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| Where complex fault systems exist between a trap and a source kitchen or between two traps, migration pathways are correspondingly complex. Traps in this setting can have widely different migration/fill or charge risks, depending upon fault seal behavior. | | Where complex fault systems exist between a trap and a source kitchen or between two traps, migration pathways are correspondingly complex. Traps in this setting can have widely different migration/fill or charge risks, depending upon fault seal behavior. |
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− | ==[[Migration]] parallel to faults== | + | ==Migration parallel to faults== |
| Where the dip of carrier beds is not perpendicular to faults, even cross-leaking faults can act as barriers as long as the [[permeability]] of the carrier bed is higher than that of the fault. Hydrocarbons can then migrate parallel to a fault rather than across the fault, even though the fault cross-leaks. This baffle effect can direct hydrocarbons away from potential traps as well as toward others. [[Migration]] pathway maps are critical to prospect assessment. | | Where the dip of carrier beds is not perpendicular to faults, even cross-leaking faults can act as barriers as long as the [[permeability]] of the carrier bed is higher than that of the fault. Hydrocarbons can then migrate parallel to a fault rather than across the fault, even though the fault cross-leaks. This baffle effect can direct hydrocarbons away from potential traps as well as toward others. [[Migration]] pathway maps are critical to prospect assessment. |
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| ==Example: Hudson field== | | ==Example: Hudson field== |
− | The Hudson field, North Sea, is an excellent example of how faults control migration pathways and charge.<ref name=ch10r36>Hardman, R., F., P., Booth, J., E., 1991, 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 the following figure show that the first well, 210/24a-l, was located on the crest of an obvious structural high. This well encountered water-wet Brent Group sands. 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.
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− | [[file:evaluating-top-and-fault-seal_fig10-30.png|thumb|{{figure number|10-30}}After .<ref name=ch10r36 /> Copyright: Geological Society of London.]] | + | [[file:evaluating-top-and-fault-seal_fig10-30.png|thumb|{{figure number|1}}After .<ref name=ch10r36 /> Copyright: Geological Society of London.]] |
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| + | The Hudson field, North Sea, is an excellent example of how faults control migration pathways and charge.<ref name=ch10r36>Hardman, R., F., P., Booth, J., E., 1991, 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 water-wet Brent Group sands. 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. |
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| 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 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 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. |
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− | ==Example: don field== | + | ==Example: Don field== |
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| + | [[file:evaluating-top-and-fault-seal_fig10-31.png|thumb|{{figure number|2}}After .<ref name=ch10r36 /> Copyright: Geological Society of London.]] |
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| In the Don field, North Sea, sealing faults prevent hydrocarbons from migrating into fault compartments on the crest of a large structural high.<ref name=ch10r36 /> Instead, hydrocarbons are trapped in several fault compartments on the flank of the structure against cross-sealing faults that have sand/sand juxtapositions. Wells in three fault compartments (211/18-5, 10, and 16) in the crest of the structure are dry. Hydrocarbons have either been trapped downflank or have been deflected to the southwest by sealing faults. | | In the Don field, North Sea, sealing faults prevent hydrocarbons from migrating into fault compartments on the crest of a large structural high.<ref name=ch10r36 /> Instead, hydrocarbons are trapped in several fault compartments on the flank of the structure against cross-sealing faults that have sand/sand juxtapositions. Wells in three fault compartments (211/18-5, 10, and 16) in the crest of the structure are dry. Hydrocarbons have either been trapped downflank or have been deflected to the southwest by sealing faults. |
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− | [[file:evaluating-top-and-fault-seal_fig10-31.png|thumb|{{figure number|10-31}}After .<ref name=ch10r36 /> Copyright: Geological Society of London.]]
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| ==See also== | | ==See also== |