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Subsea Well Intervention Vessel and SystemsG.H.T. Zijderveld (SPE), J .J . Tiebout (SPE), S.M. Hendriks, L. Poldervaart (SPE), GustoMSC

Copyright 2012, Offshore Technology Conference

This paper was prepared for presentation at the Offshore Technology Conference held in Houston, Texas, USA, 30 April3 May 2012.

This paper was selected for presentation by an OTC program committee following review of information contained in an abstract submitted by the author(s). Contents of the paper have not beenreviewed by the Offshore Technology Conference and are subject to correction by the author(s). The material does not necessarily reflect any position of the Offshore Technology Conference, itsofficers, or members. Electronic reproduction, distribution, or storage of any part of this paper without the written consent of the Offshore Technology Conference is prohibited. P ermission toreproduce in print is restricted to an abstract of not more than 300 words; illustrations may not be copied. The abstract must contain conspicuous acknowledgment of OTC copyright.

Abstract

With the present deepwater developments on the increase it is foreseen that a dedicated market will develop for vessels

capable of intervening on subsea wells at a lesser cost than existing deepwater drilling units. Thereby (I) extend the life of

deepwater developments rendering additional profits and (II) adhere to minimum field production requirements as are being

required by the authorities more and more to date.

The paper describes the development of the concept for such a Well Intervention Vessel resulting from a combined effort

between a Naval Architecture Design Bureau and a major rig equipment supplier with a focus on an open equipment structure

facilitating the possible application of multiple levels of/and intervention solutions. The vessel will target Class B+/(II+) and

Class C/(III) type interventions, based upon systems which will use risers and capable of retrieving completions. Input of

operators as well as equipment- and service providers has been used in the development of the concept to develop the opensystem.

The proposed paper shall present in detail the design approach and basis, the concept design and the operational parameters ofthe deepwater well completion and intervention vessel. It will also address in detail the specific pieces of equipment to be used

on the vessel.

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Subsea Well Intervention Vessel and Systems

IntroductionDuring the last 15 years the development of deepwater fields started with ever increasing water depths. In order to enable

development a significant number of deepwater drilling units, be it ship shape or semisubmersible, have been built or are being

built at present. The present water depth range for these units is in general some 10,000 feet. Although higher water depth

capacities for deepwater drilling units are available, reality shows that the amount of subsea development wells reaching the10,000 feet limit is not that high and medium range depths, up to 7,500 feet are more common. Reservoir depths of up to

30,000 feet are not uncommon today in deepwater developments.Following the drilling and completion of deepwater wells (with hundreds of deepwater wells completed per year), one of the

upcoming needs is the intervention on deepwater wells.

There are two basic reasons for intervention:

1. To execute maintenance on existing wells when production is interrupted.2. To increase the extraction rate (ultimate recovery) from subsea fields to the same level as is done from more

conventional offshore fields.In order to address this matter, a ship shaped Well Intervention Vessel (WIV) was developed for the intervention on

deepwater wells. The design is developed utilizing the extensive experience gained over the last 40 years with the design of

mobile offshore drilling units whilst at the same time taking into account the specifics of well intervention. This paper

describes what was identified as a need, how this need was translated into a statement of requirements and how this statement

was translated into a fit for purpose design.

History about subsea WIV development

Though there is an increasing need for subsea well intervention and some dedicated units are available, in most cases a drilling

unit could be obtained at an acceptable rate if a dedicated unit was not available.

Subsea well intervention technology is still under development for deeper water, while the more mature market appears to be

in the North Sea with its shallow water depth. Several operators in the North Sea are using dedicated subsea well interventionvessels on a routine basis.

A structured commercial approach within operators to address problems with deepwater subsea wells was - and is - not

present. All work is judged from a reactive rather than a proactive perspective. The stumbling block is to have sufficient

subsea well intervention work on a reactive basis that can be contracted on an annual basis. A more pro-active approach, such

as applied by some operators in the North Sea, would change that.

Market analysis

With regard to the potential application of WIVs, a market research including the type of activities that can be done by a WIV

was executed.

The analysis was done by:

1. Obtaining commercially available studies of the well intervention market and reviewing same.2. Consulting operators and parties involved in the services rendered by a WIV and discussing views on future

requirements

3. Executing a desk research study

Many well intervention activities depend on the installed base of subsea wells in the various water depth ranges.

These are defined as follows:

Shallow 0 500 m Deep 500 1,500 m

Ultra Deep >1,500 m

Fig 1-1 shows the worldwide annual increase in subsea wells on-stream by water depth.

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0

100

200

300

400

500

600

700

2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014

NumberofWells

Shallow Deep Ultra Deep

Fig. 1-1 Number of Subsea Wells brough t On-stream by water depth 2004-2014. (Source: Infi eld Systems Ltd.)

There is a regional spread for subsea producing wells which is shown in Fig 1-2.

0

100

200

300

400

500

600

700

2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014

Numberof

Wells

Australasia East Asia Eastern Europe India Latin America

Middle East North Africa North America NWECS South & East Africa

South East Asia Southern Europe West Africa

Fig. 1-2 Number o f Subsea Wells brough t On-stream by Region 2004-2014. (Source: Infield Systems Ltd.)

