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The level of scientific knowledge about a gas hydrate deposit (GHD) in the northern deep-water part of the Bulgarian Exclusive Economic Zone (BEEZ), energy, climate and environmental problems determine the need of urgent creation and realization of a Bulgarian program for gas hydrate development. We present a review of this knowledge and define 3 preliminary steps for funds optimizations and fast creation and implementation of pilot and innovative economically profitable technologies for fuel production (CH4 and/or H2) with low geohazard and environmental risk and negative carbon footprint on the atmosphere.

The aim of this work is to reconstruct the variations of the total gas hydrate (GH) masses of the Danube deep-sea fan after 0.265 Ma BP. The PetroMod™ model developed in GEOMAR, Germany is for basin analysis of the Western Black Sea for 98 Ma. Geological structure is from 2D seismic of the Black Sea consortium “Geology without limits”. Results show a trend for total GH masses decrease after Middle Pleistocene and the role of the GHs as sink and source of methane.

Focused fluid flow shapes the evolution of marine sedimentary basins by transferring fluids and pressure across geological formations. Vertical fluid conduits may form where localized overpressure breaches a cap rock (permeability barrier) and thereby transports overpressured fluids towards shallower reservoirs or the surface. Field outcrops of an Eocene fluid flow system at Pobiti Kamani and Beloslav Quarry (ca 15 km west of Varna, Bulgaria) reveal large carbonate‐cemented conduits, which formed in highly permeable, unconsolidated, marine sands of the northern Tethys Margin. An uncrewed aerial vehicle with an RGB sensor camera produces ortho‐rectified image mosaics, digital elevation models and point clouds of the two kilometre‐scale outcrop areas. Based on these data, geological field observations and petrological analysis of rock/core samples, fractures and vertical fluid conduits were mapped and analyzed with centimetre accuracy. The results show that both outcrops comprise several hundred carbonate‐cemented fluid conduits (pipes), oriented perpendicular to bedding, and at least seven bedding‐parallel calcite cemented interbeds which differ from the hosting sand formation only by their increased amount of cementation. The observations show that carbonate precipitation likely initiated around areas of focused fluid flow, where methane entered the formation from the underlying fractured subsurface. These first carbonates formed the outer walls of the pipes and continued to grow inward, leading to self‐sustaining and self‐reinforcing focused fluid flow. The results, supported by literature‐based carbon and oxygen isotope analyses of the carbonates, indicate that ambient seawater and advected fresh/brackish water were involved in the carbonate precipitation by microbial methane oxidation. Similar structures may also form in modern settings where focused fluid flow advects fluids into overlying sand‐dominated formations, which has wide implications for the understanding of how focusing of fluids works in sedimentary basins with broad consequences for the migration of water, oil and gas., Integrated School of Ocean Sciences (ISOS) Kiel, European Union’s Horizon 2020 http://dx.doi.org/10.13039/100010661, Bulgarian Science Fund

We propose a new possible earthquake precursor, a coastal water jet originating from shallow water gas seeps and colored by sediments, lifted from increased gas seeps emissions, preceding some earthquakes with offshore epicenters along the Bulgarian Black Sea coast and M ≥ 3. The new possible earthquake precursor is site specific and may be observed in shallow coastal water regions where active faults are accompanied by hydrocarbon gas seeps. We point out to a region where it can be easily detected by direct observation and satellite remote sensing, Zelenka methane seeps (ZMS), near the Bulgarian Black Sea coast. The ZMS activation is related to the tectonic stress and fracturing preceding and accompanying the earthquakes in the Shabla-Kaliakra-Balchik region along the northern part of the Bulgarian Black Sea coast. We also propose an earthquake forecasting experiment, based on the following four hypotheses: 1) The change of the methane emission of shallow horizons is related to crustal strain changes preceding earthquakes in the region; 2) extreme change of the activity of underwater methane seepages appears immediately before nearby earthquakes; 3) shallow water methane seepages activity can be monitored by remote sensing; 4) satellites can register effects from an extreme increase in their emissions. The proposed earthquake forecasting experiment is based on the monitoring of methane seepages activity in the ZMS area by direct observation and remote sensing which may provide indication for preparatory earthquake activity preceding offshore earthquakes in the region.

The aim of Stage 1 of the FNI project GEOHydrate is to prove the hypothesis that gas hydrates deposits (GHDs) create measurable temperature and heat flow (T&HF) anomalies on the seafloor. We use a PetroMod™ model for 98 Ma basin analysis of the Western Black Sea basin, developed in GEOMAR, FRG. The model was run 2 times – with and without GH formation. The resultant difference of the heat flows on the seabed shows average heat flow anomaly above GHDs of 7 mW/m2 and a maximum of 15 mW/m2.