Downloaded by guest on September 24, 2021 n ecietasotpoessi ope abnts(22). carbonates (21), complex oil in of processes desaturation transport reactive capillary and the during pres- dynamics capillary ganglion CO (15), condition jumps reservoir during Haines changes sure including imaged, been processes pore-scale have dynamic, unsteady-state, Many s. 60 under in (19). trap- behavior residual wetting of and observations (18) ping instance, technological scan- for observed This allowed, laboratory-based 15–17). has be 9, both advance (8, in now beamlines synchrotron conditions can and reservoir ners phenomena at pore-scale rocks in that mean CT) nat- of far space pore thus the studies rocks. in ural no behavior flow are this were there investigated have they However, that established, change. were to stud- pathways observed differ- flow micromodel not for once in Again, quantified patterns (14). been Flow ies also 4–7). have wettabilities (2, hydro- ent stable during CO remains as established, or such settings, recovery natural carbon in displacements most model in flow flow 10–13). steady-state this 7, (1–3, during and spaces understood, observed pore well been 9). is has (8, motion behavior ganglia ganglion flow disconnected of and of space onset advection pore The the the the through of scale, out occur pore pushed can the be at can dominate phase to nonwetting begin forces viscous indentations that whereas and such pores pores, (4–7). small solid large the the of surface the occupies the in phase occupies wetting non- one generally The the by other. the occupied phase by channels occupied wetting number of of the number decreases saturation and the the fluid increases Increasing pathways. phase the stable one that separate show net- own of rates their work through flow flow low fluids nonwetting-phase at and flow wetting- micromodels two-phase and of Observations beadpacks (1–3). in space pore the of fraction T connectivity dynamic the state steady of energy interfaces. the new create of to some converted consis- sporadically where is is balance, fluids behavior injected energy This an lights. traffic with recon- by tent periodically controlled that cars pathways like necessarily not nect, along is occurs phase nonwetting Flow the connected. net- with the filled instant, capillary pores any of At low work saturation. fluid and constant conditions, at and N reservoir numbers, of subsurface flow at the sandstone image imag- We X-ray pore-scale ing. fast using connectivity,” which behavior, “dynamic term flow we steady-state sepa- of a into type demonstrate organize unobserved we Here previously phases interfaces. fluid stable with the pathways that flow Darcy 2017) rate is 18, multiphase media February porous steady-state review for in of (received flow picture 2017 21, conceptual June current approved and The MA, Cambridge, University, Harvard Weitz, A. David and by Kingdom; Edited United 2AZ, SW7 London London, College Imperial Centre, Research a www.pnas.org/cgi/doi/10.1073/pnas.1702834114 Reynolds A. sandstone Catriona a in flow multiphase steady-state during connectivity fluid Dynamic eateto at cec n niern,Ipra olg odn odnS72Z ntdKingdom; United 2AZ, SW7 London London, College Imperial Engineering, and Science Earth of Department atsnhorntmgah losteaqiiino images of acquisition the allows tomography synchrotron Fast (X-ray tomography computed X-ray micro in Developments of typical flow, steady-state slow during observation key The modified is forces viscous and capillary of balance the When oe hr ahpaeocpe t w ttc connected static, own its occupies phase conceptual each a where on based model is permeability relative of definition he | oesaeimaging pore-scale | elgcCO geologic a,b,1 2 anhMenke Hannah , trg,i htteptwy once pathway, the that is storage, | 2 2 micbetopaeflow two-phase immiscible storage n rn hog permeable a through brine and 2 biedang (20), drainage -brine a,b ate Andrew Matthew , | 7 10), are (7, that connections flow. blocking critical phase, have wetting the- with pathways traditional filled the these periodically in demon- that as We paths, but manner. flow ory, fixed stepwise follows a flow in that rate strate flow shown total the (apparatus increasing sandstone Bentheimer of in sample a space into pore N flow the injected in We sandstone. motion, a ganglion of pore-scale for below threshold well the conditions, flow subsurface capillary