The demand for permanent downhole monitoring systems (PDHMS's) has been increasing over the last two decades. These systems, along with other real-time and intelligent field technologies, provide real-time data that are crucial to both reservoir and production engineers with reservoir modeling and production strategies.

A PDHMS consists of two main parts, which are downhole and surface equipment. Although the installation cost of this equipment might not be significant if installed during initial completion or routine workover, replacing defective downhole equipment is costly as it will require a workover operation. Therefore, it is important to capitalize on all opportunities to retrieve and analyze defective downhole equipment to minimize future malfunction, increase the life expectancy, reduce operational cost, and enhance efficiency.

This paper studies several downhole gauge challenges to find out their root causes. This will help in enhancing future designs and reducing the number of downhole gauge replacements. These gauges were retrieved during scheduled workover operations on several wells. They were retrieved and sent to their manufacturers for Dismantle Inspection Failure Analysis (DIFA). The root causes were identified and the recommendations were implemented in all newer models.

In many cases, the issue was caused by only one component, which was either downhole gauge malfunctioning or port blockage of the gauge mandrel. The component may vary depending on the gauge manufacturer and model, with the most common causes being the Y-block/Y-splitter, debris and non-properly swaged ferrules.

The findings have been utilized by PDHMS manufacturers to amend and enhance their next generations. Taking advantage of as many opportunities as possible to retrieve and study failed equipment will assist oil and service companies to work together for developing more reliable models that can extend their run life even in harsh downhole environments.

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