GB/T 18295-2026 Microbeam analysis—Analysis method of sandstone sample of petroleum and gas reservoir by scanning electron microscope English, Anglais, Englisch, Inglés, えいご
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ICS
CCS
National Standard of the People's Republic of China
GB/T 18295-2026
Microbeam analysis - Analysis method of sandstone sample of petroleum and gas reservoir by scanning electron microscope
微束分析 油气储层砂岩样品扫描电镜分析方法
Issue date: 2026-02-27 Implementation date: 2026-09-01
Issued by the General Administration of Quality Supervision, Inspection and Quarantine of the People's Republic of China
the Standardization Administration of the People's Republic of China
Contents
Foreword
Introduction
1 Scope
2 Normative References
3 Terms and Definitions
4 Principle
5 Instruments, Software and Materials
6 Specimen Preparation
7 Test Procedure
8 Analysis Procedure
9 Analysis Report
Annex A (Informative) Description of mineral types and occurrences of sandstone cements
Annex B (Informative) Types of diagenetic and epigenetic alterations in sandstone
Annex C (Informative) Test parameter record sheet and analysis report format
Bibliography
Microbeam analysis - Scanning electron microscopy method for analysis of oil and gas reservoir sandstone samples
1 Scope
This document describes the principles, instruments, software and materials, specimen preparation, test procedure, analysis procedure and analysis report for scanning electron microscopy analysis of oil and gas reservoir sandstone samples.
This document applies to the scanning electron microscopy analysis of sandstone samples, and also to the scanning electron microscopy analysis of sandy components in rocks such as mudstone, shale and coal rock.
2 Normative references
The contents of the following documents constitute essential provisions of this document through normative reference. For dated references, only the edition cited applies. For undated references, the latest edition (including all amendments) applies.
GB/T 17359-2023 Microbeam analysis - Quantitative analysis of elements with atomic numbers not less than 11 using energy dispersive spectrometry
GB/T 17361 Microbeam analysis - Identification of authigenic clay minerals in sedimentary rock by scanning electron microscope and energy dispersive spectrometer
GB/T 27788 Microbeam analysis - Guideline for calibration of magnification of scanning electron microscope images
3 Terms and definitions
For the purposes of this document, the terms and definitions given in GB/T 17359-2023, GB/T 17361, GB/T 27788 and the following apply.
3.1 detrital grain
Granular primary materials (including quartz, feldspar and rock fragments, etc.) that constitute sandstone.
3.2 cement
Authigenic minerals formed by chemical precipitation in intergranular pores.
3.3 matrix
Fine grained detrital material deposited mechanically.
NOTE: Includes fine silt and clay.
3.4 pore
Spaces surrounded by solid parts of the rock that are not filled by detrital grains, cements or matrix.
3.5 throat
A narrow channel connecting two adjacent pores.
NOTE: One throat connects two pores, while one pore typically connects multiple throats. When the pore/throat diameter ratio approaches unity for large pores and coarse throats, both are classified as pores.
3.6 visual porosity
The percentage of the area of pores and throats in the total area of a scanning electron microscope image.
3.7 overgrowth
The phenomenon in which the surface of a detrital grain regrows the same mineral along its original crystallographic orientation during diagenesis.
NOTE: Minerals prone to overgrowth in sandstone include quartz, potassium feldspar, albite, etc.
3.8 leaching
The geological process in which formation water (or diagenetic fluid) selectively dissolves soluble components in detrital grains or cements, leading to the destruction of mineral structures and an increase in porosity.
NOTE: Minerals prone to leaching in sandstone include evaporite minerals (e.g., gypsum, halite), carbonate minerals (e.g., calcite, dolomite), feldspar minerals (e.g., potassium feldspar, albite) and zeolite minerals (e.g., heulandite, laumontite), etc.
3.9 metasomatism
The process in which, under the action of temperature, pressure and fluids (hydrothermal solutions, pore water, etc.), the original mineral undergoes material component exchange with the external medium, is replaced by a new mineral through a chemical reaction in an equal volume manner, and retains its original morphological characteristics (pseudomorph).
NOTE: Minerals prone to metasomatism in sandstone include carbonate minerals (e.g., calcite, aragonite), feldspar minerals (e.g., potassium feldspar, plagioclase), ferromagnesian minerals (e.g., pyroxene, amphibole) and clay minerals (e.g., montmorillonite, illite), etc.
4 Principle
This document uses scanning electron microscopy to characterise natural fracture specimens and argon ion beam polished specimens of sandstone samples, obtaining information on mineral types (such as cements), pore and throat characteristics, overall visual porosity and overall mineral composition, thereby enabling a qualitative evaluation of the reservoir.
To observe the natural morphological characteristics of minerals in sandstone samples, natural fracture specimens shall be prepared. During specimen preparation, damage such as liquid contamination and detachment of mineral particles shall be avoided. Subsequently, electron microscopy imaging and energy dispersive spectrometry analysis shall be performed, followed by the determination of mineral types (such as cements) and the description of their occurrence.
To observe the pore and throat characteristics of sandstone samples, argon ion beam polished specimens shall be prepared to expose the true pore throat network obscured by detrital minerals, matrix, etc. Subsequently, electron microscopy imaging and analysis shall be performed, followed by the determination of pore types and throat types, and the measurement of pore and throat dimensions.
To obtain the overall visual porosity of a sandstone sample, large area mosaic imaging shall be performed on the argon ion beam polished specimen. Phase segmentation based on image grey values shall be performed to delineate pores, and the visual porosity shall be calculated.
To obtain the overall mineral composition of a sandstone sample, backscattered electron (BSE) imaging and energy dispersive spectrometer mapping analysis shall be performed on the argon ion beam polished specimen. Using the atomic number contrast and elemental data at each measurement point, mineral phases shall be identified based on a standard mineral characteristic database, and the overall mineral composition shall be obtained.
5 Instruments, software and materials
5.1 Instruments
The main instruments include:
a)Scanning electron microscope (secondary electron image resolution preferably better than 2 nm, backscattered electron image resolution preferably better than 5 nm);
b) Energy dispersive spectrometer (effective crystal area preferably greater than 20 mm², element analysis range Be⁴ to U⁹²);
c) Vacuum coater or ion sputter coater (preferably with film thickness detection capability);
d) Argon ion beam polishing machine (polishing area preferably greater than or equal to 1
