prEN 1918-4

This document covers the functional recommendations for design, construction, testing, commissioning, operation, maintenance and abandonment of underground gas storage (UGS) facilities in mined rock caverns up to and including the wellhead.
This document specifies practices which are safe and environmentally acceptable.
For necessary surface facilities for underground gas storage, EN 1918 5 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).
Gases that are liquid in subsurface conditions are not considered in this document.
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.