Method of Operating a Subsea Production System, a Subsea Tree and an Electric Downhole Safety Valve

Abstract

A method of operating a subsea production system (1), the system comprising a subsea tree (2) connected to a subsea well (3), a production tubing (4) in the well (3), and an electrically operable electric downhole safety valve (5), wherein the method comprises, in case of malfunction in operation of the electric downhole safety valve (5), the steps of installing a hydraulically operable insert hydraulic downhole safety valve (6) within the production tubing (4); connecting the insert hydraulic downhole safety valve (6) to the fluid line (10) at a point of setting (7) in the subsea well (3); operating the insert hydraulic downhole safety valve (6) by using the fluid line (10) which extends from an input port (11) at a position outside of the subsea tree (2).

Claims

1. A method of operating a subsea production system, the system comprising an electric subsea tree connected to a subsea well, a production tubing in the well, and an electrically operable electric downhole safety valve, the electric subsea tree comprising a through-going bore forming part of a fluid line in the subsea production system extending down to a position at or close to the electric downhole safety valve, wherein the method comprises, in case of malfunction in operation of the electric downhole safety valve, the steps of: installing a hydraulically operable insert hydraulic downhole safety valve into the well for positioning within the production tubing; connecting the insert hydraulic downhole safety valve to the fluid line at a point of setting in the subsea well, for operation of the insert hydraulic downhole safety valve; operating the insert hydraulic downhole safety valve from a position outside the subsea tree using the fluid line, wherein the fluid line extends from an input port located at a position outside of the electric subsea tree to the point of setting in the subsea well via the through-going bore.

2. The method according to claim 1, wherein the system comprises an implement profile located below the electric subsea tree, and wherein the method further comprises: installing the insert hydraulic downhole safety valve in the implement profile.

3. The method according to claim 2, wherein the implement profile is arranged between the electric subsea tree and the electric downhole safety valve.

4. The method according to claim 2, wherein the implement profile is provided in the electric downhole safety valve, and wherein during the step of installing the insert hydraulic downhole safety valve in the implement profile in the electric downhole safety valve, thereby forcing the electric downhole safety valve is forced into an open position, thereby inactivating the electric downhole safety valve.

5. The method according to claim 1, further comprising, prior to the step of operating the hydraulically operable insert hydraulic downhole safety valve: lowering a hydraulic fluid source in the form of a subsea hydraulic power unit and a control unit subsea; and connecting the subsea hydraulic power unit to the input port.

6. The method according to claim 1, further comprising, prior to the step of operating the hydraulically operable insert hydraulic downhole safety valve: installing a fluid conduit from existing infrastructure in the field to the input port of the fluid line, the existing infrastructure comprising hydraulic or chemical distribution means and control means; and lowering a control unit to the seabed and connecting it to the control means; and connecting the fluid line to the insert hydraulic downhole safety valve at the point of setting such so as to provide a fluid connection between the subsea existing infrastructure and the insert hydraulic downhole safety valve via the fluid line.

7. A subsea production system comprising: a subsea well; an electric subsea tree positioned above the well, the electric subsea tree being connected to the subsea well; and a production tubing arranged inside the well, the production tubing comprising: an electrically operable electric downhole safety valve; and an implement profile arranged within the production tubing and configured for receiving a hydraulically operable insert hydraulic downhole safety valve; a through-going bore configured to support a hydraulic fluid line in the subsea production system, the fluid line extending from an input port at a position outside of the electric subsea tree to a point of setting in the subsea well, thereby enabling operation of the insert hydraulic downhole safety valve from a position outside the electric subsea tree via the through-going bore.

8. The system according to 7, further comprising a tubing hanger which comprises a hydraulic connection hydraulically connecting a first side of the tubing hanger with an opposite second side of the tubing hanger, wherein the hydraulic connection forms part of the hydraulic fluid line.

9. An electric subsea tree comprising: communication means for operating an electrically operable electric downhole safety valve; and a through-going bore for a hydraulic fluid line, the through-going bore enabling the creation of a fluid connection from a position outside of the subsea tree to an interface configured for connection to a well, whereby an insert hydraulic downhole safety valve can be operated from a position outside the subsea tree.