of low representative at numbers behavior rate- flow investigate two-phase to reservoir steady-state CT dependent, X-ray at investi- synchrotron performed fast experimental use flow We pore-scale conditions. steady-state a macroscopic is of here gation presented work The Scale Pore the at Flow Two-Phase Steady-State of Observations Experimental wet- pore the the through displacement ganglia of trapped nonwetting-phase (21). of recession space quan- that movement not and implied the were by was advance occurred flow it for local and implications the tified, the However, sand- of phase. in result ting quantified CO a been observed was of has ganglia as of reconnection ganglia trapping (23). and connection disconnected been The rock the stones. carbonate in has flow numbers, complex (21) ganglia a capillary oil high of trapped lower At space large pore At identified. the of in be fragmentation observed to the mechanisms rates, pore-scale new 1073/pnas.1702834114/-/DCSupplemental at online information supporting contains article This option. access open 1 PNAS the through online available Freely Submission. Direct PNAS a is article This interest. of wrote conflict no S.K. declare and authors M.J.B., The M.A., H.M., C.A.R., and data; paper. the analyzed H.M. and C.A.R. research; uhrcnrbtos ...dsge eerh ... .. n ..performed M.A. and H.M., C.A.R., research; designed C.A.R. contributions: Author c owo orsodnesol eadesd mi:catriona.reynolds11@imperial. Email: addressed. be should correspondence whom To ac.uk. atnJ Blunt J. Martin , uha elgcCO flow processes geologic two-phase flow as of subsurface such describing models to our fundamental modify are to that sug- need observation we contin- This that that pores. gests connections filled between of rearrange network nonwetting uously a the through of occurs flow phase that demonstrate “dynamic term We we unidenti- that connectivity.” previously behavior flow a steady-state of of type observations throughfied present flow water we and Here oil rock. including settings, media many permeable in through occurs fluids immiscible of movement The Significance edfiewtig n owtigpaecplaynumbers capillary nonwetting-phase and wetting- define We allowed also have technology imaging in advances These .W lee h ailr–icu oc aac by balance force capillary–viscous the altered We S1). 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EARTH, ATMOSPHERIC, AND PLANETARY SCIENCES Table 1. List of experiments 2C, and disconnected ganglia of N2 of various sizes were present Flow Rate,* Scan Mean in all of the experiments (Fig. 1). Experiment mL·min−1 Ca Ca time, min S The ganglia populations were subdivided to make visualizing w nw N2 the connectivity easier (Table S1): large ganglia, which typically 1A 0.02 7.00 × 10−7 2.27 × 10−8 44 0.274 contain thousands of pores and may be connected across the field 1B 0.10 3.50 × 10−6 1.13 × 10−7 35 0.225 of view (pink volumes, Fig. 1, containing more than 107 voxels); 1C 0.30 1.05 × 10−5 3.40 × 10−7 45 0.302 medium ganglia, which may be connected over tens to hundreds 1D 0.50 1.75 × 10−5 5.67 × 10−7 42 0.321 of pores (blue volumes, Fig. 1, containing 105 to 107 voxels); and 2A 0.04 1.40 × 10−6 4.54 × 10−8 29 0.358 small ganglia, which may be isolated in a single pore or be simply 2B 0.30 1.05 × 10−5 3.40 × 10−7 28 0.340 connected over a few pores (green volumes, Fig. 1, containing 2C 1.00 3.50 × 10−5 1.13 × 10−6 28 0.354 5 × 103 to 1 × 105 voxels; ganglia smaller than 5,000 voxels are ignored). *Total flow rate, Q = Q + Q , where Q = Q . t nw w nw w The total saturation throughout each experimental stage re- mained approximately constant, at a value close to the residual nonwetting phase saturation during imbibition, as measured on and larger core samples (24). However, the amount contributed by vnw µnw Canw = , [2] the different ganglia populations changed with both time and σ flow rate (Figs. 2 and 3). All of the experiments contained respectively, where the interstitial fluid velocity (in meters per medium and small ganglia, whereas the large ganglia are present second) is v = q/φ, q is the Darcy flux, φ is the porosity, µ is only at low flow rates (experiments 1A, 1B, and 2A). As the flow the dynamic viscosity (in Pascal seconds), and σ is the interfacial rate rises, the proportion of small and medium ganglia increases, tension between the wetting and nonwetting phases (in Newtons and the proportion