NO20220840A1

NO20220840A1 -

Info

Publication number: NO20220840A1
Application number: NO20220840A
Authority: NO
Priority date: 2022-07-29
Filing date: 2022-07-29
Publication date: 2024-01-29
Also published as: NO347615B1

Description

SUBSEA WELL INTERVENTION TOOL-STRING ASSEMBLY AND DEPLOYMENT

Well interventions are remedial operations, performed on oil or gas producing wells, to restore, or increase production. Well intervention does not normally cover the ability to perform full drilling operations, or workovers, with pulling and installing completions.

This invention concerns Riser-less Light Well Intervention (RLWI), which is known in the art of Subsea Oil &Gas technology. An RLWI stack can be run from an offshore vessel and be connected on top of a subsea X-mas tree to perform well intervention, without the use of a workover riser (WOR), or a marine drilling riser.

More specifically, it concerns a telescopic conduit for assembling and suspending a wireline tool-string, parking a tool-string between RLWI operations, and guiding a tool-string through the conduit from the surface, through the splash zone and below the hull of a Mobile Offshore Drilling Unit, (MODU), and further into the subsea environment.

A wireline well intervention tool shall be deployed, guideline less, from a MODU. A toolstring is attached to the end of a well intervention cable or wire, which is lowered through the sea and inserted into a subsea well. The tool-string is guided by a Remotely Operated Vehicle (ROV) into a subsea lubricator section of a RLWI stack, where it is sealed off towards the subsea environment, before it is lowered past the well barrier valves of the RLWI stack and a subsea X-mas tree, into the well, under full pressure.

Cables for wireline operations are slickline, braided line and e-line cable. Braided line is a multi-strand wireline for slickline applications, with higher tension or weight-carrying ability. E-line is a braided wire with electrical cable inside, to provide electrical power and communication to a well tractor. A well intervention tool-string consists of a wireline tool-string assembly and a Pressure Control Head (PCH). Slickline tools operate with mechanical action (such as jars). A slickline tool-string consists of a rope socket, stem (weights) or roller stem, jar and different tools that can be attached at the bottom.

During the lifetime of a subsea well, reservoir water cut increases, gas-oil ratio (GOR) rises, and corrosion, scaling and mechanical problems occur. Some wells have exceeded their expected design life through Improved Oil Recovery (IOR) measures. Poor hydrocarbon recovery rates for subsea wells can be attributed to a lack of well intervention, and limitations of available well intervention techniques to address the challenges. Ultimate recovery from subsea wells has typically been less than 35%, while recovery from landbased and platform wells is above 50%, and in some cases as high as 70%.

Traditionally, subsea well intervention has been done through a workover riser (WOR) from offshore drilling rigs. Expected production gains often did not justify the cost of well intervention. The large cost of mobilising such rigs has led to wells being left unattended for too long, low-producing, or merely shut-in due to integrity concerns. The need for well interventions has increased as the number of producing wells and their age have increased. This has been a stimulus for the development of more cost-effective subsea well intervention methods, with a goal of raising ultimate recovery of subsea wells above 50%.

During the emergence of subsea production technology, in the 1980s and 1990s, WOR`s were primarily equipment used in connection with subsea well completion operations. After the turn of the century, lighter well intervention systems emerged, which could be deployed in open water, from well intervention vessels. These are both riser-based and riserless (RLWI). RLWI Stacks are typically adaptable to any existing subsea production system on the market. The introduction of RLWI from vessels with lower day-rates than a MODU and a high degree of efficiency through high transit speed, no anchor handling, and no time spent on running a riser, has provided a cost reduction of about 2/3, compared with traditional, riser-based well intervention operations from offshore drilling rigs. This has lowered the economic threshold for the initiation of subsea well intervention. However, a MODU will have a wider range of usage than a monohull RLWI vessel, which is typically limited to these operations:

− Pull and set plugs

− Well monitoring, Run wireline (logs)

− Make well diagnosis

− Perforating/re-perforating

− Subsea equipment repair

− X-mas Tree running and retrieval

Well Plug and Abandonment (P&A) and Coiled Tubing operations from RLWI vessels are emerging services but are examples of operations where a MODU will be a competitive alternative. Limitations of RLWI vessels include: - Personnel on Board (POB), fluids capacity, logistics and crane capacity. Apart from the many superior capabilities of a MODU, another favourable factor is the lower weather vulnerability, which can make a difference during the winter months.

The main drawback of a MODU, is the higher cost of intervention. A way to improve the competitiveness of MODU`s, is the facilitation of RLWI operations alongside other tasks. This will save time, compared to wireline operations through a WO riser. Preparations can be done offline, while the rig is used for other tasks. This can be enabled through the introduction of a post-installable telescopic deployment conduit, which will be used for wireline tool-string assembly, protected parking of tool-strings between well operations, and protected lowering of the tool-string through the splash zone, and below the vessel hull.