On a cumulative basis the number of subsea wells on-stream is increasing vastly. Taking into account subsea wells which are

decommissioned Table 1-1 gives an overview of the subsea wells which are/will be producing in any given year between 2004and 2014.

Region 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014

Africa 260 327 435 542 674 772 817 889 948 1,067 1,218

Asia 115 119 116 127 147 169 171 181 217 249 279

Australasia 79 89 105 122 138 156 183 151 161 172 211

Europe 1,298 1,356 1,424 1,500 1,562 1,607 1,662 1,760 1,794 1,859 1,977

Latin America 566 605 650 709 753 818 884 958 971 1,050 1,069

ME & Casp. 36 37 37 37 41 45 47 47 51 59 63

North America 434 487 536 596 641 692 730 775 836 888 967

Grand Total 2,788 3,020 3,303 3,633 3,956 4,259 4,494 4,761 4,978 5,344 5,784

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Table 0-1 Operational Base of Subsea Wells 2004-14. (Source: Infield Systems Ltd.)Especially for Deepwater and Ultra Deepwater it is clear that Africa, Latin America and North America show the largest

increases in producing subsea wells.

Based on historical averages of executed work a future demand on subsea well intervention is projected for the various water

depth ranges. The demand is shown as vessel days in Fig 1-3.

0

1,000

2,000

3,000

4,000

5,000

6,000

7,000

2005 2006 2007 2008 2009 2010 2011 2012 2013 2014

Ves

selDays

Shallow Deep Ultra Deep

Fig. 1-3 Global Well Intervention Demand (Vessel Days) by Water Depth 2005 2014. (Source: Infield Systems Ltd.)

A further analysis shows that the requirement for subsea well intervention vessel days varies by region as shown in Fig 1-4.

-

1,000

2,000

3,000

4,000

5,000

6,000

7,000

2005 2006 2007 2008 2009 2010 2011 2012 2013 2014

Vess

elDays

Africa Asia Australasia Europe Latin America Middle East & Caspian North America

Fig. 1-4 Global Well Intervention Demand (Vessel Days) by Region 2005 2014. (Source: Infield Systems Ltd.)

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The conclusion is that the subsea well intervention market is developing while more subsea wells are brought on stream. From

the study it can be derived that for the Deepwater and Ultra Deepwater areas a substantial demand for capable well

intervention vessels is developing.

Just like for surface completed wells there exists a whole range of well intervention requirements for subsea completed wells.

Considering the occurrences of intervention requirements the breakdown is depicted in Fig. 1-5. The largest proportion of

intervention demand is associated with light interventions (such as borehole surveys, logging and stimulation).

BHSurveys/Logging19%

Stimulation

13%

SCSSVFailureTubingPullRepair9%

Set/PullTubingPlugs6%GasLiftValves

6%WaterShutoff

6%

Fishing4%

Tubing/PackerFailure7%

CasingLeakRepair4%

HorizSandControl7%

Re-Perforating2%

Perforating2%

RemedialCementing3%

ZonalIsolation2%

Others10%

Fig. 1-5 Subsea well in tervention requi rements demand as percentage of total. (Source: Infi eld Systems Ltd.)

Analyzing the demand on vessel days by type of subsea well intervention a steady increase is observed with medium to heavy

intervention roughly accountable for half of the total requirements. This is depicted in Fig. 1-6.

0

1000

2000

3000

4000

5000

6000

7000

2005 2006 2007 2008 2009 2010 2011 2012 2013 2014

VesselDays

Heavy Intervention Medium Intervention Light Intervention

Fig. 1-6 Global Intervention Demand by Vessel Days 2005 -2014. (Source: Infield Systems Ltd.)

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The number of vessel days is derived from an analysis based on the intervention requirement of an average subsea well on an

average year-to-year basis. This is shown in Table 1-2

Table 1-2: Well Intervention Services and Expected Vessel Days per Well per Year. (Source: Infield Systems Ltd.)

Preliminary Observations

The currently existing WIV fleet consists of vessels with a length of about 130 m maximum with a few slightly larger units.

Most vessels are smaller sized and are deployed for RLWI operations. These units are developed to operate in shallow to mid

range water depths; nearly no units are specifically developed for the Deepwater and Ultra Deepwater ranges.

From the studies mentioned above and consultations with operators it became clear that there is a high potential for a numberof deepwater and ultra deepwater WIVs.

However, the following observations are associated with the development of these units for the market.

1. Development of hydrocarbon deposits takes place on a project to project basis where the field is developed andhanded over to an asset owner. After startup of production, no overall authority for well intervention is present withinthe major operators consulted, with scarce exceptions. Asset owners cannot be aligned with regard to an integrated

approach for well intervention due to internal company structures, partners and national borders. As a result, there is

no single authority within the operator for interventions and no overall budget plan can be made validating the long

term hire of a WIV.

2. Subsea development of reservoirs is to a certain extent defined by reservoir characteristics and available subseatechnology at that time. As a result each subsea development differs both in installed equipment (where thecharacteristics of well fluids are concerned) and the period in which the field was developed.

