Construction of an efficient development mode for buried-hill fractured reservoirs in Bohai Bay

Fractured reservoirs are very complicated due to the coexistence of matrix and fractures. In addition, there are plenty of micro-fractures and a few dissolution pores rather than the traditional pores in the matrix of buried-hill fractured reservoirs. Thus, the performance of water flooding is mainly decided by the storage, percolation, and oil displacement characteristics of both fracture and matrix. However, the distribution and transmissibility of both macro-fractures and micro-fractures are actually heterogeneous due to the special origins. Moreover, the mass transfer between matrix and fracture is complicated. Therefore, it is very difficult to construct an effective development mode to obtain a favorable development effect. With the objective of effectively developing such reservoirs, JZ25-1S in Bohai Bay in China was taken as an example in this paper. First, experiments were conducted to study the stress sensitivity of both matrix and fractures in buried-hill fractured reservoir, and simulations were performed to optimize the initial development project of depletion. Then, 3D large-scale experiments and simulations were demonstrated to study the oil displacement mechanisms and contributions of matrix and fracture for choosing optimal water flooding mode. Subsequently, the impacts of well pattern, injection-production ratio, and water flooding modes on development effects were studied by experiments and production practices in water flooding stage. Ultimately, an effective development mode was presented and used in the JZ25-1S reservoir.