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This Recommmended Require
M
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MRAA GA
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RRD
AS PRE
d to define the mia work plan for co
D-GAS-0
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RRD NBRC TVersioDate
nimum technical nducting the wor
09
MONITO
No. Task IDon of Revision
requirements for k.
ORING
RRD‐GG
6/18
conducting the su
GAS‐09 GAS‐11
Final 8/2013
ubject
This Recom
Subject:
1.0 BaThe Blue methane hydrostatmandatortechnical Observatirequiremecomprehe
Technicalpressure rfor this prgas flow defined befforts prmay be pobenchmar
This RRD of the foll
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Over 15 millioas been no a
While TBC‐01 aORW‐12 on th
ments Document work ta
OMMEND
A Gas Press
d mission (BRC)n pressures inacross the Bn order (Figurts for installinell (ORW) gase by the applan for addre
ressure in ththe gas to floires substanti Such charas the appropa multiphase fine a MRAA human healt
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DED REQ
sure Monito
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ressure monitxas Brine Coe communityressure monier monitoring
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RRD NBRC TVersioDate Page
nimum technical nducting the wor
MENTS D
o recommenduvial Aquifer one metric Requiremenonitoring welent of this RRs when dire
reduced to ao the surface. bsurface geolontly availablere. As the mel is developn hydrostatic
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‐01D showed
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n removed thsure in the th
m vent wells, Tessure decline
No. Task IDon of Revision
requirements for k.
DOCUME
d that reducin(MRAA) to eqnecessary in
nts Documentls to monitorRD is to provecting the d
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6/18
conducting the su
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ng and maintaqual to or lessn order to lift (RRD) definer gas pressuride recommedevelopment
at is less thaetermining a ns and multipatic pressured characterizsite conditiot is an approp
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ith pressure
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GAS‐09 GAS‐11
Final 8/2013 1 of 3
ubject
aining s than ft the es the e and ended of a
an the value phase e was zation ons, it priate
ration
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ttempts to usevel data. Mladder pump
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efine the gamodeling and
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nstallation ofecommendedAttachment 1wells are neceORW wells.
he pressure ommunicatioeal. Before wthology at ea
nstallation ofmonitoring wnstrumentatioanges observe
outine operaownhole pres
ata generateasis.
Quarterly repoperations sha
ments Document work ta
se shut‐in ORany of the shps. It may bere reconfigure
as part of themonitoring ns RRD establis
ve of this RRDfor:
gas pressure
s pressure dassessments.
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f wellhead prwells to dion should beed or expecte
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ure monitorinhave recentlyuse some of
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RRD NBRC TVersioDate Page
nimum technical nducting the wor
ng wells are hy been reconf the shut‐in ORW operati
k. This BRC tncluding the quipment req
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rding pressurtion pressurate readings
e pressure mntain continu
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anges in the
No. Task IDon of Revision
requirements for k.
ampered duefigured with ORWs as pronal data.
task addresseinstallation
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as presentedr analyses (Cl pressure mpressures, in
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RRD‐GG
6/18
conducting the su
e to a lack of w2‐inch tubinessure monit
es the need fof new preese data.
ng network i
ehavior/ migr
RRD are:
d on Figure Charbeneau, onitoring netndependent o
t result in a grouted an
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GAS‐09 GAS‐11
Final 8/2013 2 of 3
ubject
water g and toring
for an essure
in the
ration
1 is 2013) twork of the
good nnular e the
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a daily
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This Recom
Appendixrequiremerequireme
mmended Require
x 1 presents ents. These pents.
ments Document work ta
suggested procedures ca
(RRD) is intendedasks. This is not a
procedures fan be modifie
d to define the mia work plan for co
for data colled or replace
RRD NBRC TVersioDate Page
nimum technical nducting the wor
lection to md as appropr
No. Task IDon of Revision
requirements for k.
