The purpose of this paper is to document an ongoing project called "Dual - velocity tubular running" which is being used to optimize the drill-string and casing running speeds, with the view to trip as efficiently and quickly as the rig and geo pressure limitations allow but doing so in a safe manner that prevents nonproductive time, both visible and invisible, and always retains the wells integrity and allows safe operations. Dual speed refers to the ability to target an initial speed to safely break the mud gels, and a second tripping speed permissible once those same gels are broken, and this is illustrated in Figure 1.
This ‘dual speed’ optimization approach can be achieved by a more advanced use of mud gel-break and rheology data and a new auto sequence for stepwise axial velocity control.
This project is a step change in targeting an autonomous and optimized drilling process, and the impressive results that can be achieved can be seen in figure 2 above.
As many authors have noted, such as Cayeux E., E. W. Dvergsnes, F. P. Iversen 2009 there are many factors that contribute to nonproductive time, which include Lost circulation, formation influx, pack-offs and other stuck pipe events which cause delays, problems, lost time, and generally increase risk, and cost of the well, during drilling operations. Each of these has the potential to escalate into serious problems that can result in undesirable technical sidetracks. Couple this with ever more complex wells, (whether they be long horizontal sections, multi-laterals, etc.), and ensuring operations are done safely and efficiently is paramount. Furthermore, the traditional metrics of time and cost, are now further modified by the requirements to reduce the carbon footprint of operations. Anything which allows the well operations to be completed more quickly reduces the carbon footprint of the operation. The solution and concept presented in this paper showcases a modelling approach which allows all these situations to be accurately modelled in a transient setting, to optimize tubular running speeds – be that drill pipe, casing, liners, expandable liners, sand screens or any tubular string run in hole, and then also compared and back modelled using all the available real time high frequency data. This coupled with an automated drilling control system has resulted in safe, record-breaking drilling achievements in the North Sea. The models allow updated safeguards to be applied to the drilling control system to maintain a downhole pressure within the acceptable limits of the open hole formations. It also automatically stops the movement of the drill string in case of abnormal hook loads or surface torques. Since automatic actions can be triggered in case of an unexpected situation, some standard procedures have been fully automated, including friction tests and back-reaming. In prior papers such as Cayeux E., B. Daireaux, E. W. Dvergsnes, 2010," Automation of Mud-Pump Management : Application to Drilling Operations in the North Sea , the peak surge seen when pipe is first moved and gels are ‘broken’ has been used as the limit for safe tripping, however that precluded further optimization that exists once gels are broken, and pipe and fluid is in motion. This optimization process will be discussed in detail in this paper.