Drill bit with PDC cutters with different backrake angles

摘要

A drill bit is disclosed which includes a bit body having a plurality of blades thereon. The blades have a plurality of cutting elements (12) affixed thereon at selected positions. The cutting elements (12) are disposed into at least two groups. A first one of the groups has at least 60 percent of the cutting elements (112) therein disposed at a first mean backracke angle. A second group has at least 60 percent of the cutting elements (212) therein disposed at a second mean backrake angle. The second backrake angle is at least about fifteen degrees more than the first backrake angle. A bottom hole coverage of the cutting elements in the second group is at least about eighty percent. <IMAGE>