− | [[file:M91Ch13FG92.JPG|thumb|300px|{{figure number|14}}Comparison between (a) depth-converted seismic interpretation from the Gullfaks field, Norwegian North Sea, and (b) a plaster model deformed by plane strain extension. The plaster model shows that many small-scale faults are expected to exist in the Gullfaks structure but are below seismic resolution (from Fossen and Hesthammer<ref name=Fossenandhesthammer_1998>Fossen, H., and J. Hesthammer, 1998, Structural geology of the Gullfaks field, northern North Sea, in M. P. Coward, H. Johnson, and T. S. Daltaban, eds., Structural geology in reservoir characterization: Geological Society Special Publication 127, p. 231–261.</ref>). Reprinted with permission from the Geological Society of London.]]
| + | ==Subseismic faults== |
| + | M91Ch13FG92.JPG|{{figure number|14}}Comparison between (a) depth-converted seismic interpretation from the Gullfaks field, Norwegian North Sea, and (b) a plaster model deformed by plane strain extension. The plaster model shows that many small-scale faults are expected to exist in the Gullfaks structure but are below seismic resolution (from Fossen and Hesthammer<ref name=Fossenandhesthammer_1998>Fossen, H., and J. Hesthammer, 1998, Structural geology of the Gullfaks field, northern North Sea, in M. P. Coward, H. Johnson, and T. S. Daltaban, eds., Structural geology in reservoir characterization: Geological Society Special Publication 127, p. 231–261.</ref>). Reprinted with permission from the Geological Society of London. |
| + | M91Ch13FG93.JPG|{{figure number|15}}Fault maps of the East Pennine coalfield, United Kingdom. In map (a), only faults with throws of 20 m (64 ft) or more are shown. These are equivalent to faults that are detectable by seismic surveys at reservoir depths. In map (b), every mapped fault is shown, with fault throws of between 10 cm (4 in.) and 180 m (590 ft) (from Watterson et al.<ref name=Wattersonetal_1996>Watterson, J., J. J. Walsh, P. A. Gillespie, and S. Easton, 1996, Scaling systematics of fault sizes on a large-scale range fault map: Journal of Structural Geology, v. 18, no. 2/3, p. 199–214.</ref>). Reprinted with permission from the Journal of Structural Geology. |
| Only the faults that the geophysicist can pick from seismic data will be mapped, that is, those faults with vertical displacements down to the limit of seismic resolution. As mentioned in [[Data: sources]], this can be about 20–40 m for reservoirs at moderate depths. However, a significant number of subseismic faults will probably be present with vertical displacements less than this ([[:file:M91Ch13FG92.JPG|Figure 14]], [[:file:M91Ch13FG93.JPG|Figure 15]]). Thus, the true degree of the structural complexity of a reservoir will be underrepresented. | | Only the faults that the geophysicist can pick from seismic data will be mapped, that is, those faults with vertical displacements down to the limit of seismic resolution. As mentioned in [[Data: sources]], this can be about 20–40 m for reservoirs at moderate depths. However, a significant number of subseismic faults will probably be present with vertical displacements less than this ([[:file:M91Ch13FG92.JPG|Figure 14]], [[:file:M91Ch13FG93.JPG|Figure 15]]). Thus, the true degree of the structural complexity of a reservoir will be underrepresented. |
− | [[file:M91Ch13FG93.JPG|thumb|300px|{{figure number|15}}Fault maps of the East Pennine coalfield, United Kingdom. In map (a), only faults with throws of 20 m (64 ft) or more are shown. These are equivalent to faults that are detectable by seismic surveys at reservoir depths. In map (b), every mapped fault is shown, with fault throws of between 10 cm (4 in.) and 180 m (590 ft) (from Watterson et al.<ref name=Wattersonetal_1996>Watterson, J., J. J. Walsh, P. A. Gillespie, and S. Easton, 1996, Scaling systematics of fault sizes on a large-scale range fault map: Journal of Structural Geology, v. 18, no. 2/3, p. 199–214.</ref>). Reprinted with permission from the Journal of Structural Geology.]]
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| It is possible to input subseismic faults into a reservoir model using stochastic methods.<ref name=Muntheetal_1993>Munthe, K. L., H. Omre, L. Holden, E. Damsleth, K. Heffer, T. S. Olsen, and J. Watterson, 1993, Subseismic faults in reservoir description and simulation, Presented at the Society of Petroleum Engineers Annual Technical Conference and Exhibition, October 3–6, Houston, Texas, [https://www.onepetro.org/conference-paper/SPE-26500-MS SPE Paper 26500], 8 p.</ref> <ref name=Hollundetal_2002>Hollund, K., P. Mostad, B. F. Nielsen, L. Holden, J. Gjerde, M. G. Contursi, A. J. McCann, C. Townsend, and E. Sverdrup, 2002, Havana—A fault modelling tool, in A. G. Koestler and R. Hunsdale, eds., Hydrocarbon seal quantification: Norwegian Petroleum Society Special Publication 11, p. 157–171.</ref> In summary, this is a computerized procedure for randomly inserting shapes representing geological features into a 3-D model while still honoring predefined rules and statistics controlling the global distribution of the data. | | It is possible to input subseismic faults into a reservoir model using stochastic methods.<ref name=Muntheetal_1993>Munthe, K. L., H. Omre, L. Holden, E. Damsleth, K. Heffer, T. S. Olsen, and J. Watterson, 1993, Subseismic faults in reservoir description and simulation, Presented at the Society of Petroleum Engineers Annual Technical Conference and Exhibition, October 3–6, Houston, Texas, [https://www.onepetro.org/conference-paper/SPE-26500-MS SPE Paper 26500], 8 p.</ref> <ref name=Hollundetal_2002>Hollund, K., P. Mostad, B. F. Nielsen, L. Holden, J. Gjerde, M. G. Contursi, A. J. McCann, C. Townsend, and E. Sverdrup, 2002, Havana—A fault modelling tool, in A. G. Koestler and R. Hunsdale, eds., Hydrocarbon seal quantification: Norwegian Petroleum Society Special Publication 11, p. 157–171.</ref> In summary, this is a computerized procedure for randomly inserting shapes representing geological features into a 3-D model while still honoring predefined rules and statistics controlling the global distribution of the data. |