New Method for Connection Transmissibility Calculation

The paper reviews the problem of very low or zero productivity of simulated horizontal wells, when "connections" are placed in cells with zero vertical permeability (PERMZ). Such cells may imply, for instance, thin interlayering of permeable and impermeable interbeds inside one cell. The formulas are considered to calculate parameters describing the fluid flow to the "connection": the equivalent radius (R0j), transmissibility (khj), and the connection factor (Tj or CCFj). The conditional calculated examples show shortcomings of formulas and the reasons that lead to zero productivity of simulated wells. The author proposes refined formula to calculate Tj , R0j и khj, that account the well diameter going through the model cell. The formula imply that thinly-bedded vertically impermeable formation unit which has a plane-parallel filtration flow running across the area equal to well diameter multiplied by completion length. The applicability of the model for bigger cells is demonstrated by comparison of results obtained on the detailed grid. Bigger cells-based calculation results are close to those obtained on the detailed grid. The proposed formula can be used in dynamic simulators for more accurate simulation of fluid flowing to horizontal wells in case of bigger cells.