This paper will identify the increasingly stringent requirements of bit and mill design associated with small holes (particularly <3½") for use with coiled tubing. Recommendations are made on the correct slim hole bit/mill design to use when drilling a variety of different targets. In essence, this paper will show that as the bit/mill size decreases, the bit/mill choice becomes driven more by coil and downhole motor considerations; as the bit size increases, the bit choice becomes driven more by the properties of the target to be drilled.

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