A blueprint for sustainable offshore energy

By Stewart Maxwell, Aquaterra Energy

DeNovo’s Zandolie Field Development, offshore Trinidad & Tobago
DeNovo’s Zandolie Field Development, offshore Trinidad & Tobago (photo: DeNovo)

A pioneering 100% renewable offshore platform that reached first gas within a year of installation offers a blueprint for rapidly scaling up global offshore energy capacity while reducing the associated costs and carbon emissions.

The ground-breaking project harnessed a light, locally built renewably powered minimum facilities platform to produce up to 40 million cubic feet of gas a day. The Zandolie Field Development is DeNovo’s second offshore instalment and will provide the National Gas Company of Trinidad & Tobago with a stable supply of locally sourced natural gas.

As a lightweight, unmanned modular design that is locally made with a robust preventative maintenance strategy, it will dramatically reduce the cost and carbon emissions of manufacturing, transportation, installation, and maintenance. By sharing a pipeline and processing facility with DeNovo’s neighbouring Iguana gas field, it will also reduce the environmental impact of processing. As the platform is powered from solar and wind, it makes use of 100% renewable power sources, which translates to no direct CO2 emissions during normal operations.

Against the backdrop of a global energy crisis, the project offers a cleaner and more cost-effective way to scale up the world’s offshore energy capacity from oil and gas to offshore wind.

The Challenge: A low-cost, low-carbon route to rapid first gas
DeNovo faced the challenge of delivering rapid returns and reduced capex and opex while simultaneously reducing carbon emissions across the project lifecycle.

This involved the difficulty of producing a 100% renewably powered platform in a region with highly changeable weather conditions that created an energy intermittency risk. Developers also had to contend with the conflicting requirements of having a platform in 20 metres of water in an area with very high-seismic loads and minimising the carbon-intensive steel used in the platform.

Crucially, developers needed to find a lighter alternative to conventional jacketed structures so that the Zandolie field could be sustainably developed with existing local manufacturing facilities and installation vessels. Smarter and more streamlined maintenance was also essential to reducing lifecycle emissions.

The Solution: A circular economy of energy assets
Aquaterra Energy aims to drive a global circular economy of energy assets where existing platforms, logistics and fabrication facilities can be repurposed or re-used for new offshore energy production. The company has been pioneering the use of lightweight, low-carbon modular offshore energy platforms which can be rapidly deployed and scaled up using limited local resources.

Aquaterra Energy has recently completed the development of a lightweight Sea Swift unmanned platform that is enabling the Zandolie field to be sustainably developed at unprecedented speed – taking just 476,613 manhours of which 66% were local content hours. The platform is renewably self-powered, eliminating the need for traditional diesel generators or cables connecting to the grid. It can adapt to intermittency from local weather fluctuations by using a complimentary combination of wind and solar power alongside 4 days of extra storage capacity via batteries.

Its streamlined, slimline design uses approximately 30% less steel than conventional jacketed foundations, eliminating the need for larger installation vessels and reducing reliance on steel, which contributes 8% of global CO2 emissions. Engineers harnessed a novel steel bracing system support structure with legs locking monopiles together to withstand seismic activity without the need for a huge carbon-intensive steel platform on the seabed.

Aquaterra Energy has recently completed the development of a lightweight Sea Swift unmanned platform that is enabling the Zandolie field to be sustainably developed at unprecedented speed
Aquaterra Energy has recently completed the development of a lightweight Sea Swift unmanned platform that is enabling the Zandolie field to be sustainably developed at unprecedented speed (photo: DeNovo)

The project’s modular design means it can be transported in prefabricated parts and assembled on-site like industrial-scale Lego. This means the new platform deck, subsea structure and conductor were all installed using the same local jack-up rig that drilled the well without the environmental impact of bringing in bigger vessels and cranes from outside the country. The modular design used can also be seamlessly scaled up without expensive, carbon-intensive replacement of existing infrastructure.

The “brains” of the platform is the modular deckhouse unit, which houses the main electrical equipment such as the control and shutdown system, wellhead control panel, communications, power distribution panels and solar panels. The modular design of this unit allowed over 90% of commissioning and function testing to be executed onshore in the fabrication yard, which significantly reduced offshore time, cost and associated CO2 emissions.

This simplified, streamlined design is entirely manufactured locally with existing infrastructure, boosting regional skills and employment while curbing manufacturing-phase emissions, in fact 56.4% was local content spend. A pipeline to the nearby Iguana field enables the platform to share processing facilities with the existing Iguana Platform, delivering further environmental efficiencies.

Intelligent monitoring and preventative maintenance enables the platform to operate unmanned and reduce average maintenance visits, significantly slashing operational expenditure and emissions across its lifecycle.

Results: A model for sustainably scaling offshore energy
Localisation and decarbonisation of the project from manufacturing to maintenance has improved both cost and carbon efficiency, demonstrating that sustainable offshore energy can boost both profit and planet. Platform visits have been cut in half when compared to routine visits to traditional platforms. Localising material sourcing, fabrication and installation is also providing and preserving vital skills for the region which will be vital for Trinidad & Tobago’s future energy independence.

The project also offers a potential blueprint for sustainable development of our abundant offshore energy resources through a circular economy of energy infrastructure continually reused for new projects. Similar lightweight, locally built platforms could dramatically reduce the combined capex, opex and carbon footprint of offshore oil and gas globally. The Sea Swift range of platforms can be seamlessly scaled up to produce from one up to 9 conductors without increasing installation costs and emissions.

Lightweight, locally built platforms could also provide substations for offshore wind projects that can be installed with existing jack-up rigs, reducing the cost and environmental impact of installation. We could see a cross-sector circular economy of energy assets where oil and gas infrastructure is repurposed to help sustainably scale up offshore wind capacity in line with climate targets.

Ultimately, this offers a template for achieving combined social, economic and environmental benefits across every aspect of offshore energy from design to decommissioning.

Stewart Maxwell, Technical Director at Aquaterra EnergyStewart Maxwell joined Aquaterra Energy as Technical Director in May 2013. In this role, he is responsible driving technical innovations across all parts of the business. Stewart also leads the Platforms solutions within Aquaterra Energy including the flagship Sea Swift and renewable-powered platforms.