Nano/Molecular Scale Petrophysics and Fluids. I. Yucel Akkutlu Harold Vance Department of Petroleum Engineering Texas A&M University, College Station

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1 Nano/Molecular Scale Petrophysics and Fluids I. Yucel Akkutlu Harold Vance Department of Petroleum Engineering Texas A&M University, College Station

2 Yucel Akkutlu Associate Professor Department of Petroleum Engineering Texas A&M University Research interests: Nano-scale and molecular phenomena Shale petrophysics Fluid flow, transport and reactions in heterogeneous porous media Related Publications: Wasaki, A., and Akkutlu, I.Y., Permeability of Organic-rich Shale. SPE , paper presented during the SPE ATCE in Amsterdam, the Netherlands, October Accepted for publication in SPEJ Bui, K., Akkutlu, I.Y Nanopore Wall Effect on Surface Tension of Methane. Journal of Molecular Physics, Fathi E., Tinni, A., and Akkutlu, I.Y Correction to Klinkenberg Slip Theory for Gas Flow in Nanocapillaries. International Journal of Coal Geology, special issue on Shale, Vol. 103, Ambrose, R.J., Hartman, R.C., Diaz-Campos, M., Akkutlu, I.Y., and Sondergeld, C.H Shale Gas inplace Calculations Part I - New Pore-scale Considerations. SPE Journal. Volume 17 (1)

3 Multi-scale Pore Network 4nm shale core plug SEM Evidence of Porosity in Kerogen

4 Mercury Injection Porosimeter incremental pore volume (ml/g) Steady-state permeability measurements shown on the Double-slip Chart 5 nm 10 nm 20 nm nm pore throat diameter (mm) nm 100 nm 1/P (1/psi)

5 MC Simulation of Fluid Adsorption VMD visualization of methane-ethane mixture in slit-pore 4nm, 3,000 psi (20.7MPa) pore pressure and 176 o F (80 o C) temperature 40 Adsorbed fluid r*ch4, (1000*A-3) Free fluid pore half length, Å pore half length

6 Adsorption in SWCNT Structured density profile across the tube under thermodynamic equilibrium conditions: 6/19 2 nm 3 nm 5 nm

7 Density Profile in Organic Pores and Channels Under equilibrium conditions, discrete density profile has three regions: adsorbed layer methane in 4,000 psi and 175 F phasedistribution in nanopore 0.30 Density (g/ml) transition layers free fluid Distance from the wall (Å)

8 Shale Gas-in-place Calculations Old Methodology Void space measured by porosity measurement + Sorbed mass measured by adsorption experiment = Total GIP New Methodology Void space measured by porosity measurement + Sorbed mass measured by adsorption experiment - Free gas volume taken up by sorbed gas = Total GIP G f = φ(1 S B g ρ b w ) Mˆ G p sl ρ ads p + p L correction for adsorption layer effect

9 Phase Diagrams of Methane, Butane and Octane Bulk EOS Bulk GCMC Temperature, K nc 4 nc C Density, g/cc Phase diagrams of bulk methane, n-butane and n-octane obtained from Peng-Robinson equation of state and GCMC simulations in this work. The dots indicate critical points.

10 Phase Diagrams of Methane, Butane and Octane under Confinement Temperature, K Methane Bulk - EOS 8nm-GCMC 4nm-GCMC Butane 600 Density, g/cc Bulk - EOS 200 8nm - GCMC Density, g/cc Density, g/cc

11 Implications Uncertainty in Analysis? ternary (C 1, C 4, C 8 ) mixture T=210F Bulk Reservoir Pressure, psia nm 3nm Oil Gas Condensate 500 Wet Gas Reservoir Temperature, F 11

12 Fluid Transport in SWCNT - Driving force generated using piston-like arrangement, controlling source and sink volumes to emulate pressure gradient - Transport properties measured through the tube, e.g. velocity profile, to infer the effects of free and adsorbed phases on the overall transport

13 Fluid Density and Velocity Profiles: Average pressure: 1,687 psi p=50 psi High Pressures Density Hagen Poiseuille Velocity Velocity velocity (nm/ps) density (g/cm3) Distance from capillary center (nm)

14 Mass Flux Profile across Nanocapillary Mass Flux ((g/cm^3*nm/ps) Distance from capillary center (nm) 2 3 Adsorption phase transport contribute a large portion to the total mass flux

15 Field Application I: (Bundle of Capillaries Approach) Marcellus shale permeability correction for the organic capillaries kk = kk [ff rr ee RR mmee ] where f(r tube ) = organic pore size distribution (fraction) Pore size distribution using N 2 adsorption porosimetry A flow cutoff of 2 nm applied ff rr ee RR mmee = k a = k 57.3% enhancement in permeability

16 Field Application I: (Organic-rich Shale Permeability) kerogen adsorption +diffusion inorganic matrix viscous flow f r a c t u r e 10.0 k = k + µdc + µd gas m g s k = k p α p 1 conf m o 1 p G sl ρ grain B g 3 m ε ks p L (p + p ) 2 L Apparent permeability [nd] nn tt Molecular transport effects of organic nanopores Geomechanical effect of inorganic pores only ,500 4,500 6,500 8,500 10,500 Pore Pressure [psia] 16

