Geothermal conditions of hydrocarbon prospects of Meso-Cenozoic formations in South Caspian Basin

Abstract

Temperature data of oil and gas fields and prospecting sites in the South Caspian Basin (SCB) are summarized. From the array of measured temperatures and stratigraphy data from 190 offshore and onshore fields as function of depth, 3D interpolated maps of temperature fields and stratigraphic units of the area are constructed. Available data covers the stratigraphic interval from Neogene to Upper Cretaceous and include Pliocene productive formations and anticipated source rocks intervals (Oligocene and Upper Cretaceous suites). Geothermal modes (temperature-depth curves) for specific fields and for the region as a whole can be approximated by generalized parabolic type functions with fitted coefficients according to actual field data. The thermal mode of the South Caspian Basin is compared with similar major hydrocarbon fields worldwide. Specific features of the geological history and deposition, in particular, fast subsidence and avalanche sedimentation (sedimentation rate 1―2 km per MA) resulted in SCB being one of the coldest basin among giant hydrocarbon basins worldwide. This allows anticipating the availability of a hydrocarbon generation zone at depths up to 15―20 km, that is essentially below the sedimentary formations of the Pliocene Productive Suite and underlying Oligocene Maykop Suite, which nowadays are the most searched exploration targets. In particular, the results in conjunction with other research data from geochemistry, stratigraphy and tectonics, as well as backstripping simulations, allow us to expect large HC bearing structures in Mesozoic formations, including potential deposits at ultra big depths up to 12 km.