The application of Nuclear Magnetic Resonance T1-T2 maps in the research of sedimentary organic matter: A case study of early mature shale with type Ⅰ kerogen

Abstract

The Nuclear Magnetic Resonance (NMR) 2D T1-T2 map was widely used in shale resources for separation of the different proton contributions, and the obtained data provided lots of information for shale resources evaluation. However, the further work of its application in organic matter quantification and hydrocarbon generation research was quite limited. In this article, we used a low field NMR instrument working at a high frequency (15 MHz) to test isolated organic matter, raw oil shales and shale samples processed by pyrolysis respectively. The results indicated that the kerogen and bitumen could be distinguished by positions located in NMR 2D T1-T2 maps. The standard equations (the relationship between the signal intensity and the mass of isolated organic matter) with excellent linear relationship were established for firstly calculating the content of organic matter in oil shales. The results of NMR were almost identical with that tested by traditional methods. In addition, the NMR relaxometry measurements correlated well with geochemical properties of pyrolyzed oil shales obtained from Rock-Eval pyrolysis (S1 and S2).