17 Production Trends with Varying Fracture Conductivity Reservoir pressures [ psia ] 10, ,000 6,000 4,000 2,000 k f = 5 md k = 50 md f Distance from the well [ ft ] K gas [ nd ] k gas = 26 nd k gas = 13.5 nd 0 1,000 2,000 3,000 4,000 5,000 Pore Pressure [ psia ] Because of relatively high pressure near the fracture, molecular transport effects become less influential

18 Nano-group Researchers Ten researchers with In alphabetical order: Sara Abedi, Petroleum Eng Dept. Experimental and theoretical microporomechanics, nanochemomechanical characterization of geomaterials Yucel Akkutlu, Petroleum Eng Dept. Multi-component, multi-phase molecular effects in organic nanocapillaries and scaling up Perla Balbuena, Chemical Eng Dept. Nanopore confinement effects on hydrocarbon phase behavior Khoa Bui, Petroleum Engineering Dept. Multi-phase flow and capillarity in nanoporous materials Tahir Cagin, Chemical & Materials Eng Dept. Nano-scale mechanical investigations of water-shale interactions and rock failure mechanism

19 Nano-group Researchers, cont. Louise Criscenti, Sandia National Laboratories, New Mexico Molecular interaction of hydrocarbons with various kerogen types Yalchin Efendiev, Mathematics Dept. Upscaling microscopic phenomena, multi-scale simulations Andreas Holzenburg, Center for Imaging and Microscopy Nano-scale imaging for petrophysics John Killough, Petroleum Engineering Dept. Meso-scale simulations of fluid flow and transport in multi-scale porous media Yifang Wang, Sandia National Laboratories, New Mexico Geochemistry laboratory

20 Organic rich shales: from nano to macroscale Macro: Uniaxial creep -4/-3 Acoustic measurement Strengh Fracure toughness Micromechanical Upscaling -7/-6 log (m) Nano/Microchemomechanical testing Creep Elasticity -9 Stochastic upscaling Tests at elevated temperature Strength Fracture toughness

21 IFT of Methane in Nanopore From the local stress tensor, pressures are calculated considering both kinetic and internal (inter- and intra-molecular) contributions: p xx (z) + p yy (z) γ = 1 L Z [ p N (z) p T (z)]dz = 1 L Z ]dz N N [ p zz (z) z Value of IFT is 6.65 mn/m across the V-L interface. This value is 45% smaller than that of the bulk IFT

22 EOR for Shale Oil using Nano-emulsion oil in water emulsion Surfactant: dodecylhepta(oxy-ethylene)ether (C 12 E 7 ) contains one hydrophobic tail of 12 alkyl groups, and one hydrophilic head of 7 ethylene oxide groups and 1 terminal OH group Oil: d-limonene (terpene solvent) time=0 time=3 ns time=10 ns oil organic wall Y Y Y Y Y Y Y Y Y Y Y Y Y

23 TAMU Center for Imaging and Microscopy: Imaging Modalities across the Scales (continuum)

24 TAMU Center for Imaging and Microscopy: Imaging of Anything from Atoms to Ant Interfacial structure between SiC and nanoscale MgAl 2 O 4 particles. The layer spacing of 0.25 nm is well resolved for the SiC phase

25 TAMU Center for Imaging and Microscopy: and from Alzheimer s peptides to zeolite 24 hrs 144 hrs 288 hrs 250 nm 100 nm 250 nm Small, spherical aggregates Sheets rolling up Fibrils Tin-containing zeolite crystals

26 Capabilities for Nano-scale Ge ochemical Studies at Sandia National Laboratories A Synthesis of nanoporous material B s Isolation of kerogen from Mancos shale Density functional theory (DFT) modeling Field observations Core/outcrop sample collection Quantification of heterogeneities Molecular dynamic (MD) modeling Binding energies of methane sorption Diffusion rates Pioneering work in nanogeochemistry. Access to DOE Center of Integrated Nanotechnology Pore structure characterization using small angle neutron scattering C Material characterization Pore structures: SANS, BET, TEM, SEM, etc Chemistry & m ineralogy: XRD, XRF, etc Sorption/desorption measurements Methane sorption/desorption on m odel materials Methane sorption/desorption under high P & high T Chemical/physical stimulations Column experiments Diffusive fluxes Advective fluxes Gas disposition & release Gas in place (GIP) Gas m igration from matrix into fractures Stim ulated volume Gas for secondary recovery Nanoscience Effects of nanopore confinement on fluid thermodynamic properties Effects of nanopore confinement on methane transport (m icrofluidics in shale) Upscaling Percolation theory Fractal representation LatticeBoltzmann modeling Predictive models Constitutive relationships Continuum m odels Reactive transport modeling TRAMANTO: Classical Density Functional Theory High pressure/high temperature sorption/desorption measurements PFLOTRAN: Reactive transport modeling High pressure flow-through experiments

27 Water-clay interactions using large-scale simulations 50 x 50 x 80 nm 3 Kaolinite Clay under external stress Soak with brine Vary salinity, stress, temperature