Inflow-Control-Device Design: Revisiting Objectives and Techniques

Inflow-control devices (ICDs) were developed in response to early water breakthrough from the heel of prolific horizontal wells. In their initial applications, the design of ICD installations was based on equalizing flux (flow rate per unit length) along the length of a horizontal well, which required "choking" of flux in the heel region. In practice, these tools are often installed along the entire length of a horizontal well, with the logic that, because choking level is proportional to flow, the tool will automatically produce a more uniform flow profile. In this paper, we will re-examine the technical validity of equalizing flux along the length of the horizontal well. We will show that, in reservoirs with uniform permeability, the flux from the toe and heel regions should, in fact, be larger than that from the midsection. We will also show that delaying water or gas breakthrough is not the best reason for using ICDs. We will discuss the benefits of a new design philosophy whereby the well is segmented and choked at a level that regulates its flux to a value that produces a more-suitable flow for optimum reservoir management. This gives the operator the flexibility to design ICD layout to optimize various flow parameters, including time or cumulative production at water/gas breakthrough, location of first water/gas breakthrough, or any other parameter that fits the production strategy. This will be especially valuable for wells in variable-permeability reservoirs. A new design philosophy developed on the basis of this concept will be presented and its benefits demonstrated through a case history.