The Effects of Horizontal Well Placement and Gravity on Sweep Efficiency
Abstract/Contents
- Abstract
- This report evaluates sweep efficiencies of numerous well configurations in gas injection processes. For each configuration, comparisons are made at different viscous to gravity ratios (Rv/g) in order to present the effects of gravity on sweep efficiency.The report first evaluates well configurations in homogeneous reservoirs. Although the focus is on horizontal well applications, some configurations with vertical wells are also presented. In total, seven well configurations are considered in a homogeneous reservoir. These configurations are: 1) fully penetrated vertical five spot, 2) infinite length horizontal wells, 3) partially penetrated vertical five spot, 4) staggered finite length horizontal wells, 5) adjacent finite length horizontal wells, 6) combination vertical injector - horizontal producer, and 7) combination horizontal injector - vertical producer. The first and second configurations are studied in more depth than the other five configurations. The infinite length horizontal wells deliver the highest recovery of the seven configurations in the homogeneous reservoir. However, horizontal well configurations are sensitive to viscous to gravity ratio. Horizontal wells deliver their best recovery at an Rv/g of 1, where lateral and vertical travel times are equal. However, their recovery is very poor in viscous dominated flows (Rv/g's greater than 1).Conversely, the fully penetrated vertical five spot is less sensitive to viscous to gravity ratio in a homogeneous reservoir. The fully penetrated vertical wells do not display an optimum; recovery simply improves as Rv/g increases. The vertical five spot demonstrates a transition region in the form of a 'knee' between Rv/g's of 1 and 10, where recovery rapidly improves with increasing Rv/g. At Rv/g's outside the transition region, recovery is relatively insensitive to R. The report expands on the vertical five spot and the infinite length horizontal wells configurations by evaluating those configurations in a reservoir with a heterogeneous permeability distribution. In order to determine the effects of high permeability paths on well configurations, the distribution is evaluated both in its standard orientation and upside down. High permeability paths exist in the upper portion of the reservoir in the standard orientation. Hence, flipping the reservoir over put those paths in the lower portion of the reservoir.The horizontal wells deliver higher recovery than the vertical five spot in the heterogeneous reservoir. Unlike the homogeneous case, the horizontal wells do not exhibit an optimum Rv/g in the heterogeneous reservoir. Instead, recovery improves as Rv/g decreases. Bottom positioned horizontal wells have more dependence on Rv/g when the high permeability path is low in the reservoir than when the path is high in the reservoir.The fully penetrated vertical five spot also does not demonstrate the same behavior in the heterogeneous reservoir as in the homogeneous reservoir. When high permeability paths are low in the reservoir, recovery improves monotonically as Rv/g decreases. However, when the high permeability paths are high in the reservoir, the optimum recovery is at an Rv/g of approximately 0.1 for the case we studied. At high R's the recovery is approximately equal for the heterogeneous reservoir whether the high permeability paths are high or low in the reservoir.
Description
| Type of resource | text |
|---|---|
| Date created | June 1996 |
Creators/Contributors
| Author | Williams Jr, Richard |
|---|---|
| Primary advisor | Blunt, Martin |
| Degree granting institution | Stanford University, Department of Petroleum Engineering |
Subjects
| Subject | School of Earth Energy & Environmental Sciences |
|---|---|
| Genre | Thesis |
Bibliographic information
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Preferred citation
- Preferred Citation
- Williams Jr, Richard. (1996). The Effects of Horizontal Well Placement and Gravity on Sweep Efficiency. Stanford Digital Repository. Available at: https://purl.stanford.edu/cq913sm6547
Collection
Master's Theses, Doerr School of Sustainability
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