Page 20 - Offshore Well Construction

CHAPTER 16
Technical Limit Drilling
Petroleum Extension-The University of Texas at Austin

INTRODUCTION
Technical limit drilling is a performance improvement process that advocates the pursuit of sound engineering and
proper planning to both the onshore planning and offshore execution phases of well construction.
It is nothing new and is certainly not rocket science. It was first called technical limit by Woodside, operating on the
northwest shelf of Australia in the early 1990s. This was based on the improvements that Unocal, Thailand achieved
in the late 1980s and early 1990s. Since then Shell has adopted a similar principle and called it drilling the limit (DTL)
and Amerada Hess called it to the limit (T L).
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The technical limit philosophy is based around two questions relating to performance.
• Where are we now?
• What is possible?

Where Are We Now?
This question can be answered by reviewing past performance or historical data.

Essentially it involves breaking the well down into discrete phases and identifying the conventional lost time or downtime
that has occurred. This data can then be reviewed and steps taken to prevent this downtime from occurring again.

Examples of this include:
• Determining the root cause of hole instability on directional wells.
• Running vibration subs to eliminate downhole vibration that was responsible for multiple twistoffs.
• Utilizing a hydraulic swivel packing instead of a conventional swivel packing to eliminate rig downtime.

What Is Possible?
Once the current level of performance has been established, the question then becomes one of where could our level
of performance go or what is possible?

This is a two-stage process that first challenges existing practices (that’s the way we’ve always done it, is no longer an
acceptable answer) and secondly starts asking, what if?
Challenging existing practice focuses on what is known as invisible lost time (ILT). ILT is time that is not classed as
downtime, but is time that is nevertheless not productive or is inefficient.

Examples of this include:
• Slow ROP
• Excessive connection time caused by outdated practices

Asking what if focuses on enhancements to equipment or identifies new technology that will improve the overall time
taken to perform a specific operation.

Examples of this include:
• Rotary steerable tools
• Multilaterals
• Dual activity derricks