Average Expected Vessel Days/ Well/Yr

Services Light Medium Heavy

Borehole surveys/logging 0.30 0.30 0.30

Casing leak/repair 0.00 0.06 0.06

Electrical Submersible Pumps 0.00 0.00 0.03

Fishing 0.00 0.06 0.06

Fluid displacement 0.02 0.02 0.02

Gas Lift Valves 0.09 0.09 0.09

Horizontal well sand control 0.00 0.00 0.11

Paraffin/Asphaltenes/Hydrates 0.00 0.02 0.02

Perforating 0.04 0.04 0.04

Plug & Abandon well 0.00 0.01 0.01Remedial cementing 0.00 0.05 0.05

Re-perforating 0.04 0.04 0.04

Sand control/gravel pack 0.00 0.02 0.02

Sand washing 0.02 0.02 0.02

SCSSV failure (tubing pull repair) 0.00 0.14 0.14

SCSSV failure (wireline repair) 0.00 0.04 0.04

Setting/pulling tubing plugs 0.09 0.09 0.09

Stimulation 0.21 0.21 0.21

Tubing/packer failure 0.00 0.00 0.12

Water shut-off 0.00 0.09 0.09

Zonal isolation 0.03 0.03 0.03

Total 0.84 1.33 1.59

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3. Consequently a WIV has to be highly flexible with regard to deck space for third party services, location there-off onthe vessel and available utilities for 3rd party services. In addition to this the question is which well services

equipment should be owned by a 3rd party and of temporary nature and which equipment should be owned by the

vessel owner. Even ownership by a vessel owner is possible in combination with regard to 3rd party equipment.

With the above in mind the focus for the project became the development of a WIV for deepwater and ultra deepwater

operations supporting all type of intervention operations with the exception of riser based tubing change outs for tubing strings

with large bore hangers. Up to now, the latter requires a full size deepwater drilling unit.

Also, additional functionality, e.g. tophole drilling, was created to make investment in the WIV attractive for a vessel owner in

view of utilization days.

Subsea Well Intervention categories

In general 3 different categories of subsea well intervention can be identified:

(I) Light well intervention (Also referenced as type I or class A in literature)Light interventions are serviceable using a variety of equipment that can be deployed from numerous types of vessels.The types of operations can be identified as:

Bore hole surveys/logging Fluid displacement Gas lift valve repair Perforating

Re-perforating Sand washing Setting/pulling tubing plugs

Stimulation

Zonal isolation(II) Medium well intervention (Also referenced as type II or class B in literature)

Medium intervention requirements are in general more specialized than the light types. Some are related to the

production issues while others refer to safety issues. Examples are:

Casing leak repairs Fishing Paraffin, asphaltenes, hydrates Plugging abandoned well Remedial cementing

Sand control/gravel packing SCSSV failure Water shut-offs

(III) Heavy well intervention (Also referenced as type III or class C in literature)The traditional definition of heavy well intervention typically is associated with the deployment of drilling rigs.

Examples are:

Tubing packer failure ESP replacement

Horizontal well sand control Well completion change out

Re-drilling side tracks Subsea Christmas tree change out

For type I light well intervention vessels are used for intervention services requiring riserless wireline (WL) operations, or

derivatives of this technology (RLWI). This is a mature market where existing technologies are used and new technologies aredeveloped at the same time. The type of vessels used for RLWI operations are smaller sized, typically supplier type vessels,

where a temporarily installed package can be used to deploy WL over the side using a subsea lubricator or other means to

safely access the well. At the same time, this technology is used in combination with more demanding technology, such as

coiled tubing (CT) operations, on larger dedicated intervention vessels.

For type II medium well intervention vessels are used for more demanding techniques such as coiled tubing (CT) operations

where fluids are pumped through a coil into the reservoir or used to drive certain components. CT packages are more

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demanding in space requirements than WL packages resulting in a larger vessel size. Often the WL and CT techniques are to

be combined to address the requirements of an intervention. With CT operations the requirement may be for work where well

returns are coming back to surface and need to be cleaned and or treated on board of the vessel. In these cases a riser based

system will be required to create a flow path whereas with more limited operations a subsea lubricator can be deployed.

For type III Large vessels are used for heavy intervention operations, such as the change out of production tubing. In these

types of operations, the pulling of the tubing hanger is required. Due to the diameter of the tubing hanger a riser is used of such

substantial diameter that the deployment of a deepwater drilling unit with full size subsea BOP stack is required. To date thesesize requirements make this type of operation no-go territory for the development of a smaller cost efficient well intervention

vessel.

It should be noted that for all of the above types of well intervention, due to the nature of the work, the deployment of

dedicated staff, with well intervention experience is preferred. Especially since different skill sets are required for each type of

activity. (e.g. WL, CT). These skill sets are not, as a rule, encountered amongst staff on board of regular drilling units.The above makes the use of deepwater drilling units and subsea construction vessels less desirable considering the nature and

the anticipated increase in subsea well intervention work.

Design approach

For reference the way a design is generally developed is summarized.

