EN 1918-3:2016

• Abstract:

  This European Standard covers the functional recommendations for design, construction, testing, commissioning, operation, maintenance and abandonment of underground gas storage (UGS) facilities in solution-mined salt caverns up to and including the wellhead.; It specifies practices which are safe and environmentally acceptable.; For necessary surface facilities for underground gas storage, EN 1918-5 applies.; In this context "gas" is any hydrocarbon fuel:; — which is in a gaseous state at a temperature of 15 °C and under a pressure of 0,1 MPa (this includes natural gas, compressed natural gas (CNG) and liquefied petroleum gas (LPG). The stored product is also named fluid);; — which meets specific quality requirements in order to maintain underground storage integrity, performance, environmental compatibility and fulfils contractual requirements.; This European Standard specifies common basic principles for underground gas storage facilities. Users of this European Standard should be aware that more detailed standards and/or codes of practice exist. A non-exhaustive list of relevant standards can be found in Annex A.; This European Standard is intended to be applied in association with these national standards and/or codes of practice and does not replace them.; In the event of conflicts in terms of more restrictive requirements in the national legislation/regulation with the requirements of this European Standard, the national legislation/regulation takes precedence as illustrated in CEN/TR 13737 (all parts).; NOTE CEN/TR 13737 (all parts) contains:; — clarification of relevant legislation/regulations applicable in a country;; — if appropriate, more restrictive national requirements;; — national contact point for the latest information.; This European Standard is not intended to be applied retrospectively to existing facilities.

• Status: Published
• Publication Date: 22-Mar-2016
• Withdrawal Date: 29-Sep-2016
• ICS: 75.200 - Petroleum products and natural gas handling equipment
• Technical Committee: CEN/TC 234 - Gas infrastructure
• Drafting Committee: CEN/TC 234/WG 4 - Gas underground storage
• Current Stage: 9092 - Decision on results of review/2YR ENQ - revise - Review Enquiry
• Start Date: 20-Dec-2022
• Completion Date: 17-Sep-2026
• Mandate: M/017 - Standardization mandate to CEN in the field of equipment and installation for the transmission and distribution of gas
• Ref Project: SIST EN 1918-3:2016 - Gas infrastructure - Underground gas storage - Part 3: Functional recommendations for storage in solution-mined salt caverns

• Replaces: EN 1918-3:1998 - Gas supply systems - Underground gas storage - Part 3: Functional recommendations for storage in solution-mined salt cavities
• Effective Date: 11-Jun-2011
• Refers: EN 1918-5:2016 - Gas infrastructure - Underground gas storage - Part 5: Functional recommendations for surface facilities
• Effective Date: 28-Jan-2026
• Revised: FprEN 1918-3 - Gas infrastructure - Underground gas storage - Part 3: Functional recommendations for storage in solution-mined salt caverns
• Effective Date: 28-Dec-2022

Overview - EN 1918-3:2016 (CEN)

EN 1918-3:2016 is the CEN European standard that provides functional recommendations for underground gas storage (UGS) in solution-mined salt caverns, covering the facility up to and including the wellhead. It addresses safe and environmentally acceptable practices for the design, construction, testing, commissioning, operation, maintenance and abandonment of such storages. The standard applies to gases that are gaseous at 15 °C and 0.1 MPa (including natural gas, CNG and LPG) and specifies principles that complement national legislation and more detailed codes of practice. EN 1918-5 covers associated surface facilities.

Key topics and technical requirements

• Scope & definitions: common UGS terminology (e.g., cushion gas, maximum/minimum operating pressure (MOP), containment, monitoring wells).
• Design principles: geological modelling, cavern sizing and stability, well design (casing, cementing, completions), pressure limits and integrity requirements.
• Geological exploration: investigation and data requirements to establish cavern siting, caprock integrity and overburden characterization.
• Solution mining: recommended practices for creating salt caverns by dissolution and implications for cavern geometry and stability.
• Wells and wellheads: construction, completion, monitoring and maintenance of injection/withdrawal and auxiliary wells up to the wellhead.
• Monitoring & instrumentation: subsurface and surface monitoring systems for pressure, temperature, fluid quality and leakage detection.
• Testing and commissioning: performance testing and verification before operation.
• Operation & maintenance: operational envelopes (injection/withdrawal profiles), cavern integrity management, HSE and environmental protection measures.
• Abandonment: decommissioning steps including gas withdrawal, well plugging and post‑abandonment monitoring.
• Compliance & interaction with national rules: the standard is to be used in association with national standards and CEN/TR 13737 guidance where national legislation prevails.

