The importance of gas as a driver of security of energy supply and the influence of the role it currently has and will continue having in the energy transition has stimulated the development of further research studies in unconventional sources of natural gas. Mature gas fields of coarse-grained fluvial reservoirs have already reached their production plateau and are in a production decline with high-water cuts.
The northwest gas province of the Netherlands contains low-permeable fine-grained fluvial deposits of which the reservoir architecture and connectivity have not yet been widely studied using the standard industry techniques. For this reason, the geomorphological and sedimentological characteristics of the Río Colorado fluvial system were used as a modern analogue to determine how the river avulsion process has generated the current fluvial topography and why its repetition has developed a vertical stacking pattern of thin but laterally extensive layers.
Differential Global Positioning System data, Google Earth Pro Imagery, and previous studies focused on the evolution analysis of river positions in this region, allowed the observation of multiple repetitions of avulsion river in an area of approximately 400 km2, describing the fluvial sediments on top of the lacustrine deposits and representing alluvial ridges with an average width of 1500 m. Moreover, a thickness variation between the fluvial and lacustrine deposits up to 2 meters was recognised over 25 km, and a very gentle gradient slope, from 0.02° at the apex of the fluvial fan to 0.0022° in the flattened section towards the Salar de Uyuni.
Borehole data from the West Netherlands Basin and surface data from the Río Colorado were integrated to construct a three-dimensional model that represents the characteristics of the fluvial deposits regarding geobody size, geometry, and potential connectivity. With this, and the distribution of porosity and permeability as a function of channel belt and alluvial ridge width resulted in reservoir volumes up to 2×〖10〗^9 sm^3.
Six wells were simulated to understand the production behaviour in channel belts, alluvial ridges, and floodplain sediments. Water saturation, pressure and streamline maps differ from well to well, and the model contributed to quantify the most efficient production rates per well location in the fluvial fan system. The results allowed to predict the communication between facies and how that connectivity reflected the resultant flow rates and recovery factors, showing the tough gas as potential secondary targets and prolonging the production stages of mature oil fields.

The Huesca fluvial fan contains a low gradient fluvial system with well-exposed, 3D outcrops. An outcrop study of low-sinuous deposits aims to provide a deterministic reservoir model that predicts correlation lengths, nesting and reservoir potential of thin-bedded fluvial reservoir sandstone in an overall low net-to-gross setting. To correlate the study area, centimetre accurate dGPS measurements of paleosols have been collected to calculate the tectonic dip. This was used to correlate lithostratigraphic logs of the area. Correlation lengths between wells are dependent on how spatial and continuous a paleosol has developed. Photo panels of the outcrop were analysed for net-to-gross ratio and distribution of channel and floodplain deposits. A clear distinction between high and low net-to-gross regions can be observed in the panels, which causes a lateral heterogeneity. This can be explained by the nesting of a river channel. Nesting can be caused by local avulsions triggered by crevasse splays of the river channel in combination with avulsion by annexation. The lateral heterogeneous character can have major implications on reservoir potential. The reservoir volume is dependent on the connectivity between the higher and lower net-to-gross regions. The heterogeneity also has an impact on reservoir modelling as there only is a limited subsurface expression from wells. Therefore, it cannot be known whether the higher or lower net-to-gross zones are being looked at for that particular fluvial system which makes estimates about reservoir volume difficult and inaccurate.