of large ganglia decreases. per meter). Large ganglia that are connected across the field of view are Coinjection experiments were performed in two sets of only observed for the lowest flow rate experiments (1A and 2A). increasing total flow rate corresponding to an increasing cap- However, the connected pathway is not stable and varies in both illary number (experiments 1A to 1D and 2A to 2C, Table volume and position over time. Changes in connected pathway 1), each time starting with the pore space fully saturated with volume do not correspond to a change in total N2 saturation, brine. Brine and N2 were injected at equal flow rates until an but are the result of splitting the original connected ganglion approximately constant saturation was established in the core, into two separate large ganglia, or multiple medium ganglia (Fig. and then images were acquired over a period of 28 min to 4). Parts of the connected pathway repeatedly disconnect and 45 min. reconnect, changing the position of the connected pathway in the The images were processed using the techniques outlined in pore space. Materials and Methods, using Avizo 9.1 (www.vsg3d.com) to cre- The pathway stability can be described in terms of the num- ate 3D volumes of N2 that could be analyzed to assess their vol- ber of disconnection events that take place between each time ume and connectivity (Figs. S2 and S3). The steady-state satura- step. A decrease in volume of the connected pathway requires a

tion of N2 (Mean SN2 ) and the calculated capillary numbers for section to become disconnected, whereas an increase requires a the wetting and nonwetting phases are given in Table 1. connection with a neighboring ganglion to be made. Increasing Connected volumes of N2 were observed in the low flow rate, the flow rate, or capillary number, results in more disconnection low capillary number experiments (1A and 2A). There were no and reconnection events, and the pathway has an increasingly connected pathways of N2 in experiments 1B to 1D and 2B and dynamic connectivity.

Fig. 1. Ganglia populations contributing to average saturation. Average saturation is plotted versus time, and volume renderings of ganglia at the end of the experiment are shown, for experiments 1A to 1D and 2A to 2C. Ganglia are subdivided by size: large (pink), medium (blue), and small (green). Flow is from top to bottom. Time from the beginning of the experiment is normalized by the total experimental time (Table 1).

8188 | www.pnas.org/cgi/doi/10.1073/pnas.1702834114 Reynolds et al. Downloaded by guest on September 24, 2021 Downloaded by guest on September 24, 2021 enlse al. N et Reynolds of rendering volume show Images 2A. experiment for N plotted bottom. of are to volume time connected with The volume 8). connected in change relative 4. Fig. due be could ganglia of number the in change the inter- means of Rearrangement faces flow. must to space phase imaged pore nonwetting the the the for in of change ganglia volume a between pore interfaces of total the fluid Thus, the acquisition core. than of the greater volume during is The space image single time. pore over the through constant medium, transported stay small, of ganglia proportions large the rates, and (exper- flow high 1D) or and 1A) 1C (experiment iments low very At 2). ganglia (Fig. the populations between interaction the through pathways, connected N (pink) large 1D. and to (blue), 1A experiments medium (green), small of saturation 2. Fig. hsdnmccnetvt loocr neprmnswithout experiments in occurs also connectivity dynamic This neato ewe agi ouain.Posso h relative the show Plots populations. ganglia between Interaction oueo N of Volume 2 ntnaeul once rmiltt ult ngah,cnetdvlm fN of volume connected graphs, In outlet. to inlet from connected instantaneously 2 agi pi ysz:sal(re) eim(le,adlre(ik agi.Fo sfo top from is Flow ganglia. (pink) large and (blue), medium (green), small size: by split Ganglia (Insets) red. in shown is 2 agi for ganglia onciiyi h oetras hra h oebde remain bodies pore the throughout. whereas filled dynamic throats, of pore result the changing in the that observe connectivity is We connectivity populations 5. ganglia Fig. the between in sequence interaction of time ganglia illus- subvolume is the some of connectivity in in trated with positions change This static, ganglia. the neighboring between be Instead, to identified. appear be cannot space another. S1–S9 