Development of Nanoparticle-Stabilized Foams to Improve Performance of Water-less Hydraulic Fracturing

Transcription

1 Development of Nanoparticle-Stabilized Foams to Improve Performance of Water-less Hydraulic Fracturing Ali Qajar, Zheng Xue, Andrew Worthen, Chun Huh, Keith Johnston, Maša Prodanović Center for Petroleum and Geosystems Engineering, University of Texas at Austin Department of Chemical Engineering, University of Texas at Austin

2 Why Hydraulic Fracturing with Foam? Unconventional reservoirs - Shale oil and gas, tight gas, coalbed methane and oil sands - Vast (~ shale gas reservoirs as 7299 trillion ft 3 ) - Difficult/expensive to produce Natural gas is estimated to meet ~26% of total global energy demand by Water Consumption - Reinjection causes microseismic events (slip on existing faults) - Shortage of water in dry regions (e.g. Eagle Ford Shale on TX-Mexico border) - Water reduces permeability to gas/oil during production Advantages of Foams for Hydraulic Fracturing - Lower water consumption - High viscosity and excellent sand carrying properties - Low leak off rate - Less damage to water sensitive reservoirs 2

3 Reduce Water Consumption in Viscoelastic Fracturing Fluids with up to 0.98 Quality Foam Ultra-dry Foams to Reduce Water Consumption Foam quality Q =V gas /V total 3 3

4 Fracture Generation with Foam Injection Substituting water with foam Water Energized Fluids (Q <40%) High Quality Foam (Q>60%) NP-stabilized Dry Foam (Q>90%) Fracture Propagation Axis Fracture width 4

5 Objectives: Design High Internal Phase CO 2 -in-water Foams with a Viscoelastic Aqueous Phase Stabilize high viscosity (100 cp at 100 s -1 ) up to 0.98 C/W foams with long lifetime (>3 hrs) Approach 1: viscoelastic anionic wormlike micelles Approach 2: mixtures of cationic surfactant and anionic modified silica NPs Surfactant: lower C/W IFT and reduce capillary pressure for drainage Wormlike micelle or polymer: raise the viscosity of continuous phase and interfacial viscosity/elasticity raise the storage modulus G of aqueous phase (carry proppants) Nanoparticles: adsorb at C/W interface to increase foam stability (Ostwald ripening) 5

6 Apparatus for foam viscosity measurement Hagen Poiseuille equation 6

7 Entanglement of Wormlike Micelles Imparts Viscoelasticity p = v/a 0 l c v/l c area of surfactant tail a 0 area of head group V = dh f dt = h2 3μ e R f 2 P Reduce a o with KCl and catanionic micelles Very dry foams, high f give high P c Rapid lamellae drainage P c = g/ R f (1-f) 0.5 Tubes: 12-hydroxystearic acid and ethanolamine Catanionic micelles: 2:1 C 13 COO - : C 16 (CH 3 ) 3 NH 4+ Cl Jamming: slow drainage maintains thick lamellae Fameau et al., Ang. Chem. (11) 7

8 G', G (Pa) G" SLES Wormlike Micelles Exhibits Maxwell Viscoelasticity 3.6% SLES + 0.4% C10DMA (5:1 by mole) + 2% KCl at 25 o C, ph G' G" Angular Velocity (rad/s) G' Cryo-TEM CH 3 (CH 2 ) 11 (OCH 2 CH 2 ) ~3 OSO 3 - and C 10 NH + (CH 3 ) 2 Forms entangled wormlike micelles Maxwell behavior indicate single relaxation time (9 ms) for combined reptation and micelle scission/recomb. Air water surface viscosity incr. 100 fold with addition of C 10 DMA to form mixed charged monolayer 8

9 Foam Viscosity (cp) Wormlike Micelles Increase Foam Viscosity at ɸ C = % SLES + 0.4% C10DMA + 2% KCl 3.6% SLES + 2% KCl 3.6% SLES in DIW SLES CDMA 2% KCl ɸ C = 95% ɸ C = 98% ,75 0,85 0,95 Internal Phase Volume Fraction SLES DIW Finer bubble size with viscoelastic aq. phase including C 10 NH + (CH 3 ) 2 High bulk and air-water surf. visc. decreases drainage/coalescence/coarsening ɸ C = 0.98 SLES Foam Viscosity (cp) Sauter Mean Size (µm) C/W IFT (mn/m) Air-Water Surface Viscosity (10-6 Pa.s.m) DIW C 10 DMA + KCl Xue et al. Submitted 9

