R Single well injection withdrawal tests (SWIW) in fractured rock. Some aspects on interpretation

Transcription

1 Single ell injetion ithdraal tet (SWIW) in ratured rok Some aet on interretation Ivar Neretniek eartment o Chemial Engineering and Tehnology oyal Intitute o Tehnology Augut 007 Svenk Kärnbränlehantering AB Sedih Nulear Fuel and Wate Management Co Box 5864 SE Stokholm Seden Tel Fax

2 ISSN Tänd ett lager: SKB aort P, eller T. Single ell injetion ithdraal tet (SWIW) in ratured rok Some aet on interretation Ivar Neretniek eartment o Chemial Engineering and Tehnology oyal Intitute o Tehnology Augut 007 Thi reort onern a tudy hih a onduted or SKB. The onluion and vieoint reented in the reort are thoe o the author and do not neearily oinide ith thoe o the lient. ata in SKB databae an be hanged or dierent reaon. Minor hange in SKB databae ill not neearily reult in a revied reort. ata reviion may alo be reented a ulement, available at.kb.e. A d verion o thi doument an be donloaded rom.kb.e.

3 Summary Single-Well-Injetion-Withdraal, SWIW, tet are ued to try to extrat inormation on rature aerture, ortion and diuion roertie and dierion inormation in individual rature. It i done by injeting a given amount o traed ater into an iolated rature. Ater a aiting eriod ater i ithdran rom the rature and the traer onentration i meaured. The onentration time urve i itted to a model and the arameter value quantiying the dierent interation mehanim are determined. A number o dierent mehanim inluene the reovery o the traer. One or more o the olloing mehanim are onidered. They inlude: dierion due to veloity dierene, ortion on rature urae and on inill, diuion in rok ragment in the rature, diuion beteen treamline, diuion into rok matrix and other tagnant ater volume, ortion kineti and lo drit o the lume aued by the natural gradient. Many o the interation mehanim an inluene the reovery urve in a imilar ay. For examle, diuion into rok matrix ater and into tagnant ater in the rature adjaent to the loing hannel annot be ditinguihed i only one traer i ued. Traer ith dierent roertie an in rinile be ued but they ill enounter dierent art o the rature, the orbing traer ill move out le rom the injetion oint than a nonorbing traer ill. iuion and ortion in mall artile in the loath an inluene the reovery urve in a imilar ay a rok matrix diuion doe. ierion aued by diuion beteen treamline, Taylor dierion, an give very dierent reult in hannel o dierent hae. Suh dierion eet an be diiult to ditinguih rom matrix diuion eet. ierion oeiient obtained in a SWIW tet may have little relation to dierion o a traer moving rom A to B. Thi i artly due to the dierent mehanim and artly due to dierent time ale. The hort duration o a SWIW tet an not be exeted to have been inluened in the ame ay by the dierent mehanim that are ative over the long time ale o interet or aety analyi. Beaue many dierent mehanim inluene the reovery urve in a imilar ay any arameter value extrated rom SWIW tet mut be treated ith oniderable aution and aterthought. 3

4 Sammanattning Så kallade Single-Well-Injetion-Withdraal, SWIW, teter använd ör att öka exerimentellt betämma rikvidder amt ortion-, diuion- oh dieriondata ho enkilda rikor. I öröken injiera vatten med ett årämne i en rika. Eter en väntetid uma vattnet tillbaka oh halten årämne mät. Sårämnehalten ändring med återumad mängd vatten använd ör att betämma arametervärden i någon modell om bekriver hur årämnet åverka av olika mekanimer. Ett antal olika mekanimer åverkar årämnet uörande. En eller ler av öljande mekanimer brukar modellera: dierion örorakad av hatighetkillnader, ortion å rikyllnadmaterial oh rikytor, diuion in oh ur bergragment i rikan, diuion mellan trömlinjer, diuion in oh ut ur bergmatrien oh andra tagnanta vatten, ortionkinetik oh inverkan av naturligt löde i rikan under öröket. Många av dea mekanimer åverkar hur årämnehalten i återumat vatten varierar med tiden å ett narlikt ätt. et leder till att t ex diuion i bergmatrien oh i andra tagnanta vatten inte kan ärkilja om endat ett årämne använt. Sårämnen med olika diuionoh ortionegenkaer kan i rini använda ör att ärkilja mekanimerna men de kommer att ha varit i kontakt med olika delar av rikan; det orberande årämnet kommer att ha varit i kontakt med rikytan närmat injieringhålet medan det ike orberande kommer att ha nått längre ut. iuion oh ortion i må artiklar oh bergmatri kan åverka hur myket årämne om återå i tillbakaumat vatten å ett narlikt ätt, vilket gör det vårt att utkilja om det var artiklar eller bergmatri om åverkade reultatet. ierion örorakad av diuion mellan trömlinjer, k Taylordierion kan vara myket olika i kanaler med olika orm. enna ty av dierion kan okå ge uhov till narlika eekter om matridiuion. ierionkoeiienter utvärderade ur ett SWIW örök kan ha liten relation till vad om kulle erhålla vid tranort mellan unkt A oh B i amma rika under andra örhållanden. etta beror del å att olika mekanimer kan ha orakat dierionen, del å att tidkalorna kan vara myket olika. SWIW örök gör ota under relativt kort tid ör att undvika att årämnet ör iväg av det naturliga vattenlödet. et innebär att andra mekanimer kan åverka årämnet uörande än de mekanimer om kommer att ha tört inverkan ör tider av intree ör en äkerhetanaly ör radionuklidtranort. Eterom många olika mekanimer kan ha narlik inverkan å årämnena måte arametervärden om betämt med SWIW örök använda med ytterta öriktighet oh etertanke. 4

