Signature Of Volcanic Reservoirs Of Xujiaweizi Fault Depression, North Songliao Basin, NE China

With the development of petroleum industry and improvement of explorationtechnology, certain progresses have been made in the research on volcanicreservoirs both at home and abroad. Volcanic oil gas reservoirs with certain scaleand output have been discovered successively, which expanded oil gas exploration.With its wide-range distribution, small scale, high initial output and rapid decrease,together with its complexity in reservoir type and reservoir-formation conditions,there is no systematical research methodology, which affected its exploration anddevelopment. This paper started from the study on volcanic rock reservoir, summarized itscharacteristics and regularity. Based on the study on volcanic rock reservoir and thegeochemical materials about natural gas, the paper, with the combination of thestore layer and fluid, mainly dealt with the synthetic description towards thecharacteristics of natural gas reservoir in the chosen study area--- Xujia Weizi faultdepression. As for the Xujiaweizi fault depression deep volcanic rock natural gas reservoir,neutral andesite to acid rhyolite are observed from the viewpoint of its lithology,and lava store layer as well as volcaniclastic rock store layer from structure.Shenshen 101 well and Shengshen 2 well in Wangjiatun presented neutral andesiteand andesite-basalt. Wang 903,4 well presented acid lava; Acid lava dominatedChangDe area. Macro pores and cracks are well developed in volcanic rockreservoir, which presented itself the storage characteristic of dual porosity medium The porosity and permeation of the volcanic rock reservoir varied greatly,porosity: 4-11%, horizontal permeation 0.1-122 × 10-3 μ ｍ , while the -2perpendicular permeation 0.01-44.4×10-3μｍ-2.Most of the storage layers are lowpore permeable. Generally, fractures are well developed in volcanics storage layers,which make the pore permeable conditions of the production layer are better thanthe testing results. Arise energy can arriving in industry standard。The materialconditions of the volcanics storage layer mainly associated with the volcaniclithofacies and the post-reforming. The top as well as the bottom of the overflowlava, together with outburst volcanic breccias presents superior material conditions,with less relation to its embedded depth. Therefore, it indicates that better volcanicsstorage layer can be founded in deep depth. Volcanics natural gas reservoir can be catalogued into volcanics hydrovcarbongas reservoir, and volcanics CO2 gas reservoir, which has hydrocarbon gas such asCH4 and non- hydrocarbon gas such as CO2 as representation respectively. It can beobserved easily through the geochemical data analysis of natural gas that the heavyhydrocarbon gas content in CHANGDE area is lower than of other areas, togetherwith high aridity coefficient. The gas presents to be rather acid. On the contrary, theheavy hydrocarbon gas content in WANGSHENG area is relatively high, withlower aridity coefficient than CHANGDE area. In hydrocarbon gas reservoir,volcanics reservoir is different with the volcaniclastic rock in natural gascomposition characteristic. The mean content of CH4 in volcanics reservoirs is lower than that ofvolcaniclastic reservoir, while the mean content of the N2 and CO2 is in the contrary.The natural gas reservoir data of Wang 903 well and deep in 4well serve as explicitexamples. In combination with the carbon isotope data, it arrives that thecomposition of the volcanics gas reservoir mainly involves the coal-type, withmixture of oil-type and inorganic gas. As for the volcanics CO2 gas reservoir, theCO2 content of as Fangshen 9 well reaches the maximum level of 93.08%. CO2carbon isotope is -4.06‰～-5.46‰., which present well according with theinorganic original CO2 carbon isotope, which gives -8‰～-4‰. Therefore, theinorganic original CO2 gas reservoir is determined. The profiles of volconics natural gas reservoir is completed, the stru...