This article is reprinted with permission from ExxonMobil.
In 2009, ExxonMobil engineers drilling into deep offshore oil deposits in the Gulf of Mexico unexpectedly encountered a particularly hard and abrasive rock formation. Instead of taking the drill bit half a day to drill through this formation, it ultimately took four runs, or trips in and out of the hole, and three weeks.
Yet just four years later, engineers were able to drill through the same formation in only one run and about a day.
The difference? An innovative approach to drilling that turned conventional industry wisdom on its head and is now reducing time, money and the environmental impact of oil and gas exploration and development.
For nearly a century, drilling engineers grappled with the challenges associated with vibrations along the drill string, which connects the drill bit to the rig at the surface. As the drill bit penetrates rock, the incredible force exerted on the system can cause the drill string to vibrate violently, which sometimes causes the tool to stop drilling, losing precious time.
The traditional approach to researching this problem was to focus on extreme scenarios. Scientists believed that by analyzing the large shocks and intense vibrations associated with extreme events, they would be able to figure out how to minimize damage. However, a team of ExxonMobil engineers and scientists broke new ground by upending that convention, convinced that the solution would come from preventing large vibrations from ever getting started in the first place. Instead of focusing on large vibration events, they developed drilling processes to mitigate vibrations when they are still small and manageable.
ExxonMobil engineers now tune the bottom part of the drill string, known as the bottom hole assembly, using proprietary modeling technology. Jeffrey Bailey, drilling mechanics advisor with ExxonMobil Development Company, compares the upgrade to making music.
“We now approach bottom hole assembly design in an analogous way to playing a stringed instrument,” he said.
“We now approach bottom hole assembly design in an analogous way to playing a stringed instrument,” he said. “If we need to modify the design to run at a higher rotational speed, then we shorten the length of the pipe between contact points, just as a musician moves his or her finger closer to the bridge to play a higher note.”
The research team also figured out how to identify and measure vibrations happening at the drill bit, using only measurements recorded by the rig equipment at the surface. This method is applicable to every well that we drill, is less expensive than measurements recorded at the bit, provides real-time data, and enables further optimization methods. The patent describing this methodology was recognized with an Edison Patent Award in 2015 by the Research & Development Council of New Jersey.
Bailey and his colleague Deniz Ertas aren’t new to drilling vibrations. They first developed the models that helped inform their winning approach to vibration mitigation two decades ago. Today that patient research is steadily proving its effectiveness in places like Qatar, Abu Dhabi and the Gulf of Mexico. The technology is also helping drillers reach incredible depths. In 2015, ExxonMobil and its partners drilled a 13,500 meter extended-reach well at the Chayvo field, which lies in Pacific Ocean waters off the eastern coastline of Russia’s Sakhalin Island.
“It took several years to build up to the point where we have the amount of confidence in the method that we do today,” said Bailey. “It’s just been a matter of conviction that the technology works and then persistence and seeing it to completion.”