Water is ubiquitous in the rocks of the Earth's crust, and acts as an important component in many chemical reactions. However, the role of water in oil and gas generation has rarely been addressed. Xiaofeng Wang at the Chinese Academy of Sciences in Lanzhou and co-workers1 have shown that the presence of water increases the production of natural gas from coal.
Previously, hydrogen was thought to originate only from organic matter itself, but this method cannot account for all the hydrogen needed to make hydrocarbons such as oil and gas. To investigate whether water provides the extra hydrogen, Wang and co-workers ground up Jurassic lignite (brown coal) from the Shenshan coal field in China's Ordos Basin and performed experiments on it at high pressures and temperatures of 250 °C to 550 °C, with and without water.
The researchers found that when water was present, the production of carbon dioxide, hydrogen and hydrocarbons, such as methane, was enhanced, especially at higher temperatures. The presence of water also affected the levels of deuterium (heavy hydrogen) and carbon-13 isotopes, proving that water is directly involved in chemical reactions during gas generation.
The findings show that hydrogen release is just as important as hydrogen consumption during the natural generation of hydrocarbons.
（The authors of this work are from:
Key Laboratory of Gas Geochemistry, Chinese Academy of Sciences, Lanzhou, China; Research Institute of Petroleum Exploration and Production, SINOPEC, Beijing, China. ）
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