Stability enhanced drill bit and cutting structure having zones of varying wear resistance

A drill bit for drilling a borehole through formation material when said bit is rotated about its axis, said bit comprising:

• a bit body;
• a bit face on said body, said bit face including a central portion, a shoulder portion adjacent to said central portion and a gage portion adjacent to said shoulder portion defining the diameter of the borehole;
• a first plurality of redundant PDC cutter elements having cutting faces with a first abrasion resistance mounted in a first radial position on said bit face;
• and
• a second plurality of redundant PDC cutter elements having cutting faces with a second abrasion resistance that is less than said first abrasion resistance, said second plurality of cutter elements being mounted at a second radial position on said bit face that is spaced apart from said first radial position.

A cutting structure for a drill bit comprising:

• a bit face;
• cutter elements having PDC cutting faces disposed on said bit face, each of said cutter elements having an element cutting profile;
• wherein said cutter elements include a first plurality of cutter elements having cutting faces with a first abrasion resistance and a second plurality of cutter elements having cutting faces with a second abrasion resistance that is less than said first abrasion resistance;
• and
• wherein said first and second plurality of cutter elements are arranged in sets on said bit face, each set including a set cutting profile defined by said element cutting profiles of said cutter elements in said set;
• and
• wherein a first set of cutter elements includes a first cutter element of said first plurality at a first radial position on said bit face and a second cutter element of said second plurality radially spaced from said first cutter element at a second radial position on said bit face, said element cutting profiles of said first and second cutter elements partially overlapping in rotated profile and forming adjacent regions within said set cutting profile, said adjacent regions including a first region having a relatively high abrasion resistance, a second region having an abrasion resistance that is less than said relatively high abrasion resistance, and a third region of multiple diamond density that is disposed between said first and second regions, said third region defined by the area of overlap between the cutting profiles of said first and said second cutter elements.

A cutting structure for a drill bit comprising:

• a bit face;
• a first PDC cutter element on said bit face having a first cutting face for cutting a kerf in formation material;
• and
• a second PDC cutter element on said bit face having a second cutting face for cutting a kerf in formation material;
• wherein said first and second cutting faces each include a first region and a second region and wherein said first region of each of said cutting faces has a higher abrasion resistance than said second region of said same cutting face, said first and second regions having different average diamond grain sizes;
• and
• wherein said first and second cutting faces have cutting profiles that partially overlap when viewed in rotated profile.