Effects of Solid-State and Pore-Fluid Chemistry and Stress on Permeability Evolution Derek Elsworth (Penn State) and Josh Taron (USGS) Basic Observations of Permeability Evolution – EGS and SGRs Key Issues in EGS and SGRs Spectrum of Behaviors EGS to SGR Homogeneous Permeability Flow Modes Diagenesis Permeability Evolution Basin Evolution Stimulation and Production Scaling Relations in Rocks and Proppants Reinforcing Feedbacks Induced Seismicity Mineralogical Transformations – Seismic -vs- Aseismic First- and Second-Order Frictional Effects Key Issues g3.ems.psu.edu 1 derek.elsworth@psu.edu Basic Observations of Permeability Evolution Resource • Hydrothermal (US:104 EJ) • EGS (US:107 EJ; 100 GW in 50y) Challenges • Prospecting (characterization) • Accessing (drilling) • Creating reservoir • Sustaining reservoir • Environmental issues Observation • Stress-sensitive reservoirs • T H M C all influence via effective stress • Effective stresses influence • Permeability • Reactive surface area • Induced seismicity Understanding T H M C is key: • Size of relative effects of THMC(B) • Timing of effects • Migration within reservoir • Using them to engineer the reservoir g3.ems.psu.edu Permeability Reactive surface area Induced seismicity 2 derek.elsworth@psu.edu Key Questions in EGS and SGRs Needs • • • • • • H = M f DT f c f Fluid availability • Native or introduced • H20/CO2 working fluids? Fluid transmission • Permeability microD to mD? • Distributed permeability Thermal efficiency • Large heat transfer area • Small conduction length Long-lived • Maintain mD and HT-area • Chemistry Environment • Induced seismicity • Fugitive fluids Ubiquitous g3.ems.psu.edu [Ingebritsen and Manning, various, in Manga et al., 2012] 3 derek.elsworth@psu.edu Contrasts Between EGS & SGRs EGS (Order of Mag.) Property ESRs (Order of Mag) Fractured-non-porous General Porous-fractured Porosity, n0 -> nstim ~10-30%, ~same <<1%,<1% microD -> mD 106 Permeability, k0 -> kstim Kf/kmatrix 10-100m Heat transfer length, s >>100/1. >100/1 ? *Heatsolid/Heatfluid Chemistry >mD -> >mD 106 ->1 1m -> 1cm ~10/1-2/1, same ? V. Strong TM Perm. Feedbacks Less strong Moderate, late time TC Perm. Feedbacks Strong? * g3.ems.psu.edu Heat in solid V (1- n) r R cR DT (1- n) r R cR = = Heat in fluid V (n) rW cW DT n rW cW 4 derek.elsworth@psu.edu Thermal Drawdown EGS –vs- SGRs dT 12lDT H solid ~ Al R ~ dx s2 Q f rW cW DT v rW cW DT H fluid ~ ~ V s EGS : ESRs : T0 t0 Hs Hs ® 0 tn Ti g3.ems.psu.edu Water Temp (at outlet) Thermal Output: x Rock Temp (in reservoir) In-Reservoir Water Temperature Distributions: v s® ¥ Hs ® 0 H s 12l R 1 = H f rW cW v s v s®0 tn Hs ® ¥ Hs Hs ® ¥ Ti x s ® 0; PeDa ® 0; Suppress short circuit? T0 Ti T0 t0 s ® ¥; PeDa ® ¥; Promote short circuit? 1 2 5 tD = t v V rW cW s s3 r R cR derek.elsworth@psu.edu Thermal Recovery at Field Scale Parallel Flow Model Spherical Reservoir Model Dimensionless temperature [Gringarten and Witherspoon, Geothermics,1974] Spacing, s, is small g3.ems.psu.edu [Elsworth, JGR, 1989] Trock [Note: not linear in log-time] Spacing, s, is large Tinjection Dimensionless time [Elsworth, JVGR, 1990] 6 Dimensionless time derek.elsworth@psu.edu What Does This Mean? This makes the case that: Permeability needs to be large enough to allow Mdot_sufficient without: 1. Fracturing reservoir during production 2. Large pump costs Beyond that – issues of heterogeneity are imp: 1. No feedbacks (Rick) 2. Reinforcing feedbacks (Kate/Paul/Golder/ Gringarten) Diagenesis contributes to this: 1. Initial basin evolution [k0,n0] 2. Reservoir stimulation/development [k,n=f(t)] 3. Reinforcing feedbacks [k,n=f(x,t)] for THMC g3.ems.psu.edu 7 derek.elsworth@psu.edu Effects of Solid-State and Pore-Fluid Chemistry and Stress on Permeability Evolution Derek Elsworth (Penn State) and Josh Taron (USGS) Basic Observations of Permeability Evolution – EGS and SGRs Key Issues in EGS and SGRs Spectrum of Behaviors EGS to SGR Homogeneous Permeability Flow Modes