October 02 2018 0Comment

Workability of offshore operations

This blog post is part of a series of posts covering workability of offshore operations, and the role of decision support software such as MO4. The first post deals with the definition of workability and how it is determined.

Any operation taking place offshore is limited by environmental influences, most commonly a combination of wind, waves and current. Some operations can also be limited by visibility, heavy rainfall, hail or other types of weather. Once one of these environmental aspects is sufficiently strong that it can harm the well being of the personnel, or jeopardize the equipment or product dealt with, the operations must be halted.

Various reasons cause a grey area to be present between being able to work safely and when to stop. Decision making is a delicate process, as most operations take multiple hours to be completed and numerous complex steps are involved. More often than not it is impossible to abandon an operation once it has commenced—whenever it is possible it is costly and undesirably. Furthermore, the question of when an operation is no longer safe is not a binary one.

Environmental limits are determined with due engineering—simulations of the operation in various wave, wind and current conditions are performed, analyzed and reported. Unfortunately, this is done months before the actual operation, leading to a large number of assumptions. Engineers will always choose the worst-case (conservative) assumption. Conservative assumption stacked on conservative assumption causes a snow-balling effect of margins. More so, the results of the analysis have to be strongly simplified in order to be usable. Complex sea states and ship motions are reduced to a single parameter; significant wave height, even though the heading of the vessel and the wave periods are more decisive. A small swell can cause such large roll motions that an operation cannot take place, even though it is often neglected in engineering.

MO4 attempts to reduce the performance gap by including an automated part of the engineering into the planning. It also combines all forecasts and measurements of environment and ship motions in one central location, making it straight-forward to detect trends in the weather.