A new approach to heterogeneity analysis in a highly complex carbonate reservoir by using borehole image and conventional log data

Mehdi Tadayoni,Mahmoudreza Khalilbeyg,Radzuan Bin Junin

doi:10.1007/s13202-020-00930-4

Mehdi Tadayoni, Mahmoudreza Khalilbeyg + Show 1 more

Open Access

https://doi.org/10.1007/s13202-020-00930-4

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Abstract

This study outstretches a new method to specify the heterogeneity of the studied reservoir by combining BHI (Borehole Image Log) and conventional log data for 4 existing wells. The first step to achieve this goal was utilizing borehole electrical images to assess the quantity of vugs/modals fraction and porosity distribution. Spectrum porosity was calculated through probabilistic analysis based on core and FMI data which has specified two general types of porosity in studied field as primary porosity (microporosities and intercrystalline) and secondary porosity (vugs). Due to irregular dispersion, non-categorization, and scattering of the porosity–permeability graph obtained from laboratory core data, next step was using petrophysical image facies prediction for generating an electrical facies to incorporate the different reservoir quality. This lithology (litho types) is produced by BHI analysis which reflects geological and petrophysical properties of the field. Then a porosity–permeability cross-plot has been made based on core data and produced facies codes which build in the previous step to check the validity of BHI Facies code extraction. Finally, heterogeneity analysis has been done through an innovative step-by-step workflow to determine spectrum porosity log which is divided into 6 categories/portions as Resistive, Matrix, Isolated, Connected, Bed boundaries and Fractures porosity.

Highlights

Most of the literature on reservoir characterization and petrophysics refers to reservoirs as being heterogeneous in nature
It is vital to fully comprehend the variability and distribution of petrophysical properties such as porosity and permeability throughout a reservoir. This is mainly correct in the case of carbonate reservoirs, which mostly have notable variability
Upper Shuaiba and Upper Mauddud Formations are the main intervals which have been exposing by meteoric water and based on image log in 4 wells these formations mostly contain bimodal and trimodal pores from matrix to vuggy porosity

Summary

Introduction

Most of the literature on reservoir characterization and petrophysics refers to reservoirs as being heterogeneous in nature. It is vital to fully comprehend the variability and distribution of petrophysical properties such as porosity and permeability throughout a reservoir. This is mainly correct in the case of carbonate reservoirs, which mostly have notable variability. Common reservoir heterogeneities include grain/rock component, grain size distribution, grain/rock distribution (mineralogy, fossils, and lithology), fluid distribution, pore system types, connectivity, sizes and cementation. These heterogeneities plainly affect petrophysical log responses (e.g. nuclear, resistivity and sonic) and derived petrophysical parameters such as porosity, saturation, and permeability (Fitch 2011)

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