Diagenesis Permeability Evolution Basin Evolution Stimulation and Production Scaling Relations in Rocks and Proppants Reinforcing Feedbacks Induced Seismicity Mineralogical Transformations – Seismic -vs- Aseismic First- and Second-Order Frictional Effects Key Issues g3.ems.psu.edu 8 derek.elsworth@psu.edu Controls on Reservoir Evolution Many processes of vital importance to EGS/SGR are defined by coupled THMC processes. Thermal sweep/fluid residence time Short circuiting Induced seismicity Prolonged sustainability of fluid transmission Fractures dominate the fluid transfer system Transmission characterized by: History of mineral deposition Chemo-mechanical creep at contacting asperities Mechanical compaction Shear dilation and the reactivation of relic fractures g3.ems.psu.edu 9 derek.elsworth@psu.edu Typical Response of Fractures (Dissolution) m [Polak et al., GRL, 2003] g3.ems.psu.edu 10 derek.elsworth@psu.edu Typical Response of Fractures (Precipitation) Experimental arrangement Precipitation Thermal gradient along fracture [Dobson et al., 2001] g3.ems.psu.edu 11 derek.elsworth@psu.edu Dissolution Processes Approaches to Determine dk or db s Db s grain grain dissolution dissolution Time Time precipitation precipitation diffusion diffusion grain grain s s s s Time Db Component Model •Interface Dissolution dM diss d diss g d c2 dt 4 3 Vm2 s eff k g d c2 4R T Em 1 T Tm sc 4Vm 2 2 dM diss 3 Vm s a s c k g d c dt 4R T •Interface Diffusion J Db Jm •Pore Precipitation dM diff dt dM prec dt dC J m 2 r Db dr r dc dC dx 2 Db Cint C pore dc ln 2a V pore A k C pore Ceq M [Yasuhara et al., JGR, 2003] Matching Compaction Data [Experimental data from Elias and Hajash, 1992] System Evolution at 35-70 MPa and 150°C Observation 70 MPa and 150°C [Experimental data from Elias and Hajash, 1992] [Yasuhara et al., JGR, 2003] Extension 35 MPa and 150°C Timescales of Evolution of Granular Systems at 35 MPa and 75-150°C 75°C [Yasuhara et al., JGR, 2003] 150° C Permeability Evolution in Granular Systems at 35 MPa and 75-300°C 75°C 150° C Capillary Model : nd 2 k 96 Pore Evolution: V p ( / 4)d d 0 2 Linked Permeability: k ~ [Yasuhara et al., JGR, 2003] nV p 24 d 0 300° C Fracture/Proppant Diagenesis g3.ems.psu.edu 18 derek.elsworth@psu.edu Do we understand the mechanisms? Various mechanisms – appear complex but include: • Dissolution/precipitation • Solid and aqueous chemical transformations • Fluid/chemical assisted strength loss of proppant and proppant collapse Observation Experiment 250F 275F 325F 350F 0.030 DL (inches) 0.025 0.020 Characterization 0.015 0.010 0.005 Analysis 0.000 2 4 6 8 10 12 Time (days) [Dae Sung Lee et al., 2009] 14 THMC/HPHT Continuum Models Spatial Permeability Evolution THMC-S – Linked codes Temporal Permeability Evolution g3.ems.psu.edu 20 Constraint on Fracture Apertures and Fluid Concentrations d Asperity contacts (a ) Local contact area, Alc b br bmax Exp[( Rc Rc 0 ) / a] (b ) bmax br g3.ems.psu.edu 21 (c ) Increasing fracture closure c Modeling Results - Novaculite K+~x300 [Yasuhara et al., JGR, 2004] g3.ems.psu.edu 22 Projected Response of Fracture Define projected behavior for varied temperatures ….and mean stress magnitudes g3.ems.psu.edu 23 [Yasuhara et al., JGR, 2004] Reactive - Hydrodynamic Controls Peclet No. (Pe) Pe q vb Advective flux 0 Dispersive flux Dm Dm Damkohler No. (Da) Da Reactive flux 2k L 2k L Advective flux q vb0 PeDa No. (Removes <q>) Pe.Da Pe < 1 Dispersion dominated – Perturbations damped Pe > 1 Advection dominated – Perturbations enhanced Da << 1 Reaction slow Undersaturated along fracture – Perturbations damped Da larger << 1 – Reaction faster Saturated along fracture – Perturbations enhanced 2k L Reactive flux Dispersive flux Dm [Sherwood No.] Reactive Hydrodynamics: Role of Damkohler Number (PeDa) High PeDa 15 cm x 10cm Voxel = 1 mm Aperture: Black (0)White(0.25mm) Low PeDa Time [Detwiler and Rajaram, WRR, 2007] Effects of Solid-State and Pore-Fluid Chemistry and Stress on