The impact of oil and, in particular, gas fields discovered in the Dutch subsurface has been very significant. However, 50 years after the discovery of the giant Groningen gas field the Netherlands has become very mature for exploration of oil and gas, and the gas volume left to be discovered in conventional traps is insignificant compared to what has been found already. The total portfolio of conventional prospects held by the industry contains several 100s of billions of cubic metres (bcm), as reported by the Ministry of Economic Affairs, but many of these prospects are unattractive to drill because of their small size or other geologically unfavourable aspects. Hence, for planning purposes of future national gas production the risk should be taken into account that the size of the conventional portfolio is overestimated. The major E&P companies have reduced their exploration efforts and the number of wells drilled as well as the size and total volume of discovered gas reserves has seen a steady decline over the last 10 years. Some surprises may still be in store and can occasionally add a welcome addition of gas. But the follow-up potential of new play and trapping concepts has been disappointing for many years now, and it is concluded that this is unlikely to be different in the future. Remaining conventional discoveries will mainly be in small near-field targets that as a result of technological advances made in the last few decades can be drilled with high confidence, despite their small volumes.

This leaves the so-called unconventional gas (UG) resources for a real and significant increase in the exploration potential of the Netherlands. UG resources occur outside conventional structural or stratigraphic traps in tight (low permeability) rocks and are of regional or sub-regional extent, without well-defined hydrocarbon-water contacts. The potential for Basin Centred Gas, Shale Gas and Coal Bed Methane is reviewed. As, according to present-day technology, development of UG requires very dense drilling at low costs with well spacing of a few 100s of metres, only the onshore potential can be commercial, even in the longer term.

Recent geological uplift is a characteristic for all North American commercial UG developments. Uplift helps bringing the resources close to the surface and facilitates development of fractures, which are essential for achieving commercial flow rates. This significantly reduces the area where commercial UG resources may occur in the Netherlands. In addition, sweet spots, where commercial flow rates and ultimate recovery per well can be achieved, represent only a fraction of the total ‘play area’. The UG plays in the Dutch subsurface remain to be proven, and there is still a significant technical risk associated with these plays, on top of the commercial risk. Therefore, despite potentially enormous in-place gas volumes in these unconventional plays, recoverable volumes are much less. If UG resources can be proven and are commercially developable, their cumulative volume potential is estimated by us in the order of a few tens to one or two hundreds bcm of recoverable gas at best. Finally, as UG resources produce at very low rates and require large numbers of wells to develop, the environmental impact in a densely populated country like the Netherlands is enormous, and needs to be seriously considered, already in the exploration phase.

In a mature area like the Netherlands, industry focus should be on technology development to reduce risk, increase recovery, reduce cost and minimize surface impact. Cooperation between Operators to build multi-well campaigns is therefore strongly recommended to reduce mobilisation cost. In addition, government incentives should be targeted at the development phase, in order to increase economic attractiveness for difficult reservoirs, both conventional and unconventional. In this way State and industry will both be able to maximize their returns on the remaining potential for gas and oil in the next two to three decades.

Recent studies have demonstrated the complex depositional history of the Vijlen Member (Gulpen Formation) in the Maastricht-Aachen-Liège area, on which synsedimentary tectonics had a profound impact, in conjunction with regressive and transgressive episodes, the oldest portion of this member being preserved only locally, within channel-like structures. Our reinterpretation of the Vijlen Member, here presented, is at variance with current belemnite stratigraphy. To account for incongruities, reworking of belemnites is here proposed as a typical feature during Vijlen Member deposition. A renewed study of belemnites on the basis of these new data suggests that intervals 4–6 of the Vijlen Member are of late Maastrichtian age. With respect to the mean values of populations of Belemnitella junior Nowak and Belemnitella Iwowensis Naidin, Vijlen Member intervals 4–5 are coeval with the Spyridoceramus tegulatus/Belemnitella junior Zone (sensu germanico), whereas at least the upper portion of interval 6 is correlatable with the basal Tenuipteria argentea/Belemnitella junior Zone (sensu germanico). Although reworking of belemnites appears to have been a common feature, this cannot be properly substantiated without additional geochemical analyses of individual guards. For this reason, we refrain from proposing a biostratigraphic zonation of the Vijlen Member based on belemnites. Alternatively, scaphitid ammonites might be used to subdivide this member, because species such as Acanthoscaphites (Acanthoscaphites) tridens (Kner), A. (Euroscaphites) varians blaszkiewiczi Jagt, Kennedy & Machalski, Hoploscaphites constrictus (J. Sowerby), H. tenuistriatus (Kner) and Hoploscaphites sp. have been recorded. The last-named taxon represents an interspecies hybrid between the North American Jeletzkytes dorfi Landman & Waage and an unidentified subspecies of the endemic European lineage of H. constrictus, allowing correlation of the lower portion of Vijlen Member interval 6 with the Hoploscaphites birkelundae Zone of the United States Western Interior.