Over time a stepped approach has evolved when developing a new vessel class, this approach is sequenced in a number of

phases narrowing down the design whilst maintaining maximum flexibility for the future vessel owner.Not cast in stone, the following phases can be identified when a design is developed:

Data acquisition phase.Prior to the design phase the market is reviewed, potential clients and other operational stakeholders are identified.

The review and results of consultations will give initial requirements for the design of the unit. These requirements

define the data for the initial size of the vessel and a sketchy operational layout.

Concept design phase.Two tracks are possible; the first one is the development of an in-house design, based upon expected market

developments. This track leads to a generic design where maximum flexibility is included. The second track is more

focused. This takes place when a client is involved with more specific design and operational requirements.

During the concept design phase the requirements are laid down in a Basis of Design (BOD) document. This outline

document states the requirements for the vessel both from naval as well as operational requirements and is used asguidance by the design team. The result of the concept design phase is a set of deliverables consisting of general

arrangement drawings, a specification, an equipment list, and primary checks with regard to vessel strength and

stability. This set provides sufficient data for a yard to quote a first indicative price for the unit, which should be

adequate for a client to decide to continue or abandon the project. In some cases an extended concept design is

developed which is significantly more detailed but not at the level of a basic design.

Basic design phase.The basic design phase takes the design down a much more detailed level where all drawings, documents and reports

are prepared to take the design to class approval level and results in a set of deliverables detailed enough for a yard to

quote a fixed price and delivery schedule to a client and develop a set of construction drawings to build the vessel.

WIV Basis of Design

In parallel with the WIV, a vessel design was under development within the design office.This vessel type is named Constructor Class. The Constructor Class is specifically developed to address the offshore industrys

needs for oil and gas development projects in deeper waters. This particular vessel is developed for activities such as subsea

construction, IRM, flex-lay and S-lay. This class has the following key elements:

The vessel was built around a concept for a range of platforms, starting at 155 m length and 30 m width onto whichdifferent systems could be fitted. Key characteristics are a large accommodation forward, the possibility to include a

large moonpool and a smaller moonpool, and a large deck to support the activities for which the vessel is designed.

The class shares a hull shape designed with good sea keeping capabilities and low resistance in transit. The vesselarrangements are laid out with DP-3 in mind.

The design is developed to operate in deep water for prolonged time in remote areas with a short mobilization time. The latest HSE requirements have been taken into account, specifically where working environment and

environmental requirements are concerned.

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It was concluded that the Constructor Class vessel design is well suited as a base case for the WIV design.

With the above benefits of this class, combined with the statement of requirements resulting from market review and client

consultations, a Basis of Design was developed for the WIV containing the following key elements with regard to

classification and operation:

Classification:

Classification (DNV): 1A1Ship-shaped Well Intervention 2 Unit CRANE DRILL DPS-3 E0 WELL-1Optional: CLEAN DESIGN COMF-V(crn)C(crn) HELDK-SH OPP-F WELLTEST BIS (N) BWM-

T NAUT-OSV(A) DK(+) SILENT-E

(Equivalent ABS or other Classification is possible)

Operating area:

The vessel is capable to work worldwide with special focus on conditions existing in the Gulf of Mexico, Brazil, West Africa,North Sea and Southeast Asia.

Operating Profile:

Capable to execute intervention operations by means of WL or braided line

Capable to execute intervention operation by means of CT in combination with a subsea lubricator or a riserdeployed subsea package

Capable to execute tubing change out operations on suspended wells without a riser system (riserless completionrunning and retrieval)

Capable to execute tophole drilling operations Capable to execute well capping operations with fluid transfer to standby tanker Capable to execute plug and abandon work Capable to execute deepwater installation

Capable to execute deepwater repair, inspection and maintenance on subsea equipment

(Though intervention is the main goal of the unit, the design will facilitate other activities related to intervention in the broader

sense making the WIV more attractive from an economic point of view)

Resulting Vessel design

Vessel layout and construction

The vessel is shown in figures 2.1 thru 2.8 in appendix 2, showing part of the GA and 3D renders.

HullAt least the following functional spaces and areas will be arranged below main deck:

Propulsion rooms Engine rooms Workshops & stores

Switchboard rooms Pump rooms Sack store & mixing area

Mud pump room Accommodation spaces for 150 POB Dedicated anti heeling and anti rolling tanks will be incorporated in the design.

Main deck and upwards

At least the following functional spaces and areas will be arranged above main deck:

Well testing area

Third party areas Riser storage Tubular storage ROV storage & control areas

Subsea package and Christmas tree storage, testing & handling area Substructure, drill floor & derrick Mud treatment area

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Subsea facilities (including well control equipment)

Workshops & stores Accommodation

Moonpool

A moonpool, surrounded by cofferdams, will be incorporated in the design. The moonpool dimensions will ensure that

(subsea) tools and equipment will not collide with the moonpool sides during deployment / retrieval operations.

Furthermore, the moonpool dimensions will allow for the total riser angle (static heel and dynamic roll) of 10 degrees.

Substructure & Drill Floor

The substructure will support the drill floor and the derrick. The height of the substructure will be sufficient for handling of

BOPs, Christmas trees, well intervention equipment and tools with a package height of maximum 12 m.

