U-CR-001r1

NORSOK STANDARD

COMMON REQUIREMENTS SUBSEA STRUCTURES AND PIPING SYSTEM

U-CR-001 Rev. 1, January 1995

Subsea Structures and Piping System U-CR-001Rev. 1, January 1995

NORSOK Standard 1 of 24

CONTENTS

1. FOREWORD 2 2. SCOPE 2 3. NORMATIVE REFERENCES 2 4. DEFINITIONS AND ABBREVIATIONS 3

4.1 Definitions 3 4.2 Symbols and abbreviations 3 4.3 System Definition 4

5. TECHNICAL REQUIREMENTS 4 5.1 General guidelines 4 5.2 Overall Requirements 4 5.3 Requirements for Structures 8 5.4 Requirements for Manifold and Piping System 11 5.5 Requirements for Replacement Devices 14

ANNEX A Subsea Data Sheet (Normative) ANNEX B National Regulations (Informative)

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1. FOREWORD This standard has been developed by the NORSOK Standardisation Work Group. ANNEX A is normative. ANNEX B is informative.

2. SCOPE

The purpose of this standard is to the minimum requirements to subsea structures and piping systems.

3. NORMATIVE REFERENCES

Rules, regulations and standards The latest edition and current amendments of the following regulations and standards shall apply, where relevant, at the time of order placement: ASME B31.3 Chemical Plant and Petroleum Refinery Piping ASME B31.4 Chemical Plant and Petroleum Refinery Piping DnV Rules for submarine pipelines, 1981 ISO 10423 Specification for Wellhead and X-mas Tree Equipment

(replaces API 6A) API 6D Specification for Pipeline Valves, Steel Gate, Plug, Ball and

Check Valves (To be replaced by ISO 14313) API 14D Wellhead Surface Safety Valves and Underwater Safety

Valves for Offshore Service (To be replaced by ISO 10433) NORSOK Standards: U-DP-001 Principles for design and operation of subsea production

systems U-CR-005 Subsea Production Control System U-CR-007 Intervention System J-CR-003 Marine Operations U-CR-001 Colour and Marking M-DP-001 Material Selection U-CR-003 Subsea X-mas tree system.

Data sheets Project specific requirements are defined by use of a relevant selection of the following NORSOK data sheets.



The following data sheets are specific for U-CR-001: UDS-A03 Load Matrix UDS-A05 Drilling loads - Default values UDS-A06 Dropped object loads UDS-A07 Design against fishing gear/overtrawlability UDS-A08 Design of hatches A data heet outlinging the Test Requirements should also be developed. Dummy data sheets including default values are attached in ANNEXA. For the following general data sheets, reference is made to the other NORSOK Subsea Standards: UDS-A01 General Field Data UDS-A02 Production requirements/reservoir management UDS-A04 Environmental Data It is considered favourable that datasheets covering the following areas should also be developed for a specific field development: • Intervention Strategy • Guidewire anchor and guidepost locking mechanism • ROV torque tools. • Thermal Expansion Data • Flowline data • Control system design data • Condition monitoring • Process flowcharts • Operational requirements • Wellstream composition • Simultaneous operations

4. DEFINITIONS AND ABBREVIATIONS

4.1 Definitions

Reference is made to the general list of definitions given in U-DP-001.

4.2 Symbols and abbreviations

For definition of symbols and abbreviations used in the text, reference is made to U-DP-001.



4.3 System Definition

This standard covers the subsea structures and piping systems (template and satellite structures, manifold and riser base structures, protection structures, piping modules). This subsystem interfaces with all of the other systems in a subsea production system, ref. U-DP-001. This standard is intended to give general requirements and should cover both shallow water, deep water and very deep water; diver systems and diverless systems; guideline and guidelineless systems; overtrawlable and non-overtrawlable systems, etc. Supplementary data sheets defines special requirements to the actual application.

5. TECHNICAL REQUIREMENTS

5.1 General guidelines

The subject standard is a part of the NORSOK system of standards, and should be read with this in mind for instance will special requirements set to the structure by the marine operations be defined in J-CR-003, material selection is covered in M-DP-001, colour and marking requirements in U-CR-001 and intervention systems in U-CR-007. The standards are supplemented by data sheets as required to specify the actual application.

