Optimizing CT Material Properties for Extended Reach Operations

Abstract

There is a demand in the industry for coiled tubing (CT) that can safely reach significantly farther in horizontal wells than the current, steel based technology can reach. Some have suggested that CT composed of lighter materials could maintain a neutral or positive buoyancy (floating) in the horizontal section and thus be capable of reaching extraordinary total depths without exceeding their yield limit. However, several other aspects of CT operations must be considered for a complete assessment of extended reach capability, and these aspects often cause lighter materials to friction lock at shallow depths relative to their steel counterparts. Using a parametric analysis, this paper will quantify the effect material properties, including stiffness and density, have on CT performance in extended reach wells. It will also correlate those properties with materials available today such as steel, titanium, and composites to explain why steel tubing is used in most CT operations.

Corrosion resistance of steel for coiled tubing units

“…According to the results of studies of total corrosion in five working solutions, it was found that the corrosion rate in acidic [22,23] solutions (I, II) is significantly higher than in neutral [24] (III, IV, and V). For ease of analysis, the results of corrosion studies are presented separately for acidic and neutral working solutions.…”

“…Continuing to work in this direction, the authors want to consider in more detail the action of gas hydrates on the corrosion resistance [18,19,24] of CT pipes. Especially, action acidic gases such as H 2 S and CO 2 , which are components of gas hydrates, and dissolve in water, can accelerate the internal pitting corrosion of CT pipes.…”