Core-Scale Experiments on Fracture-Matrix Interactions Between CO2 and Water in Fractured Porous Media
Abstract
The assessment of CO2 storage capacity in fractured reservoirs requires a better understanding of the fundamental processes of fracture-matrix interactions. These processes can be complicated by capillary continuity between neighboring matrix blocks. In this study, we investigated three-dimensional CO2-water displacement in four columns, each of which was stacked by a ceramic block at the bottom and a rock-core matrix block with a range of capillary/flow properties. While the capillary ceramic blocks were used to increase the applicable range of capillary pressure (Pc), the four rock-core samples showed contrasts between weak and strong anisotropy, low and high permeability, and homogeneity and heterogeneity. In the experimental setup, the open space between the experimental vessel and the core sample represented fractures surrounding the cylindrical matrix block, and a piece of filter paper between the core sample and the downstream ceramic block represented a horizontal fracture to simulate the capillary continuity between the two blocks. Twelve CO2 drainage experiments were conducted with controlled Pc varying from 14 to 200 kPa. In each experiment, the matrix block initially saturated with water was drained under a constant Pc applied to the surrounding fractures under ambient temperature. The dynamic invasion/drainage process in the core matrix was monitored by frequent X-ray computed tomography (CT) scans and the CT images were used to show the distribution of CO2 saturation. Results show that the steady-state, core-scale storage efficiency in the matrix block varies from 0.10 to 0.60 and is considerably affected by the water saturation and capillary continuity of the horizontal fracture. The capillary continuity is enhanced by the non-uniform water distribution in the fracture and a countercurrent flow of CO2 and water near the fracture-matrix interface. When a high capillary continuity in the fracture is maintained, the storage efficiency (as well as CO2 invasion and water drainage) is also affected by matrix anisotropy and heterogeneity. The results from this study can help better understand fracture-matrix interactions and storage efficiency in fractured reservoirs.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFM.H51I1592C
- Keywords:
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- 1832 Groundwater transport;
- HYDROLOGY;
- 1859 Rocks: physical properties;
- HYDROLOGY;
- 1878 Water/energy interactions;
- HYDROLOGY;
- 1895 Instruments and techniques: monitoring;
- HYDROLOGY