Discovery of the Metal Trace Elements in Natural Gas and Its Ecological Environment Significance

In order to conduct the ecological geochemical evaluation and the investigation of unconventional geochemical exploration in natural gas reservoirs, the authors introduced the method of air-extracting for geogas survey for the first time and successfully collected the trace elements in natural gas. Fifty-one types of trace elements in the natural gas of west Sichuan are discovered by the method of plasma spectral analysis. These trace elements mainly appear in periods 4, 5, 6 of the Elements Periodic Table, and the attribute of them are alkali metals, alkaline-earth metals, rare metals, transition metals, main group elements, halogen, and nonmetals. The contents of metal trace elements (such as Zn, Ca, K, Na, P, Cu, Mg, Ba, Pb, Fe, and so on) make up 95% of the total. Among them, the content of Zn and Ca are the highest, making up 56.7% of the total; K, Na, P, and Cu are the secondary. This discovery not only plays an important role in the investigation of the origin, hydrocarbon source, reservoir-forming process, and utility of natural gas but also is of important significance for studying the ecological environment above the gas field.