Abstract:

Tectonic and sedimentary factors are of importance in controlling the formation and distribution of marine reservoirs.Confronted with the spreading of ocean basins and dispersing of plates from Sinian to the early period of Early Paleozoic(Z-O₂),sedimentary systems of stable platform-passive margin slope developed around the main plates of China such as Huabei,Tarim and Yangtze.Carbonate rocks of platform facies bloomed during that long period,and were mainly composed of limestone,grainstone and dolomite.The high-stand Ordovician is one of the main marine strata for hydrocarbon discoveries in China.Subduction of ocean basins and con-vergence of Paleo-China continent occurred during the late period of the Early Paleozoic(O₃-S).Along with retrogression,the central part of the plates uplifted and became erosion areas,around which marine elastic reservoirs were developed,such as the Silurian in the northern Tarim Basin and areas from west Hubei to east Chongqing.The Caledonian karstifieation imposed an important influence on the early diagenetic evolution of the Lower-Paleozoic carbonate reservoirs.From the Late Paleozoic to the Early Mesozoic(D-T),convergence dominated in northern China,where marine elastic reservoirs were mainly developed,such as the Carboniferous and the Permian in North China and Junggar basins and the Devonian in the Tarim Basin.The Lower Palaeozoic carbonate rocks underwent the major karstification during the Hercynian period.While divergence dominated in southern China,where the South China platform underwent tectonic dispersion and broke down into several smaller platforms surrounded by deep basins,with reservoirs of shoal and reef facies deposited on the edge of platforms.Under long and multistage tectonization,marine reservoirs lost primary porosity progressively;meanwhile, conjunction of karstification,hydatothermal erosion,dolomitization and fracture formed secondary porosity and improved marine reservoirs remarkably.

Key words: reservoir, tectonic and sedimentary condition, marine strata, Pre-Mesozoic, China