Abstract
Structural trapping is known to be the primary storage mechanism in geological carbon sequestration (GCS), where the injected CO2 rises upwards due to buoyancy forces and becomes trapped under an ultra-low permeability layer. Although it is relatively common in GCS studies to assume a planar caprock for the synthesised models, in a real scenario this is not always the case as the caprock might exhibit some small- or large-scale topography changes. Moreover, little is known about the impact of the caprock morphology on the CO2 plume migration and the storage capacity. In this work, we performed a preliminary study of the effects of boundary conditions on the CO2 plume migration and dissolution. This was performed because most of the case study models which are employed for GCS studies are part of larger reservoirs. The obtained results were used in the simulation models of the second part of the work, to model an infinite-acting reservoir appropriately. Three different volume modifier values of 105, 107 and 109 were considered on either one side or both sides of the reservoir for both horizontal and tilted caprock models. The CO2 dissolution in the tilted models was seen to be higher once the multiplier was on the opposite side of the slope. Horizontal models closed on one side (closed faults, salt walls, etc.) were also found to exhibit more significant dissolution than models which were open from both sides. We subsequently investigated the impact of caprock morphology on the CO2 plume advancement and its structural and dissolution trapping mechanisms by performing numerical simulations on nine synthetic models. The dissolution and migration distance are seen to be at a maximum for tilted reservoirs, where the CO2 has more space to migrate upwards and to interact with more formation water. The lowest dissolution occurred where the significant portion of the injected CO2 was trapped in a sand ridge or an anticline. Moreover, the possibility and also the amount of structural trapping was evaluated using an analytical method, and the results showed a fair match with the ones from the numerical simulation. We believe that this methodology could be applied for site screening prior to performing numerical simulations.
| Original language | English |
|---|---|
| Pages (from-to) | 183-205 |
| Number of pages | 23 |
| Journal | Greenhouse Gases: Science and Technology |
| Volume | 11 |
| Issue number | 1 |
| Early online date | 21 Dec 2020 |
| DOIs | |
| Publication status | Published - Feb 2021 |
Bibliographical note
Funding Information:Geological carbon sequestration can play a crucial role to achieve the 1.5 degrees°C target set by the Paris agreement. The rise in atmospheric concentrations of the CO and their now accepted direct link to global warming has prompted efforts to reduce their anthropogenic emissions, mainly from the burning of fossil fuels. An attractive mitigation option under consideration globally is the capture of CO from stationary sources, such as fossil fuel power plants, and its subsequent injection into deep, stable geologic formations, where its safe storage could be guaranteed for hundreds to thousands of years. Geological storage of carbon was first proposed in the late 1970's and the first research in this area started in the 1990's. Thanks to recent technological advancements in model development and computer power and speed, it is now possible to better predict the behaviour of the injected CO into these proposed underground storage sites. According to the Global Carbon Capture and Storage (CCS) roadmap, the contribution of CCS towards emission reduction by 2050 is expected to be 17%. Potential geologic storage reservoirs include depleted or depleting oil and gas reservoirs, coal beds and saline formations. There is a confidence in the feasibility of GCS worldwide, and this is supported by many large‐scale CCS projects, such as the Sleipner project in Norway, the Illinois Basin Decatur Project in the US and the QUEST project in Canada. Over the last decade, CO has also been used in more than 70 enhanced oil recovery (EOR) projects around the world. Some of the largest CO‐EOR projects are the Cranfield oil and gas field, Weyburn Field in Canada, Changqing Oil Field in China, Santos Basin in Brazil, and the Alberta Carbon Trunk Line project in Canada. This concept demonstration has been supported by a significant number of publications on different aspects of CCS in the last few decades, which shows the growing importance of the topic. Several studies have been undertaken globally on the feasibility of the CO storage in geological structures. The Sleipner gas field in the Norwegian North Sea is the first long‐running storage project in a saline formation, where the CO is captured from the produced natural gas through a chemical solvent‐based process and is then injected into the Utsira formation. The injection rate is approximately one million tonnes per year, and the reservoir had stored almost 17.8 Mt of CO by 1 January 2019. 1 2 2 2,3 4 5 2 5 6 7,8 9 10,11 12 13 2 14 2 15–18 19,20 21 22 23 2 24–31 2 32 33,34 2 35,36
Funding Information:
The authors would like to thank the Centre for Fluid and Complex Systems at Coventry University for providing financial support for this project. The authors also wish to thank Schlumberger for the use of the ECLIPSE and Petrel software, MathWorks for the use of Matlab and also Amarile for the use of Re‐Studio. Special thanks also to Dr Phil Costen for reviewing the paper and sharing his constructive comments with us.
Publisher Copyright:
© 2020 Society of Chemical Industry and John Wiley & Sons, Ltd.
Keywords
- analytical calculation
- caprock morphology
- carbon sequestration
- numerical simulation
- reservoir boundary
- saline aquifer
ASJC Scopus subject areas
- Environmental Engineering
- Environmental Chemistry