Customized design of micro-core PDC bit and its application in the deep formations of Nanpu Oilfield

The deep formations in the third member of Dongying Formation and the Shahejie Formation in Nanpu Oilfield are characterized by high compaction degree, complex lithology, tight mudstone cementation, strong abrasiveness and poor drillability, which reduce the ROP of conventional PDC bit. Micro-core PDC bit was researched and developed after the rock mechanical properties of these deep formations were analyzed thoroughly. In the micro-core PDC bit, no cogging is arranged in the central zone, the special structure without mandrel is adopted and the design of flat inner cone, wide crest and extended outer cone is applied to distribute more energy to the cutting structure which undertakes more work, so as to increase cogging’s bit weight per unit area and improve the rock breaking efficiency. Micro-core PDC bit has been applied on site over 10 well times, presenting better application results. Its average ROP is 8.7 m/h, 40% higher than routine, and its average footage per bit is 470 m, 100% higher than routine. The research results provide the new method for the efficient development of deep formations in Nanpu Oilfield.