System-Engineering Recommendations Aim To Improve Intelligent Completions
Authors: Carpenter Chris 
Published: May 2023

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This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper SPE 209965, “System Engineering Recommendations To Improve Intelligent Completions,” by Ron Nelson, SPE, Consultant; Eric Handley, MacDermid Offshore Solutions; and Jonathon Joubran, SPE, Halliburton, et al. The paper has not been peer reviewed.

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The complete paper compiles recommendations from a broad range of sources into a single document to aid future intelligent-completion installations and operations. While emphasis is placed on subsea completions, these recommendations can be applied readily to differing well types. Important differences between production wells and injection wells also are addressed.

Introduction

Intelligent-completion interfaces span drilling, completions, facilities, production operations, and subsea-systems-engineering disciplines. Affected system components include the tree and tubing hanger, control system, control fluid, control lines, well fluids, well casing, downhole sensors, feed-through packers, and interval control valves (ICVs). Example diagrams are provided in Appendix B of the complete paper.

While a successful intelligent completion can enhance a well’s value significantly, a failed intelligent completion can severely diminish that value, possibly rendering the well inoperable.

Proposed Intelligent-Well-Design Process

Control-Fluid Selection. The design process should start with the control fluid, which provides hydraulic force to open and close the ICV. It traverses the entirety of the system and will affect most system components. A successful control fluid will accomplish the following goals, which are further detailed in the complete paper:

- Provide adequate lubricity

- Maintain required properties across all design temperatures

- Be compatible with all materials

- Be compatible with completion brines

- Provide adequate hydrate inhibition

- Minimize environmental impact

If the intelligent completion is to be installed in an existing development already using a fluid that cannot be used for the ICV, it may be possible to fill or “stack” the ICV lines with another control fluid that meets the downhole requirements and also is fully compatible with the in-service control fluid. The fluid’s original equipment manufacturer (OEM) should be consulted when a mixed-fluid system is considered.

Assessing Thermally Induced Pressure Gains. Once a preferred control fluid has been identified, the next recommended step is to assess worst-case thermally induced pressure changes in the control lines. Thermal effects directly affect numerous intelligent-completion components.

API SPEC 17D recommends keeping the tree-mounted ICV control-line isolation valves [tree-isolation valves (TIVs)] closed when not shifting the ICVs. At the other end of the control line, the ICV’s seals isolate the control fluids from the well fluids. Each downhole control line is a closed system when the TIVs are closed.

A closed control line will behave like a casing annulus in that internal pressure will rise when warmed and fall when cooled. The pressure changes in the lines, however, can be far greater than those seen in the casing annuli and can affect the intelligent completion system’s pressure requirements profoundly.