Until 31 December 2001 Gasunie employed a transport system in which the tariff was determined on the basis of the distance between the entry point and the exit point, the Commodity Service System (CSS). In consequence of a binding instruction from the DTE , Gas Transport Services promised that it would change to an entry/exit system. The entry-exit system is such that transport through the pipeline system is not directly related to distance.

If a shipper wishes to have gas transported through the Dutch system he must contract for the entry and exit capacity: in this way the right to be able to use a specific capacity at a contracted point is bought. The gas transport service amounts to the following: an agreed amount of gas at the entry point is provided according to agreed quality specifications, and then at the same moment GTS delivers gas at the contracted exit point, also being the agreed amount and according to agreed quality specifications [1]. In order to maintain the integrity of the pipeline system, it must be ensured that the entry and exit capacities are sufficiently balanced. With regards to L gas this results in the commitment of a shipper to supply the same amount of L gas at the entry points as claimed at the exit points on a calorific basis. The balance between entry and exit capacities also applies to H gas, although the shipper then is also allowed to supply more H gas then actually claimed, as the H gas can always be converted to L gas quality by adding nitrogen to the gas.

Due to the nature of the gas trading system the preferred location of SNG injection in the grid, beside the potential advantage of metering and regulating point of view, is again the HTL network as this network is fed with gas from numerous fields, which already might enable a shipper to balance his entry and exit capacity more easily in case of temporarily lack of SNG production (e.g. disruption of the gasification process). In case of SNG injection in the RTL network this balancing might be more difficult. The advantages of metering and regulating, trading as well as economy of scale (i.e. injection in the HTL network allows large scale SNG production facilities) cause the disadvantage of SNG injection in the HTL grid, i.e. the gas quality commitment to multiple consumers, to be of less concern as long as SNG is produced at a constant specification, suitable for grid injection. The projected scale of a SNG production facility will preferably be consistent with current gas fields, hence approximately 500-1000 MWth (synthetic) natural gas.

References:

1. Gas Transport Services (GTS), 2006 (www.gastransportservices.nl).