Development of Unified Experimental and Theoretical Approach to Predict Reactive Transport in Subsurface Porous Media

Lead Research Organisation: Imperial College London
Department Name: Earth Science and Engineering

Abstract

This project aims to reduce the uncertainty and risk associated with key global challenges for the 21st century - securing sustainable access to water, energy and food. The underpinning understanding of natural systems to address this challenge is, in a large part, concerned with storage and extraction from porous rock: this includes safe storage of carbon dioxide to mitigate greenhouse gas emissions, efficient recovery from hydrocarbon reservoirs and groundwater management. Complex geological structures such as carbonate rock contain at least half of the world's conventional oil reserves, and have a significant storage capacity for CO2. The UK strategic energy plans include taking a leading role in enhanced oil recovery and carbon storage in carbonates. The most important UK aquifer is a remarkably pure limestone (calcium carbonate) providing more than half the water supply for drinking and industrial purposes.

Transport - a quantitative description of how fluids move - through complex geological structures is absolutely crucial to a rational understanding of these processes in natural systems and yet it is still not fully understood, especially when coupled with chemical reactions. While it is well known that geological systems host physical and chemical processes that span a huge range of spatial and temporal scales, research - to date - has largely focused on understanding the structure of the porous medium, and the macroscopic description of the interplay between flow field, transport and reaction. However the interplay between pore structure, flow field, transport and chemical reaction is unknown.

Chemical reaction introduces the next level of complexity that is particularly challenging to quantitatively describe across a hierarchy of length scales. We will address this problem for reactive transport in porous media by combining new experimental Nuclear Magnetic Resonance methods with a novel multiple scale modelling method. This unified approach will have a key advantage in retaining detailed information on localised reactive transport parameters in terms of spatial and temporal distribution functions, rather than only having spatially and/or temporally averaged macroscopic parameters.

We will undertake a systematic program of research integrating pore-to-core scale measurements and modelling of reactive transport processes into a unified experimental and theoretical framework aimed at answering the following key questions:

* How can we establish a methodology to measure and predict the reactive transport rates within aquifers and reservoirs?

* What are relationships between structural, flow, transport and reaction properties governing reactive transport in natural rock?

* What are key uncertainties in predicting reactive transport in natural rock in terms of structural, flow, transport and reaction properties?

* What impact the transport and reaction physics at the pore scale have on reactive transport at the large scale?

Planned Impact

Key deliverables from this project are:

(1) Image library of carbonate rock
(2) Library of reactive flow propagators NMR measurements
(3) Experimental validation at the pore- and core-scale by pore-scale modelling
(4) Model predictions for reactive transport from pore to field scale with a new simulator
(5) A new methodology for making predictions of reactive transport based on the unified experimental and theoretical approach.

These deliverables will help the beneficiaries describe and upscale the key processes responsible for quantitative description of how fluids move and react in porous media including the subsurface.

Who will benefit and how:

(1) The UK Research Community
The research will generate new experimental results and modelling insights that are of generic value for the UK research effort in a range of disciplines including carbon storage, enhanced oil recovery and subsurface contaminant transport. Examples are: Localised chemically selective NMR propagator measurements and model predictions for reactive transport propagators in carbonate cores; a methodology to measure reactive flow propagators in natural rock; pore-to-field scale simulator for reactive transport that incorporates NMR flow propagator data.

(2) Global Academic Community
The research outputs and methodology developed in this work will of global relevance and will provide valuable data and models for use in reactive transport in porous media research. Examples are as for UK Research Community. Research findings will be disseminated in leading scientific journals and at top national and international conferences.

(3) The Enhanced Oil Recovery, CO2 Storage and Waste Disposal and Remediation Industry

The project results will quantify the uncertainties and reduce the risk involved in CO2 sequestration and enhanced oil recovery. The UK-based CO2 storage and enhanced oil recovery industry is well placed to benefit directly from the project outcomes. The beneficiaries are mainly oil and gas companies, who are able to develop large-scale enhanced oil recovery projects, the large CCS storage projects, and the power companies who must work with them to establish a full CCS chain.

