Patent ID: 6250408
Filing Date: 2001-06-26
Classification: E21B

Abstract:
A rotary drag bit for drilling a subterranean formation, comprising:a bit body having a longitudinal axis and a face thereon extending radially outward from the longitudinal axis;a plurality of blades extending above and generally radially over the face and outwardly of the bit body, the blades separating and defining the plurality of radially extending fluid courses leading to a plurality of junk slots extending longitudinally away from the bit body face;a plurality of cutters mounted to each of the plurality of blades, the plurality of cutters of at least one blade differing in at least one of number, size and exposure from a plurality of cutters mounted to at least one other blade such that a different formation cuttings volume is to be generated from engagement of the subterranean formation by the at least one blade cutters and the at least another blade cutters; anda plurality of nozzles for discharging drilling fluid from the bit body face into an area between the bit body face and the formation, the plurality of nozzles being located and oriented to apportion a discharge of drilling fluid between a fluid course positioned to receive formation cuttings generated by that at least one blade cutters and a fluid course positioned to receive formation cuttings generated by the at least another blade cutters in general proportion to the relative volumes of formation cuttings generated by each of the at least one blade cutters and the at least another blade cutters, the plurality of nozzles being further located and oriented to provide drilling fluid flow to each of the plurality of fluid courses so that a predominant flow direction in each of the fluid courses of the plurality is outwardly away from the longitudinal axis of the bit body and there is minimal cross-flow of fluid from a radially inner end of one fluid course into a radially inner end of any other fluid course.