This paper gives a description of the capacity gap that Gasunie is facing in the near future due to the depletion of the Croningen field. It addresses the method used to study how this gap can be filled in the most economical way. The method uses supply and demand figures to set up a capacity balance and uses associated LDCs for volume calculations. Some details are given upon the capacity measures that already have been taken.

Background information

The natural gas era in the Netherlands, and actually in western Europe, started with the discovery of the giant Groningen gas field in the late 50's. After the discovery, it gradually became clear that the field could have an enormous impact on the energy situation in western Europe. On the other hand, at that time it was also believed that nuclear energy was the most promising future source of energy and that this energy would become very cheap. As a consequence the gas in the Groningen field would have to be sold very quickly in order to be of any economic value. The first energy crisis in 1973 and the second a few years later changed this situation. Moreover, there was a growing awareness that nuclear energy would not play the role that was hoped for (Harrisburg, Chernobyl). As a result of all these developments, the policy of the Dutch government switched from selling as much gas as quickly as possible to energy conservation and thus to conservation of the Groningen field as long as possible. Tax measures were used to stimulate exploration and production from other fields. This so-called small fields policy turned out to be quite successful : today, only 40 % of all the gas produced in the Netherlands originates from the Groningen field; the other 60 O/O comes from small fields (see graph below). It must be remembered that the composition of Groningen gas differs significantly from that of other fields. Groningen gas (G-gas) contains some 14% nitrogen, which leads to a Wobbe index of 1200 Btujft-' (44 Ml/m3), while gas from other fields (H-gas) has a Wobbe index of around 1350 Btu/ft' (50 MJ/m3). The gas equipment in the markets that was supplied initially from the Groningen field had been adjusted to its specific Wobbe index; the gas from the new fields had to be accommodated in such a way that the major markets could still be supplied with (pseudo) Groningen gas. Some markets, such as large industries, power plants and some export clients switched to the higher Wobbe index. The Dutch gas transmission system was adjusted in such a way that two separate transmission systems emerged (one for G-gas and one for H-gas) with several mixing stations (some equipped with nitrogen facilities) to inject H-gas into the G-gas system. The transmission system thus became very complex (see attached map).

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