Models of flow and mixing of CO2 and brines in heterogeneous porous media

Lead Research Organisation: University of Cambridge
Department Name: Earth Sciences

Abstract

Sub-surface carbon storage, which involves separation of CO2 from power station fuels or waste gases and injection and storage of the CO2 underground, offers one of the more economical and practical methods for society to manage its transition to a low-carbon economy. A key aspect of sub-surface carbon storage is the need to ensure that the storage is safe and efficient and this requires the ability to model the fate of the CO2 over the ~ 10000 year storage period. Key mechanisms which will increase the security of CO2 storage are residual trapping, where some CO2 is retained in pore space by surface tension, and solubility trapping in which CO2 dissolves in formation brines. The rate at which both these mechanisms will operate will be strongly controlled by the small and medium scale (10 cm to 100's m) heterogeneities in permeability of the reservoirs.

The project will examine the impact of the characteristic heterogeneities in sedimentary units on the rates of residual and solubility trapping. The project will use a combination of approaches. Laboratory experiments and theoretical analysis for miscible currents with large viscosity differences may be used to understand the flow of brines and CO2 through heterogeneous media characteristic of reservoirs. The project may combine this with field studies of the permeability heterogeneities of sedimentary formations and use this information to predict the important structural heterogeneities of potential CO2 reservoirs.

The student will become familiar with the processes and requirements for geological carbon storage. They will join a group of more than 10 (faculty, post-docs and students) working on a whole range of problems related to CO2 storage. The student will be encouraged to interact with this group who are carrying out related research on a variety of issues in carbon storage including modelling of multi-phase flow, seismic imaging of reservoirs and studying the fluid-fluid and fluid-mineral reactions within reservoirs. While the modelling will be based on the field examples, the theoretical and experimental tools developed will be generic and applicable to a wide range of heterogeneous media.

Publications

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Studentship Projects

Project Reference Relationship Related To Start End Student Name
EP/P510440/1 01/10/2016 30/09/2021
1928880 Studentship EP/P510440/1 01/10/2017 30/09/2020 Kieran Andreas Gilmore
 
Description To limit global warming to well under 2?C, it is likely that large amounts of carbon dioxide (CO2) will need to be stored underground. A significant fraction of the total possible storage space for CO2 is in salt water reservoirs, kilometers beneath the surface. It is important that once the CO2 has been injected underground it is securely trapped, otherwise there is a risk that it could leak back to the surface. After the CO2 is injected into these reservoirs, it can dissolve in the surrounding water which permanently traps the CO2. This process is usually slow. However, geological formations may contain layers that allow the CO2 to flow more easily and this increases the contact area between the CO2 and water which means more CO2 can dissolve in the water. This study calculates how much of the injected CO2 dissolves in such a reservoir, and how far it travels in a given time. Using the Salt Creek Field CO2 injection site in Wyoming as an example, we find that up to 10% of the total injected CO2 can dissolve into the surrounding water by this process and become permanently trapped.
Exploitation Route In the coming decades, it is highly likely that large volumes of CO2 will be stored underground to help mitigate global warming. Being able to quantify how safely the CO2 is trapped once underground will allow stakeholders to assess how often it needs to be monitored, what volumes can be stored and what reservoirs are most suitable for storage. All of these factors affect the costs of storage, and have important consequences with assessing and minimizing risk.
Sectors Energy,Environment

 
Description I have presented findings of my research to non-academic audiences, educating them on the background sciences, associated technologies and need for carbon capture and storage in the energy transition.
First Year Of Impact 2018
Sector Energy,Environment
Impact Types Policy & public services