TYPE AND ORIGIN OF MESOZOIC RESERVOIRS IN WESTERN DEPRESSION ZONE OF EAST CHINA SEA SHELF BASIN

Using the existing drilling, logging, and seismic data, this paper analyzed the stratigraphic and sedimentary characteristics of the Mesozoic depression belt of the Western Depression in the East China Sea Shelf Basin and made a comparison of reservoir types to the adjacent land area. On the basis, the types and origins of the Mesozoic reservoirs are discussed in order to provide the basis for comprehensive analysis of gas geological conditions and preferred direction for further exploration. The types of Mesozoic reservoirs found in the study area include sandstone reservoir, weathering-crust reservoir and volcanic rock reservoir. Among them, sandstone reservoir dominates. Cretaceous reservoirs are much better than the Jurassic. However, the sandstone reservoirs are strongly heterogeneous. The development of sandstone reservoirs depends upon its sedimentary environment. Fluvial, fan deltaic, and coastal environments are the main domains for sandstone reservoir to form. Weathering-crust reservoir and Volcano clastic rock reservoir are influenced by tectonic movement and structural highs are the favorable places for them to form.