Because the anisotropy of shale formation should result in that wellbore deviations is unpredictable, the bit-rock interaction should be fully lucubrated in order to eliminate this problem. The impact of shale rock anisotropy and the cutting velocity on the load of PDC cutter wasn’t considered by the existing cutter-rock interaction models. On the basis of experiments of cutting shale with PDC cutter, using the stress tensor analysis theory, the relationship between the shale rock anisotropy and the cutter’s force is proposed in this paper. A new cutter-rock interaction model was established, and then a new bit-rock interaction model was set up. That applying these models to the ROP prediction of directional PDC bit can improve forecast accuracy is found.

Singer PDC cutters of five different cone top diameters are designed and manufactured.On the basis of rock-breaking test with stinger PDC cutters, effects of significant factors on cutting forces are discussed, including cutting angle, cutter shape and rock hardness. The test results show that the stinger PDC cutters have the ability of drilling hard rock.The sharper the stinger PDC cutter is, the stronger the ability of drilling the formation will become.15°is an optimal front rake angle.