5 Content 1 Introdution Bakground 7 1. Bai rinile o a SWIW tet and ome ue 7 Aim, aroah and oe 9 3 Flo and tranort in ratured rok 11 4 Interation o olute ith rok Interation mehanim beteen rok and diolved ioni eie The K d onet and reverible ortion eation kineti eet iuion kineti eet iuion in rok matrix Penetration into mall artile in the loath Poible ale eet o matrix diuion Other diuion eet Paraboli veloity roile in a lit or laminar lo Veloity roile in a taered lit Taylor dierion 3 5 Flo attern in rature Flo attern Flo in a rature ith and ithout inill 7 5. Eet o heterogeneitie in the lo ath Hydrodynami dierion 9 6 Proee aeting a SWIW tet in a rature Injetion o a volume o ater in a rature Ideal ae Non-ideal ae eovery by bak uming rit o traed volume aued by natural lo 33 7 Model and imliied verion Cae a: aidly injet and immediately ithdra traed ater Cae b: Injet traer in rature and monitor onentration in the ater in the rature iuion into rok matrix only Comare eet o matrix and tagnant ater utake Cae : iuion rom hannel into tagnant ater and into matrix rom both hannel and tagnant ater 38 8 Some diiultie in interretation o SWIW tet Summary o ome idealied ae Some omliating ator Interretation o SWIW tet Stagnant ater diuion eet inluded in the idealized ingle rature model Poible ue o indeendent obervation to ontrain the interretation Ue o a hot ater intead o a olute a a traer 44 9 iuion and onluion Aknoledgement 49 eerene 51 Notation 57 Aendix Model or traer utake rom a lat hannel into matrix, into tagnant ater in rature and rom there into matrix 59 5

6 1 Introdution 1.1 Bakground The long term aety o a inal reoitory or nulear ate in dee lying rytalline rok may be inluened by the aability o the ratured rok to retard any otentially eaing nulide. One o the main retardation mehanim i the utake o the nulide into the orou rok matrix and the ortion on the internal urae in the matrix. It ha been ound that the diuion and ortion roertie o the rok a ell a the ontat urae beteen the loing ater and the rok, the o alled Flo Wetted Surae, FWS, are eential or aeing the retardation. It i o oniderable interet to be able to veriy that thee retardation mehanim are ative in the dee lying rok. Traer tet in itu are ued or thi uroe. The main thrut o thi reort ill be on diuing hat inormation atually an be extrated rom in itu traer tet and hat other mehanim ould oibly diturb the interretation. It i alo highly imortant to ditinguih mehanim that ill be ative over time ale o thouand to hundred o thouand o year rom thoe mehanim that may be ative in hort time tet but ill not have muh eet over longer time. The diuion in the olloing ill thereore oint to a number o mehanim and relate them to the time ale here they may be o imortane. Model o olute tranort in ratured rok are ued to imulate ontaminant tranort in the omlex three dimenional rature netork that ontitute the loath. Mot olute interat in variou ay ith the rature urae and ith the underlying rok. Laboratory meaurement are ommonly ued to tudy the dierent interation mehanim and roee. Hoever, it i neeary to veriy and validate the model by olute migration exeriment in real rature and netork o rature in their natural environment i.e. by in itu exeriment. Numerou exeriment have been erormed by dierent organiation. Very oten beteen hole tet are ued here traer are injeted in one borehole and their arrival monitored in another borehole. From the breakthrough urve inormation an be extrated on at leat ome o the olute-rok interation mehanim. Suh beteen-hole exeriment are very otly and diiult to erorm in dee lying rok rom urae borehole, hih need to be aurately oitioned. Pratially nothing i knon o the rature roertie along the loath here the tet ill be erormed. Some o the diiultie an be avoided by erorming ingle ell (borehole) exeriment here a traer olution i injeted into an iolated rature or in a netork o rature and later umed bak. The idea i that the traer reovery urve ould be ued to extrat inormation on at leat ome o the interation mehanim. Thi reort diue the lo and tranort mehanim and roee that inluene olute tranort in ratured rok ith an aim to ae hat inormation ould be extrated rom Single-Well-Injetion-Withdraal, SWIW, tet, and hat obtale and diiultie hould be onidered hen lanning, erorming and interreting uh tet. Belo i a hort derition o SWIW tet and hat inormation ha been attemted to extrat rom uh tet. Thereater ollo a hort ummary derition o lo and tranort in ratured rok ytem, o interation mehanim and o rok roertie related to the reent roblem. Thi ill give the bakground or the ret o the reort. 1. Bai rinile o a SWIW tet and ome ue In a SWIW tet erormed in a borehole a rature i iolated beteen to aker. A given volume o traed ater i raidly injeted into the rature. Ater a aiting eriod ater i umed bak and the traer onentration in the umed ater i reorded. Muh more ater 7

7 i umed bak than a injeted beaue the traer ha reated in variou ay ith the material and ater oket in the rature and i only loly releaed bak to the umed ater. The onentration time urve i analyed ith the aim to extrat inormation on the dierent mehanim that aued the reovery urve to be read out in time. Thi i tyially done by itting the reovery urve to a model by adjuting the arameter o the model to obtain a bet it in ome ene. For uh a itting to be meaningul the model mut aount or all imortant mehanim that inluene the reovery urve. It ill be ound that many interation mehanim have a imilar inluene on the reovery urve, hih imlie that indeendent obervation or aumtion are needed to earate the eet o the dierent mehanim. Variant o the tet an be oneived e.g. lo injetion, no or a hort aiting eriod and lo bak uming. In uh a tet traer interation mehanim aued by lo lo mut alo be onidered in addition to thoe ative in a tet here the aiting eriod eentially determine the interation. Then even more arameter mut be determined. SWIW tet are made in rature onneted to the loing netork and the natural lo in the rok mut be onidered to avoid unaetable lo o traer olution due to the natural lo in the rok. Commonly day to eek o aiting time i ued. SWIW tet have been ued or a variety o uroe. Some reent invetigation are mentioned here. Several invetigation uing SWIW tet ere aimed at obtaining in itu reation rate or mirobially mediated reation. /Haggerty et al. 1998/ ued a imliied method o uh-ull tet data analyi or determining in itu reation rate oeiient, /Snodgra and Kitanide 1998/ deribed a method to iner in itu reation rate rom uh-ull exeriment. /Burbery et al. 004/ ound that the model ued oten do not aount or ome relevant and imortant roee and they diued the limitation o SWIW or thee uroe. /Itok et al. 001/ ued uh-ull tet or in itu determination o uburae mirobial enzyme kineti. /Itok et al. 00/ ued artitioning traer in ingle-ell uh-ull or NAPL detetion in the uburae. /Kim et al. 004/ ued uh-ull tet or aeing in itu aerobi o-metabolim. /avi et al. 00/ invetigated the ue o radon and a non-interating traer to detet and quantiy reene o non-aqueou hae liquid, NAPL, ontamination in the uburae, utilizing the retardation eet on radon by the reene o the NAPL. SWIW tet have been erormed to tudy dierion o non-orbing and interation o orbing traer ith the rok rature auming ingle oroity ytem, /Snodgra and Kitanide 1998, Altman et al. 00, Ghergut et al. 005, Gutaon et al. 006, 005, Novakoki et al. 1998, 004, Shroth et al. 001, Waker and Berg 004, Caini et al. 005/. In many o the ited aer method o evaluating and arameterizing the lo and tranort roertie are diued. Literature revie on deign and interretation o SWIW tet are reorted in /Nordqvit and Gutaon 00, 004/. Tet have alo been erormed and interreted auming interation by diuion and ortion in a orou matrix o ratured rok /MKenna et al. 001, Haggerty et al. 000, 001/. /Meig and Beauheim 001/ diu variou roee and mehanim that make it diiult to unequivoally determine tranort arameter beaue they give rie to imilar behaviour o the reovery urve. 8

