Oil and natural gas prospecting requires precise pore characterisation of insulating rock samples, which involves severe charging problems in the state-of-art FIB-SEM tomography, such as overexposure, drift and distortion. For weak cemented samples with very poor conductivity, the conventional ways such as decreasing accelerating voltage or current as well as coating a thin layer of carbon or gold fail to eliminate all the detrimental effect, leading to image distortion in the form of lateral shift and longitudinal stretching. A new nanoprobe-assisted method is explored in FIB-SEM tomography to address this problem and improve image quality. To be specific, a metallic nanoprobe is induced and attached on the sample surface to create an express path for the export of excess electrons near the region of interest, which effectively removes distortion and drift when imaging. Two adjacent areas were characterised and reconstructed into 3D digital models by FIB-SEM tomography with nanoprobe-assisted method applied to one region only. The lateral shift creates zigzag feature for distorted region and the longitudinal stretching of undistorted object can reach 14%. Average pore size of distorted region is larger than that of the undistorted region, however considering the longitudinal stretching, the average pore size of distorted region can be corrected to the same level as the undistorted region. The systematic error caused by distortion for poorly conductive porous rock is hazardous for digital rock physics analysis. Therefore, the nanoprobe-assisted FIB-SEM tomography should be regarded as a one of the optional and feasible procedures in case decreasing accelerating voltage or current as well as coating a thin layer of conductive material does not work. This article is protected by copyright. All rights reserved.

中文翻译：

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通过纳米探针辅助 FIB-SEM 断层扫描重建不失真的导电性差的多孔岩石 3D 数字模型

石油和天然气勘探需要对绝缘岩石样品进行精确的孔隙表征，这涉及最先进的 FIB-SEM 层析成像中的严重充电问题，例如过度曝光、漂移和变形。对于导电性很差的弱胶结样品，传统的降低加速电压或电流以及涂覆一层薄薄的碳或金的方法无法消除所有不利影响，导致图像横向偏移和纵向偏移。伸展。在 FIB-SEM 断层扫描中探索了一种新的纳米探针辅助方法来解决这个问题并提高图像质量。具体而言，金属纳米探针被诱导并附着在样品表面，为感兴趣区域附近的多余电子输出创建一条快速路径，有效消除成像时的失真和漂移。通过 FIB-SEM 断层扫描对两个相邻区域进行表征并重建为 3D 数字模型，纳米探针辅助方法仅应用于一个区域。横向位移为扭曲区域创造了锯齿特征，未扭曲对象的纵向拉伸可达14%。畸变区域的平均孔径大于未畸变区域的平均孔径，但考虑到纵向拉伸，畸变区域的平均孔径可以校正到与未畸变区域相同的水平。导电性差的多孔岩石变形引起的系统误差对于数字岩石物理分析是危险的。所以，纳米探针辅助 FIB-SEM 断层扫描应被视为一种可选和可行的程序，以防降低加速电压或电流以及涂覆一层薄薄的导电材料不起作用。本文受版权保护。版权所有。