Diagenesis of the Changxing Formation Carbonate Rocks in the Northeastern Sichuan Basin and Reservoir Porosity Evolution

The object of this work is the Changxing Formation carbonate rocks in the northeastern Sichuan basin.Our purpose is to study their diagenesis,diagenetic sequence,porosity evolution characteristics by use of analytical techniques of thin sections,casting,cathodoluminescence and X-ray diffraction.The widespread diagenesis in this area principally includes compaction,cementation,filling,replacement,dolomitization,recrystallization,dissolution and fracture diagenesis.Of all the diagenesis,cementation,dissolution,filling,dolomitization and recrystallization contribute greatly to the porosity development of reservoirs.In the reef-beach reservoir of the Changxing Formation,micrite limestones,micrite grain limestones,sparry grain limestone,reef limestone and reef dolostones developed well.Because of the composition differences,the pore evolution owes different characteristics.According to the diagenetic order,mutual cutting relation between minerals and the porosity evolution characteristics in the diagenesis process,this paper sums up the diagenetic sequence and porosity evolution rule in the Changxing Formation.