8 Aim, aroah and oe Thi reort et out to urvey the lo and tranort mehanim and roe that inluene olute tranort in ratured rok ith an aim to ae hat inormation ould be extrated rom Single-Well-Injetion-Withdraal, SWIW, tet and hat obtale and diiultie hould be onidered hen lanning, erorming and interreting uh tet. The mehanim deemed to be mot imortant are deribed and oing alulation are ued to exlore hen they an notieably inluene the olute rok interation. Simle onetual and mathematial model are ued to ae hih arameter and arameter grou ontained in the model ould otentially be determined by SWIW tet. It i alo attemted to ae hih mehanim and their arameter value are likely to be diiult to determine. Furthermore it i attemted to oint out inormation that an not be derived rom uh tet ithout reorting to variou aumtion, hih may be diiult to ubtantiate by indeendent meaurement or obervation. A eii aim i to ae hether SWIW tet erormed over a eriod o day, eek or month an give quantitative inormation on mehanim that ill be o imortane or imulating radionulide tranort over aety aement timeale or reoitorie or nulear ate, meaning time longer than thouand to ten thouand o year or even longer. Central data needed or long term redition inlude rok diuion and ortion roertie uh a matrix diuion oeiient and ortion ditribution oeiient a ell a the magnitude o the Flo Wetted Surae, FWS, over hih interation beteen olute in the ater and the rok take lae. Purely hydrodynami dierion eet are deemed to be o eondary imortane or the long term but are imortant to undertand hen evaluating tet. 9

9 3 Flo and tranort in ratured rok Some reent ell reerened aer on lo and olute tranort mehanim in ratured rok ummarize muh o hat i knon today and alo oint to area here there i more to learn /Bodin and Marily 003ab/. Another valuable oure i the aer by /Neuman 005/ here trend, roet and hallenge in quantiying lo and tranort through ratured rok are diued. Belo i a hort ummary o the roee and mehanim that are deemed to be o eial imortane or the aim and oe o thi reort. For the ubequent diuion a imliied onetualiation o the rature ytem in ratured rytalline rok i given belo. Muh more detailed derition o the internal o rature rature zone an be ound in e.g. /Mazurek et al. 003/. Frature in rytalline rok range in ize rom miro rature beteen and in the rytal that make u the rok matrix to major rature zone that an extend or everal km. Frature ith ize u to ten o meter or even u to 100 m an be made u o individual rature or an ehelon o individual rature. Thee are oten alled bakground rature. They an be oriented eemingly randomly in ome rok or in everal dominating diretion in other rok. Thee rature are ometime maed individually but are treated tohatially in rature netork model. The urae o the bakground rature are in ontat ith eah other in ome lae but an alo have oen art that are onneted and allo ater to lo through the rature. Mot o the loing ater i oten een to lo in a minor art o the rature lane. Thi i alled hannelling. Channelling i deemed to motly be due to the ater eeking out the eaiet ath under the hydrauli gradient that exit at any time. Hoever, hannelling i alo knon to exit in ath that have been generated by long time hemial eathering o a lo ath or by reiitation o eondary mineral loing o etion o the rature. Figure 3-1 and 3- ho ome hannel oberved on the all in tunnel. Water ith diolved errou iron emerge rom ome art o rature and the iron i oxidied, mediated by miro-organim, hen it ome in ontat ith air in the tunnel. Thi leave urtain o the iron reiitate mixed ith miro organim. Frature interetion have been oberved to orm onduit or ater. Flo in rature interetion ha alo been oberved in large ale lo exeriment in Stria underground laboratory /Abelin et al. 1991/. Channelling ha been oberved in many exeriment and obervation in ratured rytalline rok /Abelin et al. 1983, 1991, 1994, Neretniek 1988, Birgeron et al. 1993/. /Moreno and Neretniek 1989/ diued the imat o hannelling in rature zone on the tranort o radionulide. /Moreno et al. 1990/ diued ome anomalou eature ariing rom rature aerture variability. /amuon and Neretniek 1986/ hoed that narro hannel an trongly inluene the retardation eet due to matrix diuion. /Grenier et al. 1998/ made numerial imulation o the inluene o heterogeneitie on the tranort o non-orbing olute. /Tang and Neretniek 1998/ revieed obervation on hannelling in heterogeneou ratured rok. They ound that thi i a ommon henomenon and may trongly inluene traer migration. /Neretniek 00a/ analyed ome traer exeriment uing a hannelling model inding that utake into tagnant ater in the rature lane may have a notieable eet on interretation o traer exeriment. Larger rature or rature zone are oten made u o a number o maller rature aligned in eentially a -dimenional eature ith a thikne that an vary rom a e m to many meter or ten o meter. The zone ontain large and mall rok ragment, hemially altered rok and lay ormed rom eathered rok. The hydrauli ondutivity ithin the rature zone an vary oniderably alo ermitting reerential lo ath to develo. 11

10 Figure 3-1. Channelling een in the Bolmen tunnel a reiitate o iron oxide. Figure 3-. Channelling in the Poço de Calda uranium mine een a reiitate o iron oxide in the rok matrix into hih oxygen ha diued and reated ith yrite. White line have been dran around the oxidized red rok. The grey rok ha not been invaded by oxidizing ater. Figure 3-3 ho a tylied examle o loath and hannel in a blok o rok ontaining bakground rature a ell a a rature zone. Thi reort ill mainly diu lo and tranort roertie in bakground rature and minor rature zone ith tranmiivitie tyially le than 10 6 m /. It i the lo and olute tranort roertie o the hydraulially onneted rature and the hannel in thi netork that ill be tudied in thi reort. 1

