Detailed study of geology of the lower parts of Pliocene in Kurovdagh area by use of 3D seismic survey

Abstract

The article is devoted to the study of the geological structure of the lower parts of the Productive Series of the Lower Pliocene of the Kurovdagh field.

It consists of an introduction, problem statement, research questions, research methodology, results, conclusion and list of references. The introduction provides basic information about the field under study, its geographical location, the history of geological and geophysical studies, the lithology of the section, the structure of the Kyurovdag fold and the oil and gas potential of the field.

Oil and gas presence inthefield is related to the Absheron stage of Pleistocene, Akchagyl stage and Productive Series (horizons PS01—PS23) of Neogene. Despite the long-term production from the field, the lower parts of the Productive Series and underlying sediments have not been recovered and sufficiently studied by deep drilling due to the complicated surface and deepseismo-geological environment. It has been recommended to carry out a 3D seismic survey due to a high level of lateral one-fold reflections on seismic records.

The major goals of the 3D seismic survey were studyingthe Kurovdagh field's geologic setting, obtaining characteristics previously unknown to geoscientists, and providing detailed research on velocity section to derive prognostic time-depth dependence.

It was noted that thePetroalliance Services Company Limited geophysical company has performed a field seismic survey on request «The Caspian Energy Group» company. Processing of the acquired data used the FOCUS 5.4 software package manufactured by Paradigm Geophysical.

For repeated interpretation of 3D seismic survey data, the 3D CDP data acquired from the field were used. The kinematic analysis by use of the 3 D cubes revealed the difference by the time shift, frequency spectrum, and amplitude range. The 3 D cubes were brought to a single formby time, phase, and amplitude. The further kinematic interpretation displayed the good quality of the data acquired from Kurovdagh area. The study applied PANGEYA® software for a multi-attribute geological and geophysical data analysis and the standard interpretation.

For volumetric modeling of the productive layers of the Kurovdagh oil field, we used the PETREL.10.2 software package. The study targets included complex, lithologically, and tectonically sealed deposits of Productive Series PS01—PS09 and Akchagyl stage (AKCH). Productive layers are attributed to Neogene's Pliocene stage within the Caspian basin's limits.

It is represented by a thick series of continental, coastal, and marine sediments (sand, clay, coarsely fragmented depositions) of 1600 m thickness and is unconformity laying over the Pontian stage and covered by the Akchagyl layers in a transgressive form. The Akchagyl stage is one of the stages of the Upper Pliocene which is made of clay, limestone, marl, sandstone, sand, and conglomerates.

It became clear that the Kurovdagh field is characterized by a block type structure across the geological section. Block sizes are almost unchanged, evidencing conformance of structural stages and heritance of tectonic movements. Mud volcano and diapiric folding and their sizes are the major distinguishing features of the area.