In long horizontal wells, production rate is typically higher at the heel than at the toe. The resulting imbalanced production profile may cause early water or gas breakthrough into the wellbore. Once coning occurs, well production may be severely decreased due to limited flow contribution from the toe. To eliminate this imbalance, inflow control devices (ICDs) are placed in each screen joint to balance the production influx profile across the entire lateral length and compensate for permeability variation. Passive ICDs should be designed to control the influx without the need for intervention.
There are two basic pressure drop mechanisms used currently in ICDs, restriction or friction. Restriction mechanisms rely on a contraction of the fluid flow path to generate an instantaneous pressure drop across the device. A frictional device creates a pressure drop due to fluid flow along the length of a channel or tube.
There is an industry misconception that all ICDs will create a uniform influx. The reality is that none of these mechanisms alone meets the ideal requirements of an ICD designed for the life of the well: high resistance to plugging, mud flowback assurance, high resistance to erosion and high viscosity insensitivity.
This paper will detail the development of a new hybrid design that incorporates all the positive features necessary to effectively produce a well from startup, peak production, through eventual water onset and beyond. Available in standard or field-adjustable versions, this unique design maximizes flow areas to reduce velocities and increase erosion resistance. Fullscale performance testing validates that the hybrid design offers the highest level of viscosity insensitivity available. Because ICDs are permanent downhole components, their long-term reliability is imperative, and these new developments will improve their performance and ability to effectively balance inflow for the life of the well.
As discussed previously, the primary purpose of ICDs is to effectively balance well production throughout the entire operational life of the completion to optimize hydrocarbon recovery. Since a typical well with ICDs can be in production from 5 to >20 years, the long-term reliability of such a device is crucial to the well's overall success. The significant factor in the reliability of an ICD is its ability to maintain a uniform and controlled influx over the well life. If an ICD is not able to maintain a uniform flux rate, increased localized production rates will occur and the well will become unbalanced. This will render the ICD ineffective, leading to premature water and/or gas breakthrough and possible loss of sand control. At some stage in a well's life, water may break through into the wellbore in certain sections due to heterogeneities of the formation and/or vertical fractures. Ideally, once this occurs, flow contribution from these water-producing zones should not be greater than the oil-producing sections. The device should have the ability to add additional restriction to flow once the onset of water has occurred, thus allowing other oil producing zones to continue to flow effectively. In production wells with higherviscosity oil (>10 cp.), ICD type selection becomes a more critical factor due to the larger difference in viscosity between the oil and produced water. The pressure reduction mechanism in an ICD in this situation must have the lowest sensitivity to viscosity to maintain an even flow profile across the entire lateral wellbore. A restrictive-type ICD can provide desirable results in this regard due to its lower sensitivity to viscosity. This type of ICD however, requires a very small flow area to generate the pressure drop (restriction) required in ICD applications. This is a negative feature that has a greater potential for erosion and a low plugging resistance.