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Exploration in a mature basin requires a detailed classification and standardisation of rock stratigraphy to adequately comprehend the depositional history and prospect architecture. The pre-Quaternary Stratigraphic Nomenclature of the Netherlands compiled by Van Adrichem Boogaert & Kouwe in 1993 provided a consistent framework for use by the Dutch geological community. Over the past twenty years, new biostratigraphic techniques and continued exploration in the Netherlands have provided additional stratigraphic information. Based on this information the Late Jurassic lithostratigraphy in particular, shows significant inaccuracies. The Callovian-Ryazanian strata from the northern offshore of the Netherlands' territorial waters, termed the Central Graben Subgroup and Scruff Group, reveal a complex sedimentary history. The combination of non-marine to shallow marine lateral facies changes, repetitive log and facies characteristics in time, sea-level and climate change, salt tectonics and structural compartmentalisation hamper straightforward seismic interpretation and log correlation. Recognition of three genetic sequences by Abbink et al. in 2006 enabled an improved reconstruction of the geological history. Further improvements in refinement and reliability of the stratigraphy together with new information on the facies and ages of the successions and about the subsequent tectonostratigraphic development of the northern Dutch offshore area form the basis of the present revision. As a result, earlier lithostratigraphic models have been changed and new lithostratigraphic relationships and names are introduced in this paper.

A synthesis of the upper Moscovian sedimentological and palaeontological record of terrestrial habitats across the Variscan foreland and adjacent intramontane basins (an area which is referred to here as Variscan Euramerica) suggests a contraction and progressive westward shift of the coal swamps. These changes can be correlated with pulses of tectonic activity (tectonic phases) resulting from the northwards migration of the Variscan Front. This tectonic activity caused disruption to the landscapes and drainage patterns where the coal swamps were growing, which became less suitable to growth of the dominant plants of the swamps, the arborescent lycopsids. They were progressively replaced by vegetation dominated by marattialean ferns, which through a combination of slower growth and larger canopies resulted in less evapo-transpiration. This in turn caused localised reductions in rainfall, which further affected the ability of the lycopsids to dominate the swamp vegetation. These changes were initially localised and where the coal swamps were able to survive the lycopsids and pteridosperms show little change in either species diversity or biogeography, indicating that at this time there was minimal regional-scale climate change taking place. By Asturian times, however, the process had accelerated and the swamps in Variscan Euramerica became progressively replaced by predominantly conifer and cordaite vegetation that favoured much drier substrates. Except in localised pockets in intramontane basins of the Variscan Mountains, the last development of coal swamps in Variscan Euramerica was of early Cantabrian age. Further west, lycopsid-dominated coal swamps persisted for a little longer. The last remnants of the lycopsid-dominated coal swamps in the Illinois Basin disappeared probably by middle-late Cantabrian times, as the cycle of contracting wetlands and regional reductions in rainfall generated its own momentum, and no longer needed the impetus of tectonic instability. This tectonically-driven decline in the Euramerican coal swamps was probably responsible for an annual increase in atmospheric CO2of c. 0.37 ppm, and may have been implicated in the marked increase in global temperatures near the Moscovian – Kasimovian boundary, and the onset of the Late Pennsylvanian interglacial.

Middle Jurassic - Early Cretaceous strata are a target for oil and gas exploration in the Dutch offshore. During the initial stages of the ‘Late Jurassic’ offshore exploration, various oil fields and a few gas fields were discovered of which only one, the F3-FB field, proved to be economically viable. In the Northern Offshore of the Netherlands, latest Middle Jurassic (Callovian) - earliest Cretaceous (Ryazanian) strata are mostly limited to the Dutch Central Graben and Terschelling basins. Outside the Dutch Central Graben and the Terschelling Basin only thin veneers of these strata occur on the fringing highs such as the Schill Grund High and the Step Graben. The geology of this non-marine to shallow marine succession is complex. The combination of lateral facies changes, repetitive log and facies characteristics in time, sea-level and climate changes, salt tectonics and structural compartmentalisation hamper straightforward seismic interpretation and log correlation. The large number of lithostratigraphic units defined in the Stratigraphic Nomenclature of the Netherlands illustrates the complexity of this time-interval.In recent years, new biostratigraphic techniques and newly acquired stratigraphic data led to the identification of a series of events which can be related to the tectonic, climatic, environmental and stratigraphic development of the ‘Late Jurassic’ in the Dutch Central Graben and Terschelling basins. Based on these data, three stratigraphic sequences can be recognized. Sequence 1 (Callovian - earliest Kimmeridgian) records the initiation of the Dutch Central Graben, Sequence 2 (early Kimmeridgian - early Portlandian) that of the initiation of the Terschelling Basin. During sequence 3 (late Portlandian - Ryazanian) the Dutch offshore was draped by a regional transgression. These insights have directly impact on the exploration potential, which is discussed in two play concepts. The first is a strat-trap play in the fluvial/paralic sediments of Sequence 1 in the lows between the graben boundary and salt domes. The second example is the Spiculite play, which comprises a bioclastic sandstone reservoir at the top of a dome with a 4-way dip closure. These two examples highlight the necessity of understanding the paleoenvironment and geography for assessing the future exploration potential.

