There are many reasons why you would want to drill using Underbalanced Coiled Tubing Drilling (UBCTD). Not only do you have the advantages of underbalanced drilling, such as maximised well productivity and increased ROP, but you also get the advantages of working with CTD where you get continuous underbalance, fast rig up, small footprint and high build rates. However, even with many advantages, UBCTD has a specific range of applications that it is suitable for. Outside this range, it will be ineffective or completely unsuitable.

The key to every UBCTD project is that there is a well-defined reason for using the technology. A focus on the specific value to be gained from the technology keeps the engineering problem constrained within narrow limits so that the return on investment can be maximised. Other secondary benefits will still be captured from UBCTD but they will naturally develop as the planning and execution progress.

When assessing your well candidates consider the ways in which UBCTD could revolutionise your well designs and therefore your return on investment. Finally, here are a few example questions to ask yourself during the process (there are many more, of course):

• Is the reservoir sensitive to formation damage? UBCTD could increase production more than 3x compared to overbalanced drilling.
• Could high build rates remove a casing string or liner from the well design?
• Could you save cost by utilising a smaller pad or by using access roads already suitable for a CT unit but not a rig?

More to follow in my next blog…

Author: Adam Miszewski

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