A Review of the Evaluation, Control, and Application Technologies for Drill String Vibrations and Shocks in Oil and Gas Well

Table 8

Contrast of conventional VSP, SIT SWD, drill-bit SWD and VSP-SWD.

Items	Conventional VSP	Drill-bit SWD	SIT-SWD	VSP-WD
Seismic source form	Conventional ground or sea seismic source	Seismic waves generated by a working drill bit	Swept impulse source	Conventional ground or sea seismic source
Seismic source location	The ground surface	Downhole		The ground surface
Signal receiver location	Underground cable	Ground or sea survey line		Downhole tool
Interfere with the drilling operation?	Yes	No		No
Data availability	After drilling	While drilling (near real time)		After drilling
Real-time data type	Full-wave data	Full-wave data		Check-shot time
Bandwidth	Larger	Narrower (with surface pilots), comparable (with downhole pilots)		Comparable (with downhole pilots)
Signal to noise ratio	Higher	Lower		Higher
Data preprocessing requirements	No	The cross correlation of reference signal and record signal (surface receiver array)		Underground preprocessing, automatic extraction check shot time, and quality factor
Signal transmission requirements	Conventional cable	The reference signal is transmitted through the drill pipe		Mud pulse
Range of application	Nonextended reach wells, nonhorizontal wells	Non-high inclination wells, nonhorizontal wells	Extended reach wells, horizontal wells	Deepwater drilling, extended reach wells, high inclination, and horizontal wells
Cost	Higher	Lower		Higher
Operative risk	Yes	No		Yes