Development of a Permeability Formula for Tight and Shale Gas Reservoirs Based on Advanced High-Precision Lab Measurement Techniques

Paulina Krakowska-Madejska,Magdalena Habrat,Paweł Madejski,Edyta Puskarczyk,Mariusz Jędrychowski,Marek Dohnalik

doi:10.3390/en14092628

Paulina Krakowska-Madejska, Magdalena Habrat + Show 4 more

Open Access

https://doi.org/10.3390/en14092628

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Abstract

Computed X-ray tomography (CT), together with pulse and pressure decay permeability methods were used to evaluate a formula for absolute reservoir permeability. For this reason, 62 core samples representing geological material of tight, gas-bearing sandstones, mudstones, limestones, and dolostones were studied. Samples were divided into two groups with lower and higher permeability values. Images of the pore space were processed and interpreted to obtain geometrical parameters of the objects (pores, microfractures) with 0.5 × 0.5 × 0.5 µm3 voxel size. Statistical methods, which included basic statistical analysis, linear regression, and multiple linear regression analysis, were combined to evaluate the formula for absolute permeability. It appeared that the following parameters: Feret Breadth/Volume, Flatness/Anisotropy, Feret Max/Flatness, moments of inertia around middle principal axis I2/around longest principal axis I3, Anisotropy/Flatness, Flatness/Anisotropy provided the best results. The presented formula was obtained for a large set of data and is based only on the geometric parameters of the pore space. The novelty of the work is connected with the estimation of absolute permeability using only data from the CT method for tight rocks.

Highlights

New methods to evaluate the absolute permeability in low-porosity and low-permeability rocks are a challenge for the petroleum industry [1,2,3,4]
One of the equations used for permeability estimation is built based on the porosity and specific surface area of a porous material Svgr
The geometrical parameters of the pore space for all 62 samples were checked conThe geometrical parameters of the pore space for all 62 samples were checked considering the value reliability and being within the correct range

Summary

Introduction

New methods to evaluate the absolute permeability in low-porosity and low-permeability rocks are a challenge for the petroleum industry [1,2,3,4]. One of the equations used for permeability estimation is built based on the porosity and specific surface area of a porous material Svgr (the total area exposed within the pore space per unit of grain volume). The Kozeny equation is reasonable for use when the pore space structure is similar to the set of straight capillary tubes, and the porosity is relatively high. These requirements cannot be satisfied, especially in tight rocks [6,7,8,9,10]. Assessment of absolute permeability will always be a top problem to solve because it is a key parameter in evaluating fluid flow abilities in reservoirs [21,22]

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