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Critical path concept is the key idea for a new drillship design

"Dual Activity Drillships Reduce Ultra-Deepwater Well Costs," by Larry McMahan and Forrest Estep, Petroleum Engineer International, April 1999, pp. 23-29.

"Project-management techniques improve dual-activity drillship operations" by Dean E. Gaddy, Oil & Gas Journal, Dec. 18, 2000, pp. 32-37.

Transocean Offshore, Inc. is a drilling contractor that has developed a new generation of deepwater drillships.  These are ships (835-ft long, in this case) for drilling petroleum exploration wells in deep oceans. Ships and drilling operations are very expensive, and the company targeted cost reduction in their new dynamically-positioned drillship design.

A "dual Activity Drilling Package" was conceived to attach the "flat times" that can consume up to 65% of the well construction. Normal drilling operations are bottlenecked by operations that occur through the rotary table (part of a drill rig).  That is, most all the critical path activities involve process with the rotary table.


The critical path is used to:


The most common way to shorten a construction project is to do more of the activities in parallel.  Transocean Offshore was able to do this by configuring the new drillship with a second complete drilling system.  While one system is drilling, the other can be making up stands of drillpipe, for example.

This design is a step improvement in functionality, made possible by applying smart project management thinking to the new drillship design. They estimate that time savings will be 15-25% for single wells and up to 40% for multiple wells.

I recommend reading this article if you are designing new equipment or processes that will be used in the projects your company performs.


—John Schuyler, May 1999.  Revised Dec. 2000

Copyright © 1999-2000 by John R. Schuyler. All rights reserved. Permission to copy with reproduction of this notice.