# NMR Evaluation of Shale Oil Mobility: Combined Pyrolysis and CO\({}_{2}\) [PERSON]
## 3 Results and Discussion  
### Pyrolysis-NMR Experimental Results  
Shale powder samples were subjected to a multistage pyrolysis experiment following the temperature sequence shown in Figure 1, and 2D NMR spectra were measured at each state to ascertain the component distribution. Figure 3 displays the 2D NMR \(T_{1}\)-\(T_{2}\) spectra of the powder samples in their original state and after multistage pyrolysis. The 2D NMR spectrum utilizes the \(T_{2}\) to characterize the pore distribution of the sample, while the \(T_{1}\) characterizes the fluid viscosity corresponding to different pore distributions within the sample. By integrating the saturation and pyrolysis states of the sample, a comprehensive evaluation of the fluid types present in the sample can be achieved. The changes in the signal intervals of the 2D spectrum are used to determine the storage space of different types of fluids. When the sample was heated from its original state to 60 \({}^{\circ}\)C, there was no significant change in the signals of the 2D spectrum. In terms of the temperature characteristics of oil and water, the fluid components at this temperature stage correspond to free water and capillary water, indicating that there is essentially no free water in the sample. As the sample was further heated to 200 \({}^{\circ}\)C, the signal in region 3 of the 2D  
Figure 2: Workflow of CO\({}_{2}\) huff-n-puff experiment.  
spectrum decreased, with only water being released, not oil. According to the temperature characteristics of oil and water, the nature of water between 60 \({}^{\circ}\)C and 200 \({}^{\circ}\)C is clay-bound water, thus this region is identified as clay-bound water. When the temperature was further increased to 350 \({}^{\circ}\)C, both water and oil were released. The signal in region 3 of the 2D spectrum further decreased, indicating that the water in this region also includes structural water derived from pyrolysis, and region 3 contains structural water. At the same time, the signal in region 4 decreased, and according to the pyrolysis rules, this part is medium oil. At 450 \({}^{\circ}\)C, the release of water and oil continued, with a decrease in region 3's signal confirming it as structural water and region 2 as hydrocarbons, comprising heavy oil and asphaltene. Upon reaching 600 \({}^{\circ}\)C, both water and oil were released, and changes occurred in regions 1 and 3 of the 2D NMR spectrum. Region 3 has been identified as structural water, while region 1 showed a continuous decrease in signal throughout the heating process and still had a residue after 600 \({}^{\circ}\)C. Between 450 \({}^{\circ}\)C and 600 \({}^{\circ}\)C heating, the hydrocarbons are derived from the pyrolysis of kerogen, and region 1 is ultimately identified as kerogen. We conducted pyrolysis experiments on powder samples in their original state, where the movable components have almost completely volatilized. The residual bound and non-fluid components, including asphaltene, kerogen, and structural water, are less affected by volatilization. Asphaltene may undergo cracking to produce low molecular weight hydrocarbons before 450 \({}^{\circ}\)C, but in the actual experiments, we added a 400 \({}^{\circ}\)C pyrolysis-NMR testing to a fragment sample and found that the fluid distribution in the 2D NMR spectrum was essentially the same as that obtained from the 350 \({}^{\circ}\)C pyrolysis-NMR testing. The high-temperature exposure had a negligible effect on the distribution of non-fluid components in the NMR spectrum, inducing only a minor variation in signal intensity. Thus, through multistage pyrolysis-NMR joint experiments, the identification of shale components on the 2D NMR \(T_{1}\)-\(T_{2}\) spectrum was successfully achieved. Applying this method to additional samples enables the acquisition and quantitative description of component distribution, establishing a basis for future research on component division.  
Figure 3: NMR \(T_{1}\)-\(T_{2}\) spectra of the original state and multistage pyrolysis of powder samples.