This paper reports the discovery of an in-situ striated, far-travelled, oversized clast in the Ardleigh Gravels of the Kesgrave Sands and Gravels of the River Thames at Ardleigh, east of Colchester in Essex, eastern England. The morphology, petrography and geochemistry of the clast, and the sedimentology of the host deposit are described. The striations are interpreted, on the basis of their sub-parallelism and the shape and sub-roundedness of the clast, as glacial and the clast is provenanced to Ordovician rocks of the Llŷn and Snowdonia regions of North Wales. On the basis of clast frequency within the Colchester Formation gravels of the Kesgrave Sands and Gravels it is inferred that glaciers reached the Cotswold region of the Thames catchment. Floe-ice transport during spring flood is invoked for movement from the glaciated region to eastern England. The paper discusses the possible age of the glaciation and recognises that it is difficult to be more precise than a cold stage in the early Middle Pleistocene (MIS 18, 16 or 14). Attention is drawn to the possibility of glaciation associated with a diamicton in the region of the Cotswold Hills known as the Bruern Till, but stresses the need for new work on this deposit.

The youngest representatives of ‘true’ (= non-tegulated) inoceramid bivalves (Inoceramidae) are described from intervals 3-6 of the Vijlen Member (Gulpen Formation), of late early and early late Maastrichtian age, as exposed at quarries and temporary sections in northeast Belgium (CPL SA-Haccourt and CBR-Lixhe quarries) and the Aachen area (Germany), i.e. the extended type area of the Maastrichtian Stage. In total, twelve taxa are recognised from levels which are correlative with the Calcaire à Baculites of Manche (France), as well as with the Tercis les Bains section in southwest France, the Wisła (Vistula) River sections (central Poland) and the Western Interior of the United States. Associated cephalopods allow a detailed correlation between biozones based on those groups and on inoceramid bivalves.

During the 2007 ‘Kor en Bot’ collecting trip across the Oosterschelde (province of Zeeland, southwest Netherlands), on board trawler cutter ZZ10, a stem fragment of a fossil isocrinid was recognised amongst the contents of the nets pulled on deck. This specimen is here interpreted to be of Early Jurassic age and assignable to the genus Isocrinus. However, because only internodals are preserved in this pluricolumnal, specific identification cannot be but approximate (Isocrinus (Chladocrinus) cf. tuberculatus). In the absence of any outcrop of Jurassic deposits in Zeeland and adjacent Dutch and Belgian territory, the most likely explanation is that this crinoid represents erratic material transported by precursors of the present-day River Maas (Meuse). Between the Langres Plateau and Sedan (northeast France), this river cuts through several occurrences of Lower Jurassic strata from which the present isocrinid might have originated. A less likely explanation is that it stems from boulders used for coastal reinforcement or from a Roman limestone votive altarpiece put up at the temple complex for the goddess Nehalennia, formerly present at Colijnsplaat, near Domburg (Noord-Beveland, Zeeland). Transportation from either northwest France or the southern or eastern United Kingdom, where there are coastal exposures of Jurassic strata, via the North Sea, is another option which, however, is also considered less feasible in view of the good state of preservation of the crinoid.