(4) Small and Medium Enterprises (SMEs) and Oil Companies (such as Total)

Digital Rock Analysis that will be used in this project has made considerable advances over the recent years. This facilitated the creation of a number of SMEs that are involved with the oil and gas majors as service companies providing special core analysis. They will benefit from the new methodology to be developed in this project.

(5) UK Economy

The scientific development under this project will help improve nationally important technologies - carbon storage, enhanced oil recovery and waste disposal and remediation. The project will benefit the UK economy by creating exporting opportunities in the above technologies.

(6) The Public
The new scientific understanding of reactive transport in porous media in the proposed research will help us to better understand the physics of carbon storage, enhanced oil recovery and waste disposal and remediation, thus providing reassurances that these technologies are efficient, safe and cost-effective. This will contribute to public acceptance.

Publications


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Honari A (2016) The impact of residual water on CH4-CO2 dispersion in consolidated rock cores in International Journal of Greenhouse Gas Control
Pereira Nunes J (2016) Pore-scale simulation of carbonate dissolution in micro-CT images in Journal of Geophysical Research: Solid Earth
Pereira Nunes J (2016) Pore-space structure and average dissolution rates: A simulation study in Water Resources Research
 
Description The pore-scale modelling work on flow and reactive transport in carbonate rock has delivered several new outcomes:

- The impact of inertial flow effects have been quantified for a wide range of flow conditions in subsurface rock of different pore space heterogeneity. This study can be used to assess the impact of non-Darcy flow effects in subsurface near the injection wells.

- Fluid/fluid reactive transport modelling on images of pore space has demonstrated the key role that incomplete fluid mixing has in predictions of dynamic effective reaction rates in porous media. This work has implications in mixing and spreading behaviour during contaminant transport and tracer studies in subsurface.

- Fluid/solid reactive transport modelling work have demonstrated capability in validating dynamic X-ray tomography experiment on CO2 storage in carbonate rock as well as the predictive capability for modelling different initial pore/solid structures and transport conditions. Effective reaction rates are shown to be at least an order of magnitude lower than the rates measured in the laboratory under perfect mixing conditions - this is a result of mass transfer limitations introduced by complex geometry of subsurface rock.

- New multi-scale characterisation of transport heterogeneity has been evaluated by analysing NMR reactive transpor texperiments. Validation of the model against NMR experiments has been successful.
Exploitation Route Further experiments can be performed to test model predictions for inertial flow effects, fluid/fluid effective reaction rates and fluid/solid effective reaction rates.
Sectors Agriculture, Food and Drink,Energy,Environment,Manufacturing, including Industrial Biotechology
 
Description Collaboration with University of Western Australia 
Organisation University of Western Australia
Country Australia, Commonwealth of 
Sector Academic/University 
PI Contribution This Centre for Energy, School of Mechanical and Chemical Engineering M050, University of Western Australia
Collaborator Contribution Reinjection of CO2 into producing natural gas reservoirs is considered as a promising technology to improve gas recovery, mitigate atmospheric emissions and control climate change. This collaboration have undertaken experimental studies on CO2/CH4 dispersion in carbonate and sandstone rock (Honari et al., 2015) and demonstrated the impact of pore-structure heterogeneity on the mixing process. A new publication (Honari et al., 2016) expanded this studies to report spercritical CH4 dispersion in two-phase flow in sandstones and carbonates.
Impact This collaboration work found out a good agreement of the experimental data on dispersion in carbonates and sandstones (Honari et al., 2015; 2016) with previously published model predictions (Bijeljic and Blunt,2006; Bijeljic et al., 2011) based on pore-scale simulations.
Start Year 2014
 
Description MRRC centre at Cambridge University 
Organisation University of Cambridge
Country United Kingdom of Great Britain & Northern Ireland (UK) 
Sector Academic/University 
PI Contribution Development of models for reactive transport in porous media for comparison with NMR technique results
Collaborator Contribution Development of NMR techniques to experimentally study reactive flows in porous media
Impact None for now as project has started in April 2014
Start Year 2014