Key Evaluation Index Of Water Injection Development Effect In Low Permeability Fractured Reservoirs In Wangyao District

Low-permeability fractured reservoirs are featured with poor physical property, micro-fracture and the difficulty in establishing an effective injection-production system. How to correctly understand the influencing rule of micro-fracture on reservoir water flooding and the key controlling factors impacting low-permeability fractured water flooding is the basis for improving the water flooding of low-permeability fractured reservoir, scientifically evaluating the effect of low-permeability fractured reservoir water flooding and achieving efficient oilfield development, which has great significance and role. Based on the analysis of the key controlling factors of water flooding effect and percolation theory of low-permeability fractured reservoir, this paper conducts a systematic study on 13 key indicators of the development effect of low-permeability fractured reservoir, and the results are as follows:(1) From the perspective of the equivalent permeability, this paper establishes the equivalent continuum model of low-permeability fractured reservoir, calculates the equivalent permeability respectively parallel and perpendicular to the fracture direction as well as the vertical equivalent permeability of the reservoir, and quantitatively studies the influence rule of different parameters of natural fracture on reservoir permeability, which lays the foundation for carrying out the low permeability fractured reservoir percolation theory with equivalent continuum model.(2) By combining the equivalent continuum model and reservoir engineering approach, the equivalent percolation model of low-permeability fractured reservoir is established, and the influence rule of characteristic parameters of natural fracture on oil well productivity and percolated space is studied. Meanwhile, the effects of natural and artificial fractures on oil well productivity are studied by numerical simulation method. The movement rule of unstable percolation boundary in single well and the inter-well stable percolation law are studied based on the equivalent continuum model, which lay the foundation for systematically carrying out the research on the key development effect of low-permeability fractured reservoir.(3) Based on the percolation law and main controlling factors of development results of the low permeability fractured reservoir, the evaluation index system for the water flooding development effect of low-permeability fractured reservoir is built and the calculation method, index theory change law and evaluation criteria are of 13 key indicators including recovery efficiency, yield and reserve-production status, well pattern improvement, water-bearing and water drive conditions are studied, which provides the basis for the correct evaluation of the development effect and level of low-permeability fractured reservoir.(4) The comprehensive evaluation method to evaluate the water flooding effect of low-permeability fractured reservoir is built based on the fuzzy comprehensive evaluation theory. The water flooding effect of Changqing Ansai Oilfield Wangyao maturing field is evaluated and the feasibility of evaluation index system and evaluation criterion is discussed. Besides, the adjustment measure suggestion to further improve the development effect of Wangyao maturing field is proposed based on the evaluation results.