The impact of drainage displacement patterns and Haines jumps on CO2 storage efficiency

Ioannis Zacharoudiou,John Crawshaw,Edo S. Boek

doi:10.1038/s41598-018-33502-y

Ioannis Zacharoudiou, John Crawshaw + Show 1 more

Open Access

https://doi.org/10.1038/s41598-018-33502-y

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Abstract

Injection of CO2 deep underground into porous rocks, such as saline aquifers, appears to be a promising tool for reducing CO2 emissions and the consequent climate change. During this process CO2 displaces brine from individual pores and the sequence in which this happens determines the efficiency with which the rock is filled with CO2 at the large scale. At the pore scale, displacements are controlled by the balance of capillary, viscous and inertial forces. We simulate this process by a numerical technique, multi-GPU Lattice Boltzmann, using X-ray images of the rock pores. The simulations show the three types of fluid displacement patterns, at the larger scale, that have been previously observed in both experiments and simulations: viscous fingering, capillary fingering and stable displacement. Here we examine the impact of the patterns on storage efficiency and then focus on slow flows, where displacements at the pore scale typically happen by sudden jumps in the position of the interface between brine and CO2, Haines jumps. During these jumps, the fluid in surrounding pores can rearrange in a way that prevent later displacements in nearby pores, potentially reducing the efficiency with which the CO2 fills the total available volume in the rock.

Highlights

Multiphase flow is ubiquitous in nature, as well as a plethora of industrial processes
We directly solve the hydrodynamic equations of motion on a three dimensional geometry reconstructed from micro-CT images of Ketton limestone[30], see Fig. 1, using multi-Graphics Processing Units (GPUs) free energy lattice Boltzmann (LB) simulations[31,32,33]
Our results agree with the ones reported in the literature[3,6,7,12], i.e. the maximum achievable displacement efficiency decreases with decreasing Ca and as we move from stable displacement to capillary fingering and viscous fingering

Summary

Introduction

Multiphase flow is ubiquitous in nature, as well as a plethora of industrial processes. According to the pioneering work of Lenormand et al.[3] in micromodels, the competition of viscous and capillary forces leads to the basic drainage displacement patterns, namely i) viscous fingering, ii) capillary fingering and iii) stable displacement These patterns can be mapped on a phase diagram with axes the capillary number Ca and the viscosity ratio M of the fluids. Haines jumps are associated with both drainage and imbibition dynamics[21,27], as i) at the draining site the non-wetting fluid passes through a narrow throat displacing the wetting fluid in the wider pore body, while ii) imbibition takes place in surrounding throats with the wetting fluid displacing the injected non-wetting phase This leads to fluid rearrangement during the jumps, which supplies a significant fraction of the the necessary fluid volume for draining a pore body[19]. Understanding the displacement processes taking place at the pore-scale is essential in maximizing the displacement efficiency and it is of paramount importance as CO2 geological sequestration appears to be an important tool for combating global warming

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