Harnessing flare gas to generate power for offshore microgrid

For a major oil and gas company who is consistently engaged in the exploration and production of oil and gas offshore – a constant supply of power is simply compulsory.

Without it, production efficiency would plummet, causing profits to be affected, putting annual projections at risk.

The customer’s offshore platforms’ power requirements were fulfilled primarily by a subsea grid network. The grid connects to a 42 MW gas power station on a nearby island. This grid is responsible for supplying power to a cluster of 30 offshore platforms via a network of subsea power cables and for facilities on the island itself.

However, the offshore subsea grid network suffers from baseload issues where additional power must be supplied to the grid. The customer subsequently issued a public tender for engineered power solutions to resolve the baseload requirements of its offshore component of the microgrid.

It was revealed that the customer had a substantial amount of stranded gas, produced as a by-product during the drilling process. Collected and stored in pressure tanks vessels, the conventional process was to flare it.

Our experts saw this as an excellent opportunity and devised a proposition that could resolve baseload issues and reduce the cost of energy, while decarbonising its operations. A ‘rig-safe’ turnkey gas power solution with end-to-end gas engineering, which harnesses otherwise wasted flare gas to generate power was proposed:

• A gas sampling assessment by our technical team revealed that the gas had high sulphur levels with lower methane index of 53.4 with fluctuations in composition and quality of gas being expected.
• This key obstacle on harnessing flare gas for power was resolved by our experienced gas engineering expertise. Gas filters capable of stripping the flare gas of its impurities were integrated onto the generators.
• The inlet gas temperature was very high, at 70℃. These conditions weren’t ideal. However, with our expertise and equipment, our gas generators were able to utilise the gas.
• By establishing an estimate of flare gas volume to generate power, along with technical evaluation of the entire rig’s power load and synchronisation demands with existing power system, 4 MW of gas power generation was sized for the solution, with a built-in redundancy component.

A 6.3 MVA transformer package was also included as part of the solution Our experts designed and engineered a gas train and scrubber as part of the efficient package. Safety is paramount to everything we do, so fire and gas detection systems were installed and interfaced with the onboard ESD system.

With its high de-rate levels allowing it to work in harsh conditions, and its high efficient lean-burn technology that can reach full load in as little as two minutes, our gas generators were a great solution for the customer’s flare gas. Equipped with a gas filter and its high tolerance for methane, this meant the customer’s flare gas could be repurposed even with the levels of impurities it contained. Five gas generators were deployed to the customer’s offshore platform.

Our expertise was also harnessed for the design, supply and fabrication of gas connections. By using their flare gas to generate power offshore, power was supplemented to the mini-grid where it resolved the baseload issues, which is pivotal production continuity for its offshore operations.

Besides providing sustainable solutions, Aggreko also had on-site maintenance personnel to provide efficient and effective expertise whenever necessary.

Resolving baseload issues of the mini-grid allowed for consistent and high-quality power. This meant high productivity and efficiency for our client, eradicating the potential for drilling system breakdowns due to unstable power. This will lead to minimising production loss.

The daily 0.5mmscfd of APG used to generate power, which would otherwise be flared, was effectively repurposed and also reduced the emissions produced by the operations.