prEN 1918-5
(Main)Gas infrastructure - Underground gas storage - Part 5: Functional recommendations for surface facilities
Gas infrastructure - Underground gas storage - Part 5: Functional recommendations for surface facilities
This document covers the functional recommendations for the design, construction, testing, commissioning, operation, maintenance and abandonment of the surface facilities for underground gas storage (UGS), between the wellhead and the connection to the gas grid.
It specifies practices which are safe and environmentally acceptable.
For necessary subsurface facilities for underground storage, the relevant part of EN 1918 1 to EN 1918 4 applies. In this context, “gas” refers to flammable gas:
— which is in a gaseous state at a temperature of 15 °C and under a pressure of 0,1 MPa. 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 comprises:
— gas not in liquid phase under subsurface conditions:
— methane-rich gases;
— natural gas;
— biomethane;
— synthetic methane;
— hydrogen of various purities;
— any mixtures of the gases above;
— hydrocarbon gas in liquid phase under subsurface conditions such as:
— ethylene;
— liquified petroleum gas (LPG).
NOTE 1 Correspondingly the EN 1918 series can be considered where applicable for underground storage of any other fluid e.g. helium, carbon dioxide, compressed air, rDME (renewable dimethyl ether) and hydrogen transport fluids (such as ammonia and LOHC).
This document is not intended to be applied retrospectively to existing facilities.
NOTE 2 Correspondingly this document can be considered for major conversions in case of significant change of gas composition.
Gasinfrastruktur - Untertagespeicherung von Gas - Teil 5: Funktionale Empfehlungen für Übertageanlagen
Dieses Dokument legt die funktionalen Empfehlungen für Planung, Errichtung, Prüfung, Inbetriebnahme, Betrieb, Instandhaltung und Stilllegung von Übertageanlagen für Untertagegasspeicher vom Bohrlochkopf bis zum Anschluss an das Gastransportsystem fest.
Es legt sichere und umweltverträgliche Verfahrensweisen fest.
Für erforderliche Untertageanlagen für die Untertagespeicherung gelten die einschlägigen Teile 1, 2, 3 oder 4 von EN 1918. In diesem Zusammenhang bezieht sich „Gas“ auf brennbares Gas, das
sich bei einer Temperatur von 15 °C und unter einem Druck von 0,1 MPa in gasförmigem Zustand befindet. Das gespeicherte Produkt wird auch als Medium bezeichnet;
bestimmte Qualitätsanforderungen erfüllt, um die Integrität des Untertagespeichers, die Leistung und die Umweltverträglichkeit aufrechtzuerhalten, und vertragliche Anforderungen erfüllt.
Dies umfasst:
Gas, das sich bei Untertagebedingungen nicht in flüssiger Phase befindet:
methanreiche Gase;
Erdgas;
Biomethan;
synthetisches Methan;
Wasserstoff in verschiedenen Reinheitsgraden;
jegliche Gemische der oben genannten Gase;
Kohlenwasserstoffgas, das sich bei Untertagebedingungen in flüssiger Phase befindet, z. B.:
Ethylen;
Flüssiggas (LPG, liquefied petroleum gas).
ANMERKUNG 1 Entsprechend kann die Normenreihe EN 1918, soweit anwendbar, für die Untertagespeicherung von jedem anderen flüssigen oder gasförmigen Medium berücksichtigt werden, z. B. Helium, Kohlenstoffdioxid, Druckluft, erneuerbarer Dimethylether (en: renewable dimethyl ether, rDME) und Wasserstoff-Trägerfluide (wie Ammoniak und LOHC).
Es ist nicht vorgesehen, dieses Dokument rückwirkend auf bestehende Anlagen anzuwenden.
ANMERKUNG 2 Entsprechend kann dieses Dokument für umfassende Umstellungen bei wesentlichen Änderungen der Gaszusammensetzung berücksichtigt werden.
Infrastructures gazières - Stockage souterrain de gaz - Partie 5 : Recommandations fonctionnelles pour les installations de surface
Le présent document décrit les recommandations fonctionnelles pour la conception, la construction, les essais, la mise en service, l’exploitation, la maintenance et l’abandon des installations de surface d’un stockage souterrain de gaz comprises entre les têtes de puits et le réseau de gaz.
