Adjusting porosity and permeability estimation by nuclear magnetic resonance: a case study from a carbonate reservoir of south of Iran

S M Fatemi Aghda,A Fahimifar,M Taslimi

doi:10.1007/s13202-018-0474-z

Abstract

The aim of this study is to assess the accuracy of nuclear magnetic resonance (NMR) method in estimating the porosity and permeability in a carbonate reservoir located in south of Iran. In this study, 26 carbonate samples were selected and common core and NMR experiments were performed. Comparison of core and NMR porosity showed that NMR method is very accurate for estimation of porosity. However, after comparison of core and NMR permeability, it was found that NMR permeability estimation cannot be used with the common coefficients since they are calibrated in the clastic reservoirs. Therefore, it is necessary to modify coefficients in the permeability models of the considered reservoirs. For this purpose, 16 samples were selected to develop the model, and 10 samples for evaluating the accuracy of the model. In this study, free-fluid and mean T2 models were two main models for permeability estimation using NMR method. Coefficients of the two above-mentioned models were modified in terms of maximizing the coefficient of determination of core permeability and calculated permeability using NMR permeability models. The proposed models were used to estimate permeability in 10 other samples for verifying the reliability of models.

Highlights

Porosity indicates the amount of pore spaces in the rocks; and permeability represents the capacity of rocks to transmit fluids
It should be specified to what extent is the accuracy of nuclear magnetic resonance (NMR) method for determining porosity in the samples
In this study it was shown that using NMR method, the porosity in the carbonate samples can be estimated well

Summary

Introduction

Porosity indicates the amount of pore spaces in the rocks; and permeability represents the capacity of rocks to transmit fluids. It is not difficult to determine the porosity of rocks directly in the laboratory, and it can be done in different ways. Determination of the permeability of rocks is difficult for various reasons such as high cost, time consuming and lack of enough samples. NMR technology (in laboratory and well logging) has had many applications in the oil industry from 1990 onwards, for determining various parameters of rock and fluid such as porosity, fluid type, pore size distribution, and permeability (Kenyon 1992; Kleinberg et al 1993; Kenyon et al 1995a, b; Kleinberg 1996; Straley et al 1997; Coates et al 1999; Al-Mahrooqi et al 2003; Alvarado et al 2003; Westphal et al 2005).

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