A Model for the Connectivity of Horizontal Wells in Water-Flooding Oil Reservoirs

As current calculation models for inter-well connectivity in oilfields can only account for vertical wells, an updated model is elaborated here that can predict the future production performance and evaluate the connectivity of horizontal wells (or horizontal and vertical wells). In this model, the injection-production system of the considered reservoir is simplified and represented with many connected units. Moreover, the horizontal well is modeled with multiple connected wells without considering the pressure loss in the horizontal direction. With this approach, the production performance for both injection and production wells can be obtained by calculating the bottom-hole flowing pressure and oil/water saturation according to the material balance equation and a saturation front-tracking equation. Some effort is also provided to optimize (to fit known historical production performances) the two characteristic problem parameters, namely, the interwell conductivity and connected volume by means of a SPSA gradient-free algorithm. In order to verify the validity of the model, considering a heterogenous reservoir, three conceptual examples are constructed, where the number ratio between injection and production wells are 1/4, 4/1 and 4/5, respectively. It is shown that there is a high consistency between simulation results and field data.