Abstract
Conventional drilling methods have been plagued with huge operational and financial challenges, such as cost of purchasing, inspecting, handling, transporting the drill equipment and most importantly, tripping in-and-out of the drill string whenever the Bottom Hole Assembly (BHA) needs a replacement, needs of wiper trip or when total depth is reached. The tripping in-and-out of the drill string not only contributes to Non Productive Time (NPT) but also leads to well control difficulties including wellbore instability and lost circulation. All this has led Oil and Gas industry, as well as any other engineering industry, to seek for new ways and methods in order to reduce these problems. Thanks to the advances in technical solutions and constant improvements of conventional drilling methods, a new drilling method - casing while drilling has been developed. Casing Drilling encompasses the process of simultaneously drilling and casing a well, using the active casing and thus optimizes the production. This paper presents a review of casing while drilling method (CwD) and its practical usage in drilling wells. The comparison of conventional drilling method and casing while drilling is also presented. The CwD method achieves significantly better results than conventional drilling method.
Highlights
Pavković B., Bizjak R., Pretrović B.In the late 1990s, the idea of casing while drilling has been accepted in O&G industry
The tripping of the drill string contributes to non-productive time (NPT) and leads to well control difficulties such as wellbore instability and lost circulation
One of the Tesco Casing Drilling rig were designed on standard oilfield skids, so the entire rig can be moved in 12 loads, rather than the 23 loads required for conventional rigs
Summary
The tripping of the drill string contributes to non-productive time (NPT) and leads to well control difficulties such as wellbore instability and lost circulation. Since these problems had to be solved there was a need for a new method - casing while drilling (CwD) - to address these issues (Abubakar et al 2012). It still has not been accepted very well, this patent had numerous advantages Some of those advantages were: elimination of drill pipe, reductions in overall drilling time, stuck pipe, crew and drilling costs; application of few casing string, decrease in accident occurrence on the rig and the ability to drill every foot in the well.
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