Oil potential of the Lower Mesozoic deposits of the Khapchagai megaswell of the Vilyui syneclise

Analysis of all available geological, geophysical, and field data on some gas condensate fields discovered within the Khapchagai megaswell (Vilyui syneclise of the Siberian Platform) as early as the 1960s shows the presence of oil rims in Lower Triassic (horizon T1-III in the Srednevilyuiskoe and Tolonskoe gas condensate fields and horizon T1-Kh in the Mastakhskoe gas condensate field) and Lower Jurassic (horizons J1-I and J1-II in the Mastakhskoe gas condensate field) deposits. The C3 oil reserves in these rims are estimated at several tens of millions of tons of oil. The results are indicative of the oil potential of the Lower Mesozoic deposits not only of the Vilyui syneclise but also of the Lena–Vilyui petroliferous province as a whole, which was always characterized as a gas-bearing province in summary reports.