Diagenesis and High Quality Reservoir Forecast of the Qingshankou Sandstones in the Southern Songliao Basin of Northeast China

Abstract

The Qingshankou (QSK) sandstones are mostly lithic arkoses and feldspathic litharenites. A combination of primary and secondary pores constitutes the pore features of the QSK sandstones that have experienced complex diagenetic events. Diagenetic minerals include illite, mixed illite/smectite (I/S), chlorite, calcite, dolomite, Fe-calcite, dawsonite, quartz, halloysite, paligorskite, and so on. The carbonate and clay cement blocks the pore spaces and throats, especially poikilitic calcite degrades reservoir quality, whereas the rigid quartz preserves pores by resisting compaction. The compaction porosity loss is 18.4% and the cementation porosity loss is 9.63%, which indicates compaction is the chief factor that reducing reservoir quality. The porosity that was generated from dissolution can measure up to 3–8%. Four diagenetic-lithofacies, namely, plastic detritus dissolution diagenetic-lithofacies, quartz overgrowth diagenetic-lithofacies, carbonate cementation diagenetic-lithofacies, and compact-infill diagenetic-lithofacies, are observed in the QSK sandstone. The sandstones that display plastic component dissolution diagenetic-lithofacies or the quartz overgrowth diagenetic-lithofacies prove to be good hydrocarbon reservoirs.