Delivering fluid to a subsea wellhead

Patent metadata

Field	Value
Publication number	US-11512550-B2
Application number	US-202017100081-A
Country	US
Kind code	B2
Filing date	Nov 20, 2020
Priority date	Nov 22, 2019
Publication date	Nov 29, 2022
Grant date	Nov 29, 2022

Abstract

The invention relates to the introduction of pressurized fluid, e.g. acid, into a subsea well directly from a vessel ( 33 ). A fluid injection assembly ( 20 ) is fitted to the top of a subsea Xmas tree ( 3 ), the assembly ( 20 ) including fail safe closed valve ( 21 ) which is controlled via a hydraulic line ( 31 ) from the vessel. The hose and assembly and valve are designed with an internal bore allowing a large diameter ball to be dropped (required for acid stimulation). The subsea subsea control module ( 8 ) on the Xmas tree is controlled from the producing platform.

First claim

The invention claimed is:

1. A pressurized fluid injection assembly suitable for lowering onto and mounting to a top of a subsea Xmas tree, the Xmas tree having a first conduit communicating with production tubing of a subsea hydrocarbon well, the fluid injection assembly comprising:
a second conduit for delivery of fluid via the Xmas tree to the hydrocarbon well;
a connector at a first end of the second conduit, for connecting the second conduit to the first conduit of the Xmas tree;
only a single valve in the second conduit, wherein the valve is a fail-safe close valve;
wherein the second conduit and the fail-safe close valve have an unobstructed internal diameter of at least 4″;
a fluid delivery connector for connecting to a fluid delivery pipe for supply of fluid to the injection assembly, the fluid delivery connector located at a second end of the second conduit.

2. The fluid injection assembly according to claim 1 , suitable for injection of fluid at a rate between 5,000 and 15,000 liters per minute.

3. The fluid injection assembly according to claim 1 , wherein the second conduit includes a rigid piping section having one or more bends of 90 degrees or more, whereby the fluid delivery connector is provided at an end of the rigid piping section.

4. The fluid injection assembly according to claim 1 , wherein, when the assembly is secured with respect to the seafloor, the fluid delivery connector is directed upwardly.

5. The fluid injection assembly according to claim 4 wherein the fluid delivery connector is also adapted to receive lifting point member, whereby a lifting point for the assembly is provided.

6. The fluid injection assembly according to claim 1 , further comprising a guide funnel for guiding a fluid delivery pipe or lifting point member into position to connect to the fluid connector.

7. A system for injecting pressurized fluid into a subsea hydrocarbon well, the system comprising:
a subsea Xmas tree having a first conduit communicating with production tubing of a subsea hydrocarbon well;
a fluid injection assembly mounted on top of the subsea Xmas tree, the fluid injection assembly comprising: (i) a second conduit for delivery of fluid via the Xmas tree to the hydrocarbon well; (ii) a connector at a first end of the second conduit, for connecting the second conduit to the first conduit of the Xmas tree; (iii) the second conduit having only a single valve, wherein the valve is a fail-safe close valve, and wherein the second conduit and the fail-safe close valve have an unobstructed internal diameter of at least 4″; (iv) a fluid delivery connector for connecting to a fluid delivery pipe for supply of fluid to the injection assembly, the fluid delivery connector located at a second end of the second conduit;
a marine vessel including a fluid supply and a control unit;
a fluid delivery pipe including a subsea connector at a first end for connecting to the fluid injection assembly and a connector at a second end for connecting to the fluid supply;
a control line extending between the fluid injection assembly and the control unit, for controlling the fail-safe close valve of the fluid injection assembly.

8. The system according to claim 7 , suitable for injection of fluid at a rate between 5,000 and 15,000 liters per minute.

9. The system according to claim 7 , wherein the fluid delivery pipe has an unobstructed internal diameter of at least 4″.

10. The system according to claim 7 , wherein the fluid delivery pipe comprises a hose and a rigid connecting pipe having one or more bends of 60 degrees or more, the subsea connector being located on an end of the rigid connecting pipe, wherein the rigid connecting pipe is releasably connected to the hose.

11. The system according to claim 7 , wherein the Xmas tree includes a subsea control module for controlling at least a production master valve of the Xmas tree, the subsea control module controllable from a nearby production platform, and wherein no means is provided for control of the subsea control module directly from the vessel.

12. A method of delivering pressurized acid to a subsea hydrocarbon wellhead, the method comprising:
a. removing a tree cap from a Xmas tree of a subsea well assembly;
b. mounting a pressurized fluid injection assembly on top of the Xmas tree, the fluid injection assembly comprising a connector for a fluid delivery pipe and only a single valve, wherein the valve is a fail-safe close valve;
c. connecting a first end of a fluid delivery pipe to the connector, a second end of the fluid delivery pipe being connected to a fluid supply apparatus installed on a marine vessel;
d. delivering acid under pressure, via the fluid delivery pipe and the fail-safe valve, to production tubing of a well via the Xmas tree;
e. controlling the fail-safe valve from the marine vessel;
f. controlling from a production platform a production master valve and/or downhole safety valve associated with the Xmas tree;
g. including the step of dropping or pumping a ball from the marine vessel through the fluid delivery pipe and into the production tubing of the well.

13. The method according to claim 12 , wherein step b includes lowering the pressurized fluid injection assembly into place on the Xmas tree by crane, using a lifting point member installed in the connector of the assembly, and wherein the lifting point member is removed prior to step c.

14. The method according to claim 12 , wherein the second end of the fluid delivery pipe is connected via a quick release connector to the fluid supply apparatus via a hose reel or via some other structure.

15. The method according to claim 12 , wherein step c is performed by lowering the first end of the fluid delivery pipe into position using a crane.

16. The method according to claim 12 , wherein the fluid delivery pipe comprises a hose and a rigid connecting pipe having one or more bends of 60 degrees or more, and a subsea connector being located on an end of the rigid connecting pipe, and wherein step c is performed by:
(i) lowering the hose into a bracket adjacent the Xmas tree;
(ii) lowering the connecting pipe;
(iii) connecting a first end of the connecting pipe to the hose;
(iv) connecting the subsea connector of the connecting pipe to the connector of the fluid injection assembly.

17. The method according to claim 12 , maintaining the fail-safe valve open with positive hydraulic pressure on a hydraulic line from the vessel.

18. The method according to claim 12 , wherein the acid is delivered at a rate between 5,000 and 15,000 litres per minute.

Assignees

• Conocophillips Co

Inventors

• Kvarme Leif
• Spence John
• Heigre Birger

Classifications

• E21B33/076 Primary

  specially adapted for underwater installations · CPC title

• E21B19/002

  specially adapted for underwater drilling (E21B19/09, E21B19/143 take precedence) · CPC title

• E21B34/04

  in underwater well heads · CPC title

• E21B41/0007 Primary

  for underwater installations (E21B41/005, E21B41/04, E21B41/06, E21B41/08, E21B41/10 take precedence) · CPC title

• E21B19/16

  Connecting or disconnecting pipe couplings or joints (E21B19/20 takes precedence) · CPC title