Organic-inorganic Interactions Affect The Densification And Development Of Sandstone

Based on the core observation,conventional thin section,cathodoluminescence,scanning electron microscope?SEM?experiments,in the east of the Ordos basin of Shanxi Formation sandstone,we study on the densification of sandstone.at the same time,with the aid of basin simulation,hydrocarbon source rock thermal evolution,hydrocarbon generation,we simulate the generation of organic acids.Recovery the tectonic and sedimentary evolution of heat in the study area,using basin model software,we study in detail the micro-environment the cause of porosity in the study area Shanxi Formation sandstone reservoir,organic fluid source and mechanism of action.To study the evolution of the diagenetic stages,the amount of organic fluid formation,intensity on the micro-pore diagenetic environment,further analysis of the different stages of diagenesis of organic acids in the source rocks in different stages of the transformation of the role of the thermal evolution of the reservoir diagenetic minerals,combined with experimental data and basin simulation software to analyze the Shanxi team,under the geological conditions due to the sandstone palaeogeothermal,diagenetic fluids and a variety of environmental changes caused by diagenesis densification process development.Research has shown that the organic matter type in Shanxi Formation in eastern area of Ordos Basin is dominated by type III kerogen and coal source rock,reservoir is a typical low porosity and permeability of tight reservoir layer,sandstone type mainly lithic quartz sandstone.Into the early diagenetic stage,when Ro is less than 0.5,the main types of organic fluid is humic acid,when Ro is greater than 0.5,the type III kerogen can release than type I and type II kerogen more organic acid fluid and result in coal measure source rock pore type is acidic.Organic acids dissoluted on feldspar,debris,volcanic ash and other soluble mineral,and generated SiO₂,quartz overgrowth provides a source of silica sources.A large number of silicon sources and in the acidic stability environment is the main cause of increased self quartz.In the early diagenetic stage?at 220Ma?and the late diagenetic stage A?at 160Ma?for the two main periods of organic acids generated.Organic acids resulting in feldspar,debris and other inorganic mineral dissolution,quartz secondary hyperplasia,authigenic clay minerals occupy the pore space,and as a result of the Shanxi Formation sandstone are influenced strongly by mechanical compaction and cementation,the porosity densification.At the end of the early diagenetic stage,quartz sandstone due to the early compaction and siliceous cementation function is more intense,resulting in the original reservoir porosity decreased to15.47%.Late diagenetic stage A,compaction and siliceous cementation cause reservoir porosity is further reduced to 10.94%,late diagenetic stage B,compaction and siliceous cementation cause reservoir porosity is further reduced to 8.23%,late diagenetic stage C,porosity is further reduced to 5.84%,the densification of the reservoir.In general,it is considered that the formation of organic inorganic interaction is the result of the decrease of reservoir porosity and the development of reservoir density.