It’s been a quarter of a century since Rotary Steerable Systems (RSS) displaced mud motors as the energy industry’s premium directional drilling tool of choice, and the basic design has incrementally been improved upon over the years.
But the fundamental approach has remained unchanged. The technical and commercial realities of today’s broad energy landscape – and the specific directional drilling market – demand that an alternative be added to the RSS roster. This article will explore why that need exists and how it can be met.
The energy industry of 2021 looks very different to anything that’s come before. With the energy transition as a backdrop, a lower-for-longer oil price environment has forced both operators and service companies to squeeze their operations for every ounce of efficiency they can.
The geography of the industry is changing too. The Middle East remains a juggernaut and the US shale strength continues but around the world operators are looking again at previously unattractive or uneconomic plays and re-evaluating their feasibility. To make these plays economic means keeping an iron grip on the cost per barrel.
In that respect, traditional pad-and-piston RSS designs can be frustrating. By nature of their design, they are prone to excessive wear which eventually inevitably entails downtime. In a competitive industry with downtime as a major performance metric, that’s not just frustrating – it’s damaging, both to reputation and the bottom line.
However, there is no avoiding it. Any system that steers by pushing a pad against the borehole wall is going to be subject to powerful forces, and if it’s not direct wear of the pads that causes the problem, it’s torsional vibration of the drill bit. Over the years, resourceful engineers have fine-tuned designs to reinforce the technology or reduce the effect of those forces, but it’s an unavoidable drawback of existing RSS systems. This is a potential cause of failure that can result in downtime at any moment, eroding already-thin margins.
At the same time, just as oil producers are keeping an eye on production cost per barrel, gas-focused producers are trying to manage cost per cubic foot. Touted as a ‘bridging fuel’ between the hydrocarbon-based old world and the renewable new one, demand for gas has seen sustained increases worldwide. Abundant supplies and the emergence of the US as an LNG super-exporter mean this has not translated into high prices however, and margins for gas production remain thin. In certain basins, such as Hainesville, gas producers must similarly look for a more reliable RSS option with the added difficulty that these are often in high-temperature environments, and traditional RSS designs aren’t necessarily designed to perform well in these circumstances.
What can be done though, if this is an unavoidable facet of RSS design? The answer is to take a new direction for directional drilling, omitting pads and pistons in favour of a simple, stronger collar, and decoupling the steering mechanism from damaging torsional vibration.
This is achieved by using internal hydraulic pressure differentials to create side-force at the bit for geo-steering, rather than pushing against the borehole wall to change direction. The approach uses Bernoulli’s principle of fluid dynamics, which can commonly be observed in the generation of lift force on hydrofoil, but which has not previously been applied to downhole applications.
The advantage of this approach is that, by internalising the steering mechanism, a completely plain collar design is possible while achieving true at-bit steering, decoupling the mechanism from torsional vibration, and removing any pads or external profusions that might be subject to excessive wear. Most of all though, the design is mechanically simpler – elegant, even – compared to anything possible with traditional RSS design, which increases reliability and therefore reduces downtime.
A different market landscape
It isn’t just the technology that has been overdue a shake-up when it comes to the RSS market though; the market itself has become (conversely) over-commoditised and under-competitive.
Taking the US as an example, there are a number of engineering firms offering RSS tools to the market, with high quality engineering honed over many years. The country’s backbone of independent service companies buy or lease RSS tools as necessary from these companies. However, the market lacks enough independent alternatives. To support a healthy ecosystem of independent service companies with genuine options to choose from, that must be rectified.
And that imperative is extending into new markets, too. In the Middle East, National Oil Corporations (NOCs) are looking to bolster local content and in-country manufacturing. Unlike traditional RSS tools, the independent status and simple engineering of an internally pressure-steered RSS allows for the majority of manufacture and repairs to be conducted in-country, in line with national strategies.
Around the world, independent service companies are underserved by independent RSS options. Giving them that independent alternative – an alternative that offers greater reliability and cost-efficiency – could be genuinely transformative for many: an internal pressure differential steered RSS could elevate many into a new league of contracts.
As lateral lengths increase across the industry, there is going to be demand for RSS tools that can achieve smoother bores with lower tortuosity.
In other words, there is ample room for an alternative to traditional RSS tools without having to rip up the rulebook and start again – the market functions best when it can choose from a range of technologies, from a range of suppliers, to best suit the job at hand. And that’s the new direction for directional drilling that needs to be taken.
Read the article online at: https://www.oilfieldtechnology.com/drilling-and-production/01072021/a-new-direction-for-directional-drilling/
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