Il spécifie les pratiques acceptables pour la sécurité et l’environnement.
Pour les installations de subsurface qui sont nécessaires pour un stockage souterrain de gaz, la partie pertinente des EN 1918 1 à EN 1918 4 s’applique. Dans ce contexte, le terme « gaz » désigne un gaz inflammable :
— qui est à l’état gazeux à une température de 15 °C et sous une pression de 0,1 MPa. Le produit stocké est également appelé « fluide » ;
— qui satisfait à des prescriptions spécifiques en matière de qualité afin de maintenir l’intégrité, les performances, la compatibilité environnementale du stockage souterrain et qui respecte les prescriptions contractuelles.
Sont inclus :
— les gaz qui ne sont pas en phase liquide dans des conditions de subsurface :
— les gaz riches en méthane :
— le gaz naturel ;
— le biométhane ;
— le méthane de synthèse ;
— l’hydrogène de différentes puretés ;
— tout mélange des gaz précités ;
— les gaz d’hydrocarbure en phase liquide dans des conditions de subsurface, tels que :
— l’éthylène ;
— les gaz de pétrole liquéfiés (GPL).
NOTE 1 Par conséquent, une utilisation de la série EN 1918 peut être envisagée, lorsque cela est applicable, pour le stockage souterrain de tout autre fluide tel que l’hélium, le dioxyde de carbone, l’air comprimé, le diméthyl éther renouvelable (rDME) et les fluides de transport de l’hydrogène (ammoniac et LOHC, par exemple).
Le présent document n’est pas destiné à être appliqué de façon rétroactive aux installations existantes.
NOTE 2 Par conséquent, le présent document peut être utilisé pour des conversions majeures en cas de changement significatif de la composition du gaz.
Infrastruktura za plin - Podzemna plinska skladišča - 5. del: Funkcionalna priporočila za nadzemno opremo
General Information
Relations
Standards Content (Sample)
SLOVENSKI STANDARD
01-junij-2025
Infrastruktura za plin - Podzemna plinska skladišča - 5. del: Funkcionalna
priporočila za nadzemno opremo
Gas infrastructure - Underground gas storage - Part 5: Functional recommendations for
surface facilities
Gasinfrastruktur - Untertagespeicherung von Gas - Teil 5: Funktionale Empfehlungen für
Übertageanlagen
Infrastructures gazières - Stockage de gaz souterrain - Partie 5 : Recommandations
fonctionnelles pour les installations de surface
Ta slovenski standard je istoveten z: prEN 1918-5
ICS:
75.200 Oprema za skladiščenje Petroleum products and
nafte, naftnih proizvodov in natural gas handling
zemeljskega plina equipment
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
DRAFT
EUROPEAN STANDARD
NORME EUROPÉENNE
EUROPÄISCHE NORM
May 2025
ICS 75.200 Will supersede EN 1918-5:2016
English Version
Gas infrastructure - Underground gas storage - Part 5:
Functional recommendations for surface facilities
Infrastructures gazières - Stockage de gaz souterrain - Gasinfrastruktur - Untertagespeicherung von Gas - Teil
Partie 5 : Recommandations fonctionnelles pour les 5: Funktionale Empfehlungen für Übertageanlagen
installations de surface
This draft European Standard is submitted to CEN members for enquiry. It has been drawn up by the Technical Committee
CEN/TC 234.
If this draft becomes a European Standard, CEN members are bound to comply with the CEN/CENELEC Internal Regulations
which stipulate the conditions for giving this European Standard the status of a national standard without any alteration.
This draft European Standard was established by CEN in three official versions (English, French, German). A version in any other
language made by translation under the responsibility of a CEN member into its own language and notified to the CEN-CENELEC
Management Centre has the same status as the official versions.
CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia,
Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway,
Poland, Portugal, Republic of North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Türkiye and
United Kingdom.
Recipients of this draft are invited to submit, with their comments, notification of any relevant patent rights of which they are
aware and to provide supporting documentation.
