Coiled Tubing Drilling (CTD) has been used effectively for over 20 years in the oil industry and the technology has been evolving in order to meet changing industry demands. CTD takes the well-established concept of Coiled tubing and combines it with directional drilling using a mud motor to create a system for drilling reservoirs. Bottom hole assemblies (BHAs) are now able to drill directional, S-curve and horizontal wells and can be the key to unlocking reserves in mature oilfields via re-entry drilling. Coiled tubing drilling is known for its speed and ability to drill reservoirs in an underbalanced condition and CTD can reduce drilling times between 30%-60% compared with conventional jointed pipe drilling rigs. Therefore CTD can provide significant economic benefits.
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Underbalanced Conditions
Underbalanced drilling is the main advantage of Coiled Tubing Drilling (CTD) that jointed pipe drilling cannot easily replicate. CTD allows for continuous drilling and pumping and can increase the rate of penetration (ROP).
Speed of Operation
The second advantage of CTD is its ability to drill at high ROPs with increased time with the bit on bottom. This is made possible as operations do not need to stop to make and break connections. This can provide significant cost savings and both drilling time and rig-up time are far quicker with CTD, decreasing costs and increasing the rate of return.
Safety
CTD operations compare favourably to jointed pipe drilling as fewer rig hands are required on the rig floor.
Lower Environmental Impact
An additional advantage is the environmental impact of CTD. The well footprint, human interaction, discharges and noise pollution are greatly reduced by using CTD. Multiple wells can also be drilled from the same pad utilising a directional BHA and therefore CTD offers a more sustainable and lower impact method of drilling.
Operations
CTD has been used across the world in regions such as Alaska, US, Canada and the United Arab Emirates. Typical applications include depleted wells, unconventional gas shale, underground coal gasification and coal bed methane.