A detailed characterization of the organic matter in sediments gives a key parameter for the correct evaluation of the petroleum generation potential of a source rock and its modeling in an oil system. To understand the features of the organic matter stored in source rocks, a wide variety of routine techniques are used. Those techniques are mostly destructive, time-consuming, and are not necessarily suitable for all the shale rocks. Thus, new technologies are being explored. XPS is a solid state, nondestructive, and direct method. It can be used to directly probe the speciation of organic carbon in sedimentary materials by C1s spectra measurements. In this work, we demonstrated that a heterogeneous layer of adventitious carbon (AC) is always present on the rock. This layer significantly altered the features of the organic compound fingerprint, which is measured by XPS of C1s. To acquire a reliable organic matter composition of a rock from XPS spectra it is necessary to remove the AC layer by sputtering it with Ar⁺. Further, the sputtering damage of the organic matter appears after an hour of radiation, and rocks become contaminated again during storage in the UHV chamber. The radiation damage by X-ray is also relevant in the XPS measurement of a rock. This damage is associated with an increment of AC contamination on the rock surface. To minimize this side effect, C1s spectra have to be measured immediately after the sputtering conditioning step. Thus, we developed a method for XPS measurements taking into account the AC contamination and radiation damage. We consider that the proposed method for outcrop shales can be applied to a wide range of rock sampling types, such as cuttings, damaged crowns, and so forth.

中文翻译：

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X射线光电子能谱表征页岩的有机质：不定碳污染和辐射损伤

沉积物中有机物的详细表征为正确评估烃源岩的生石油潜力及其在石油系统中的建模提供了关键参数。为了了解源岩中存储的有机物的特征，使用了多种常规技术。这些技术大部分是破坏性的，耗时的，并且不一定适用于所有页岩。因此，正在探索新技术。XPS是一种固态，非破坏性的直接方法。它可用于通过C1s光谱测量直接探测沉积材料中有机碳的形态。在这项工作中，我们证明了岩石上总是存在不定形碳（AC）的非均质层。该层显着改变了有机化合物指纹的特征，通过C1的XPS测量。为了从XPS光谱中获得可靠的岩石有机物组成，必须通过用Ar溅射将AC层去除⁺。此外，辐射一小时后，就会发生有机物的溅射损伤，并且在储存在特高压室中的过程中，岩石会再次受到污染。X射线的辐射损伤也与岩石的XPS测量有关。这种损坏与岩石表面AC污染的增加有关。为了最大程度地减少这种副作用，必须在溅射调节步骤之后立即测量C1s光谱。因此，我们开发了一种考虑到AC污染和辐射损伤的XPS测量方法。我们认为，所提出的露头页岩方法可以应用于各种岩石采样类型，例如切屑，损坏的树冠等。