Diffusive seal leakage
| Exploring for Oil and Gas Traps | |
| |
| Series | Treatise in Petroleum Geology |
|---|---|
| Part | Predicting the occurrence of oil and gas traps |
| Chapter | Predicting preservation and destruction of accumulations |
| Author | Alton A. Brown |
| Link | Web page |
| Store | AAPG Store |
Natural gas can dissolve in water to a significant enough degree that diffusion through water in the seal rock can result in substantial loss of gas, given geological time. Because of their very low solubility in water, black oils and high molecular-weight components of oil cannot leak by this mechanism, even at high temperatures.[1] Leakage rates determined in various published studies demonstrate the likelihood of gas accumulations lasting for tens to hundreds of million years (e.g., Montel et al.[2]
Predicting leakage
Only gas accumulations can be destroyed by diffusive leakage. For most seal lithologies, loss by diffusion is very slow; so most gas accumulations are preserved for tens to hundreds of millions of years. Rates of loss have been modeled,[2] but data necessary to quantitatively predict accumulation preservation at a particular prospect are difficult to acquire.
Diffusive leakage is favored by high temperature, high pressure, and a thin, porous seal. Older accumulations are more likely to be destroyed by this process, and late Cenozoic accumulations are not likely to be destroyed by this process.
See also
- Trap leakage
- Intact membrane seal leakage
- Fractured membrane seal leakage
- Hydrofractured seal leakage
- Micropermeable seal leakage
- Seal failure prediction
References
- ↑ McAuliffe, C. D., 1980, Oil and gas migration: chemical and physical constraints, in W. Roberts, and R. Cordell, eds., Problems of Petroleum Migration: AAPG Studies in Geology 10, p. 89–108.
- ↑ 2.0 2.1 Montel, F., G. Caillet, A. Pucheu, and J. Caltagirone, 1993, Diffusion model for predicting reservoir gas losses: Marine and Petroleum Geology, vol. 10, p. 51–57., 10., 1016/0264-8172(93)90099-E
External links
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