The Study on the Terminal Fans and Reservoir Quality during Neozoic Era in Kuche down Warping Region in Tarim Basin

Key words: 
• Kuche down warping region /
• terminal fans /
• reservoir quality

Abstract: The Neozoic Era stratra deposits are mainly terrigenous clastics which formed in arid or semiarid regions in Kuche down warping region in Tarim basin. There are six lithologic associations during Neogene period in Kuche depression. The lithologic asociation during Paleogene period is FA6+FA5+FA1+FA3+FA2. The main lithologic association during Jidike period in the north area is FAl+FA2+FA5,and in the south area is FA5+FA6. The main lithologic association during Kongchong period in the north area is FA1+FA2+FA3,and in the south area is FA5+FA4. The main lithologic association during Kuche period in the north area is FA1+FA2+FA3,and in the east and south area is FA5. The sedimentary system is regarded as terminal fans by petrology,sedimentary structure and the depositional sequence. The model includes a tripartite zonation of terminal fans into feeder, distributary and basinal zones. The feeder zone is characterized by a down- stream decrease in both the scale and frequency of channel deposits,which are mainly replaced by sheetflood deposits. The basinal zone is made up of floodbasin,playa mudflat or aeolian-origined deposits. The lithologic type is mainly terrigenous clastics. The content of quartz is 10.1%-58.5%,of the terminal fan lithic fragment is 58%-84.3%,interstitial materials is 19. 2%-39.4%,cement is 1%-18%,that include anhydrite,calcite, dolomite and analcidite. The primary pore typs are primary intergranular pore,matrix micropore,shrinkage pore,intercrystal pore and inner granular pore. The secondary pore type include intergranular solution pore,granular solution pore,fracture etc. Integrated with the diagenesis,reservoir space,porosity and permeability,the reservoir quality of lower Tertiary stratra is poor and the better reservoir during Neogene period developped in the northern area in Kuche down warping region.