(559m) NMR Relaxation and Diffusion in Model Organic Shale Using Molecular Simulations | AIChE

(559m) NMR Relaxation and Diffusion in Model Organic Shale Using Molecular Simulations


Asthagiri, D., Rice University
Singer, P., Rice University
Hirasaki, G. J., Rice University
Chapman, W., Rice University
The promising development in shale gas/oil makes it critical to understand fluid properties in pores of shale kerogen. Confinement in nanopores shifts the fluid phase behavior making exploration and production predictions challenging. As the pore shape, pore size and solid composition can all affect the fluid behavior, prediction of fluid properties in shale networks is still under study by many researchers. In this research, nuclear magnetic resonance (NMR) relaxation measurements of fluids in kerogen are analyzed with molecular dynamics (md) simulation, and molecular density functional theory (DFT) to predict hydrocarbon fluid distribution in kerogen.

NMR is extensively used to probe the pore size distribution, fluid distribution, and surface relaxivity of oil and gas reservoirs. However, the interpretation of these NMR-logs still depends on classical Bloembergen-Purcell-Pound (BPP) and Torrey models of NMR relaxation that make important assumptions about the nature of the molecules and its interaction with the environment. These models constrain our ability to interpret NMR logs, thereby hampering development of effective, and environmentally sound, ways to increase hydrocarbon yield. These fundamental limitations also have a bearing in other areas, including in medicine, where MRI is used. We use atomistic molecular dynamics simulations to enhance the understanding and interpretation of NMR relaxation in confined systems of interest in current oil and gas production. In our research team, NMR relaxation behavior of fluids in kerogen from a variety of sources is measured and analyzed with molecular dynamics simulation. Further, DFT is used to predict hydrocarbons absorbed in kerogen matrix and the distribution of hydrocarbons to nano-pores lined with permeable kerogen.

In this talk, we outline how we can use the atomistic simulations to obtain insights into NMR 1H dipole-dipole and spin-rotation relaxation mechanisms. We will discuss our results in modeling the NMR relaxation dynamics and diffusion in bulk hydrocarbons, and then the effect of nano confinement on the same. We conclude by noting some current directions that our team is pursuing.