Revisiting capacitance-resistance model connectivity estimates for directional and distance effects

Connectivity has been described as one of the fundamental reservoir characteristics which directly impacts recovery. Numerous studies have reported on how it can be measured and used to manage waterfloods. Largely missing from these reports, however, is how connectivity can be integrated with the available geological information to identify which geological features are controlling interwell communication. Having a structured approach to connectivity analysis helps to identify geological controls on fluid flow and avoids overlooking important features.

Through three cases, we show how connectivity—as measured using the capacitance-resistance model—can be systematically analyzed for geological information. Two methods—not used in prior literature—prove particularly useful for connectivity analysis. First, a semi-log crossplot of connectivity versus interwell distance helps compare connectivity behaviors from different parts of the reservoir to assess geological effects, provide initial estimates of connected region sizes, and establish the noise level in the results. Second, histograms of azimuthal sensitivities of connectivities offer insights into preferential orientations of geological features.

Two field cases are clastic reservoirs where the depositional features prove to be the primary controls on connectivity. One carbonate reservoir shows the effects of post-depositional characteristics on connectivity. All three cases illustrate how careful connectivity evaluations can inform waterflood recovery strategies.