Dual inversion applied to D multi‑component seismic data onshore Libya

Wintershall-Libya’s onshore concession 97 includes the Nakhla field where oil is produced from the almost 4 km deep Sarir sandstone reservoir. For each new production well in the field, as well as for each appraisal or exploration well in the concession and surrounding areas, the main risk is an absence of Sarir sandstone reservoir. Reservoir sandstones can be partly or fully missing because of intrusions of basalt or deposition of volcanoclastics or presence of shallow basement. Figure 1 illustrates the risks involved, providing a schematic view of a 3 km short line, the worst case line with three dry wells and only one oil well. Looking at well statistics, the overall risk is lower but significant, in the order of 10-30%. Much geophysical and geological effort has been spent over the years to understand the issue and, despite much progress in terms of qualitative understanding (Weihe et al., 2004; Fornaciari et al., 2003), there has only been limited success in terms of quantitative prediction, i.e. what is the risk of encountering a non-reservoir in a new well location?