Methods, systems, and bottom hole assemblies including reamer with varying effective back rake

A reamer bit comprising:

• a generally tubular body extending between a first end and a second end, the generally tubular body configured for attachment to a drill string;
• and
• a plurality of cutting elements carried by the generally tubular body between the first end and the second end thereof, the cutting elements of the plurality defining a cutting profile spaced radially apart from a longitudinal axis of the reamer bit when the one or more blades are in an operable position, wherein at least one cutting element of the plurality has an effective back rake angle of about fifteen degrees (15°) or more;
• wherein the cutting profile of the reamer bit includes a lower shoulder region and an upper shoulder region, cutting elements of the plurality in the lower shoulder region having a first average effective back rake angle that is greater than a second average effective back rake angle of cutting elements of the plurality in the upper shoulder region.

A reamer bit comprising:

• a generally tubular body extending between a first end and a second end, the generally tubular body configured for attachment to a drill string;
• and
• a plurality of cutting elements disposed on one or more blades carried by the generally tubular body between the first end and the second end thereof, the cutting elements of the plurality defining a cutting profile spaced radially apart from a longitudinal axis of the reamer bit and longitudinally apart from the first end and the second end of the generally tubular body when the one or more blades are in an operable position, at least one cutting element of the plurality of cutting elements having a side rake angle of about five degrees (5°) or more;
• wherein the plurality of cutting elements comprises all the cutting elements carried by the reamer bit between the first end and the second end.

A reamer bit comprising:

• a generally tubular body extending between a first end and a second end, the generally tubular body configured for attachment to a drill string;
• and
• a plurality of cutting elements disposed on one or more blades carried by the generally tubular body between the first end and the second end thereof, the cutting elements of the plurality defining a cutting profile spaced radially apart from a longitudinal axis of the reamer bit when the one or more blades are in an operable position, at least one cutting element of the plurality of cutting elements having a side rake angle of about five degrees (5°) or more
• wherein cutting elements of the plurality in a lower shoulder region of the cutting profile have a first average side rake angle, and wherein cutting elements of the plurality in an upper shoulder region of the cutting profile have a second average side rake angle less than the first average side rake angle.

A reamer bit comprising:

• a generally tubular body extending between a first end and a second end, the generally tubular body configured for attachment to a drill string;
• and
• a plurality of cutting elements disposed on one or more blades carried by the generally tubular body between the first end and the second end thereof, the cutting elements of the plurality defining a cutting profile spaced radially apart from a longitudinal axis of the reamer bit when the one or more blades are in an operable position, at least one cutting element of the plurality of cutting elements having a side rake angle of about five degrees (5°) or more;
• wherein cutting elements of the plurality in a lower shoulder region of the cutting profile have an average side rake angle of at least about fifteen degrees (15°);
• and
• wherein the plurality of cutting elements comprises all the cutting elements carried by the reamer bit between the first end and the second end.

A method of drilling a wellbore in a subterranean formation, comprising:

• selecting a pilot bit having a first plurality of cutting elements in shoulder regions of a cutting profile of the pilot bit, the cutting elements of the first plurality having a first average effective back rake angle;
• selecting a reamer bit having a second plurality of cutting elements in shoulder regions of a cutting profile of the reamer bit, the cutting elements of the second plurality having a second average effective back rake angle greater than the first average effective back rake angle;
• drilling a pilot bore using the pilot bit;
• and
• reaming the pilot bore with the reamer bit while drilling the pilot bore using the pilot bit.

A method of forming a drilling system, comprising:

• forming a pilot bit having a first plurality of cutting elements in shoulder regions of a cutting profile of the pilot bit;
• positioning the cutting elements of the first plurality on the pilot bit to have a first average effective back rake angle;
• forming a reamer bit having a second plurality of cutting elements in shoulder regions of a cutting profile of the reamer bit;
• positioning the cutting elements of the second plurality on the reamer bit to have a second average effective back rake angle greater than the first average effective back rake angle;
• and
• securing the pilot bit and the reamer bit to a common drill string.