# NMR Evaluation of Shale Oil Mobility: Combined Pyrolysis and CO\({}_{2}\) [PERSON]
## 1 Introduction  
Shale oil typically refers to petroleum resources stored in shale formations and can be divided into two definitions of broad and narrow. Broadly, it includes petroleum resources in low-porosity, low-permeability tight oil-bearing strata, including interbeds. Narrowly, it is specific to petroleum resources confined to source rocks, such as shaly mudstones [1, 2, 3, 4]. As conventional resource reserves diminish, shale oil has become a key area of research because of its considerable potential as an unconventional resource. However, the complexity of shale oil storage space and occurrence mechanisms makes the evaluation of its mobility and recoverability challenging [5]. Shale reservoirs exhibit a complex fluid state, housing oil and water in various forms, including free and adsorbed phases [6]. Moreover, the rock framework within these reservoirs, which contains organic matter and clay minerals, influences the state of fluid components. This adds complexity to the study of fluid components and their mobility. Thus, identifying the oil and water components within shale and assessing their mobility are the primary issues that need to be addressed in the development of shale oil. Researchers initially focused on identifying the types and quantities of hydrocarbon components in shale. Currently, there is no single method that comprehensively addresses the study of pore components such as oil, water, and organic matter. Commonly used research methods are primarily developed from the study of hydrocarbons in shale and include solvent extraction, pyrolysis, and nuclear magnetic resonance (NMR) techniques. The solvent extraction method leverages the principle that various components in the sample have different solubilities in specific solvents. It uses specific solvents to fully or partially separate the target components, thus distinguishing different constituents [7]. Nevertheless, this approach has notable limitations in distinguishing fluid components. The solvent selection significantly influences component extraction, and it is uncertain whether the final extract represents all hydrocarbons. Additionally, the efficiency of solvent and extract separation impacts the assessment of oil content. This method also only partially discriminates organic matter in shale samples and fails to investigate the occurrence of kerogen and other water components. Pyrolysis relies on the temperature characteristics of shale components to establish distinct temperature sequences and study the released components at various temperatures [8; 9; 10]. This method is more reliable for determining the properties of these components. Given the relatively consistent temperature properties of different components, pyrolysis is commonly employed for calculating shale fluid content. In shale oil evaluation, the pyrolysis parameter S\({}_{1}\) is a crucial parameter, as its value directly influences the assessed quantity of shale oil. Consequently, the pyrolysis S\({}_{1}\) method is the primary approach for differentiating and quantifying shale oil components. However, current pyrolysis research on shale mainly focuses on hydrocarbons, neglecting water studies and measurements, which limits its comprehensiveness in shale component analysis. Despite this, pyrolysis's temperature ramping method offers an experimental method and a reference for subsequent component studies. A critical factor in pyrolytic analysis is the selection of an appropriate pyrolytic temperature sequence, which should be designed according to the properties of the study area. The objective of shale component analysis is to accurately identify, distinguish, and quantify both hydrocarbon and aqueous phases, a goal well-suited to NMR techniques. NMR capitalizes on the \({}^{1}\)H NMR phenomenon, where different components have distinct nuclear magnetic relaxation mechanisms, enabling the differentiation of various components.