The Exploration and Production (E&P) of crude oil and natural gas is a very complex process, which, among other aspects, involves sometimes quite challenging pipeline networks from an in-line inspection point of view. These include small-diameter gas flowlines that are of advanced age and/or were not designed for any sort of internal inspection or so-called “intelligent pigging.” The small diameter, combined with tight bends and insufficient flow and pressure conditions, often poses interesting challenges in achieving a high-resolution ILI.

A major European E&P operator had to clean and inspect a few 3" gas flowlines connecting different wells to a 10" main pipeline via underground T-pieces. Since commissioning, these pipelines had never been inspected before using ILI tools. Due to the main line connections and other varying circumstances, the ILI of these pipelines was performed in a bi-directional application using a half-batching approach in combination with High-resolution ultrasonic data gathering.

This paper describes in detail the preparation process, the cleaning and inspection tools used, and the operational procedure applying the half-batching approach to inspect such small difficult to inspect gas flowlines using high-resolution ILI tools and the results of such a “challenging project”.