Abstract:

According to the methane,heavy hydrocarbons and mean ΔC measured with acidolytic hydrocarbon method,and variation coefficient,the geochemical fields in China's major petroliferous basins can be classified as high,medium and low ambient fields,as well as highly non-homogeneous,non-homogeneous and homogeneous fields.As a whole,the geochemical fields of the petroliferous basins in western China(to the west of Ordos and Sichuan basins) are higher than that of the petroliferous basins in eastern China,and that of petroliferous basins in northeastern China is lower than that of the petroliferous basins in central China but higher than that of the petroliferous basins in southern China.In addition to the petroleum geologic conditions,the main causes are also related with the properties of near surface sediments and the geographical and geomorphologic landscape conditions.Based on the results of nation-wide geochemical reconnaissance surveys,and combined with the composite features of geochemical prospecting anomalies in the proven oil and gas reservoirs,areas with strong local composite anomaly and good consistence of various indexes in relatively under-explored regions are selected as prospective areas,including Changling fault depression in the southern end of central depression,western slope,and Qianjiadian fault depression in southwestern uplift of Songliao basin,Tanzhuang-Shenqiu depression in Zhoukou basin,Xiaman-Manrima-Awancang anomaly zone in Songpan-Aba region,and Wuwei-Hexian and Wangjiang anomaly zones in Lower Yangtze region.Twenty five plays have further been subdivided based on the results of geochemical prospecting in 7 basins(or regions).

Key words: geochemical exploration of oil and gas, anomaly, geochemical field, prospective area, play, petroliferous basin