Warning : This document is not a European Standard. It is distributed for review and comments. It is subject to change without
notice and shall not be referred to as a European Standard.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION
EUROPÄISCHES KOMITEE FÜR NORMUNG
CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels
© 2025 CEN All rights of exploitation in any form and by any means reserved Ref. No. prEN 1918-5:2025 E
worldwide for CEN national Members.
Contents Page
European foreword . 4
Introduction . 5
1 Scope . 6
2 Normative references . 6
3 Terms and definitions . 7
3.1 Terms and definitions common to EN 1918 (all parts) . 7
3.2 Terms and definitions specific to this document . 9
4 Requirements for underground gas storage . 10
4.1 General. 10
4.2 Underground gas storage . 10
4.2.1 Overview and functionality . 10
4.2.2 Types . 11
4.2.3 General characterization . 12
4.3 Injection facilities . 13
4.3.1 Liquid and solid separation . 13
4.3.2 Gas compression . 13
4.3.3 Gas cooling . 14
4.4 Withdrawal facilities . 14
4.4.1 Prevention of hydrate formation . 14
4.4.2 Solid and liquid separation . 14
4.4.3 Gas heating . 14
4.4.4 Pressure reduction . 14
4.4.5 Gas conditioning . 14
4.4.6 Re-Compression . 14
4.4.7 Odorization . 14
4.5 Surface utilities . 15
4.5.1 Treatment of recovered water . 15
4.5.2 Fuel gas system . 15
4.5.3 Instrument system . 15
4.5.4 Corrosion protection . 15
4.5.5 Power supplies. 15
4.5.6 Earthing . 15
4.5.7 Gas analysis and metering . 15
4.5.8 Others . 15
4.6 Leaching and debrining facilities for salt caverns . 15
4.7 Liquified petroleum gas . 16
4.7.1 Solid and liquid separation . 16
4.7.2 Liquid transfer . 16
4.7.3 Heating . 16
4.7.4 Cooling . 16
4.7.5 Conditioning . 16
4.7.6 Colourization . 17
4.8 Environmental conservation . 17
4.8.1 General. 17
4.8.2 Methane emissions . 17
4.8.3 Other gas emissions . 18
5 Design . 18
5.1 General . 18
5.2 Safety and environmental issues . 19
5.3 Engineering . 20
5.4 Security . 20
5.5 Pumps and compressors . 20
5.6 Process control and monitoring . 20
5.7 Security . 20
5.8 Back-up systems. 20
5.9 Manning levels . 20
5.10 Maintenance and inspection . 21
5.11 Flaring and venting . 21
5.12 Prevention and control of fires and explosions . 21
6 Construction . 21
7 Testing and commissioning . 21
8 Operation and maintenance . 22
8.1 Operating principles . 22
8.2 Health, safety and environment . 22
8.2.1 Safety management and health and environment . 22
8.2.2 Emergency procedures . 23
8.3 Adaptation to climate change . 23
8.3.1 Climate change effects . 23
8.3.2 Climate change impacts . 23
9 Abandonment. 25
9.1 General . 25
9.2 Surface facilities . 25
Annex A (informative) Significant technical changes between this document and EN 1918-5:2016
............................................................................................................................................................................. 26
Bibliography . 27
European foreword
This document (prEN 1918-5:2025) has been prepared by Technical Committee CEN/TC 234 “Gas
infrastructure”, the secretariat of which is held by DIN.
This document is currently submitted to the CEN Enquiry.
This document will supersede EN 1918-5:2016.
For a list of significant technical changes with respect to EN 1918-5:2016 see Annex A.
This document has been prepared under a standardization request addressed to CEN by the European
Commission. The Standing Committee of the EFTA States subsequently approves these requests for its
Member States.
This document is Part 5 of a European Standard on “Gas infrastructure - Underground gas storage” which
includes the following five parts:
— Part 1: Functional recommendations for storage in aquifers;
— Part 2: Functional recommendations for storage in oil and gas fields;
— Part 3: Functional recommendations for storage in solution-mined salt cavities;
— Part 4: Functional recommendations for storage in rock caverns;
— Part 5: Functional recommendations for surface facilities.
