Fig.1

Stratigraphic column of the Sinian Doushantuo formation, eyangye 1 well

Table 1

Basic parameters of the 20 shale cores and multifractal parameters of their T2 spectra

Fig.2

(a) T2 spectra of the 20 shale cores with fully saturated salt water; (b) Normalized cumulative curve of T2 spectra

Fig.3

The pore size distributions of black carbonaceous shale core (5#) and gray-black dolomitic shale core (13#) acquired with NMR

Fig.4

Multifractal analysis of the T2 spectra of the 5# shale core. (a) Log-log plots of the partition function versus different box scales; (b) The mass functional spectrum q~τ(q); (c) The generalized dimension spectrum q~D(q); (d) The multifractal spectrum α~f(α)

Fig.5

Pore structure analysis for three types of shale cores. (a) Normalized cumulative curves of T2 spectra; (b) The generalized dimension spectra q~D(q); (c) The multifractal spectra α~f(α)

Fig.6

Intersection graph between spectral width Δα and the difference of minimum and maximum generalized fractal dimension (Dmin-Dmax)

Table 2

The distribution ranges and average values of the multifractal characteristic parameters of the three typesof pore structures in 20 shale cores

Fig.7

Three types of T2 spectra based on multifractal parameter classification. (a) type Ⅰ; (b) type Ⅱ; (c) type Ⅲ; (d) Average T2 spectra

Table 3

The distribution ranges and average values of NMR porosity, T50 and pore ratio of the three types of pore structures in 20 shale samples