10 Wormlike Micelles Increase Foam Stability at ɸ C = 0.95 Dsm 3 (um 3 ) 1,2E+6 1,0E+6 8,0E+5 6,0E+5 4,0E+5 2,0E+5 0,0E+0 SLES + C10DMA 95% CO2 SLES 95% CO2 y = 5033x Spherical Ω 3 = dd sm 3 dt = 64γD diffsv m 9RT y = x Time (min) Long term stability is dominated by Ostwald Ripening (const. polydisp.) Ω 3 decreased by a factor of 6 upon formation of wormlike micelles Perhaps the lamellae stay thicker and this slows down coarsening F Wormlike 10

11 Formulation variables to control curvature of CO 2 -water interface stabilized with silica nanoparticles θ<90 C/W SiOH with low Si(CH 3 ) 2 Cl 2 [1] Similar to concept for HLB (Binks) Hydrophilic/CO 2 -philic balance (HCB) and θ tuned with surface modification High adsorption energy: stable colloids E r 2 g CW 1 cos 2 [1] Dickson, Binks, KPJ et al. (2004). Langmuir 20. θ >90 W/C Fluorosilanes [2] [2] Adkins, KPJ et al. (2007). Phys. Chem. Chem. Phys. 9(48). 11

12 NPs irreversibly adsorb at water-gas interface (with molar adsorption energy of ~ 100 kt) Jamming of NPs stabilizes gas bubbles Proppant Why are Nanoparticle (NP) Foams Stable? Silica NPs (~0.1-1 wt%) + Dry foam Viscous Foam Carries Sand -SiOH / Surfactant / Polymer Surface modified silica NPs fill the interface Pc Drainage stops when capillary pressure cuts disjoining pressure at negative slope 12

13 NP surf. synergy: catanionic viscous foams at 98% CO 2 LAPB above CMC reduces IFT Flocculated NPs incr. emulsion stability (similar to Binks, Rodrigues, Langmuir (07) Catanionic foams at atm P (Varade, Langevin, et al. Soft Matter (11) 1% modified silica NPs, LAPB in 2% KCl, 50 o C Xue et al. JCIS

14 Apparent viscosity of C/W foams in 2 % KCl brine at shear rates of 200 s -1, 3000 psi and 50 o C. C/W foams stabilized with mixtures of 0.88% HPAM, 0.08% LAPB, with and without 1% silica NP. 14

15 Fracture Generation with Foam Injection / Simulation Substituting water with foam Water Energized Fluids (Q <40%) High Quality Foam (Q>60%) NP-stabilized Dry Foam (Q>90%) Fracture Propagation Axis Fracture width 15

16 Evaluation of Fracture Fluid Efficiency Fracturing fluid consumption (Total fluid and water phase) to generate a unit volume of fracture for different fluids Qajar et al. Submitted 16

17 Fracture Propagation Model Equations Physics Equation Conservation of Momentum (Pressure) Conservation of Mass Foam Transport (Kam, 2003) Nanoparticle Transport Fracture Propagation (KGD) 17

18 Geometry & Model Parameters Discretization Model Parameters Parameter Value Formation thickness, h (ft) 100 Reservoir Porosity 0.1 Reservoir Permeability (md) k x, k y, k z 1 Fracture Porosity 0.3 Fracture Permeability (d) 200 NX, NY, NZ 15, 5, 20 DX, DY, DZ (ft) 20, 20, Reservoir Pressure (psi) 3500 Least principle stress (psi), Layers , 4050, 3900, 4050, 4300 Initial Water Saturation (Sw0) 0.2 Parameter Value Young s Modulus 1e6 Rock compressibility (psi -1 ) 6e-7 Water compressibility (psi -1 ) 6.9e-5 CO 2 compressibility (psi -1 ) 7.2e-4 Methane compressibility (psi -1 ) 1.1e-2 Poisson ratio, v 0.2 Biot s constant, α 0.7 Injection rate (bbl/min) 20 Injection time (min) 20 18

