Application of NMR to Test Sandstone Stress Sensitivity of the Dongfang X Gas Field, China

Abstract

The stress sensitivity of reservoir rocks has captured considerable attention in the field of oil and gas development. In this paper, nuclear magnetic resonance (NMR) was employed to measure the T2 spectra of sandstone samples from Dongfang X gas field under different confining pressures. According to T2 values, the pores in sandstone samples were divided into macropores (right peak of T2 spectra) and micropores (left peak of T2 spectra), and the stress sensitivity of macropores and micropores were discussed separately. The results show that the increase of net effective stress will lead to the pore deformation of rock samples, and the pore deformation characteristics of rocks in different blocks under different net effective stress can be effectively analyzed by the NMR. As the net effective pressure increases, the compression amplitudes of rock samples in different blocks are almost equal, indicating that the reservoirs in the Dongfang X gas field have good homogeneity. In addition, the study rocks have a weak stress sensitivity, the general stress sensitivity of micropores is stronger than that of macropores. For the samples with high permeability (over 80mD), the compression amplitudes of macropores and micropores are relatively small and close, and the porosity losses are almost the same.