Unconventional oil and gas are playing a more and more important role in the global energy supply and clean energy future. Because of some unique features of unconventional formations like low permeability special pore structure and the existence of organic matter, more understanding of unconventional formations and core analysis methods are needed. This thesis focuses on how to apply Nuclear Magnetic Resonance (NMR) techniques to understand fluid properties in unconventional formations. NMR is a powerful nondestructive method to analyze the fluid in porous media. By applying different pulse sequences, various petrophysical properties can be derived like porosity, fluid distribution, relaxation times, and diffusivity.

First, permeability estimation is crucial for formation evaluation and becoming a challenge in understanding low-permeability, unconventional formations. NMR well logging is often used to estimate formation permeability but in many unconventional formations, the current NMR methods are not adequate. To overcome the challenge, a new method is developed to estimate permeability. This method uses a modified Carman-Kozeny model with pore size, tortuosity, and porosity information inferred from NMR diffusion measurements. Another variant for the ultra-low permeability scenario is also developed using D2O diffusion measurements for the scenario where NMR diffusion measurements are limited in some ultra-low permeability shales.

Second, to better understand the NMR relaxation mechanism in shale formations and interpret the porosity and saturation from logs, the correlations between relaxation times and oil/water saturation are investigated by NMR T_1-T_2 measurements on partially saturated samples. This methodology overcomes the challenges due to potential overlapping signals in unconventional formations between micropore water and bound hydrocarbon, and, macro-pore water and hydrocarbons.

Last but not the least, NMR is used to investigate the relaxation mechanism of fluids in kerogen, which is one type of organic matter in formations. To better understand the fluid relaxation mechanisms, intergranular and intragranular fluids in kerogen isolate pellets are studied. Different frequencies are compared when analyzing fluid in kerogen. It is found that the maturity can have impacts on intragranular relaxation times and porosities. The effects of diffusive coupling are also investigated and discussed.

This thesis focuses on applying NMR technique to understand and do core analysis for unconventional formations. Several new methods are proposed to estimate permeability, macro-pore saturation and analyze fluid in kerogen. In principle, these new methods and techniques can be used to better understand unconventional formations.