meet the aboiate to meet
RRD‐GG
6/18
conducting the su
ove objectivethe objective
GAS‐09 GAS‐11
Final 8/2013 3 of 3
ubject
e and es and
FIGGURE
RRD NBRC TaVersioDate o
1
No. ask IDonof Revision
RRD‐GG
6/18
GAS‐09 GAS‐11
Final 8/2013
&<
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TBC-PMW-007
TBC-PMW-008
TBC-PMW-009
TBC-PMW-010
TBC-PMW-012
TBC-PMW-013
TBC-PMW-014
TBC-PMW-015TBC-PMW-016
TBC-PMW-017
TBC-PMW-011
o
G:\LD
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Date:
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013 1
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_̂
1,000 0 1,000500
Feet
Legend
!(&<Recommended PressureMonitor Well
&< Existing Pressure Monitor Well
_̂ Sinkhole Location
#0 CPT
!A Installed Observation/Relief Well
@A Proposed Observation/Relief Well
#0 MRAA Monitor Well
!H Industrial Water Well
LOUISIANA DEPARTMENT OFNATURAL RESOURCES
RECOMMENDED MRAA PRESSURE MONITOR WELLS
BAYOU CORNE/NAPOLEONVILLE SALT DOMEEMERGENCY RESPONSE
FIGURENUMBER
1Shaw Environmental & Infrastructure, Inc.
A CB&I Company4171 ESSEN LANE
BATON ROUGE, LOUISIANA 70809www.CBI.com
Gas Area Legend
Known Gas AreaInitial Gas Thickness (ft)
0.0 - 0.5
0.6 - 1.0
1.1 - 2.0
2.1 - 3.0
3.1 - 4.0
4.1 - 5.0
5.1 - 6.0
6.1 - 7.0
7.1 - 10.0
10.1 - 13.8
This Recommmended Require
SU
ments Document work ta
UGGE
(RRD) is intendedasks. This is not a
APPE
ESTED
d to define the mia work plan for co
ENDIX
D PRO
RRD NBRC TaVersioDate o
nimum technical nducting the wor
X 1
OCEDU
No. ask IDonof Revision
requirements for k.
URES
RRD‐GG
6/18
conducting the su
S
GAS‐09 GAS‐11
Final 8/2013
ubject
This Recom
1.0 IntThis appeThe procegenerate substitute
2.0 CoA licensedthis RRD.
3.0 Sp
3.1 PPressure new presPressure actual pre
3.2 PDownholedirectly mdepth as schedule.more freqexamples wells. Oshould be
4.0 DeThe follow
• Fom
• Wthw
mmended Require
troductionendix is intendedures in thisthe data reqe procedures
ontract Sed drilling con
pecialized
Pressure Gagauges are cssure monitomeasuremenessure ranges
Pressure Tre recording pmeasuring forthe pressur For the prequent data m of stand‐alother vendorse capable of m
efinitions wing definitio
ormation premeasured dire
Wellhead preshe MRAA lesswater level rise
ments Document work ta
n ded for use as section haveuired in Sectcan be used
ervices tractor will b
d Field Equ
auges urrently mouoring well. Tnt instruments observed or
ransducerspressure tranrmation pressre monitoringessure data, fmay be necesone downhols also providmeasuring pre
ons are applic
essure: Pressuectly or calcul
ssure: Pressurs the hydrostaes, the wellhe
(RRD) is intendedasks. This is not a
as a procedure been used btion 2.0 of thas long as the
be required to
uipment
unted on thehese allow ftation should expected at
s nsducers elimsures in the wg well screeformation pressary depende recording de similar recessure to a m
able to this a
ure in the gasated from the
re at the wellatic pressure ead pressure
d to define the mia work plan for co
ral reference by one or moe RRD. In pre requiremen
o install the p
wellhead at for daily pre be selected the site wells
minate the newell perforatn interval aessures on a ing on the otransducers cording transinimum accu
ppendix:
s interval in te wellhead pr
head; this prdue to the wwill decline.
RRD NBRC TaVersioDate oPage
nimum technical nducting the wor
for obtainingore Blue Ribbreparing the wnts in Section
pressure mon
each well anessure observto provide as.
eed for calcutions. A trannd records p15‐minute babserved respand installatisducers. Theracy of 0.1 ps
the geologic hressure and t
ressure is detwater level in t
No. ask IDonof Revision
requirements for k.
g the data reqon Commissiwork plan to2.0 are met.
nitoring wells
nd should bevation of weaccurate read
ulating formasducer is instpressures of asis are probponses. Attacion equipme selected prsi.
horizon of inthe water leve
ermined by tthe well. In a
RRD‐GG
6/18
conducting the su
quired in theoners to obta address this
s recommend
e installed onellhead pressdings based o
ation pressurtalled at the a predeterm
bably sufficienchment 2 prent for pressuessure trans
terest. This cel in a well.
the gas pressua given well, a
GAS‐09 GAS‐11
Final 8/2013 1 of 3
ubject
e RRD. ain or s RRD,
ded in
each sures. on the
res by same mined nt but esents urized ducer
an be
ure in as the
This Recom
5.0 PrThe expan
5.1 InsInstall 11previously
The wells include aMRAA anwells shafrom the that contr
Prior to ineach locaboring nemoved to
5.2 InsThe press
The transthat will sthrough sto a shorwellhead opened aopen whithrough dthe transdvalve.