10. An electric downhole safety valve comprising: an implement profile configured for receiving a hydraulically operable insert hydraulic downhole safety valve; and a through-going opening for hydraulic fluid for hydraulically operating the hydraulically operable insert hydraulic downhole safety valve.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0062] FIG. 1A is an overview of the main components forming part of the subsea production system according to the invention, including a subsea tree connected to the subsea well, a production tubing in the well, and an electric downhole safety valve in the well;

[0063] FIG. 1B is an enlarged view of section A in FIG. 1A, showing more details of the electric downhole safety valve;

[0064] FIG. 2A shows an example of a typical prior art hydraulic tubing retrievable surface controlled subsurface safety valve (TRSCSSV) which is a hydraulic operated downhole safety valve with flapper;

[0065] FIG. 2B shows an example of a typical prior art hydraulic wireline retrievable surface controlled subsurface safety valve (WRSCSSV) which is a hydraulic downhole safety valve with flapper;

[0066] FIG. 3A shows an electric downhole safety valve comprising an implement profile configured for receiving a hydraulically operable insert hydraulic downhole safety valve without the hydraulically operable insert hydraulic downhole safety valve installed;

[0067] FIG. 3B shows an electric downhole safety valve comprising an implement profile configured for receiving a hydraulically operable insert hydraulic downhole safety valve with the hydraulically operable insert hydraulic downhole safety valve installed;

[0068] FIG. 4A shows an example of a subsea production system, the system comprising a subsea tree connected to the subsea well, a production tubing in the well, and an electrically operable electric downhole safety valve, where the subsea tree comprises a through-going bore configured to support a hydraulic fluid line in the subsea system, wherein the hydraulic fluid line extends from an input port at a position outside of the subsea tree to the point of setting;

[0069] FIG. 4B shows an example of a tubing hanger to be used with the production system of FIG. 4A;

DETAILED DESCRIPTION OF THE INVENTION

[0070] In the following, embodiments of the invention will be discussed in more detail with reference to the appended drawings. It should be understood, however, that the drawings are not intended to limit the invention to the subject-matter depicted in the drawings.

[0071] FIG. 1A is an overview of the main components forming part of the subsea production system according to the invention, including a subsea tree connected to the subsea well, a production tubing in the well, and an electric downhole safety valve in the well. FIG. 1A shows the situation before the insert hydraulic downhole safety valve has been installed in the well. The electric downhole safety valve typically has a lock open mechanism, which secures that access to the well is achieved at any time without the risk of uncontrolled closing of the bore in the production tubing. The subsea tree can be an electric subsea tree or a hydraulic subsea tree.

[0072] FIG. 1B is an enlarged view of section A in FIG. 1A, showing more details of the electric downhole safety valve.

[0073] FIG. 2A shows an example of a typical prior art hydraulic tubing retrievable surface controlled subsurface safety valve (TRSCSSV) 23 which is a hydraulic operated downhole safety valve with flapper 24. The main functional components of the TRSCSSV 23 typically includes a housing 25, a flapper function 24, a power spring 26, a hydraulic piston 27, a hydraulic chamber 28, a flow tube 29, a control line 30, and a nipple profile 31 for insert hydraulic downhole safety valve (e.g. insert valve run on wireline). The end of the control line 30 is connected to the valve inlet connection port which is a threaded connection with metal-to-metal seal. This is normally done on the platform before subsea deployment. It could also be done onshore and sent to the platform as pre-made assembly. The entire control line 30 is tested before the TRSCSSV 23 is run downhole with the production tubing (not shown in the figure but the TRSCSSV 23 forms part of the production tubing). In order to protect the control line 30 when run downhole, it is typically clamped to the outside of the production tubing while being run down hole. Most TRSCSSV 23 uses a single control line 30 for valve opening and the power spring 26 for valve closure because this gives the fail-safe close function upon hydraulic power supply failure. In a similar manner will an electric operated production installed downhole safety valve be configured and operated, as stay open while being feed electric power and automatic close when losing the power source.

