By using the physical properties and core observation

this paper compares their reservoir qualities and characteristics of reservoir spaces in the study area. The main factors controlling the development of highquality reservoirs are also discussed based on study of the lateral and vertical distribution of reservoirs and the occurrence of oil

gas and water. The reefshoal complex reservoirs of the Upper Ordovician are significantly controlled by sedimentary facies belts and faults

thus show obvious characteristics of occurring at certain horizons and segmentation. In contrast

the karstweathering crust reservoirs of the Lower Ordovician are mainly controlled by faults and karstification along unconformities. They mainly occur within 40-200m under the unconformity

and show obvious layering features. A comprehensive comparison of these two kinds of quality reservoirs indicates that both of them feature in “lateral connection and vertical superimposition” and are similar in reservoir quality

though their major controlling factors are different. Moreover

the quality carbonate reservoirs are developed under the dual control of sedimentation and modification. The western platform as well as the subsidiary karst upland and upslope in the inner fault zoneⅠ in Tazhong area have favorable conditions for the development of highquality carbonate reservoirs

thus are play fairways.