Internal Structure Of Fault Zone、Sealing Ability And Fluid Migration In Volcanic Rock

Faults in the volcano rock have an important significance for the unconventional oil andgas reservoir. Based on a lot of literature research and field observation, this paper mainlystudies the fault deformation mechanism and fault zone internal structure of low-non-porosityrocks, then analyzed that faults in the low-non-porosity rocks have a role on the control of oiland gas accumulation. Research shows that fault deformation mechanism of low-non porosityrocks are fracturing, cataclasis and cataclastic flow effect, respectively forms the beginning ofbreccia, breccia, cataclasite, and ultra-cataclasite. the former three types of fault rockspermeability is relatively high, and is the channel of fluid migration. Fault zone internalstructure of low-non-porosity rock is “tow yuan” structure, namely fault core and damagezone. Different types of rocks, the development process corresponding to the lithologic faultare also different. The volcano rock in the fault deformation process forms fault core firstly,then with the degree of deformation increases gradually, develops the damage zone whichcontains a lot of fracture, finally forms "two yuan" structure of the fault zone. Rules of faultsealing depend on the permeability of fault core. If the fault rock of fault core has highpermeability, the fault itself does not have closed, mainly lithologic juxtaposition sealing; Ifthe fault core develops fault gouge which is the low permeability fault rock, then fractureitself has good sealing ability.By the way of researching the fault deformation nechanism、the internal structure of faultzone and sealing ability in volcano rock, then analysis the control effect of Xujiaweizi faultdepression of the volcano rock in Songliao Basin. Xujiaweizi fault depression which locateson the north of Songliao Basin develops three sets of volcano rock: the Huoshiling group、theYingyi group and the Yingsan group, and finds a large scale natural gas pool in the Yingyigroup and the Yingsan group of volcanic rocks. Xujiaweizi fault system has an important rolewhich controls on the natural gas accumulation, early active fault forms the fault breccia, andthe natural gas vertical migration along the fault, then gathers in Yingcheng group of volcanicrock, but the lateral sealing ability of fault breccia is poor, by the influence of lateralpermeability relatively low conglomerate accumulation. Under the Xuzhong strike slip fault,gas reservoir shows just like the curbe “sine” on horizontal distribution.