The sandstone reservoir characteristics and controlling factors of Shanxi Formation and Lower Shihezi Formation in Southeastern Ordos Basin

The southeastern Ordos Basin hosts considerable resource potentials and contains significant hydrocarbon discoveries in the Shanxi Formation and Lower Shihezi Formation, making it a significant petroliferous exploration area. In this study, wireline logs, mud logs, cores, thin sections, scanning electron microscope, heavy minerals, porosity and permeability data, and grain size are employed to carry out research on reservoir differentiation characteristics and associated controlling factors in the Shanxi Formation and Lower Shihezi Formation. The results indicate that reservoir sandstone mainly includes lithic sandstone, quartz sandstone, and lithic quartz sandstone. The pore types are dominated by secondary intergranular pore, intragranular dissolution pore, followed by intercrystal pore and microcracks. The porosity and permeability attain 7.9% and 0.59 10(-3)mu m(2)respectively which shows low porosity and low permeability. The differences of sandstone reservoirs in the Lower Shihezi Formation and Shanxi Formation are controlled by tectonic movements, sedimentary environments, and diagenesis. Tectonic movements not only provide potential provenance but also reconstruct physical property. Sedimentary environments determine sandstone composition and texture and controls reservoir heterogeneity. The diagenesis affects the preservation, evolution, and development of reservoirs and determines the quality of physical property.