[0074] FIG. 2B shows an example of a typical prior art hydraulic wireline retrievable surface controlled subsurface safety valve (WRSCSSV) 32 which is an insert hydraulic downhole safety valve with flapper 24. The main functional modules of the WRSCSSV 32 typically includes a housing 25w, a flapper 24w, a power spring 26w, a hydraulic piston 27w, a hydraulic chamber 28w, a control line 30w, a flow tube 29w, hydraulic seals (upper and lower sealbores) 34w, and a nipple profile 31w for insert hydraulic valve (e.g. insert valve run on wireline). The WRSCSSV 32 is a wireline retrievable surface controlled subsurface safety valve, also named insert WRSCSSV. The WRSCSSV 32 is basically reduced bore version of the TRSCSSV 23 with main application as through-tubing conveyed means for remediation of TRSCSSV failures. The WRSCSSV 32 is normally installed within the TRSCSSV 23 taking advantage of the existing hydraulic line. The WRSCSSV is installed on wireline into applicable nipple 31w in the production tubing (not shown in FIG. 2B). This nipple 31w is normally a part of the complete TRSCSSV assembly ready for installation. The WRSCSSV 32 will as an inserted valve have a reduced bore ID through the valve compared to the TRSCSSV and the tubing string.

[0075] Referring to FIGS. 2A and 2B, if experiencing a leak in the hydraulic TRSCSSV 23, the operator may run an exercise tool to force flow tube 29 to an upper position. Then an inflow test of the TRSCSSV 23 is performed as a standard procedure, including increasing the pressure above the TRSCSSV 23 over a predetermined period time. When the inflow test has been performed, any debris causing the flow tube 29 not to close properly is removed. If the TRSCSSV 23 is still leaking, install WRSCSSV 32. This sequence includes:

[0076] preparing TRSCSSV 23 for installation of insert valve by locking open the flapper 24 and establishing communication with control line 30 into well between upper and lower sealbore. However, there may also be situations where the flapper 24 will not open due to lack of power downhole, then it may be impossible to locking open the flapper 24 and the flapper 24 has to be opened in another way for example by stinger or spike in e.g. lockout/communication tool as described below.

[0077] Run lockout/communication tool and land in TRSCSSV nipple profile 31. Prong (e.g. stinger or spike) will push flapper 24 valve open without resistance. Jar and engage O-ring and expand locking dogs,

[0078] Jar down aggressively to establish communication between well and control line 30 Different need for establishing communication with control line.

[0079] Polish upper and lower sealbores 34w of insert WRSCSSV 32 before installing the insert WRSCSSV,

[0080] Install insert WRSCSSV 32 with flapper 24w locked open,

[0081] Communication from control line 30 and into well between the two sealbores (i.e. upper and lower sealbores) 34w is established,

[0082] Tap insert WRSCSSV 32 in place until it lands in no-go. Upper and lower sealbores 34w shall now be in place in the polished area,

[0083] Pressure up control line 30w and leak test for a predetermined time. Inflow test insert WRSCSSV 32, including increasing the pressure above the WRSCSSV 32 over a predetermined period of time.

[0084] In the following different methods of operating a subsea production system according to the invention will be described in greater detail. The methods and associated subsea production system and electric subsea tree have many common features with the installation sequence described in relation to FIGS. 2A and 2B, however according to the present invention, due to the fact there is an electric subsea tree with no hydraulic fluid to the surface, the TRSCSSV has been changed with an electrically operable electric downhole safety valve. As indicated above, in FIG. 1A it is an overview of the main components forming part of the electric subsea production system according to the invention, including an (all)-electric subsea tree connected to the subsea well, a production tubing in the well, and an electric downhole safety valve in the well. FIG. 1A shows the situation before the insert hydraulic downhole safety valve has been installed in the well.

[0085] FIG. 3A shows an electric downhole safety valve 5 comprising an implement profile 8 configured for receiving a hydraulically operable insert hydraulic downhole safety valve without the hydraulically operable insert hydraulic downhole safety valve installed.