Geothermal energy is strongly dependent on the geothermal gradient; this means that with increasing depth an increase in temperature is found. The targeted formation of our research is the Hardegsen which reaches depths of around three kilometers in the West Netherlands Basin. At three kilometers depth the temperature is around 90 C˚ which is interesting for geothermal exploitation. However, rock at increasing depth generally shows a decrease in reservoir properties.
This study investigates whether the reservoir properties of the Hardegsen formation at a depth of three kilometers are still interesting for geothermal exploitation. This is done by determining to what extent the Hardegsen has been influenced by depositional history, diagenetic processes and inversion.
Determining the reservoir properties is done by studying a data set that consists of core descriptions, core plug measurements, gamma ray logs, microscopy analysis, literature studies and a field study. From the core plug measurements a simple model was created describing how porosity and permeability of the Hardegsen behave with increasing depth.
The Hardegsen succession in the West Netherlands Basin consists mainly out of (cross-bedded) arkosic fine to medium grained sandstones intercalated by 0.2-1 meter thick laterally consistent shales and shaly/silty very fine sands. High minus-porosities (up to 45 %) are reported which could have played an important role in the preservation of the reservoir properties. Core plug measurements show that the Hardegsen has good prospects for a potential reservoir with porosities ranging from 10-20% and permeability’s ranging from 50-1000 mD.
The presence of the laterally consistent shale and sandy/silty very fine sand layers is heavily dependent on the location in the reservoir. This research shows absence of these layers in wells that are located closer to the basin margin. Since these layers decrease vertical flow drastically, further investigation of the extent of these layers is needed to give a better prediction of the quality of the reservoir as a whole.

The sedimentary systems terminating in the Salar de Uyuni, hold modern days analogues for the Permian and Triassic thin-bedded crevasse-splay deposits. In the future, these crevasse-splay deposits could be of importance for hydrocarbon production in Northwest Europe. In this study, the possibility of using satellite data to construct geomorphological maps is investigated. In order to do this, QGIS is used to determine the watershed and river paths based on ASTER GDEM satellite data, and to classify the land cover based on Landsat 7 ETM+ satellite data. The results generated by QGIS are compared to open source available datasets and high resolution Google Earth Pro images. The watershed and river paths determined in QGIS are accurate for high relief areas. In low relief areas, the results are not trustable. Here, the watershed and river path results seems to be controlled by the errors in the ASTER GDEM data. The resolution of the used Landsat 7 ETM+ is not large enough to distinguish various rock types accurately. A map that indicates the amount of clay within the basin could be created using the Landsat 7 ETM+ images though. Lithological classification using satellite images is a promising technique, with a lot of applications. However, to perform accurate lithological classification higher resolution satellite images and more detailed lithological information is necessary.

A good understanding of the reservoir architecture of tough gas reservoirs is necessary to define their potential for the hydrocarbon industry. These tough gas reservoirs have been overlooked until now due to the high economic risks of development. These risks are mainly related to the large uncertainties that exist in the reservoir architecture. Understanding the depositional processes of crevasse-splays will help in minimizing the uncertainties in interpreting the internal depositional setting and deposition processes.
This research focuses on the mapping of thin bedded crevasse splays in a low-net-over-gross floodplain environment in the distal areas of the Huesca fluvial fan (Miocene) of the Ebro basin in Spain. This outcrop is a good analogue to the Permian Rötliegend and Triassic Bundsandstein intervals in the West Netherlands Basin. A field study of the Huesca fluvial fan is used to analyse the reservoir architecture (size, shape, spatial distribution and connectivity) of the reservoirs of fossil crevasse-splay deposits. At two outcrop locations an interval of crevasse-splay deposits is mapped, using detailed lithostratigraphical logs, a type section log, photo-panels and lateral characterizations of sand beds. With these data a correlation panel is constructed to determine the connectivity of the mapped layers, and cross-sections are made to determine the lateral continuity, vertical stacking and grain-size variations.
On a single layer level, results show both a decrease in bed thickness and in grain size from proximal to distal, related to the energy of deposition. Grain size is also related to distributary-channel proximity, decreasing away from the distributary crevasse channels. In multi-storey stacked sheets, incision of distributary channels into underlying crevasse deposits near the crevasse apex creates sand-on-sand contact. The approximation of a crevasse splay as a simple accumulation of homogeneous sheet like layers should be refined in order to lower the uncertainties in the tough gas reservoir model. A quantitative dataset for the size, shape and stacking patterns of crevasse splay sandstone is composed, which can be used as an input in static reservoir models.