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Line 46: − The following figure is an example of an SGR calculation for a portion of a fault at progressive throws of 50, 100, and [[length::200 ft]]. Sands are patterned; shales are black. The black trace is an SP log.+ + + + + − + − + − [[file:evaluating-top-and-fault-seal_fig10-23.png|thumb|{{figure number|10-23}}See text for explanation.]]+ − − − −
Quantitative fault seal analysis (view source)
Revision as of 22:10, 18 February 2014
, 22:10, 18 February 2014→Step 2: Calculate the SGR
==Step 2: Calculate the SGR==
==Step 2: Calculate the SGR==
<gallery>
file:evaluating-top-and-fault-seal_fig10-22.png|{{figure number|1}}See text for explanation.
file:evaluating-top-and-fault-seal_fig10-23.png|{{figure number|2}}See text for explanation.
file:evaluating-top-and-fault-seal_fig10-24.jpg|{{figure number|3}}See text for explanation.
</gallery>
[[file:evaluating-top-and-fault-seal_fig10-22.png|thumb|{{figure number|10-22}}See text for explanation.]]
[[:file:evaluating-top-and-fault-seal_fig10-22.png|Figure 1]] is an example of an SGR calculation for a portion of a fault at progressive throws of 50, 100, and [[length::200 ft]]. Sands are patterned; shales are black. The black trace is an SP log.
The portion of the fault analyzed is adjacent to the R<sub>d</sub> sand in the hanging wall. The SGR is the ratio of the total sand divided by the total shale that has moved past the fault. The stratigraphy that has moved past this portion of the fault is marked in red. As the throw increases, more of the stratigraphy below the R<sub>u</sub> and R<sub>d</sub> sands moves past the fault and the SGR changes.
The portion of the fault analyzed is adjacent to the R<sub>d</sub> sand in the hanging wall. The SGR is the ratio of the total sand divided by the total shale that has moved past the fault. The stratigraphy that has moved past this portion of the fault is marked in red. As the throw increases, more of the stratigraphy below the R<sub>u</sub> and R<sub>d</sub> sands moves past the fault and the SGR changes.
A plot of SGR vs. throw, taken from the preceding example, is shown in the following figure. At small throws, very little shale has moved past the fault, the R sand is not completely offset, and the SGR is high. As the throw increases, progressively more shale is moved past the fault and the SGR decreases. At larger throws, a thick sand package begins to move past the fault and the SGR increases.
A plot of SGR vs. throw, taken from the preceding example, is shown in [[:file:evaluating-top-and-fault-seal_fig10-23.png|Figure 2]]. At small throws, very little shale has moved past the fault, the R sand is not completely offset, and the SGR is high. As the throw increases, progressively more shale is moved past the fault and the SGR decreases. At larger throws, a thick sand package begins to move past the fault and the SGR increases.
An SGR–throw plot shows the variation in SGR with increasing displacement for only one small area along the fault plane. In practice, SGR is calculated and mapped over the surface of the entire fault plane. [[:file:evaluating-top-and-fault-seal_fig10-24.jpg|Figure 3]] shows the variation in SGR for each point along the fault.
An SGR–throw plot shows the variation in SGR with increasing displacement for only one small area along the fault plane. In practice, SGR is calculated and mapped over the surface of the entire fault plane. The following figure shows the variation in SGR for each point along the fault.
[[file:evaluating-top-and-fault-seal_fig10-24.jpg|thumb|{{figure number|10-24}}See text for explanation.]]
==Determine SGR threshold==
==Determine SGR threshold==