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  = 10-18

  | topg    = 10-94

  | topg    = 10-19

  | 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

}}

}}

Afault plane profile (FPP) is a cross section in the plane of the fault that shows both the hanging wall and footwall cutoffs.

A [[fault plane profile]] (FPP) is a [[cross section]] in the plane of the [[fault]] that shows both the [[hanging wall]] and [[footwall]] cutoffs.<ref name=ch10r86>Van Wijhe, D. H., M. Lutz, and J. P. H. Kaasschieter, 1980, The Rotliegend in the Netherlands and its gas accumulations: Geologie en Minjbouw, vol. 59, no. 1, p. 3–24.</ref><ref name=ch10r2>Allan, U. S., 1989, [http://archives.datapages.com/data/bulletns/1988-89/data/pg/0073/0007/0800/0803.htm Model for hydrocarbon migration and entrapment within faulted structures]: AAPG Bulletin, vol. 72, no. 7, p. 803–811.</ref><ref name=ch10r35>Hardman, R. F. P., and J. E. Booth, 1989, [http://archives.datapages.com/data/bulletns/1988-89/data/pg/0073/0007/0800/0812.htm Structural interpretation of hydrocarbon traps sealed by [[basement]] normal fault block faults at stable flank of foredeep basins and at rift basins]: AAPG Bulletin, vol. 72, no. 7, p. 813–840.</ref>Fault plane profiles are a fundamental tool for prospect assessment as well as a first step in understanding [[seal]] behavior in existing fields. Fault plane profiles are important because they show what is being juxtaposed across the fault. By doing so, they show areas of sand/sand and sand/shale juxtaposition, establish seal relationships, define potential fault-dependent [[Trap leakage|leak points]], and help assess [[hydrocarbon volume]]s.

An FPP is distinctive in two ways:

An FPP is distinctive in two ways:

==Procedure==

==Procedure==

We construct an FPP as we do any geologic cross section. Using structure-depth maps, we project the top of each mapped stratigraphic unit at its intersections with the fault plane to its correct depth on the fault plane profile.<ref name=ch10r2>Allan, U., S., 1989, Model for hydrocarbon [[migration]] and entrapment within faulted structures: AAPG Bulletin, vol. 72, no. 7, p. 803–811.</ref>

We construct an FPP as we do any geologic [[cross section]]. Using [[Subsurface_maps#Structure|structure-depth maps]], we project the top of each mapped stratigraphic unit at its intersections with the fault plane to its correct depth on the fault plane profile.<ref name=ch10r2>Allan, U. S., 1989, [http://archives.datapages.com/data/bulletns/1988-89/data/pg/0073/0007/0800/0803.htm Model for hydrocarbon migration and entrapment within faulted structures]: AAPG Bulletin, vol. 72, no. 7, p. 803–811.</ref>

Because only a fraction of the stratigraphy is mapped routinely, well logs are used to project the remainder of the detailed stratigraphy onto the FPP.

Because only a fraction of the stratigraphy is mapped routinely, well logs are used to project the remainder of the detailed stratigraphy onto the FPP.

==Example: FPP of cross-leaking fault==

==Example: FPP of cross-leaking fault==

[[file:evaluating-top-and-fault-seal_fig10-15.png|thumb|{{figure number|1}}See text for explanation.]]

[[:file:evaluating-top-and-fault-seal_fig10-15.png|Figure 1]] is a simple example of a fault plane profile. The sand reservoirs in the hanging wall (dark gray) and footwall (light gray) are shown on the same cross section drawn in the plane of the fault. In this example, all hydrocarbon [[accumulation]]s (black) are limited by [[Cross-leaking_faults#Juxtaposed_lithology_leak_points|JLLPs (juxtaposed lithology leak points)]]. Hydrocarbons cross-leak from the footwall sands into the hanging wall sands.

The fault cross-leaks along its entire surface at sand/sand juxtapositions. At each sand/sand juxtaposition, a JLLP spills the hydrocarbons across the fault. There is sufficient [[Calculating charge volume|charge]] to fill all closures to a fault-dependent leak point. Potential reservoirs with JLLPs at the crest are [[dry]]. The percent fill for other sands is constrained by the JLLPs.<ref name=ch10r2 /> If bed dips in the hanging wall allow entrapment against the fault, hydrocarbons could be trapped in both the hanging wall and footwall reservoirs. With sufficient charge, common hydrocarbon contacts could exist.

 

The fault cross-leaks along its entire surface at sand/sand juxtapositions. At each sand/sand juxtaposition, a JLLP spills the hydrocarbons across the fault. There is sufficient charge to fill all closures to a fault-dependent leak point. Potential reservoirs with JLLPs at the crest are dry. The percent fill for other sands is constrained by the JLLPs.<ref name=ch10r2 /> If bed dips in the hanging wall allow entrapment against the fault, hydrocarbons could be trapped in both the hanging wall and footwall reservoirs. With sufficient charge, common hydrocarbon contacts could exist.

==Example: FFP that cross seals, cross leaks==

==Example: FFP that cross seals, cross leaks==

[[file:evaluating-top-and-fault-seal_fig10-16.png|thumb|{{figure number|2}}See text for explanation.]]

The fault plane profile in [[:file:evaluating-top-and-fault-seal_fig10-16.png|Figure 2]] is similar to the profile in [[:file:evaluating-top-and-fault-seal_fig10-15.png|Figure 1]] except that the fault is cross sealing at the fault/reservoir intersection in the lowest foot-wall sand. Despite a sand/sand juxtaposition at the crest of this reservoir, the fault traps hydrocarbons at a cross sealing segment. Higher sands continue to cross-leak. The percent fill of the lowest sand is limited by either the [[displacement pressure]] (P_d) of the fault zone, the [[Calculating charge volume|charge volume]], or the top seal—not a JLLP.

The fault plane profile in [[:file:evaluating-top-and-fault-seal_fig10-16.png|Figure 2]] is similar to the profile in Figure 10-15 except that the fault is cross sealing at the fault/reservoir intersection in the lowest foot-wall sand. Despite a sand/sand juxtaposition at the crest of this reservoir, the fault traps hydrocarbons at a cross sealing segment. Higher sands continue to cross-leak. The percent fill of the lowest sand is limited by either the P_d of the fault zone, the charge volume, or the top seal—not a JLLP.

[[:file:evaluating-top-and-fault-seal_fig10-26.png|Figure 3]] is an example of a fault plane profile of a fault in a Gulf Coast field.

* [[Fault plane profile analysis pitfalls]]

* [[Fault plane profile analysis]]

* [[Avoiding pitfalls of fault plane profile analysis]]

==References==

==References==

[[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]]