E.M. Chuvilin

Natural gas and gas hydrate accumulations within permafrost in Russia

Sudden natural gas blowouts from within the permafrost sections in West and East Siberia and some results of permafrost core samples study are presented. Topics covered include gas geochemistry, blowout intensity (gas flow rate), depth interval and permafrost rock peculiarities in places of these gas releases. Although microbial gas is widespread within permafrost, thermogenic gas can also occasionally migrate from deep gas reservoirs along faults, or be present locally in areas of gas reservoirs within the permafrost section. Gas can be preserved within permafrost in a free state as well as in hydrate form throughout the permafrost zone and be a potential threat to climate in the course of global warming.

Surface tension parameters of ice obtained from contact angle data and from positive and negative particle adhesion to advancing freezing fronts

From contact angle data obtained on flat ice surfaces with a number of liquids, combined with data on particle and macromolecule adhesion or non-adhesion to advancing freezing fronts, the apolar (Lifshitz-van der Waals or LW) and polar (Lewis acid-base or AB) surface tension (γ) components and parameters have been determined. At 0°C these are γLW iee = 26.9 and γAB ice = 39.6 mJ/m2. The latter consists of an electron-acceptor (γ⊕) and an electron-donor (γ⊖) parameter: γ⊕ = 14 and γ⊖ = 28 mJ/m2.

The degradation of submarine permafrost and the destruction of hydrates on the shelf of east arctic seas as a potential cause of the “Methane Catastrophe”: some results of integrated studies in 2011

On the basis of the analysis of published data and in the course of the authors’ long-term geochemical and acoustic surveys performed in 1995–2011 on the East Siberian shelf (ESS) and aimed to research the role of the Arctic shelf in the processes of massive methane outbursts into the Earth’s atmosphere, some crucially new results were obtained. A number of hypotheses were proposed concerning the qualitative and quantitative characterization of the scale of this phenomenon. The ESS is a powerful supplier of methane to the atmosphere owing to the continued degradation of the submarine permafrost, which causes the destruction of gas hydrates. The emission of methane in several areas of the ESS is massive to the extent that growth in the methane concentrations in the atmosphere to values capable of causing a considerable and even catastrophic warning on the Earth is possible. The seismic data were compared to those of the drilling from ice performed first by the authors in 2011 in the southeastern part of the Laptev Sea to a depth of 65 m from the ice surface. This made it possible to reveal some new factors explaining the observed massive methane bursts out of the bottom sediments.

Factors affecting spreadability and transportation of oil in regions of frozen ground

The physical behaviour of oil interacting with soils subjected to seasonal frost or permafrost was investigated. An experimental programme was carried out to investigate the transportation and spreading of oil on a frozen surface, and transportation and accumulation of oil into freezing or frozen soils. The results show that spreading of oil at the surface at air temperatures below freezing depends on oil composition, soil temperature, and the type of mineral surface. It was observed that an ice surface has the least spreading and the greatest wetting angle of the surfaces studied. The oil penetration into frozen soils depends on soil and oil composition and temperature conditions. It was observed, as expected, that oil accumulation in frozen soils decreases with increasing ice content in the pores. However, penetration of oil components is observed even in completely ice-saturated soils. Freezing of oil-saturated soils causes a redistribution of the oil components. In sandy soils, the oil concentrates in a thawed zone in front of the freezing front; in clay soils, the oil can accumulate in the frozen zone under certain temperature conditions. A summary of the influence of various factors affecting oil behaviour in frozen and freezing soils is presented based on the experimental data and published data from other authors.

An experimental investigation of the influence of salinity and cryogenic structure on the dispersion of oil and oil products in frozen soils

Abstract The migration of oil into disturbed soils from several regions of Russia, differing in dispersity, salinity, and cryogenic structure, was investigated. The soils were exposed to oil at negative temperature (−1.5, −7 and −20 °C) and the oil penetration was measured over at least 7 days and up to 180 days. The resulting oil complexes that penetrated into the ice-filled pores (G=0.85–0.95) was highly influenced by dispersity, salinity, cryogenic structure, and the nature of ice spreading in the frozen soil. Based on these results, the main determinant oil pollution migration in frozen soils is pore channels and microsplits that are partly filled with water and ice. Oil pore saturation takes place at the expense of capillary transfer and surface diffusion.

