Characteristics and Controlling Factors on Physical Properties of Yan 1012 Reservoirs in the Northern Maling Oilfield of the Erodos Basin

Based on data from thin sections,scanning electron microscope and mercury injection tests and physical property analysis,this work made a systematic study on characteristics and controlling factors of Yan 1012 reservoirs in the northern Maling oilfield of Shanxi Province. The results demonstrate that the reservoir sandstone is mainly composed of lithic feldspathic sandstones and feldspathic lithic sandstones which have the characteristics of high compositional maturity and medium or low texture maturity,and belongs to a low-porosity and low-permeability type. The main internal architecture is muddy intercalation and the main reservoir space is dominated by intergranular holes with highly heterogeneous microscopic pore structure. Major throats are the crucial factor for reservoir infiltrating ability. Different sedimentary facies zones resulted in the differences of physical properties and determined types and intensity of the late diagenesis. The strong compaction and cementation played a key role in forming low-porosity and low-permeability reservoirs. As constructive diagenesis,dissolution of feldspar and cuttings caused by the acidic water not only improved the reservoir space greatly,but also enhanced the pore connectivity. Microscopic pore structure can effectively reflect reservoir quality.