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Line 44: − The following figure is an FPP of a portion of a fault in a Gulf Coast field. It shows the juxtaposition of sands along the fault and the observed distribution of hydrocarbons. Sands are shown in gray (hanging wall) and orange (footwall).+ − [[file:evaluating-top-and-fault-seal_fig10-26.png|thumb|{{figure number|10-26}}See text for explanation.]]+ − ==Determine seal behavior==+ − Examples of cross-leaking and cross-sealing portions of the fault are shown in the following figure, which is a detail of Figure 10-26. Juxtapositions of the 7100/7100 sands and the 7200/7200 sands are cross leaking (left). These sand/sand juxtapositions have common hydrocarbon contacts across the fault. The portion of the fault juxtaposing the 7100/7200 sands, however, is cross sealing (right). Hydrocarbons in the 7200 sand in the hanging wall (R<sub>u</sub>) are juxtaposed with water-wet sands of the 7100 sand in the footwall (R<sub>d</sub>). − + − SGR is calculated over the surface of the entire fault. The following figure is a map of the SGR contoured on the FPP of the fault in Figure 10-26. SGR—and seal potential—vary over the surface of the fault as the throw and stratigraphy change. Areas of high SGR are shown in red and orange. Areas of low SGR are shown in purple and blue. − + + + − The SGR is calculated for each known sealing and leaking segment of the fault. The SGRs of two cross-leaking and cross-sealing segments of the fault are shown in the following figure (location is on Figure 10-33). SGR values along the cross-leaking sand/sand juxtapositions are high (red). Cross-leakage (right) occurs at both the 7100/7100 and 7200/7200 juxtapositions. Cross-seal (left) occurs where the 7100 sand is juxtaposed with the 7200 sand. This cross-sealing segment is characterized by low SGRs (blue). Cross-leakage occurs where the SGR is high; cross-seal occurs where it is low. − + + + + +
Fault seal analysis example: Gulf Coast (view source)
Revision as of 15:27, 6 February 2014
, 15:27, 6 February 2014no edit summary
==Procedure==
==Procedure==
[[file:evaluating-top-and-fault-seal_fig10-26.png|thumb|{{figure number|1}}See text for explanation.]]
The table below outlines a procedure for analyzing fault seal behavior.
The table below outlines a procedure for analyzing fault seal behavior.
==Construct an FPP==
==Construct an FPP==
[[:file:evaluating-top-and-fault-seal_fig10-26.png|Figure 1]] is an FPP of a portion of a fault in a Gulf Coast field. It shows the juxtaposition of sands along the fault and the observed distribution of hydrocarbons. Sands are shown in gray (hanging wall) and orange (footwall).
==Determine seal behavior==
[[file:evaluating-top-and-fault-seal_fig10-27.png|thumb|{{figure number|2}}See text for explanation.]]
[[file:evaluating-top-and-fault-seal_fig10-27.png|thumb|{{figure number|10-27}}See text for explanation.]]
Examples of cross-leaking and cross-sealing portions of the fault are shown in [[:file:evaluating-top-and-fault-seal_fig10-27.png|Figure 2]], which is a detail of [[:file:evaluating-top-and-fault-seal_fig10-26.png|Figure 1]]. Juxtapositions of the 7100/7100 sands and the 7200/7200 sands are cross leaking (left). These sand/sand juxtapositions have common hydrocarbon contacts across the fault. The portion of the fault juxtaposing the 7100/7200 sands, however, is cross sealing (right). Hydrocarbons in the 7200 sand in the hanging wall (R<sub>u</sub>) are juxtaposed with water-wet sands of the 7100 sand in the footwall (R<sub>d</sub>).
==Calculate SGR and construct SGR map==
==Calculate SGR and construct SGR map==
[[file:evaluating-top-and-fault-seal_fig10-28.jpg|thumb|{{figure number|10-28}}See text for explanation.]]
[[file:evaluating-top-and-fault-seal_fig10-28.jpg|thumb|{{figure number|3}}See text for explanation.]]
SGR is calculated over the surface of the entire fault. [[:file:evaluating-top-and-fault-seal_fig10-28.jpg|Figure 3]] is a map of the SGR contoured on the FPP of the fault in [[:file:evaluating-top-and-fault-seal_fig10-26.png|Figure 1]]. SGR—and seal potential—vary over the surface of the fault as the throw and stratigraphy change. Areas of high SGR are shown in red and orange. Areas of low SGR are shown in purple and blue.
The SGR is calculated by “rubber-banding” the stratigraphy in adjacent well logs to fit the stratigraphic cutoffs on the FPR The detailed log stratigraphy is necessary for reliably calculating SGR. The rubber-banding corrects for apparent thicknesses in both the well and fault plane profile.
The SGR is calculated by “rubber-banding” the stratigraphy in adjacent well logs to fit the stratigraphic cutoffs on the FPR The detailed log stratigraphy is necessary for reliably calculating SGR. The rubber-banding corrects for apparent thicknesses in both the well and fault plane profile.
==Example: correlating SGRs, seal behavior==
==Example: correlating SGRs, seal behavior==
[[file:evaluating-top-and-fault-seal_fig10-29.png|thumb|{{figure number|10-29}}See text for explanation.]]
[[file:evaluating-top-and-fault-seal_fig10-29.png|thumb|{{figure number|4}}See text for explanation.]]
[[file:evaluating-top-and-fault-seal_fig10-33.png|thumb|{{figure number|5}}See text for explanation.]]
The SGR is calculated for each known sealing and leaking segment of the fault. The SGRs of two cross-leaking and cross-sealing segments of the fault are shown in [[:file:evaluating-top-and-fault-seal_fig10-29.png|Figure 4]] (location is on [[:file:evaluating-top-and-fault-seal_fig10-33.png|Figure 5]]). SGR values along the cross-leaking sand/sand juxtapositions are high (red). Cross-leakage (right) occurs at both the 7100/7100 and 7200/7200 juxtapositions. Cross-seal (left) occurs where the 7100 sand is juxtaposed with the 7200 sand. This cross-sealing segment is characterized by low SGRs (blue). Cross-leakage occurs where the SGR is high; cross-seal occurs where it is low.
==Calibrating SGR threshold==
==Calibrating SGR threshold==