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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:

Define the tasks that must be accomplished to finish the project and in what sequence
Plan activities so that some can be done in parallel (consurrently).
Determine the shortest time in which the project can be completed.
Determine which activities constrain the project from finishing sooner (the sequence of these constraining activities is called the critical path)
Facilitate project plan optimization by evaluating whether to:
* schedule more activities in parallel so that the project finishes sooner;
* accelerate activities along the critical path so the project finishes sooner.

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