Changes

  | part    = Predicting the occurrence of oil and gas traps

  | part    = Predicting the occurrence of oil and gas traps

  | chapter = Evaluating top and fault seal

  | chapter = Evaluating top and fault seal

  | frompg  = 10-1

  | frompg  = 10-46

  | topg    = 10-94

  | topg    = 10-46

  | author  = Grant M. Skerlec

  | author  = Grant M. Skerlec

  | link    = http://archives.datapages.com/data/specpubs/beaumont/ch10/ch10.htm

  | link    = http://archives.datapages.com/data/specpubs/beaumont/ch10/ch10.htm

  | isbn    = 0-89181-602-X

  | isbn    = 0-89181-602-X

}}

}}

Loss of top seal integrity by high [[strain]] and [[Fracture|fracturing]] is an important cause of dry holes and partially filled traps.<ref name=ch10r70>Skerlec, G., M., 1982, Risking top seals in the Central Graben: Exxon Production Research Company internal report.</ref><ref name=ch10r71>Skerlec, G., M., 1990, SEALS: A short course for risking top seal and fault seal: Franklin, Pennsylvania, SEALS International, 600 p.</ref> Although fracturing is commonly predicted from [[stress]], the advantage of strain analysis is that it provides a practical  tool prior to drilling for evaluating prospects using [[seismic data]].

Loss of top seal integrity by high [[Wikipedia:Deformation(mechanics)|strain]] and [[Fracture|fracturing]] is an important cause of [[dry hole]]s and partially filled traps.<ref name=ch10r70>Skerlec, G., M., 1982, Risking top seals in the Central Graben: Exxon Production Research Company internal report.</ref><ref name=ch10r71>Skerlec, G., M., 1990, SEALS: A short course for risking top seal and fault seal: Franklin, Pennsylvania, SEALS International, 600 p.</ref> Although fracturing is commonly predicted from [[Wikipedia:Stress (mechanics)|stress]], the advantage of strain analysis is that it provides a practical  tool prior to drilling for evaluating prospects using [[seismic data]].

==Rates of leakage==

==Rates of leakage==

Even a small amount of 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>

==See also==

==See also==

[[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]]