Electron microscope identification method and device for residual oil in nanopores of tight reservoirs

Abstract

The invention relates to an electron microscope identification method for residual oil in light reservoir nanopores and a device for executing the method. The method comprises the following steps: obtaining an electron microscope sample; processing the electron microscope sample to obtain a flat section with exposed micro-nanopores; obtaining an back scattering image without an electric charge phenomenon on the flat section with the exposed the micro-nanopores, wherein the back scattering image without the electric charge phenomenon displays the micro-nanopores and distribution of the protogenetic organic matter; on the same imaging position, obtaining an back scattering image of residual oil charges, which displays the micro-nanopores and distribution of the protogenetic organic matter; respectively extracting the pores from the back scattering image without the electric charge phenomenon and the back scattering image of the residual oil charges to obtain distribution of the residual oil in a three-dimensional porous space, so as to realize identification of residual oil in the light reservoir nanopores.

Description

technical field [0001] The invention relates to the technical field of petroleum exploration, in particular to an electron microscope identification method and device for residual oil in nanopores of tight reservoirs, which are suitable for the characterization of unconventional reservoirs such as tight sandstone and tight carbonate rock. Background technique [0002] In my country, tight oil resources have huge potential and are widely distributed. Key areas include the Ordos Basin, Sichuan Basin, Bohai Bay Basin, Jiuquan Basin, Junggar Basin, etc. The reservoir lithology includes tight sandstone and tight carbonate rock. The storage space of tight reservoirs is mainly composed of micro-nano pore-throat systems. Nano-CT imaging technology, cross-sectional ion polishing technology, field emission scanning electron microscopy imaging, and focused ion beam scanning electron microscopy (FIB-SEM) imaging are used to analyze the pores of this scale. And other technologies have be...

AI Technical Summary

Problems solved by technology

At present, environmental scanning electron microscopy is mostly used for direct observation of residual oil. However, due to the influence of water and gas atmosphere on the signal of environmental scanning electron microscopy, its resolution is seriously lost compared with high vacuum mode, and its ability to distinguish nanopores is seriously reduced; due to the influence of kerogen The properties of various organic matter and residual oil under the electron beam are similar, and the identification of the two is difficult and easily confused; the evaluation of residual oil is often combined with EDX energy spectrum analysis, and because the energy spectrum only relies on the analysis of carbon and oxygen elements to determine the existence of organic matter , which cannot distinguish residual oil and kerogen, and the energy spectrum beam spot diameter is about 3 μm, and the penetration depth is about 1 μm, so the energy spectrum verification is greatly affected by the particles near the pores

Therefore, the above-mentioned various negative factors will cause errors or even fallacies in the evaluation process of residual oil, which seriously restricts the oil-bearing evaluation of tight reservoirs.

[0004] At present, except for environmental scanning electron microscopy combined with energy spectrum analysis, there is no microscopic analysis method for directly imaging residual oil, and the lack of technology seriously restricts the analysis of oil-bearing samples in tight reservoirs

Images