The work presents the positive experience of the slot-recovery of the wellhead platform at the Dragon field of JV «Vietsovpetro» after the abandonment of an exploration well by drilling the trunk of a new production well on a casing string with a diameter of 508 mm with a deviation from the vertical axis of the slot. The main advantages of the casing while drilling method for drilling a new well from the restored slot are confirmed: a) the entire drilling interval is effectively and reliably secured by the casing string using this method; b) the time for running the casing string is excluded from the calendar time of well construction; c) problems associated with wellbore complications in this interval are completely eliminated due to the effect of mechanical clogging of the wellbore walls; d) a better-quality wellbore is formed compared to conventional drilling, due to the high annular velocity of the upward flow of the flushing fluid, which contributes to more efficient cleaning of the well. Some technical and technological aspects of this technology are presented. Technical difficulties associated with the very small deviation between the new 508 mm surface casing and the old conductor of the abandoned well were resolved by mechanical adjustment of the three platform guides inclination in a way, that allowed tilting the surface casing to the maximum required angle, in order to ensure the designed reach at the seabed. Successful application of a number of advanced technological solutions and tools from the leading oil and gas equipment manufacturers during casing drilling operations, such as casing running tool with internal wedge casing gripper (CRTi) and packer element, drillable four-blade shoe bit with hydro-monitor nozzles and PDC cutters on the casing, special high-torque unloading rings, all-metal centralizer and premium casing cementing coupling with two check valves allowed reducing the drilling time of new well from the recovered slot in the surface casing interval by 1 day.
References
1. Shorokhovetskiy S.E., Mirovoy opyt primeneniya tekhnologii bureniya na obsadnoy kolonne (World experience in using casing drilling technology), Proceedings of conference “Problemy geologii i osvoeniya nedr. Sektsiya 14. Sovremennye tekhnika i tekhnologii bureniya skvazhin” (Problems of geology and subsoil development. Section 14. Modern equipment and technologies for drilling wells), Tomsk: Publ. of TPU, 2016, pp. 804-806.
2. Gupta A.K., Drilling with casing: Prospects and limitations, SPE-99536-MS, 2006, DOI: http://doi.org/10.2118/99536-MS
