Effects of Volcanic Activity on Organic Matter Enrichment in the Sediments and its Implications for Oil and Gas Exploration and Development

International School of Beijing, Anhua Street No.10, Shunyi, China

Abstract

Volcanic activity is an important geological phenomenon in the evolution and development of the earth and brings rich resources to benefit human society, such as geothermal resources, valuable minerals, petroleum, and natural gas, although volcanic eruptions cause serious threats to the ecological environment of our planet. The co-development of oil and gas and volcanic activity in the same basin is a common phenomenon globally. Volcanic activity can bring abundant nutrients into the basins, conducive to the development of algae and other microorganisms in the water body. After the death of organisms, their remaining settles down to the water bottom and accumulate in the sediments. Meanwhile, reducing gases, releasing along with the volcano eruption, including H2S, CO2, etc., result in anoxia in the water body, benefiting the preservation of organic matter at the bottom and brings a large amount of material basis for the generation of oil and gas. Additionally, volcanic activity and hydrothermal fluids are rich in acid substances, will dissolve part of the minerals in the formation, generates a large number of migration channels for oil and gas migration. Some volcanic rocks are rich in pores, making them natural tanks for oil and gas storage. However, volcanic activity also has destructive effects on oil and gas accumulation. High hydrothermal/volcanic input can dilute primary productivity or reduce the abundance of organic matter due to high deposition rates, while excessive volcanic activity or hydrothermal fluid input can introduce large amounts of sulfate into the water, causing strong bacterial sulfate reduction (BSR). The high consumption of organic matter can hamper the organic matter enrichment. Therefore, how to define appropriate volcanic activity conducive to organic carbon preservation, and to establish the relationship model between volcanic activity and organic matter enrichment, are key scientific issues.