5.2 Overall Requirements

5.2.1 General

The following functional requirements shall generally apply for the subsea structure and manifold system: • The design life of non-retrievable equipment shall be equal to or exceed the specified

field lifetime. • In areas where this is required, a method for removal of or prevention of any damage

or inconvenience caused by the subsea structure and manifold system upon field abandonment shall be developed. The design life and structural integrity of the structure shall allow for this operation.

• The subsea structure and piping system design shall comply with the intervention

strategy. • Requirements for protection against fishing gear and overtrawlability is project

specific, ref data sheet UDS-A01.



5.2.2 Intervention

The following requirements shall apply to the subsea structures and piping system in order to facilitate efficient intervention: • Suitable viewing positions shall be provided for observations during running,

connection and operation of tools, modules and equipment. • Suitable landing area and/or attachment points shall be provided where manipulative

tasks are required carried out. • Sensitive components/items on the subsea structure which may be damaged by the

intervention system shall be protected. • For entry of ROV operated tools onto valve spindles, a ROV landing frame or ROV

attachment points shall be provided. The frame shall not obstruct the access for visual inspection of the piping. The valves spindles/docking receptacles shall then be located a suitable distance below/behind the ROV platform/frontplate/grating such that the torque tool can interface with the valve.

• Minimum two buckets, designed for easy replacement of acoustic transponders shall

be provided diametric opposite on top of the structure. Acoustic shielding and potential snagging shall be avoided.

• The landing- and surrounding areas shall be designed to withstand loads imposed by

the respective intervention system during landing and operation. • All locking mechanisms on protection hatches and lifting frames shall be easily

operated according to the defined intervention strategy. • All guideposts shall be replaceable using locking mechanisms easily operated by the

selected intervention system. • A design based on running retrievable modules, structures and equipment on a

guidewire system, shall be in accordance with the required project standard, including guidepost top design with respect to guidewire anchor system and guidepost locking system.

• All permanently installed guideposts which require guidewire attachment must have

through bore to allow passage of the guidewire anchor. • Any special equipment or arrangements installed on the subsea structure, which

requires torque to be applied during operation, shall be designed to use the required project standard torque tool and interface.

• The design shall be such that location of anodes and other construction details do not

represent any obstruction or snagging point for the selected intervention system.



• For guidelineless intervention systems a proper guiding system shall be provided. The

guiding structure shall be designed for relevant operational impact loads. • Tools, BOP, modules and all retrievable equipment shall have an adequate running

clearance to any part of the structure, adjacent module or equipment etc to avoid any unintended impacts or clashes during installation and retrieval: − minimum 0,2 m while running on guideposts − minimum 1,0 m for monohull and 0.5 m for semisubmersible operations,

respectively, at 0.8 m above guidepost top and upward when running on guidewires. Tighter clearances can be accepted for final alignment.

• Operational requirements for running intervention systems from vessels, necessitating

offset angles on the guidelines, shall not restrict ROT access, reduce running clearances or otherwise deteriorate operational safety and reliability.

• The subsea system shall enable any guidewire based ROT to be run vertically along

guidewires and guideposts onto the dedicated landing area. • The subsea systems shall be designed to provide sufficient access and manoeuvring

space to allow the ROV systems to perform the required work at the different task sites (U-CR-007).

For further details conserning requirements set by the intervention operations reference is made to U-CR-007.

5.2.3 Material Selection and Corrosion Protection

Material selection, fabrication and corrosion protection shall comply with the requirements in the NORSOK standard for material selection (M-DP-001). A corrosion protection system based on a combination of surface coating and cathodic protection shall be included in the design of subsea structures, manifolds and modules exposed to ambient seawater. The following requirements apply with respect to the corrosion protection system: • Necessary corrosion protection shall be provided, including requirements from

interfacing subsystems. • The design shall ensure reliable electrical continuity to each individual element for the

defined design life, including continuity through the sealine termination (if relevant). • Location and number of cathodic protection inspection points shall be defined and

prepared for intervention. • Earthing connection cables for subsea structure installed systems shall be replaceable

or duplicated.