Introduction
This document specifies common basic principles for underground gas storage facilities. Users of this
document are expected to be aware that more detailed standards and/or codes of practice exist. This
document is intended to be applied in association with these national standards and/or codes of practice
and does not replace them. Furthermore, a non-exhaustive list of related European and international
standards can be found in the Bibliography.
NOTE Directive 2009/73/EC concerning common rules for the internal market in natural gas and the related
Regulation (EC) No 715/2009 on conditions for access to the natural gas transmission networks also aim at
technical safety including technical reliability of the European gas system. These aspects are also in the scope of
CEN/TC 234 standardization. In this respect, CEN/TC 234 evaluated the indicated EU legislation and amended this
technical standard accordingly, where required and appropriate.
1 Scope
This document covers the functional recommendations for the design, construction, testing,
commissioning, operation, maintenance and abandonment of the surface facilities for underground gas
storage (UGS), between the wellhead and the connection to the gas grid.
It specifies practices which are safe and environmentally acceptable.
For necessary subsurface facilities for underground storage, the relevant part of EN 1918-1 to EN 1918-4
applies. In this context, “gas” refers to flammable gas:
— which is in a gaseous state at a temperature of 15 °C and under a pressure of 0,1 MPa. 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 comprises:
— gas not in liquid phase under subsurface conditions:
— methane-rich gases;
— natural gas;
— biomethane;
— synthetic methane;
— hydrogen of various purities;
— any mixtures of the gases above;
— hydrocarbon gas in liquid phase under subsurface conditions such as:
— ethylene;
— liquified petroleum gas (LPG).
NOTE 1 Correspondingly the EN 1918 series can be considered where applicable for underground storage of any
other fluid e.g. helium, carbon dioxide, compressed air, rDME (renewable dimethyl ether) and hydrogen transport
fluids (such as ammonia and LOHC).
This document is not intended to be applied retrospectively to existing facilities.
NOTE 2 Correspondingly this document can be considered for major conversions in case of significant change of
gas composition.
2 Normative references
The following documents in whole or in part, are normatively referenced in this document and are
indispensable for its application. For dated references, only the edition cited applies. For undated
references, the latest edition of the referenced document (including any amendments) applies.
ISO 1663, Rigid cellular plastics - Determination of water vapour transmission properties
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply. The definitions common to
EN 1918 (all parts) are listed in 3.1; those specific for this document are listed in 3.2.
ISO and IEC maintain terminology databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https://www.iso.org/obp/
— IEC Electropedia: available at https://www.electropedia.org/
3.1 Terms and definitions common to EN 1918 (all parts)
3.1.1
aquifer
reservoir, group of reservoirs, or a part thereof that is fully water-bearing and displaying differing
permeability/porosity
3.1.2
exploration
all technical activities connected with the investigation of potential storage locations for the assessment
of storage feasibility and derivation of design parameters
3.1.3
formation (horizon)
body of rock mass characterized by a degree of homogeneous lithology which forms an identifiable
geologic unit
3.1.4
gas injection
gas delivery from gas transport system into the reservoir/cavern through surface facilities and wells
3.1.5
gas withdrawal
gas delivery from the reservoir or cavern through wells and surface facilities to a gas transport system
3.1.6
hydrogen
H
lightest and most represented chemical element, found in nature as a diatomic molecule (H , or
dihydrogen), gaseous under standard conditions, colourless, odourless and highly flammable
3.1.7
indicator horizon
horizon overlying the caprock in the storage area and used for monitoring
3.1.8
maximum operating pressure
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.
3.1.9
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 is for caverns based on geomechanical investigations to ensure stability
and to limit the effect of subsidence
Note 1 to entry: The minimum pressure is related to a datum depth and in caverns usually to the casing shoe of the
last cemented casing.
3.1.10
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
3.1.11
operating well
well used for gas withdrawal and/or injection
3.1.12
reservoir
porous and permeable (in some cases naturally fractured) formation having area- and depth-related
boundaries based on physical and geological factors
Note 1 to entry: It contains fluids which are internally in pressure communication.
