Occurrence of deep fluids in Tazhong area has been confirmed through analyzing rare-earth elements in rock and oil samples

carbon isotope of carbon dioxide and fluid inclusion thermometry in reservoir rocks.The deep fluids below the basement entered the basin along the discordogenic faults and through volcanic activity

and the carbonate reservoirs were modified by dissolution and metasomatosis through material and energy exchanges.The porosity and permeability of the carbonate reservoirs were thus improved

leading to the formation of deeply buried and modified type good carbonate reservoirs.The fluorspar ore belts

discovered along the large fault and in volcanic activity area in the western part of Tazhong

are the result of activities of deep fluids

and they are the main reservoir types in Tazhong 45 oilfield.The origin and sphere of activity of deep fluids are closely related to discordogenic faults and volcanic activities.Areas with well-developed discordogenic faults and volcanic rocks can be considered as indicators for seeking deep fluid modified reservoirs.