Impacts of mantle-genetic CO2 influx on the reservoir quality of Lower Cretaceous sandstone from Wuerxun depression, Hailaer basin
海拉尔盆地乌尔逊凹陷幔源CO2充注对下白垩统砂岩储层质量的影响

The history of mantle-genetic CO2-sandstone interactions are partly recorded in the dawsonite-bearing sandstone from Wuerxun depression, Hailaer basin. The petrology and reservoir characteristics of dawsonite-bearing sandstone from Wuerxun depression, Hailaer basin have been investigated using polarizering microscope, scanning electron microscope and core analysis data of porosity and permeability to unravel effect of mantle-genetic CO2 influx on the reservoir quality. The mantle-genetic CO2 influx leads to the partly dissolution of feldspar and the precipitation of dawsonite as well as ankerite. The secondary porosity has been formed as a result of the feldspar dissolution. Dawsonite that filled pores and replaced feldspar and other framework grain is distinguished by its acicular habit, typically forming bundles, tufts, fans and rosetes. Locally, dawsonite also forms tabular crystals. Dawsonite is locally replaced by ankerite suggesting that dawsonite grew before ankerite. Dawsonite generally comprises 1%~20% of the sandstone volume.