Structure and interpretation of the anomalous magnetic field of the South Turgay petroleum region

Abstract

Purpose. Study on the deep structure of the South Turgay petroleum region to assess the influence of magnetic causative masses on the processes of generation, migration, accumulation and conservation of hydrocarbon (HC) accumulations, taking into account the evolution of rift development modes of the same sedimentary basin. Methodology. The combination of regional magnetometry data is applied with deep drilling data using a priori data on historical-geological, structural-formation, reservoir qualities and other factors. With the complex spatial anisotropy of the geomagnetic field and the distribution of magnetization of rocks in the Earth’s crust, the physical prerequisites of magnetic survey data provide quite correct geological interpretation of the results obtained. Findings. Classification and zoning of geomagnetic field anomalies by their morphology, intensity values, gradient and size was conducted, which made it possible to perform identification and geological forecast of magnetically causative bodies and determine their qualitative (structural) features.Various degrees of magnetization of different-age rocks of the South Torgay Petroleum region, as well as their relative location, structure, and depths of occurrence were established. It was revealed that the sedimentary cover and the upper part of the basement here are composed of low-magnetic and non-magnetic formations, and the upper edges of the magnetically disturbing masses lie at different depths in the consolidated crust, but, in general, deeper than the intervals of the section penetrated by deep drilling. Originality. The genetic, historical, geological, and tectonic-magmatic features of the South Torgay basin differ sharply from those of the adjacent Lower Syrdariya arch and Shu-Sarysu Depression. At the present stage of evolution, South Torgay sedimentary basin has a significant endogenous warming of the lithosphere in contrast to the adjacent Lower Syrdariya arch and Shu-Sarysu depression. To some extent, it indicates the inheritance in the regime of development of the South Turgay sedimentary basin from the Paleozoic and Mesozoic stages of rifting. Practical value. The depth of occurrence of magnetically causative objects significantly expand the stratigraphic interval of sediments that can be involved in the exploration process. The inherited mode of rift evolution of the basin suggests a favorable combination for the formation of a wide range of hydrocarbon traps, oil and gas source rocks, migration pathways, accumulation and preservation of HC accumulations.