The Geomagnetic Field Transformants and Their Complexing with Data of Gravitational, Thermal and Radioactive Fields: During the Exploration of Hydrocarbon Fields at the Southern Part of the Ustyurt Region

Abstract

The chapter discusses the results of the interpretation of aeromagnetic survey data in the southern part of the Ustyurt region in order to identify zones that are heterogeneous in magnetic properties, with their subsequent tie-up with areas promising for the detection of hydrocarbon accumulations. Three tectonic elements are distinguished—the Central Ustyurt system of disturbances, the Shakhpakhty step and the Assakeaudan depression according to the sign, orientation and quantitative values of the transformants of the geomagnetic field, and, consequently, according to the depth and extent of distribution of magnetized rocks, based on the degree of deformation of lithological-stratigraphic complexes and levels by deep faults. Within these tectonic elements, the transformants of the geomagnetic field were comprehensively interpreted with the data of gravitational, thermal and radiochemical fields to increase the reliability of the results of geological interpretation. This made it possible to study the behavior and characteristics of faults, to draw conclusions about the depth of gravitational and magnetically disturbing masses, about the degree of geological heterogeneity of large geostructures, as well as to trace the nature of the manifestation of local structures in geophysical fields. The Central Ustyurt system of dislocation, the Shakhpakhty step and the Assakeaudan depression differ in varying degrees of active tectonics and differentiation by the degree of dislocation of oil and gas prospective objects, fragmentation by faults, by the extent of distribution of reservoir rocks and oil and gas source suite, conditions of conservation of hydrocarbon accumulations, directions and channels of probable hydrocarbon migration, and assumptions are made about the relationship of oil and gas prospective structures and explored hydrocarbon field with large deep faults. The author’s studies of transformants of magnetic and gravitational fields, geothermal and aerogamma spectrometry data clearly indicate in favor of the prospects of oil and gas potential of local structures of the Shakhpakhty step: Utezhan, Kozhantai, Northern Kozhantai, Otynshy. In general, the results obtained will serve as a reliable basis for clarifying and detailing the geological and structural-formation models of the Southern Ustyurt, which can be used as the basis for the design of geological exploration for the exploration of new hydrocarbon field using expensive and time-consuming seismic exploration of CDP-3D and deep drilling.