Application of a fault identification and fault sealing evaluation method in production and development stage in ZB area of Bohai Bay Basin

When the oilfield is in the middle and late stage of intensive waterflood development, waterflood development is likely to cause fault activation and bring about the development risk of injection-production contradiction in well groups and low injection-production correspondence rate. Therefore, it is necessary to identify and evaluate the fault sealing of low-grade faults. At present, the fault sealing is mostly high-grade faults in the exploration stage and mostly stays in the semi-quantitative evaluation method. Therefore, this paper provides a set of integrated thinking of fault interpretation and fault sealing quantitative evaluation in production and development stage. Firstly, the fault is delineated by well-seismic integrated method, and the possible fault breakpoint is identified from changes of strata thickness in the well. Secondly, high-frequency seismic data are obtained by frequency division, and faults are identified on the basis of fault breakpoint data by two-dimensional seismic section. Then, various three-dimensional seismic attributes such as ant tracking and variance (edge method) are extracted, and the combination of plane and section interpretation is used to strengthen fault characterization and recognition in three-dimensional space. The basic characteristics of faults are described well by the above methods. Then, the fault sealing property is qualitatively evaluated from the aspects of fault nature, fault inclination, fault distance and burial depth, and the conventional fault sealing property is quantitatively analyzed from shale gouge ratio method, lithologic juxtaposition method and the normal pressure on the fault plane from lateral and vertical aspects. Finally, the fuzzy comprehensive discrimination method is used to comprehensively evaluate the fault sealing property based on the above three parameters of the analysis results. The method is applied to ZB area with complex structure and developed fault, and the threshold of fault opening or sealing is determined by the comprehensive evaluation index of fault sealing in ZB area of Bohai Bay Basin. The results of low-grade fault sealing identified in the early stage are judged and applied to the development and production practice. The dynamic and static data such as tracer response relationship, injection-production response relationship and oil properties on both sides of the fault are used to verify the method. The results show that the method is in good agreement with the dynamic and static data .It is suitable for the fault sealing evaluation of  ZB area，and can better guide the later waterflood development, which is of great significance for the recovery of remaining oil .