To obtain well control during an intervention operation, a RLWI Stack will be mounted on top of the subsea production X-Mas tree, (XMT), which is connected to the subsea wellhead. An RLWI stack comprises both a Well Control package, with well barrier devices, and a Lubricator Section for tool entry into the RLWI stack and sealing around the wireline (WL) during downhole operations. The RLWI lubricator section has the necessary length to accommodate the tool-string, and space-out below the PCH.

The tool-string with the PCH shall be lowered with a heave compensated lifting wire from the MODU, through the extended telescopic deployment conduit, and open water, down to the RLWI stack. This was originally done as a guidewire operation, but guideline less RLWI operation has been developed in later years.

When the tool-string has been inserted into the subsea lubricator section, the Pressure Control Head (PCH) is locked to the Upper Lubricator Package (ULP) connector. The PCH provides the primary seal towards the subsea environment when the wireline is run into the well. The seal around the wireline is achieved by pumping viscous grease between the limited free space in the wireline and narrow tubes in the PCH. A tool catcher may be located at the bottom of the PCH, with the function of catching and holding the tool if the tool-string is unintentionally pulled into the PCH and the wireline is broken.

The MODU will typically have two off PCH. One can be used for RLWI operation, while the other is stored in preparation for deployment of a second, pre-assembled tool-string, which is kept suspended inside a second, retracted, telescopic wireline tool-string deployment conduit.

In the following, a device, and a method for wireline tool-string deployment into a subsea well is described, which is illustrated in the attached drawings, wherein:

Fig. 1A shows a MODU with a telescopic wireline tool-string deployment conduit;

Fig. 1B shows in more detail a side view of a telescopic wireline tool-string deployment conduit, a support funnel located at a MODU pontoon, and a surface work platform for wireline tool-string assembly and deployment;

Fig. 2A shows a front view of two telescopic deployment conduits, - one is fully extended, and the other is fully retracted;

Fig. 2B shows at the bottom, in more detail, a front view of the lower end of an extended telescopic deployment conduit, and at the top, a front view of a retracted telescopic deployment conduit;

Fig. 2C shows at the bottom, in more detail, a side view of the lower end of an extended telescopic deployment conduit, and at the top, a side view of a retracted telescopic deployment conduit.

Fig. 3A shows a prior art running tool for guideline less deployment of a Pressure Control Head (PCH) and a tool-string;

Fig. 3B shows a prior art Pressure Control Head (PCH);

Fig. 4 discloses a prior art well intervention setup, and the components that are parts of a RLWI Stack.

Figure 1A and B show a MODU 1 with a telescopic deployment conduit 2, and a work platform 3 for tool-string assembly and deployment. Lifting wires 4 are attached to a yoke 5, which is fixed to the lower telescope joint 6.

An RLWI tool-string suspension device, (not shown), at the top of the conduit 2 will enable stepwise, vertical assembly of a, (not shown), wireline tool-string inside a retracted, telescopic deployment conduit 2B, shown in figure 2A. The tool-string will be kept suspended, until it is time for tool-string deployment.

As the lifting wires 4 are paid-out, or hauled-in, by winches (not shown), the telescopic joints of the deployment conduit 2 will be unfolded or collapsed/retracted in a controlled manner. Prior to the tool-string deployment, the conduit 2 is lowered into full extension, and the end of the lower telescope joint 6 will stab into a funnel 7, that extends to the bottom of the MODU 1 hull, and which provides lateral support to the lower part of the telescopic conduit 2. The funnel 7 will be fitted with a guide-cone in each end. The upper cone will guide the end of the lower telescope joint 6 into the funnel 7.

Figure 2A shows a front view of two telescopic deployment conduits, where one, 2A, is fully extended and the other, 2B, is fully retracted. The top part of figure 2B and 2C shows a front and side view of the yoke 5, abutting the bottom end of the upper/outer telescope joint of a retracted telescopic deployment conduit 2B. The bottom part of figure 2B and 2C shows a front and side view of a lower telescope joint 6, stabbed into the funnel 7.

Figure 3A shows a prior art Guideline Less Running Tool (GLL RT) 8, with a tool protection frame 9. A GLL RT lifting sling 10 is attached to the top ring of the protection frame 9, while the upper part of the sling is connected to a crane hook 11, which hangs from a heave compensated lifting wire 12. Figure 3B shows details of a prior art, Pressure Control Head (PCH) 13, with a wireline sealing section 14.

Prior to tool-string deployment, a well intervention wire or cable 15 is inserted through the PCH 13, and the GLL RT 8 is connected to the top end of the PCH sealing section 14. The PCH 13 is moved by the crane 16, to a position above the extended funnel 2A, and the suspended tool-string (not shown) in the conduit 2B is attached to the intervention wire 15. The tool-string is released from suspension in the conduit 2, before it is lowered down, by paying out the lifting wire 12, while the intervention wire 15 is paid out simultaneously. The tool-string will typically hang 2-3 meters below the PCH 13 during deployment.

