Forward simulation and characteristic analysis on the low field NMR
transverse relaxation response of fractured shale reservoir
Abstract
Nuclear magnetic resonance technology can be used to simulate the T2
spectrum distribution characteristics of different fracture parameters
of fractured shale. Based on scanning electron microscope data of
lacustrine shale strata, a petrophysical model of fractured shale is
established, and the shapes of pores and fractures are simplified into
spheres and ellipsoids, respectively. According to the aspect ratio of
the ellipsoid and the log Gaussian function to control the crack shape.
The simulation results show that the NMR response of fractured shale is
unique, which is related to fracture shape, fracture width and fracture
density. The fracture width has a greater influence on the T2 spectrum
distribution of fractured shale. With the increase of the crack width,
the T2 spectrum distribution shows a “double peak”-“single
peak”-“double peak” trend. As the crack density increases, the T2
spectrum distribution changes from “single peak” to “double peak”.
The shale model with needle-shaped fractures contributes the most to the
connectivity of the pore-fracture model, and the shale model with
pie-shaped fractures contributes the least to the connectivity of the
pore-fracture model.