Authors:
Elena N. Volkova,Ekaterina A. Vlasenko,DOI NO:
https://doi.org/10.26782/jmcms.spl.10/2020.06.00004Keywords:
Oil and gas prospects,geology,geophysics,Cis-Caspian depression,gravityprospecting, magnetic prospecting,interpretation,anomalies,transformations,Abstract
The article presents new methodological methods for interpreting geological and geophysical data with the aim of justifying the search for oil and gas in the inner regions of Cis-Caspian depression and confirming the hypothesis of uplifted foundation blocks and large drillable subsalt elevations. For the territory of Cis-Caspian depression, new schemes of composite magnetic field strength and gravity field anomalies maps were obtained at different transformation parameters, taking into account qualitative zoning of the territory according to sign ratios. The transformed parameters are obtained by analytic continuation into the upper half-space to a height of 5-50 km by calculating the residual values and difference in the geophysical values between the altitude levels, i.e. by obtaining interval transformants that narrowed the range of the possible interval of the geological section, in which the appearance of anomalous-forming masses in the subsalt paleozoic can be expected. The observed fields were represented in the form of numerical matrices covering theentire territory of Cis-Caspian depression with 120*100 dimensions of elements for maps of 1: 1 000000 scales. A total of 40 schemes of geophysical parameters were generated. In the central part, the transformations allowed identifying large, intense anomalies associated with the morphology of the subsalt bed surface. Gravity steps, which limit large anomalies, testify to the steep slopes of structural elements. This isthe possible zones of transition from shallow-water conditions to deep-water ones. The oil and gas prospects of the geological situation are determined by a combination of negative magnetic and positive gravitational fields observed in theincreasingly thick areas of carbonate rocks caused by organogenic structures of basinal, flankand shelftype on the slopes of major elevations. As a result of processing and interpretation, in Hobdin high area the author predicts the existence of an elevated relative to the depression part zone within which a possible socle for further growth of large carbonate structures such as Karachaganak is located. The zone with the same signs is also registered in the western part of the Central Caspian depression in the region of Aralsor gravity high.Refference:
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