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[[file:evaluating-top-and-fault-seal_fig10-30.png|300px|thumb|{{figure number|1}}Well located on the crest of an obvious structural high. After Hardman & Booth.<ref name=ch10r36 /> Copyright: Geological Society of London.]]

[[file:evaluating-top-and-fault-seal_fig10-30.png|300px|thumb|{{figure number|1}}Well located on the crest of an obvious structural high. After Hardman & Booth.<ref name=ch10r36 /> Copyright: Geological Society of London.]]

The Hudson field, North Sea, is an excellent example of how faults control [[migration pathways]] and [[Calculating charge volume|charge]].<ref name=ch10r36>Hardman, R., F., P., Booth, J., E., 1991, [http://sp.lyellcollection.org/content/56/1/1.abstract The significance of normal faults in the exploration and production of North Sea hydrocarbons], in Roberts, A., M., Yielding, G., Freeman, B., eds., The Geometry of Normal Faults: London, Geological Society of London, p. 1–16.</ref> The map and [[cross section]] in [[:file:evaluating-top-and-fault-seal_fig10-30.png|Figure 1]] show that the first well, 210/24a-l, was located on the crest of an obvious structural high. This well encountered [http://www.glossary.oilfield.slb.com/en/Terms/w/water_wet.aspx water-wet] Brent Group sandstones. A second well on the flank, 210/24a-2, encountered oil shows suggestive of a local [[stratigraphic trap]]. Thirteen years after the initial well, the 210/24a-3 well discovered the Hudson field: a fault-dependent trap.

The Hudson field, North Sea, is an excellent example of how faults control [[migration pathways]] and [[Calculating charge volume|charge]].<ref name=ch10r36>Hardman, R. F. P., and J. E. Booth, 1991, [http://sp.lyellcollection.org/content/56/1/1.abstract The significance of normal faults in the exploration and production of North Sea hydrocarbons], in A. M. Roberts, G. Yielding, and B. Freeman, eds., The Geometry of Normal Faults: London, Geological Society of London, p. 1–16.</ref> The map and [[cross section]] in [[:file:evaluating-top-and-fault-seal_fig10-30.png|Figure 1]] show that the first well, 210/24a-l, was located on the crest of an obvious structural high. This well encountered [http://www.glossary.oilfield.slb.com/en/Terms/w/water_wet.aspx water-wet] Brent Group sandstones. A second well on the flank, 210/24a-2, encountered oil shows suggestive of a local [[stratigraphic trap]]. Thirteen years after the initial well, the 210/24a-3 well discovered the Hudson field: a fault-dependent trap.

The sealing fault trapped hydrocarbons in a flank fault compartment and prevented hydrocarbons from migrating into the more obvious structural high to the west. Predrill [[fault seal analysis]] and a [[Migration pathway map construction|migration pathway map]] would have correctly identified the sealing fault and would have placed a much greater risk on the success of the first well. In this case, new [[seismic data]] identified the sealing fault; however, numerous examples exist where the same error is made with high-quality seismic data. Hydrocarbons do not simply migrate into the crest of structural highs.

The sealing fault trapped hydrocarbons in a flank fault compartment and prevented hydrocarbons from migrating into the more obvious structural high to the west. Predrill [[fault seal analysis]] and a [[Migration pathway map construction|migration pathway map]] would have correctly identified the sealing fault and would have placed a much greater risk on the success of the first well. In this case, new [[seismic data]] identified the sealing fault; however, numerous examples exist where the same error is made with high-quality seismic data. Hydrocarbons do not simply migrate into the crest of structural highs.