11 Figure 3-3. Flo take lae in bakground rature a ell a a rature zone. Channelling i indiated by the red ot. Water that lo in the netork o hannel ill have a reidene time ditribution governed by the volume o the ondutive netork and the lo rate o the ater. The dierene in lorate in dierent loath ill give rie to a eidene Time itribution, T, o the ater. Solute arried by the ater ill have a T that i alo inluened by dierent mehanim inluding thoe aued by interation ith the rok urae. Some olute interation roee ith the rok an dramatially inluene the T o the olute. Thi i diued in the next etion. 13

12 4 Interation o olute ith rok Solute arried by the ater may interat ith the all o the rature by hyial and by hemial mehanim. The rok matrix i orou and ha a onneted oroity extending at leat ten o entimetre, oibly extending throughout the hole rok. The rok nearet the rature urae i ometime altered and an have a higher oroity and dierent hemial roertie /Maurek 003/. Many rature have inill and oating o eondary mineral hih an have a dierent oroity and dierent hemial roertie than the bulk rok. There ill be le or ratially no lo in the oating, eondary mineralization or the rok matrix omared to the lo in the rature. Hoever, olute ill ae the ore by moleular diuion. The enetration deth ill be mall or hort ontat time and larger or long. Some orbing olute ill reveribly attah to the outer a ell a inner urae and be retarded in their migration. A orbing eie an have dierent ortion roertie on the dierent mineral. There ill thu be everal mehanim that inluene the T o traer. ierent traer ill be inluened in dierent ay. The orbing traer ill be retarded omared to the ater veloity and during a given time a nonorbing traer ill move a longer ditane than a orbing and the to traer ill thereore ontat dierent art o the rature. 4.1 Interation mehanim beteen rok and diolved ioni eie The main hemial interation mehanim onidered or long term migration o radionulide in ratured rok i adortion and ion-exhange. Thi take lae on the mineral urae o the rok. Preiitation in variou orm ould ontribute in addition. Hoever, thi i rarely aounted or and ill not be diued urther. The hort etion that ollo give the bakground to hy linear reverible ortion i ommonly ued in the model. The main mineral o the rok matrix o graniti rok are alumino-iliate, iron and other oxide and ome alteration rodut uh a lay. Table 4-1 ho examle o ome ommon mineral ound in graniti rok Table 4-1. Examle o ome ommon mineral ound in graniti rok. ok orming mineral Alumino-iliate (very lo olubilitie) Quarz SiO K-Feldar KAlSi 3 O 4 Biotite KMgFe AlSi 3 O 10 (OH) Plagiolae Na 0.6 Ca 0.38 Al 1.38 Si.6 O 8 Seondary (reative) mineral Carbonate CaCO 3 (Seondary mineral in rature) Sulhide mineral FeS Iron oxide Fe 3 O 4, Fe(OOH) Clay (motly in rature ormed by eathering) Kaolinite Al Si O 5 (OH) 4 Montmorillonite Al Si 4 O 10 (OH) Gibbite Al(OH) 3 15

13 Some o thee mineral have a ermanent negative harge due to iomorhi ubtitution, hih attrat oitive ion in the ater. Suh harged mineral ill have a aaity or at-ion exhange. In addition ome oxide urae an be rotonated and de-rotonated deending on the loal H. Thi imlie that the urae S = OH grou an beome oitively or negatively harged a S = OH + or S = O grou and attrat ooitely harged ion. The S = OH grou alo an bind ation by hat i alled urae omlexation to orm or examle an ameriium omlex S = OAm + ith Am 3+ ion in ater. In addition reiitation and o-reiitation an our hen the onentration o a eie ome near it olubility. The ortion ainity o a eii ationi traer (radionulide) an be very dierent on the dierent mineral. The ortion o a eii ation ill alo deend on the reene and onentration o other ion, hih omete or the ortion ite. The ortion take lae on the urae in and on the mineral grain. Thereore the magnitude o the aeible urae o the mineral in the rature ill inluene the ortion aaity o a given area or volume o a rature. Later the matter o aeible urae ithin orou artile and intat rok matrix ill be diued in the ontext o time deendene o olute interation. The above erve to illutrate that the ortion on a rature urae and any inill in the rature ill be trongly inluened by the mineral reent in the rature and on the aeibility o orbing urae. Provided that the rature mineral in and on the rature urae i reaonably ontant in a loath ome average ortion aaity and ainity an be deined The K d onet and reverible ortion Ion exhange and urae omlexation are uually raid roee one the ion have ome near to the urae o the mineral grain. The roee are alo reverible, hih mean that the ion an detah rom the urae and enter the ater a ree ion again. Attahment and detahment i ontantly ourring. Equilibrium may be attained hen the to rate are equal. The ratio o the onentration o the eie on the olid to that in the ater i alled ditribution oeiient and i denoted K d. Oten it i given in unit a hon in Equation (1) K d ma _ o _ ion g _ olid = = (1) ma _ o _ ion l _ ater When the onentration in the ater i very lo i.e. trae onentration, K d i not muh inluened by the onentration and i oten taken to be ontant. Thi i uually deemed to be an aetable aroximation or mot nulide. It i inherently aumed that all the ite on the urae o a ma o the mineral are aeible and have been aeed in the exeriment ued to determine the ditribution oeiient. Suh exeriment are ommonly made on ruhed rok and ith ontat time ranging rom hour to month, ometime more. The aumtion o linear reverible equilibrium and K d onet i very ueul beaue the mathematial treatment o the model() i muh imler than hen nonlinear eet and reation kineti mut be aounted or. In thi reort e aume that the K d onet i aliable. /Craord et al. 006/ have reently diued K d meaurement and omiled data or rytalline rok eation kineti eet Even though the loal ortion-deortion on a ortion ite may be quik and reverible there ometime may be hange o the urae due to e.g. lo eathering. It ha been noted in laboratory exeriment that equilibration ith ruhed rok an be a lo roe taking eek to month or more. I uh eet are ueted in an in itu exeriment thi ill inluene the reovery urve o a SWIW tet and may not be eay to ditinguih rom other eet /Haggerty et al. 1998/. 16

