Junggar Basin Shixi Oilfield Carboniferous Volcanic Facies And Reservoir Characteristics

The study of volcanic reservoir is one of the new research fields home and broad as a complicated and special oil and gas reservoir. Many problems need to be further stydied. According to the process of volcanic action and based on lithology, petrophysical property, log analysis and capillary pressure, lithology and its facies are classified and reservoir property is comprehensively analysized in Shixi field.Through determination of flowing direction of lava flow by focusing method and volcanic rock formation thickness study by means of statistics, lithology and lithologic facies are correlated. It is believed that explosion facies and overflow facies are principal in Shixi field and volcanic rock body in Carboniferous is composed of nonhomogeneous mass geologic bodies that have many volcanic extrusions and magma property is different and overlapping.The lithology of such accumulating rock includes neutral andesite, andesitic volcanic breccia and acidic dacite, dacitic breccia. The accumulating space is mainly solution erosion pore connected with fractures, with moderate porosity, higher capacity and thinner throat pore channels. It belongs to low permeable intense nonhomogeneous dualstructure (namely fracture-pore combined) accumulating body. The fracture and fissures of Shixi's Carboniferous reservoir include shrinkage fissures, structural fractures, weathering and solution erosion fissures, mainly appeared as high-dip structural fractures with moderate width of fracture opening.Reservoir pore structure has fourtypes:isolated-intergranularpore, bad-developing-pore micro-fracture, well-developingandgood-connectivity pore and medium-developing fracture-cave. What's more, reservoir in Carboniferous, Shixi, is divided into four types: fracture and cave type, large pore type, moderate pore and large cave type and fracture type.