The Role of Magnetic Methods in the Study of Areas of the Tight Oil and Gas: Introduction

Background. The war in Ukraine arises the urgent need to intensify hydrocarbon production on its own territory in order to maintain and develop the country's energy independence. The effectiveness, low cost and relevance of the involvement are demonstrated by magnetic methods of studies of the near surface geological section and the soil for the oil and gas prospecting. Methods. The methodology of magnetic studies for the hydrocarbon prospecting is based on the methods of studying the environmental magnetism and soil, precision magnetic survey of natural systems and authigenic models of changes in magnetic mineralogy under the influence of hydrocarbon fluid migration. Results. The crucial aim is to distinguish the sources of the formation of the magnetic minerals. In most cases, soils contain minerals of natural pedogenic origin, authigenic secondary magnetic minerals, and sometimes detrital fine-coarse magnetic phases. For Ukraine, magnetite, maghemite, hematite, and goethite are the most common magnetic minerals of soils of the pedogenic origin. At the same time, the experience of conducting magnetic mineralogical analyzes of soils in the territories of oil and gas deposits indicates the presence of iron sulfides. First of all, monoclinic pyrrhotite is identified. The soils also contain accompanying hexagonal pyrrhotite, pyrite, and greigite. The results of thermomagnetic analyzes and hysteresis loops of soil samples collected at the territories of hydrocarbon deposits are presented and their mineral composition is analyzed. Conclusions. The results of the study of the impact of hydrocarbon fluid migration (microseepage) on the change in the mineral composition of soils indicate significant informativeness and the perspective of introducing the method into the complex of geological exploration works at various stages. Authigenic changes of magnetic minerals in the near surface geological section and soil, as well as natural and anthropogenic accumulation of hydrocarbon products in soils, cause changes in magnetic properties and form magnetic field anomalies.

Fluids Migration Impact on Soil Magnetic Mineralogy

MENSHOV

2024

Improved Methodоlogy of Detailed Magnetometric Survey to Solve the Problems of Oil and Gas Geology

VYZHVA,

POPOV,

BONDAR

et al. 2024

Background. Nowadays, interest in studying the local anomalous magnetic field to solve the problems of oil and gas geology is growing, and the capabilities of the equipment can significantly increase the speed, accuracy and detail of work. Accordingly, the development and testing of an improved method of detailed magnetic recording in motion becomes relevant. Methods. For areas with low gradient magnetic field, we assessed the accuracy of the survey by comparing the maps obtained from repeated surveys of the site. Results. The survey of the magnetic field was conducted in the movement. The total surveyed area was about 20 square kilometers in the Zinkovsky district of the Poltava region. The inter-profile distance was about 50 meters, the distance between the points of observation on the profile was about 1 meter. This grid of observations allows us to get maps that differ significantly from the maps obtained by the usual density of observations. This technique also allows identifying local anomalies, and drawing conclusions about the fine structure of the magnetic field. The main objects that form anomalies and their geological characteristics are identified. On this basis, interpreted magnetic field anomalies in oil and gas regions were catalogued. Conclusions. We have proposed explanation of tectonic and geochemical factors, which form local anomalies of the magnetic field of the studied areas. Three types of anomalies associated with ravines are distinguished. Positive anomalies over ravines and step-type anomalies, in our opinion, are associated with tectonic movements, and negative anomalies are due to slope wash processes. Alternating magnetic fields in the studied areas may be due to ferruginized deposits.

Magnetic Mineralogical Analysis of Soils as a Part of the Integrated Geological and Geophysical Model for the Hydrocarbon Prospecting

Piriyev¹

2022

Magnetic minerals form or alter in the presence of hydrocarbons, making them a potential magnetic proxy for identifying hydrocarbon migration pathways. We concentrate in the precision magnetic mineralogical analyzes to understand what magnetic minerals in soil from the hydrocarbon fields are responsible for the magnetic signal. To illustrate the results of our studying, we consider the study area of the hydrocarbon deposits near the village Balabanivka, Bogodukhiv district, Kharkiv region. A collection of soil samples is represented by deep medium-humus chernozems. The thermomagnetic analyzes, hysteresis parameters, and isothermal remanent magnetization curves (IRM) were studied for the samples collected near the well (point PR 28) and at the area located out of the hydrocarbon influence zone (point PR 0403). To study the thermomagnetic parameters, different types of the magnetization and magnetic susceptibility (MS, χ), and hysteresis loops we used the Variable Field Translation Balance (VFTB) instrument. The results are confirmed by the highest values of the gas geochemical parameters. The MS variations at temperatures ranging from 200 to 400 ˚C may reflect the presence of either iron sulphides or maghemite. The magnetite occurs for all soils. The wasp-waisted hysteresis loops identified either a mixture of two magnetic minerals (magnetite and hematite) and the admixture of the superparamagnetic and larger grains of the same minerals.