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Chapter 6 – DRILL BITS                                           149






                    Drilling Hydraulics


                    Most drill bits incorporate nozzles, which direct the flow of drilling

                 fluid so as to efficiently clean cuttings from the bottom of the hole and

                 from the cutting structure. If cuttings are not moved away from the
                 bottom quickly, the cutting structure may end up cutting on cuttings,

                 which reduces the ability to cut virgin rock. These nozzles fit into holes
                 (called nozzle pockets) on the bottom of the drill bit (fig. 6–7). This allows

                 the drillers to be able to select nozzles with different inside diameters. A
                 smaller diameter nozzle will increase the speed that mud flows through it


                 (for a given flow rate). If the mud flows faster through the nozzle, it will

                 expend more energy at the bottom of the hole, which may give greater
                 drilling penetration.









































                 Fig. 6–7. PDC bit showing nozzles






        _Devereux_Book.indb   149                                                 1/16/12   2:09 PM
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