4.4 lower groundwater zone 24g/appendix f... · mike beeslaar eskom majuba simulated h hydraulic co...

Mike BeesEskom Ma

4.4 A lower gsurface. the hydra

Table 2:Ground

zon

Shallow groundwazone

Intermedupper groundwazone

IntermedLower groundwazone

Gus coalgroundwazone

Lower groundwazone

slaar ajuba UCG

Lower Ggroundwater No informataulic conduc

: Hydraulic Pdwater ne

D

ater Throuarea

iate

ater

Throuarea.compthrou

iate

ater

Throuarea.compthrou

seam ater

Throuarea

ater Throuarea

Groundwatr zone is asstion regardin

ctivity will be

Parameters Distribution

ughout Majuba

ughout Majuba (May be

partmentalized gh dykes)

ughout Majuba (May be

partmentalized gh dykes)

ughout Majuba

ughout Majuba

ter zone umed to be

ng piezometrlow.

of GroundwDepth

0-70m below surface

70 - 120m below surface

180 – 270m below surface

280-284m below surface

284-unknown depth.

6/41

present beloric levels hyd

water ConceHydraulic P

(HydConduc

/TransmisK=1.7 x 10-

8.6 x 10-3 mtest done ducurrent stud

K=8.0 x 10-4

(Slug test dthe current

T=0.1 to 0.9pumping dothe current

K=1.0 X10-4

X10-5 m/day

No informatavailable

ow the Gus cdraulic proper

eptual ModeParameters raulic tivity (K) ssivity (T) 1 m/day –

m/day (Slug uring the dy)

4 m/day

done during study)

9 m2/d (test one during study)

4 m/d to 1.0 y

tion

oal seam at rties is availa

el

Highly weKaroo se

Permeabdepth

Groundwfollows th

High grougenerally

Watercouareas

Fractured

Permeabfracturing

Rechargezone

Fracturedbelow the

Discharg

Fracturedwithin the

Groundwmbgl dur2008

Rechargezone

Discharg

Fracturedbelow the

• Permfractu

• Rechzone

• DischRiver

11

depths belowable but it ca

Properties

eathered/fractuediments

bility generally d

water piezometrihe topography

und between wy constitutes rec

urses and sprin

d dolerite.

bility depends ong

e from overlying

d dolerite and Ke dolerite.

ge to local base

d coal and lithole coal seam

water levels appring 2006-2007

e from overlying

ge to local base

d dolerite and Ke Gus seam

meability depenuring. Likely to bharge from ove. harge to regionr?)

1613755_Mem_22 February 20

w 284 m beloan be assume

s

red dolerite and

decreases with

ic surface gene

atercourses charge areas

gs are discharg

n the extent of

g groundwater

Karoo sediments

level (Vaal Rive

logical partings

roximately 100 and 40-60 mbg

g groundwater

level (Vaal Rive

Karoo sediments

nds on extentbe very low. erlying groundw

al base level (V

_006013

ow ed

d

rally

ge

s

er?)

l in

er?)

s

t of

water

Vaal

ME

F

Mike Beeslaar skom Majuba UCG

Figure 3: Updated C

onceptual Hydrogeoological Model

7/41

11613755_22 Febru

_Mem_006 uary 2013

Mike Beeslaar Eskom Majuba

5.0 NU5.1 InThe groundas the volumflow model the coal seastrata on gr

The developsuitable conis available gasifier to thand UCG pr

The objectiv

To repUCG s

To useground

Ch

Th

Th

Th

It is importadata and acassumption

5.2 MThe code sethe WASY Ian interactivdensity-couheat transpoefficiently usdesign remeFEFLOW is

5.3 NThe modelligeological athe groundwmodelled ar

5.3.1 Boundary cthey expresboundary coconditions.

Dirichl

ra UCG

UMERICAntroductiowater flow mme of groundis further utilam to surfaceoundwater in

pment of a mntaminant soa mass tran

he regional groject.

