Abstract:

We have successfully collected the trace elements in natural gas by the airextracting method used in geogas survey in order to conduct the ecologic geochemical evaluation and the investigation of unconventional geochemical exploration for natural gas reservoirs. Fiftyone trace elements in the natural gas of west Sichuan were discovered by using the method of laser plasma spectral analysis. These trace elements are mainly the elements in the 4th, 5th, and 6th periods of the Periodic Table, and their attributes are alkali metals, alkalineearth metals, rare metals, transition metals, main group elements, halogen and nonmetals. The contents of Zn, Ca, K, Na, P, Cu, Mg, Ba, Pb and Fe make up 95% of the total. Among them, the contents of Zn and Ca are the highest, making up 56.7% of the total; the next elements having higher contents are K, Na, P and Cu. This discovery not only plays an important role in the investigation of the origin, the hydrocarbon source, the reservoirforming process and the utility of the natural gas，but also is of great significance for studying the ecologic environment above the gas field.

Key words:

natural gas; metal trace element; airextracting from gas; plasma spectral analysis; agricultural ecologic environment