Practical applications

EN 1918-3:2016 is used to:

• Guide design and engineering of new salt-cavern UGS projects.
• Define technical and HSE operating envelopes for operators and asset owners.
• Inform procurement and inspection specifications for wells, solution mining and monitoring systems.
• Support permitting and regulatory documentation by demonstrating adherence to European functional recommendations.
• Serve as a reference for consultants, geotechnical and reservoir engineers, safety/HSE specialists and regulatory bodies.

Who should use this standard

• UGS designers and project engineers
• Cavern solution-mining contractors
• Gas storage operators and asset owners
• Well construction and completion contractors
• HSE and environmental compliance teams
• Regulators and permitting authorities
• Technical consultants and auditors

Related standards and notes

• Part of the EN 1918 series (Parts 1–5); see EN 1918-5 for surface facilities.
• Annex A lists additional relevant standards; national regulations take precedence in case of conflict (see CEN/TR 13737).
• Not intended to be applied retrospectively to existing facilities.

2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.NFLRQDOQDGasinfrastruktur - Untertagespeicherung von Gas - Teil 3: Funktionale Empfehlungen für die Speicherung in gesolten SalzkavernenInfrastructure gazières - Stockage souterrain de gaz - Partie 3: Recommandations fonctionnelles pour le stockage en cavités salines creusées par dissolutionGas infrastructure - Underground gas storage - Part 3: Functional recommendations for storage in solution-mined salt caverns75.200Petroleum products and natural gas handling equipmentICS:Ta slovenski standard je istoveten z:EN 1918-3:2016SIST EN 1918-3:2016en,fr,de01-november-2016SIST EN 1918-3:2016SLOVENSKI
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EUROPEAN STANDARD NORME EUROPÉENNE EUROPÄISCHE NORM
EN 1918-3
March
t r s x ICS
y wä t r r Supersedes EN
s { s zæ uã s { { zEnglish Version
Gas infrastructure æ Underground gas storage æ Part
uã Functional recommendations for storage in solutionæmined salt caverns Infrastructures gazières æ Stockage souterrain de gaz æ Partie
uã Recommandations fonctionnelles pour le stockage en cavités salines creusées par dissolution
Gasinfrastruktur æ Untertagespeicherung von Gas æ Teil
uã Funktionale Empfehlungen für die Speicherung in gesolten Salzkavernen This European Standard was approved by CEN on
s r January
t r s xä
egulations which stipulate the conditions for giving this European Standard the status of a national standard without any alterationä Upætoædate lists and bibliographical references concerning such national standards may be obtained on application to the CENæCENELEC Management Centre or to any CEN memberä
translation under the responsibility of a CEN member into its own language and notified to the CENæCENELEC Management Centre has the same status as the official versionsä
CEN members are the national standards bodies of Austriaá Belgiumá Bulgariaá Croatiaá Cyprusá Czech Republicá Denmarká Estoniaá Finlandá Former Yugoslav Republic of Macedoniaá Franceá Germanyá Greeceá Hungaryá Icelandá Irelandá Italyá Latviaá Lithuaniaá Luxembourgá Maltaá Netherlandsá Norwayá Polandá Portugalá Romaniaá Slovakiaá Sloveniaá Spainá Swedená Switzerlandá Turkey andUnited Kingdomä
EUROPEAN COMMITTEE FOR STANDARDIZATION COMITÉ EUROPÉEN DE NORMALISATION EUROPÄISCHES KOMITEE FÜR NORMUNG
CEN-CENELEC Management Centre:
Avenue Marnix 17,
B-1000 Brussels
t r s x CEN All rights of exploitation in any form and by any means reserved worldwide for CEN national Membersä Refä Noä EN
s { s zæ uã t r s x ESIST EN 1918-3:2016

