Stuck Coiled Tubing: Risks in a Complex Operating Environment

Abstract

This article, written by Senior Technology Editor Dennis Denney, contains highlights of paper SPE 163914, ’Stuck Coiled Tubing: Addressing the Risks in a Complex Operating Environment,’ by Rex Burgos, SPE, and Robin Mallalieu, SPE, Schlumberger, prepared for the 2013 SPE/ICoTA Coiled Tubing & Well Intervention Conference & Exhibition, The Woodlands, Texas, 26-27 March. The paper has not been peer reviewed. Sticking the coiled tubing (CT) is a major operational risk when performing a well intervention with CT. Stuck-pipe incidents often result in considerable production delay or, in the worst case, loss of the well. Mechanisms for dealing with stuck pipe are varied. Over the last decade, the profile of wells in which CT intervention has been used has evolved. The operating environment for today’s intervention can be more challenging, involving difficulties in wellbore trajectory, complexities in the completion, and an array of sophisticated tool assemblies that require conveyance. During this period, the approach to stuck-pipe avoidance or prevention has remained more or less unchanged. Introduction During the 10-year period of this study, several developments in the manner in which oil and gas wells are drilled and completed resulted in a change in the complexity of performing CT well interventions. An increase in intervention activity in horizontal or highly deviated extended-reach wells was found across most operating areas. The type of completions in several of these wells required running more-sophisticated bottomhole assemblies (BHAs) to achieve objectives similar to those in a less-aggressive well-bore environment. An example is the need to run tractors or vibrators in tandem with more standard tools to reach bottom and perform fill removal in extended-reach wells. Also, the great depths and complexity of these completions increased the time required to perform most interventions. Thus, there was a need for improving operational efficiency, which typically took the form of performing fewer runs to achieve the intervention objective, usually through the use of multifunction BHAs to eliminate tripping runs to the surface to change the configuration of the tool string. Unfortunately, additional complexity in the tool string, whether through added components or a more-elaborate design, typically added risk, including greater potential for sticking. Data collected for the period 2001–2010 showed that sticking incidents during CT interventions increased. Comparing data for the first 3 years (2001–2003) to data for the last 3 years (2008–2010), the number of reported sticking incidents increased more than threefold. Because the activity levels for the periods were not identical (increased by approximately 50% from one period to the next), a more-representative measure was found with a jobs-between-incidents (JBI) comparison. The JBI for the 2001–2003 period was 926, while the JBI for the 2008–2010 period was 524, a 43% deterioration in the JBI metric and an undesirable trend for this type of intervention activity.