5.3 DaWellheadweekly.
mmended Require
rocedure nsion and mo
stallation o additional My‐referenced
shall be instappropriate sand overlying all be consistegas interval rols gas press
nstallation of ation to definear a propose the vicinity o
stallation osure gauges sh
sducers can bserve as a stuhould be instt lubricator‐twhile the mnd the transdle the transdduring installaducer will ha
ata Collectio pressures sh
ments Document work ta
onitoring of th
f Pressure MRAA pressuresults of pre
alled in accorafety precautaquitard. Tecent with pracin the MRAAsure at all tim
each pressurne the litholoed pressure mof the existing
f Pressure hould be inst
be installed uffing box allotalled when ttype assemblaster valve isducer loweredducer is loweation. Becauave to be pu
on hould be rec
(RRD) is intendedasks. This is not a
he pressure m
Wells ure monitor weliminary gas
rdance with stions with rechniques/metctices that prA. The pressues.
re monitoringogy for use inmonitoring wg CPT location
and Wateralled above t
using a simplowing the trahe cables arey so that thes closed. Ond into the pered into the use the transdlled up into
corded daily.
d to define the mia work plan for co
monitoring ne
wells at the behavior ana
standard accespect to the thodologies uovide accuraure monitorin
g well, it is recn well designell location sn.
r Level Equhe master va
e pressure pnsducer and e assembled be transducer,ce the wellherforations. Fowell. This wducer cable wthe lubricato
The pressu
RRD NBRC TaVersioDate oPage
nimum technical nducting the wor
etwork includ
general locaalyses and sit
eptable and/opresence ofused to instate and reliabng wells shou
commended . In the evenhown on Fig
uipment lve on each p
pass‐through cable to be loby the vendor cable, and fead assemblyor safety pur
will reduce prewill need to por‐type assem
re transduce
No. ask IDonof Revision
requirements for k.
es the follow
ations (Figuree ORW opera
or modified df elevated gaall additional ble measuremuld to be inst
that CPT borint that there ure 1, the we
pressure mon
fitting shownowered into tr. The pass‐thfittings can by is set up, thposes, the floessure on thepass through mbly before c
er data shoul
RRD‐GG
6/18
conducting the su
ing steps.
e 1) based oational data.
drilling practics pressures ipressure mo
ments of prestalled in a ma
ings be instalis an existingell location c
nitoring well.
n in Attachmthe well. The hrough is attabe installed ohe master vaow valve shoue transducer the master v
closing the m
ld be downlo
GAS‐09 GAS‐11
Final 8/2013 2 of 3
ubject
n the
ces to in the onitor ssures anner
led at g CPT an be
ment 2 pass‐ached on the alve is uld be pass‐valve, master
oaded
This Recom
5.4 OpCompleteequipmendata.
5.5 DAll data, ilevels, forto the LDNand assoc
TBC shourates anrecommepressure quarter.
6.0 At• A
C
• Afit
7.0 FONo formsdocument
8.0 ReCharbene
RMyers, J.,
M
mmended Require
peration ane routine O&Mnt to maintain
Data Submincluding but rmation pressNR in an orgaciated directiv
ld submit opd formationnded equipmmonitoring w
ttachmentttachment 1harbeneau
ttachment 2tting
ORMS are providedting and subm
eferenceseau, R. C., 20Ribbon Comm, 2013, Interp
May 10, 2013:
ments Document work ta
d MaintenaM of the presn continuous
ittal and Renot limited tsures, and opanized formatves.
perational qun pressure ment, water pwells. The qu
ts 1—Model An
2—Examples
d but it is recmitting the in
013, Model Anission May 2,retation of AnCB&I.
