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The general focus in environmental evaluation of offshore drilling is the discharge of cuttings and chemicals to local marine environment, in some cases including emissions to air from offshore turbines and engines. However, significant impacts occur as a result of processes upstream and downstream from drilling operations, in the manufacture of chemicals and materials, in supply and transport operations, and in treatment of drilling wastes. Life-cycle assessment (LCA) is the structuring, aggregation and evaluation of environmental impacts in a cradle-to-grave scope. We present an LCA model developed through a series of case studies for offshore drilling operations. Model components include a fleet of drilling rigs and supply vessels, a library of drilling fluids and chemical products, various cuttings treatment technologies, top-hole abatement techniques and well operations. The LCA model is used to evaluate technologies in historical, current and future best practice for offshore drilling. One measure under evaluation for the future is the development of smaller, fit-for-purpose vessels (Cat B), which are shown to potentially reduce emissions from the drilling vessel itself by 50 %. Slim-hole drilling is another technology with several potential benefits, including time savings, reductions in steel and concrete in installing and cementing casings, less drilling fluid required, and less cuttings waste logistics and treatment. In all, these provide 30-50 % reduction when compared with conventional well designs, in greenhouse gas emissions and other air emissions, and in harmful releases from manufacture of materials and chemicals and treatment of wastes. Relevant for operations outside European waters, the LCA shows that production and waste treatment of drilling fluid may pose a significant source for impacts unless fluids are managed properly by reuse of drilling fluid and recycling of oil from cuttings waste. These measures provide a reduction of 30 % of the total environmental footprint, illustrating the benefits from current best practice.

Future energy scenarios include both green and blue hydrogen, as both are needed to scale up decarbonized energy supply. A transition to renewable energy is predicted over time, but the urgency we are facing cannot be met by renewable energy alone. For blue hydrogen production, the overall greenhouse gas (GHG) emissions are primarily affected by emissions from natural gas production, processing, and transport (CO 2 and methane), as well as process efficiency and carbon capture ratio. Few complete and updated analyses are available that cover the entire blue hydrogen value chain with the best available technology for process facilities, as well as the proper design, operation, and maintenance of all relevant systems and infrastructure. This paper analyses the GHG intensity of blue hydrogen, using recent data as well as input from technology providers on state-of-the-art gas reforming technologies. Data are primarily based on natural gas production and transport in the North Sea Basin, with gas export from the Norwegian continental shelf to continental Europe or the United Kingdom, and with blue hydrogen production either in Norway or near pipeline landfall in the European Union or United Kingdom. Some data related to potential blue hydrogen production in the US Appalachian region are also given. The data show that the properly designed and operated value chains for blue hydrogen supply, with minimal emissions from natural gas supply and high carbon capture in hydrogen production, will give a major reduction in GHG emissions from energy end-use. GHG footprint for end-users based on blue hydrogen will typically be 80%-90% lower than for direct supply and use of natural gas.

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Today gas turbines and combined cycle power plants play an important role in power generation and in the light of increasing energy demand, their role is expected to grow alongside renewables. In addition, the volatility of renewables in generating and dispatching power entails a new focus on electricity security. This reinforces the importance of gas turbines in guaranteeing grid reliability by compensating for the intermittency of renewables. In order to achieve the Paris Agreement’s goals, power generation must be decarbonized. This is where hydrogen produced from renewables or with CCS (Carbon Capture and Storage) comes into play, allowing totally CO2-free combustion. Hydrogen features the unique capability to store energy for medium to long storage cycles and hence could be used to alleviate seasonal variations of renewable power generation. The importance of hydrogen for future power generation is expected to increase due to several factors: the push for CO2-free energy production is calling for various options, all resulting in the necessity of a broader fuel flexibility, in particular accommodating hydrogen as a future fuel feeding gas turbines and combined cycle power plants. Hydrogen from methane reforming is pursued, with particular interest within energy scenarios linked with carbon capture and storage, while the increased share of renewables requires the storage of energy for which hydrogen is the best candidate. Compared to natural gas the main challenge of hydrogen combustion is its increased reactivity resulting in a decrease of engine performance for conventional premix combustion systems. The sequential combustion technology used within Ansaldo Energia’s GT36 and GT26 gas turbines provides for extra freedom in optimizing the operation concept. This sequential combustion technology enables low emission combustion at high temperatures with particularly high fuel flexibility thanks to the complementarity between its first stage, stabilized by flame propagation and its second (sequential) stage, stabilized by auto-ignition. With this concept, gas turbines are envisaged to be able to provide reliable, dispatchable, CO2-free electric power. In this paper, an overview of hydrogen production (grey, blue, and green hydrogen), transport and storage are presented targeting a CO2-free energy system based on gas turbines. A detailed description of the test infrastructure, handling of highly reactive fuels is given with specific aspects of the large amounts of hydrogen used for the full engine pressure tests. Based on the results discussed at last year’s Turbo Expo (Bothien et al. GT2019-90798), further high pressure test results are reported, demonstrating how sequential combustion with novel operational concepts is able to achieve the lowest emissions, highest fuel and operational flexibility, for very high combustor exit temperatures (H-class) with unprecedented hydrogen contents.