H029-02
The Development of Intermittent Fluid Flow Pathways and their Impact on Relative Permeability Imaged with 1s Temporal Resolution
The Development of Intermittent Fluid Flow Pathways and their Impact on Relative Permeability Imaged with 1s Temporal Resolution
Tuesday, 8 December 2020: 04:04
Virtual
Abstract:
Intermittent flow fluid pathways, where the flow pathways are periodically disconnecting and reconnected, are expected to occur in the subsurface for scenarios such as CO2 storage and natural gas production (Panel 1) [1]. This flow phenomenon has been observed in rocks using X-ray tomography, but limitations with resolution has always led to the blurring of fluid interfaces in the images [1-4]. This has prevented the understanding of the development and stability of intermittent pathways, as the movements have been faster than the temporal resolution of the imaging. Thus, it has been poorly understood the impact of intermittent pathways on macroscale flow properties such as the relative permeability, and its impact on flow has been historically ignored in reservoir modelling.
With state-of-the-art synchrotron imaging, we imaged fluid flow every second; this improves the temporal resolution compared to previously published work by almost two orders of magnitude. We were able to capture the movement of fluid interfaces during steady-state flow of nitrogen and brine through a carbonate rock. The distribution of gas in the pore space with time is explored for different capillary numbers (Panel 2).
For the lowest capillary number experiment, the gas flows through one pore at one point in the sample (Panel 2). When the flow rate is increased (but the ratio of brine flow to nitrogen flow is the same), the saturation is similar, but the gas flow pathways have rearranged considerably. The Reynolds number for the same slice in the pore space is considerably lower, even though flow is faster (Panel 2). More intermittent pathways were observed at higher capillary numbers suggesting they are preferred over turbulent flow. We observe that the gas saturation scales with relative permeability, but to model our relative permeability values using the Brooks-Corey model requires different values of the “pore size distribution index” even though the rock sample was the same (Panel 3). This is because the dependence of pathways on the pore geometry decreases as the capillary number increases.
With state-of-the-art synchrotron imaging, we imaged fluid flow every second; this improves the temporal resolution compared to previously published work by almost two orders of magnitude. We were able to capture the movement of fluid interfaces during steady-state flow of nitrogen and brine through a carbonate rock. The distribution of gas in the pore space with time is explored for different capillary numbers (Panel 2).
For the lowest capillary number experiment, the gas flows through one pore at one point in the sample (Panel 2). When the flow rate is increased (but the ratio of brine flow to nitrogen flow is the same), the saturation is similar, but the gas flow pathways have rearranged considerably. The Reynolds number for the same slice in the pore space is considerably lower, even though flow is faster (Panel 2). More intermittent pathways were observed at higher capillary numbers suggesting they are preferred over turbulent flow. We observe that the gas saturation scales with relative permeability, but to model our relative permeability values using the Brooks-Corey model requires different values of the “pore size distribution index” even though the rock sample was the same (Panel 3). This is because the dependence of pathways on the pore geometry decreases as the capillary number increases.
[1] Spurin et al. 2019b. 10.1103/PhysRevE.100.043115
[2] Spurin et al. 2019a. 10.1103/PhysRevE.100.043103
[3] Reynolds et al. 2017. 10.1073/pnas.1702834114
[4] Gao et al. 2017. 10.1002/2017WR021736