## 3 Results
### Development of the T\({}_{1}\)-T\({}_{2}\) Interpretation Scheme  
In the framework of rock analysis before and after the thermal exposure, we did not have an opportunity to employ the multistage NMR analysis of the rock at different states of saturation. For this reason, we conducted a detailed NMR analysis of 5 core plugs (n1-n5) in order to develop the T\({}_{1}\)-T\({}_{2}\) interpretation scheme for target collection prior to the main experimental section. The selected shale samples had similar petrophysical, geochemical properties, and lithotype. Figure 8: Pores in the sample #16 after the experiment. Figure 6: Shrinkage of OM, arrows indicate vacated space around an inclusion. SEM images of the sample #16 after the experiment. Figure 7: Newly formed fractures after the experiment on different scales, (**A**) sample #16, (**B**,**C**) sample #12. The core plugs underwent a 4-step routine core analysis, including drying, a saturation of the rock with water and decane. For each of the samples studied, an individual interpretation of T\({}_{1}\)-T\({}_{2}\) maps was carried out, and the values of water and oil saturation were calculated. An example of the T\({}_{1}\)-T\({}_{2}\) maps for representative sample n5 is illustrated in Figure 9. We observed the change of fluid signal of the rock at different stages of saturation. This enabled fluid separation in the sample based on the information obtained. An increase in the fluid viscosity is accompanied not only by changes in the T\({}_{1}\) and T\({}_{2}\) relaxation times but also, most importantly, by the ratio of longitudinal relaxation time to transverse relaxation time T\({}_{1}\)/T\({}_{2}\). As an empirical basis for the interpretation of the two-dimensional distributions of T\({}_{1}\)-T\({}_{2}\) for shale, first, the statements of [PERSON] et al. [28] obtained for gas- and oil-bearing shales, as well as the two-dimensional distributions of [PERSON] et al. [50] are widely used. The algorithm for investigating oil shale using NMR with an operating frequency of 2-MHz is discussed in the works of [PERSON] et al. [51]. A qualitative interpretation of 2D T\({}_{1}\)-T\({}_{2}\) distributions is proposed in accordance with the conditional algorithm presented in the paper of [PERSON] et al. [52]. The separation of water-oil-type fluids, as well as the pore space geometry, is based on the apparent contrast of the T\({}_{1}\)/T\({}_{2}\) ratio for the various pore populations. Recently, many scholars have presented their own interpretation schemes of T\({}_{1}\)-T\({}_{2}\) maps for shale rock [53; 20; 54; 55; 56]. The most detailed identification is yielded at higher frequency (\(\sim\)20-MHz) NMR units, whereas the 2-MHz units are limited to the resolution in the field of low T\({}_{2}\) relaxation times. Therefore, for the identification of the signal, we mainly referred to the simplified scheme by [PERSON] et al. [57]. In the as-received or primary saturation state, there is an insignificant signal region of reduced T\({}_{1}\)/T\({}_{2}\) (2-10 ms/ms) and low T\({}_{2}\) (less than 1 ms) area, which is responsible for water bound by clay minerals (Figure 9a)--drying the sample results in a significant change in the NMR signal in the clay and bound water region of the porous medium (Figure 9b). T\({}_{1}\)-T\({}_{2}\) maps (Figure 9a-d) show that decane resaturation is predominantly indicated by an increase in NMR signal due to the T\({}_{1}\)-T\({}_{2}\) distribution region with low T\({}_{1}\)/T\({}_{2}\)\(\sim\) 1 and long T\({}_{2}\) (40-300 ms), which indicates the filling of large pores of the inorganic matrix (IP--inorganic porosity). This proportion in the structure of the void space of the sample is dominant. With a small number of large pores, the NMR signal in the region of long T\({}_{2}\) is  
Figure 9: T\({}_{1}\)–T\({}_{2}\) maps of BF sample—Sample n5—in (**a**) as-received state; (**b**) dried state; (**c**) decane-saturated state; (**d**) brine-resaturated state. usually leveled.