CARBON DIOXIDE GAS HYDRATES ACCUMULATION IN FREEZING AND FROZEN SEDIMENTS

The paper presents results of the experimental research on the process of CO2 gas hydrates formation in the porous media of sediments under positive and negative temperatures. The subject of research were sediment samples of various compositions including those selected in the permafrost area. The research was conducted in a special pressure chamber, which allowed to monitor pressure and temperature. Using the monitoring results it was possible to make quantitative estimation of the kinetics of CO2 hydrates accumulation in the model sediments. In the course of the research it was demonstrated, that active hydrates accumulation occurred in frozen sediments under negative temperatures (about -4 о С). At the same time a comparative analysis of СО2 and СН4 hydrates accumulation was made in the porous media of the sediment under negative temperatures. The performed experiments enabled to estimate an influence of temperature, sediment composition and water content on kinetics of CO2 hydrates accumulation in porous media. Besides, we made an estimation of the amount of hydrates, which could be formed in hydrates containing sediments at freezing of the remaining pore water.

Mechanism of frost heave by film water migration under temperature gradient

ConclusionsBased on the principle of freezing point superposition, a model for predicting unfrozen water content is worked out and it can consider the influences of five factors: soil variation, water content, temperature, solution concentration and overburden pressure. The difference of values between determination and calculation is less than 3 %.According to the curve of unfrozen water content vs. temperature and initial freezing point and temperature at the cold end of soil body, a way for estimating ice segregation temperature is presented. The difference of values between determination and calculation is less than 0.3°C.The thickness of frozen fringe changing with time has three models. The calculation method needs further study.

Combined CFD/Population Balance Model for Gas Hydrate Particle Size Prediction in Turbulent Pipeline Flow

A combined computational fluid dynamics/population balance model (CFD‐PBM) is developed for gas hydrate particle size prediction in turbulent pipeline flow. The model is based on a one‐moment population balance technique, which is coupled with flow field parameters computed using commercial CFD software. The model is calibrated with a five‐moment, off‐line population balance model and validated with experimental data produced in a low‐pressure multiphase flow loop.

EXPERIMENTAL METHOD FOR DETERMINATION OF THE RESIDUAL EQUILIBRIUM WATER CONTENT IN HYDRATE-SATURATED NATURAL SEDIMENTS

The equilibrium “pore water in sediment–gas hydrate-former–bulk gas hydrate” was experimentally studied. This residual pore water corresponds to a minimal possible amount of water in the sediment, which is in thermodynamic equilibrium with both gas and the bulk hydrate phase. This pore water can be defined as non-clathrated water by analogy to unfrozen water widely used in geocryological science. The amount of non-clathrated water depends on pressure, temperature, type of sediment, and gas hydrate former. The presence of residual pore water influences the thermodynamic properties of hydrate-saturated samples. The paper’s purpose is to describe a new experimental method for determining the amount of non-clathrated water in sediments at different pressure/temperature conditions. This method is based on measuring the equilibrium water content in an initially air-dried sediment plate that has been placed in close contact with an ice plate under isothermal, hydrate-forming gas pressure conditions. This method was used to measure the non-clathrated water content in kaolinite clay in equilibrium with methane hydrate and CO2 hydrate at a temperature of –7.5 o C in a range of gas pressures from 0.1 to 8.7 MPa for methane and from 0.1 to 2.5 MPa for CO2. Experimental data show that at the fixed temperature the non-clathrated water in hydrate-containing sediments sharply reduces when gas pressure increases. The experiment demonstrates that the non-clathrated water content strongly depends on temperature, the mineral structure of sediment, and the hydrate-forming gas.

CO2 Capture by Injection of Flue Gas or CO2–N2 Mixtures into Hydrate Reservoirs: Dependence of CO2 Capture Efficiency on Gas Hydrate Reservoir Conditions

Injection of flue gas or CO2-N2 mixtures into gas hydrate reservoirs has been considered as a promising option for geological storage of CO2. However, the thermodynamic process in which the CO2 present in flue gas or a CO2-N2 mixture is captured as hydrate has not been well understood. In this work, a series of experiments were conducted to investigate the dependence of CO2 capture efficiency on reservoir conditions. The CO2 capture efficiency was investigated at different injection pressures from 2.6 to 23.8 MPa and hydrate reservoir temperatures from 273.2 to 283.2 K in the presence of two different saturations of methane hydrate. The results showed that more than 60% of the CO2 in the flue gas was captured and stored as CO2 hydrate or CO2-mixed hydrates, while methane-rich gas was produced. The efficiency of CO2 capture depends on the reservoir conditions including temperature, pressure, and hydrate saturation. For a certain reservoir temperature, there is an optimum reservoir pressure at which the maximum amount of CO2 can be captured from the injected flue gas or CO2-N2 mixtures. This finding suggests that it is essential to control the injection pressure to enhance CO2 capture efficiency by flue gas or CO2-N2 mixtures injection.