Drill bit having offset roller cutters and improved nozzles

Claim 2

A rotary drill bit for drilling a well bore, the bit comprising: a bit body adapted to be detachably secured to a drill string for rotating the bit and to receive drilling fluid under pressure from the drill string, the bit body having a plurality of spaced apart, depending legs at its lower end, and a plurality of nozzles, one for each of said legs, for exit of the drilling fluid from the bit body; and a plurality of roller cutters, one for each of said legs, rotatably secured to the legs at the lower end thereof, each roller cutter comprising a generally frusto-conical cutter body and a plurality of powder metallurgy composite cutting elements on the cutter body, the roller cutters being so mounted on the bit body that the apices of the roller cutters are positioned generally toward a central portion of the bit body with the axes of rotation of the roller cutters spaced from the longitudinal centerline of the bit body a relatively large offset distance, whereby some measure of drag motion of the cutting elements across the formation at the bottom of the well bore is imparted thereto which results in enhanced drill bit cutting action, but also an accompanying increased tendency of the cut formation to adhere to the roller cutters in certain formations; each of said nozzles having passaging therein directing the drilling fluid under pressure to flow downwardly in a stream angled relative to the longitudinal axis of the bit body and generally toward the underside of one of said roller cutters, constituted by the half of said one roller cutter below its axis of rotation, along a line generally adjacent to its cutter body, the drilling fluid impinging at least some of the cutting elements on the roller cutter and thereafter impinging the formation generally at the bottom of the well bore spaced from the points at which the cutting elements of the roller cutter then engage the bottom of the well bore, whereby the formation and the cutting elements impinged by the stream are subjected to separate cleaning actions immediately prior to their engagement for presenting clean engagement surfaces to further enhance the drill bit cutting action.

Claim 3

A rotary drill bit as set forth in claim 1 wherein said offset distance is greater than about 1/16 inch of offset per inch of drill bit diameter.

Claim 4

A rotary drill bit as set forth in claim 1 wherein said offset distance is in the range from about 1/16 inch of offset to about 1/8 inch of offset per inch of drill bit diameter.

Claim 5

A rotary drill bit as set forth in claim 1 wherein the stream of drilling fluid from each nozzle flows along a line generally tangent to the cutter body of the respective roller cutter.

Claim 6

A rotary drill bit as set forth in claim 1 wherein the stream of drilling fluid from each nozzle flows in a direction generally opposite to the direction of rotation of the drill bit.

Claim 7

A rotary drill bit as set forth in claim 1 wherein the stream of drilling fluid from each nozzle impinges portions of the formation at the bottom of the well bore closely adjacent to, but spaced forward, with respect to the direction of rotation of the bit, of the points of engagement of the cutting elements of the respective roller cutter with the formation.

Claim 8

A rotary drill bit as set forth in claim 1 wherein the cutting elements of each roller cutter are arranged in annular rows around the cutter body, the stream of drilling fluid from each nozzle impinging cutting elements of at least one of the outer rows of cutting elements of the respective roller cutter.

Claim 9

A rotary drill bit for drilling a well bore, the bit comprising: a bit body adapted to be detachably secured to a drill string for rotating the bit and to receive drilling fluid under pressure from the drill string, the bit body having a plurality of spaced apart, depending legs at its lower end, and a plurality of nozzles, one for each of said legs, for exit of the drilling fluid from the bit body; and a plurality of roller cutters, one for each of said legs, rotatably secured to the legs at the lower end thereof, each roller cutter comprising a generally frusto-conical cutter body and a plurality of powder metallurgy composite cutting elements on the cutter body, the roller cutters being so mounted on the bit body that the apices of the roller cutters are positioned generally toward a central portion of the bit body with axes of rotation of the roller cutters spaced from the longitudinal centerline of the bit body a relatively large offset distance, whereby some measure of drag motion of the cutting elements across the formation at the bottom of the well bore is imparted thereto which results in enhanced drill bit cutting action but also an accompanying increased tendency of the cut formation to adhere to the roller cutter in certain formations; each of said nozzles having passaging therein directing the drilling fluid under pressure to flow downwardly in a stream angled relative to the longitudinal axis of the bit body and generally toward the underside of one of said roller cutters, constituted by the half of said one roller cutter below its axis of rotation, with the stream being so angled and position relative to said one of said roller cutters that as said one roller cutter rotates cutting elements thereon enter the stream for being cleaned thereby and then exit the stream prior to engaging the formation, with the stream after flowing past the cutting elements impinging the formation generally at the bottom of the well bore, whereby the formation and the cutting elements impinged by the stream are subjected to separate cleaning actions immediately prior to their engagement for presenting clean engagement surfaces to further enhance the drill bit cutting action.

Claim 10

A rotary drill bit for drilling a well bore, the bit comprising: a bit body adapted to be detachably secured to a drill string for rotating the bit and to receive drilling fluid under pressure from the drill string, the bit body having a plurality of spaced apart, depending legs at its lower end, and a plurality of nozzles, one for each of said legs, for exit of the drilling fluid from the bit body; and a plurality of roller cutters, one for each of said legs, rotatably secured to the legs at the lower end thereof, each roller cutter comprising a generally frusto-conical cutter body and a plurality of powder metallurgy composite cutting elements on the cutter body, the roller cutters being so mounted on the bit body that the apices of the roller cutters are positioned generally toward a central portion of the bit body with axes of rotation of the roller cutters spaced from the longitudinal centerline of the bit body a relatively large offset distance, whereby some measure of drag motion of the cutting elements across the formation at the bottom of the well bore is imparted thereto which results in enhanced drill bit cutting action but also an accompanying increased tendency of the cut formation to adhere to the roller cutter in certain formations; each of said nozzles having passaging therein directing the drilling fluid under pressure to flow downwardly in a stream angled relative to the longitudinal axis of the bit body and generally toward the underside of one of said roller cutters, constituted by the half of said one roller cutter below its axis of rotation, with the stream being so angled and position relative to said one of said roller cutters that as said one roller cutter rotates cutting elements thereon enter the stream for being cleaned thereby and then exit the stream prior to engaging the formation, with the stream after flowing past the cutting elements impinging the formation generally at the bottom of the well bore, whereby the formation and the cutting elements impinged by the stream are subjected to separate cleaning actions immediately prior to their engagement for presenting clean engagement surfaces to further enhance the drill bit cutting action.

Claim 11

A rotary drill bit as set forth in claim 8 wherein said offset distance is greater than about 1/16 inch of offset per inch of drill bit diameter.

Claim 12

A rotary drill bit as set forth in claim 8 wherein said offset distance is in the range from about 1/16 inch of offset to about 1/8 inch of offset per inch of drill bit diameter.

Claim 13

A rotary drill bit as set forth in claim 8 wherein the stream of drilling fluid from each nozzle flows along a line generally tangent to the cutter body of the respective roller cutter.

Claim 14

A rotary drill bit as set forth in claim 8 wherein the stream of drilling fluid from each nozzle flows in a direction generally opposite to the direction of rotation of the drill bit.

Claim 15

A rotary drill bit as set forth in claim 8 wherein the stream of drilling fluid from each nozzle impinges portions of the formation at the bottom of the well bore closely adjacent to, but spaced forward, with respect to the direction of rotation of the bit, of the points of engagement of the cutting elements of the respective roller cutter with the formation.

Claim 16

A rotary drill bit as set forth in claim 8 where the cutting elements of each roller cutter are arranged in annular rows around the cutter body, the stream of drilling fluid from each nozzle impinging cutting elements of at least one of the outer rows of cutting elements of the respective roller cutter.