Phase Composition and States of Water-Hydrocarbon Fluids at Elevated and High Temperatures and Pressures (Experiment with the Use of Synthetic Fluid Inclusions)

Abstract

The article considers new approaches and methods for studying the phase composition and states of aqueous-hydrocarbon fluids in the temperature range of 240–700 °C and pressures of 5–150 MPa respectively. The essence of the approach is to conduct experiments in autoclaves on the formation of aqueous-hydrocarbon fluids through the interaction of hydrothermal solutions with bituminous and high-carbon rocks, as well as with crude oil. Simultaneous, in the same autoclaves, the quartz crystals and less other minerals with trapped aqueous-hydrocarbon inclusions are growing. These inclusions are the main objects of research that are carried out using modern micro thermometry methods, especially in combination with conventional and high-temperature FT-IR spectroscopy and microscopy with UV and natural light. This allows in situ monitoring of changes in the phase composition and states of aqueous-hydrocarbon fluids in a wide range of PT-parameters, to determine the effect of temperature and volume ratios of water and hydrocarbon (liquid and gas) phases on the occurrence of multiphase, three-phase and biphasic heterogeneous liquid and gas-liquid phases and homogeneous fluids. Studies have shown that with certain compositions of synthetic aqueous-hydrocarbon inclusions at heated and cooled is often appeared so-called imaginary homogenization in inclusions. This event associated with the periodic alignment of the refractive indices and densities of the aqueous and hydrocarbon liquid phases. The influence of the volume ratios of the aqueous and hydrocarbon phases on the cessation of cracking and metamorphic transformations of oil when the fluid goes into a homogeneous supercritical state, and the resumption of these processes after fluid heterogenization as a result of the temperature drop were established. In addition, a comparison of the effect of the PT-condition on the phase composition and the state of the hydrocarbon made it possible to estimate the maximum depths of the oil in the Earth’s interior. Depending on the volume ratios of the water and oil phases this depth turned out to be equal from 14 to 22 km.