Application of seismic and seismoacoustic methods to identify migration routes of hydrocarbon and enhanced oil recovery in zones of tectonic faults in the Vostochnobortovaya oil and gas region of the Peri-Caspian Depression

Abstract

The oil and gas fields of the Vostochnobortovaya oil and gas bearing region of the Peri-Caspian Depression are characterized by a complex tectonic structure. The analysis of the Alibekmola oil and gas condensate field development shows that tectonic blocks of deposits intercommunicate along lowamplitude faults and fracture zones, which have the form of filter channels, and which positively affects the process of their development. The aim of the work was to analyze the results of the application of seismic and seismoacoustic methods to identify fracture zones, migration routes of hydrocarbon and enhanced oil recovery in zones of tectonic disturbances in the study area using the Alibekmola field as an example. Methods. An updated interpretation of the temporary seismic profiles of CDPM -3D, crossing the field in the sublatitudinal and submeridional directions, was carried out using the author’s methodological techniques. The interpretation took into account the seismogeological signs of the discovery of geodynamic centers of hydrocarbon generation in the basement. To study the current oil saturation and stimulate oil production from the productive strata of the AOGCF, the well log of the induced seismoacoustic emission in a cycle with simultaneous acoustic impact on the near a heading zone in well No. 54, was applied. Results. According to the new interpretation, the Alibekmola oil and gas field in cross section is a near-fault horst-like uplift. In the rocks of the sedimentary cover, a network of low-amplitude faults with the “flower” structure was identified. Some faults are traced from subsalt deposits to post-salt rocks; this fact indicates their neotectonic nature. Large deep disturbances tectonically shield oil and gas-oil deposits. Most faults are traced from the basement. Some of them simultaneously affect the oil and gas deposit, break through the salt-bearing strata of the Kungurian age, “getting stuck” in it or “coming out” in the post-salt deposits. Disturbances serve as routes for the migration of hydrocarbons. In longitudinal section, the deposit is a combination of horsts and grabens. The results of the study of well No. 54 using the method of seismoacoustic emission confirm the presence of fractured reservoirs in the oil deposit and show that after the study and acoustic impact in the working intervals the acoustic emission of the formation increased, and with it the fluid inflow. Productivity of the well has improved, the number of working interlayers increased. In many cases, the acoustic emission signal became more pronounced, which corresponds to the presence of a fractured reservoir. The interval subjected to acoustic impact, as a result of which there was a positive dynamics in the work of the well, coincides with the identified fault, confirming its existence. It is concluded that the Alibekmola field is the result of vertical migration of hydrocarbons; using the KVK-SAE method, it is possible to influence directly the filtration capacity of its routes.