Heterogeneity of reservoirs is a crucial aspect of reservoir characterization and serves as an important basis for adjustment in the later stages of oilfield development. The study examines the heterogeneity characteristics of the T member reservoir in the Napo Formation of the P oilfield from three dimensions: within layers, between layers, and in planar view. The research indicates the following: (1) In the TmTS layer reservoir, the volume fraction of quartz in the clastic components is the highest, ranging from 59 to 98% with an average of 90.5%. The sandstone reservoir does not contain feldspar, and the content of rock fragments varies greatly, from 1 to 37%. The content of interstitial materials is relatively small, primarily consisting of cementing materials, with abundant calcite, illite, chlorite, and authigenic quartz as the main cementing minerals. (2) The TUTS layer of the T member is characterized as having extremely low porosity and extremely low permeability. The TmTS layer is a low porosity, medium permeability reservoir, while the BmTS layer is an extremely low porosity, low permeability reservoir. The TmTS layer is dominated by tidal channel sedimentary microfacies, which have good reservoir properties. (3) All three layers exhibit strong geological heterogeneity, but the TUTS and BmTS layers have stronger heterogeneity than the TmTS layer. There is development of positive and composite rhythms within the layers, with large variations in permeability and significant differences in permeability coefficient. The sandstone density of the TUTS and BmTS layers is around 0.1, while the TmTS layer sandstone density is 0.7, indicating Interlayer heterogeneity is relatively weak. In terms of planar view, sedimentary microfacies control the development characteristics of the sand bodies. The TmTS layer is primarily composed of tidal channels, with tidal sandbars and tidal sand ridges as secondary features. There is good connectivity within the tidal channels, but poor lateral connectivity, resulting in strong planar heterogeneity. A thorough analysis of the heterogeneity characteristics within the T member, and comparison of the heterogeneity differences among the various sub-layers, provides reliable theoretical guidance for subsequent well placement and centralized water injection development in the oilfield.