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  | isbn    = 0-89181-602-X

  | isbn    = 0-89181-602-X

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Studies of the [[hydrocarbon distribution]] in the Gulf Coast relative to the top of overpressure suggest hydraulic fracturing and seal integrity influence the vertical distribution of hydrocarbons, success ratios, and seal risk.<ref name=ch10r30>Fertl, W., H., Leach, W., G., 1988, Economics of hydrocarbon reserves in overpressured reservoirs below 18,000 feet in south Louisiana: SPE paper 18146, 16 p.</ref><ref name=ch10r46>Leach, W., G., 1993a, Fluid [[migration]], HC concentration in south Louisiana Tertiary sands: Oil & Gas Journal, vol. 91, no. 11, p. 71–74.</ref><ref name=ch10r47>Leach, W., G., 1993b, Maximum hydrocarbon window determination in south Louisiana: Oil & Gas Journal, vol. 91, no. 13, p. 81–84.</ref>

Studies of the [[hydrocarbon distribution]] in the Gulf Coast relative to the top of overpressure suggest [[Natural hydraulic fracturing of top seals|hydraulic fracturing]] and seal integrity influence the vertical distribution of hydrocarbons, success ratios, and seal risk.<ref name=ch10r30>Fertl, W., H., Leach, W., G., 1988, Economics of hydrocarbon reserves in overpressured reservoirs below 18,000 feet in south Louisiana: SPE paper 18146, 16 p.</ref><ref name=ch10r46>Leach, W., G., 1993a, Fluid [[migration]], HC concentration in south Louisiana Tertiary sands: Oil & Gas Journal, vol. 91, no. 11, p. 71–74.</ref><ref name=ch10r47>Leach, W., G., 1993b, Maximum hydrocarbon window determination in south Louisiana: Oil & Gas Journal, vol. 91, no. 13, p. 81–84.</ref>

==Success rate vs. depth==

==Success rate vs. depth==

[[file:evaluating-top-and-fault-seal_fig10-46.png|thumb|300px|{{figure number|2}}Distribution of hydrocarbons relative to the top of overpressure changes as reservoir depth changes.<ref name=ch10r47 /> Copyright: Oil & Gas Journal.]]

[[file:evaluating-top-and-fault-seal_fig10-46.png|thumb|300px|{{figure number|2}}Distribution of hydrocarbons relative to the top of overpressure changes as reservoir depth changes.<ref name=ch10r47 /> Copyright: Oil & Gas Journal.]]

The distribution of hydrocarbons relative to the top of overpressure changes as reservoir depth changes is shown in [[:file:evaluating-top-and-fault-seal_fig10-46.png|Figure 2]]. This pattern is consistent with loss of top seal integrity because of hydrofracturing rather than a simple loss of reservoir quality or other variable. Deeper reservoirs have the peak gas occurrence below the top of overpressure. This is consistent with the changing P_f with depth. As depth increases, confining pressure increases and thus the amount of pressure required to fracture the top seal (P_f) increases. As fracture pressure increases, the depth of the first intact top seal increases.

The distribution of hydrocarbons relative to the top of overpressure changes as reservoir depth changes is shown in [[:file:evaluating-top-and-fault-seal_fig10-46.png|Figure 2]]. This pattern is consistent with loss of top seal integrity because of [[Natural hydraulic fracturing of top seals|hydrofracturing]] rather than a simple loss of reservoir quality or other variable. Deeper reservoirs have the peak gas occurrence below the top of overpressure. This is consistent with the changing P_f with depth. As depth increases, confining pressure increases and thus the amount of pressure required to fracture the top seal (P_f) increases. As fracture pressure increases, the depth of the first intact top seal increases.

The relationship between depth of reservoir and depth of maximum cumulative production below the top of overpressure is fundamental to seal risk. Further work is required to relate the distribution of hydrocarbons to actual fracture pressure rather than simply depth below top of overpressure.

The relationship between depth of reservoir and depth of maximum cumulative production below the top of overpressure is fundamental to seal risk. Further work is required to relate the distribution of hydrocarbons to actual fracture pressure rather than simply depth below top of overpressure.