🔍 Key Concepts

• Roll period vs. roll angle relationship for offshore platforms • Effect of water depth on motion characteristics of a jack-up or drilling unit • Practical range of roll periods for stable vs. uncomfortable vessel/platform motions

💭 Think About

• Which of these times would represent a very fast, uncomfortable ‘snappy’ roll versus a slower, more gentle motion for personnel going on location? • In 150 feet of water with only a 2° single-amplitude roll, would you expect the roll period to be extremely short, very long, or in a moderate range? • Compare the four options: which are clearly unrealistic for a large drilling unit’s roll period based on your knowledge of typical ship/platform motions?

✅ Before You Answer

• Eliminate any roll periods that are so short they are more typical of small boats in waves, not large drilling units. • Consider whether very long periods (over 10 seconds) are typical of large, slow-rolling ships or whether that would be excessive for a small 2° roll in 150 ft of water. • Focus on the option that represents a reasonable, moderate roll period for a stable platform with only 2° of single-amplitude roll.