= Solution
Potential leakage paths are permeable or reactivated <faults> and connected fractures cutting the sealing sequence; lateral migration through connected reservoir layers into an unsealed outcrop or spill point; and natural or artificial penetrations such as poorly sealed abandoned wells or a compromised injection well. Injection raises <pore pressure>, potentially overcoming the <capillary entry pressure> of a seal, hydraulically opening fractures, or causing <fault> reactivation through reduced <effective stress>.
Seal continuity and <porous permeability> matter more than the rock name alone: a fractured or porous <limestone> need not be an effective <caprock>. Dissolution, chemical alteration or well-cement degradation can change leakage pathways over time. The underlying salt may be an effective barrier beneath the reservoir, but it does not seal the roof. Conversely, dissolved or residually trapped <carbon dioxide> is less mobile than a connected buoyant free-fluid phase, so connected porosity and fluid state also affect leakage.
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