Globally, significant oil and gas reserves occur in so-called ‘barren red beds’. These sediments are generally deposited in a shallow to non-marine environment under arid (desert) climate conditions. In terrestrial basins, biostratigraphic analysis of plant microfossils (pollen and spores) is often effective in constraining static geological models. Unfortunately, such organic-walled microfossils are not preserved in red bed deposits due to oxidation, hampering stratigraphic correlation on both local (field) and regional scale. Although red beds occur throughout the geological timescale, examples with an economic interest are the Late Carboniferous, Permian and Early Triassic of Europe (Barren Measures, Rotliegendes, Bunter − Doornenbal and Stevenson, 2010), the Triassic of the United States, and the Permo-Carboniferous of the Middle East (Melvin & Sprague, 2006). Here, for the first time, we apply biogenic silica microfossils as a stratigraphic tool in the Permo-Carboniferous red bed sequences in the Southern North Sea. The combination of their qualitative occurrence, cyclic abundance patterns, and stable isotopic data provides the possibility to improve existing regional geological correlations, position regional unconformities, and to refine reservoir architecture models. We have applied the biogenic silica stratigraphy in two representative case studies in the Upper Rotliegend in the Southern North Sea Basin. The first example focuses on refining the basin infill model of the Upper Rotliegend and the second on detecting the position of the Base Permian Unconformity (BPU). Both aspects are critical for E&P activities in the Southern North Sea but are notoriously difficult to determine due to a lack of effective correlation tools in the red bed deposits. Permo-Carboniferous red beds in

Using paleontological and geochemical techniques the long-term temperature development of the central Arctic was documented from sedimentary records for the first time. With the help of the new paleo-climatic evolution a tectonic paleo heat flow prediction of the Kara Sea area was performed to show the influence of paleo temperatures on the temperature and maturity history of that region. © 2010, Society of Petroleum Engineers.

Permo-Carboniferous sandstones are important reservoir rocks for natural gas in the Southern North Sea basin. This is a mature area which makes tools for reservoir characterization and well to well correlation important for field optimalisation and ongoing exploration activities. Within the Permo-Carboniferous sandstone reservoirs of the Dutch on- and offshore there are two key questions which still need to be resolved. One regards the geological model for the basin infill, another is the detection of the Base Permian Unconformity (BPU), an important regional unconformity. Biostratigraphy is classically used to address these problems. As the traditional microfossil groups are absent in the Permo-Carboniferous redbed deposits, the application of biostratigraphy is seriously hampered. In this study, we present a new biostratigraphical tool based on biogenic silica microfossils (BSPs). This fossil group consists of siliceous plant remains which are preserved even under extreme oxidizing conditions. BSPs are present in the Permo-Carboniferous redbed sequences and are now for the first time used for biostratigraphical correlations. This new tool holds great potential for independent chronostratigraphical correlations in economically important redbed deposits worldwide. In this study the initial results from a case study in the Southern North Sea basin will be presented.

The Southern Permian Basin (also referred to as Central European Basin) is Europe s largest sedimentary basin. It is a typical intracontinental basin that evolved from latest Carboniferous to recent times and extends from eastern England to the Belarussian-Polish border and from Denmark to South Germany. The Southern Permian Basin Atlas (SPBA) project is a joint project between the Geological Surveys of Belgium, Denmark, Germany, The Netherlands, Poland, and the UK and is being supported by a wide range of E&P companies, government licensing authorities, universities and research institutes. The aim of the Atlas is to present an overview of the results of over 150 years of petroleum exploration and research in this basin area. As this gas and oil province continues to mature and with field sizes inevitably decreasing, more and more careful data integration and geoscientific effort is required to discover new reserves. The subsurface characterization provided in the Atlas will also be of great value to governments, researchers and other individuals interested in the deep subsurface.

Depletion of large volumes of natural gas, oil and water from hydrocarbon reservoirs may lead to movements of the Earths surface (tilt or subsidence). Observations of these movements (Interferometric Synthetic Aperture Radar (InSAR), leveling measurements) can provide a better insight on subsurface processes like reservoir compaction or the aquifer strength. A simple inversion approach does not usually provide a sensible solution due to the non-uniqueness of the inverse problem and the sensitivity of the inverse problem to small fluctuations in the data. This necessitates the use of all available prior information (geologic model, reservoir model) in the inversion procedure to better constrain the subsurface parameters. A time-dependent inversion scheme is adopted for resolving the spatial and temporal reservoir pressure drop from the surface subsidence observations. The innovative inversion method is effectively applied to one synthetic and two field cases (one from The Netherlands, one from North Africa). The results suggest that incremental gas reserves due to reservoir compartmentalization can be detected successfully.