(RRD) is intendedasks. This is not a
ance sure monitoroperation an
eporting to well constperation and t once per da
arterly reporchanges duproduced, anarterly report
nalysis of Me
of recording
commended formation.
nalysis of Met, 2013. nalyses of Ga
d to define the mia work plan for co
r wells and sund provide ac
ruction diagrmaintenancey or as specif
rts to LDNR oring the qund any work‐ts should be
ethane Gas
g pressure tr
that forms b
thane Gas Be
as Samples O
RRD NBRC TaVersioDate oPage
nimum technical nducting the wor
urface and docurate and re
rams, CPT date records, shfied by LDNR
on gas removuarter, main‐over activitiesubmitted w
Behavior at
ansducers an
be developed
ehavior at Bay
Obtained from
No. ask IDonof Revision
requirements for k.
wnhole presseliable pressu
ta, flow ratesould continuemergency o
val efforts inntenance pees performedithin 30 days
Bayou Corn
nd high‐press
d (if not alrea
you Corne: re
the Bayou C
RRD‐GG
6/18
conducting the su
sure measureure and water
s, pressures, we to be submorder amendm
cluding ORWerformed ond on the ORW after the end
ne by Dr. Ra
sure pass‐thr
ady develope
eport to Blue
orne Area as
GAS‐09 GAS‐11
Final 8/2013 3 of 3
ubject
ement r level
water mitted ments
W flow n the Ws or d of a
andall
rough
d) for
of
This Recom
M
mmended Require
MODEL ABAYOU
ments Document work ta
ANALYSU CORNE
(RRD) is intendedasks. This is not a
ATTA
SIS OF ME BY DR
d to define the mia work plan for co
ACHMEN
METHANR. RAND
RRD NBRC TaVersioDate o
nimum technical nducting the wor
NT 1
NE GAS DALL CH
No. ask IDonof Revision
requirements for k.
BEHAVIHARBEN
RRD‐GG
6/18
conducting the su
IOR AT NEAU
GAS‐09 GAS‐11
Final 8/2013
ubject
RJC 5/2/13
1
NOTE: This material was developed to provide a quantitative framework for assessing methane gas behavior associated with the Bayou Corne sinkhole. In current form, the material is not based on any site-specific data.
Model Analysis of Methane Gas Behavior at Bayou Corne
Quantify Methane Quantity in the Gas Cap
One of the first quantities that must be determined is the amount of methane gas that is present in the gas cap under different environmental conditions including gas pressure, aquifer water pressure, and soil characteristics. This is difficult because methane is compressible and forms a non-wetting fluid. The approach developed calculates the “standard specific methane volume”, which corresponds to the volume of methane contained in the gas cap under conditions of standard atmospheric pressure, per unit plan area of the aquifer. The standard specific methane volume, designated Dm, has units of feet or meters (cubic feet per square foot plan area, or cubic meters per square meter plan area). For the purpose of this calculation, the soil is characterized by van Genuchten capillary pressure model parameters (α, N, M and Swr).
Figure 1: Pressure distribution for water (Pw) and methane (Pm) at the gas cap located adjacent to the top of aquifer
Figure 1 is presented as a basis for discussion. Pressure head (gage) is shown for water and methane as a function of elevation. The elevation ZP corresponds to the potentiometric surface (water pressure equals atmospheric pressure) for the confined aquifer (MRAA), and the water pressure head is zero at this elevation. Water pressure
Pressure head
Elevation
Pw/gw
hc
Pm/gw
ZP
ZAq
Zmw
Top of Aquifer
Clay
RJC 5/2/13
2
increases hydrostatically with depth, so that the slope of the pressure head-elevation line is equal to -1. The methane is assumed to have constant pressure Pm. It does not show a hydrostatic increase with depth because the methane density is so small (compared to liquid water). At elevation Zmw the methane and water pressures are the same. Pressures are normalized by the specific weight of water γw (pressure à head). The elevation ZAq corresponds to the top of the aquifer, with clay aquitard material located above. The methane gas cap is located between elevations Zmw and ZAq, where the methane-water capillary pressure is positive and does not exceed the entry pressure for methane into the overlying clay. Capillary pressure is the pressure difference between the nonwetting fluid (methane) and the wetting fluid (water). Expressed in terms of head, hc = Pm/γw – Pw/γw. The capillary pressure head hc is shown on Fig. 1 within the gas cap region. hc increases from zero at Zmw to a maximum value at the top of the aquifer (base of the clay), ZAq.
The pressure distribution and capillary pressure distribution are independent of soil material properties. However, soil material properties are essential for establishing the relationship between the capillary pressure distribution and the amount of the different fluids (methane and water) present within the soil pore space. The soil characteristic curve expresses the fundamental relationship between fluid saturation (fraction of pore space occupied) and capillary pressure. Figure 2 shows a representative example for sand texture soil, based on the USDA Rosetta database. The capillary pressure head is measured in feet. At zero capillary pressure the soil is 100-percent saturated with water, the wetting fluid. At a capillary pressure head of about 0.5-ft, the water saturation starts to decrease while the air (methane) saturation increases. At capillary pressure head exceeding about 3-ft, the water saturation approaches its irreducible value (residual water saturation) while the air saturation approaches its maximum value.
