Changes

==Rates of leakage==

==Rates of leakage==

Even a small amount of [[Fracture|fracturing]] can result in staggering leakage rates. The volume of hydrocarbon that could be lost from a typical North Sea field, assuming a fractured top seal with a relatively low fracture [[permeability]] of only 0.05 md, is more than 100 billion bbl/m.y..<ref name=ch10r71 />). Fracture permeability can be as high as tens of darcys (<ref name=ch10r80>Stearns, D., W., Friedman, M., 1972, Reservoirs in fractured rock: AAPG Memoir 16, p. 82–106.</ref> and leakage rates consequently can be much higher.

Even a small amount of [[Fracture|fracturing]] can result in staggering leakage rates. The volume of hydrocarbon that could be lost from a typical North Sea field, assuming a fractured top seal with a relatively low fracture [[permeability]] of only 0.05 md, is more than 100 billion bbl/m.y.<ref name=ch10r71 /> Fracture permeability can be as high as tens of darcys<ref name=ch10r80>Stearns, D., W., Friedman, M., 1972, Reservoirs in fractured rock: AAPG Memoir 16, p. 82–106.</ref> and leakage rates consequently can be much higher.

Natural seeps confirm these high rates of hydrocarbon loss. The [[Palos Verde fault]] in Santa Monica Bay, California, seeps oil at the rate of 10–15 bbl/d or more than 5 billion bbl/m.y. The [[Coal Point seep]] in the Santa Barbara Channel, California, is leaking 50–70 bbl/d or more than 25 billion bbl/m.y.<ref name=ch10r95>Wilkinson, E., R., 1971, California offshore oil and gas seeps: California Oil Fields–Summary Operations, vol. 57, no. 1, p. 5–28.</ref>

Natural seeps confirm these high rates of hydrocarbon loss. The [[Palos Verde fault]] in Santa Monica Bay, California, seeps oil at the rate of 10–15 bbl/d or more than 5 billion bbl/m.y. The [[Coal Point seep]] in the Santa Barbara Channel, California, is leaking 50–70 bbl/d or more than 25 billion bbl/m.y.<ref name=ch10r95>Wilkinson, E., R., 1971, California offshore oil and gas seeps: California Oil Fields–Summary Operations, vol. 57, no. 1, p. 5–28.</ref>

[[Category:Predicting the occurrence of oil and gas traps]]  

[[Category:Predicting the occurrence of oil and gas traps]]  

[[Category:Evaluating top and fault seal]]

[[Category:Evaluating top and fault seal]]