Study On Characterization Of Pore-Fracture Fractal Reservoir And Law Migration Of Fluid

Oil and gas reservoir in the presence of large amounts of pore and fracture,and the decision of reservoir pore and fracture structure and transport properties of reservoir property,at the same time caused by the diversity of causes these pore and fracture distribution may show that the scale invariant features.It is very important to explore the complex space geometry of pore and fracture structure for the occurrence and migration of oil and gas,and it is the premise of quantitative evaluation of reservoir productivity.The scale invariance of pores and fractures in reservoir is mostly described by the classical quantitative-dimension relationship and its derived model.However,the classical quantity-size relationship and its derived models mostly focus on the quantification of the complexity of fractal behavior,seldom on the definition of fractal behavior.Recent fractal topology theories show that the relationship between fractal dimension and fractal behavior is one to many,and fractal behavior can determine the only fractal dimension.The above studies show that a fractal dimension D alone cannot determine the distribution of unique pores and fractures.Based on the above understanding,this paper,relying on the fractal topology theory,quantitatively described the fractal characteristics of pores and fractures in the reservoir by using the advantage of unstructured subdivision of Voronoi algorithm,and simulated them at the pore scale by using lattice boltzmann method(LBM),including:(1)In this paper,the complex types of fractal characteristics of the coupling of pore and pore throat in the pore structure are demarcated,including the original complexity and behavior complexity.A quantitative description of the original complexity of pore-throat coupling type is realized by using the Voronoi algorithm.Based on the fractal topology theory,the scale invariant definition of the behavior complexity is given,and a new granular network model is developed to represent the pore structure.Based on the new model,the effects of original complexity and behavior complexity on pore structure are analyzed,and the validity of the model is verified by the deduced formulas of porosity and specific surface area.Then,LBM method is used to simulate the fluid transport behavior in pore structure with different original complexity at pore scale,and the influence of pore structure parameters on transport properties is studied.The new model can well separate and characterize the original complexity and behavior complexity of pore throat coupling structure.The research results provide a theoretical basis for understanding the complex types of natural reservoirs and their fabric models,provide a reference for the definition of original complexity and behavior complexity,and provide a framework for quantitative characterization of arbitrary complex pore structure.In addition,the model simulated by LBM is more convincing because it separates the original complexity and behavior complexity.(2)According to the characteristics of fractures in the reservoir and the advantage of space division of Voronoi algorithm,a fractal network model more consistent with the real fractures is constructed.Respectively to build single fractal fracture of single phase,multiphase and self-similar and self-affine model,on this basis,the simulated the influence of different fractal behavior of fissure structure,and according to the fractal topology theory developed a method of multifractal fracture network model of the building,improved the fractal characterization method of fracture network in reservoir.The method greatly reduces the difficulty of model construction and provides an idea for accurately describing the fractal distribution of fractures in reservoirs.(3)Based on the constructed fractured fractal network model,the percolation properties in the fractured network were simulated at the pore scale using LBM.From the perspective of fractal topology,the relationship between porosity and permeability is analyzed.Then,combined with the kozeny-carman(KC)equation,the effects of behavioral complexity on physical parameters such as porosity,hydrologic curvature,specific surface area and shape factor were analyzed.The results show that in the fractured fractal network,the porosity and permeability under the control of fractal behavior show a positive correlation,and there is a rule between fractal topological parameters and physical parameters of porous media.