to pore one from migration fluid for in cre- pathway to seen a briefly behavior open ate connections connectivity which dynamic in pathways, same connected the the pore to the due through wholesale or ganglia space individual of transport the to in numbers the to corresponding 2. shown, Fig. on are red 1B experiment from ganglia 3. Fig. ntetm euneiae hw nFg sealso (see 3 Fig. in shown images sequence time the In ,idvda agi oigporsieytruhtepore the through progressively moving ganglia individual ), neato ewe agi ouain.Vlm edrnsof renderings Volume populations. ganglia between Interaction PNAS 2 | sapreto oa N total of percent a as uut1 2017 1, August 2 o xeiet2 nmes1to 1 (numbers 2A experiment for | o.114 vol. 2 auainadthe and saturation | o 31 no. Movies | 8189

EARTH, ATMOSPHERIC, AND PLANETARY SCIENCES Fig. 5. Change in connectivity with flow rate and time. Volume renderings of N2 ganglia, colored by size, in a 720 × 720 × 360 µm subvolume are shown for experiments 1A to 1D. Four consecutive time steps are shown for experiment 1C, illustrating two continuously filled pores and several transient branching connections. Also shown is the number of connections through pore throats in the whole imaged volume versus time. The volume of N2 shown in the images is connected both inside and outside the subvolume.

Dynamic Connectivity: A Single Flow Regime energy provided by the injection to alter the fluid configuration We estimate that the transition from experiments containing in only around 3% or the pores, or 160 elements in a scan vol- some intermittent connected pathways to experiments contain- ume encompassing ∼5,000 pores. Our observations show that ing no connected pathways occurs at critical wetting and crit- this leads to connected flow paths that are only sometimes sta- −6 ical nonwetting capillary numbers, Caw,crit = 4.5 × 10 and ble across successive scans. However, at the highest flow rates −8 Canw,crit = 8.5 × 10 (Fig. 6). These are two to three orders studied, a 50-fold increase in qt , or a 2,500-fold change in energy, of magnitude smaller than the transition identified in bead- allows rearrangement in all of the pores between scans, leading pack experiments (7); this is likely due to the difference in to a much more dynamic flow pattern. pore structure between beadpacks and the sandstone used in this study. However, the dynamic connectivity shown is different from that assumed in the traditional conceptual picture of two-phase flow. Instead of a transition from connected pathways to the advection of discrete ganglia, we see transport of the nonwetting phase through pathways that are largely fixed, with some connec- tions that periodically open and close. This novel flow behavior is separate from that reported by Datta et al. (7, 10), specifically, that the ganglia do not flow but instead rearrange their connec- tivity between filled pores. As capillary number increases, the fre- quency of connection and disconnection increases, and thus no connected pathway is ever observed. Fundamentally, steady-state fluid displacement is controlled by an energy balance (25). Work is done to inject fluids: The power per unit volume expended through fluid movement for either phase is approximately given by dW /dt = −qt·∇P ≈ 2 µqt /Keff , where Keff is the effective permeability in multiphase flow and qt is the total Darcy velocity (26). The surface energy of the interface between the wetting and nonwetting phases per unit volume is ∼σ/l, where l is a characteristic pore size. The time taken to provide sufficient energy to create the fluid inter- 2 faces is roughly t = σKeff /lµqt . As there is no net displacement in the experiments, fluctuations in the position of the interfaces eventually dissipate the surface energy as heat. For an order of −12 2 −4 magnitude estimate, we consider Keff = 10 m , l = 10 m, −5 −1 Fig. 6. The arrangement of N2 (as transient connected pathways or as and qt = 2.7 × 10 m·s , with the brine viscosity correspond- disconnected ganglia) is shown as a function of wetting and nonwetting ing to the lowest flow rate experiment in Table 1 (16). We find a phase capillary numbers for experiments 1A to 1D and 2A to 2C. We esti- 3 −6 timescale for interface creation of 1.4 × 10 s or around 20 min. mate that no connected pathways form above Caw,crit = 4.5 × 10 and −8 Thus, between two successive scans (43 s), there is sufficient Canw,crit = 8.5 × 10 .

