Effect of Adsorption in Flow of Gases in Organic Nanopores: A Molecular Dynamics Study. Mohammad Kazemi Ali Takbiri-Borujeni West Virginia University

Transcription

1 Effect of Adsorption in Flow of Gases in Organic Nanopores: A Molecular Dynamics Study Mohammad Kazemi Ali Takbiri-Borujeni West Virginia University

2 Multiscale Nature of Gas production Slide 2

3 Slide 3 Flow in Organic Matter (1) 1- The pore sizes are so tight and are in nanometer scale 2- Adsorption adds more complexity in modeling flow of gases in these resources. 1. Loucks, R. G., Reed, R. M., Ruppel, S. C., & Jarvie, D. M. (2009). Morphology, Genesis, and Distribution of Nanometer-Scale Pores in Siliceous Mudstones of the Mississippian Barnett Shale. Journal of Sedimentary Research, 79(12),

4 Problem Statement: Nanopores Flow regime is characterized by Knudsen number. Slide 4 L The gas flow cannot be modeled using Darcy s or Navies- Stokes equations Taheri, P., Torrilhon, M., & Struchtrup, H. (2009). Couette and Poiseuille microflows: Analytical solutions for regularized 13-moment equations. Physics of Fluids, 21(1),

5 Flow Regime Characterization Slide 5 Ref: In organic nanopores in shale, Knudsen number is larger than Kang, S. M., Fathi, E., Ambrose, R. J., Akkutlu, I. Y., Sigal, R. F., & others. (2011). Carbon dioxide storage capacity of organic-rich shales. Spe Journal, 16(4),

6 Problem Statement: Adsorption Slide 6 Methane molecules Graphite walls Modeling studies (1,2) have indicated that molecular transport rates inside carbon nanotubes are orders of magnitude higher than in all other microporous materials. 1. S. K. Bhatia, H. Chen, and D. S. Sholl, Mol. Simul. 31, (2005) 2. A. I. Skoulidas, D. M. Ackerman, J. K. Johnson, and D. S. Sholl, Phys. Rev. Lett. 89, (2002)

7 Slide 7 Questions to be answered: 1. Does the adsorbed phase contribute to the flow? 2. Does the system properties (such as pressure) affect the flow? Diffusion or Advection?

8 Slide 8 Methodology: Molecular Dynamics Simulations Molecular simulation is a powerful tool to study transport in shale nanopores with inhomogeneous fluid density. The forces on each atom depend on position of other atoms. Interatomic potential

9 Slide 9 The Lennard-Jones is one of the most common interatomic potentials. = + OPLS-All Atom Force Field Loerentz-Berthelot Combination rules: Ref:

10 Slide 10 Adsorption: Grand Canonical Monte Carlo (GCMC) GCMC simulations are performed to study the adsorption of different gas types in carbon nanochannel. Molecular insertion and deletion is occurred inside the nanotube and no pressure driven flow exists.

11 Non-Equilibrium Molecular Dynamics (NEMD)

12 Simulation Setup LAMMPS 1 software is employed for MD simulations and VMD 2 software is used for visualizations. simulations Height: 2 nm 4 nm 6 nm 8 nm Gases: Argon Methane Knudsen: Pressure Gradients: Three different pressure Gradients for each pressure

13 Adsorption Isotherms-Multilayer Assumption Excess Adsorption=Total gas amount in pore gas amount in absence if walls Absolute Adsorption=Total gas amount in pore

14 Velocity and Density Profiles- Methane Plug shape flow profile exists for all channel sizes despite the higher density of methane near the walls. Navier-Stokes Equation

15 Velocity and Density Profiles- Argon Plug shape flow profile exists for all channel sizes despite the higher density of methane near the walls.

16 Molecular Fluxes

17 Diffusive or Advective Flow? = =

18 Diffusion Coefficients Diffusion coefficients sorted in terms of Knudsen number.

19 Kerogen vs. Graphite Channel

20 Kerogen Adsorption and Transport

21 Conclusions Transport and adsorption of methane and argon is studied by performing GCMC and force-driven flow. Plug shaped flow profile are established for both gases for all channel sizes and Knudsen numbers in contrary to well known models such as Navier-Stokes equation. Transport through organic pores is essential diffusive. To have a realistic model for predicting the recovery of fluids from unconventional resources, the transport equations in organic nanopores should be replaced by the diffusive transport equations.

22 Thank You Authors acknowledge use of Super Computing System (Spruce Knob and Mountaineer) at WVU, which are funded in part by the National Science Foundation EPSCoR Research Infrastructure Improvement Cooperative Agreement # , the state of West Virginia (WVEPSCoR via the Higher Education Policy Commission) and WVU.