Gas chimneys in the northwestern part of the Black Sea Basin: Nature and seismic interpretation

Gas chimneys are geological structures that represent vertical, columnar features through which gases from deeper levels of the Earth’s crust rise toward the surface. They are primarily composed of methane and water, sometimes mixed with sedimentary material. Typically formed in sedimentary basins, gas chimneys can indicate potential natural gas and oil deposits underneath. Seismic methods are commonly used to detect gas chimneys by identifying anomalies in rock sequences, often through the seismic noise generated by gas flows. These structures are characterized by the migration of gas (mainly methane) from deeper sedimentary formations to shallower levels, occasionally reaching the seafloor as noticed in the Bulgarian part of the NW Black Sea region. The maximum depth at which seismic records indicate gas chimneys is within Cenozoic sediments in the area of interest.