Research advances,geological implication and application in Ordos Basin of the “pore-size controlled precipitation” in diagenesis of carbonate rock reservoir |
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| Authors: | Sheng Hui Duan Zheng-Ming Liu Shan-Wei Zeng Zhe Feng Jian-Wei |
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| Institution: | 1.State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation,Southwest Petroleum University,Chengdu 610500,China;2.Southwest Petroleum University,Division of Key Laboratory of Carbonate Reservoirs,CNPC,Chengdu 610500,China;3.Institute of Subsurface Energy Systems,Clausthal University of Technology,Clausthal-Zellerfeld 38678,Germany;4.PetroChina Hangzhou Research Institute of Geology, Hangzhou 310023,China |
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| Abstract: | Based on the discovery of pore-size controlled mineral precipitation and cementation heterogeneity in carbonate rock reservoirs,the state of art and the geological implications are summarized,referring to the fluid-rock interaction and chemical hydrodynamics in porous media. (1)The pore-size controlled precipitation phenomenon is common in geological environments,as shown by the heterogeneous cementation and eventual features that the large pores are filled while small pores can be preserved. Related studies are mainly divided into three aspects,including pore structure observations at different scales,numerical simulation of fluid-rock interaction and mineral precipitation experiment. (2)The kinetic models related to surface chemistry can be used to explain the heterogeneous precipitation affected by pore-size distribution. The larger interfacial tension and mineral crystal curvature in the micropores result in the much higher effective solubility.Thus the fluids in micropores can maintain a higher supersaturation with no minerals precipitation. (3)The pore-size controlled precipitation leads to the selective preservation of micropores. It means that the much larger pores tend to be cement-filled while the smaller pores are preserved in the case of coexistence of pores at different scales. The impacts of cementation types on the overall permeability of rock are different. The pore-size controlled precipitation phenomenon is also worthy of attention in the research of geothermal development and geologic sequestration of carbon dioxide. In the last part, based on the heterogeneous cementation and porosity distribution of the Majiagou Formation in the Ordos Basin,we study the impacts of diagenetic fluids properties,origin and cementation patterns on the evolution of pore structure and high-quality reservoir distribution.The discovery and emphasis of pore-size controlled precipitation is of great theoretical significance to our understanding of the complex fluid-rock interaction process,which provides a new perspective for reservoir diagenesis and pore preservation. |
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| Keywords: | pore-size cementation heterogeneity diagenesis supersaturated fluid pore preservation |
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