Fractured - Vuggy Genesis Model of Middle - Lower Ordovician Carbonate Rocks in Tahe Oilfield of Trim Basin, Western China

The fracturedvuggy characteristics of carbonate rocks of Middle Lower Ordovician limestone in Tahe Oilfield was studied in the article. By analysis of the affecting factors of reservoir space include sedimentary diagenesis, tectonism and karstification, we found deposition determined the Formation and the number of primary porosity, diagenesis affected the pore destruction and construction, tectonism controled the reservoir burial history and the Formation of structure cracks and weathering fissure, karstification affected the latter change of the previous diagenetic porosity and remodeled the large hole-cave reservoir in Tahe Oilfield. Then the fissure-cave porosity evolution is studied. And we found that the Lower or dovician carbonate rocks in Tahe area experienced shallow marine diagenetic environment, shallow surface meteoric diagenetic environment, early shallow burial diagenetic environment, uplift exposed supergene meteoric diagenetic environment, shallow deep burial diagenetic environment. As a result, the Tahe Oilfield Ordovician fissure-cave porosity evolution model is established.