BUILDING A RESERVOIR MODEL WITH CROSSING CONJUGATE FAULTS

摘要

Certain fault geometries can be extremely difficult or even impossible to incorporate into reservoir models due to limitations of the model-building software. Including Y or lambda faults in a reservoir model is a well-known problem, but even more difficult is the inclusion of the half-Y or half-lambda faults created by overlapping convergent or divergent conjugate faults. In these situations, the faults have the truncation characteristics of Y or lambda faults along part of their length, but are not truncated in other sections. Existing modeling methods cannot include such geometries in reservoir models; the modeler usually removes such faults from the model or changes the fault shape so that intersections do not occur. Both of these workarounds alter the reservoir model so that it no longer correctly portrays the actual structure. In our methodology, Y and lambda faults are not considered special cases and can be easily and routinely included in the reservoir model. The ability to specify and manipulate compound areas of fault surfaces enables the reservoir modeler to create the correct truncations of half-Y or half-lambda faults without compromising the true structure. These geometries are carried through to the reservoir grid without compromise. The inclusion of such problematic faults in the reservoir model ensures that volumes are correctly calculated within fault blocks, as the faults have not been altered. The sealing nature of these faults can also be assessed and incorporated into the reservoir model, as the faults are an integral part of the reservoir framework. The ability to include these complex fault geometries in a reservoir model is a significant break-through in model-building technology. Asset teams can now work with a complete and accurate reservoir model and no longer need to ignore significant structural components simply because of artificial modeling software limitations.