Qatar CCS Multi-Scale Imaging Laboratory
Dedicated to the imaging of flow in porous media at different length scales using X-ray Computer-aided Tomograpghy (CT), this laboratory is complemented by multi-scale simulation using direct and network modelling.
State-of-the-art imaging equipment is employed to study the fundamentals of CO2 storage in carbonates, including a Medical CT with 0.25mm resolution (capable of horizontal and vertical scanning), a micro-CT scanner (1 μm), a Confocal Laser Scanning Microscope (< 1 μm) and access to a Synchrotronic source (Diamond facility) allowing dynamic observations, Scanning Electron Microscopes and Positron Emission Tomography CT.
Carbon dioxide injection and trapping in carbonate reservoirs is governed by physical and chemical processes that take place at scales ranging from micron-sized pores to kilometre-length reservoirs. This advanced facility allows us to study these processes by recreating the extremely hot and pressurised conditions that exist in subsurface reservoirs, imaging flow and reaction in individual pores all the way up to metre-length rock samples.
The laboratory includes a bespoke petrographic X-ray CT that can record images in either horizontal or vertical orientations, and high pressure apparatus that allow for the controlled flow of CO2 and brines at extreme temperatures and pressures with or without chemical reaction.
We use a micro-CT specially adapted to recreate reservoir conditions, using flow experiments to visualise the arrangement of fluids and pore scale imaging of rock structures with a resolution of around 1 micron. We aim to focus on the impact of pore-scale processes and controls for large scale phenomena such as capillary trapping, changes in wettability and reactive transport.
These images go hand-in-hand with our pore-scale modelling research that can utilise approaches from a wide spectrum of techniques depending on the research hypothesis, and will ensure Imperial will be known globally as the home of the Digital Rocks revolution.
This laboratory, unique in the world today, is allowing us to address the major scientific and engineering challenges in multi-phase flow physics and reactive transport for the safe and permanent storage of carbon dioxide.
- We have now developed advanced characterisation techniques to analyse the multiphase flow properties for the CO2-brine-sandstone rock system across a wide range of reservoir conditions.
- Capillary pressure, relative permeability and residual trapping have all been characterised across a wide range of reservoir conditions of pressure, temperature and brine salinity, and all have been found to be invariant with respect to these conditions where rock heterogeneity does not prevail in the system
- The wetting properties of the CO2-brine-rock system do not change sufficiently to affect multiphase flow (capillarity, permeability and trapping) across a wide range of reservoir conditions. This is consistent with the vast body of multiphase flow literature for hydrocarbon systems but in contradiction to recent observations of wetting properties made on crystal surfaces with sessile drops for the CO2-brine-rock system.
- We have confirmed that the extent of residual trapping will be significant, with up to 30% of the pore space containing residually trapped CO2, leading to greatly enhanced secure containment predictions.
- We have characterised the distribution of reactive mineral surfaces in three dimensions, leading to a much greater understanding of potential reaction dynamics.
We have developed a new technique to observe the transport of chemicals, and particularly their dispersion or spreading, as they move through permeable rocks using 3D imagery generated from X-ray tomography.
Looking forward: areas under investigation
- Provision of reliable scCO2/brine relative permeabilities
- Study of coupled flow, phase exchange and reaction
- Pore imaging/network extraction for digital rock analysis
- Pore-to-core analysis for improved storage design
- Assessment of PET-CT as a tool for special core analysis
- Providing benchmark results for predictive modelling
- Providing input into field-scale simulation
We now turn our focus to the key questions concerning carbonate rocks: Rock mineralogy, heterogeneity, wetting properties and reactivity.
- What are the impacts of natural rock heterogeneity on multiphase flow and trapping? How do we characterise this and incorporate that description into reservoir models?
- What are the trapping properties of mixed wet systems? Particularly what will trapping look like in the context of mature oil fields where CO2 storage is being combined with enhanced oil recovery?
- How do chemical reacting and fluid flow impact each other? What are the feedbacks between chemical reaction and multiphase flow, how can we characterise those and how can they be modelled?
- How do fractures influence fluid flow and reactivity?