The Effect of Steady Currents in Weather Downtime Assessment

Abstract

Abstract Weather downtime is a major factor in any offshore operation as it affects both the project program and budget. Therefore, knowledge of potential weather downtime for a given site is valuable to de-risk the project by improved planning and estimates of the financial performance. Severe sea states limit the allowable operational time offshore, thus extending the time required to complete the project. The metocean parameters used to estimate the weather impact on offshore operations are usually wind speed, significant wave height and wave period. However, steady currents may significantly impact the project, even during workable sea state conditions. This can especially be the case in offshore windfarms construction as they are often located in shallow water areas with high currents making it crucial to understand their effects on the weather downtime. In this paper we discuss how the effect of the currents may be more realistically accounted for in weather downtime estimations by considering the “waiting on current periods”, or the time the construction vessel will have to cease the operations due to periods of peak currents within an otherwise workable weather window. To understand this effect, we have developed a tool known as “GDG-WDAT” which is capable of interacting with the ERA5 database, enabling effective operational planning and cost savings in offshore operations.