Reservoir sandstones and their physical properties of the Chang-6 oil measures in the Yanchang Formation, Huaqing region, Ordos Basin

The emphasis of this study is placed on the types and characteristics of the reservoir sandstones and their bearings on physical properties of the Chang-6 oil measures in the Yanchang Formation, Huaqing region, Ordos Basin. The reservoir sandstones are represented by lithic feldspathic sandstone with finer grain sizes and moderate to poor sorting. The interstitial materials contain carbonate minerals and clay minerals. The physical properties of the reservoir sandstones are progressively getting better in response to the increase of quartz contents, while worse with the increase of lithoclastic contents. The dissolution of feldspar from the sandstones is believed to be a key factor for the improvement of the physical properties. The higher contents of the interstitial material give rise to the plugging and filling of pore throats, and thus result in the deterioration of the physical properties.