14 4. iuion kineti eet 4..1 iuion in rok matrix /Neretniek 1980/ uggeted that matrix diuion ould have a dominating imat on radionulide tranort in ratured rok, eeially or time ale o interet or aety analyi or nulear ate reoitorie. It ha been ound to be the mot imortant retardation mehanim or nulide migrating in ratured rok ormation /Moreno et al. 1993, 1997, Zuber and Motyka 1994, Smith et al. 001, eimu et al. 003, etrok 005/. For that reaon thi reort lay muh emhai on matrix diuion and ho it an be oberved and quantiied in SWIW tet. Oberved lo kineti and dierion in traer tet in ratured rok are oten due to lo diuion in larger artile here the traer ha to ae the interior ite o lager artile and intat rok itel. Thi i one o the mot imortant kineti eet. The rok matrix, altered rok, eondary mineral oating on rature urae and inill artile are more or le orou but the lo reitane in the miroore netork i o large that lo i negligible. A olute that ome in ontat ith rok and rok ragment ill move by moleular diuion into the onneted ore netork o the material to reah the inner ortion ite. The inner ortion ite have vatly larger urae than that o the loing rature. The longer ditane the olute ha to migrate the longer it ill take to equilibrate the interior o the artile. In large artile the olute may not have time to enetrate the entire amle or rok matrix during the time o a tet. uring the bak uming tage in a SWIW tet the reovery o the traer mut be exeted to be only artial. Thi, in theory, ould be ued to ae the diuion roertie o the loath. Sorbing traer ill be retarded a they diue into the material beaue they have to uly the ortion ite underay and equilibrate thee beore the traer an move deeer into the amle. The enetration deth a it evolve ith time an be illutrated by the imle exreion in Equation (4). I a rok rature oniting o only the rok matrix i exoed to a olute and the onentration at the urae i ket ontant the traer loly diue into the rok. Conentration roile in a rok matrix ith ontant roertie an be determined by olving the intationary diuion equation, Fik eond la. The olution or unidiretional diuion uh a into the rok rom the urae i given by Equation (), or a material exoed to a ontant onentration at the urae rom time zero /Bird et al. 00, 61/. o = Er ( x t ) () i the ore diuion oeiient, hih i maller than that in unonined ater beaue o tortuoity and ontritivity eet. It an be meaured or aroximately etimated rom the oroity o the material. The rok matrix diuivity an alo be etimated rom eletrial ondutivity meaurement erormed in itu in borehole even don to large deth /Lögren and Neretniek 003/. i the retardation ator or the olute aued by the reverible ortion deribed earlier, Equation (3). ρ i the denity o the rok material and ε i it oroity. Thee entitie are meaured in the laboratory K ρ ( 1 ε ) d = 1 + (3) ε The leading edge o the traer here the onentration i arbitrarily et to 1% o that at the urae, ater time t i at a loation η The rate o movement lo don ith time. The ditane i roortional to the quare root o time /Bird et al. 00, 61/. 17

15 η 0.01 = 4 t (4) Figure 4-1 illutrate enetration deth into a orou, omehat altered, rok uh a an be ound at the rature urae. = m / and oroity ε = 1%, ortion oeiient K d ρ = 0, 0.1 and 1, (etardation ator 1, 11 and 101). The let igure ho the enetration deth or time tyial or a SWIW tet and the right hand igure or the lo end o tyial or SA time. It i een that in a SWIW exeriment the traer ould ae u to a e ten o mm at mot herea or Saety analyi, SA, time the roertie o the rok on the order o metre or more ould inluene the traer migration. A traer tet erormed over a hort time may thu not give reult that are rereentative or muh longer time i there i reaon to believe that the roertie o the rok near the rature urae dier rom that urther in. Another oint to onider i that i there i inill oniting o artile in the loath thee may add oniderably to the ortion during the tet but ill ontribute little during SA time hen they have aturated early on already. Thi a one o the main onluion alo o /Haggerty et al. 001/. Another ay to exlore ho ar rom the rature urae a traer enetrate and ho thi i inluened by an inreaed oroity near the rature urae i reented belo or illutrative uroe 4.. Penetration into mall artile in the loath Similarly one an etimate the time or a olute to enetrate and equilibrate ith a orou artile in the rature. Partile ize an vary rom extremely mall lay artile u to rather large blok in rature zone. In the tye o rature onidered in thi reort or SWIW tet the rature aerture are deemed to be maller than a e entimetre or the more tranmiive rature and don to le than 0.1 mm or the le tranmiive rature, The larger rature are tyially illed ith rok ragment, mall artile and lay herea the maller rature onit o to more or le loely itting urae. Partile ize and the oroity o the inill ill inluene the tranmiivity o a rature ith inill. A lo oroity and mall artile ize ill exert a high reitane to lo and ill have a lo loal tranmiivity. Water ill tend to lo in region ith le uh inill. The ore ae o orou inill ith lo tranmiivity ill at imilarly to a orou rok or oating here olute ill diue in the nearly tagnant ater in the inill more raidly than they are tranorted by lo. There may thu be region ith ratially tagnant ater in the rature lane beteen loing ath into hih region olute ill gain ae by diuion. The inill may alo orb the orbing traer. η0.01 mm time day η0.01 m time year Figure 4-1. Penetration deth into a orou matrix a a untion o time or retardation ator 1, 11 and 101, urve rom to don. 18

