Industry Article: Real-Time Seismic-While-Drilling to Reduce Exploration Risk

Real-time seismic-while-drilling to reduce exploration risk
Publication: Offshore
Publication Date: 06/01/2012

Depth uncertainty is a major challenge when drilling wildcat exploration wells, because the nearest offset wells are usually too far away to provide any reliable useful indication of subsurface geology. In common with many exploration wells, planning the position of the first well—Apalis-1, drilled in block LB-09—was based solely on surface seismic imaging. African Petroleum decided to utilize the seismicVISION seismic-while-drilling service while drilling the 17 1/2-in. hole section—a look-ahead technology that delivers time-depth-velocity information in real time while not disrupting drilling operations. The real-time checkshot data acquired while drilling the during the 17 1/2-in. hole section showed that the actual measured velocity was slower than the pre-drill velocity predicted from the surface seismic data, which meant that the target horizons would be shallower than the predrill prognosis. The checkshot data allowed the section TD to be pushed to within 100-ft (30-m) of the expected seismic marker. This was deeper than could otherwise have been achieved safely given the original depth uncertainty—estimated at +/- 100-m.

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