DOI: 10.24412/2076-6785-2023-6-23-30
Abstract
Laboratory studies of cores from carbonate formations in Eastern Siberia have their own difficulties. These include high mineralization of formation water, anhydritization, presence of heavy hydrocarbons and bitumen in the reservoir rock. At present, there are no reliable criteria for identifying bitumen when interpreting standard methods of geophysical well studies. Of great practical interest is the use of nuclear magnetic resonance (NMR) to describe the characteristics of fluid saturating reservoirs with heavy oil. The combination of petrophysical (NMR, determination of preserved water saturation by extraction-distillation method on Dina-Stark apparatus) and pyrolytic methods allows to characterize bituminous samples, as well as to determine boundary cutoffs of T2 times separating bitumen, bituminous and heavy oil fractions from free pore space. The obtained T2 time boundary cutoffs are applied to the nuclear magnetic logging curves. A good comparison of porosity attributable to free pore space and porosity attributable to bitumens and heavy oil fractions from core data and NMR logging data is obtained. In addition, the article
describes experiments to determine the hydrogen index of bitumen and proposes a value of hydrogen index recommended for practical tasks of interpretation methods of geophysical well studies.
Materials and methods
In the laboratory it is possible to obtain information about bituminosity by methods of petrography (visual study of slits), geochemistry (pyrolytic studies) and petrophysics (gas-volumetry, liquid saturation, NMR), but these methods are not without disadvantages. The developed method based on a comprehensive analysis of laboratory studies allows us to estimate the volume of pores occupied by bitumen, as well as to determine the boundary cutoffs that allow us to estimate the fraction of pores occupied by a particular fluid, which can be further used in the interpretation of nuclear magnetic logging.
Keywords
core, bitumen, total porosity, NMR, T2 time boundary cutoffs, hydrogen index
