CN; mso-bidi-language: AR-SA" lang=EN-US>Mechanism of Carbonate Cementation and Secondary Dissolution Porosity Formation in Deep-Burial Sandstones near the Top Overpressured Surface in Central Part of Junggar Basin
CN; mso-bidi-language: AR-SA" lang=EN-US>The carbonate cementation and secondary dissolution porosity in the deep-burial sandstones near the top overpressured surface (present-day depths: 4 400~6 cnv w:st="on" TCSC="0" NumberType="1" Negative="False" HasSpace="True" SourceValue="200" UnitName="m">200 mcnv> and temperatures: 105~cnv w:st="on" TCSC="0" NumberType="1" Negative="False" HasSpace="True" SourceValue="145" UnitName="℃">145 ℃cnv>) in the central part of Junggar Basin are intimately related to the overpressured fluid activities. Periodic decreases of pore pressures and changes of formation hydrochemical conditions as sealing and releasing of overpressures along the top overpressured surface can result the processes of carbonate precipitation and aluminosilicate dissolving in the sandstones. Based on the data of diagenesis, carbonate cement content, sandstone property, carbon and oxygen isotope of carbonate cement, thermal maturity modeling of source rocks and so on, integrated studies indicate as fellows: The ferroan carbonate cements are the dominated cements formed in the late diagenesis stage, and the feldspar-related secondary dissolved pores are the most important pore types in the deep-burial sandstone reservoirs.