19 Fracture Geometry (width and half-length) Fracture Width Foam 70% Low Vis. Foam 90% Low Vis. Fracture Half-Length Foam 95% Low Vis inch 19

20 Water and Nanoparticle Leak-off from Fracture into the Reservoir Water saturation inside reservoir near fracture Water 1 Foam 70% High Vis. 0 Nanoparticle concentration inside reservoir near fracture Foam 70% High Vis. 1.5 wt% Foam 90% High Vis. 0 20

21 Fracture Cleanup / Water Saturation 1 day 2 days 7 days Water Vis Fracpad Foam 70% High Vis. 1 Foam 70% Low Vis. Foam 90% High Vis. Foam 90% Low Vis. 0 21

22 Gas Productivity from the Reservoir after 4000 Days of production Gas production rate Cumulative gas production 22

23 Conclusions : Foam Generation High continuous phase and surface viscosities produced as a result of opposite charge between surfactant and polymer CO 2 /brine IFT reduced from 20 mn/m to 5 mn/m at 50 o C, 3000 psia Low lamellae drainage rates and low coalescence Small bubble size leads to high viscosity of cp at quality, at 200 s -1 NPs increase the apparent viscosity and stability of foam Decreases bubble size by factor of 2 Increases foam stability against Ostwald Ripening NPs irreversibly adsorb to C/W interface, creating an elastic interface 23

24 Conclusions: Foam fracturing behavior simulation Larger foam viscosity generated wider fractures with smaller fracture half-length: less leak-off Fracture cleanup simulations show that fracturing fluid cleanup for foam based fracturing fluids could take the order of 10 days Compare viscous fracpad which could take up to 1000 days Model combines: Gas and water flow in matrix and fracture Fracture geometry generated using existing software Mechanistic accounting of foam generation and coalescence (population balance) 24

25 Future Work High Internal Phase Foam Generation at High Temperatures Proppant carrying properties of viscoelastic foams Foam Generation in Micromodels 25

26 Supervisors Dr. Maša Prodanović Dr. Keith Johnston Dr. Chun Huh Dr. Steven Bryant Graduate students Zheng Xue Andrew Worthen Chang Da Undergraduate student Armand Colas 26

27 Thank you Publications - Xue et al. Viscosity and stability of ultra-high internal phase CO2-in-water foams stabilized with surfactants and nanoparticles with or without polyelectrolytes. J. Colloid Interface Sci Xue et al. Ultra-Dry Carbon Dioxide-in-Water Foams with Viscoelastic Aqueous Phases. Submitted - Qajar et al. Modeling Fracture Propagation and Cleanup for Dry Nanoparticle- Stabilized-Foam Fracturing Fluids. Submitted 27

28 Apparent viscosity of C/W foams in 2 % KCl brine at shear rates of 200 s -1, 3000 psi and 50 o C. 28

29 Micrographs of C/W foams at 3000 psia, 2% KCl brine and room temperature. (e)-(g) 90% v/v C/W foams stabilized with mixtures of 0.08% LAPB, 1% NP, and 0, 0.1% and 0.88% HPAM. (h) 90% v/v C/W foam stabilized with mixtures of 0.08% LAPB and 0.88% HPAM. (i)-(j) 95% v/v C/W foams stabilized with mixtures of 0.88% HPAM, 0.08% LAPB, with and without 1% silica NP. 29

30 Fracture Geometry (width and half-length) 2 min 20 min Water 0.25 inch Viscous frac pad 0 CO 2 30

31 Fracture Geometry (width and half-length) 2 min 20 min Foam 70% High Vis inch Foam 90% High Vis. Foam 95% High Vis. 0 31

32 Fracture Geometry (width and half-length) 2 min 20 min Foam 70% Low Vis inch Foam 90% Low Vis. Foam 95% Low Vis. 0

33 Fracture Cleanup / Initial Fracture Geometry 0.25 inch 0 Fracture clean up simulation by assuming above initial fracture geometry for all cases Flow direction and shape of fracture per layer 33