Abstract: In order to improve the penetration rate of PDC bits for drilling through heterogeneous formations and to extend the life of drill bits,a new type of PDC bit with a tapered auxiliary cutter has been developed.The bit uses a PDC cutter as the main cutting element,with the conical cutter and PDC cutter as auxiliary cutting elements.When the bit starts to work,the PDC cutter will break rocks in "shearing" mode.After the PDC cutter drills into the formation to some extent,the conical cutter starts to plow and cut the rock to generate cracks and induce local fractures,which helps the PDC cutter break the rock at a relatively low cutting force.The rear cutter of two adjacent blades are arranged with the conical cutter and the PDC cutter respectively,which is used for the rate of penetration to increase and efficiency improvement of the bit in the later stage.It incorporates the characteristics of stable rock breaking efficiency of conventional PDC bits as well as the advantages of high rock breaking efficiency of the conical cutter in heterogeneous formations.The bit has been through field testing in different regions.Testing results show that the new bit has longer drilling life and higher penetration rate than conventional PDC bits in drilling through heterogeneous formations.The successful development of the new type of PDC bit provided a new and efficient rock breaking tool for drilling through heterogeneous formations.