Method to Generate Random Element Equivalent Core Models Based on the NMR T 2 Spectrum for Waterflooding in Tight Sandstone.

Abstract

Numerical simulation based on the widely used homogeneous equivalent core model can solve the problem of high cost and long duration of coreflooding experiments. However, using the homogeneous equivalent core model, it is difficult to reflect the characteristics of the core interior during waterflooding. In this paper, we provide a method to generate random element equivalent core models based on the nuclear magnetic resonance (NMR) T2 spectrum, and it can divide permeability regions by granularity. The permeability calculation formula derived from the complementary correlation principle ensures that most areas of the core satisfy the correlation between permeability and T2 relaxation time. Moreover, the generation method can guarantee that the random element equivalent core model is consistent with the homogeneous equivalent core model in terms of the geometric mean of permeability. The simulation results show that the high-resolution random element equivalent core model can better simulate microcosmic fingering inside the core during waterflooding. Nevertheless, the proposed method has some limitations emanating from the demarcation criteria and the porosity assumption. Furthermore, the generation method is expected to be extended to simulate enhanced oil recovery (EOR) mechanisms on the core scale after waterflooding.