Figure 4 shows a prior art well intervention setup, and the main components forming part of an RLWI Stack 17. The PCH hub 18 interfaces a connector 19 on top of the Upper Lubricator Package (ULP) 20 of the Lubricator Section (LS) 21. The Upper Lubricator Package (ULP) 20 is mounted on top of the Lubricator Tubular (LT) 22, and contains a wire line cutting ball valve, a circulation outlet, and the ULP connector 19 towards the PCH hub 18 on the PCH 13. The Lubricator Tubular (LT) 22 carries the grease reservoirs and the highpressure grease injection pumps and is connected on top of the Lower Lubricator Package (LLP) 23. The LLP 23 has a Lower Lubricator Package connector 24 to connect the LLP 23 to a Well Control Package (WCP) 25, in a known manner.

When the tool-string has been lowered to the RLWI stack 17, it will be guided by an ROV, and inserted into the subsea lubricator section 21, before the PCH 13 is locked onto the RLWI stack, with the Upper Lubricator Package (ULP) connector 19. The PCH 13 provides the primary seal around the intervention wireline 15 towards the subsea environment, when the tool-string is run into the well. Sealing around the moving wireline will be facilitated through the pumping of viscous grease between the limited free space in the wireline 15 and the narrow tubes inside the sealing section 14 of the PCH 13. The injection system in the LLP 23 will supply grease at a pressure above the wellhead pressure.

The prior art PCH 13 in fig.3B shows the PCH hub 18 with a guide cone. This is not optimal for deployment through the telescopic deployment conduit 2. In an alternative configuration, the cone can be placed at the ULP connector 19, to minimize the diameter of the PCH 13. Consequently, a smaller inner diameter can be used for the telescopic joints.

After connection of the PCH 13 to the (ULP) connector 19, the GLL RT 8 can be released from the PCH 13 by means of an ROV and will be hoisted back to surface. The GLL RT 8 will be re-deployed through the conduit 2 to retrieve the PCH 13 and the tool-string, when the well-intervention task is completed. The lower cone of the funnel 7 will guide the hook 11 of the lifting wire 12 and the GLL RT 8 into the telescopic deployment conduit 2 during the retrieval operations.

Claims

P a t e n t c l a i m s

1. Telescopic conduit for assembling and suspending a wireline tool-string, parking of a tool-string between RLWI operations, and guiding of a tool string through the conduit from the surface, into the subsea environment, c h a r a c t e r i s e d i n that the system comprises:

at least one telescopic conduit (2) for subsea deployment of a wireline tool-string and a Pressure Control Head, (13), and

a tool-string suspension device for each conduit (2), located at a work platform (3), for vertical assembly, or dis-assembly of a wireline tool-string, and

a device for collapsing, or extending the conduit (2) telescopic tubular joints, consisting of lifting wires (4), attached to a yoke (5), which is fixed to the lower telescope tubular joint (6), and which are hauled-in, or are paid-out, with at least one winch, and

a funnel (7), with a guide-cone in each end, that provides lateral support for the lower end of the extended conduit (2).

2. Method for assembly and suspension of a wireline tool-string at the top end of a telescopic conduit (2), parking of a tool-string between RLWI well operations, and deployment of a wireline tool-string from the surface, through the telescopic conduit and out into open water, c h a r a c t e r i s e d i n that the method comprises the steps of:

a) assembling a wireline tool-string, and suspending it in a telescopic conduit (2), according to claim 1;

b) fully extending the telescopic conduit (2), so it enters the funnel (7) at the vessel (1) lower hull, by paying out lifting wires (4) that are connected to the lower telescope joint (6), by means of the yoke (5), according to claim 1;

c) inserting a well intervention wire (15) through a PCH (13), connecting a GLL RT (8) to the PCH, suspending the PCH above the telescopic conduit (2), attaching the well intervention wire to the wireline tool-string, releasing the tool-string from suspension in the conduit (2), and lowering the PCH and the tool-string through the conduit, and further into open water, down to a RLWI stack (17);

d) releasing and retrieving the GLL RT (8) up through the conduit (2), when the PCH (13) has been connected to the top of the RLWI stack (17);

e) lowering the GLL RT (8) through the conduit (2) and to the RLWI equipment, to recover the PCH (13) and the tool-string, when the well-intervention has been completed;

f) hoisting the lower telescope joint (6) by means of lifting wires (4), connected to the yoke (5), and collapsing the telescopic conduit (2), until the yoke (5) abuts the bottom end of the upper/outer telescope tubular joint, according to claim 1;

g) dis-assembly of the wireline tool-string, according to claim 1.