3.1.13
saturation
percentages of pore space occupied by fluids
3.1.14
well
borehole and its technical equipment including the wellhead
3.1.15
well integrity
well condition without uncontrolled release of fluids throughout the life cycle
3.1.16
well integrity management
complete system necessary to ensure well integrity at all times throughout the life cycle of the well, which
comprises dedicated personnel, assets, including subsurface and surface installations, and processes
provided by the operator to monitor and assess well integrity
3.1.17
wellhead
equipment supported by the top of the casing including tubing hanger, shut off and flow valves, flanges
and auxiliary equipment which provides the control and closing-off of the well at the upper end of the
well at the surface
3.1.18
working gas volume
volume of gas in the storage above the designed level of cushion gas volume, which can be
withdrawn/injected with installed subsurface and surface facilities (wells, flow lines, etc.) subject to legal
and technical limitations (pressures, gas velocities, flowrates, etc.)
Note 1 to entry: Depending on local site conditions (injection/withdrawal rates, utilization hours, etc.) the working
gas volume can be cycled more than once a year.
3.2 Terms and definitions specific to this document
3.2.1
flaring
deliberate burning of natural gas in flares, without recovery of its energy, generally as part of the
maintenance or safety of surface installations
3.2.2
gas hydrates
chemical compounds consisting of water molecules trapping gas molecules, formed under conditions of
high pressure and low temperature
3.2.3
gas odorization
addition of an odorous substance to natural gas to facilitate its detection
3.2.4
gas processing and conditioning
range of industrial processes designed to bring natural gas up to transport or final consumption
standards by removing contaminants such as solids, water, carbon dioxide, hydrogen sulphide, mercury,
hydrates and condensates
3.2.5
HAZOP
method commonly used for analysing industrial risks
Note 1 to entry: HAZOP stands for hazard and operability analysis.
3.2.6
power-to-gas
process aiming at the conversion of electricity, generally produced from renewable or low-carbon
sources, into gas
3.2.7
separator
equipment used to separate fluid components of a hydrocarbon well production into gas and liquid
phases
3.2.8
venting
deliberate release of natural gas into the atmosphere, without recovery of its energy, generally as part of
the safety of surface installations
4 Requirements for underground gas storage
4.1 General
The main equipment that can be required for both the withdrawal and the injection operations of gas
storage facility is described below.
Where no specific mention of LPG or natural gas is made, the following statements refer to both.
4.2 Underground gas storage
4.2.1 Overview and functionality
EN 1918 series covers storage of gas as defined in the Scope. Because of the relevance of underground
gas storage of methane rich gases and hydrogen, the major part of this introduction is related to these.
The underground gas storage (UGS) is an efficient proven common technology and is in use since 1915.
UGS became an essential indispensable link in the gas supply chain for adjusting supply to meet short-
term and seasonal changes in demand.
Gas produced from natural resources or synthesized by various production methods is increasingly being
used to supply energy requirements. As the gas supply from various sources does not match with the
variable market demand, gas is injected into underground gas storage reservoirs when market demand
falls below the level of gas delivery or if there is an economic incentive. Gas is withdrawn from storage
facilities to supplement the supply if demand exceeds that supply or withdrawal is economically
attractive.
The primary function of UGS is to ensure that supply is adjusted for peak and seasonal demand. Apart
from this, the storage facilities can provide stand-by reserves in case of interruption of the planned supply
or for regulatory and/or technical requirements. Typically, UGS is applied for commercial storage
services.
Thus, in summary underground gas storage facilities can be used for:
— security of supply;
— providing flexibilities;
— balancing of seasonal demand variabilities;
— structuring of gas supply;
— provision of balancing energy for the optimization of transport grids;
— trading and arbitrage purpose;
— stand-by provisions and strategic reserves;
— structuring renewable energy sources – power to gas;
— storage of associated gas as service for production optimization and resultant environmental
conservation;
— blending different types of gas quality.
