Percent fill: controlling factors

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The percent fill of a trap is the percentage of the trap volume filled with hydrocarbons compared with its total volume. Percent fill can be controlled by a number of factors, including the following:

  • Top seal capacity/integrity
  • Synclinal spill points
  • Charge
  • Fault seal capacity
  • Fault-dependent leak points

Control summary

 
Figure 1 Controls on percent fill and hydrocarbon column height..

Figure 1 summarizes the various controls on percent fill and hydrocarbon column height. The maximum fill case is the synclinal spill point (SSP). A cross-leaking fault limits the percent fill to the juxtaposed lithology leak point (JLLP). A dip-leaking fault limits the percent fill to the fault plane leak point (FPLP).

A cross-sealing fault allows fill below the JLLP and possibly as deep as the SSP. A trap also may be partially filled (PF) due to either charge or top seal capacity. A partially filled trap can have a hydrocarbon contact at any depth.

Finite seal capacity of faults

Sealing faults may have some finite seal capacity. A fault may be able to support the pressure exerted by a 50-m hydrocarbon column but leak if the column increases to length::51 m.[1] Recent work suggests there may be a maximum seal capacity related to the percentage of shale in the fault gouge.[2][3] In most cases, however, the percent fill is significantly less and is limited by fault-dependent leak points rather than the seal capacity of the gouge.

See also

References

  1. Chong, K., P., Hoyt, P., M., Smith, J., W., Paulsen, B., Y., 1980, Effects of strain rate on oil shale fracturing: International Journal of Rock Mechanics, vol. 17, no. 1, p. 35–43., 10., 1016/0148-9062(80)90004-2
  2. Yielding, G., Freeman, B., Needham, D., T., 1997, Quantitative fault seal prediction: AAPG Bulletin, vol. 81, no. 6, p. 897–917.
  3. Skerlec, G., M., 1997b, Atlas of fault seal behavior in the Gulf Coast: Franklin, Pennsylvania, SEALS International, 4356 p.

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Percent fill: controlling factors