RESEARCH ON GEOCHEMICAL EXPLORATION TECHNIQUE FOR NATURAL GAS IN THE NORTHEASTERN SICHUAN AREA

The hydrocarbon gases-oriented geochemical exploration technique has the advantage of quickness,effectiveness and low cost,and may play active roles in natural gas exploration.Some experiments and researches,including experiments for sample-collecting methods,researches on the effectiveness and the repeatability of the geochemical indicators,have been made in the Puguang Gasfield and Yuanba Block in the Northeastern Sichuan Experimental Area in order to select the effective geochemical indicators suitable for the surface and geological conditions of the study area.As the result,the geochemical indicators of headspace hydrocarbon,acid-extraction hydrocarbon and heat-released hydrocarbon of the common surface residual soils caused by the weathering of the red Jurassic mudstones have been selected.The results show that when the high concentration values,the accumulation factor,and the dryness degree(C₁/C₂+) of these hydrocarbons are used to determine the main anomaly,they can quickly identify the favorable accumulation area for natural gases,and have already achieved good prediction effects in Yuanba Block.