5.2.4 Design Loads

Subsea structures shall be designed according to the applicable rules and regulations of the land. The methology for structural design given in Annex B has been used as basis for this standard. Production piping systems shall be designed according to ASME B31.3. For simple export systems and water injection systems ASME B31.4 or DnV Rules for Submarine Pipelines, 1981 can be used. All applicable loads that may affect the subsea structure and piping system during all relevant phases such as fabrication, storing, testing, transportation, installation, drilling/completion, operation, and removal shall be included in the design. In general accidental loads are project specific and will be verified by a special risk analysis for the actual application. Accidental loads may include dropped objects, snag loads (fishing gear, anchors), abnormal environmental loads (earthquake), etc. Relevant loads for the actual application are defined in a separate data sheet (UDS-A03).

5.2.5 Operational Requirements

Requirements for simultaneous operations (production, installation, drilling, intervention, workover) and definition of relevant combinations is defined in a separate data sheet (UDS-A09). The layout of the subsea structure and piping system shall allow for simultaneous operations as defined in the subject data sheet.

5.2.6 Test Requirements

The subsea structures and piping systems shall be subject to factory acceptance testing (FAT), integration testing and commissioning. The extent of each test is project and system specific and shall be specified in separate data sheet. The FAT shall ensure and demonstrate that equipment is assembled and function in accordance with purchase order/contract requirements. FAT shall be performed for all fabricated components including components with identical design. The integration test shall: • verify correct installation, assembly and integration towards interfacing subsystems

including all inspection and testing work required to verify that equipment and facilities are complete and fully installed according to approved drawings and specifications, and that all inspections and non-operational test have been performed and recorded



• verify correct function of all components and systems according to approved specifications and requirement including debugging, function testing of equipment and filling of consumables.

Commissioning shall: • verify that the total subsea production system is working satisfactory as an integrated

system • verify all interfaces to platform systems • demonstrate for the operation organization that the subsea production system is ready

for start-up.

5.3 Requirements for Structures

5.3.1 Main Frame and Protection Structure

The following functional requirements apply: • The structure shall ensure sufficient alignment capability for proper physical interfaces

between subsystems such as wellhead/production guide base, x-mas tree/manifold and piping system, manifold/sealine termination and installation aids, protective structure and other relevant interfaces.

• The subsea structures may be designed to accept or not accept drilling loads, ref section 5.2.4. The loads induced on the PGB/bottom frame from the well system will depend upon the following: - Soil conditions and axial stiffness of well system. - Structural design and stiffness of bottom frame against vertical deflection. - Structure/well interface design.

Default values for skirt foundation structures are provided in UDS-A05: • Well supporting structures shall provide guiding/landing/latch capability for the

conductor housing, where required. • The well supporting structure/production guide base design shall allow for thermal

expansion of the conductor/wellhead housings. The thermal expansion data are to be included in the basis for interface tolerance design of template mounted objects.

• A drill cuttings disposal system should be included. Alternatively accumulation of

cuttings shall be considered. • Snagging on the structure during pull-in and pull-out of sealines shall be avoided.



• All retrievable modules and structures shall if not otherwise secured, be properly locked to the bottom frame structure by means of a locking mechanism operated according to the selected intervention strategy.

• The structure shall allow onshore assembly and testing of its supported equipment. • The structure shall transfer all loads from interfacing systems and equipment to the

foundation system. • Where applicable protective structures shall protect the subsea equipment against

damage from dropped objects and fishing gear, by use of e.g. local protection, roof hatches, etc. ref. separate data sheets UDS-A01, UDS-A06 and UDS-A08.

• Where applicable openings in grating on the roof hatches shall be sufficiently small to

protect against objects that are lifted over the structure, i.e. control pods, valve inserts, etc.

• The height from top of the permanently installed equipment to underside roof, shall

be sufficient to prevent any damage on the equipment if the roof is deflected by dropped objects.

• The structure shall provide sufficient space for landing a BOP-stack, and a x-mas tree

in each wellbay. Envelopes will be project specific. • The structure, piping system and controls, and chemical distribution shall provide

proper access for intervention operations, ref. U-CR-007.

