Despite of negative results in finding giant and large fields during the last 10–15 yr, the North Caspian basin still remains a highly prospective frontier. Complex geology, great depths to the main subsalt plays, and poor resolution of most seismic surveys caused by the presence of thick deformed salt are responsible for the lack of exploration success. However, the potential for finding world-class fields continues to attract the interest of major international oil companies despite the economic and political instability of the region.
Several regional plays, which were defined approximately 15 yr ago, are still believed to contain the principal undiscovered potential. Among these plays, carbonate banks of the Tengiz type located offshore are certainly the most obvious prospects. Primary risks related to this play include salt seal integrity and the resulting preservation of hydrocarbons and expected oil versus gas hydrocarbon phase. The Kashagan well, presently in drilling, will soon provide data on some of these uncertainties. Isolated atolls and pinnacle reefs similar to Karacha-ganak remain the most attractive targets along the entire northern and western basin margins. However, very limited progress has been recorded in pursuing this play since the discovery of the Karachaganak field primarily because of the very deep occurrence of the prospects. No significant new fields were found in the structural trap play of the Zhanazhol type on the eastern margin. The Mesozoic salt-dome play is undoubtedly highly potential, but not for giant and very large fields. Presently, few players are pursuing these prospects.