Improving the subsurface geological model while drilling
The revision of a well prognosis has, until comparatively recently, been possible only at the end of a drilling phase. As an inevitable consequence, the new data and the conclusions arising from the revised prognosis come too late to change the drilling or operational programme in any way. This paper discusses a technique whereby information gathered during drilling can influence the course of the drilling. These techniques are Seisbit or Seismic While Drilling (SWD) (Widrow 1990; Rector et al. 1991; Abramo et al. 1996; Miranda et al. 1996; Poletto et al. 1997), and Migration While Drilling Continuously (MWDC) (Aleotti et al. 1995). Both were pioneered by AGIP and are implemented using the software package Drilling and Real Time Migration (DREAM*), developed jointly by Agip and Western Geophysical (AGIP & Western Geophysical 1997).