Metal-to-metal completion technology

Metalmorphology is the process of shaping metal downhole to provide a metal-to-metal, gas-tight seal for the life of the well. Photos from Meta.

Well integrity has been defined by a reactive approach and the limitations of current well planning and intervention technologies. Mark Rivenbark looks at an alternative approach.

One of the biggest issues facing the offshore oil and gas sector today is well integrity.

This challenge was made apparent by a study conducted on a number of wells on the Norwegian Continental Shelf by Norway’s Petroleum Safety Authority (PSA), which found that every fifth well analyzed had well integrity weaknesses.

Regulatory requirements, in the North Sea and Gulf of Mexico in particular, are increasing the onus on operators to establish structural integrity and contingencies at the planning stage; recomplete existing producing wells to comply with new legislation; ensure that well integrity is not compromised by trouble zones and stuck casing; and reinstate well integrity quickly when damage does occur.

Despite the growing importance of well integrity – particularly since Macondo – questions still remain as to well integrity’s role in the well’s lifecycle. Questions include: What exactly is well integrity and when does it start in the well lifecycle? Is it possible to protect it and at what stage? And how can a safe and effective balance be found between protecting well integrity while maximizing production?

Robust well integrity

Sadly, many older wells were not designed for long life, so in some ways they were destined for early failure from the outset. Well life cycles of 30-50 years are what is needed in many producing fields around the world. These life cycles are achievable. Many studies based on statistical data have been conducted over the years in an effort to understand the causes of casing failure and possible solutions. This has involved the study of large data sets gathered over many years of production.

For external corrosion of wellbore casing and strings, caused by corrosive aquifers, for example, protective coatings, thicker casing and cementing all strings to surface are just some of the tactics that have been used to combat the attacks on the integrity of well bores. The loss of production inflicted on operators by the corrosion of casing strings is indeed substantial and in fact is growing every year. This can even lead to the loss of the well and/or damage to the reservoir. Some operators have reported well failures in as little as two years from the start of production of a well.

Many operators have carried out a detailed risk analysis of their well stock in an effort to rank each well from good to bad. This type of risk analysis is only as good as the data available for review and evaluation. Designing a robust, database-driven, analytical tool is a first step in risk ranking of a given well stock. Factors to be part of the database includes well construction types, annulus pressure, production data and well intervention information just to name a few of the parameters to investigate.

A system designed to monitor and manage well integrity should at a minimum set out clear standards to ascertain the integrity of the wells under management for their entire life cycle. This would include safe and continuous functionality aimed at meeting required production targets. In light of past well integrity lapses, some of which have resulted in loss of life and environmental and economic damage, a robust well integrity management system is a requirement for any operator interested in being a good corporate citizen.

The limitations of existing isolation technology

Liner tieback – The durability of the metal-to-metal seal enables the liner tieback to operate at high pressures and temperatures, making it ideal for deepwater challenges. Photo from Meta.

While technologies, such as inflatables, swellables and mechanical packers, have played a key role in securing well integrity and zonal isolation in the past, they do come with limitations. Swellables in particular are relatively inexpensive and easy to install without compromising casing strength, and yet come with reliability issues relating to the polymer swelling, the size of the diameter changes, structural integrity issues from other fluids, and the time it takes to swell, which can sometimes be up to 30 days. These technologies have an important role to play in isolation, but there is a need for other technologies to harness their benefits while overcoming their weaknesses.

Metal-to-metal

Meta has Metalmorphology for this area. Metalmorphology uses established metal working principles to shape metal down- hole to deliver a gas tight and durable metal-to-metal seal.

The technology balances the mechani- cal strength of steel with its elastic properties to create isolation solutions that instantly morph together to provide 100% conformance within the wellbore or casing. It provides a morphing ratio up to 60%, an axial load bearing rating up to six million lbs, and a sealing rating of up to 15,000psi.

The result is a gas-tight, axial load bearing, metal-to-metal sealing solution, which meets well integrity legislation as well as giving operators absolute confi- dence in their isolation and well integrity solutions.

Delivering tieback integrity in the North Sea

A Meta liner tieback, which uses Metalmorphology metal-to-metal morphing technology, was recently installed by a North Sea operator.

By morphing metal, the Meta liner tieback connects the liner to a tieback receptacle built into the previously run casing string. The result is a fully compliant V0 ISO14310 certified metal- to-metal connection with no reduction in internal diameter (ID) and no reliance on elastomers, capable of offering full integrity for the lifetime of the well.

The durability of the metal-to-metal seal enables the liner tieback to operate at pressures of up to 13,500psi at temperatures of 320°F and with an axial load bearing capability of up to six million lbs, making it ideal for deepwater challenges. It can be installed faster than other methods.

The Meta liner tieback connects the liner to a tieback receptacle built into the previously run casing string. Photo from Meta.

On the North Sea application, the field came with drilling and well architecture challenges that were preventing comple- tions. One particular challenge was equivalent circulating density (ECD), which can lead to wellbore instability. The operator needed a strong liner tieback interface with no reduction in ID and the ability to avoid tying liners back to the surface for as long as possible. The liner tieback was installed on a 9-5/8in. liner, allowing the operator to drill multiple sections below, while keeping the 13-5/8in. casing above the liner open for as long as possible.

Meta successfully ran the liner tieback to 3000m depth. It was deployed through a 65° build section and successfully set in 15ppg oil-based muds and at 70°C. The result was a life of well, gas-tight connection that extends the envelope for well construction and delivers tieback integrity over the lifetime of the well. The operator benefitted from improved control over the well, reduced rig costs and non-productive time, faster drilling and earlier revenue, and profitable and productive wells for the life of the field.

Strengthening well architecture in the Gulf of Mexico

A series of Meta tieback systems are due to be installed in a deepwater Gulf of Mexico field. The operating temperature will be 120°C and, once the tieback is installed, the deployment depth 10,000ft. Hydrostatic pressure at this depth will be 3750-5800psi, depending on fluid in the well.

Through the incorporation of the liner tieback into its’ well architecture, the operator will ensure that the company remains fully compliant with current regulations; overcomes limited IDs in casing strings to achieve high load bearing capabilities; allows asset teams to plan for drilling deeper; and provides flexibility of space out.

Conclusion

For too long, well integrity has been defined by a reactive approach and the limitations of current well planning and intervention technologies. Metalmorphology is providing a new way of working.

Mark Rivenbark is VP Global Sales at Meta. He has over 25 years’ experience in the oil and gas industry, having begun his career on Alaska’s North Slope as a completions engineer. Rivenbark previously worked for Dresser Industries, Halliburton, and Enventure Global Technology in various sales, technical, and management positions. He majored in applied science at the University of Alaska-Anchorage with an emphasis on metallurgy. He earned an MBA from the University of Liverpool.