[0086] FIG. 3B shows an electric downhole safety valve 5 comprising an implement profile 8 configured for receiving a hydraulically operable insert hydraulic downhole safety valve 6 with the hydraulically operable insert hydraulic downhole safety valve 6 installed.

[0087] FIG. 4A shows an example of an subsea production system 1, the system 1 comprising an electric subsea tree 2 connected to the subsea well 3, a production tubing 4 in the well 3, and an electrically operable electric downhole safety valve 5. The electric subsea tree 2 comprises a through-going bore 9 configured to support a hydraulic fluid line 10 in the electric subsea system 1. The hydraulic fluid line 10 extends from an input port 11 at a position outside of the subsea tree 2 to a point of setting 7 at a position at or close to the electric downhole safety valve 5. The point of setting 7 is shown as being the same position as the implement profile 8 for landing the insert hydraulic downhole safety valve 6. The hydraulic fluid line 10 extends outside of the production tubing 4 but inside the well 3. A hydraulic fluid source in the form of a subsea hydraulic power unit 12 and a control unit subsea 13 have been lowered subsea to a position at or close the electric subsea tree 2. The subsea hydraulic power unit 12 is connected to the input port 11 and the hydraulic fluid line 10 is connected to the insert hydraulic downhole safety valve 6 at the point of setting 7. As such, a hydraulic connection between the subsea hydraulic power unit 12 and the insert hydraulic downhole safety valve 6, via the hydraulic fluid line 10, has been established. In case hydraulic infrastructure is already in place in the field the subsea high-pressure unit may not be required.

[0088] A remotely operated vehicle 19 connected to a surface facility 21 via a connection line 21 may be used in assisting installation of subsea hydraulic power unit 12 and when connecting e.g. subsea hydraulic power unit 12 to input port 11.

[0089] FIG. 4B shows an example of a tubing hanger to be used with the production system of FIG. 4A. The tubing hanger comprises a hydraulic connection 18 hydraulically connecting a first side of the tubing hanger 17 with an opposite second side of the tubing hanger, wherein the hydraulic connection forms part of the hydraulic fluid line. The tubing hanger 17 further comprises standard connections when used in a subsea production system 1, including connections or ports to surface controlled subsea safety valve A (eSCSSV A) 22′ and surface controlled subsea safety valve B (eSCSSV B) 22″.

[0090] The invention has been explained with reference to non-limiting embodiments. For example, any subsea tree with an electric downhole safety valve can be used, including an electric subsea tree, an all-electric subsea tree and a hydraulic subsea tree. Furthermore, a skilled person will understand that there may be made alternations and modifications to the embodiment that are within the scope of the invention as defined in the attached claims.

REFERENCE LIST

[0091]

TABLE-US-00001  1 subsea production system,  2 subsea tree  3 subsea well  4 production tubing  5 electric downhole safety valve  6 insert hydraulic downhole safety valve  7 a point of setting  8 Implement profile  9 through-going bore in tree 10 hydraulic fluid line 11 input port 12 subsea hydraulic power unit 13 Subsea control unit 17 Tubing hanger 18 hydraulic connection in tubing hanger 19 Remotely Operated Vehicle, ROV 20 Surface facility 21 connection line 22′ surface controlled subsea safety valve A connection 22″ surface controlled subsea safety valve B connection 23 TRSCSSV 24 Flapper 24w Flapper WRSCSSV 25 Housing (TRSCSSV) 25w Housing (WRSCSSV) 26 Power spring 26w Power spring (WRSCSSV) 27 Hydraulic piston 27w Hydraulic piston (WRSCSSV) 28 Hydraulic chamber 28w Hydraulic chamber (WRSCSSV) 29 Flow tube 29w Flow tube (WRSCSSV) 30 Control line 30w Control line (WRSCSSV) 31 Nipple profile 31w Nipple profile (WRSCSSV) 32 WRSCSSV 34w Hydraulic seals/Sealbores (upper and lower) A Section A