<abstract xmlns="http://www.w3.org/1999/xhtml">

CO2 injection is a well-known Enhanced Oil Recovery (EOR) technique that has been used for years to improve oil extraction from carbonate rock and other oil reservoirs. Optimal functioning of CO2 injection requires a thorough understanding of how this method affects the petrophysical properties of the rocks. We evaluated pore-scale changes in these properties, notably porosity and absolute permeability, following injection of CO2-saturated water in two coquina outcrop samples from the Morro do Chaves Formation in Brazil. The coquinas are close analogues of Pre-salt oil reservoirs off the coast of southern Brazil. The effects of carbonated water injection were evaluated using a series of experimental and numerical steps before and after coreflooding: cleaning, basic petrophysics, microtomography (microCT) imaging, nuclear magnetic resonance (NMR) analyses, and pore network modeling (PNM). Our study was motivated by an earlier experiment which did not show the development of a wormhole in the center of the sample, with a concomitant increase in permeability of the coquina as often noted in the literature. We instead observed a substantial decrease in the absolute permeability (between 71 and 77%), but with little effect on the porosity and no wormhole formation. While all tests were carried out on both samples, here we present a comprehensive analysis for one of the samples to illustrate changes at the pore network level. Different techniques were used for the pore-scale analyses, including pore network modeling using PoreStudio, and software developed by the authors to enable a statistical analysis of the pore network. Results provided much insight in how injected carbonated water affects the pore network of carbonate rocks.
</abstract>

CO2 injection is a well-known Enhanced Oil Recovery (EOR) technique that has been used for years to improve oil extraction from carbonate rock and other oil reservoirs. Optimal functioning of CO2 injection requires a thorough understanding of how this method affects the petrophysical properties of the rocks. We evaluated pore-scale changes in these properties, notably porosity and absolute permeability, following injection of CO2-saturated water in two coquina outcrop samples from the Morro do Chaves Formation in Brazil. The coquinas are close analogues of Pre-salt oil reservoirs off the coast of southern Brazil. The effects of carbonated water injection were evaluated using a series of experimental and numerical steps before and after coreflooding: cleaning, basic petrophysics, microtomography (microCT) imaging, nuclear magnetic resonance (NMR) analyses, and pore network modeling (PNM). Our study was motivated by an earlier experiment which did not show the development of a wormhole in the center of the sample, with a concomitant increase in permeability of the coquina as often noted in the literature. We instead observed a substantial decrease in the absolute permeability (between 71 and 77%), but with little effect on the porosity and no wormhole formation. While all tests were carried out on both samples, here we present a comprehensive analysis for one of the samples to illustrate changes at the pore network level. Different techniques were used for the pore-scale analyses, including pore network modeling using PoreStudio, and software developed by the authors to enable a statistical analysis of the pore network. Results provided much insight in how injected carbonated water affects the pore network of carbonate rocks.

Effects of carbonated water injection on the pore system of a carbonate rock (coquina)

Journal of Hydrology and Hydromechanics

This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License.

CO2 injection is a well-known Enhanced Oil Recovery (EOR) technique that has been used for years to improve oil extraction from carbonate rock and other oil...

Effects of carbonated water injection on the pore system of a carbonate rock (coquina)

Published Online: May 19, 2022

Page range: 257 - 268

Received: Oct 01, 2021

Accepted: Dec 27, 2021

DOI: https://doi.org/10.2478/johh-2022-0001

Keywords
Carbonate rocks, Coreflooding, Pore Size Distribution, Pore Network Analysis, PoreStudio

© 2022 Thaís M. Silveira et al., published by Sciendo

This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License.

Effects of carbonated water injection on the pore system of a carbonate rock (coquina)

Published Online: May 19, 2022

Page range: 257 - 268

Received: Oct 01, 2021

Accepted: Dec 27, 2021

DOI: https://doi.org/10.2478/johh-2022-0001

KeywordsCarbonate rocks, Coreflooding, Pore Size Distribution, Pore Network Analysis, PoreStudio

© 2022 Thaís M. Silveira et al., published by Sciendo

This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License.

Keywords
Carbonate rocks, Coreflooding, Pore Size Distribution, Pore Network Analysis, PoreStudio