EFFECT OF DOWNHOLE ASSEMBLY AND POLYCRYSTALLINE DIAMOND COMPACT (PDC)BIT GEOMETRY ON STABILITY OF DRILLSTRINGS

Stability of drillstrings equipped with PDC bits depends an many facto rs such as the design of the drillstring, design of the bit, and forma tion type. In this paper, we show that the drill pipe plays a minor ro le in stability in comparison with that of the drill collars. We also show that the number of bit blades affects the location of the stabili ty pockets, while their spacing affects the size of these peckers. Usi ng this data, a combination of drill collar and bit design can be used to provide operating speeds resulting in maximum stability of the dri llstring.