ves of the mo

present, in nusite and surro

e the model tdwater syste

hanges in nat

e coal seam

e groundwat

e potential im

ant to note thccordingly is s. The mode

Modelling elected for coInstitute for Wve groundwapled, thermoort in subsursed to descrediation strat

s used worldw

Numerical ing area wasand structurawater systemrea is approx

Modelling onditions ex

ss the conditionditions resBoundary co

et Type (or c

L GROUNon model has bedwater inflowised to assee as well as nflow rates in

mass transpoource term fosport model

groundwater

odelling inclu

umerical formounding area

to simulate thm, including

tural groundw

m hydrostatic

ter inflow rat

mpact in grou

at the groundpresented as

el will be peri

Code onducting th

Water Resouater modellingo-haline or unrface water reribe the spatitegies and towide as a hig

Model Pros selected baal control. Bom. Most of theximately 32 k

Boundariepress the waons of know

sult in differeonditions in a

constant hea

NDWATER

een constructw that may bess water leveto assess thento the gasifi

ort model usinr the gasifiercan be utilissystem durin

ude:

m, the principas; and

he gasificatio:

water levels;

pressure; an

e into the ga

undwater lev

dwater flow ms a preliminaodically upda

e modelling urces Planning system forncoupled, vaesources wital and tempo

o assist in degh-end groun

operties ased on a cooundaries of te boundarieskm, and the a

es ay the considn water flux,nt solutions h

a groundwate

d) boundary

8/41

R MODELL

ted and updae expected toel drawdowne impact of per.

ng the flow mr which is pre

sed to assessng the opera

ple hydrogeo

on activities a

;

nd

asifier.

vel as result

model has bary model usated once ne

is FEFLOW.ng and Syster three and twariably saturath or without oral distributesigning alterndwater num

nceptual mothe numericas were selectarea is 32,16

dered domain or known vahence the imer flow mode

y conditions o

LING

ated to addreo impact on tn impacts in tpossible goa

model as a besently unavs the possibleational and po

logical flow p

and hence a

of goafing.

een developsing a concepew data beco

. This is a finems Researcwo-dimensioated, transienone or multiion of groundrnatives and

merical mode

odel and alsoal model werted along the69,352 m2.

n interacts wariables, suc

mportance of el can be spe

or:

ess key operthe UCG prothe various afing and sub

ase is subjecailable. Oncee migration oost closure p

processes oc

ssess potent

ed on the baptual model wome availabl

ite element pch, Ltd. Berlinnal, areal annt or steady sple free surfadwater contaeffective molling tool.

combinationre chosen to e watersheds

with its enviroh as piezomstating the c

ecified either

1161322 F

rational quesocess. The gaquifers extebsidence of th

ct to the avae sufficient inof contaminaphases of the

ccurring at th

tial impacts o

asis of spatiawith significale.

package devn, Germany.

nd cross-sectstate flow, maces. FEFLO

aminants, to onitoring sch

n of topograpreflect the g

s. Perimeter

onment. In otetric head. D

correct boundas:

3755_Mem_006February 2013

stions such roundwater nding from he overlying

ilability of a nformation ants from thee gasifier

he Majuba

on the

ally limited ant

veloped by FEFLOW is

tional, fluid mass and OW can be plan and emes.

phical, eometry of of the

her words, Different dary

63

e


Neuma

A mixt

The model dgasifier to m

The boundanumerically boundary co

5.3.2 The hydrogmodel, fieldvariable, anrepresent th

Table 3: MoAquife

Shallow Aquifer

IntermediaAquifer

Coal seam

Lower Aqu

5.3.3 A finite elemelement grid174,512 elenumerical m

ra UCG

an Type (or s

ure of the ab

domain was minimise imp

aries of the nby what is re

ondition).

Model Layeological set data and ge

nd is controllehe different a

odel Layers r Mod

Layer Layer

ate LayerLayerLayer Layer

m Layer

uifer Layer

Finite Elemment networkd was compiements and 9model area.

specified flux

bove.

designed to act from UC

numerical moeferred to as

yers tting is repreeology as dised by the geoaquifers as d

in relation tel Layer

r 1 r 2

TW

r3 r4 r 5 r6

CUSL

r 7 C

r 8 B

ment Mesh k (grid) was dled by FEFL

99,828 nodes

x) boundary c

ensure the eG activities,

odel are shows a “no-flow”

sented by anscussed in thological inforescribed in T

to Geology

Topsoil Weathered d

Contact doleUnweatheredSugary dolerLower Sedim

Coal seam la

Base sedime

designed to pLOW, which fs. Figure 5 il

9/41

conditions; o

edge of the mthus avoidin

wn on Figureboundary co

n eight-layerhe earlier secrmation receTable 3.

