Research On Digital Core Refactoring Techniques Based On Simulated Anneal Arithmetic And Numerical Simulation Of Its Electrical Conductivity

At present, the rock physical experiment can measure the physical properties in porous media, however, with the successive improvement of scientific research level,for some special reservoir samples, it is difficult to get the experimental results by using the traditional rock physics experiment methods. Furthermore, it is also known for many defects, such as long experimental period, high cost, poor stability of experimental results, etc. As a kind of emerging rock physics research method,numeral stimulation technology, which enjoys many advantages including lower cost,higher efficiency, more convenient application, is attracting more and more attentions.Meanwhile, the numerical simulation is being developed to be more accurate,practical and versatile with the efforts of experts and scholars at home and abroad.This paper is taking original two dimensional(2D) core sections as basis, using artificial threshold segmentation to divide 2D core sections into pore and skeleton,and then conducting binaryzation segmentation processing. The establishment of digital core model is based on the geometric features of the pore space of original core.Accordingly, the author studied the micro pore space characteristics of original core,analyzed the spatial probability distribution of parameters including core pore radius,pore-throat radius, pore shape factor, pore-throat ratio and other ect., and quantitatively described the pore morphology of original core space. Finally, the 3D digital core model is built by using the simulated anneal arithmetic(SAA) method with the constraint of actual core pore space distribution characteristics. In order to overcome the disadvantages of low efficiency and much isolated points in building digital core model by the traditional simulated annealing methods, this article defines the criterion to select the boundary point of pore and the matrix, and proposes the generation solutions of the new system by exchanging the isolated pore points and boundary points of pore and matrix based on the majority operator method, Improved traditional modeling method of simulated annealing. Compared with traditional SAA modeling, the results of improved model are relatively closed to original cores.In this paper, the electrical conductivity of the digital core model is studied by using the finite element method, which further helped achieve the analysis of conductivity differences among three principal axes The numerical simulation results show that the built digital core model has significant conductivity difference in each axis direction. The conductivity difference between the Z axis and the other axis directions is particularly prominent, while the X axis and the Y axis are smaller, This may be related to the given way of the constraint function. But on the whole,resistivity calculation results show that the digital core conductivity obeys exponential law with the change of porosity, and the lithology coefficient and cementation exponent obtained from formulae accord with the theoretical results, which verified the accuracy of digital core conductivity calculated by finite element method.