Fixed Cutter Bit With Backup Cutter Elements on Primary Blades

A drill bit for drilling a borehole in earthen formations, the bit comprising:

• a bit body having a bit axis and a bit face comprising a cone region, a shoulder region, and a gage region;
• a plurality of primary blades, each primary blade extending along the cone region, the shoulder region, and the gage region of the bit face;
• a plurality of primary cutter elements mounted to each primary blade;
• at least one backup cutter element mounted to each primary blade in the shoulder region;
• a plurality of secondary blades, each secondary blade extending along the shoulder region and the gage region of the bit face;
• a plurality of primary cutter elements mounted to each secondary blade;
• wherein the ratio of the total number of backup cutter elements mounted to the plurality of primary blades to the total number of backup cutter elements mounted to the plurality of secondary blades is greater than 2.0.
• wherein each backup cutter element and each primary cutter element has a radial position;
• and
• wherein each backup cutter element on each primary blade has substantially the same radial position as one of the primary cutter elements on the same primary blade.

A drill bit for drilling a borehole in earthen formations, the bit comprising:

• a bit body having a bit axis and a bit face comprising a cone region, a shoulder region, and a gage region;
• a first and a second primary blade, each primary blade extending along the cone region, the shoulder region, and the gage region of the bit face;
• a plurality of primary cutter elements mounted to each primary blade;
• a backup cutter element mounted to each primary blade in the shoulder region;
• a secondary blade extending along the shoulder region and the gage region of the bit face;
• a plurality of primary cutter elements mounted to each secondary blade;
• wherein the ratio of the total number of backup cutter elements mounted to the plurality of primary blades to the total number of backup cutter elements mounted to the plurality of secondary blades is greater than 2.0;
• wherein each backup cutter element and each primary cutter element has a radial position;
• wherein the backup cutter element on the first primary blade has a different radial position than each primary cutter element on the first primary blade;
• and
• wherein the backup cutter element on the first primary blade has the same radial position as one of the primary cutter elements on the second primary blade or one of the primary cutter elements on the secondary blade.