The Analysis and Application of Salvage Method for the Fallen PDC Bit

With the wide application of PDC bit, facing with many complicated drilling problem, the drill bit falling accident is particularly serious, so it is very urgent to find a salvage method that can ensure the success rate of PDC bit salvage. This paper proposes two-drill salvage technology, which is especially suitable for the fallen drill bit in skew in the wellbore, which significantly improves the success rate of salvage; besides the paper has deeply analyzed the salvage method of the fallen drill bit to clear that the traditional mill and tap salvage method is effective for the conventional fallen drill bit. Firstly, the guiding shoe adjusts and guides the crooked drill bit to the middle of the well bore, mainly by rotating to drive the drill bit and improve the success rate of catching fallen drill bit; secondly, the improved salvage tool takes the fallen drill bit out. By using this technique, the fallen PDC bit of an oil well in Bohai sea area was successfully recovered. Practice indicates that the two-drill salvage technology can ensure the success rate of PDC bit salvage, and obviously shorten the operation period and reduce the cost, besides the successful salvage work for the fallen PDC bit will provide reference for the follow-up drilling work.