Porosity origin and controlling factors of sandstone and conglomerate reservoir of the Upper Paleozoic in central Ordos Basin
Si Chunsong1, Shou Jianfeng2, Wang Shaoyi2, Wu Dongxu2
1 Faculty of Earth Resources, China University of Geosciences（Wuhan），Wuhan 430074，Hubei 2 Hangzhou Institute of Petroleum Geology，PetroChina，Hangzhou 310023，Zhejiang
Abstract：Gas productivity of the Lower Permian Shanxi and Xiashihezi Formations in the Ordos Basin is controlled mainly by reservoir property.Understanding the porosity origin and its controlling factors is a critical step in predicting the distribution of reservoir.Integrated analysis of porosity characteristics，mineral solubility and pore textures shows that reservoir space for sandstones and conglomerates in the Member 2 of Shanxi Formation is mainly primary porosity，while that for the Member 8 of Xiashihezi Formation is mainly dissolution porosity.Reservation of primary porosity and creation of dissolution porosity are constrained by detrital component，grain size，and silica origin，i.e.coarse quartzose sandstones and conglomerates in the Member 2 of Shanxi Formation are favored by their strong resistance to compression，absence of dissoluble components，and multiplicate origin of silica;coarse lithic sandstones and conglomerates in the Member 8 of Xiashihezi Formation are prone to be dissolved due to their abundant dissoluble components and organic acid.This study indicates that reservoirs with 8％～18％ of dissoluble components possess the highest dissolution porosity.Porosity genetic types correlate well with pore textures，i.e. reservoirs with primary pores are of higher permeability than those with dissolution pores at the same porosity.
Si Chunsong,Shou Jianfeng,Wang Shaoyi et al. Porosity origin and controlling factors of sandstone and conglomerate reservoir of the Upper Paleozoic in central Ordos Basin[J]. JOPC, 2012, 14(4): 533-542.
