Well placement subclustering within partially oil-saturated flow units

Robust well placement strategies are decisive for upstream activities in the oil industry. In particular, flow units are used as an effective model for reservoir characterization and rock typing. However, the interplay between the petrophysical features of flow units, their intrinsic quality, rock mechanics, and ultimate production still deserves investigation. In an earlier paper (Oliveira et al., 2016), the authors have proposed a well placement technique based on graph theory to suggest competitive zones for increased production with fewer perforations in fully oil-saturated flow units. Although promising outcomes could be observed, the former approach disregarded the different fluid saturations within the flow unit domain. In this paper, we extend the technique to take the fluid saturation fields into account and correct the well placement. We now introduce a subclustering model intended to identify competitive completion points within partially saturated flow units. Subgraphs are used to yield partitions of the flow unit domain and marker functions similar to phase indicator functions commonly found in multiphase flow modeling are implemented to label flow units intersecting gas-oil, gas-water, or oil-water contacts. Once divided, the subclustered flow unit enables us to find new flow convergence points relevant for partially oil-saturated cases. We show that the oil cumulative production in oil-water cases, for instance, can be up to 10 times higher at the new points (SubMaxC) when compared to points chosen under the former approach (so-called MaxC). Additionally, we reinforce that the earlier approach remains valid as a locator of spots with competitive total fluid production, but better places are obtainable when a specific fluid is the target of production. The present approach is helpful to determine gas, oil, or even water production spots in two-fluid or three-fluid flow unit configurations.