Controls of most currently used CT units consist of multiple hydraulic valves located in CTU Control Cabin (CTU CC) and other components, and work of valves predetermined by initial pre-set values. Main advantages of hydraulic-based CTUs such as flexibility, reliability and relative simplicity of hydraulic systems are often compromising with inability for adaptation in changing environment conditions, inaccurate range of settings of the hydraulic components, bulky design which affects on logistics and job preparation, rig-up and safe job execution. Most of the issues caused by hydraulics-based architecture of CTUs itself. Maintenance for such type of CT units based on time intervals and procedures only. Automated control systems implemented very seldom or not implemented at all on the most of such units so CTU operator doesn’t have ability to know current conditions of main systems.
Safety systems and ergonomics have been changed significantly over last years and now they are essential parts of oilfield service equipment. Unfortunately such advance features can be seen only in newest generation of CTUs when absolute majority of traditional CT units were designed in 1980–1990 when electronics was poorly and seldom used in CTU design for automated safety system control functions. In the most of the cases design of conventional hydraulic-based units cannot be easily upgraded for new automated features, or will require substantial investments.
All of listed issues lead to excessive injury rate during job executions and rig up, accidents, increase rig-up and rig-down time, limiting use of such types of CTUs in offshore operations due to bulky design and excessive weight. Also absence of automated control systems leads to more frequent rate of equipment failures in comparison to new CT units. It has been very challenging to keep minimum parts stock and order directly from manufacturer due to some of models production has discontinued, when another models are significantly modified. Finally that leads to extended lead time for parts and main components to remote locations, such as offshore platforms. At the end, all minor and major functions of control are dedicated to CTU operator and relay on reaction speed, knowledge and experience without cross-check of taken decision by automated control system.
The results of investigations demonstrate that many of catastrophic accidents during well intervention caused by “human error” can be simply eliminated by implementation of new generation of safety systems.
During “typical”, “standard” type of jobs attention of CT unit operator must be dedicated by 100 percent for control of the main parameters of CTU such as CT weight, circulation pressure, wellhead pressure, pump rates, CT depth and more. Lack of control is unacceptable – results and consequences can be catastrophic, especially for offshore operations. Under specific circumstances control on the well can be lost as well.
In nowadays safety is the fundamental key in planning for oil operators as well as for service companies. Sufficient level of Safety normally has been achieved by utilization of appropriate equipment with specific safety features, by training and certification of personnel.