Lit

dolerite, Sed

erite, Sedimed, unfracturerite, Sedimen

mentary unit.

ayer

entary unit

provide a higfacilitated thelustrates a th

or

modelling dog boundary e

e 4. These boondition (zero

ed model bactions of the ived from Es

thology Unit

imentary uni

entary unit. ed dolerite unntary unit.

gh resolutione constructiohree-dimens

main is sufficeffects on the

oundaries areo specified flu

sed on the ureport. The tskom UCG. T

t

t

nit.

of the numen of a trianguional view of

1161322 F

ciently distane model resu

re representeux Neuman

updated concthickness of tThe model la

erical solutionular mesh cof the finite ele


nt from the ults.

ed Type II

ceptual the layers is

ayers

n. The finite onsisting of ement

63


Figure 4: Num

ra UCG

merical Modell Boundaries ((Blue dots indi

10/41

icate the drainnage system o

over the mode

1161322 F

elling domain)


63


Figure 5: Thr

5.4 M5.4.1 The steady-activities. Thsubsequent

The model wgeological uunder/overemodel calib

The simulatconductivity

ra UCG

ree dimension

Model CaliSteady-sta-state pre-ophis period wat stages.

was calibrateunits and effeestimated, thration. Table

ted water levy or recharge

nal view of finit

ibration ate pre-opeperational staas modelled

ed using the ective aquifeis can be co

e 4 indicates

vel distributioe values can

te element net

erational caage compriseto provide a

observed bor recharge. Smpensated bthe calibrate

on is comparebe altered u

11/41

twork

alibration es the natura

a baseline an

orehole wateShould the aby the adjusted hydraulic c

ed to the mentil an accep

al groundwatd appropriat

er level, the hverage aquiftment of the conductivitie

easured headptable correla

er flow regime initial cond

hydraulic confer thicknesshydraulic cos specified in

d distribution ation betwee

1161322 F

me prior to Uditions for mo

nductivity of ts therefore beonductivity van the model.

and the hyden measured


CG odelling of

the e alues during

draulic and

63


simulated hhydraulic co

Table 4: HyLayer

Layer 1

Layer 2

Layer 3

Layer 4

Layer 5

Layer 6 Layer 7

Layer 8

5.4.1.1 Evapotransalready ove

5.4.1.2 For the purpreasonable model was

5.4.2 The results calibration tDeviations fshould be ragroundwatethe simulate

Table 5: FinBH ID Ob

WMS1

WMS2 WMS3 WMS4

P1 P2 P3

PZ1 PZ2 PZ4

ra UCG

eads is obtaonductivity (K

ydraulic conr

WeatSedimContaSedimUnwedoler

SugaSedim

LoweCoal Base

Evapotrapiration was

ercome the e

Rechargpose of this mand likely tocalibrated us

Steady Stafrom the ste

the observedfrom the straandomly dister levels (Anded and obser

nal calibratibserved WL (

(mamsl) 1675.3

1677.2 1689.8 1680.8 1621.9 1630.4 1624.9 1606.5 1600.7 1601.0

ained. The caK) and recha

nductivity (KLithology U

Topsoil thered doleritmentary unit act dolorite, mentary unit.eathered,unfite unit.

ry dolerite, mentary unit.

er Sedimentaseam layer sedimentary

anspirationnot specifiedffect of evap

ge modelling stu

o result in simsing all availa

ate Calibrateady-state cad groundwateaight line, whtributed indicderson and Wrved groundw

on measure(2005) Simu

(m1

111111111

alibration prorge within a

K) values spUnit

t

te,

ractured

ary unit.

