Vendian-lower Cambrian saltless rock associations in Lebyazhinsky zone of Siberian platform: conditions and causes of formation

Commercial hydrocarbon accumulations in Riphean, Vendian terrigenous and Upper Vendian-Lower Cambrian plays of the Lena-Tungussky Petroleum Province of the Siberian Platform are always found below the regional impermeable sequence that is the Early Cambrian thick salt-bearing carbonate regional seal. Therefore, investigation of the occurrence regularities of Lower Cambrian salts is an important geological task. Overestimation of the facies factor and underestimation of secondary changes result in wrong conclusions, and this complicates regional exploration and prospecting for oil and gas. Invalidity of certain geological reconstructions is shown by the example of the Lebyazhinsky zone. Basing on the drilling data, seismic lines, and hydrogeochemistry materials, area of intensive leaching determined by faults is identified. The authors prove that Cambrian facies zonation in the area of the current Yenisei Ridge and its neighbourhood has the less complex nature and lower average number of permeable intervals. These facts confirm the well-known theory-based point of view on the Late Palaeozoic time of its occurrence in the current form