Characteristics of pore evolution in tight sandstone reservoirs of Yingcheng Formation-Shahezi Formation,Longfengshan Sub-sag in Changling fault depression,Songliao Basin
In response to clear understanding of reservoir rock-forming and pore evolution characteristics,this study takes the tight sandstone reservoir of the Lower Cretaceous Yingcheng Formation and Shahezi Formation in the Longfengshan Sub-sag of the Changling Fault depression in the Songliao Basin as the research object,and the pore evolution process of the main rock-forming phases is quantitatively recovered on the basis of reservoir characteristics and rock-forming phase delineation.The conclusions are as follows.The main rock type of the target formation is rock chip sandstone with low structural maturity and poor sorting and rounding;the typical type of reservoir diagenesis is compaction and cementation,the diagenetic stage is intermediate diagenetic stage B,and the diagenetic coeval sequence is:early compaction-chlorite cementation-turbidite cementation-early calcareous cementation-phase I dissolution-siliceous cementation-phase Ⅱ dissolution-late calcareous cementation;the typical diagenetic phases include chlorite cementation diagenetic phase,turbidite cementation diagenetic phase and acidic dissolution diagenetic phase,and each diagenetic phase has undergone the process of compaction and cementation to reduce pore size,and two stages of dissolution to increase pore size;the pore evolution characteristics and the understanding of tight gas reservoir formation period are integrated,and two reservoir evolution models are established,namely the first tight and then reservoir formation model and the tight unresolved reservoir model.
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