Wang, Q, Yang, S, Glover, PWJ orcid.org/0000-0003-1715-5474 et al. (3 more authors) (2020) Effect of Pore-Throat Microstructures on Formation Damage during Miscible CO2 Flooding of Tight Sandstone Reservoirs. Energy & Fuels, 34 (4). pp. 4338-4352. ISSN 0887-0624
Abstract
Pore and throat blockage and wettability alteration caused by asphaltene deposition are serious problems during the injection of CO2 into subsurface reservoirs for enhanced oil recovery (EOR). During miscible CO2 flooding, the efficacy and distribution of fluid flow in sandstone reservoirs are controlled by the pore-throat microstructure of the rock. Furthermore, CO2 injection promotes asphaltene precipitation on pore surfaces and in the pore throats, decreasing the permeability and altering reservoir wettability. In this work, miscible CO2 flooding experiments under reservoir conditions (up to 70 ± 0.1 °C, 18 MPa) were carried out on four samples with very similar permeabilities but significantly different pore size distributions and pore-throat structures to study the effects of the pore-throat microstructure on formation damage. The features of the pore-throat structure were evaluated by fractal theory, based on constant-rate mercury intrusion (CRMI) tests. Reservoir rocks with smaller pore-throat sizes and more heterogeneous and poorer pore-throat microstructures were found to be more sensitive to asphaltene precipitation, with corresponding 14–22% lower oil recovery factors (RFs) and 4–7% greater decreases in permeability compared to more homogeneous rocks and rocks with larger pore throats. However, the water-wettability index of cores with larger and more connected pore-throat microstructures was found to drop by an extra 15–25% compared to the water-wettability decrease found for heterogeneous cores. We attribute these observations to an increase in asphaltene precipitation caused by the larger sweep volume of injected CO2, which occurs in rocks with larger and more homogeneous pore throats. In addition, we observed that rocks with more homogeneous pore-throat microstructures also exhibit homogeneity in the consequent distribution of formation damage.
Metadata
Item Type: | Article |
---|---|
Authors/Creators: |
|
Copyright, Publisher and Additional Information: | © 2020 American Chemical Society. This is an author produced version of an article published in Energy & Fuels. Uploaded in accordance with the publisher's self-archiving policy. |
Keywords: | Hydrocarbons; Lipids; Wetting; Aromatic compounds; Permeability |
Dates: |
|
Institution: | The University of Leeds |
Academic Units: | The University of Leeds > Faculty of Environment (Leeds) > School of Earth and Environment (Leeds) > Institute for Applied Geosciences (IAG) (Leeds) |
Depositing User: | Symplectic Publications |
Date Deposited: | 03 Mar 2020 15:51 |
Last Modified: | 17 Mar 2021 01:38 |
Status: | Published |
Publisher: | American Chemical Society |
Identification Number: | 10.1021/acs.energyfuels.0c00158 |
Open Archives Initiative ID (OAI ID): | oai:eprints.whiterose.ac.uk:157894 |