Changes

==Gas loss by diffusion==

==Gas loss by diffusion==

Diffusive loss of gas through a top seal can also limit seal capacity (Leythaeuser et al., 1982; ..<ref name=ch10r59>Nelson, J., S., Simmons, E., C., 1995, Diffusion of methane and ethane through the reservoir cap rock: Implications for the timing and duration of catagenesis: AAPG Bulletin, vol. 79, no. 7, p. 1064–1074.</ref> Seal capacity is not simply related to the displacement pressure. Although diffusion can be important in entrapment of gas, diffusion coefficients for oil are so small that diffusion does not affect seal capacity relative to oil.

Diffusive loss of gas through a top seal can also limit seal capacity (Leythaeuser et al., 1982; ..<ref name=ch10r59>Nelson, J., S., Simmons, E., C., 1995, [http://archives.datapages.com/data/bulletns/1994-96/data/pg/0079/0007/1050/1064.htm Diffusion of methane and ethane through the reservoir cap rock: Implications for the timing and duration of catagenesis]: AAPG Bulletin, vol. 79, no. 7, p. 1064–1074.</ref> Seal capacity is not simply related to the displacement pressure. Although diffusion can be important in entrapment of gas, diffusion coefficients for oil are so small that diffusion does not affect seal capacity relative to oil.

Estimates of the diffusive loss of gas in the McClave field, Colorado, demonstrate that 57 bcf of gas can diffuse from a trap in only 0.5–5.0 m.y.<ref name=ch10r59 />

Estimates of the diffusive loss of gas in the McClave field, Colorado, demonstrate that 57 bcf of gas can diffuse from a trap in only 0.5–5.0 m.y.<ref name=ch10r59 />