This paper describes the status of an ongoing project to both prove the feasibility of and provide a testbed for the development of processes and tools for drilling with coiled tubing. To date a total of three horizontal wells have been drilled in the Austin Chalk formation in Texas. These wells consisted of two 4 1/2" (114 mm) reentries in the Pearsall Field and one 5 1/2" (140 mm) reentry in the Austin Chalk near Bryan, Texas. To our knowledge these are the first horizontal wells to be drilled using coiled tubing.

These wells have been drilled using 2" (50.8 mm) coiled tubing with a 0.156" (3.96 mm) nominal wall, downhole mud motors, wireline steering tools and downhole mechanical orienting tools. The coiled tubing had a 5/16" (7.9 mm) single conductor wire installed inside it to allow the use of conventional wireline steering tools. The tools and techniques developed during this project and the advantages, limitations and future potential for this type of drilling operation are the subject of this paper.

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