Coiled tubing drilling has proven to be a valuable asset in petroleum recovery; however, the application of this technology has also posed its own unique challenges. One of the greatest challenges has been devising a way to orient downhole toolface without the ability to rotate the drillstring. The operation of the patented indexing tool described in this paper, only one of two currently available on the market, achieves toolface orientation by using available hydraulic forces already present during the drilling process: air, gas, or mud.
Actuation is achieved through a flow-operated orienter. The mud or other sources of hydraulic power drive a cam that rotates the toolface. The design of this tool also helps to ensure actuation accuracy by restricting drilling fluid flow until orientation is achieved. Flow will resume only when the toolface is in the correct position, thus reducing possible errors.
Successfully in use for five years on Alaska's North Slope, the indexing tool has a simple design and yet is durable enough to withstand downhole stresses and operate in virtually any environment. Technical and operational features, and the benefits of those features to drillers are discussed in detail in this paper. The indexing tool has also been used successfully as a coiled tubing fishing tool.
Its unique design and operation makes it a cost-effective technique in coiled tubing drilling and a unique achievement in downhole technology.