A Survey of Reservoir Rock Compaction, and Its Influence on Well Flow Tests
Abstract/Contents
- Abstract
- Rock properties such as porosity and permeability are dependent on the effective stress within the rock. The effective stress is approximately equal to the overburden pressure minus the fluid pressure, or to the net overburden pressure. Thus, compared with a normal porosity value measured at the surface, the in-situ value before production is lower due to the increased stress caused by the overburden pressure. As the reservoir fluid pressure declines the net confining pressure increases and the porosity gets smaller. The compressibility of rocks varies widely, values of pore compressibility ranging from 1 x 10 psi to more than 300 x 10 psi. In the Wilmington and Huntington Beach oil fields in Southern California, porosities calculated from formation density logs can be 5 to 10 porosity per cent lower than surface measured values. This can obviously have a considerable effect on calculated oil-in-place.As the reservoir fluid pressure declines, there will usually be decreases in permeability and effective rock compressibility. These changing values may significantly affect pressure buildup and drawdown calculations. A finite difference approximation to the radial flow unsteady-state "diffusivity" equation was developed to take account of the variations of permeability, porosity and effective fluid compressibility with fluid pressure. A mathematical model developed from this finite difference equation was solved on a high speed digital computer using the IBM Continuous System Modeling Program language.Published rock compressibility measurements are reviewed in this report and significant results are indicated. Relevant theory and data from other fields of science such as hydrology and soil mechanics are reviewed.The literature discloses that difficulties arising in the coring and testing of high-compressibility rocks limit data on them to a few cases where particular field problems have arisen. From these few data, it appears that high-compressibility rocks are apt to be geologically young and unconsolidated, with a high shale content.
Description
| Type of resource | text |
|---|---|
| Date created | June 1971 |
Creators/Contributors
| Author | Scorer, John D. |
|---|---|
| Primary advisor | Miller, Frank G. |
| 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
- Scorer, John D. (1971). A Survey of Reservoir Rock Compaction, and Its Influence on Well Flow Tests. Stanford Digital Repository. Available at: https://purl.stanford.edu/gd562sq0953
Collection
Master's Theses, Doerr School of Sustainability
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