Offshore wind energy generation and paleontology
With increased interest and investment in wind energy – especially as the U.S. considers leases in Federal Waters – it’s important to remember that geology and paleontology can play a big role. We hope to inspire architects, engineers, and the general public to research the influence geological and paleontological information can have on offshore facility design.
Offshore facility installations tend to be larger than their onshore equivalents. Wind turbines are no exception, as offshore turbines need to produce high wattage to offset a more costly installation. An offshore wind turbine installation can cost as much as $4 million per turbine. With that large of an investment, operators often want to understand the potential risks to their facilities and assess the design to withstand risks or potentially avoid certain risks.
Paleo for offshore facility risk assessment
Before any facility is installed, potential sites are risk-assessed by a team of experts usually led by a Geotechnical Engineer. Much of facility design relies on physical testing and classification of soil characteristics to arrive at foundation, slope stability, and settlement recommendations. Depending on the site (especially for larger facilities and those farther from shore) recurrence intervals (or return periods) of natural phenomena like faulting, landslides, floods, etc. are calculated to assess the probability of a magnitude event that the facility should be designed to withstand. An example of this would be a 1% probability of a certain natural occurrence, which is often termed a 100-year event.
In the offshore marine environment, these natural events tend to be wind, storm swells, submarine landslides, and fault movement in the subsurface, depending on the depth of anchors or footings. For large and costly investments, facilities may be designed for a 10,000-year event – an event that has a 1 in 10,000 chance of occurrence.
For a proper assessment, a record of 50,000 or 100,000 years can corroborate the recurrence of these 10,000-year events. The rock record preserves this evidence. The challenge is to place these events in the context of time. Radiocarbon dating techniques are often employed to create a time model. However, radiocarbon techniques are only relevant to 40-60,000 years in the past. For older time models, paleontology is employed.
Paleontology and Stable Isotope Stratigraphic – an alternative to radiogenic dating
Companies like Paleo Data Inc. examine rock samples for microscopic fossil content, searching for bioevents in the geologic past to put the events into context. This can all be done in an effective and cost-efficient manner.
Additionally, certain fossils preserve the chemical properties of the oceanic water at the time the fossil was buried in seafloor sediment. Chemical properties like δO18 and δC13 have been studied thoroughly across the globe and shown to be cyclical in the geologic record. These chemical signatures – termed Stable Isotope Stratigraphy – provide resolution of time in the context of paleontological bioevents (based on global research) that rivals radiogenic dating methods.
Past events and ocean chemistry recorded by microscopic fossils provide a time model in the calculation of recurrence intervals (or probabilities) for natural events. The recurrence of a magnitude threshold for these natural events effects the placement and design of any facility – including oil and gas installations and wind turbines – in the context of a risk-assessed geotechnical evaluation.
