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Characteristics of Carbonate Cements and Their Effects on Properties in Chang 8 Sandstone Reservoir, Ordos Basin

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Authors:Li Yang; Zhang Wenxuan; Li Shutong; Luo Anxiang; Mou Weiwei; Deng Xiuqin; Yan Cancan; Hui Xiao
Author Affiliations:Primary:
Chinese Academy of Sciences, Institute of Geology and Geophysics, Beijing, China
Changqing Oilfield Company, PetroChina, China
Volume Title:Dizhi Keji Qingbao Geological Science and Technology Information
Source:Dizhi Keji Qingbao = Geological Science and Technology Information, 37(4), p.175-183. Publisher: China University of Geosciences, Wuhan, China. ISSN: 1000-7849
Publication Date:2018
Note:In Chinese with English summary
Summary:In order to verify the characteristics of carbonate cements and their effects on reservoir properties, the potassium ferricyanide and alizarin red staining slices, cathodoluminescence and carbon and oxygen isotopes, were used to study the mineralogical and geochemical characteristics of carbonate cements in Chang 8 reservoir. The research results show that there are three periods of carbonate cements developed mostly. The first period of carbonate cements is mainly calcite, with δ13C ranging from -3.7per mill to -2.4per mill and δ18O about -10per mill. Its formation is related to the over saturation of calcium carbonate in alkaline lake water, formed in penecontemporaneous to early diagenetic stage. The second period of carbonate cements is ferrocalcite, with δ13C ranging from -14.8per mill to -4.1per mill and δ18O-21.0per mill to -13.2per mill. This is mainly due to the decarboxylation of organic matters during the period B of early diagenetic stage to period A of middle diagenetic stage. The third period of carbonate cements is mainly ferrodolomite and ferrocalcite, formed in the period B of middle diagenetic stage, with δ13C being -9.5per mill to -5.5per mill and δ18O, -25.7per mill to -22.3per mill. This is affected by both organic carbon from the thermal evolution of organic matter and inorganic carbon formed by dissolution of carbonate cement in the early stage. Theoretical quantitative calculation shows that the porosity of Chang 8 reservoir is decreased about 5.06% by carbonate cement, with the loss rate of 12.05%-12.95%. The result has a reference to the prediction of favorable reservoirs.
Record ID:855495-23
Copyright Information:GeoRef, Copyright 2021 American Geosciences Institute.
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