ROV Superstructure & Work DeckThe ROVs will be fully integrated in a superstructure aft of the substructure; the ROVs will be launched over the side and will

be arranged in dedicated hangars. The superstructure will allow for skidding (cursor system) of subsea equipment from the aft

deck into the moonpool area. On top of the ROV superstructure a multi functional work deck will be provided at rig floor

level.

Construction

The hull will be subdivided into watertight and non-watertight compartments by means of longitudinal bulkheads, transverse

bulkheads and decks. The vessel will have a double bottom and double hull.

A longitudinal framing system will be applied supported by transverse web frames. A forward collision bulkhead extending up

to main deck will be provided. The vessel will be outfitted with a forecastle deck extending over

The following main parameters, dimensions and capacities are derived:

Main parameters

Maximum water depth : 3,048 m (10,000 ft)

Maximum well depth : 9,144 m (30,000 ft MD) below mudline located at 3,048 m below sealevel

Operational condition : Sign. Wave height between 4 to 7 m at wave peak period 5.0 16.0 s

Wind 10 min. mean 20 m/s

Current speed 1.5 m/s (3 knots)

Min/Max T(seawater) : 0/32C

Min/Max T(ambient) : -10/40C

Design speed : 16 knots

Design life : 20 years

Station keeping : DP system compliant with IMO DP3 notation

Autonomy : 45 days based upon 5 days mob/demob and 35 days operation

(This can be increased depending upon requirements)

Dimensions

Length over all : 150 m

Width : 28 m

Design draught : 8 m

Operational LoadsStatic hook load : 680 mt

Riser tension load : 816 mt

AHC crane load : 400 mt

Variable load : 5,000 mt

Capacities

Marine Diesel Oil : 1,800 m3

Fresh water : 1,200 m3

Potable water : 1,500 m3

Active/Reserve fluids : 1,080 m3

(Pits for well intervention purposes)

Reserve brine : 450 m

3

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Methanol : 200 m3

Bulk mud/cement : 240 m3

(4 pods total)

Mixing area pallets : 70 (double stacked)

Tubulars

Intervention riser : 3,048 m 11. (base case, storage space for a system up to 16 available)

Drill collars/ 9. : 165 m

Drillpipe 6.5/8 : 5,532 mConductor 30 : 300 m (for batch setting several wells)Surface casing 20 : 2,000 m (for batch setting several wells)

Tubing 4. : 9,144 m

(Numbers are typical, storage depends upon deck configuration)

Operational areas

Main deck : 1,150 m2

Rig floor : 400 m2

Wire line unit : 160 m2

Coiled tubing unit : 280 m2

Subsea package : 250 m2

(The areas to be arranged such that no activity shall be blocked by any other activity causing delays in rigging or secondary

equipment handling, with the exception of the rig floor area)

Operational philosophyGeneral

The vessel will use its own propulsion system for sailing. On location the vessel will use its own DP system for station

keeping and is allowed to weathervane and choose optimum heading in the environment.

The vessel will operate autonomously: all consumables and (support) functions need to be provided on the vessel for the

duration of operation(s) to be performed. Support vessels can be used to re-supply (load consumables and offload waste) the

vessel, without disturbing operations, using vessel crane(s).

Well intervention operations are done through the main moonpool: operations (including ROV operations) should not interfere

with the DP system / thrusters. Some operations (e.g. subsea installation, maintenance and repair) can be done over the side

using the active heave compensated crane. Depending upon vessel requirements a secondary moonpool can be included.Well intervention operations can be continued until environmental responses (motions, accelerations and loads) reach the

operational limits of the vessel and its equipment. The vessel can either stay connected to the well (stand-by) waiting on

weather or disconnect in case of riser based operation. After disconnection the vessel can either stay in the field (in-field

survival) or sail. In case of an emergency situation (e.g. well control situation) there will be an emergency disconnect.

The above differs per operational area and is dependent upon equipment deployed as well as operator developed procedures.

Well intervention classes addressed by the vessel

The vessel is designed for the following well intervention classes:

A: intervention by means of wireline or braided line operations in combination with a subsea lubricator

B: intervention by means of coiled tubing operations and a subsea lubricator

B+: intervention by means of coiled tubing operations and a deployed subsea package and riser system

Although the WIV is initially targeted at operations up to and including class B+ type of well intervention operations, the

vessel is also designed for riserless tubing retrieval and running capability or tubing running/retrieval in combination with aslimbore wellhead system.

Vessel applications

The well intervention vessel is developed primarily to execute all types of work on subsea wells and associated infrastructure

to a water depth of 3,048 m (10,000 ft).

The following well intervention and subsea related operations are targeted by the design.

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Well Intervention

The vessels primary goal is intervention on existing wells, thereby extending the life of the well. Typical activities are repair

and planned maintenance on the infrastructure of the well as well as the Christmas tree or electrical submersible pump system

associated with it. In order to execute these activities the vessel will be fitted with the following equipment:

Rig package to support intervention equipment installed, such as coiled tubing and wireline equipment.

