| In view of the unclear understanding of the development characteristics and laws of interlayers in Chang 2 reservoir in Qiaozhen area of Xiasiwan oilfield,the distribution pattern and connectivity of single sand body are not clear,and the heterogeneity of reservoir sand body is strong.Controlled by heterogeneity,the single well production of reservoir varies greatly and the production decreases rapidly.On the basis of previous studies,combined with core observation,drilling coring,logging and analysis and testing data,this paper uses logging interpretation model establishment,fine identification of interlayers,fine characterization of sand bodies and quantitative calculation of heterogeneity parameters.The types and development characteristics of interlayers,single sand body characterization and sand body connectivity,intra-layer and inter-layer heterogeneity,and the relationship between heterogeneity and oiliness of Chang 2 oil layer in the study area were systematically studied.The results show that:(1)The Chang 2 reservoir in the study area develops argillaceous interlayer,calcareous interlayer and physical interlayer.The development of muddy interlayer is controlled by sedimentary microfacies.The development of calcareous interlayer is controlled by supersaturated precipitation of carbonate ions in the early and late diagenesis.The development of physical interlayers is controlled by both hydrodynamic conditions during the sedimentary period and late diagenesis.(2)Sand bodies in the study area can be finely identified as interlayer separated sand bodies,isolated sand bodies and superimposed sand bodies.After fine identification of sand bodies,the average thickness of single sand layer decreased from 4.16 m to 3.73 m,the maximum number of single well sandstone layers increased from 22 to 29,and the average number of single well sandstone layers increased from 4.97 to 6.02.The proportion of type I sand body decreased from 7.62% to 5.41%,the proportion of type II sand body increased from37.92% to 41.83%,the proportion of type III sand body decreased from 40.11% to 39.17%,and the proportion of type IV sand body decreased from 14.35% to 13.59%.(3)Vertically,there is no connectivity between argillaceous interlayer separated sand body,calcareous interlayer separated sand body,physical interlayer separated sand body and isolated sand body.The vertical superposition and vertical cut sand body have good connectivity.In the transverse direction,the stable continuous sand body in the single sand body is connected,the lateral pinch-out sand body at the edge of the single sand body is connected,the lateral cut-over sand body of the single sand body is connected,and the unequal and phase change sand body is not connected.(4)The interlayers between the sand bodies of Chang 2 reservoir in the study area are relatively developed,and most of them are thin layers,resulting in poor vertical development and connectivity of sand bodies,and strong interlayer heterogeneity.The calculation results of permeability heterogeneity parameters of most sand bodies in the study area have reached the standard of strong heterogeneity,and the intra-layer heterogeneity is strong.On the whole,the Chang 2 reservoir in the study area shows strong heterogeneity.(5)The heterogeneity of Chang 2 reservoir in the study area is negatively correlated with oil-bearing property,that is,the stronger the heterogeneity of the reservoir is,the lower the degree of crude oil enrichment is,and the production is relatively poor.The weaker the reservoir heterogeneity is,the higher the degree of crude oil enrichment is,and the better the production is.On this basis,the high quality production section prediction of single well section and oil layer well section is carried out. |