Permeability Evolution Derek Elsworth (Penn State) and Josh Taron (USGS) Basic Observations of Permeability Evolution – EGS and SGRs Key Issues in EGS and SGRs Spectrum of Behaviors EGS to SGR Homogeneous Permeability Flow Modes Diagenesis Permeability Evolution Basin Evolution Stimulation and Production Scaling Relations in Rocks and Proppants Reinforcing Feedbacks Induced Seismicity Mineralogical Transformations – Seismic -vs- Aseismic First- and Second-Order Frictional Effects Key Issues g3.ems.psu.edu 26 derek.elsworth@psu.edu Triggered Seismicity – Key Questions THMC Model: Principal trigger - change in (effective) stress regime: Fluid pressure Thermal stress Chemical creep How do these processes contribute to: Rates and event size (frequencymagnitude) Spatial distribution Time history (migration) How can this information be used to: Evaluate seismicity Manage/manipulate seismicity Link seismicity to permeability evolution Reservoir Conditions: g3.ems.psu.edu 27 derek.elsworth@psu.edu Observations of Induced Seismicity (Basel) [Goertz-Allmann et al, 2011] g3.ems.psu.edu [Shapiro and Dinske, 2009] 28 derek.elsworth@psu.edu r-t Plot - Fluid and Thermal Fronts and Induced Seismicity Parameters utilized in simulation Q: Flow rate t: Time h: Thickness ϕ: Porosity b: Aperture r 2Qt , h k0 3 b 12 S k0 Permeability[m2] 10-17 Pp Pore Pressure[Mpa] 14.8 Pinj Fluid Pressure[Mpa] 17.8 Tres Reservoir Temperature[°c] 250 Tinj Fluid Temperature[°c] 70 S Fracture Spacing[m] 10 to 500 [Izadi and Elsworth, in review, 2013] g3.ems.psu.edu 29 derek.elsworth@psu.edu Fault Reactivation (and Control) Controls on Magnitude and Timing: kfault & kmedium [10-16 – 10-12 m2] Injection temperature dT [50C – 250C] Stress field obliquity [45-60 degrees] Fault Permeability & Magnitude Timing Injection well [Gan and Elsworth, in review, 2013] g3.ems.psu.edu 30 Seismic –vs- Aseismic Events 1 year Duration (s) [secs -> years] 1 month 1 day 1 hour 1 min 1s 0 4 Mw = 6 Seismic Moment (N.m) [Magnitude] g3.ems.psu.edu 31 Mw = 8 [Peng and Gomberg, Nature Geosc., 2010] derek.elsworth@psu.edu Approaches – Rate-State versus Brittle Behavior Low velocity µ0 a ln(v/v0) Brittle High velocity Low velocity Failure Criterion (Trigger) Coefficient of friction System Stiffness (Stored Energy) Rate-State -b ln(v/v0) (a-b)ln(v/v0) DC Displacement g3.ems.psu.edu 32 derek.elsworth@psu.edu Seismic –vs- Aseismic Events Friction Velocity Strengthening (stable slip) Velocity Weakening (unstable slip) Stability (a-b) [Ikari et al., Geology, 2011] g3.ems.psu.edu 33 derek.elsworth@psu.edu • • • • Remote earthquakes trigger dynamic changes in permeability Unusual record transits ~8y Sharp rise in permeability followed by slow “healing” to background Scales of observations: – – – Field scale Laboratory scale Missing intermediate scale with control [Elkhoury et al., Nature, 2006] Permeability Permeability Scale Effects in Hydrology – Space and Time Role of Wear Products Sample Holder Sample Shear-Permeability Evolution Dissolution Products [Faoro et al., JGR, 2009] g3.ems.psu.edu 35 derek.elsworth@psu.edu Key Questions in EGS and SGRs Needs • • H = M f DT f c f Fluid availability • Native or introduced – fluid/geochemical compatibility • H20/CO2 working fluids? – arid envts. Fluid transmission • Permeability microD to milliD? – high enough? • Distributed permeability • • • • • • • Characterizing location and magnitude Defining mechanisms of perm evolution (chem/mech/thermal) Well configurations for sweep efficiency and isolating short-circuits Thermal efficiency • Large heat transfer area – better for SGRs than EGS? • Small conduction length – better for SGRs than EGS? Long-lived • Maintain mD and HT-area – better understanding diagenetic effects? • Chemistry - complex Environment • Induced seismicity - Event size (max)/timing/processes (THMCB) • Fugitive fluids – Fluid loss on production and environment – seal integrity Ubiquitous g3.ems.psu.edu 36 derek.elsworth@psu.edu