Subsea intervention package deployed from a handling system with adequate space for running and retrieval of apackage complete with attached Christmas tree.

Riser system to connect the subsea package to the rig floor substructure as guide path forintervention activities andreturn flow path in case pumping of fluids is required.

Allocated space for a wireline package at rig floor level.

Allocated space for a coiled tubing setup at rig floor level with additional equipment for temporary activitiesassociated with coiled tubing operations.

Well fluids pumping package of adequate capacity to handle the volumes in a completed well at 3,048 m (10,000 ft)water depth with a maximum well depth of 9,144 m (30,000 ft)

Cement unit package for cementing operations ROV package (2) to assist in intervention operations at a maximum water depth of 3,048 m (10,000 ft). Large deck area to facilitate space for all other equipment associated with intervention operations.

Riserless Completion Running

Riserless completion retrieval and running is a new type of activity presently under review and development by variousoperators and well service companies. This approach removes the requirement for a class C operation by installing temporary

barriers between the reservoir and the well bore. With this approach and the provided equipment the WIV 10,000 is fully

capable of retrieving and running tubing strings complete with hanger.

Riser Based Completion Running

Riser based completion running involves the retrieval and running of completion strings, in general tubing strings, or ESP

strings, by means of the deployment of a subsea package on a riser. Such operations can take place on wells and subsea based

first stage separation or pumping systems. The vessel will be laid out to deploy such a package / riser combination for various

configurations of wellhead bore and water depth.

Through Tubing Rotary Drilling

One of the intervention activities envisaged is extending the flow path in an existing well over a minor distance and limited

diameter to enhance / improve well production performance. This can be achieved by drilling with a coiled tubing unit throughthe tubing. In order to achieve this, a dedicated treatment package can be installed consisting of the following equipment:

Shale shakers (2) to remove the cuttings from the return well fluid Desander / desilter unit to remove sand and silt fractions from the return well fluid Vacuum degassers to remove adsorbed (or associated) gas from the return well fluid

Associated treatment tank packageOther equipment required for this type of operation such as centrifuges and cuttings treatment will be temporary equipment

installed on deck. Piping will be permanently installed between the fixed package and this equipment to facilitate easy and fast

hookup.

Extended Well Testing

Normal well testing after intervention and extended well testing operations can both be performed on the vessel. Produced gas

will be flared; produced oil will not be stored in the vessel itself, but on a support vessel moored, or dynamically positioned,

close by.Extended well testing will require connecting to a well by means of a top tensioned production riser, suspended in the

moonpool with or without termination at rig floor level.

The produced fluids or gas are transferred to the well test system by means of a flexible and hard piping which is permanently

installed. These tests typically have duration of several weeks up to a few months and are carried out to assess reservoir

parameters.

Tophole DrillingThe vessel will be equipped to batch execute tophole drilling operations for field development and installing the well

infrastructure (up and including to the subsea wellhead). Upon completion of the tophole section the well will be suspended

for future development by a deepwater drilling unit.

In order to do this the vessel will be fitted with a portable topdrive system and fluid pumping system of adequate capacity to

deliver well tophole sections with the string attached to the subsea wellhead, which can be set at a shoe depth down to

typically 600 - 800 m (4,921 - 6,562 ft) below the mudline.

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Drilling will be done with 75 ft singles; well tubulars will be supplied in singles as well.

Well Capping

An important aspect of rig operations is the capability to execute well capping operations to stem the flow coming from an

uncontrolled blowout at seabed.

The vessel has the capability to collect and install well capping devices located in strategic places around the world and deploy

these devices on a short term basis on the stricken well. The extended well test setup will be used in combination with the

capping device to redirect the flow to a nearby storage vessel, or existing subsea infrastructure, for further transfer to shorewhilst other units are developing relief wells.The vessel is also well fitted to be used as a base to execute wild well control operations in case of other blowout scenarios.

Plug & Abandon

Plug and abandon operations can be executed by the vessel once the life of the well has been completed and regulatory

requirements demand that the well is closed off with a permanent number of barriers, separating the reservoir from the

environment. Steel is partially removed from the well, including the wellhead to a certain level below the mudline. This

activity also requires removal of the seabed infrastructure associated with the well. Such activity requires the application of the

deepwater installation crane or the derrick for infrastructure retrieval, the derrick package. The cementing system is required

for setting the plugs and the derrick package and rotational equipment for cutting and retrieving casing strings.

Deepwater Installation/Retrieval

Deepwater installation includes the installation and removal of seabed infrastructure and well related equipment residing at theseabed. Both the vessels rig package as well as the crane can be used. The difference is that the rig package can handle

packages of smaller size, compared to the crane but does have pumping and rotation capacity associated with it, whereas the

crane handles larger loads, deploying these from the deck over the side.

Business model/present status

As mentioned in one of the previous sections, the main challenge for the concept of a deepwater intervention vessel is finding

a financing model to develop and build the unit. As a rule, deepwater units are built against a fixed rate for a set period,

typically a number of years. In the case of a well intervention vessel this is a challenge since no intervention project spans a

number of years. The additional problem is the way the operators are structured, where no single point responsibility is present

for integrated intervention.A possible way to overcome this is to develop an alliance between a vessel owner, a main 3rd

party service provider and a

deepwater technology supplier. Such an alliance can offer an operator a viable option for the execution of well intervention

activities.

