Lohr et al. 2015 Prediction of Subsesimic faults and fractures, . AAPG bulletin v 92 p 473-485 reproduced courtesy of AAPG
Ever had that experience when production data from two nearby wells is showing they just don't connect, yet there are no obvious structural or stratigraphic barriers?
There are no shortage of subtleties which can impact reservoir flow - stratigraphy and diagenesis are frequently culprits for example. It is often very difficult to make a lot of progress with those. Yet there is another culprit to consider ruling out first before considering these more difficult scenarios. What sub-seismic structure might be acting?
Fault seal issues associated with seismically resolvable faults are sometimes obviously the problem - and PAETORO can help with that - see the fault seal page. However, faults and fracture networks don't have to be seismically resolvable to have a potentially big impact on reservoir flow. Strike-slip faults are very good at generating continuous cataclasis yet can possess only minor vertical offsets, if any. Sub-seismic scale normal or thrust faults can still be quite efficient conduits for calcite or quartz vein precipitation. Faults that are very clear distinct breaks in some underlying lithologies, might be more distributed zones of shear in a different reservoir lithology - with a whole lot of different deformation mechanisms and more subtle fractures.
There are clues that can be checked at a regional level to assess the likelihood of some of these phenomena. Also very subtle changes in geometry, and checks of structure underneath the reservoir units might give further clues. Sometimes we can get so focussed on the reservoir units that the significance of minor structuration in deeper or overlying units can be overlooked. It never hurts either to systematically look at coherence time slices through a volume. Even in relatively quiescent tectonic times, the compaction subtleties of major underlying faults can have major effects on deposition, and may still generate enough low-level activity over geological time to impact reservoir performance along smaller faults.
If you encounter problems like this, PAETORO is well placed to review tectonostratigraphic histories and subtle features of your seismic volumes, to assess whether sub-seismic structural features could be to blame. It may well be that diagenetic or stratigraphic complexities are causing the problem, perhaps combined with and influenced by the structural elements. If that's the case, then structure can be used as a predictor for stratigraphic and diagenetic subtleties as well. Whatever the case, if candidates for structural interference are identified, it can point to other areas where calibration might be easier, and/or guide placement of future producers or injectors to test and clarify the issue.