Probabilistic assessment of the permeability of the deposits of the upper part of the Tyumen suite of the Shaim oil and gas region

The work is devoted to the problem of increasing the reliability of the calculation of the permeability cube in the construction of a threedimensional geological model. The common method of mechanically transferring the relationship between porosity and permeability, obtained on the basis of the approximation of the results of the study of the core, gives too vague result since neither the differences in the sizes of cells and samples, nor the large scatter of the values of the analyzed dependencies are taken into account. Instead, it is proposed to use stochastic methods to calculate permeability histograms for each elementary cell. First, the analysis of the results of determining the petrophysical properties performed in the laboratory is carried out. For rocks with similar porosity values, the probability of occurrence of rocks whose permeability exceeds a number of threshold values is calculated. Then, for each threshold value of permeability, empirical dependences of the probability of exceeding a given value on porosity are determined. At the next stage, the obtained results are adapted to the cell scale. The Monte Carlo method is used. Each cell is represented as a set of a large number of rocks, the sizes of which are close to those of the samples. Each virtual rock is assigned a porosity using a random number generator in such a way that the average value of the cell porosity is stored. For each conditional rock, the probabilities of exceeding the corresponding permeability thresholds are calculated. Based on the porosity cube for each cell, the probability of existence of all permeability ranges is automatically calculated for each cell. The authors provide examples of the implementation of the proposed methodology in the study of terrigenous deposits of the Tyumen suite of the Shaim oil and gas region.