Core Scale Experimental Study of Capillary Dominated Flow in Fractured Porous Media Using CT Imaging
Abstract/Contents
- Abstract
- When producing from naturally or hydraulically fractured petroleum reservoirs, it is important to understand the dominant mechanisms of production and accurately model flow performance both in the solid rock matrix and in the fracture network. Capillary imbibition of water into the matrix, during waterflooding or aquifer influx, provides a mechanism for expulsing oil out of the matrix and into the fractures. Because fluids flow preferentially in the fractures, but the great majority of petroleum is stored in the rock matrix, matrix-to-fracture fluid transfer resulting from capillary imbibition largely influences reservoir performance. Numerical flow simulations of fractured porous reservoirs typically utilize transfer functions incorporating shape factors to model the matrix-to-fracture fluid transfer. Historically, transfer function formulations have assumed pseudosteady state flow and a fracture network that is completely filled with fluid. This approach results in constant, time independent shape factors. Recently, authors have presented transfer functions without assuming pseudosteady state flow and have captured the time dependency of shape factors. It has been shown that time dependent shape factors are significant to accurate recovery prediction and to the design of efficient waterfloods. Prior research related to capillary dominated flow in fractured porous media is mostly limited to experiments with fractures that are external to the core, imbibition in one dimension, non-intersecting fractures, numerical studies that utilize such experimental results, or purely analytical methods. In this work, an 11.4 cm diameter, sleeved sandstone core with two internal and perpendicular artificial fractures is waterflooded to observe the physical processes of imbibition and fracture flow in multidimensions. Waterflood flow rate was varied. X-ray computerized tomography is employed to measure saturations and observe water front advancement in the core. Experiments are conducted using air-water phases. The robustness of matrix-to-fracture shape factor formulations developed by previous authors are tested. Specifically, it is found that the new experimental results for shape factor show good agreement with time dependent shape factor behavior published by previous authors. The previously published shape factor formulation is further validated in this work with more complex matrix-fracture geometry than was previously tested. Second, in accord with published theory for capillary continuity in strongly water wet porous media, no evidence of droplet bridging across fractures was observed in this experimental work. Third, fractures significantly influenced saturation versus position profiles. Where there were fractures parallel to the primary direction of flow, the saturation profiles were significantly more diffuse as compared to the saturation profiles where there were no fractures present. When there was a fracture perpendicular to the primary direction of flow, the saturation profile showed a marked dip. The saturation values were smaller just in front of the perpendicular fracture because water was supplied to fill the fracture, rather than first being imbibed into the matrix. Within the fracture, the saturation was high because the porosity and permeability of the fracture was greater than the porosity in the matrix. Behind the fracture, the imbibition rate was relatively slower before the fracture filled and subsequently faster after the fracture filled.
Description
| Type of resource | text |
|---|---|
| Date created | June 2004 |
Creators/Contributors
| Author | Chaobal, Aditya N. |
|---|---|
| Primary advisor | Kovscek, Anthony R. |
| Degree granting institution | Stanford University, Department of Petroleum Engineering |
Subjects
| Subject | School of Earth Energy & Environmental Sciences |
|---|---|
| Genre | Thesis |
Bibliographic information
Access conditions
- Use and reproduction
- User agrees that, where applicable, content will not be used to identify or to otherwise infringe the privacy or confidentiality rights of individuals. Content distributed via the Stanford Digital Repository may be subject to additional license and use restrictions applied by the depositor.
Preferred citation
- Preferred Citation
- Chaobal, Aditya N. (2004). Core Scale Experimental Study of Capillary Dominated Flow in Fractured Porous Media Using CT Imaging. Stanford Digital Repository. Available at: https://purl.stanford.edu/jp040pb4069
Collection
Master's Theses, Doerr School of Sustainability
View other items in this collection in SearchWorksContact information
- Contact
- brannerlibrary@stanford.edu
Also listed in
Loading usage metrics...