The modern era of drilling using coiled tubing began in the early 1990's and was made possible by the development of enabling technologies such as slim-hole drilling tools, improvements in tubing metallurgy and horizontal drilling techniques. The industry has recognised that coiled tubing drilling is most applicable for underbalanced drilling, re-entry drilling and through tubing re-entry drilling. Most coiled tubing drilling jobs have been completed using conventional or slightly modified coiled tubing units. A number of hybrid units have been built that incorporate conventional coiled tubing technology with conventional hydraulic jack systems for jointed pipe handling. At the same time as interest in coiled tubing drilling has grown, the interest in slim-hole drilling has waned as the industry recognised that although there was a need for fit for purpose slimhole drilling units, the capital to build the units was not available. This paper describes a unique rig concept that has been designed specifically for coiled tubing drilling and slim-hole drilling applications using jointed pipe.
The use of coiled tubing for drilling applications is a new phenomenon made possible by the development of a number of enabling technologies associated with both the coiled tubing and drilling processes. These enabling technologies include improved metallurgy and sizes of coiled tubing, enhanced tubing monitoring systems, reliable slim-hole drilling systems including slim-hole MWD technologies, window cutting systems for slim-hole applications among others. In addition there is an increasing business imperative to maximise recoveries from existing assets and to develop technologies that will make marginal fields economic.