Most hydrocarbon resources on the Norwegian Continental Shelf occurs within porous sandstone reservoirs. When sandstones are buried to depths greater than c. 3 km, pore space starts to become filled in by quartz cement. This reduces the reservoir’s ability to store fluids. For this reason, deep reservoirs are very risky exploration targets. In some cases, however, reservoirs buried down to 5 km can have excellent properties because the grains are coated by the mineral chlorite. This coating inhibits development of pore-filling quartz cement and may preserve good reservoir quality at great depths.
At present, no geological concept or technology allow us to predict whether a reservoir has chlorite coating or not. This is problematic for two reasons: First, finds in deep prospects close to existing infrastructure may be economically viable and extend operations at existing installations. But without a reliable predictive tool for distribution of chlorite coats, such targets might be considered too risky. Secondly, chlorite has the potential to mineralize CO2, which is a great advantage for CO2 storage. Without models to predict the distribution of chlorite in subsurface reservoirs, permanent storage of CO2 can be difficult to assess.
DeepReservoir will develop new ways to predict the presence of chlorite coatings. World-class geological exposures with chlorite-coated sandstones are present in east Greenland, and we will conduct expeditions to these outcrops to investigate the nature of chlorite-coated zones and why it occurs here. We will also study subsurface examples of chlorite coats from the Norwegian Continental Shelf| and examine modern environments where chlorite is abundant.
In 2023, we will hire the necessary personnel, have our inaugural meeting between project partners, work on subsurface data to build experience in the group, conduct the first of two expeditions to east Greenland, and start analyzing the field data.
With the largest and most easily accessible hydrocarbon resources on the Norwegian Continental Shelf already discovered, the future of Norwegian exploration lies in developing deeper and technically complex prospects close to existing infrastructure. Reservoir quality generally decreases with depth, leading to greater uncertainty in deeper prospects. However, some reservoirs contain sand grains coated with the mineral chlorite, which inhibit cementation and preserve excellent reservoir quality at great depth (3-6 km). It is difficult to predict where good reservoir properties are preserved with current models, and measures that can improve the predictability of chlorite coats in deep reservoirs will increase the commercial discovery rates, delay decommissioning, and maintain the competitiveness of the NCS. Chlorite-coated reservoirs, and reservoirs with precursor clays to chlorite coats, are well-suited storage sites for CO2 because chlorite promotes rapid, permanent mineralization of CO2. The DeepReservoir project promotes future value creation on the NCS by developing knowledge important for screening the potential of subsurface aquifers.
In this project, we will map the distribution of chlorite coats on the NCS and investigate the processes controlling porosity preservation in deeply buried reservoirs. We will do this by investigating data from subsurface fields and utilize the globally unique outcrops on E Greenland, where chlorite-coated sandstones can be studied in unprecedented detail, and the well-studied modern occurrences of chlorite coat precursor clays in the Ravenglass Estuary, UK. To combine findings into a predictive model, we will integrate sedimentology, petrography, geophysics and hydrodynamic modelling in both subsurface, outcrop and modern analogue systems. This integrated approach was selected as the answers to our research questions lie in the intersection between these disciplines.