Experiments on shallow-lacustrine deltaic sandstone in the Ordos Basin(Upper Paleozoic), Central China

Interval from the Shanxi Formation to member 8 of Lower Shihezi Formation in the Upper Paleozoic, Ordos Basin, central China, is one of the most important exploration targeted strata, which develops large area of shallow lacustrine deltaic sandstone and bears giant natural gas source. This study investigates the reservoir sandstone development and trys to build a physical model to perform sandstone internal structure analysis in an experimental basin equipped with a subsiding floor. A distorted model characterized by multi-sources, shallow-water and open system, is established which is integrated with tectonic evolution, palaeo-geomorphology, sediment sources and related components and so on. Through the adjusting of experimental parameters, such as inflow water volume, sediment supply, gradient, subsidence value and fluctuation of lake-level etc. during each stage of the experiments, we can reproduce and investigate multi-source big area shallow-lacustrine deltaic deposition. And we use double-direction intensive cross sections to discuss different characters of shallow water deltaic deposits at the position of near-source, middle part and distal. The results indicate that lake-level fluctuation and interplay of multi-direction sources are main controls during the development of large area shallow-lacustrine deltaic deposits. Meanwhile, both abundant sediment supply and suitable subsidence ratio also play an important role in this process. Shallow lacustrine delta front is not similar to traditional deltas with relative uniform foresets, but has complicated internal architecture. Finally, we also compare the physical simulation results with the real subsurface sedimentary strata and point out potential problems. ©, 2015, Science Press. All right reserved.