Marine methanogenesis

The EU’s fit-for-55 climate package aims to curb greenhouse gas emissions by 55%, by year 2030, ultimately becoming carbon neutral by 2050. Notwithstanding, natural gas and especially biogenic natural gas is increasingly becoming an important energy source worldwide and for Europe as it is more environmentally friendly compared to oil and coal. Natural gas is categorised into thermogenic gas, generated from oil, and into biogenic natural gas (BNG), produced from a class of bacteria called methanogens that thrive under anoxic conditions. One of the main differences between the two classes of natural gas is the amount of methane (CH4). Biogenic natural gas is purer with a methane content often exceeding 95% compared to thermogenic gas, which has a significant fraction of condensates.

Under certain conditions, biogenic natural gas is generated as a by-product of methanogens that coexist and depend on the chemical reactions from a series of other bacteria that reduce sulphates and ferment the organic matter during the decomposition of the organic matter (Fig. 1) . Previous research has revealed that biogenic natural gas is created at depths shallower than 1,000 m below the seabed fostered by certain factors such as a minimum TOC of 0.5%, in the absence of or at low levels of sulphates, at temperatures ranging between 20°C to 75°C, at burial rates ranging from 200 to 1000 m/Ma and pore space between 1 to 10 μm.

Organic Matter (OM) which yields biogenic gas follows a different pathway than conventional hydrocarbons which are produced from kerogen. The Kerogen Organic Matter (KOM) exbibits certain mechanisms which preserve the OM that consists of about 60% of TOC while the remaining OM, called hydrolysable (HOC), makes-up the remaining 40% of the TOC. This HOC constitutes the cornerstone of the generation of biogenic natural gas.

Fig. 1. The process of methanogenesis.

Combining the interpretation of seismic sections and stratigraphic modelling in the East Med, this research project aims to elucidate the process of methanogenesis. Primarily, it intends to formulate new biogenic natural gas system models which will help explain the conditions that permit methanogens to generate commercial size accumulations of biogenic natural gas. Geographically, the study will focus in the eastern Mediterranean basins of Herodotus and Levant with special attention on the gas fields of Aphrodite, Leviathan, Glaucus and Zeus.

Project details. The marine methanogenesis project is funded by the Cyprus Ministry of Energy, Commerce and Industry.

Research team: Mr Christos Christoforou, Dr Constantinos Hadjistassou.

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