y unit

n d in the mod

potranspiratio

udy, a constamilar regionalable groundw

tion Resultalibration are er levels are ich is the pe

cating that theWoessner 19water elevati

es for the stulated WLmamsl) (1672.2

1677.1 1679.2 1673.8 1619.2 1619.2 1619.5 1613.5 1621.2 1620.7

12/41

ocess was donarrow rang

pecified in thAverage

hickness (m20

37

3

107

3

100 4.5

120

el. It is assuon losses fro

ant rechargel predictions water levels.

ts summarizedplotted againrfect match bere is no bia

992). A correions.

teady state mME(m)

(WLo-WLs)i3.2

0.1 10.6 7.0 2.7

11.2 5.3 -6.9

-20.4 -19.7

∑=-6.9

one by adjuste compatible

he model

m) K

Kx,Ky=0

Kx,Ky=0

Kx,Ky=0

Kx,Ky=0

Kx,Ky=0

Kx,Ky=0Kx,Ky,K

Kx,Ky,K

med that them the system

e rate approxcompared to

d in Table 5 anst the simulbetween the

as toward oveelation coeffic

model MAE(m)

|(WLo-WLs)3.2

0.1 10.6 7.0 2.7 11.2 5.3 6.9 20.4 19.7

∑=87.2

ting the mode with the hyd

value (m/d)

0.3; Kz=0.01

0.01;Kz=0.00

0.03;Kz=0.01

0.0015;Kz=0

0.01;Kz=0.00

0.0152;Kz=0Kz=0.0001

Kz=0.001

e recharge spm.

imately 5mmo spatially dis

and Figure 6lated water leobserved an

er or under pcient of 96%

)i|RMS(

|(WLm-W10.1

0.0113.48.67.412528.547.9416.388.

∑=118

1161322 F

el parametedrogeologica

)

15

0104

15

0.0003

05

0.001

pecified in th

m per year is stributed rec

6 To show thevels in Figund simulatedpredicting thewas obtaine

(m) WLs)i|2 1

0 .4 6 4 5 5 9 .8 .8

86.4


rs for al situation.

e model has

considered harge. The

e level of ure 7 values,

e ed between

63

s


BH ID Ob

WL=Water MAE=MeanRMS= Root

Table 5 shoSociety for T(1992); Spitwas calculamethods: th(Anderson a(WLs) watewater level overall mod

The root meis generally

Figure 6: Com

ra UCG

bserved WL ((mamsl)

level; ME=Me

n Absolute Ert Mean Squar

ows the RMSTesting and tz and Moren

ated for each he mean erroand Woessnr levels. In kechange acro

del response

ean squared not under o

mparison betw

(2005) Simu(m

ean Error; rror; red Error

S error, whichMaterials (A

no (1996). Th observation

or (ME), the mer 1992). Theeping with s

oss the mode(Anderson a

(RMS) errorr over-predic

ween observed

ulated WLmamsl) (

R

h is a CalibraSTM) guidelhe difference borehole. T

mean absolue ME is the standard prael domain. If tand Woessne

r of the grouncting groundw

d water level v

13/41

ME(m) (WLo-WLs)i

1/n=-0.7

RMS% of wat

ation Error Anines for calib

e between thThe error in thute error (MAmean differe

actice, the RMthe ratio is ser, 1992).

ndwater levewater elevati

vs simulated w

MAE(m)|(WLo-WLs)

1/n=8.7

ter level rang

nalysis calcubration of thee simulated he calibration

AE) and the roence betweenMS error wasmall, the erro

el range is 11ons.

water level

)i|RMS(

|(WLm-W1/n=10

SQRT=10e=11.7

ulated accorde model. (Andand the obsen was expresoot mean sqn measured s evaluated aors are only

.7%, which i

1161322 F

(m) WLs)i|2 07.9 0.4

ding to the Aderson and Werved hydraussed by threequared (RMS

(WLo) and sas a ratio to a small part

indicates tha


merican Woessner ulic head e common

S) error simulated the total of the

at the model

63


Figure 7: Cor

Figure 8 shotowards the

ra UCG

rrelation betwe

ows the steae drainage ar

een observed

ady state watreas and tow

water level vs

ter level contwards the nor

14/41

s simulated wa

tours from thrthwest of the

ater level (R2=

he model oute UCG trial m

=0.96)

put. Generalmining area.

