Using Casing as the drillstring has a number of applications ranging from very soft surface hole formations to deep production casing strings. Drilling with casing has been performed in excess of 400 wells worldwide. Utilizing a drillable drill bit attached to the bottom of the casing has proven to be a very simple technique with a growing range of applications. The result has been significant reductions in flat time and more efficient wellbore construction. As drilling efficiency increases in a number of areas, one area little affected has been the reduction of ‘flat time’. The method of drilling with casing significantly reduces operator flat time and streamlines the drilling process. This paper describes the system used to deliver flat time reductions while maintaining and even improving on bottom drilling efficiency. (figure 1)
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