Discussion on the Theoretical Basis for Cross-Over Method Applied to Downhole Wave Velocity Test

Figure 5

Relative error of of PPM, CCM, and NPPM at different testing depths: (a) excitation inclination 20°, geophone deflection 20°, and geophone inclination 10°, using the trigger signals; (b) excitation inclination 20°, geophone deflection 20°, and geophone inclination 10°, based on the adjacent received signals; (c) excitation inclination 20°, geophone deflection 50°, and geophone inclination 10°, using the trigger signals; (d) excitation inclination 20°, geophone deflection 50°, and geophone inclination 10°, based on the adjacent received signals; (e) excitation inclination 45°, geophone deflection 20°, and geophone inclination 10°, using the trigger signals; (f) excitation inclination 45°, geophone deflection 20°, and geophone inclination 10°, based on the adjacent received signals.

(a)

(b)

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(d)

(e)

(f)