Application of Inflow Control Devices to Heterogeneous Reservoirs

The rate of inflow to a long well can vary along its completion length, e.g. due to frictional pressure losses or reservoir heterogeneity. These variations often negatively affect the oil sweep efficiency and the ultimate oil recovery. Inflow Control Devices (ICDs) represent a mature well completion technology which provides uniformity of the inflow profile by restricting high specific inflow segments while increasing inflow from low productivity segments. This paper introduces a mathematical model for effective reduction of the inflow imbalance caused by reservoir heterogeneity. The model addresses one of the key questions of the ICD technology application—the trade-off between well productivity and inflow equalisation. Our analytical model relates the specific inflow rate and specific productivity index to well characteristics, in marked contrast to the numerical nature of existing, simulation-based models. Our model takes into account the intrinsically stochastic nature of reservoir properties along the well completion interval. A general solution to our model is available in a non-closed, analytical form. We have derived a closed form solution for some particular cases. The practical utility of the model is illustrated by considering a case study with prolific and medium productivity reservoirs. Finally, we identify certain limitations of using our model. These refer to cases when (i) annular flows can be neither neglected nor eliminated, and (ii) the neglect of frictional pressure losses is not a valid assumption, that is when both reservoir heterogeneity and friction have substantial impact on the inflow distribution.