Non-exhaustive list of relevant standards . 36 Annex B (informative)
Significant technical changes between this European Standard and the previous version EN 1918-3:2008 . 38
MOP maximum pressure of the storage reservoir or cavern, normally at maximum inventory of gas in storage, which has not to be exceeded in order to ensure the integrity of the UGS and is based on the outcome of geological/technical engineering and is approved by authorities Note 1 to entry: The maximum operating pressure is related to a datum depth and in caverns usually to the casing shoe of the last cemented casing. 3.1.26 minimum operating pressure minimum pressure of the storage reservoir or cavern, normally reached at the end of the decline phase of the withdrawal profile and for caverns is based on geomechanical investigations to ensure stability and to limit the effect of subsidence and normally has to be approved by authorities and has not to be underrun Note 1 to entry: The minimum pressure is related to a datum depth. 3.1.27 monitoring well observation well well for purposes of monitoring the storage horizon and/or overlying or underlying horizons for subsurface phenomena such as pressure fluctuation, fluid flow and qualities, temperature, etc. 3.1.28 operating well well used for gas withdrawal and/or injection 3.1.29 overburden all sediments or rock that overlie a geological formation SIST EN 1918-3:2016

It contains fluids which are internally in pressure communication. 3.1.33 saturation percentages of pore space occupied by fluids 3.1.34 seismic technology technology to characterize the subsurface image with respect to extent, geometry, fault pattern and fluid content applying acoustic waves, impressed by sources near to surface in the subsurface strata, which pass through strata with different seismic responses and filtering effects back to surface, where they are recorded and analysed 3.1.35 string entity of casing or tubing plus additional equipment, screwed or welded together as parts of a well respectively completion 3.1.36 subsurface safety valve valve installed in casing and/or tubing beneath the wellhead or the lower end of the tubing for the purpose of stopping the flow of gas in case of emergency 3.1.37 tubing pipe or set of pipes that are screwed or welded together to form a string, through which fluids are injected or withdrawn or which can be used for monitoring 3.1.38 well borehole and its technical equipment including the wellhead 3.1.39 well integrity well condition without uncontrolled release of fluids throughout the life cycle SIST EN 1918-3:2016

Key 1 operating wells 2 monitoring wells 3 indicator horizon 4 caprock 5 storage reservoir and stored gas 6 salt dome 7 cavern Figure 1 — Storage in aquifers, oil and gas fields, solution mined salt caverns For LPG storage only salt or rock caverns can be applied. The UGS type applied is dependent on the geological conditions and prerequisites as well as on the designed capacity layout. 4.2.3 General characterization of UGS UGS are naturally or artificially developed reservoirs respectively artificially developed caverns in subsurface geological formations used for the storage of natural gas (or LPG). An UGS consists of all subsurface and surface facilities required for the storage and for the withdrawal and injection of natural gas (or storage of LPG). Several subsurface storage reservoirs or caverns may be connected to one or several common surface facilities. The suitability of subsurface geological formations shall be investigated individually for each location, in order to operate the storage facilities in an efficient, safe and environmentally compatible manner. In order to construct a storage facility, wells are used to establish a controlled connection between the reservoir or cavern and the surface facilities at the wellhead. The wells used for cycling the storage gas are called operating wells. In addition to the operating wells, specially assigned observation wells may be used to monitor the storage performance with respect to pressures and saturations and the quality of reservoir water as well as to monitor any interference in adjacent formations. For the handling of gas withdrawal and gas injection the surface facilities are the link between the subsurface facilities and the transport system, comprising facilities for gas dehydration/treatment, compression, process control, measurement. Gas is injected via the operating wells into the pores of a reservoir or into a cavern, thus building up a reservoir of compressed natural gas (or LPG). SIST EN 1918-3:2016

Key 1 operating wells 2 salt dome 3 cavern Figure 2 — Cavern storage 4.3 Long-term containment of stored fluids The storage facility shall be designed, constructed and operated to ensure the continuing long-term containment of the stored fluids. This presupposes: — adequate prior knowledge of the geological formation in which the storage is to be developed and of its geological environment; SIST EN 1918-3:2016

Key 1 wellhead 9 cavern height 2 cemented casing 10 distance to underlying strata 3 tubing 11 cavern diameter 4 cavern neck 12 pillar 5 cavern roof 13 overburden 6 cavern 14 salt dome or salt strata 7 sump/remaining brine 15 underlying strata 8 distance to overburden 16 subsurface safety valve Figure 3 — Cavern layout 5.4 Wells 5.4.1 General The design of a well is focused on: — the drilling platform, well site and wellhead area; — the equipment of the well, especially the casing and the completion (see Figure 4); and this design shall take into account: SIST EN 1918-3:2016
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