16 When the enetration deth η 0.01 aroahe the hal dimenion o the artile Equation (4) i no longer valid. Then even the mid art o the artile beome equilibrated. Then another illutrative entity an be ueul. One an etimate the time it take or the oreater in a artile o a given ize to beome nearly equilibrated ith the ater outide rom diuion theory. We all thi the harateriti time or equilibration t. For a herial artile the average onentration ha reahed 9% (arbitrarily hoen to get a imle ontant in the equation) o the equilibrium onentration at a time /Carla and Jaeger 1959, 10/. t = 0.05 d (5) For a lab, d thik, the ontant 0.05 i 0. intead. Figure 4- ho the harateriti time t or = m / and = 1, 11 and 101 a a untion o artile diameter. It i een that artile maller than one mm in diameter ill be equilibrated ater le than a day or the value ued or diuivity and retardation ator. Thi imlie that mall artile an aommodate notieable amount o a orbing traer i exoed to it. Furthermore, very mall artile ill be quikly equilibrated and delete the injeted ater raidly i there i muh inill o mall artile in the art o the rature injeted ith the traed ater. Larger artile alo an take u the traer but ill not be equilibrated during a day or o. They ill, hoever, be in a tranient tate o utake imilar to the rok matrix or thik oating. 4.3 Poible ale eet o matrix diuion eently everal aer have been ublihed regarding interretation o traer tet by model inluding the eet o matrix diuion here thi eemingly ha been ound to inreae ith traer travel ditane. /Beker and Shairo 000/ ould obtain imilar it baed on model ith advetion only ithout aounting or diuion eet. /Shairo 001/ onluded rom kilometre ale obervation that matrix diuivitie mut be order o magnitude larger than that in ree ater to it a tranort model that inluded matrix diuion eet and onluded that thi mut be aued by major lo heterogeneitie and not by matrix diuion. /Liu et al. 007/ ummarize a large number o aer that diu thee eet. In their aer they alo invetigated a number o otential mehanim that ould aue uh inreae. By imulation they ho that hydrauli heterogeneitie in the orm o loal loath an give rie to the eeming inreae in diuion ith ale. They alo ugget that there may be urther mehanim, a yet not exlored, that alo ould aue uh eet. Thee obervation ugget that olute interation eet imilar to thoe aued by diuion into matrix ore ater an be aued by other mehanim, hih may lead to diiultie to unequivoally determine diuion arameter rom traer tet. t day artile diam mm Figure 4-. Charateriti time or aturation o artile a a untion o artile diameter or = 1, 11 and 101, urve rom bottom and u. 19

17 4.4 Other diuion eet Stagnant or nearly tagnant ater i alo ound in region ith inill in the rature and rature zone and in region adjaent to the loing hannel. Solute in the loing ater ill diue in and out o uh region. The eet on traer tranort ith the loing ater ill be very imilar to thoe aued by matrix diuion and annot readily be ditinguihed rom the olute onentration time urve. Hoever, the ue o traer ith dierent diuion and ortion roertie an be ued to earate uh eet. Thi i alo oible or other diuion eet diued belo, at leat in rinile. In thi etion e onider the eet moleular diuion ha on reading the olute beteen and aro treamline in a rature. Firt, or illutrative uroe, a ae i onidered here there i no diuion aro treamline. Thereater the eet o moleular diuion are onidered and it i hon that thi an inreae the reading o a ule in ome irumtane and to narro the ule in other Paraboli veloity roile in a lit or laminar lo Water that lo in a lit move ater in the middle than near the all here it ha zero veloity. The veloity roile i araboli /Bird et al. 00, 63/. Equation (6) ho the veloity ditribution in a hannel. v i the mean veloity and b i the hal aerture o the rature. z in thi ae i the ditane rom the middle o the lit. v( z) = v 3 z ( 1 ( ) b ) (6) Thi i hon in Figure 4-3 belo. The veloity in the entre o the hannel i 1.5 larger than the mean veloity. Thi ha imliation on ho a traer olution read out hen it i injeted into a rature dilaing the ater ithout traer. The ater in the entre o the rature ill arry the traer a given ditane 50% ater than the average lo. The irt arrival ill ome earlier than the mean o the traer te inut. The traer onentration ill gradually inreae and the traer onentration ill build u and aroah that o the injeted traed ater. The breakthrough urve or uh a ae i hon in Figure 4-4 or a traer injetion onentration equal to 1. The time ale i normalized to time or irt arrival. Figure 4-5 ho the onentration roile along the loath. The ti o the veloity roile ha travelled a normalized ditane equal to 1. The traer i read out over the hole ditane generating a oniderable dierion. Thi tye o dierion ould inluene the injeted traer olution a ell a the reovery urve. Thi henomenon ould be exeted to our or hort injetion or ithdraal time and in rature ith large aerture hen diuion beteen treamline ha not had time to even Figure 4-3. Veloity roile or laminar lo in a lit. 0

18 Conentration Time Figure 4-4. Breakthrough urve at a given ditane a a untion o time. Conentration itane Figure 4-5. Conentration averaged over the aerture a a untion o relative ditane rom entry. out the onentration aro the rature. Long time or mall aerture ill allo diuion to even out the onentration aro the aerture. The harateriti time or thi an be etimated rom Equation (7) a deribed earlier or artile 1 t = 0. d (7) Figure 4-6 ho the harateriti time or a hannel and a olute ith diuivity in ater o 10 9 m / a a untion o the aerture. Figure 4-6 ugget that or large aerture a hort injetion time may not allo the traer to equilibrate over the aerture and may lead to a traer ditribution along the injetion loath ith oniderable dierion a hon in Figure 4-4 above. In narro rature the traer read over the aerture and the ront beteen the dilaed ater and the traed ater beome narroer. Thi i alled Taylor dierion and i treated belo Veloity roile in a taered lit In a loath in a rature ith variable aerture there may be a veloity ditribution in the lane o the rature in addition to that aro the rature aerture a treated above. Channel in variable aerture rature ill mot robably have thi kind o veloity ditribution. We exlore an idealied ae belo. Figure 4-7 ho an idealized taered lit ith a maximum aerture o b max and idth W. 1

19 t hour aerture mm Figure 4-6. Charateriti time to equilibrate the traer aro a rature aerture by moleular diuion. b max b(y) y W Figure 4-7. Taered lit ormed hannel. Water lo in the lit erendiular to the igure. The mean veloity v (y) at every loation y i ratially roortional to b(y). We neglet the inluene o the gradient in the y diretion due to the taering. The lorate in a vertial lie i roortional to b(y) 3 imilarly to that diued reviouly or the veloity ditribution over the aerture. I W>>b e an neglet the taering o o the ro etional area or diuion and treat the ae a or the veloity ditribution aro the hannel. The harateriti time or diuion i then aroximated by Equation (7) but ith d exhanged or W. t = W (8) For a ae ith W = 0.05 m t = 3 day. Thu or hort injetion time the araboli veloity roile in the y diretion ill not be evened out by diuion. Thi ill alo be hon under Taylor dierion diued belo. It may be mentioned here already that i an injeted non interating traer ule ere to be immediately umed bak the ule that i read out in the injetion te ould again unread beaue the traer in the adjaent treamline ill not have had muh time to diue

