Abstract:

This paper analyzed the characteristics of volcanic reservoir space and its formation process in the case of intermediate-basic volcanic rock in the Carboniferous Jinlong Block,by integrating the core,thin section,logging,seismic and analytical data.The results show that:(1)feldspar and other minerals in the upper volcanic cycle altered to zeolite and chlorite and formed an unstable layer during the volcano eruption quiescent intervals;(2)tectonic movement at the Late Carboniferous developed fault-fracture and unconformity,and then meteoric freshwater could cause vertical and transverse dissolution along the fault-fracture and the unstable layer at the top of the cycle;(3)new fault-fracture formed through the tectonic activity of the La te Jurassic period,and the pore-fracture reservoir was compartmentalized and the accumulation space was basically finalized.Under the control of fault-fracture,palaeo-geomorphology and contact surfaces of the volcanic cycles,the reservoirs are characterized by zonation in the vertical direction and by lenticular geometry with greater thickness in the paleo high and losser thickness down the paleo-slope.As a whole,the reservoir is a complex"multi-zone overlapping"reservoir,composed of fractures,dissolved pores,and dissolved fractures.The geological model of pore-fracture volcanic reservoir is of great value for volcanic reservoir prediction and oil/gas exploration.

Key words: fracture, dissolved pore, volcanic cycle, intermediate-basic volcanic rock, Carboniferous, Junggar Basin