8190 | www.pnas.org/cgi/doi/10.1073/pnas.1702834114 Reynolds et al. Downloaded by guest on September 24, 2021 Downloaded by guest on September 24, 2021 0 at S aarsnnT et A(04 oiiaino rpe non-wetting trapped a of Mobilization (2014) DA Weitz T, Ramakrishnan SS, Datta 10. 4 hoB aMn ,Jae 21)Wtaiiycnrlo utpaeflwi pat- in flow multiphase on control Wettability (2016) R Juanes C, MacMinn B, Zhao 14. of characterization resonance magnetic Nuclear (2011) JD Seymour SL, Codd EM, Rassi 13. two- simultaneous in state steady of independence History (2013) porous al. et in M, Erpelding flow two-phase 12. simultaneous Steady-state, (2009) al. et KT, Tallakstad 11. eevi odtosadhv dnie yeo o behav- flow at of type behavior a flow identified have steady-state and two-phase conditions N investigate reservoir using to floods microcore brine coinjection performed have We Conclusions pore- the same here. presented the in experiments are observed scale observations behavior these reconnection both and that contin- disconnection break likely of is observed intervals It the by flow.” - punctuated uous size irregularly, up occurs in break process pores up intermittently several pathway ganglia, 3D discrete “Intriguingly... into connected that this noted a (7) of al. In sections et conditions.” Datta steady observation, original 3D flow the recent configurations of temporary starting whereby reestablishment exact of the their elasticity with case almost an layer resume the to exhibited single tended “In channels a they that flow in noted Chaten- the flow and 2D. disturbances channel beads in observed glass flow (5) of two-phase Calhoun of and observations ever earliest the pore. each of occupies it that time of correc- fraction a the with the of for intermittently, by even tion governed start occupies, is and it phase that stop a volume of the entire conductance not The network, car. measure individual road we an entire permeability, the continuum- relative through make as flow we is such when overall Thus, measurements pathway. behavior scale N continuous the the a ganglia, of although separate that scale, in large arranged the pore-scale taneously by At modeled (3). accurately is simulations Primary rocks phases. fluid water-wet multiple in to drainage law Darcy’s very jus- of appears to extension used the process originally tify start flow pathway and continuous stop the short bal- this from different scale, a energy pore same for local the the On down junction the continues road. flow green—when a again—the turns movement blocking be favors light ance light, can network the network traffic road the When red a through time. a cars to of by comparable flow stopped is The lights. pathway traffic This arranged with are pathway. they a Although, ganglia, in dynamics. discrete ganglion observe we of instantaneously, type is unidentified described previously have we a disconnection and connection dynamic The Properties Continuum-Scale with Mechanisms Flow Pore-Scale Reconciling enlse al. et Reynolds .Ara G aaae C(95 lwrgmsadrltv emaiiisduring permeabilities relative and regimes Flow (1995) AC Payatakes DG, phase Avraam oil discontinuous 9. a remove to required two-phase forces static simultaneous and during Dynamic (1969) breakup JJ Taber Fluid (2014) 8. DA Weitz JB, Dupin SS, Datta 7. porous in (1958) behaviour AE fluid of Scheidegger examinations 6. Visual (1952) JC fluid one Calhoun of A, displacement Chatenever the of 5. Mechanisms (1983) A Sarr C, Zarcone R, Lenormand 