20 beteen them. Hoever, during the aiting eriod in a SWIW tet, o ay ten day in thi examle, diuion beteen the treamline ould beome notieable. Furthermore, a ill be diued later the interation o a traer by diuion in the orou rok matrix i very trongly inluened by the rature aerture a a loally narro aerture allo muh larger deletion o the ater in the rature by utake into the matrix Taylor dierion Moleular diuion ill even out the onentration roile aro the loath /Bird et al. 00, Logan 1999/. Thi eet may oniderably dereae the read o the traer ule in the lo diretion. Thi ill be illutrated by onidering the reading o a narro ule travelling ith the tream. The read o a hort (ira) ule due to moleular diuion in the lo diretion an be obtained rom Equation (9). Thi ould aly or a lat veloity roile. The ule i travelling ith the veloity v in the x diretion. = M π t e (x vt) 4 t (9) Thi i illutrated in Figure 4-8 or = 10 9 m / ater t = 1 hour and veloity 1 m/hour and M = 1 (arbitrary unit). It i een that or thi ae the dierion due to moleular diuion i very mall hen lug lo (lat veloity roile) i aumed. The ule ha read to about one m in the lo diretion due to diuion. Thi i, hoever muh larger than the rature aerture e onider. The veloity roile ill ontantly try to read the ule but the diuion aro the aerture ill ounterat thi. The ombined eet on dierion are alled Taylor dierion. It ha been quantiied by olving the lo and diuion equation, reulting in Equation (10). It ha been onirmed by exeriment /Bird et al. 00/. L 1 b v = ( 1+ ) 5.5 (10) It hould be noted that the notion o Taylor dierion i valid or the ae hen the traed olution i olleted and mixed at the outlet o the rature. I there ha not been time to even out the onentration beteen the treamline the dierion ould not be een i the luid a raidly ulled bak a in a SWIW tet. Comare the diuion around Figure 4-4 and 4-5. Conentration itane m Figure 4-8. Sread o a ira ule in the diretion o lo due to moleular diuion only. Veloity v = 1 m/hour, = 10 9 m /. Obervation ater 1 hour. 3

21 L an be ued intead o in Equation (9), or a Pelet number Pe x > 10, at leat or illutration uroe. Pe = x vx L (11) Note hoever, that thi i not tritly orret beaue the orm o the ule by ure diuion and Taylor dierion i dierent. It i een that or very lo veloitie or aerture b the irt term ill dominate and the longitudinal dierion oeiient aroahe the moleular diuion oeiient. For large aerture or veloitie the eond term ill dominate. Thi i hon in Figure 4-9 here L / W i 133 or the narro urve and 1,470 or the broad urve. A more raid injetion ill inreae the dierion due to Taylor eet (Figure 4-10). Alo, i there i a taered rature diued reviouly, the dierion that ould be oberved i the ater a olleted and mixed at ome oint dontream ould exhibit a oniderable dierion. Equation (10) ith b = W = 0.1 m and a veloity o 1 m/hour give L = Thi i ell outide the validity o the ormula, Equation (9), a it ould imly that the ule ha read muh ider than the length o the travel ditane (1 m) in the examle onidered. Should the ame volume be injeted over 5 day intead o 1 hour in the taered rature, ueeded by an immediate ithdraal there ould be a muh larger eet o diuion aro the treamline. A very aroximate but illutrative aement o the reulting dierion Conentration itane m Figure 4-9. Sread o a ira ule in the diretion o lo due to Taylor dierion. Veloity v = 1 m/hour, t = 1 hour, = 10 9 m /. High urve or aerture 0.3 mm, lo urve or aerture 1 mm. Obervation ater 1 hour. Conentration itane m Figure Sread o a ira ule in the diretion o lo due to Taylor dierion. Veloity v = 3 m/hour, t = 0.33 hour, = 10 9 m /. High urve or aerture 0.3 mm, lo urve or aerture 1 mm. Obervation ater 0.33 hour. 4

22 oeiient i L = m / or 1,000 time larger than the diuion oeiient in ater. The Pelet number, Pe x =.3 in thi ae. A Pe x beteen 1 and 100 i ommonly ound in traer tet arried out beteen to ell. It i mentioned here beaue it ugget that one reaon o ule reading in ield exeriment ould be aued by the above eet and an be very muh inluened by the ay a traer tet i deigned. The dierion oeiient i not only a roerty o the hannel or hannel netork but i very muh inluened by the ay the tet i erormed. It i een that the Taylor dierion an aue oniderable ule reading and mut be onidered hen deigning and evaluating SWIW tet. I extraolation o reult rom hort term traer tet are to be made the underlying mehanim mut be ell undertood and quantiied. Taylor dierion mut alo be onidered hen the ater i umed u rom a dee borehole, here the tet ha been erormed. to the ground urae or analyi. A ide tube and at but till laminar lo an aue a oniderable dierion hih an be diiult to ditinguih rom that aued by the tet itel. 5

23 5 Flo attern in rature 5.1 Flo attern The ater lorate varie oniderably beteen dierent art o a rature. Preerential lo ath develo in the rature and oten mot o the lo take lae in a mall ration o the rature. Thi i alled hannelling. In ratie the atual lo ath geometrie annot be a riory determined. The Flo Wetted Surae, FWS, i.e. the urae that a ater akage ill ontat i not knon. Furthermore it i yet not oible to meaure the aerture o the loath by non-detrutive mean Flo in a rature ith and ithout inill In thi etion e exlore hat ize rature aerture an be exeted in a SWIW exeriment and hat inill artile an do to rature tranmiivity. It ill be hon later that thi inormation i ruial or interretation o SWIW tet. The larger rature are tyially illed ith rok ragment, mall artile and lay. Partile ize and the oroity o the inill ill inluene the tranmiivity o a rature ith inill. A lo oroity and a mall artile ize ill exert a high reitane to lo and reult in a lo loal tranmiivity. Water ill tend to lo in region ith le uh inill. The ore ae o orou inill ith lo tranmiivity ill at imilarly to a orou rok or oating here olute ill diue in the nearly tagnant ater in the inill more raidly than they are tranorted by lo. One an etimate the reure dro in a rature ith inill by the Blake-Kozeny equation /Bird et al. 00, 190/. The tranmiivity o an inilled rature ith aerture b i: T 3 b ε d ρg = 150 ( 1 ε ) µ (1) Figure 5-1 ho the tranmiivity o a 1 mm lit illed ith mall artile ith diameter d m or dierent oroitie. The horizontal line ho the tranmiivity o an oen lit aording the ubi la. An oen 0.1 mm lit ill have 3 order o magnitude loer tranmiivity, i.e. jut belo 10 6 m / and the lit aerture ill have to be a mall a 0.01 mm or the tranmiivity to be 10 9 m /. The tranmiivity o the lit ith inill on the other hand dereae in roortion to the aerture. log (Tranmiivity m /) log (d m) Figure 5-1. Inilled rature tranmiivity a a untion o artile ize and oroity o the inill. Curve rom bottom and u are or oroitie o 1%, 10%, 50%, 90% and 99%. The aerture b = 1 mm. The horizontal line ho the tranmiivity o an emty rature aording to the ubi la. 7

