A method of casing drilling using a drill shoe which is drilled out once reaching the target depth rather than retrieved is well known. Casing-drilling shoes are typically constructed of non-ferrous metals in the form of solid body or steel body with extendable blades and an inner section constructed of a readily drillable material. Pilot tests of drill shoe design with extendable blades revealed the following disadvantages: undesired activation of drill shoe prior to dropping an activation ball, extendable blades dropping down from annular space to bottomhole, and poor strength of low temperature solder alloys for soldering of the cutters.
Experts of TatNIPIneft R&D Institute came up with the solution to use ferrous material with peculiar properties for construction of drillable bit solid body. Bench and field tests provided evidence of the validity of selected bit design and material. Field tests have demonstrated that drilling rate is directly proportional to axial load, while drilling is initiated at unit load of 25 kg/cm2. At optimum unit load of 50 kg/cm2, the drilling rate is estimated at 15 m/h. Drilling was conducted using commercially available PDC bits. Selection of appropriate bit body material and optimal bit design provided a reliable drillable rock-cutting tool to enable implementation of casing drilling technology.
2. Fatkulin S.A., Gumich D.P., Zabuga S.V. et al. Second wind for drilling with casing technology of glory. Burenie i Neft [Drilling and Oil], 2019, No. 4, pp. 30–34. (in Russian)
3. Ishbaev G.G., Kovalevskii E.A. Designing of rock destruction tool for casing drilling. Burenie i Neft [Drilling and Oil], 2017, No. 1, pp. 32-35. (in Russian)
4. Patent RU 2766136, Doloto dlya bureniya na obsadnoy kolonne [Drill bit for casing drilling], Int.Cl. Е21В 7/20, publ. 08.02.2022. (in Russian)
5. Akhmadishin F.F., Yagafarov A.S. Burenie s ispolzovaniem obsadnoy kolonny i razburivaemogo dolota [Drilling using casing string and drillable bit]. Neftyanoe Khozaistvo [Oil Industry], 2022, No. 7, pp. 10-12. (in Russian)
A.S. Yagafarov, PhD, Senior Research Associate, Drilling Department, TatNIPIneft Institute-PJSC TATNEFT
32, Musa Jalil st., Bugulma, 423236, Russian Federation
F.F. Akhmadishin, PhD, Head of Drilling Department, TatNIPIneft Institute-PJSC TATNEFT
А.S. Yagafarov, F.F. Akhmadishin Razrabotka i ispytaniye razburivayemogo dolota [Development and testing of drillable bit]. Neftyanaya Provintsiya, No. 2(34), 2023. pp. 242-251. DOI https://doi.org/10.25689/NP.2023.2.242-251. EDN XRRNVU (in Russian)