Deep Penetration—Rotary Drilling and Sampling through a Drill String

4 Deep Penetration—Rotary Drilling and Sampling through a Drill String 5.2.4.J Introduction 

Second, because the drill string cannot withstand much lateral movement, the ship typically is anchored, usually four points if in shallow water. If the ship is in deeper water, it must be dynamically positioned. 

Ferder. (From Andresen, A. et al.. Marine Geotechnol, 3,201-266,1979. Reprinted with permission of Taylor Francis Group.) 

The drill rig with all its components is an integral part of the ship. This vessel may be dynamically positioned over a site or anchored with up to three bows and three stem anchors. The use of a bow thruster enables anchoring without the assistance of another boat. The drill string will always be motion (heave) compensated. Heave compensation is a method employed offshore to minimize the effect of waves on the drilling and sampling process. A more thorough discussion of heave compensation will be presented in Section 5.2 A A. The second type. North Sea Type—Portable, has a portable heave-compensated 

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