An alternative to the standard graphical presentation of CT operating limits is proposed in this paper to facilitate design of CT well interventions and to guide operational decisions in critical, at-risk procedures. Typical issues in intervention design include maximum safe overpull and maximum safe circulating and annular fluid pressures and the interplay between these parameters. However, CT job designers are sometimes unfamiliar with the interrelation between tension and fluid pressures. In particular, the relationship between surface weight and actual tubing stress is often overlooked. This interrelation can be explained and interpreted via the concepts of effective and real force. Based on a presentation of effective and real force, this paper proposes a graphical presentation of CT limits which references effective force, specifically surface weight. Using this modified stress graph, safe operating limits can be more clearly inferred from actual job parameters such as surface weight and pressure.

You can access this article if you purchase or spend a download.