Forming metal downhole results in durable metal-to-metal connection
Richard Craig
Meta
There are few more high profile issues in the offshore oil and gas sector today than well integrity. Regulators are increasing scrutiny on offshore drilling and production operations. These range from the US Bureau of Safety & Environmental Enforcement through to the UK's Health & Safety Executive and Norway's Petroleum Safety Authority, among others.
Morgan Stanley predicts that 27 MMb/d of new production must come onstream over the next seven years to meet rising energy demand. Maximizing production and tapping into new offshore oil and gas frontier regions has never been more important. Increased regulatory scrutiny with its focus on well integrity, however, has led to an urgent need to find that balance between reducing risk in well operations while increasing production and well profitability.
Despite the growing importance of well integrity, questions remain about its role in a well's lifecycle. What exactly is well integrity and when does it start in the well lifecycle? Is it possible to protect it and at what stage? How can a safe and effective balance be found between protecting well integrity while maximizing production?
Current approaches
One common definition of well integrity today used worldwide comes from Standards Norway and its NORSOK D-010 standard, describing well integrity as the "application of technical, operational and organizational solutions to reduce risk of uncontrolled release of formation fluids throughout the life cycle of a well."
Too often today, this "application of technical, operational, and organizational solutions" takes place in a reactive manner where problems are dealt with and fixed after they occur and where the main focus remains well monitoring. This reactive approach can lead to drilling disruptions, rising costs, and ultimately lost production.
A new well integrity approach is required where well integrity is secured at the outset of the well design and drilling program, and where weak spots and trouble zones are tackled during well planning. This allows operators to build in contingencies, reduce risk, and protect and enhance future production. One technology enabling this proactive approach is Metalmorphology.
Metalmorphology is an established metal-working principle that balances the mechanical properties of steel with its geometric properties (diameter and wall thickness) to shape metal downhole.
Similar to hydroforming in the automotive industry, Metalmorphology forms metal through direct hydraulic fluid pressure in a downhole environment, resulting in a robust and durable metal-to-metal connection. The instant setting capabilities of the technology also create a seal that literally morphs together, conforming to the shape of the wellbore downhole.
Metalmorphology can be of benefit by removing any delays and uncertainties in using swellables, concerns about the reliability of perishable elastomer seals, and problems created with internal diameter (ID) restrictions.
The technology has high-pressure and axial loading capabilities and it also provides a permanent and gas tight, life-of-well solution.
Secondly, the fact that morphing takes place immediately and follows the well's contours with 100% conformance accelerates drilling and enables wells to be put into production more quickly. Swellables can take up to 30 days to swell and the further they expand in diameter, the more their sealing performance and structural integrity tends to reduce.
Finally, Metalmorphology has no ID reduction. It provides a full bore ID and a morphing ratio of up to 60%.
Well architecture
High quality well architecture and strong structural integrity are vital for the success and profitability of a well. Planned in from the design stage, a liner tieback system can help reduce well construction costs and improve well performance, and can be a tool for planning well architecture and structural integrity.
There is a need, for example, to overcome limited ID in casing strings through high load bearing capabilities, as well as a need for enhanced structural integrity for the well to allow drilling. An effective liner tieback has no weak points in the completions or casing string, and pre-empts unforeseen structural integrity issues.
Sometimes there is a need to avoid tying liners back to the surface for as long as possible during drilling so that wellbore and annulus diameters are maintained higher in the well and equivalent circulating density (ECD) pressures minimized.
Furthermore, pre-installing a durable liner tieback also allows for the seamless start-up of slot recovery operations at a time when the well needs a change of direction and the reservoir is being depleted, for example.
Finally, a strong and flexible liner tieback interface can also help operators recomplete existing producing wells to comply with new legislation with a minimum change to well architecture.
Meta's Metalmorphology-enabled V0 ISO14310 certified liner tieback system makes the connection by morphing the tieback casing into a tieback receptacle.
The result is fully compliant, life-of-well connection with no ID reductions and no perishable items such as elastomers. The durability of the metal-to-metal seal enables it to operate at pressures of up to 13,500 psi, installation depths of up to 30,000 ft, temperatures of over 160°C, and has full axial loading bearing capabilities of 6 million lbs.
The Meta Liner Tieback can install in one day as opposed to the typical five or more to save rig time.
North Sea field
The Metalmorphology-enabled liner tieback system is applicable in the face of complex well architectures.
One North Sea field, for example, had drilling and well architecture challenges that had the potential to prevent completions. Chief among these was ECD which can lead to wellbore instability. It was crucial to protect annular pressures as the well casing got smaller and to ensure that mud entered the wellbore.
The operator needed a strong liner tieback interface with no reduction in ID and that would ensure that wellbore and annulus diameters were maintained higher in the well and ECD pressures minimized.
Meta successfully ran its 95⁄8-in. liner tieback to a depth of 3,000 m (9,840 ft). The Meta Liner Tieback was deployed through a 65° build section and successfully set in 15 ppg oil-base muds) and at 70°C. Metalmorphology shaped the metal downhole to connect the liner to a tieback string of casing.
The solution allowed the operator to drill multiple sections below the 95⁄8-in. section while keeping the 135⁄8-in. casing above the liner open as long as possible, resulting in there no longer being a need to run the 95⁄8-in. surface casing string until after the lower completion was in place. The surface casing string also still ties in to the 95⁄8-in. liner with no loss of ID through the connection.
The result is a life-of-well V0, metal-to-metal, gas-tight, load-bearing connection that extends the envelope for well construction and delivers tieback integrity over the lifetime of the well.
In meeting the challenges of circulating pressures and maintaining wellbore and annulus diameters higher in the well, the operator improved control over the well to reduce rig costs and non-productive time, producing earlier revenue.
Regulatory requirements
The Metalmorphology-enabled liner tieback has another advantage. Its metal-to-metal morphing technology can help demonstrate compliance with regulations, especially in the Gulf of Mexico, where the technology meets and exceeds many of the required deepwater design parameters.
Recent regulations, for example, have made it necessary for GoM operators to alter well designs to strengthen well architectures, so as to demonstrate compliance with safety and environmental procedures.
With the Meta Liner Tieback, GoM operators can plan against worst case discharge scenarios; ensure that well integrity is fully compliant with BSEE; overcome limited IDs in casing strings to achieve high load bearing capabilities; and allow asset teams to plan for drilling deeper.
