The presence of residual hydrocarbons in depleted gas reservoirs contributes to explosion potential primarily because these hydrocarbons remain as combustible gases within the reservoir. Since depleted gas reservoirs are partially emptied of their original natural gas, the residual hydrocarbons constitute a mixture of flammable gases trapped in the porous rock formations. If these gases migrate or leak to the surface or into zones where oxygen is present, they can mix with air and create an explosive atmosphere.
Here are key points explaining how residual hydrocarbons influence explosion risk:
- Residual hydrocarbon gas presence: Even after production, a certain volume of hydrocarbon gases remains trapped in the reservoir rock pores. These gases are typically methane and other natural gas components, which are highly flammable.
- Mixing with air: When residual hydrocarbons leak due to well integrity failure or fractures in the caprock, they can come into contact with oxygen. This can form flammable mixtures that, if ignited, may result in explosions.
- Tank or wellhead hazards: The infrastructure associated with depleted gas reservoirs—such as wells and surface facilities—can accumulate these hydrocarbons, increasing the risk of explosive atmospheres if not properly ventilated or monitored.
- Cushion gas role: Residual hydrocarbons can act similarly to cushion gas in underground storage, maintaining pressure but also representing a flammable hazard that requires management to prevent unsafe conditions.
- Storage and safety implication: When depleted reservoirs are considered for other purposes (e.g., CO2 or hydrogen storage), the remaining hydrocarbons become a factor in safety assessments because they can compromise the integrity of the stored substance and pose explosion risks if disturbed or mixed unintentionally.
In summary, the explosion potential arises because residual hydrocarbons in depleted gas reservoirs are combustible gases trapped underground that, upon unintended release and mixing with air, can ignite. This necessitates careful monitoring, well integrity management, and risk mitigation when dealing with depleted reservoirs to prevent accidental explosions.
Original article by NenPower, If reposted, please credit the source: https://nenpower.com/blog/how-does-the-presence-of-residual-hydrocarbons-in-depleted-gas-reservoirs-contribute-to-explosion-potential/
