Into the deep: electrifying subsea oil and gas operations
In some of the most challenging conditions found anywhere in the world, far offshore, and deep below the waves, Saft batteries deliver safe and reliable power for the new generation of electrified subsea oil and gas projects.
Even as the world pushes for renewable energy, the global demand for fossil fuels is still rising. And the forecasts are that this trend will continue until 2025 at least. Offshore oil and gas already play a very significant role, with subsea reserves currently accounting for around 30 percent of global oil and gas production. However, to maintain production, exploration projects now need to venture hundreds of kilometers from the nearest shore, and ever deeper below the surface. These projects can be ‘deep offshore’, classified by Total as meaning anything at depths of more than 500 meters and even ‘ultra-deep offshore’ at depths of more than 1,500 meters.
As the operating environment becomes more extreme, a growing number of subsea operators are embracing either partial or total electrification to help optimize costs and reduce their environmental impact. One specific aim is to reduce the use of hydraulic systems. That helps simplify the umbilicals between subsea production systems and processing units on floating or onshore facilities, because they only need to contain electrical power and communication circuits.
Electrically operated valves
An application where electrification is having a strong impact is the valves used in subsea control and production systems. Traditionally, these valves have been operated hydraulically. But a switch to either fully electric or hybrid operation offers significant benefits in terms of controllability, ease of automation and safety.
Saft was in the vanguard of this development. Over 10 years ago, our lithium-ion (Li-ion) rechargeable batteries were deployed to solve the problem of powering an innovative standalone subsea choke. This is a valve which controls the flow of oil or natural gas between wells and manifolds during seabed operations. Using electrical drives rather than hydraulics offers the advantages of faster and smoother response and real-time feedback on performance and valve position. It also eliminates the possible leakage of hydraulic fluid into the sea.
The challenge was to provide enough power to operate the choke at depths of up to 3,000 meters as it was not practical to run a subsea cable that could meet the high peak power demands. The Li-ion batteries close this power gap by storing enough power for a full opening or closing operation of the choke, a process which takes up to four and a half minutes.
The batteries support the choke’s daily duty, as well as operating several times a day in exceptional circumstances, throughout a 25-year design life.
Fully electric subsea production
In the future, larger equipment such as the compressors and pumps that are currently located on offshore platforms will be relocated on the seabed near the well to improve efficiency and reduce cost. In 2016, Total led the way by launching K5F, the world’s first all-electric subsea pilot well in the Dutch North Sea. The growth of subsea electrification will need backup batteries to ensure safe, reliable, uninterrupted operation. Saft Li-ion batteries, proven in the rigors of space flight, are ideally suited for this demanding environment.
Saft is a partner of TechnipFMC in providing subsea solutions to the oil and gas industry.
Going beneath the seabed
Below the seabed, Saft primary lithium batteries also power downhole applications, such as MWD (measurement while drilling) tools that incorporate a variety of electronic sensors. These tools provide real-time information about the depth and direction of the wellbore as well as the conditions at the drill bit. The onboard batteries must operate over a wide temperature range of -40°C to +150°C, while enduring high levels of shock and vibration. Most importantly, they must provide complete reliability for long periods – typically a few hours to over 20 years. This is especially important because, if the drill had to be brought back to the surface prematurely to replace a failed battery, it would cost tens of thousands of dollars in downtime.
Setting AUVs free from cables
Autonomous underwater vehicles (AUVs) and remotely operated vehicles (ROVs) are the workhorses of the oil and gas industry, especially as exploration reaches depths beyond the reach of divers. Not only are they getting smarter, with an ever-increasing array of onboard electronic sensors, they are also going untethered and free of umbilicals. That requires high capacity batteries capable of supplying more power in a compact, lightweight package. Saft Li-ion batteries are the perfect solution, with the added benefit of proven reliability and long life.
As oil and gas projects explore new horizons deep below the surface they demand more automation and more electrification. High-technology batteries will therefore play an increasingly vital role both for backup and primary power. What we have seen so far is just a drop in the ocean.