Petroleum production is a relatively inefficient process. For oil production, it is, generally, less than 60 % effective on a macro scale and less than 60 % effective on a micro scale. This results, commonly, in an actual oil recovery of less than 35 %. Optimization of the production process will, therefore, have a significant impact on the supply of energy. At various locations in the world consortia have been set up to develop new technology that would help optimize the production process. In 2005 Shell, Delft University of Technology, and Netherlands Organization for Applied Research TNO have started the ISAPP knowledge centre. ISAPP aims to develop innovative solutions for petroleum production based on a closed loop integrated systems approach. The projects in ISAPP address both reservoir characterization issues and control issues. Apart from a short overview, this paper presents two cases from the ISAPP project portfolio: An optimal control example that shows how well head choke control can be used to prevent wax deposition during production; a reservoir characterization example that deals with production history matching and prediction of production from new wells.

The stratigraphy of the Lower Carboniferous in the North Sea area is relatively unknown due to the deep burial and the scarcity of wells penetrating these strata, as this interval is generally considered below the petroleum fairway. In 2001, Dutch onshore

Biostratigraphical re-analysis of palaeobotanical data from the De Lutte-06 well clarifies an earlier controversy regarding the stratigraphical interpretation of this well based on palaeobotanical and palynological analysis. Previous biostratigraphical studies suggested an early Westphalian D age for the major part of the De Lutte formation, with only at the topmost part of the well remnants of presumable but unconfirmed Stephanian deposits. New identifications of palaeobotanical samples illustrate the presence of plant macrofossil assemblages in the De Lutte Formation characteristic for the latest Westphalian D to the Stephanian B-C. These new palaeobotanical insights, therefore, confirm a younger age for the De Lutte Formation and are more in line with the earlier palynological observations from the De Lutte-06 well that suggested that the recovered palynofloras resembled typical Stephanian associations.

Recently, renewed interest in the hydrocarbon potential of Upper Carboniferous strata of the North Sea basin (and especially the Cleaver bank High area) led to an increased exploration activity in this area of the Dutch and UK offshore. The Upper Carboniferous deposits in the Cleaver Bank High area are characterized by a high lateral variability in sedimentological facies which makes prospecting for hydrocarbons difficult. Therefore, a high resolution stratigraphical framework in combination with a better insight in the distribution of sedimentological facies is needed to increase the exploration efficiency in this area. This is achieved by high resolution quantitative palynology on ten wells from the Cleaver Bank High area (Dutch offshore).

In the Northern Offshore of the Netherlands 'Upper Jurassic' strata are mostly limited to the Central Graben and Terschelling Basin. Outside the Central Graben and the Terschelling Basin only thin veneers of these strata occur on the fringing highs as the Schill Grund High and the Step Graben. The 'Upper Jurassic' strata are an important target for the oil and gas exploration. The geology of the non-marine to shallow marine strata is complex. The combination of lateral facies changes, repetitive log and facies characteristics in time, sea-level and climate changes, salt tectonics and structural differences hamper straightforward seismic interpretation and log correlation. A tectono-stratigraphic approach has led to the identification of three tectono-stratigraphic sequences. Sequence 1 (Callovian - lowermost Kimmeridgian) comprises the initiation of the Central Graben. Sequence 2 (lower Kimmeridgian - lower Portlandian) comprises the initiation of the Terschelling Basin. During sequence 3 (upper Portlandian - Ryazanian) the Dutch offshore is draped by a regional transgression. In this presentation the enhanced exploration potential resulting from the tectono-stratigraphic approach, is exemplified by two potential play concepts.

Based on recent vegetation distribution and an integration of macropalaeobotanical and palynological information, a palaeocommunity model is explored that may permit detailed interpretations of quantitative sporomorph distribution patterns in the Jurassic and Early Cretaceous of NW-Europe in terms of changes in palaeoenvironment (sea-level, climate). The conceptual model is based on the recognition of Sporomorph Ecogroups (SEGs) that reflect broad co-existing plant communities, viz. upland, lowland, river, pioneer, coastal, and tidally-influenced SEGs. In successive palynological assemblages, shifts in the relative abundance of SEGs are thought to be indicators of sea-level changes. Climatic changes may be recognised through significant shifts within the quantitative composition of individual SEGs.

Jurassic shallow marine to non-marine depositional sequences are among the most important economic targets in the North Sea. Detailed, ‘high resolution’ stratigraphy of these sequences has become a necessity in both predictive geological exploration models as well as in production reservoir models. In these paralic sequences, palynomorphs are the most abundant (micro) fossil group. Palynology is increasingly challenged to improve the biostratigraphic control, and to support the sequence stratigraphical framework. Based on a recently developed, conceptual Sporomorph EcoGroup model, the quantitative distribution patterns of terrestrial palynomorphs are grouped in six Sporomorph EcoGroups (SEGs), viz. Upland, Lowland, River, Pioneer, Coastal, and Tidally-influenced SEG. Application of the SEG model to data from a marginal marine, uppermost Callovian - Middle Oxfordian section of NAM well F17-4 from the southern part of the Central North Sea Graben allows the recognition of sea-level fluctuations and climate changes. A marked palaeoclimatic shift occurred in the earliest Middle Oxfordian. The relatively cool-subtropical, humid climate changed into a warmer, subtropical-tropical, drier climate. The sea-level reconstructions based on the SEG model are validated against a latest Callovian - Earliest Oxfordian depositional sequence.