1161322 F

l groundwate


er flow is

63


Figure 8: Ste

5.5 O5.5.1 A transient model baseoperational

ra UCG

eady state wat

OperationaIntroductiocalibration h

ed on the watphase.

ter level conto

al Phase Ton as been undter levels me

urs

Transient C

dertaken usineasured in bo

15/41

Calibratio

ng the pre-moth shallow b

on

ining steady boreholes an

state calibrad deep bore

1161322 F

ated groundweholes during


water flow g their

63


5.5.2 The mine pl

Curren

In 2014produc

According to

The model h9.

Gasificationmodel. Eachcompleted.

The determmine develo

Table 6: UC

From the UCwas calcula10 indicated

Panel

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23

ra UCG

Mine plan lan informati

ntly mining o

4 the miningction for 6 ye

o this very b

has been co

n panels of 22h panel’s wo

ination of groopment will p

CG Mine Pla

CG water proated from thed the average

Starting(day

01224364860728496

108120132144156168180192204216228240252264

on provided

n the wester

will continueears.

road mine pl

nstructed to

20m by 100morking progre

oundwater inprobably be d

an specified

oduction date average wae water prod

g time ys)

E

0 0 0 0 0 0 0 0

80 00 20 40 60 80 00 20 40 60 80 00 20 40

by Eskom (S

n side of gas

e to the rema

an it is assu

simulate min

m were definession is 120

nflow into thedifferent from

in the Mode

a provided bater productioduction receiv

Ending time (days)

120 240 360 480 600 720 840 960

1080 1200 1320 1440 1560 1680 1800 1920 2040 2160 2280 2400 2520 2640 2760

16/41

September, 2

sifier 1 (P1-P

ainder of gas

med that gas

ne progress

ned to assign days (4 mon

e workings mm the mining

el

by Eskom, anon from P5 aved from Ma

Panel

24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45

2010) is sum

P30).

sifier 1 and g

sifier 1 and g

as described

n the operationths) and by

may thereforeassumptions

n estimated wand P6, from ajuba UCG.

Startin(da27283031323334363738394042434445464849505154

mmarised as f

asifier 2. Thi

gasifier 2 will

d in Table 4a

onal boundar2020 gasifie

e be conservas incorporate

water producJanuary 200

ng time ays) 760 880 000 120 240 360 480 600 720 840 960 080 200 320 440 560 680 800 920 040 160 400

1161322 F

follows:

is gas field w

be complete

and illustrated

ry conditionser 1 and 2 wi

ative; since ted into the m

ction of 16 to09 to July 20

Ending time

2880300031203240336034803600372038403960408042004320444045604680480049205040516052805400


will be in

ed by 2020.

d in Figure

s in the ll be

the actual model.

ns/day that 10. Figure

e (days)

0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0

63


Figure 9: Illus

Figure 10: Av

5.5.3 The calibratobservationwas conducobtained fro

ra UCG

stration of min

verage water p

Transient Ction process

nal data whilected for the som monitorin

ne plan used in

production fro

Calibrationconsists of o

e adjusting thsteady-state g.

n the model

m P5+P6 (Esk

n obtaining a mhe aquifer papre-operatio

17/41

kom).

match betweearameters in nal model us

en the simulathe model w

sing the grou

ated model rwithin a realisundwater leve

1161322 F

results and stic range. Cael measurem


alibration ments

63


The transienPZ2 and PZof the mininindicate sim

5.6 ImImpacts on and gradienusing the as

5.6.1 Scenario 1 wduring the sscenario, w

5.6.1.1 No further doutlined mingasifier 1 an

The gasifierspecifying cthe constanschedule.

