Monodiameter drilling

The tapered design of conventional wells is as old as the oil and gas industry itself. And despite its refinement over all that time, it still has some fundamental limitations.

Designing a well involves detailed engineering to make sure that the progressively narrowing diameter is still sufficiently wide when it reaches the reservoir to enable economic production rates.

Unexpected encounters with unstable formations can require an additional string of steel pipe, reducing the final hole size though the reservoir and restricting the production from the well or even preventing the well from reaching the target depth.

Bringing new technology on stream

A monodiameter well with a single, fixed diameter from the surface all the way to the reservoir could overcome these constraints, enabling access to vast oil and gas reserves that are currently beyond our reach.

Not only that, a monodiameter well would require less rock to be drilled, and would have a smaller surface footprint – reducing the environmental impact of drilling overall.

Until recently though, monodiameter wells were an idea that had been too complicated to put into practice.

However, in a successful trial of pioneering pipe expansion technology in Pinedale, Wyoming, a team of Shell engineers have installed two consecutive casing sections of the same diameter in a live well under harsh conditions.

So how does it work?

Each time a new section of a well is drilled, a specially-designed liner is inserted to reinforce the hole.

These innovative liners are the result of extensive research and development. Shell R&D engineers have worked closely with experts from the steel industry to ensure they are optimised both for their expansion properties and strength.

Once this liner is at target depth in the well, it is mechanically expanded by pulling through a steel cone, using a unique Top Anchor and Pull expansion assembly.

After one liner has been successfully installed, we are able to drill the next hole section. This, in turn, is secured by inserting an identical liner through the already expanded section, and then expanding it to match the diameter of the previous liner.

We can repeat this process as many times as we need to in order to reach target oil and gas reserves.

Shell innovation

It’s not only the expandable liners that Shell has pioneered.

The Top Anchor and Pull expansion assembly is the result of years of innovation. Its cone is carefully designed so that, during expansion, it maintains the integrity of the threaded liner connections that are used to join each 40ft section. Its design also minimises pipe coating debris accumulating at the expansion face.

We have even developed a brand new pipe coating to lubricate the expansion process under the extreme conditions in the overlap section, and an alternative pipe connection protection system.

The result is a ground-breaking system that we can rely on to create monodiameter wells safely, wherever we need them.

The future of drilling?

With field tests currently underway, the big prize is successfully constructing complete monodiameter wells in the deep waters of the Gulf of Mexico.

There, we hope to bring remote and partially-depleted fields on stream – potentially unlocking millions more barrels of oil to help meet the world’s energy needs.

And we hope to be able to realise the many environmental and cost benefits of this new technology too.

Altogether, an incredible achievement for a talented and dedicated Shell team.