4. (2017) MJ porous Blunt through 3. fluids heterogeneous of (1991) flow FAL Dullien The 2. (1936) MW Meres M, Muskat 1. hr aebe ugsin fdnmccnetvt nsome in connectivity dynamic of suggestions been have There udfo he-iesoa oosmedium. porous three-dimensional a from fluid media. porous in flow two-phase steady-state water. and oil both containing media porous from medium. porous three-dimensional a through flow Toronto). Press, Toronto I. Part - media ducts. capillary of network a in another by UK). Cambridge, Press, Univ bridge York). media. endmicrofluidics. terned infiltration steady-state during media saturated flow. partially of dynamics stationary the Phys ter media. porous two-dimensional through flow phase study. experimental 036308. An media: e Phys J New Physics 88:053004. e Technol Pet J 7:346–363. utpaeFo nPrebeMda oeSaePerspective Pore-Scale A Media: Permeable in Flow Multiphase 13:015007. oosMda li rnpr n oeStructure Pore and Transport Fluid Media: Porous rcNt cdSiUSA Sci Acad Natl Proc h hsc fFo hog oosMedia Porous Through Flow of Physics The 4:149–156. hsRvESa olnSf atrPhys Matter Soft Nonlin Stat E Rev Phys li Mech Fluid J 113:10251–10256. li Mech Fluid J hsFluid Phys o e n J Eng Pet Soc hsFluid Phys hsRvESa olnSf Mat- Soft Nonlin Stat E Rev Phys 135:337–353. 26:022002. 293:207–236. 26:062004. 9:3–12. Aaei,New (Academic, 2 Uiest of (University sinstan- is 2 (Cam- and 80: 4 enlsC,Keo 21)Caatrzn o eairfrgsijcin Relative injection: gas for behavior flow Characterizing (2015) S Krevor CA, 3D Reynolds fragmentation: Droplet 24. (2015) KS Sorbie MIJ, Dijke van S, Geiger IB, of Butler imaging T, Pak condition Reservoir 23. (2016) B Bijeljic MJ, Blunt MG, Andrew HP, Menke 22. multiphase R dynamic 21. of imaging The (2015) B Bijeljic MJ, Blunt angle H, contact Menke and M, curvature, layers, Andrew oil of 20. Imaging (2016) MJ Blunt B, car- Bijeljic supercritical K, trapped Singh of imaging 19. Pore-scale (2014) MJ Blunt B, Bijeljic M, Andrew 18. quan- for techniques analysis and imaging X-ray (2013) AP Sheppard D, Wildenschild modelling. and 17. imaging Pore-scale (2013) al. flow. et media porous MJ, in Blunt jumps Haines 16. of imaging 3D Real-time (2013) al. et S, Berg 15. 6 aiiA,ButM,Bjli 21)Drc iuain ftopaeflwo micro- on flow two-phase of simulations Direct (2014) B Bijeljic MJ, Blunt AQ, Raeini 26. flow multiphase of description discrete-domain A (2016) R Juanes L, Cueto-Felgueroso 25. eevi-odto oue fbieadN Equal and (7). brine observed of previously volumes been reservoir-condition has 10 transport ganglia observations, advective gas (N which of flows at during subsurface number to for applicable capillary those ratios from The ranged gas/oil (32). of CO 13:1 for typical ratio ically is viscosity here The used (31). injection 31:1 of ratio viscosity a uddb niern n hsclSine eerhCuclGrant Council Research Sciences Physical C.A.R. from Park. and acknowl- Technology funding Engineering gratefully 1304506. and and by Science We I13, Qatar funded beamline Singh. the was to and Kamal who access Shell, Dr. for Petroleum, College contribu- and Qatar Source the Light Imperial Bjeljic recognize Diamond Branko from we edge Dr. particular, team addi- In of the experimental experiments. tions thank the the also in We of participated assistance. members their for tional Garcia-Fernandez Mirian Dr. ACKNOWLEDGMENTS. calculated mL, provided 0.0075 are methods of Detailed volume rock. brine-filled pore in and a dry and the of 0.19 images of from a porosity with a images during had 3D imaged sample The 3.6 was Synchrotron. of sample The Lightsource size The mm. Diamond voxel pressure. 