Why do we store geological core?

In a warehouse just outside Nottingham, vast racks of geological core are carefully curated and stored in climate-controlled conditions. Part of the collections held within BGS’s National Geological Repository (NGR), this core is quietly energising the UK’s economy, supporting the nation’s growth agenda and energy transition aspirations.

Understanding our subsurface environment requires both direct observation, through samples such as drill core, and indirect observation, through sensors and monitoring. These observations are the basis on which we build models that constrain and test hypotheses explaining the Earth, its composition and its many processes. Such knowledge is critical for determining how society is affected by or can safely interact with the ground beneath our feet.

Saving cost, reducing risk and accelerating project timelines

Drilling new core is expensive. The cost of drilling just one new offshore borehole can be in the region of £20 to £30 million, around 20 times more than the annual operational costs for the NGR. Access to existing core can therefore significantly streamline the process for new infrastructure projects; it allows both public and private sector project managers to plan with a greater degree of certainty and better mitigate risk. More informed planning can result in drilling fewer new boreholes and a shorter project timeline. This not only saves significant costs; it also reduces any associated environmental impact.

Digital scanning has unlocked new opportunities … with limitations

Digitisation of rock samples and core is a powerful tool for the modern-day geologist. Improvements in analytical techniques, including core scanning and 3D imagery, allow cores to be re-studied and preserve a record of the original material prior to sampling. These advancements are providing scientists with better opportunities to investigate changes in physical properties such as porosity (the free space inside a rock that fills with fluids).

An array of scanning technologies, including X-rays and hyperspectral imaging, allows scientists to extract more data than ever before from samples. Collectively, this data, sourced from different analytical techniques, can be compiled into digital geo-specimens that enable exciting opportunities through machine learning and artificial intelligence tools. However, there is a cost associated with scanning and digitisation. With the size of the core archive, these activities need to be targeted to deliver the largest benefit to the UK.

Although geological observations and digital samples have significant long-term value, they are limited by the context in which they were collected and the technologies available at the time. Discarding physical samples after digitising risks losing the ability to re-examine them with new techniques and technologies as they emerge in future. Digitisation enhances the samples, makes them more discoverable, and increases their value, but is not a replacement for holding physical specimens.

Safeguarding for the future

What society needs from the subsurface changes over time. The academic and commercial relevance of core varies and does so in ways that can be hard to predict. Many of the reservoir cores from the Southern North Sea gas fields, which were drilled in the 1960s and 1970s, are now being re-studied to assess their potential for carbon dioxidestorage. Sites that were once prized for their coal reserves are now being revisited for geothermal potential. These uses were almost certainly never envisaged when the core was originally drilled.

In some cases, the core may be unique and irreplaceable, especially where land has since been developed or reclassified (for example, as a Site of Special Scientific Interest). Maintaining a reference library of boreholes enables future research to take place using new techniques, saving time, reducing costs and limiting the environmental impact. Crucially, it also supports reproducible and repeatable science.

Physical space within the NGR is always a consideration. It is not possible to retain every specimen we are offered. Material is selected based on its value to inform the geological record. Sometimes, materials may be discounted or discarded where there is an abundance of material from a particular area or where samples have deteriorated, but such instances are rare. BGS is actively exploring funding opportunities to expand this national facility, so that we can continue to ingest materials critical to the UK economy.

Over the last two decades, it is estimated that the NGR has saved the UK economy at least  £1.5 billion in avoided drilling and analysis costs alone. The importance of this facility can only increase as we maximise the potential of geological ‘super regions’ for renewable energy technologies.

As demand for natural resources grows and the effects of climate change intensify, so does the need for geological data to address the economic and societal challenges. All indications are that the most important phase of the NGR is yet to come.