5.6.2 Groundwatethe modelleafter 2640 d

Figure 11: Sc

5.6.3 Figure 12 re13 represenperiod. Figu

ra UCG

nt model wasZ4 during theng from the smilar water lev

mpacts onthe groundw

nts, drawdowssumed gasi

Operationawas run usin

steady and trhereas the B

Modellindetailed gasifne plans indind gasifier 2

r mine plan foconstant heant head cells

Simulated er inflow intoed total inflowdays (7.5 yea

cenario 1: Sim

Impact on epresents thents the shalloure 14 and F

s calibrated e beginning otart to 2010. vels to the o

n the grouwater flow regwn and inflow

fication plan

al Phase Sng the calibraransient stateB5 dolerite si

ng Methodofier mine placated the opas discusse

or each timed cells at thein the model

Inflow intoo the UCG mw during the oars) while the

mulated water

groundwae shallow aqow aquifer waigure 15 sho

by using the of gasifier wo

The results bserved one

undwater fgime include

w rates to the described e

cenario 1: ated steady se calibration.ll acts as a b

ology for thns are availa

perational phad in previous

e period and e bottom elevl were theref

o UCG mineine workingsoperation phe average wa

inflow into UC

ter level inuifer water leater level con

ow the coal se

18/41

recorded waorking panel obtained fro

es.

flow regime changes in e gasifier. Theearlier.

No Goafinstate water le. The updatebarrier.

he Calculatable to descrase was sims section.

panel has bevation of the fore specified

e during ths depends onhase of the Uater inflow in

CG mine

n mining arevel contoursntours after 5eam water le

ater level me(panel 1-panm the transie

me the natural ge impacts on

g or Subsievels with theed conceptua

tion of Infloribe how min

mulated for a

een incorporgus coal sea

d exactly acc

he operation the mining

UCG. The manto UCG mine

rea over thes after 26405400 days (1evel contours

easurements nel4). This inent state cali

groundwater n the groundw

dence e hydraulic pal model was

ow Rates ining will progrperiod of 540

ated into theam (layer 7).cording to the

on phase (5panel progre

aximum inflowe is 211m3/d

e 15 year mdays (7.5 ye

15 years) at ts after 2700

1161322 F

s obtained frodicates the pibration simu

levels (hydrawater were s

parameters ds used as ba

nto the UCress. As note00 days (15

e flow model . The floor ele mine worki

5400days) ess. Figure 1w of 252m3/d

d over the mi

mining periears) of mininthe end of mand 5400 da


om PZ1, progression ulations

aulic heads) simulated

determined ases for this

CG Mine ed earlier years) for

by evations of ng

1 shows d occurs ning period.

od ng. Figure

mining ays. Figure

63


16 shown athe mining p

The followin

No imp

After 2southe

After 5the sou

Figure 12: W

ra UCG

section fromperiod.

ng can be co

pact on the s

2700days, theeast of the UC

5400 days, thuthwest from

Water level con

m west to eas

oncluded from

shallow aquif

e maximum CG mine wo

he maximumm the UCG m

ntour map of sh

st through th

m Figure 12 t

fer water leve

distance of torkings within

distance of mine workings

hallow aquifer

19/41

e mining are

to Figure 16

els is seen a

the 1m drawdn the coal sea

the 1m draws within the c

r after 2700da

ea and indica

below:

s a result of

down cone isam aquifer.

wdown cone hcoal seam aq

ays of mining:

ates the chan

the UCG min

s seen a dist

has is seen aquifer.

Scenario 1

1161322 F

nge in water

ning

tance of 1423

a distance of


level over

3m to the

f 1317m to

63


Figure 13: Sh

ra UCG

hallow grounddwater contour

rs after 5400 d

20/41

days of miningg: Scenario 1

1161322 F


63


Figure 14: Co

ra UCG

oal seam piezzometric heads

s after 2700 d

21/41

days mining: SScenario 1

1161322 F


63


Figure 15: Co

ra UCG

oal seam Piezzometric head contours afte

22/41

er 5400 days: SScenario 1

1161322 F


63

Mike Eskom

Figur

Beeslaar m Majuba UCG

re 16: Change in waater level during UCCG mining Scenario 1

23/41

11613755_Me22 February

em_006 y 2013

4.4 lower groundwater zone 24g/appendix f... · mike beeslaar eskom majuba simulated h hydraulic co...

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