TYPES OF CENO-MESOZOIC PETROLIFEROUS BASINS IN EASTERN CHINA, AND ITS RELATIONSHIP WITH OIL AND GAS--BASED ON THE COMPACTION OF MUDSTONE

Based on a large number of data of the measured porosity of mudstone, the acoustic logging, and the X-ray diffraction analysis of clay minerials, the types of Ceno-Mesozoic basins, i.e. Sanshui, Miyang, Huanghua, in eastern China, and its relationships with oil and gas are studied. The authors proposed. 1. The compaction curve of mudstone can be used to estimate the denudation and calculate the depths of denudation of a basin or depression. The study shows that the degree of the denudation of the Ceno-Mesozoic basins in eastern China is decreased gradually from south to north. 2. According to the depths of denudation calculated by the compaction curve of mudstone, the Ceno-Mesozoic basins in eastern China can be divided into seriously denuded Sanshui compaction type and slightly denuded Huanghua compaction type. These two types correspond with the two sub-types, from the plate tectonic view point, i. e. the fault-down basin developed on the basis of large-scale of depression fold; and the fault-down basin developed on the basis of large scale of uplift fold, which were formed under extension in eastern China. 3. As to the serious denudation basins,the maximum buried depth of the strata must be restored and the history of oil-generation must be reestabli-shed according to the depth of denudation. 4. In the light of the mixed compaction zone of mudstone and montmori llonite-illite mixed layer zone of clay minerals, the favourable zone of hydrocarbon expulsion of a basin or depression can be defined. Together with the buried history of the basin or depression, the period of the primary migration of oil and gas can then be inferred.