By Joanne Liou, Associate Editor
The development of 20,000-psi drilling equipment and systems has been on industry’s agenda to meet operational needs in challenging frontiers. Although the BOP is a major focus in this effort, industry leaders agree that it goes beyond a single piece of equipment. It involves the entire rig and well design. “If we’re making larger BOPs, you’ve got all kind of issues – the physical size of it, where you’re going to store it, height restrictions, the weight of the BOP. How does that impact annular equipment, tensioners, riser analysis, larger choke/kill lines, higher shut-in pressures on casing?” Lance Labiche, VP of J Connor Consulting, said. “How does this impact well design? Can the downhole well handle these loads and 20K completion equipment?”
Mr Labiche, a former petroleum engineer with the US Bureau of Safety and Environmental Enforcement (BSEE) spoke as part of a panel that discussed the considerations and challenges to develop a 20,000-psi BOP at the 2014 IADC Advanced Rig Technology Conference in
Galveston, Texas, on 17 September. Other panelists were Frank Springett, VP & GM – Pressure Control Group at National Oilwell Varco, and Jean-Paul Buisine, Corporate Sub-Sea Operations Manager at Transocean. In February 2012, BP announced the launch of Project 20K to develop technologies over the next decade in four key areas: well design and completions; drilling rigs, riser and BOP equipment; subsea production systems; and well intervention and containment.
While higher pore pressures at deeper depths are driving the need for a 20K BOP system, recent regulatory changes add another layer of urgency. BSEE has changed how it calculates the maximum anticipated surface pressure (MASP) and maximum allowable working pressure (MAWP) values, Mr Labiche stated. “In the past, they used to assume 50% mud and 50% gas, but then they would also subtract hydrostatic from the seawater, thus lowering the required rating for the BOP,” he explained. “It never really was correct to begin with to subtract off the seawater.” The new calculation MAWPs by the amount of seawater hydrostatic.
For example, with a well in 8,000 ft of water, the MAWP will increase by more than 3,500 psi under the new calculation method. Some wells that had been drilled in the past with a 15K BOP might not meet required values to be drilled today. “This is one more reason why the 20K BOP system and rig system is needed. It’s going to be part of the Gulf of Mexico’s future.”
From the moonpool to handling and tensioning systems, numerous components will be impacted by the 5,000-psi increase. “Compared to what the 15K systems are, you’re 115,000 to 200,000 lbs heavier,” Mr Springett said. Christmas trees, for example, will need to be larger, as well as the handling equipment for Christmas trees. “Ultimately, when we take a look at the 20K system of a rig, it all funnels down to what is the weight of the stack, the weight of the system as a whole. A big focus in development is around things that can allow us to eliminate cavities.”
Looking at robustness and reliability around control systems, the focus still remains on bringing the weight down and the size down, Mr Springett continued. Another key is having retrievable pods to optimize the time between repair, “which is a really big piece of the picture on the subsea side.”
The sheer size and weight of a 20K system poses a challenge to rig integration. The variable bore ram design is a challenge for OEMs, especially with higher temperatures, Mr Buisine explained, since the higher temperature requirement will likely increase the number of rams needed. “Integrating (the 20K BOP) into an existing drilling rig is going to be huge challenge,” he stated. “This is really driving us to a newbuild approach so that we can build around a 20K system. It’s not just a BOP. This is an integration of whole system.”
From an operational standpoint, once the system is installed, one of the biggest challenges is running the BOP and managing emergency disconnect situations. The hook load, which is typically 2.5 million lbs, may be an issue when running and pulling the riser and may limit water depth capabilities, Mr Buisine explained. Furhter, the riser flange tensile capacity is typically 3.5 million lb and will impact tensioner setting and, therefore, water depth capability and mud weight. “We have to either minimize the maximum mud weight in the riser or minimize the water depth.”
Project 20K is a trademark of BP.