Changes

[[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 causes|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 [[Seal failure prediction|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 amount of pressure required to fracture the top seal (P_f) with depth. As depth increases, confining pressure increases and thus the 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 causes|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 [[Seal failure prediction|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 amount of pressure required to fracture the top seal (P_f) with depth. As depth increases, confining pressure increases and thus the 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 [[Risk:_expected_value_and_chance_of_success#Probability_of_geological_success|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 [[Risk:_expected_value_and_chance_of_success#Probability_of_geological_success|seal risk]]. Further work is required to relate the distribution of hydrocarbons to actual fracture pressure rather than simply depth below top of overpressure.