Numerical Simulation Of Elastic And Electrical Properties Of Rock Based On Digital Cores

Petrophysics experiment is costly and time consuming. It encounters difficulties applying it to the rocks from the complex reservoir, such as the unconsolidated rock and carbonate sample with fracture that can not be obtained easily. Furthermore it is hard for petrophysics experiment to study the effects of micro-factors on the macro petrophysics properties. The digital petrophysics experiment is numerical simulation of petrophysics based on 3-D digital core. It will overcome the weakness of the petrophysics experiment mentioned above.The 3-D digital cores are generated by two kinds of methods. Firstly we obtain them by X-ray CT based on real rock samples and proposed a new method, which combines porosity and permeability of rock, to determine the best resolution of scanning. The other method to generate 3-D digital core is the reconstruction method based on 2-D information of rocks. We propose a hybrid method to reconstruct 3-D digital core. It inherits the advantages from process-based method and simulated annealing method. The homogeneity and pore connectivity of reconstructed digital cores are similar with those of 3-D digital core from X-ray CT. In order to study the effects of micro-factors of reservoir process-based method is applied to generate 3-D digital core with different grain radius.Based on 3-D digital cores derived from real samples, numerical methods are applied to simulate the petrophysics properties, such as mathematical morphology and the finite element method (FEM) for resistivity, FEM for elastic moduli, and lattice Boltzmann method for permeability. Those methods were also applied to the 3-D digital cores with different micro-factors to study their effects on petrophysics.For the 3-D digital cores of real samples, the numerical results are consistent with the experimental results. It validates the accuracy of numerical methods and the X-ray CT scanning. It will help us build the digital petrophysics experiment. The 3-D digital cores with different micro-factors are built to study the effects of those factors on the resistivity, elastic moduli and permeability by numerical simulation. The results indicate that those factors have great effects on macro petrophysics properties. The clay and micro pores are the main reasons to form the reservoir with low resistivity. The wettability has great effect on the fluid distribution in pore space. The saturation exponent of oil-wet rock is much larger than that of water-wet rock. For the rock with large scale in pore size there is Non-Archie phenomenon, where the saturation exponent varies with the water saturation. It is induced by the connection style of different pore network. The grain radius of rock affects its pore structure, which has effect on macro petrophysics. For a given porosity, as the grain radius increase the resistivity and elastic moduli decrease, while the permeability increases. The fracture affects the resistivity greatly. The effect depends on its volume fraction, width and direction. The elastic properties of rocks are not only determined by porosity, but also determined by the shape of pore, which is defined by aspect ratio of pore. The differential effective medium model can be applied to shaly sand with structured clay, while the combination of the self-consistent approximation and the differential effective medium model is fitted with the shaly sand with dispersed clay.