Assessing thermal maturity of organic-rich Maykop facies in the Western Black Sea

Based on 3-D modelling The Black Sea oil& gas potential

Significance 

The Black Sea developed as part of the Alpine-Himalayan folded belt overlying newly formed oceanic or thinned pre-Cretaceous crust. During its formation, a thick sedimentary sequence in the western part of the basin comprising of clearly defined units starting at the Upper Cretaceous was buried. Recent research has revealed that much of this buried organic matter is being transformed into petroleum components such as oil and gas. In fact, there is direct evidence of this active petroleum system, i.e. oil reservoirs being encountered in deep and shallow-water locations, mud volcanoes, gas seepage sites and gas hydrate deposits. Moreover, it has been recently suggested that large amounts of thermally reactive organic matter have been exposed to sufficiently high temperatures and consequently converted into mobile hydrocarbons. The free gas presence in marine sediment of the Black Sea is confirmed by the observed Bottom Simulating Reflectors (BSRs) often associated with gas hydrate deposits located directly above. BSRs are widely present in the western Black Sea basin; however, their presence does not provide any quantitative information on the free gas accumulations located directly beneath.

Present-day hydrocarbon budget of the Western Black Sea Based on the present-day steady-state conditions assuming a bottom water temperature of 9 °C and the pore water salinity of 3, the upper limit of the gas hydrate stability zone (GHSZ) coincides with a water depth of about 665m. However, due to transient temperature profiles in the sub-surface and the sediment deposition history, multiple BSR levels have been observed. Therefore, as methane gas can be formed in both biogenic as well as thermogenic processes, it is necessary to distinguish between these two sources. To address this, German researchers from the GEOMAR Helmholtz Centre for Ocean Research Kiel: Dr. Ewa Burwicz and Dr. Matthias Haeckel, designed a new application of 3-D numerical modelling to estimate the total amounts of both biogenic and thermogenic methane gas and other petroleum components. Their work is currently published in the research journal, Marine and Petroleum Geology.

The researchers used the commercial petroleum software PetroMod®, to reconstruct the entire depositional history of the Western Black Sea basin to assess basin-scale estimates of organic matter maturation, petroleum component generation and expulsion from the source rock, as well as migration and accumulation. Through this spatio-temporal reconstruction, they investigated the main factors leading to the present-day methane gas budget and its distribution in the hosting marine sediments. In addition, the model was able to estimate the rates and total amounts of the in-situ biogenic methane generation and thermally-driven organic matter maturation in the source rocks. In summary, the Burwicz-Haeckel study presented a novel numerical model for reconstructing the depositional history (98–0 Ma) of the Western Black Sea sub-basin. Most important, the amount of biogenic methane generated on a basin scale almost doubles the amount of its thermogenic equivalent (~3,100 Gt and ~1,560 Gt, respectively) due to insufficient thermal maturation of the organic-rich Maykop facies at present.. Overall, their findings were in agreement with the isotopic composition of methane reported for the region and other modeling studies.

About the author

Dr. Ewa Burwicz is a post-doctoral researcher specialized in numerical modelling and marine geology working at the GEOMAR Helmholtz Centre for Ocean Research Kiel. After receiving her MSc degree in geology at the Jagiellonian University in Cracow, she moved to Germany and accomplished her PhD at the GEOMAR Helmholtz Centre for Ocean Research Kiel and the Christian-Albrechts-University of Kiel in 2015. Two years later, she received an outstanding PhD award for the past three years worldwide in the field of natural gas hydrate research from the international gas hydrate community (ICGH). She has worked in joint academia-industry projects on conventional and unconventional energy resources such as gas hydrates. She is specialized in developing multi-phase reaction-transport and 3D basin models to study large-scale fluid and gas circulation patterns, source rock maturation, and petroleum components generation throughout the basin history.

In her work, she combines data from various sources e.g. seismic and lithostratigraphic interpretations, geochemical analyses, and drill data to represent the full complexity of natural environment. In combination with deep learning methods, she studies global key element cycles and predicts global geochemical fluxes at the sediment-ocean interface as well as the energy limitations for deep biosphere. Since 2018, she is a member and a post-doc representative to the Women Executive Board (WEB) at GEOMAR to promote and facilitate equal opportunities and long-term career development for female scientists.

About the author

Dr. Matthias Haeckel is a senior scientist for marine biogeochemistry at the GEOMAR Helmholtz Centre for Ocean Research Kiel. He studied Chemistry at the Christian-Albrechts-University of Kiel, Germany, where he received his doctoral degree in the faculty of Geology-Paleontology in 2000. In 2001 he was awarded the Feodor-Lynen Fellowship of the Alexander-von-Humboldt Foundation to work in the Department of Oceanography at Dalhousie University in Halifax, Canada. In 2005 he took up a position in the research unit ‘Marine Geosystems’ at GEOMAR. He has participated in more than 20 research cruises in the world’s oceans and was principal investigator and coordinator of several German and European large-scale collaborative research projects on gas hydrates, CCS, and deep-sea mining.

He is a member of the Strategy Group on “Marine Mineral Resources” of the Konsortium Deutsche Meeresforschung and of the Technical Working Group on “Baseline Data” of the Legal and Technical Commission of the International Seabed Authority. In his research he combines field work with numerical thermodynamic and transport-reaction modelling, high-pressure experiments, and spectroscopic techniques to entangle and quantify natural biogeochemical processes in the marine environment and how they are altered by anthropogenic uses of the ocean. The primary research topics are the global carbon cycle, cold vent & gas hydrate systems, the determination of fluid & gas sources, and applied topics, such as methane hydrate exploitation, sub-seabed CO2 storage, mining of marine minerals, and pollution with chemical substances (e.g. plastic polymers).

Reference

Ewa Burwicz, Matthias Haeckel. Basin-scale estimates on petroleum components generation in the Western Black Sea basin based on 3-D numerical modelling. Marine and Petroleum Geology, Special Issue ‘Black Sea Gas Hydrates’ 113 (2020) 104122.

Go To Marine and Petroleum Geology, Special Issue ‘Black Sea Gas Hydrates

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