(1) China University of Geosciences, Wuhan City, China
(2) China University of Geosciences, China
(3) China University of Geosciences
(4) Chengdu Institute of Technology, Chengdu, China
Abstract: A study of relationship between magnetic, geochemical and mineralogical anomalies and hydrocarbon microseepage above the Jingbian Gas Field, Ordos Basin in China
Ordos Basin is a large-scale oil-and gas-bearing basin in central China. In recent years, large areas geochemical exploration has conducted in the Ordos Basin which played an important role in the development of the Jingbian Gas Field. The sampling profile of cross through gas field is 116 km long and 117 samples at a interval of 1 km are sampled. The sampling depth is about 1.5-2.0 m and the lithology of samples are dominantly sand and subsand.
Measurements of magnetic and geochemical parameters of samples indicate that there is obvious direct correlation between magnetic (susceptibility, saturation magnetization and saturation remanent magnetization) and geochemical anomalies (total hydrocarbon, heavy hydrocarbon and alteration carbonate) and average linear correlating coeffcient between them get ut to 0.95 above gas field.
X-analysis results shows that the major magnetic mineral in samples is magnetite. High temperature trace elements content of magnetite in samples above gas field are very low and TiO2 content is the lowest by electric probe. Thus, we infer that the magnetite in soil from the Jiangbian gas field, Ordos Basin is low temperature diagenetic magnetite associated with hydrocarbon migration. High magnetic anomalies above gas field are magnetic alteration zones due to geochemical effect related with subssurface strong hydrocarbon microseepage in this region.
AAPG Search and Discovery Article #90914©2000 AAPG Annual Convention, New Orleans, Louisiana