The present status for the concept is that presentations and discussions take place with various interested parties in the

industry.

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Appendix 1: Vessel Intervention Equipment Package

This appendix contains key intervention equipment data for the present stage of the well intervention vessel.

Derrick

The derrick will have the following characteristics:

Height under water table: 36.6 m (120 ft) Static hook load: 680 t (1,500 kips)

The derrick will include a block guide rail system to support a portable top drive system and dedicated active heave

compensator system. Guidance systems will be installed to support wireline and CT operations. The V-door height is adjusted

for wireline, coiled tubing operations and to support the height of 75 feet riser and drill string joints.

Tubular Storage

The riser and work string storage will be suitable for:

Risers: 22.86 m (75 ft single joints) Work string: 22.86 m (75 ft single joints)

Other tubulars, maximum range III @ 13.72 m (45 feet) will be transferred to the rig floor by means of a transport cart located

on an elevated work deck aft of the rig floor and subsea package storage positions. The selection for 75 ft singles is based upon

maintaining optimum tripping speed whilst operating a singles system.

Hoisting & Heave Compensation

The hoisting function at the well center will be provided by a 680 t (1,500 kips) drawworks. Heave compensation will be done

by means of an active heave system mounted in the derrick, optionally an active heave drawworks system can be fitted.

Subsea Package System & Christmas Tree handling and dimensioningThe vessel will allow for the following maximum subsea package dimensions and weight:

Length : 7.0 m Width : 7.0 m Height : 12.0 m

Combined package weight : 180 t (397 kips) Max. unit weight for gantry crane : 100 t (265 kips)

Typically a package consists, (in case of tree running), out of, of (top to bottom): lower riser package (LRP) emergency disconnect package (EDP)

Christmas tree or a dedicated subsea intervention package.

Though earlier in the text an intervention riser size of 11 3/4 is listed, the maximum package size for which the unit will be

designed is based upon 13 5/8 internal diameter, thereby facilitating access to slimbore wellheads as well as a potential for

surface BOP operations whilst maintaining flexibility for future applications.

Hence the vessel is designed around a 13 5/8 10K surface BOP system with Environmental Safe Guard as ultimate

intervention package.

A multiplex (MUX) subsea package control system with 2 MUX reels and a hotline reel will be provided.

Additionally space for an intervention and workover control system (IWOCS) reel will be provided.

Riser System

A marine riser system matching the possible 13 5/8 subsea package with equivalent working pressure can be provided, with

the following characteristics:

Riser OD: 0.41 m (16.0")

Riser ID: 0.38 m (15.1)

Nominal joint length: 22.86 m (75 ft) Maximum joint weight: 4.3 t Storage space for number of joints: 134

Additionally space for pup joints and 2 telescopic joints of 50 ft stroke is allocated.

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Riser Tensioning System

The vessel will be equipped with a wireline riser tensioning system comprising of the following main components:

6 double wireline tensioners with a maximum capacity per tensioner of 68 t (150 kips) totaling to 816 t (1,800 kips) 12 idler sheaves Riser tensioning ring with diverter adapter (stroke)

Maximum riser tension load will be based on one pair of installed riser tensioners out of service. It will nevertheless be

possible to operate with 12 tensioners simultaneously

Bulk system

The bulk system will comprise the following:

Bulk mud material each 120 m3 (2,120 cft)

Bulk cement material 120 m3 (2,120 cft) Surge tanks for bulk mud and bulk cement Dust collectors Connection between bulk systems, separated by spectacle flange

A ventilated sack storage area of 120 m2 will be arranged

Mud and fluid system

In general the WIV will operate with intervention fluids, typically brine based. During some operations seawater (tophole

drilling) or mud (TTRD) will be pumped, hence this system is called mud and fluid (intervention) system. Where applicablethe term mud is used for ease of reference, even if the equipment is processing fluid.

The mud and fluid circulation system will comprise the following:

2 Quintuplex HP fluid pumps of 2,273 kW (3,000 hp) each with 7,500 psi WPOr 2 Triplex type mud pumps of 1,640 kW (2,200 hp) each with 7,500 psi WP(Room is allocated for an optional 3

rdpump in case the vessel is more designed towards drilling operations)

7,500 psi standpipes and standpipe manifold

The mixing system will comprise the following:

2 mixing and transfer pumps 1 mixing hopper 1 sack slitting machines Big bag station Chemical additive unit Caustic mixing unit Agitators in all (active and reserve) fluid storage tanks High rate mixers

High pressure (HP) shearing units Fresh water and brine transfer pumps Fluid filtration equipment

The mud treatment system will comprise the following:

2 shale shakers 2 degassers

1 desander / desilter set 1 sets of mud treatment tanks

Cuttings management will be according to the controlled discharge philosophy. Provisions will be made for a cuttings blower,

centrifuge, dryer system and cuttings storage silos, with a total working volume of 60 m3 (2,120 ft3).

