Research on Diagenetic Evolution and Hydrocarbon Accumulation Periods of Chang 8 Reservoir in Zhenjing Area of Ordos Basin

The Mesozoic Chang 8 Section in the Zhenjing area is a typical low permeability-tight sand reservoir and regarded as most important set of paybeds study area. Guided by principles basic geological theory, diagenetic evolution process hydrocarbon accumulation periods were determined through various techniques. More specifically, core observation, scanning electron microscopy (SEM), X-ray diffraction (XRD), vitrinite reflectance experiments performed combination with systematic studies on rock pyrolysis thermal evolutionary history basins, illite-dating method, so on. dominated feldspar lithic sandstones. Quartz, feldspar, fragments are major clastic constituents. In clay minerals, chlorite content highest, followed illite/smectite formation kaolinite, while illite lowest. diagenesis effect includes compaction, cementation, dissolution, metasomatism, rupturing. assumed sequence following: mechanical composition → early sedimentation mineral membrane cementation sparry calcite →authigenic kaolinite precipitation secondary production amplification quartz dissolution carbonate cement late minerals such ferrocalcite. Now, Stage A middle period. Through inclusion temperature measurements, conjunction dating analysis technology this was phase-I continuous epoch 105~125 Ma, which assigned to Middle Early Cretaceous Epoch.