Heterogeneity of low permeability lithologic reservoir and distribution of remaining water-driven oil in Dongying Sag

The potential of low permeability reservoir in China is huge, which is controlled by the characteristics of underground reservoir and the level of development technology. Taking the low permeability lithologic reservoir of Sha-2 Member (Sand II), Block H67, Dongying Sag as an example, the reservoir heterogeneity characteristics of the low permeability lithologic reservoir were analyzed by seismic, logging, core analysis, and dynamic production data. The heterogeneity characteristics of low permeability lithologic reservoirs were analyzed, and its influence on water injection development was described. Results show that the pore radius of low permeability reservoir is small, and the heterogeneity of materials between at-plane and in-layer is strong as indicated by a large difference in permeability between stably distributed interlayer and rhythmic sand layer, and the horizontal distribution of physical property of the sand body presented obvious directivity. Affected by reservoir heterogeneity, the water injection development of low-permeability lithological reservoirs was characteristic of insufficient stratigraphic energy, low daily fluid volume per well, and uneven horizontal water injection, while the remaining oil reserves after water injection remains abundant. The remained oil is concentrated in mainly the reservoir layers and areas with large reservoir thickness and poor physical properties. The above results and understanding have important guiding significance for the development of low-permeability lithological reservoirs.