4.2.2 Types
For storage of gas, several types of underground gas storage facilities can be used which differ by storage
formation and storage mechanism (see the following and Figure 1):
— pore storage;
— storage in aquifers;
— storage in former gas fields;
— storage in former oil fields;
— caverns;
— storage in salt caverns;
— storage in rock caverns (including lined rock caverns);
— storage in abandoned mines.
Key
1 operating wells
2 monitoring wells
3 indicator horizon
4 caprock
5 storage reservoir and stored gas
6 salt dome (valid also for salt layer)
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 used.
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
UGS are naturally or artificially developed reservoirs respectively artificially developed caverns in
subsurface geological formations used for the storage of gas (or in the case of LPG in a liquid phase under
subsurface conditions). A UGS consists of all subsurface and surface facilities required for the storage and
for the withdrawal and injection of gas. Several subsurface storage reservoirs or caverns may be
connected to one or several common surface facilities.
The suitability of subsurface geological formations has to 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 well head. 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, typically comprising facilities for gas
dehydration/treatment, hydrogen/natural gas separation, blending, compression, heating and cooling,
measurement, e.g. for process control and safety systems and inhibition.
Gas is injected via the operating wells into the pores of a reservoir or into a cavern, thus building up a
reservoir of compressed gas.
Gas is withdrawn using the operating wells. With progressing gas withdrawal, the reservoir or cavern
pressure declines according to the storage characteristic. For withdrawal, re-compression may be
needed.
See Figure 2 for the injection mode and withdrawal mode.
The working gas volume can be withdrawn and injected within the pressure range between the maximum
and minimum operating pressure. In order to maintain the minimum operating pressure, it is inevitable
that a significant quantity of gas, known as cushion gas volume, remains in the reservoir or cavern.
The storage facility comprises the following storage capacities:
— working gas volume;
— withdrawal rates;
— injection rates.
The technical storage performance is given by withdrawal and injection rate profiles versus working gas
volume.
Recommendations for the design, construction, testing and commissioning, operation and abandonment
of underground storage facilities are described in Clauses 5, 6, 7, 8 and 11.
Construction of a storage facility begins after the design and exploration phase and should be carried out
in accordance with the storage design, which applies proven experience from the oil and gas industry.
For specific elements of an underground gas storage facility, e.g. wells and surface installations, existing
standards should be applied.
Key
1 filter 9 gas heaters
2 gas metering 10 control room
3 compressors 11 manifold
4 coolers 12 solid and liquid separation
5 oil separator 13 storage well
6 gas conditioning (e.g. glycol) 14 gas transport system
7 glycol regeneration - - - - - withdrawal with compression
8 pressure reduction ……… injection without compression
Figure 2 — Example of flow path injection (above) and withdrawal (below)
4.3 Injection facilities
4.3.1 Liquid and solid separation
Liquids and solid particles that the gas stream may contain should be removed by filters and/or
separators to prevent damage to or incorrect operation of the equipment.
4.3.2 Gas compression
Compression will normally be required to inject gas into the storage reservoir and cavern, unless the
storage system pressure is lower than the pressure in the supplying transport system. Gas or electrical
power may be used to drive the compressors.
4.3.3 Gas cooling
After compression, the natural gas is cooled to ensure the maximum temperature allowable for
equipment like separators, compressors, piping, subsurface installations, etc., especially for the
protection of pipe coatings, is not exceeded.
In order to maintain the pressure of the stored LPG at a suitable level, cooling of the incoming LPG or
condensation of the vapour phase may be required.
4.4 Withdrawal facilities
4.4.1 Prevention of hydrate formation
Hydrate formation in a gas stream of known composition can be predicted by means of experimental data
or calculated using vapour/liquid/solid equilibrium constants.
The formation of hydrates can be prevented by inhibiting, heating and/or dehydrating the gas.
4.4.2 Solid and liquid separation
Natural gas withdrawn from underground storage may contain solids and/or liquids that shall be
separated before the treatment facilities.
4.4.3 Gas heating
To avoid excessively low temperatures due to pressure reduction heating may be required.
4.4.4 Pressure reduction
Pressure reduction from wellhead pressure to the transmission system pressure may be obtained by
specific equipment, for example control valves, choke valves or expanders.