24 The ubi la i hon in Equation (13). T 1 = 1 ρg µ (b) 3 (13) It ha been uggeted that the hydrauli tranmiivity o the rature here the SWIW tet i made to be ued to ae the rature aerture by uing the ubi la. /Guimera and Carrera 000/ analyed data rom 90 traer exeriment and ound ome uort or the ue o the ubi la. Hoever, the regreion had a large variation and they onluded that it annot be ued or redition. /Saada et al. 001/ ued traer and hydrauli data rom ratured rok in granodiorite in the Kamaihi mine to orrelate aerture to tranmiivity. They ound an emiri equation ith a quare root relation and ith a read o about one order o magnitude. b = ont T (14) All data all ithin a range here the ontant i beteen 1 and 10 hen T i in m / and b i in mm. Tranmiivity ranged rom 10 8 to m / and the aerture b beteen 0. and 3 mm. Both relation are lotted in Figure 5- uing a ontant 3.15 or the emiri relation. Figure 5- ho the aerture o a rature a a untion o the tranmiivity aording the ubi la or ater at around room temerature and the emirial relation. The ubi la under redit the oberved aerture by more than one order o magnitude in the range o interet or thi reort. eveloment are underay to better undertand the relation beteen hydrauli and tranort aerture. eently e.g. /Konzuk and Kueer 004/ uing very detailed meaurement, nearly a million oint, o the aerture variation over a rature urae obtained enouraging agreement hen uing geometri mean aerture and inororating urae roughne ator. Hoever, the unertaintie in aerture ill be the aue o the larget unertaintie in evaluation o the matrix interation arameter. 5. Eet o heterogeneitie in the lo ath /Beker and Shairo 000, Wörman and vertor 001, Xu and Wörman 003, Lee et al. 003/ and /Go et al. 005/ tudied the imat o variou heterogeneitie on traer tranort in ratured rok. /Keller et al. 1999/ in a high reolution imaging o a rature modelled lo Log (aerture mm) Log (T m /) Figure 5-. Aerture o a rature a a untion o the tranmiivity aording to the ubi la (loer urve) and the data rom the Kamaihi mine (uer urve). 8

25 and tranort and omared the reult ith exeriment, onirming the trong imat o heterogeneitie on the tranort roertie and that thee an be modelled, rovided detailed inormation i at hand. In loath in ratured zone the blok ize ditribution and hannelling eet due to heterogeneitie in the hydrauli ondutivity an be exeted to have a trong inluene on the interation ith the traer. /amuon 1985/ tudied the imat on nulide tranort o the reene o artile/blok o dierent ize and hae in the loath. /Haggerty and Gorelik 1995, Haggerty et al. 000, 001, Fleming and Haggerty 001, MKenna and Meig 001/ ued the ame onet they all multirate model to ae the imat o matrix diuion eet. The multirate onet imlie in eene that dierent artile ize are aumed to exit in the loath and that they need dierent time to be equilibrated. The multirate onetualization a alo ound to be ound in an analyi o ublihed traer exeriment /Haggerty et al. 004/. /Gerke and van Genuhten 1996/ tudied the imat o dierent artile and ore hae and ugget a method by hih omlex and mixed tye o truture an be modelled. Quantitative inormation i never available or the atual loath in in itu exeriment and the inluene o the heterogeneitie on the interretation o traer tet mut be aeed by other mean. 5.3 Hydrodynami dierion The term hydrodynami dierion i ommonly reerred to hen diuing reading o a traer ule a it rogree through a orou and/or ratured medium. A dierion oeiient L ha long been ued in advetion-dierion model to arameterie it. In model it enter in the ame ay a moleular diuion doe. Hoever the underlying mehanim are quite dierent. Some o the reaon or ule reading have been diued above. Taylor dierion ontribute a ell a diuion in and out o tagnant ater along the loath. The latter may inlude the rok matrix, artile in the loath, tagnant ater in the rature lane et. An additional eet ome into lay hen traer tet are erormed by olleting traed ater in a ell. It i ometime alled veloity dierion. It i aued by the traed ater having moved to the uming ell by dierent ath ith dierent reidene time /Matheron and Marily 1980, Neretniek 1981, 1983, 00a, Chenut 1994/. Veloity dierion an have a trong imat on the breakthrough urve in multi-ell and onverging uming traer tet. Hoever, in SWIW tet here the traed ater ill be umed bak along the ame loath ued in the injetion hae that eet i not reent. ierion in SWIW tet i then exeted to be maller than in in-beteen hole tet in the ame rok. Thi ould otentially allo a better identiiation o the other roee. The lumed eet o all the underlying aue are ummaried in the dierion oeiient or hen divided by the average veloity, α = L /v, a dierion length α i obtained to haraterie the dierive roertie o the medium. It mut be reognied that thi ratie, although ommonly ued, mut be ued ith utmot aution. It an only be alied to the atual loath under the ame lorate ondition, hih render it ue or reditive uroe to be very limited a it i a lumed arameter. It inlude the eet o everal indeendent mehanim, hih all ale dierently ith travel ditane, ater veloity, reidene time and even deend on the traer ued. One examle o the diiultie uing thi lumed arameter onet i that the aarent L and α are ound to inreae ith obervation ditane /Gelhar et al. 199/ and thu are not to be een a a roerty o the medium. In the model, hoever, it i ued a uh and given a ontant value hen olving the equation. It i deirable to earate the dierent eet auing ule reading and to model them earately i the reult are to be ued or reditive uroe. 9