V. Blinova

First sampling of gas hydrate from the Vøring Plateau

Methane hydrate is a clathrate, an ice-like solid formed from methane and water, that is stable under conditions of pressure and temperature found in most of the worlds oceans at depths greater than a few hundred meters. Hydrate occurs beneath the seabed where there is sufficient methane to exceed its solubility in water within the hydrate stability field. It has been speculated that methane released from hydrate by climate-induced changes in pressure and temperature escapes into the ocean and into the atmosphere, where its acts as a greenhouse gas. Further, methane from beneath the seabed is the primary energy source for communities of chemosynthetic biota at the seabed.

The structure and genesis of limestones at the boundary between the Abalak and Bazhenov formations in Central West Siberia

In the central West-Siberian basin, fractured and cavernous carbonate rocks that are often oilbearing, which are referred to as correlation layer 1 (CL1), are frequently present at the top of the Abalak formation and/or at the bottom of the Bazhenov formation. They are sporadically distributed over the profile and the area; their genesis is still not completely clear. The structural features and oil-bearing capacity of carbonate rocks have been studied, as well at the distributions of carbon and oxygen stable isotopes from bulk rocks and calcite filling fractures in the CL1 layer that was penetrated by six wells. The spherolitic microstructure of limestones together with the carbon and oxygen isotope distributions (δ13C =–14 to–26‰ VPDB; δ18O = 0 to–5‰ VPDB) indicate the precipitation of carbonate material due to microbial activity on the surface and/or in the upper part of sediments at high methane concentrations. The fractures and caverns in limestones are frequently oil-bearing; they contain coarse crystals of calcite, pyrite, quartz, and, more rarely, barite. This degree of mineralization and the isotope composition of calcite oxygen (up to–18‰ VPDB) indicate that calcite precipitates at elevated temperature (up to 120°C) from the hydrothermal fluids that could migrate from underlying strata.

Stable carbon and oxygen isotopes distribution in carbonates from the Central Barents Sea shelf sediments

Carbonate macrofaunal remains and diagenetic tubes collected from a number of structures in the Central Barents Sea area during the 18th TTR (Training Through Research) cruise were subdivided into three groups according to the results of stable carbon and oxygen isotopes analysis. The first group includes carbonates that were formed from bicarbonate only from surrounding sea waters. The carbonates of the second group were formed during diagenesis with use of mixed sources of bicarbonate. The fourth group includes methane-derived carbonates that were formed as a result of anaerobic oxidation of methane (AOM).

Using the Dynamics of Bottom Simulating Reflector (BSR) for Prediction of Gas Hydrate Content in Marine Sediments

An approach to prediction of properties of gas hydrate bearing sediments basing on the dynamics of seismic waves reflected from the bottom of the hydrate-containing layer (BSR reflection) without well information is proposed. The approach was tested on synthetic data and demonstrated accurate prediction of gas hydrate content in pore space above the BSR as well as free gas content in pore space below the BSR, with the solution being robust to random noise in the reflection amplitude values. The proposed approach was also tested on the real data from the Black Sea. The results obtained (average gas hydrate content of ~43% and average free gas content of ~1.3% of pore space) match to the previously published results from the adjacent areas.