4.4.5 Gas conditioning
Gas from underground gas storage facilities may contain water and shall be dehydrated to meet the
required water dew point specifications.
Gas from underground storage facilities may contain higher hydrocarbon components and shall be
treated to meet the hydrocarbon dew point.
Gas from underground storage may contain minor components (e.g. hydrogen sulfide, carbon dioxide,
carbonyl sulfide) that shall be reduced to the required concentrations according to the gas specification.
If the specification requires LPG with a water content below that in saturated conditions, then a
dehydration of the LPG may be required.
Each component to be reduced may require a separate and different conditioning process.
4.4.6 Re-Compression
The operating pressure of the storage is usually higher than the gas transport system pressure. Storage
facilities and/or plant may be operated at a pressure lower than the gas transport system pressure to
increase the working gas volume. In this case, compressors are required.
4.4.7 Odorization
If required, odorization of the gas leaving the surface facilities is done downstream of the gas processing.
4.5 Surface utilities
4.5.1 Treatment of recovered water
If required, equipment should be provided to treat water produced from the wells and recovered during
separation or conditioning before it is disposed of or reinjected.
4.5.2 Fuel gas system
A fuel gas system is required for the operation of gas fired equipment such as heaters, compressor drivers
or boilers.
4.5.3 Instrument system
An instrument air, a hydraulic or an electrical system may be required for the control and operation of
the surface and subsurface systems. They contribute to safety systems typically in combination with
spring loaded systems.
4.5.4 Corrosion protection
Suitable corrosion protection measures for all parts of the facility are necessary, such as, e.g. cathodic
protection, coating, insulation shelters, inhibition or material selection.
4.5.5 Power supplies
Suitable power supplies are necessary for the operation of all electrical equipment on site.
A backup system is required to operate the safety equipment.
4.5.6 Earthing
All points that generate electricity or modify system voltage shall be earthed. Earthing concerns the safety
of personnel and plant.
4.5.7 Gas analysis and metering
Mass and/or volumetric flow rates are normally measured and recorded when injected or withdrawn
into a storage facility. Gas analysis may be required to check gas quality before injection into or
withdrawal from a storage facility.
4.5.8 Others
Field flow lines, process control system, venting systems, inhibition system and, if applicable, flare.
4.6 Leaching and debrining facilities for salt caverns
Leaching facilities for salt caverns may consist of:
— system for leaching water delivery with
— water off take station(s) at the leaching water source with filters, pumps;
— water wells, if required;
— line pipe from the leaching water off take station(s) to the leaching plant;
— in some cases, water reservoirs or tanks;
— water injection pumps, filters;
— line pipe from the leaching plant to the well head(s);
— system for brine discharge with
— line pipe for brine discharges;
— in some cases brine reservoirs or tanks;
— brine disposal wells, if applicable;
— brine treatment when needed, including settlement and filtration units;
— brine discharge pumps, filters, dispersers;
— system for the cavern blanket with
— blanket storage, filters and pumps at the leaching plant;
— line pipe for the blanket from the leaching plant to the wellhead(s);
— separation equipment for the removal of blanket from brine, if required;
— a system for ensuring the safety of the facility including a shutdown system;
— equipment for process control.
A system for ensuring the safety of the facility during the first gas filling shall be provided.
Microbial intake during the leaching phase may be detrimental to later operation.
It should be controlled.
4.7 Liquified petroleum gas
4.7.1 Solid and liquid separation
For the treatment of LPG, specific equipment, for example separators or coalescers, may be used for the
removal of solid particles or water droplets.
4.7.2 Liquid transfer
Liquid transfer pumps may be required for the filling of LPG storage facilities.
4.7.3 Heating
LPG may be delivered to the storage facility under refrigerated conditions. To allow the fluid to be
warmed to a level suitable for the storage system, the surface facilities should include the installation of
gas heaters.
4.7.4 Cooling
In order to maintain the pressure of the stored LPG at a suitable level, cooling of the incoming LPG or
condensation of the vapour phase may be required.
