Research and application areas

Supporting and accelerating the energy transition through experimental research

An overview of the research focus and applications of RCSG

The RCSG tests, develops and demonstrates innovative technological solutions for underground applications to enable the energy transition, a shift from the use of fossil fuels to sustainable energy generation. An effective scaling up of these options in the Netherlands requires a significant cost reduction in order to increase the economic feasibility. At the same time, transparency and security are necessary preconditions to obtain maximum social and political support in the Netherlands. Due to rapid technological developments in the field of materials, sensors, semiconductors, production techniques and IT, many new products have been developed and are under development. For the development of sustainable technologies, it is essential to be able to use the latest technology in the subsurface. The challenge here is to demonstrate this technology, materials and products under conditions similar to those in the subsurface (such as temperature, pressure, etc.). Furthermore, scaling up of technology is one of the main challenges. Research facilities are therefore required where these technologies and systems can be studied and tested on a realistic scale and under these conditions. Not all innovations can be demonstrated directly in a commercial environment. The facilities at RCSG offer the opportunity to test and demonstrate in full-scale, in a controlled environment that approaches practice as closely as possible. The following programs are currently being implemented at the RCSG, for the following areas of application.

Demonstration and development of new drilling technologies

In a densely populated country like the Netherlands, surface space is scarce, while many sustainable solutions require a lot of space. It is therefore very important to use the scarce space as efficiently as possible. For underground applications, this means that as much energy as possible must be generated per available surface location, or that, in the case of storage, as much liquid or gas as possible can be introduced into the subsurface per location. This, while keeping up the highest standards around safe execution of operations. For the individual wells this means that innovations have to be implemented that make this possible, such as a larger diameter, the possibility to operate at higher pressures and the tapping of a larger part of the reservoir, for example by drilling horizontally instead of vertically. Existing technologies are often unable to provide the required properties, or only at high cost. The RSCG is therefore researching new technologies that are considered capable of cost-effectively delivering these drillings, and has a fully operational drilling platform and a highly advanced drilling machine that can be used for testing.  Since the drilling costs usually make up the largest part of the investments (CAPEX), it is possible to achieve large gains here for a better business case for sustainable energy projects. For the execution of a successful drilling project, the removal of the drill cuttings to the surface is crucial. Various installations of the RCSG are specifically designed for research into the transport of this drill cuttings under different conditions, resulting from the chosen drilling technique. To finish a well, a casing must be installed to prevent the borehole from collapsing. It is common to use mainly steel for deep drilling. Alternative designs or materials are being investigated for new applications because they are cheaper or, for example, better suited for transporting large volumes of water by being more resistant to corrosion. Because these alternative casings must also meet the requirements, large-scale strength tests are carried out at the RCSG.

Interaction between well and surrounding rocks (near-well domain)

The transfer of liquid in the subsurface between the reservoir and the well is decisive for the final performance of the installation of any subsurface technology. This transfer is determined by the properties of the well and the direct environment of the well (near-well zone), which consists of the surrounding rock, the space, whether filled or not, between the pipe or filter, the pipe or the filter itself, and the liquid in the tube. In this zone, a pressure gradient or a temperature gradient is generally created that initiates the flow. However, these gradients can also trigger processes that affect or complicate the flow, such as precipitation of materials and/or production of sand or clay that clog the entrance. This behavior in the zone around the well can be experimentally investigated at full scale at RCSG with set-ups in which the liquid flow in the near-well zone is simulated and investigated.

Safe sealing of wells during and after production

If the surface is connected to the subsurface by drilling the well, it must be ensured that the withdrawal or injection of liquids only takes place in the way and place necessary for the application. It must therefore be prevented that there is an outflow of liquids (under pressure) on the surface or in the soil other than in the reservoir and in the above-ground facilities. For example, no mixing and/or contamination of fresh aquifers or surface water with saline formation water may occur. Therefore, when completing the well, care must be taken to ensure that the space between the casing and the borehole (the annular space) is properly sealed in the path between the reservoir and the surface. This is done by injecting cement (in deep wells) or overfilling with sealing materials (in shallower wells). RCSG investigates the properties of this cement layer, looks at alternatives to cement (for example natural (clay) materials), tests the different methods for placing the cement and also investigates options for carrying out repairs in the well if this is necessary. In addition to sealing the annular space when the well is constructed it is essential to be able to seal the well itself to prevent outflow during use, with a temporary plug, or after use, with a permanent plug.

Over 4,000 wells have been drilled in the Netherlands for oil and gas exploration and extraction over the years, of which only slightly more than half have been properly completed and abandoned.  Over the next 10 years, dozens of wells are scheduled to be “abandoned”. The RCSG is investigating the placement of plugs and is looking in particular at alternative materials to use instead of the usual cement plug. These tests are performed with specific setups before full-scale testing is carried out on the platform. Because an abandonment is irreversible, it is important to measure and record as much subsurface data as possible. 

Flow from wells for an optinal energy system

Flow of liquid (or gas) will always have to be used in order to make use of the subsurface for the energy transition. These flows must be integrated as effectively as possible with the other parts of the system to optimize an energy or storage system. Where, for example, flow from the subsurface often benefits from a stable flow rate from the well, the supply or demand from the aboveground part (for example, heat) is often more variable. Research into flow through the system is therefore important. On the technology side, the RCSG looks, for example, at the behavior and performance of the pump in the well (Electric Submersible Pump, or ESP). Important physical processes to investigate are scaling, erosion, corrosion, clogging, sand production, solubility of gas (CO2) in water and the required injection pressures, etc. A set-up will soon be realized at the RCSG with which full-scale research can be carried out at high temperature and pressure. Research into the behavior of CO (and related temperature effects) is important for CO storage in empty gas fields, which is important in the Netherlands.  

Data acquisition for monitoring performance and safety

Measuring is knowing. This also applies to all aspects surrounding the performance of the well and the immediate vicinity of the well. The RCSG focuses on measuring and recording various data (temperature data, pressure data, strain data, flow data, etc.) around the well and smart technologies and well designs to be able to measure in the well. For this purpose, sensors and meters must be placed on, in and along the well. Fiber optic cables have been increasingly used in recent years for retrieving information and a fibre optic cable will also be installed at the RCSG to a depth of 200m where continuous measurements can be made (e.g. temperature). There is also a “smart casing” program at the RCSG, which is investigating the best way to place sensors in and along the casing.

In collaboration with other groups in TNO, research is also being carried out into the processing and storage of large experimental data sets and how they can be interpreted, e.g. via Artificial Intelligence techniques. 

Re-use of existing infrastructure

With the depletion of the gas fields and the phasing out of fossil fuels, many wells will be taken out of use in the coming years. Before abandoning them permanently, it is useful to evaluate whether these wells and the associated infrastructure can be used in a meaningful way to support the energy transition. Think of the reuse of wells for the injection of COor the conversion of gas wells to geothermal wells. For the latter, it may be important to drill into a shallower reservoir from the existing well. Testing and development of cost-effective tools for extracting water from former gas wells with small diameters, or possibilities to increase the diameter locally, are also of interest. At the RCSG, testing can be done in the shallow well or in the deeper research well.

Social development and education around the energy transition

This research area mainly considers the activities undertaken in cooperation with the Energy Cave.