Determination of initial gas saturation in tight gas formations with NMR relaxometry measurements

作者：Zhang Shuo^*; Yang Ping; Jiang Peng; Zhang Tingting

来源：Journal of Natural Gas Science and Engineering, 2015, 27: 1512-1517.

DOI：10.1016/j.jngse.2015.10.018

• Tight gas reservoir
• Sealed coring technique
• Initial gas saturation
• NMR
• T-2 cutoff

The NMR relaxometry measurements are designed and applied to determine the initial gas saturation in tight gas formations. After a full-diameter core obtained by sealed coring technique has been cut into two sections, one is weighed and then put into the NMR apparatus to measure its NMR T-2 spectrum, while the other is used to obtain a core plug, and some clastic grains from its edge and center. Afterward these grains are weighed and their NMR T-2 spectra are measured. Subsequently, the full-diameter section, grains, and the core plug are dried with their weights measured. Then they are saturated with water to measure their weights and NMR T-2 spectra. It is found that the average initial gas saturations for three cores determined by weighting method are 41.87%, 38.59%, and 31.30%, respectively. From T-2 spectra at the initial state and saturated-water state, the average initial gas saturations for these cores could be reproduced with a relative error of 0.29%, 1.37%, and 0.40%, respectively. If the cores are invaded by drilling fluid or not transported or preserved well, the initial gas saturations still could be determined by NMR T-2 spectra of the cores at saturated-water state and T-2cutoff with a relative error of 7.86%, 3.28%, and 8.16%, respectively.

• 出版日期2015-11