first chambers at a selected rate and time after the second chambers are substantially empty of drilling fluid so as to depressurize the hydraulic fluid in the first chambers to a selected level substantially equal to a pressure of hydraulic fluid in a hydraulic fluid discharge line hydraulically coupled to the first chambers before enabling an outflow of hydraulic fluid from the first chambers and an inflow of drilling fluid into the second chambers.

30. The method of claim 29, further comprising delaying the releasing of the hydraulic fluid by a selected time so as to ensure that a flow path has been established between the first chambers and the hydraulic fluid discharge line.

31. The method of claim 29, further comprising delaying the outflow of hydraulic fluid by a selected time so as to ensure that a flow path has been established between the first chambers and the hydraulic fluid discharge line.

32. The method of claim 29, further comprising delaying the inflow of the drilling fluid by a selected time so as to ensure that a flow path has been established between the second chambers and a drilling fluid supply line.

33. The method of claim 20, wherein the measuring a volume comprises measuring a position of the separating member and integrating the result.

34. The method of claim 20, wherein the measuring a volume comprises measuring a position of the separating member and converting the position measurement into a volume measurement using an empirically determined algorithm.

35. The method of claim 20, wherein the measuring a volume comprises measuring a position of the separating member and converting the position measurement into a volume measurement using an empirically determined look-up table.