By Joanne Liou, editorial coordinator
Within the relationship among surface, rig and downhole activities, there is an opportunity to change factors that can improve the reliability of the drilling system, stated Walt Aldred, scientific advisor and research director at Schlumberger. To support implications of the potential benefits of automation beyond the surface, Mr Aldred presented studies and performance indicators at the IADC Advanced Rig Technology Conference & Exhibition on 20 September in Houston.
Automated rig, in these studies, implies drilling units that have fully integrated AC variable frequency drives (VFD) Mr Aldred said. Referencing rotary steerable system (RSS) performance and reliability studies by Schlumberger, he asserted that the benefits of automated rigs are evident– average run length of 2,213 ft compared with 1,344 ft on other rigs, significantly higher mean footage and time between failure, and 33% reduction in overall cost. “There is a huge difference between reliability, and all that is changing is the surface system,” Mr Aldred said. “Downhole drills are the same; the maintenance procedure is the same. It’s really down to what’s happening on the surface.”
Even between the latest generations of automated rigs exists a positive difference in RSS reliability. “As we go through higher levels of integration (of rig automation), we end up with much more reliable systems,” he said.
Results from a more recent study further emphasize the benefits of automation, Mr Aldred said. Key performance indicators, such as 20% improvement in footage/circulating hour, reflect how automated rigs maintain a lower level of problems but with a higher level of reliability, according to Mr Aldred. Comparing two wells on the same field, one drilled with a mechanized, semi-automated system and the other with a manual system, Mr Aldred pointed to visible differences in smoothness of operations on the well logs.
Besides the rig, other factors can increase tool reliability: tool design, tool maintenance, bottomhole assembly design, drilling environment and drilling parameters. Once downhole tools are designed and built, they are put through tests and simulations before being integrated into the drilling process. “We test it on surface with shake-and-bake tests, where we smack them around for high shocks and increase the temperature and do some pressure testing,” Mr Aldred explained. “A lot of work goes on the surface and general testing facilities to make sure these tools are fit for the purpose before they go out to the well.”
“You have to get it into drilling with a real rig to make sure you are not missing some of those environmental impacts and rig impacts,” he added.
Although automation implies completion of tasks without a human hand, people still play an invaluable role in the drilling and completion processes when given the most fitting tasks. “We need to put humans in the right part of the loop – give them the right jobs to do,” Mr Aldred stated. “You’ve already seen what happens when we integrate the system on surface, but if we properly integrate it into downhole system as well, we can look forward to much higher reliability of the entire drilling system, not just in individual components.”