Investigation of Stress Sensitivity of Shale Nanopores via a Nuclear Magnetic Resonance Method

Nuclear magnetic resonance (NMR) is widely used to characterize the pore structure of rock. The nanoscale pores and fractures are well developed in a shale gas reservoir. closure nanopores caused by increase effective stress during production process could induce sensitivity nanopores, which has great impact on single-well productivity middle–late development stage. In this paper, samples from Longmaxi Formation were taken investigate nanopore via an NMR method. Samples with different degrees fracture selected experiments under conditions carried out. results show that: (1) As increases, space continuously compressed, cumulative volume decreases; (2) There more pronounced decrease containing larger stress. However, there obvious differences changes sizes; (3) transformation sizes occurs loading. When small, diameters than 50 nm mainly transformed those 10–50 nm. increases certain extent, 0–10 nm; (4) significant compressibility sizes. Larger generally have higher compression coefficient stronger sensitivity. loading, between 10 relatively slowly, can well-maintain shape quantity. Based variation porosity ratio stress, new method dividing proposed; smaller nm,