Application of a PDC-Roller Hybrid Bit in Highly-Deviated Wells of the Nanpu Oilfield

Directional drilling operations involving PDC bits or roller bits for highly deviated wells in the Nanpu Oilfield are characterized by significant friction resistance,high back pressures,dramatic fluctuations in torques and difficulties related to placement of tool faces.To solve these problems,PDC-roller hybrid bits with a combination of outstanding features of PDC bits and roller bits were deployed in the Nanpu Oilfield.With consideration to specific geologic conditions,two kinds of PDC-roller hybrid bits,with "2 rollers+2 fixed PDC cutters" and with "4 fixed PDC cutters+2 rollers",were developed.The performances of these two kinds of hybrid bits in the Well NP2-33 and the Well NP5-28 could be summarized as follows:during directional drilling by using the innovative PDC-roller hybrid bit with 2 kinds of cutting structures,no back pressure was observed.At the same time,tool faces remained steady and fluctuations of torques were minor.With build-up capacities equivalent to those of roller bits,the newly-developed hybrid bits enhanced ROPs and footage significantly.Returned cuttings with higher granularity and better sorting might effectively enhance accuracies in determination of lithologic and logging features.Field application performances showed the innovative PDC-roller hybrid bits could effectively remove problems related to back pressures,significant fluctuations in torques,difficulties in placement of tool face and other problems in drilling of highly deviated wells in the Nanpu Oilfield.The bit could effectively enhance ROPs of highly deviated wells.