Nuclear magnetic resonance study on the evolution of oil water distribution in multistage pore networks of shale oil reservoirs

Shale reservoirs are rich in micro and nanoscale pores and fractures, resulting in a very complex interaction mechanism between oil and water. In this paper, firstly, the differences in fluid enrichment mechanisms and evolution model characteristics within multi-level pore networks are revealed. Secondly, a linkage mechanism model of “relaxation time - multistage pore structure - fluid evolution” is constructed. Thirdly, the interaction mechanism of the coupling of mineral types, multiphase fluid evolution, and pore-fracture networks is clarified. Results show that: (a) For the 4 shale samples, the distribution of p1 peak is less than 1 ms, p2 peak is between 1 ms and 20 ms, and p3 peak is greater than 20 ms. (b). The distribution of p1, p2, and p3 peaks in the T2 spectrum of saturated oil from different shale samples is different. (c) For a typical sample, the total porosity of saturated water in the felsic shale in Research Area 1 is 6.73%; the total porosity of saturated oil is 4.15%.