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Lifting and handling systems

Cursor system:

A cursor system, consisting of skidding tracks and carts, will be installed on main deck; the cursor system will be the primary

means of handling of (subsea) equipment.

Cranes:

Cranes will be provided as secondary means of handling.The cranes will be able to transport supplies from a supplier to the vessel and vice versa. The number, size and type of craneswill depend on the layout of the vessel. A suitable number of laydown areas will be provided throughout the vessel; doors,

hatches, openings, etc. will be provided as necessary.

One knuckle boom crane will be provided aft of the derrick, with a capacity of 400 t (SWL), deepwater loweringcapability and a heave compensated system.

One small knuckle boom crane will be provided forward of the rig floor for logistics and support of the forward deck.

Other:

Various lifting and handling equipment will be provided on the drill floor and in the moonpool area.

Third party equipment packages and allocated spaces

The vessel design will include provisions for the fitting of third party equipment; distinction will be made between

(semi)permanent and non-permanent, temporary, systems. Depending on the type of operation(s) to be performed third party

equipment is taken on board. Space, utilities and access for the following third party equipment will be considered.

Permanent systems

Permanent 3rd party equipment sets are systems that are installed on board on a long term contract, typically lasting years.

These equipment types are used with all type of intervention systems and are, though not owned by the vessel owner, part of

the vessel as an operational entity. These equipment sets are fully integrated in the vessel and connected to all required vessel

utilities and systems.

ROV systems

Two work class ROV systems will be installed to be deployed over the side with a cursor guide system. The ROV systems will

be rated for 3,048 m (10,000 ft) of water depth and comprise each: Remotely operated vehicle (ROV) Tether management system (TMS) / side entry cage

Cursor (removable) A-frame Umbilical winch & sheave Hydraulic power unit (HPU)

Guide rails ROV controls ROV workshop

Cement unit

One independent AC electric or diesel driven cement unit will be installed, including batch mixer, liquid additive continuous

metering system, surge tanks and dust collector. Piping and tanks for chemicals will be provided; piping will be arranged to

supply seawater and drill water and to pump from and to the active and reserve tanks.

Coiled tubing unit

One coiled tubing unit and associated equipment will be installed. The coiled tubing unit will be located near the CL of the

vessel, aft of the derrick on drill floor level, in proximity to the drill floor.

Wireline logging unit

One wireline logging unit and associated equipment will be installed. The wireline logging unit will be located near CL of the

vessel, in proximity to the drill floor.

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Non-permanent systems

Non permanent systems are 3rd party equipment packages that are installed on the vessel over a short period, typically weeks,

for a specific project. An example is a mud logging unit which comes on board for the duration of a TTRD operation.In order to install this type of equipment quickly and efficiently, provisions are made that facilitate this process.

Typical provisions, depending on the type of equipment, are:

Fixed allocated space for the 3rd party equipment

Support structures and / or connection points, container dimension based

Power outlet of the right voltage and frequency IT interface to vessel system for data transfer Communication connections

Fresh water supply Rig air supply Dedicated fixed piping between the rig floor and the allocated space, depending upon the type of equipment installed.

In general a 3rd party data book will be created by the vessel owner for these equipment types, giving the owner of the 3rd

party equipment data to prepare his equipment for installation on board.

Mud logging unit

Provisions for a mud logging unit will be provided. All required utilities such as power, water and air will be available at the

planned location. The mud logging unit will be located in proximity to the mud treatment area, as far as convenient in thelayout; easy access for installation and removal will be provided.

LWD / MWD unit

Provisions for a LWD / MWD unit will be provided. All required utilities such as power, water and air will be available at the

planned location. The LWD / MWD unit will be located in proximity to the drill floor, as far as convenient in the layout; easy

access for installation and removal will be provided.

Well testing equipment

Part of the common work deck area will be made suitable (drainage) for (extended) well testing operations. The equipment

will consist typically of, but not limited to, a choke manifold, safety valve, steam generator, heat exchanger, separator, gauge

tank, transfer pump, fuel oil pump and compressor. A 4 15,000 psi working pressure H2S rated well testing line from the rig

floor to the well test area will be provided for equipment installation.In case of extended well testing a different setup will be used, which is field specific. The offloading reel, for returning

produced well fluids to a neighboring vessel, will be arranged on the common work deck area suitable for well testing

operations.

Burner Booms

Provisions (foundations & connections) for one self-bearing hinged burner boom will be provided, with minimum length of 25m and overboard burner. The burner boom is to be located close to the well testing equipment on the common work deck area

with the following piping and swivels:

Gas swivel Oil swivel Diesel swivel

Water swivel

Air supply Butane supply Test separator PSV relief line

Surge tank vent line

Line for electrical lighter Mist former system

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Appendix 2. Vessel renderings

Figure 2.1 WIV from PS forward

Figure 2.2 WIV from PS aft

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Figure 2.3 WIV from SB side

Figure 2.4 WIV from top

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Appendix 3: References

1. GLOBAL PERSPECTIVES - Subsea Well Intervention Market Update Report To 2014 Published By InfieldSystems Limited