Subsurface flows

Fluid flows in the subsurface play a central role in water resources, energy resources, and geophysics. Our current research focus is on reducing the environmental impact of fossil fuels.

Academics

Geological carbon dioxide storage

Mitigation of climate change will require a significant reduction in carbon dioxide (CO2) emissions to the atmosphere. Combustion of fossil fuels for electricity generation is a primary source of CO2 emissions. Reducing and eventually eliminating these emissions will require the transition to a low-carbon energy infrastructure, and this transition will likely take decades or centuries. To continue using fossil fuels at reduced CO2 emissions during this transitional period, carbon capture and storage (CCS) will be an essential bridging technology.

Cartoon of CO2 injection into a deep aquiferCarbon capture and storage involves capturing CO2 from the flue gas of power plants and injecting it deep underground into water-filled rocks for long-term storage. The CO2 is less dense than the groundwater, so one major concern is that the buoyant plume of injected CO2 will migrate far from the injection well and could leak toward the surface, potentially contaminating drinking water.

The main goal of our research on geological CO2 storage is to understand the mechanisms that trap the CO2 securely in the subsurface. These include residual trapping, where the large plume of CO2 is broken up into immobile blobs by capillary forces, and solubility trapping, where CO2 dissolves into the groundwater. We are currently studying the impact of these mechanisms on the lateral and vertical migration of CO2 plumes.

Hydraulic fracturing for recovery of shale gas

Recovery of natural gas from mudstone (shale) formations has triggered an energy revolution in the US, and shows similar potential in the UK and elsewhere. A key technology in extracting gas from these low-permeability rocks is hydraulic fracture. This involves injecting large quantities of fracturing fluid (water with chemical and granular additives) into the rock at high pressure to propagate cracks / fractures throughout the rock and thereby enhance its permeability to fluid flow and “release” the gas. Although this technology is promising, there is widespread public concern that hydraulic fracture could lead to the leakage of fracturing fluid and/or gas into freshwater aquifers, contaminating drinking water.

The main goal of our work on hydraulic fracture is to understand the coupling of rock deformation with the flow of water and gas during hydraulic fracturing and subsequent gas recovery. This is essential in order to assess leakage risks and to optimize gas extraction. Simple models are available for gas recovery over time that show promising agreement with recovery histories from real wells, but these neglect the details of the mechanics and of the gas-water displacement processes. As a result, they cannot predict, for example, the fate of the substantial fraction of fracturing fluid that is not recovered during the extraction stage.