5.3.2 Sealine Protection System

When a sealine protection system is required, the following requirements to the system shall apply: • A sealine protection system in the tie-in area shall be designed as a part of the total

protective design of the subsea structure and the sealines. • The sealine protection system shall not imply restriction of any operations during

installation, drilling, completion, production or inspection, maintenance and repair (IMR) of the structure or sealines.

• The sealine protection system shall accommodate thermal and pressure expansion of

sealines, thermal insulation, long term settlement of sealines, and necessary intervention operations to be performed.

5.3.3 Interfaces for Tie-in Porches

The following interface characteristics between tie-in porches and the subsea structure shall be adhered to in design:



• Space requirements, including intervention. • Interface tolerances, including structure and manifolding, such as inboard hub/tie-in

porch. • Loads transferred to structure during tie-in, testing and operation.

5.3.4 Foundation and Levelling System

The levelling and foundation criteria for the actal application is defined in separate data sheet UDS-A04. The following design requirements for the foundation and levelling system apply: • Seabed slope, installation tolerances and effects from possible scouring caused by

currents near the bottom shall be evaluated with respect to the foundation and levelling system.

• Suction loads due to repositioning or levelling shall be catered for • Removal of soil-plug in pile top shall be possible • Intrusion of soil into pile sleeves shall be prevented • A foundation system for well supporting structures, based on support/anchoring on the

well conductor housings can be used. The integrity of the foundation system shall be verified.

• For foundation skirt systems, arrangement shall be made for air escape during splash

zone transfer and water escape during seabed penetration. Lift stability and wash out of soil shall be taken into account.

• Structures with skirt foundation should be designed for self penetration • For skirt systems facilities for suction and pumping shall where required be included

to allow for final penetration, levelling and breaking out prior to removal. The suction and pump system shall be operated according to the selected intervention strategy.

• Settlement of the structures shall be accounted for.

5.3.5 Installation

The installation method and equipment selected for the subsea structure and piping system shall ensure a safe and reliable operation in accordance with the selected intervention strategy. • The installation equipment, temporary and permanent, shall not cause obstructions and

restrict intervention access.



• Disconnection of lifting slings, lifting beams/frames/arrangements used during installation shall be according to the selected intervention strategy. A back-up system shall be provided.

• The installation system shall not represent any hazard to the permanent works during installation, release, reconnection and removal.

• Permanently installed lifting/installation arrangements should be located to minimize

lifting height. • An installation lifting frame (optional) should include a sling laydown area and

attachment for tugger lines, and if required, platforms and support for installation instrumentation, temporary access ladders, and inspection platforms.

• Design and arrangement of structural elements including those not being rigid members of the overall structure (e.g. hatches), shall take special considerations to drag/wave induced forces during launching/retrieval through the splash zone.

• Use of wire or soft rope lashing should be avoided.

5.4 Requirements for Manifold and Piping System

5.4.1 General

The manifold and piping system may be permanently integrated with the subsea structure or installed as one or several separate modules. The following functional requirements shall apply: • All critical interfaces and equipment such as valves, flanges, piping bends and

connectors, shall allow necessary intervention work. • Production piping insulation requirements are project specific and defined in data

sheet. • Connection/disconnection of sealines shall not affect other manifold connections. • Installation and retrieval of x-mas trees on well supporting structures shall be

completed without affecting manifold connections and other x-mas trees. • Inspection areas and monitoring points for such as CP-measurements, wall thickness

measurements, sand detection and pig signalling, shall be provided and prepared for intervention.

• Manifold piping joints shall be butt welded. • All non welded connections in hydrocarbon bearing lines shall have metal to metal

seals.



• Provision for installation of back-up electrical cables according to the selected

intervention strategy shall be included • Spare lines or provision for installation of back-up lines shall be provided for the

hydraulic power and chemical injection systems.

5.4.2 Valves

The manifold valves shall have the following basic criteria: • Valve design shall be according to ISO 10423 (API 6A), API 6D and API 14D.

• The material and pressure classes of the valves shall conform to the system

requirements (in terms of corrosion/erosion resistance and pressure class). The manifold valves shall at least be rated to the highest system pressure (e.g. max. Injection system pressure or well kill pressure).

