By Joanne Liou, Associate Editor
Throughout the well construction process, multiple “limiters” can constrain the efficiency of the overall process. Recognizing these limiters and the negative effects they can have on capital efficiency, ExxonMobil developed the Limiter Redesign Process to reduce time and costs. The process highlights trends in mechanical specific energy to help the operator identify and extend limiters, identify risks, respond in real time and capture learnings. One initiative developed under the Limiter Redesign Process is the Fast Drill Process. It “helped determine what kind of dysfunction we were seeing downhole, which would in turn help us increase our ROP,” Marie Valenta of ExxonMobil said at the 2014 SPE Annual Technical Conference and Exhibition in Amsterdam on 28 October.
Two years after the process was launched, Fast Drill had pushed the operator’s global ROP average up by 43%. The operator then expanded the process to borehole management to maximize downhole motor differential rating and improve hole quality. “By 2011, we found that we had actually increased our footage per day by about 90% globally,” Ms Valenta, Fast Drill & Flat Time Reduction Coordinator for ExxonMobil, said.
As part of the Limiter Redesign Process, the operator’s drill teams around the world participate in monthly conference calls to share lessons learned or initiatives taken under the process. These typically fall into at least one of four categories: planning, real-time recognition and response, service provider engagement, and NPT reduction. “These are just the four buckets in which we are currently working on,” Ms Valenta stated. “In the future, there maybe an opportunity for additional.”
Besides the Fast Drill Process, ExxonMobil also developed the Flat Time Reduction initiative. The operator recognized that drilling accounted for only 20% of overall rig time, with the remaining 80% spent performing non-drilling operations. “We got really efficient in our rate of penetration, and we realized that we need to focus our efforts on other operations, which are necessary in the well construction process,” Ms Valenta explained. These include BOP testing, rig mobilization, running casing, cementing and completion operations. “They don’t produce an increase in depth, and they make up the majority of the entire well scope.”
One effort under the flat-time initiative was an alternative method to move subsea BOPs by using a tool outside its intended application. In a multiwell development program offshore Australia, several subsea BOPs needed to be moved for batch operations. A typical move would require the crew to rig down the diverter at surface and use a spider and gimble to handle the riser. Additionally, someone would have to ride in the moonpool to lock the slipjoint. “All of these somewhat dangerous operations were required in order to perform a subsea BOP move,” Ms Valenta explained. The team analyzed the potential use of a riser-handling tool that was originally designed to hang off the riser after an emergency disconnect. “They did an initial engineering analysis to determine this tool could actually handle the weight of the riser and the BOP stack.”
The drill team ended up using the tool on eight subsea BOP moves, saving an estimated 17 hours of rig time per move. The operator also determined that using the tool resulted in more efficient and safer operations. “It’s much safer because you’re eliminating the complexity and all these operations that would have been required to perform operation,” Ms Valenta said.
“We continue to work toward maximizing capital efficiency by implementing the Limiter Redesign Process, which includes Fast Drill and Flat Time Reduction. Safety aspects have definitely improved as critical-path operations are simplified or made more efficient or removed altogether,” Ms Valenta concluded. “We’re working to simplify the entire well construction process. We have an emphasis on working smarter, not faster.”
For more on the Limiter Redesign Process, please see SPE 170751, “Maximizing Capital Efficiency by Expanding the Limiter Redesign Process to Flat Time Operations.”