Safer, Faster, and More-Reliable Operations With Next-Generation Offshore Coiled Tubing Unit

Abstract

Most coiled tubing (CT) interventions are performed in a rigless environment. In fact, this is one of the important drivers for the widespread acceptance and continued growth of the technique for well servicing, especially in the offshore domain where the logistical costs are higher and operational challenges are more complex. Unlike land-based CT operations where integration is straightforward, the issues of equipment packaging for offshore integration is daunting. Overcoming limitations of crane-load lift capacity and deck space constraints are just part of the problem. Offshore CT units (CTU) are typically packaged as separate modules with components that require integration before any well intervention activity can begin. Rig up and operational efficiency are important design considerations for offshore CTU packages, but overall safety and regulatory compliance are of paramount concern. A new CTU configuration designed to meet the stringent demands of offshore CT operations was recently introduced. The design focused on key integration and HSE issues relating to the rig-up process. Results from more than 500 jobs performed during a 2-year period, in far eastern offshore environments indicated significant improvements in overall operational efficiency. In addition, the new designs met predefined HSE performance objectives, particularly during equipment rig-up phase. Introduction Since 2001, there has been a tremendous growth in the size of CTU service fleets. Based on an ICoTA survey, the total number of working CT units has grown from roughly 840 units in February 2001 to slightly more than 1,050 CTUs available worldwide in 2004. In March 2008, estimates for the global fleet size were reported at 1,500 units. During this period of growth, the scope of work for CT services also has continued to expand. This expansion brought some notable developments. First, the number of interventions increased in environments where standard CTU equipment packages were not intended to service, particularly in some offshore installations. The number of service quality incidents also increased, which resulted in several service delays. The failures are related to some degree to equipment packaging, but more so to the increased complexity in the performing these operations and to inexperienced younger service crews. Because most CTUs are provided by 3 or 4 large equipment manufacturers, the designs are very similar. Until recently, there was little need to radically evolve equipment designs. However, the well servicing environment is calling more and more for fit-for-purpose units, particularly offshore. From an equipment standpoint, addressing the challenges of offshore CT interventions currently is being approached in several effective ways and this has been the subject of previous discussions by Cochran (2008) and Andreassen (2004). The majority of these new equipment packages are customized insofar as specifications and features are concerned. However, the primary driver for customization is operational efficiency and overall safety.