Structure features and oil and gas prospect of paleochannel revealed with 2D seismic data in The East of Karakulsko-Smushkovskaya uplift zone

Abstract

Relevance. Today carbohydrates blocks holders in south of Russiatake an interest inoil and gas potential objects with superficial bedding because of its reasonableexplorationcosts. This research work is devoted to study of so object concerned with carbohydrates traps revelation prospective. Aim. The unique because of its size and shape paleo-channel object confinedwith erosive cut on the top of cretaceous sediments was discovered with seismic data as the result of seismic prospecting works in 2008‑2019 on the Karalatskiy block (Astrakhan region, East of Karakulsko-Smushkovskaya uplift zone). The main direction of the research was the studying of its structure, origin and exploration prospective. Methods. The study was based on available seismic data (common reflection point method, 2D modification). Processing and interpretation of total seismic data volume were realized, expanded velocity analysis was performed, structure mapping were carried out. The qualitative leveldynamic analysis and attribute analysiswere realized. Results. It is supposed that ancient riverbed were forming in Neogene in condition ofinclination of territory in south direction. The structure and configuration of this object were defined more precisely and bedding peculiarities were preliminary estimated during studying. The extension of the object is 25.4 kilometers, the area is 65,4 square kilometers, the depth is from 750 to 1050 meters. Exact stratigraphy of sediments filling up the cut, needs to be defined more exactly because of lackof boring data on the field. The results of matching with wells of neighbor Kirikilinskiy block show late cretaceous age of base rocks, some spans of the cut reach lower cretaceous sediments. The study of similar objects and geological history of the region allow supposingthat rocks filling up the cut belong to Pliocene. Research shows that the object isconfined to mainchannel of ancient delta or lowerpart of ancient river similar to present-day Volga River. Filling up rocks horizons reflected waves energyis higher than for base rocks, this occurrenceis not typical for paleo-channel objects of contiguous areas. Abnormally low values of RMS velocities were detectedduring the velocity analysisin the object area. The confirmation of paleo-river genesis of the object was achieved as the result, complex andinconstant structure of the rocks with lateral lithology changing andpotential presence of fluids was detected. The result data allowed to estimate preliminary perspectives of oil and gas content for the paleochannel and to outline the subsequent geophysical study and exploration drilling performance.