• Manifold valves shall be classified to API and ANSI classes.

• The design of the valves shall minimise the potential for hydrate formation and damage that could be caused by possible sand, erosion or corrosion. For gate valves with vertical movement of gate, special consideration shall be given to possibility for sand accumulation or hydrate formation in valve cavity.

• Special attention shall be paid to bonnet and stem sealing. Bonnet seals shall be metal to metal or welded. Stem seals shall be compatible with service requirements.

• Internal sealing. Seals between the gate/ball/plug/needle and the “seats” shall be metal to metal. The seal between floating seats and body shall be compatible with service requirements.

• The valves shall be designed for failure free operation during field life. Manifold/distribution system failures are normally of common type (several wells are shut in by failure of one component). As a general principle the system availability should be increased through simple designs and selection of high quality components. Use of insert valves or valve modules increase the number of possible leak paths and thereby reduce the MTBF. If such solutions are selected, it shall be demonstrated that the overall availability is increased compared to a simpler solution with high quality valves integral with the manifold. For frequently operated valves with remote actuation, the retrievability of valve or valve parts should be assessed (e.g. retrievability of actuator alone, actuator with valve insert, valve module or the complete manifold). The method of retrievability shall be dependant on: − cost effective and simple retrieval/re-running



− minimal well/production downtime − robust/reliable valve to piping sealing mechanism − type and size of valve

For remotely operated valves that are not frequently actuated (e.g. round trip pigging valves), the ROV override can be considered as a permanent fall back for a failed primary actuator. No possibility to retrieve such valves may be accepted if a high quality valve is selected.

• Manifold valving shall be operable in accordance with the selected intervention

strategy. The valves can be remotely actuated. ROV or diver operated valves shall have position indicators. The design of the ROV interface should be according to data sheet.

• The operation of the valve shall be dictated by the overall philosophy of the field/project. The method shall, however, take into account the intervention strategy.

Testing Prototype qualification testing shall be proven for each valve size and rating. Optionally sand slurry (not gel) performance shall be proven. FAT-testing of the valves and actuators shall be conducted following ISO 10423 (API 6A) PSL level 3 with gas test. The testing shall register torque levels at maximum differential pressure.

5.4.3 Process Piping, Production Control and Chemical Distribution System Design

The pipe routing shall: • minimize level variations where liquids can be trapped (causing e.g. hydrate plugging,

corrosion) • minimize risk for damaging the piping during testing, installation and intervention. • ensure required flexibility. • minimize number of pipe bends and pipe supports. The following requirements shall apply for pigable piping systems: • Bends in piggable lines should have a radius of minimum 5 times the pipe ID. • Successive bends, valves, branches and combination of such, should be separated with

a straight leg of minimum 3 times the pipe ID



• Branches to piggable lines shall be designed to avoid collection of deposits from the pigging. The branches shall be taken above the centreline of the headers. Fabricated tees and fittings to piggable lines shall be designed for pigging.

• Piggable lines should have constant internal diameter, ref. DnV Rules for Submarine

Pipelines, 1981 and shall accommodate for roundtrip pigging if required.

5.5 Requirements for Replacement Devices

Where considered necessary replacement devices are used for replacement and installation of structural elements and modules. • Replacement devices shall be designed in compliance with the selected intervention

strategy • The devices shall be passive, simple, small and light for easy operation, deck handling

and storage. • The devices shall have padeyes for seafastening and footings for transportation and

storage as required.

• The replacement devices shall comply with the operational requirements, seastates, intervention vessels, etc.



ANNEX A SUBSEA DATA SHEET

(Normative)



General Field Data – udsa0301.xls

Drilling loads Page 1 – udsa0501.xls

Drilling loads Page 2 – udsa051a.xls

Dropped object Loads – udsa0601.xls

Design against fishing gear/overtrawlability Page 1 – udsa0701.xls

Design against fishing gear/overtrawlability Page 2 – udsa071a.xls

Design of Hatches – udsa0801.xls















ANNEX B

NATIONAL REGULATIONS (Informative)



ANNEX B National Regulations (Informative) The latest edition and current amendments of the following standard shall apply:

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