Reservoir characteristics and diagenetic evolution of Carboniferous volcanic rock in Kelameili gas field of Junggar Basin

Key words:  Junggar Basin  Kelameili gas field  Carboniferous  volcanic  reservoir characteristics  diagenetic evolution

Abstract:

The reservoir characteristics of the Carboniferous volcanic in Kelameili gas field of Junggar Basin were studied using core observations, microscopic identification and scanning electron microscope analysis. Combining with burial history, thermal history and hydrocarbon infilling history, the diagenetic evolution and the pore dynamic evolution of the volcanic reservoir were derived. The results show that there are many types of volcanic reservoir spaces, but the secondary dissolved pores and structural fractures are the most abundant types. The reservoir is in general medium porosity and low in permeability. The reservoir property of pyroclastic rock, volcanic lava and subvolcanic rock is better than that of volcanic sedimentary-pyroclastic rocks. The volcanic pore structure can be divided into three categories. Its spatial distribution is controlled by structure, unconformity and lithology. There are mainly seven types of diagenesis. The diagenetic evolution of the volcanic reservoir can be divided into three stages, syngenetic diagenesis stage, exodiagenesis diagenesis stage and burial diagenesis stage, respectively. The reservoir capacity is closely related to weathering and leaching in the exodiagenesis diagenesis stage. The dissolution in burial diagenesis stage may have further enlarged the volcanic reservoir space.