For depleted gas reservoirs to be suitable for compressed air energy storage (CAES), there are indeed specific porosity and permeability thresholds to ensure effective storage capacity and air flow.
Porosity Thresholds
- The reservoir porosity should generally be greater than 10%. This level of porosity ensures there is enough pore space to store a meaningful volume of compressed air.
- Some studies also mention that porosity below 10% is considered disqualifying for storage purposes, as it reduces storage capacity significantly.
Permeability Thresholds
- Permeability is critical to allow the injected air to flow efficiently during both injection and withdrawal phases of CAES operation.
- A permeability threshold of greater than 300 millidarcies (mD) is suggested to facilitate effective air flow.
- Specific analysis for depleted gas fields indicates permeability should be at least 600 mD or higher to adequately support the required air mass flow rates (e.g., hundreds of million standard cubic feet per day at operational pressures around 800 psi).
- Reservoirs with permeability below 10 millidarcies are typically excluded from consideration for storage projects.
Additional Considerations
- Depth, reservoir thickness, and sealing properties also play important roles but for porosity and permeability specifically, the above thresholds are key.
- These values ensure the reservoir can store sufficient air volume and provide the necessary flow rates to support CAES turbo-machinery efficiently without excessive pressure drops or flow restrictions.
In summary, depleted gas reservoirs intended for compressed air storage should ideally have porosity >10% and permeability >300 mD, with some analyses recommending permeability around 600 mD or higher to meet mechanical and operational flow requirements. Reservoirs falling below these values face challenges in storage capacity and injection/withdrawal performance for CAES systems.
Original article by NenPower, If reposted, please credit the source: https://nenpower.com/blog/are-there-specific-porosity-and-permeability-thresholds-for-depleted-gas-reservoirs-to-be-suitable-for-compressed-air-storage/
