Carboniferous elastic rocks in Central Tarim Basin are characterized by clay mineraltransformation

well-developed dissolution

weak compaction and quartz secondary enlargement

lacking of carbonate cementation in early stage and local carbonate filling in late stage.Primary porosity was preserved to the maximum value of about 15%. The Carboniferoussequences drilled in Central Tarim are now in the late diagenetic stage (containing A

1

and A

2

stages). This stage is considered to be the peak period of organic acid production

and dissolution is intensive. This could considerably improve the primary porosity (increasing to 20%-23% )

thus forming high porosity and high permeability reservoirs.