4 the fluid of at the diameter flow over a fluid confining MPa with a with 2 each holder of and core transparent pressure cm X-ray in 4 contained of short was sample length four core total of composed a microcore with composite cores sandstone Bentheimer a into were viscosities fluid µ the conditions, these N Under and phase wetting mol·kg the 1.5 as with performed were floods Core Methods and Materials of flow. steady-state rearrangement a and in even movement phases pres- rapid in fluid These the drive changes advance. can by interfaces changes the initiated fluid sure of be as many to pressure in capillary likely local observed is intermittency be sufficient This to provide pores. connectivity used dynamic numbers for capillary power highest rate hundreds flow the to with that quadratically tens increases such pores means over input work the stable reorganization The only seconds. of This of are 3% observation. pathways to flow of up connected sufficient timescale in is interfaces the there fluid over used, reorganize numbers pore to capillary the power lowest in population the ganglia At of the space. with paths strongly flow interacting ble, Connected connectivity.” “dynamic N term we ior N 2 uprigInformation. Supporting 2 emaiiyo CO of in permeability flow multiphase during process pore-scale unidentified media. porous previously a of imaging conditions. flow and - structure tomography pore synchrotron initial fast of using Effect carbonates heterogeneous in transport reactive Lett Res conditions. reservoir at microtomography Media Porous X-ray Transp synchrotron-based using flow fluid rock. carbonate water-wet a and mixed-wet a in carbonates. and sandstones in dioxide bon systems. medium porous subsurface Resour in Water processes and structure pore-scale tifying 216. USA Sci Acad Natl Tiae fpru ei n pcln fpr-cl forces. pore-scale of upscaling and media 74:116–126. porous of images CT hysteresis. of origin the and Lett landscapes energy Rugged media: porous in 51:9464–9489. ce ,e l 21)Fo once aha o ognlo dynamics. ganglion to flow pathway connected From (2015) al. et M, ucker xs nydrn o ailr ubrflw u r o sta- not are but flow, number capillary low during only exist ¨ 20.8 = 43:1615–1622. 42:3888–3894. ,adteitrailtninws6 mN·m 64 was tension interfacial the and µPa·s, 51:217–246. rcNt cdSiUSA Sci Acad Natl Proc eeaqie vr 3st raeatm eis The series. time a create to s 43 every acquired were µm 110:3755–3759. 2 bieadN and -brine 110:1–24. PNAS h uhr cnweg r hitp a and Rau Christoph Dr. acknowledge authors The 2 stennetn hs t1 P n 50 and MPa 10 at phase nonwetting the as | uut1 2017 1, August 2 wtri eeoeeu rocks. heterogeneous in -water 112:1947–1952. n rehueGsControl Gas Greenhouse J Int 2 neto nsln qiesi typ- is aquifers saline in injection 2 eeijce tacntn rate constant a at injected were ae eorRes Resour Water −1 hmGeol Chem | oasu oie(I brine (KI) iodide potassium o.114 vol. µ c brine d ae Resour Water Adv < 10 428:15–26. 642.2 = −6 | −8 d ae Resour Water Adv −1 ae eorRes Resour Water ohg values high to ) 52:1716–1728. o 31 no. < 2–0.The (27–30). N epy Res Geophys and µPa·s 22:1–14. c < Geophys | 51:197– 10 8191 Proc Adv −5 ◦ C. ,

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8192 | www.pnas.org/cgi/doi/10.1073/pnas.1702834114 Reynolds et al. Downloaded by guest on September 24, 2021