Estimation of permeability of a sandstone reservoir by a fractal and Monte Carlo simulation approach: a case study

U Vadapalli,V P Dimri,R P Srivastava,N Vedanti

doi:10.5194/npg-21-9-2014

Abstract

Abstract. Permeability of a hydrocarbon reservoir is usually estimated from core samples in the laboratory or from well test data provided by the industry. However, such data is very sparse and as such it takes longer to generate that. Thus, estimation of permeability directly from available porosity logs could be an alternative and far easier approach. In this paper, a method of permeability estimation is proposed for a sandstone reservoir, which considers fractal behavior of pore size distribution and tortuosity of capillary pathways to perform Monte Carlo simulations. In this method, we consider a reservoir to be a mono-dispersed medium to avoid effects of micro-porosity. The method is applied to porosity logs obtained from Ankleshwar oil field, situated in the Cambay basin, India, to calculate permeability distribution in a well. Computed permeability values are in good agreement with the observed permeability obtained from well test data. We also studied variation of permeability with different parameters such as tortuosity fractal dimension (Dt), grain size (r) and minimum particle size (d0), and found that permeability is highly dependent upon the grain size. This method will be extremely useful for permeability estimation, if the average grain size of the reservoir rock is known.

Highlights

Permeability is one of the important parameters that govern production of hydrocarbons from reservoirs
Fluid flow in reservoirs depends upon permeability, and in the case of multiple phases of hydrocarbons, it is relative permeability that governs the fluid flow
There are numerous examples that present the application of fractal geometry to analyze porous media

Summary

Introduction

Permeability is one of the important parameters that govern production of hydrocarbons from reservoirs. In the literature many empirical relations are available for computation of permeability from porosity (Kozeny, 1927; Carman, 1956; Pape et al, 1999) These empirical relations define the porosity–permeability relationship in terms of correlation coefficients without addressing the real physical situation existing in a porous medium. Even for a given effective porosity, permeability will be different for different rock types This is because in addition to porosity, permeability depends upon textural parameters such as grain size, grain shape and sorting of grains. These textural parameters affect the tortuous nature of capillary pathways and the arrangement of pores in the porous medium, thereby making it more complex to understand.

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Conclusion