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Pore Structure Changes Occur During CO(2) Injection into Carbonate Reservoirs
Observations and modeling studies have shown that during CO(2) injection into underground carbonate reservoirs, the dissolution of CO(2) into formation water forms acidic brine, leading to fluid-rock interactions that can significantly impact the hydraulic properties of the host formation. However,...
Autores principales: | , , , , , , |
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Formato: | Online Artículo Texto |
Lenguaje: | English |
Publicado: |
Nature Publishing Group UK
2020
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Materias: | |
Acceso en línea: | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7046766/ https://www.ncbi.nlm.nih.gov/pubmed/32107400 http://dx.doi.org/10.1038/s41598-020-60247-4 |
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author | Seyyedi, Mojtaba Mahmud, Hisham Khaled Ben Verrall, Michael Giwelli, Ausama Esteban, Lionel Ghasemiziarani, Mohsen Clennell, Ben |
author_facet | Seyyedi, Mojtaba Mahmud, Hisham Khaled Ben Verrall, Michael Giwelli, Ausama Esteban, Lionel Ghasemiziarani, Mohsen Clennell, Ben |
author_sort | Seyyedi, Mojtaba |
collection | PubMed |
description | Observations and modeling studies have shown that during CO(2) injection into underground carbonate reservoirs, the dissolution of CO(2) into formation water forms acidic brine, leading to fluid-rock interactions that can significantly impact the hydraulic properties of the host formation. However, the impacts of these interactions on the pore structure and macroscopic flow properties of host rock are poorly characterized both for the near-wellbore region and deeper into the reservoir. Little attention has been given to the influence of pressure drop from the near-wellbore region to reservoir body on disturbing the ionic equilibrium in the CO(2)-saturated brine and consequent mineral precipitation. In this paper, we present the results of a novel experimental procedure designed to address these issues in carbonate reservoirs. We injected CO(2)-saturated brine into a composite core made of two matching grainstone carbonate core plugs with a tight disk placed between them to create a pressure profile of around 250 psi resembling that prevailing in reservoirs during CO(2) injection. We investigated the impacts of fluid-rock interactions at pore and continuum scale using medical X-ray CT, nuclear magnetic resonance, and scanning electron microscopy. We found that strong calcite dissolution occurs near to the injection point, which leads to an increase in primary intergranular porosity and permeability of the near injection region, and ultimately to wormhole formation. The strong heterogeneous dissolution of calcite grains leads to the formation of intra-granular micro-pores. At later stages of the dissolution, the internal regions of ooids become accessible to the carbonated brine, leading to the formation of moldic porosity. At distances far from the injection point, we observed minimal or no change in pore structure, pore roughness, pore populations, and rock hydraulic properties. The pressure drop of 250 psi slightly disturbed the chemical equilibrium of the system, which led to minor precipitation of sub-micron sized calcite crystals but due to the large pore throats of the rock, these deposits had no measurable impact on rock permeability. The trial illustrates that the new procedure is valuable for investigating fluid-rock interactions by reproducing the geochemical consequences of relatively steep pore pressure gradients during CO(2) injection. |
format | Online Article Text |
id | pubmed-7046766 |
institution | National Center for Biotechnology Information |
language | English |
publishDate | 2020 |
publisher | Nature Publishing Group UK |
record_format | MEDLINE/PubMed |
spelling | pubmed-70467662020-03-05 Pore Structure Changes Occur During CO(2) Injection into Carbonate Reservoirs Seyyedi, Mojtaba Mahmud, Hisham Khaled Ben Verrall, Michael Giwelli, Ausama Esteban, Lionel Ghasemiziarani, Mohsen Clennell, Ben Sci Rep Article Observations and modeling studies have shown that during CO(2) injection into underground carbonate reservoirs, the dissolution of CO(2) into formation water forms acidic brine, leading to fluid-rock interactions that can significantly impact the hydraulic properties of the host formation. However, the impacts of these interactions on the pore structure and macroscopic flow properties of host rock are poorly characterized both for the near-wellbore region and deeper into the reservoir. Little attention has been given to the influence of pressure drop from the near-wellbore region to reservoir body on disturbing the ionic equilibrium in the CO(2)-saturated brine and consequent mineral precipitation. In this paper, we present the results of a novel experimental procedure designed to address these issues in carbonate reservoirs. We injected CO(2)-saturated brine into a composite core made of two matching grainstone carbonate core plugs with a tight disk placed between them to create a pressure profile of around 250 psi resembling that prevailing in reservoirs during CO(2) injection. We investigated the impacts of fluid-rock interactions at pore and continuum scale using medical X-ray CT, nuclear magnetic resonance, and scanning electron microscopy. We found that strong calcite dissolution occurs near to the injection point, which leads to an increase in primary intergranular porosity and permeability of the near injection region, and ultimately to wormhole formation. The strong heterogeneous dissolution of calcite grains leads to the formation of intra-granular micro-pores. At later stages of the dissolution, the internal regions of ooids become accessible to the carbonated brine, leading to the formation of moldic porosity. At distances far from the injection point, we observed minimal or no change in pore structure, pore roughness, pore populations, and rock hydraulic properties. The pressure drop of 250 psi slightly disturbed the chemical equilibrium of the system, which led to minor precipitation of sub-micron sized calcite crystals but due to the large pore throats of the rock, these deposits had no measurable impact on rock permeability. The trial illustrates that the new procedure is valuable for investigating fluid-rock interactions by reproducing the geochemical consequences of relatively steep pore pressure gradients during CO(2) injection. Nature Publishing Group UK 2020-02-27 /pmc/articles/PMC7046766/ /pubmed/32107400 http://dx.doi.org/10.1038/s41598-020-60247-4 Text en © Crown 2020 https://creativecommons.org/licenses/by/4.0/Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The images or other third party material in this article are included in the article’s Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/ (https://creativecommons.org/licenses/by/4.0/) . |
spellingShingle | Article Seyyedi, Mojtaba Mahmud, Hisham Khaled Ben Verrall, Michael Giwelli, Ausama Esteban, Lionel Ghasemiziarani, Mohsen Clennell, Ben Pore Structure Changes Occur During CO(2) Injection into Carbonate Reservoirs |
title | Pore Structure Changes Occur During CO(2) Injection into Carbonate Reservoirs |
title_full | Pore Structure Changes Occur During CO(2) Injection into Carbonate Reservoirs |
title_fullStr | Pore Structure Changes Occur During CO(2) Injection into Carbonate Reservoirs |
title_full_unstemmed | Pore Structure Changes Occur During CO(2) Injection into Carbonate Reservoirs |
title_short | Pore Structure Changes Occur During CO(2) Injection into Carbonate Reservoirs |
title_sort | pore structure changes occur during co(2) injection into carbonate reservoirs |
topic | Article |
url | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7046766/ https://www.ncbi.nlm.nih.gov/pubmed/32107400 http://dx.doi.org/10.1038/s41598-020-60247-4 |
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