4.7.5 Conditioning
If the specification requires withdrawn LPG with a water content below that in saturated conditions, then
dehydration of the LPG may be required.
4.7.6 Colourization
Prior to delivery of LPG, the contract specification may require colourization.
4.8 Environmental conservation
4.8.1 General
The storage facility shall be designed, constructed, operated and abandoned in order to have the lowest
reasonably practicable impact on the environment.
Emissions of stored gas or other fluids used or created in operation shall be minimized according to
applicable emission targets. Appropriate measures to minimize leakages shall be implemented.
NOTE Regarding emissions of stored gas or other fluids, local regulations or requirements can apply.
4.8.2 Methane emissions
4.8.2.1 General
As methane is a powerful greenhouse gas, methane emission management should be integrated in the
design, construction, commissioning, operation, maintenance and abandonment phase to minimize
emissions.
The methane emissions can be divided into 3 main categories:
— fugitives;
— vented;
— incomplete combustion.
As part of the methane emission management operators shall have procedures for monitoring and
reporting of methane emissions on a regular basis. Active measures shall be taken to prevent leakage by
implementing leak detection and repair programs.
For quantification of methane emissions, CEN/TS 17874 can be used.
4.8.2.2 Design phase
During the technical design phase, the following technical examples to reduce emissions should be taken
into account:
— use electric, air pneumatic or mechanical (e.g. valve actuators, valve controllers) rather than gas
operated (gas pneumatic) components or equipment;
— plan plant layout to minimize vent volume under any conditions;
— understand that emergency stops lead to emissions that in most of the cases cannot be avoided; that
the necessity of depressurization is minimized and that segmentation into depressurization sections
is evaluated;
— consider how fugitive emissions can be quantified to assist in maintenance scheduling;
— ensure that unavoidable methane venting is fully flared.
4.8.2.3 Construction and abandonment/decommissioning
For all phases including the conversion to another gas, means shall be applied to minimize emissions. For
example, the recompression or the flaring of that gas or other uses should be considered as an alternative
to venting. See Clause 6 for more information on construction.
During abandonment, means shall be applied to minimize emissions. For example, the recompression or
the flaring of that gas or other uses should be considered as an alternative to venting. See Clause 9 for
more information on abandonment.
4.8.2.4 Operation and maintenance
Leak detection and repair (LDAR) shall be applied regularly to the well heads.
During maintenance, emissions shall be minimized.
Ideally, monitoring devices are installed at crucial modules within the facility, that constantly monitor
possible emissions. If leak detection and repair campaigns should be carried out on regular basis; this
campaign should consist of 4 phases:
— potential leak identification, based on site characteristics and/or previous experiences;
— detection and potential quantification of the leakages;
— repair or setting of a repair program and the associated reporting / tracing of the leakages and the
repairs;
— leakage and repair validation.
NOTE This can be applied to existing storages too.
Diverse emission quantification strategies can be applied depending on the type of asset (see CEN/TS
17874). Concerning fugitive emissions, the requirements of EN 15446 should be applied or any other
reference methodology, if available.
Adaption of common procedures should be considered to minimize methane emissions (e.g. maintenance
related vent reinjection).
Wells should be built with remote controlled pressure monitoring devices. Monitoring of wells shall be
done according to well integrity management systems in accordance with ISO 1663.
4.8.3 Other gas emissions
The requirements of 4.8.2 can be applied to hydrogen and GHG emissions.
5 Design
5.1 General
Surface and subsurface installations shall be designed in an integrated way in order to achieve an
environmentally, economically and technically optimized layout.
Surface and subsurface installations shall be designed to control the process and used fluids at any
combination of pressure and temperature, to which they may be subjected within a determined range of
operating conditions. They shall conform to existing standards for the individual part of a storage system.
The key parameters and procedures at the connection with the gas transport system and the operative
cooperation with the transport system operator shall be considered.
Proven technology shall be used for analysis and calculations. All relevant data should be documented.
...
Questions, Comments and Discussion
Ask us and Technical Secretary will try to provide an answer. You can facilitate discussion about the standard in here.
Loading comments...