Why is this research needed?

The Bunter Sandstone is an important saline aquifer in the Southern North Sea which is planned to be used to permanently store carbon dioxide (CO2) from anthropogenic emissions. Knowledge about this geological aquifer and its properties is vital for the progress of CO2 storage and therefore the UK’s energy transition to net zero.

This study will take data from a depleted gas field within the Bunter Sandstone. This includes pressure data from when the gas was produced, pressure data from a well drilled 13 years after gas production ceased (this can tell us how much pore fluid re-entered the gas field) and pressure data from a well 12.5 km away (this can help us understand how well connected the aquifer is).

Numerical flow models will be used to model the gas depletion and subsequent pressure recovery. The parameters representing the properties of the aquifer (permeability, connectivity, porosity, etc) start with estimates that are already available to the CCS community but include a level of uncertainty. These can be tuned until the model fits the real data, giving an improved estimate of the properties of the aquifer.

This increased level of understanding of the Bunter Sandstone can then be taken forward as operators prepare to inject CO2 into the aquifer. An important consideration from the connectivity that will be studied in this project is the impact that CO2 storage operations can have on neighbouring sites or other uses of the subsurface.

What is this research investigating?

Estimating and verifying the permeability, connectivity and other properties of the Bunter Sandstone in the Esmond area through history-matching with pressure data.

What does the research hope to achieve?

Operators holding CO2 storage licenses in the region near the Esmond field who are targeting the Bunter Sandstone are depending on the permeability and connectivity of the aquifer. This study seeks to provide some additional verification and reduce uncertainty for the parameters that are already known to an extent.

Regulators have an interest in the whole wider aquifer, including current and potential future license areas. It is important to know how wide the radius of influence is for each project and this is one of the main parameters focused on in this study.

This study seeks to characterise how wide an area was influenced by the gas production of the Esmond field. Going forward this parameter can be used to help estimate how neighbouring projects might interact with each other.

Using available pressure data for history matching and characterising the subsurface can lead to other similar studies. For example, there is also pressure data available from near the Caister field and a similar study would be beneficial to test how laterally widespread the connectivity of the Bunter Sandstone is.