Integrated Fishing and Reaming Technology for Downhole Large-Diameter Collapsed Objects

Fissured deep mudstone formation and fractured formation are prone to collapse during drilling, and the size of collapsed objects are large. Resistance is encountered while dealing with downhole large-diameter collapsed objects by using conventional methods such as “slug” sweep, and reaming with cone bit and reverse circulation junk basket. It is time consuming and seriously affects the drilling cost and benefit. Based on the analysis of the reasons why it is difficult and time consuming to handle large-diameter collapsed objects by conventional methods, a drilling tool integrating breaking, reaming and fishing was developed. In addition, different parameters of reaming and fishing, and techniques for removing collapsed objects were adopted according to downhole conditions. Therefore, an integrated processing technology of fishing and reaming for downhole large-diameter collapsed objects was formed. The technology was applied in 12 wells encountering resistance adopted reaming due to downhole collapse, and achieved a 100% success rate in reaming and fishing. The results suggested that this technology could bring about integrated reaming and fishing for large-diameter collapsed objects in downhole hard-brittle mudstone. Further, this process had a positive effect on the quick treatment of large-diameter collapsed objects in downhole hard-brittle mudstone, and could effectively reduce the time for handling downhole failures.