Oligocene-Lower Miocene Clinoforms of the Pre-Caucasus Region – a New Target in the Old Petroleum Province

Abstract

Summary This research focuses on creation of a depositional model and prediction of clastic reservoirs in the Oligocene-Lower Miocene clinoforms of the Maikop Formation. The study area is the Central and Eastern parts of Pre-Caucasus region of Russia located in the south of Skifskaya platform and in the Pre-Caucasian foredeep. Based on analysis of logs, stratigraphic data for 16 deep-wells and seismic 2D data, 16 clinoforms (M1-M16) and a filling sequence (M17) are identified. The clinoform progradation-direction varies: M1–M7 prograde from the northeast to the southwest, M8 - westwards and eastwards, M9–M12 - eastwards, M13–M16 - from north to south. There exist 3 seismic types of clinoforms based on geometry: subaqueous delta (37–75 m high), shelf-edge delta (150–800 m high), low angle clastic wedges of the slope and deep basin (120–270 m high). The bathymetry of the paleobasin increased from 300 m to 800 m from M1 to M8 sequences, decreased during deposition of M9-M12 from 500–600 to 300 m. Sequences M13–M17 compensated vestigial deep-water basin. Sandy material transported by subaqueous deltas in the topset of the shelf-edge deltas during high stand system tract and by gravity flows on the slope and bottomset of the shelf-edge deltas during sea level falling.