Research Of Permeability Models Of Reservoirs Based On Digital Cores

Digital core technology, as an emerging numerical simulation method, it has graduallyplayed an important role in the research of the petrophysical properties. Using this numericalsimulation method to study effects of microscopic factors on percolation properties ofreservoir rock, it can make up for the lack of traditional petrophysical experiments. Besides, itprovides the bridge between the study of reservoir rock permeability and its internal structure,and it is suitable for modeling studies on reservoir permeability model.This paper uses X-ray CT scanning method and process-based simulation method toconstruct the3D reservoir digital core of porous medium, and then uses random simulationmethod based on fractal theory to establish fractal discrete fracture network, and combinesreservoir digital core of porous medium to get the3D fracture network digital core offractured medium, which lay the foundation for carrying out digital rock physics experimentsof reservoir rocks.On the basis of digital core, we improve the maximum ball method developed by Dong,and use this method to establish the pore network model which has same topological structureand geometric characteristics with digital core, and then verifies the modeling method of porenetwork model from static properties and dynamic properties. Static properties mainlyconsider the topological structure and geometric characteristics, like porosity, effectiveporosity, heterogeneity and pore structure. The results agree well with the calculated results ofdigital cores. Dynamic properties considered the seepage properties including absolute andrelative permeability, and agreed well with the experimental results and calculated results ofdigital cores.The pore scale flow simulation is carried out with the pore-scale flow simulation theoryand method on the platform of pore network. The effect of three main factors on the absolute and relative permeability is researched in the aspects of pore structure, rock matrix propertiesand fracture properties respectively. In the aspect of pore structure, the factors such as poreradius, throat radius, radius of pore and throat, shape factor and coordination number aremainly considered. The results indicate that the major influence on the absolute permeabilityare radius of pore and throat, shape factor and coordination number, and radius of pore andthroat, coordination number satisfy power function and shape factor satisfy inverseproportional function to the absolute permeability. The major influence on the relativepermeability are shape factors of pore and throat, aspect ratios and coordination number. Theoil coefficient satisfies exponential function with aspect ratios of pore and throat and linearfunction with coordination number, quadratic function with shape factors of pore and throat,respectively. However, the water coefficient meets a linear dependence to aspect ratio andquadratic function with coordination number and also linear and quadratic dependence withshape factors of pore and throat, respectively. In the aspect of rock matrix properties, theeffects of particle radius, sorting coefficient, compact factor, diagenesis facotor andwettability are considered. The results show that particle radius have power relationship withabsolute permeability and sorting coefficient, compact factor, diagenesis facotor haveexponential relationship with absolute permeability, and also wettability is the main factor torelative permeability, oil relative permeability decreaseing and water relative permeabilityincreasing with the wetting angle increasing. In the aspect of fracture properties, the effectsof dip, strike, fracture length, aperture, fractal dimension of fracture center and fractaldimension of the length distribution on the absolute and relative permeability are researchedrespectively. The results show that the major factors are aperture, fracture length, fractaldimension of fracture center and length distribution. The absolute permeability meets a lineardependence on the fracture length and pow function with fracture aperture and exponentialfunction with fractal dimension of fracture center and length distribution. The oil and watercoefficients meets a linear dependence on fracture length, aperture, fractal dimension offracture center and length distribution.The absolute and relative permeability model which are suitable for both porous medium and fractured medium are constructed based on the research of effects of several factors onthe absolute and relative permeability. After processing the experimental and numericalsimulation data using the new model, the degree of fitting is considerably well.