Coiled Tubing Drilling (CTD) has been used on the North Slope of Alaska to drill in excess of 250 re-entry sidetrack wells since 1994. Most of the through tubing coil sidetracks were drilled with a conventional bottom hole assembly (BHA) consisting of a mud pulse MWD tool, and a mechanical/hydraulic orienter. Recently fifteen CTD sidetracks were drilled in Alaska using a BHA that communicates to and from the surface via an electric line in the coil.

Both the conventional mud pulse telemetry system and electric line BHA are described in this paper. However, the primary goal of this paper is to compare the actual performance of the electric line BHA to the conventional mud pulse tools. In addition to drilling rate, several other drilling parameters will be discussed. Time spent surveying, logging, drilling time, orienting, and BHA handling will be addressed. (Fig. 1)

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