RJC 5/2/13
3
Figure 2. Representative soil characteristic curve for sand texture soil
The soil characteristic curve shown in Fig. 2 is expressed mathematically using the van Genuchten model as follows:
( )[ ] MNc
wr
wrwe h
SSSS
−+=
−−
= α11
(1)
Model parameter values used in Fig. 2 are α = 1.07 ft-1, N = 3.18, M = 1 – 1/N = 0.68, and Swr = 0.14.
The soil characteristic curve model is combined with the capillary pressure distribution to calculate the distribution of methane in the gas cap. The methane saturation Sm is calculated from
( ) ( )ewrwm SSSS −−=−= 111 (2)
With porosity n, the specific volume of methane-filled pore space is calculated from
( )⎟⎟
⎠
⎞
⎜⎜
⎝
⎛−−−= ∫∫
Aq
mw
Aq
mw
Z
ZemwAq
Z
Zwrm dzSZZSndzSn 1
Using Boyle’s law to translate from the in-situ methane pressure Pm to atmospheric pressure PAtm, one finds for the Standard Specific Methane Volume:
RJC 5/2/13
4
( )⎟⎟
⎠
⎞
⎜⎜
⎝
⎛−−
−= ∫
Aq
mw
Z
ZemwAq
Atm
mwrm dzSZZ
PPSnD 1 (3)
From Fig. 1, one can see that hc = z – Zmw. Thus, in Eq. (3), one can use
( )[ ]∫ ∫−
−+=
Aq
mw
mwAqZ
Z
ZZMN
e dzzdzS0
1 α
Example One: Assume that ZP – ZAq = 110 ft and that Pm = 50 psig (Pm/γw = 115.4 ft gage). This corresponds to ZAq – Zmw = 5.4 ft, that is, the gas cap has thickness 5.4 ft. With n = 0.375, Pm = 9320 psfa, and Patm = 2120 psfa, Eq. (3) gives
( ) ( ) 64.542.14.52120
932014.01375.0=−×
×−×=MD ft
Thus within a circle of radius 200 feet, the gas cap would contain π * 2002 * 5.64 = 710,000 standard cubic feet of methane. Not all of this would be recoverable; roughly 1/3 would be trapped at residual saturation. The methane gas saturation within the gas cap is shown in Fig. 3, where the elevation datum represents the base of the clay confining bed. The red-dashed curve corresponds to residual methane saturation, where an f-factor = 0.3 is assumed for the sand-texture soil. The volume represented by the region between the saturation and residual curves corresponds to the methane volume that can be removed by venting.
Figure 3. Calculated gas cap saturation distribution based on a gas pressure = 50 psig
RJC 5/2/13
5
Change in Piezometric Surface Elevation
If the piezometric surface elevation changes, then both the methane pressure and thickness of the gas cap will also change. However, since the standard specific methane volume is a measure of the amount of methane present under standard conditions, it will not change. Dm is invariant to changes in ZP. In terms of absolute pressure,
Pm = PAtm + γw * (ZP – Zmw) = γw * (PAtm/γw + ZP – Zmw) (4)
Thus, one may write Eq. (3) as follows:
( ) wwr
AtmmZ
ZemwAqmwP
w
Atm
SnPDdzSZZZZP Aq
mwγγ −
=⎟⎟
⎠
⎞
⎜⎜
⎝
⎛−−⎟⎟
⎠
⎞⎜⎜⎝
⎛−+ ∫ 1
(5)
The only unknown in Eq. (5) is the elevation of the base of the gas cap, Zmw, and this can be found using various means.
Example Two. The elevation of the piezometric surface decreases by 10 feet over Example One. What impact does this have on the gas cap thickness and pressure? For these conditions, the right side of Eq. (5) equals 590. Taking the elevation of the top of the aquifer as the datum (ZAq = 0, ZP = 100 ft), one can find that Zmw = -5.65 ft. Thus the gas cap has thickness 5.66 feet and the gage methane pressure is (100 + 5.65) * 62.4 = 6590 psfg = 45.8 psig. There is a very slight increase in gas cap thickness while the gas cap (gage) pressure decreases by a small amount.
Methane Discharge to a Venting Well
The steady radial mass flux, fr, to a venting well over a gas cap thickness ba is given by
( ) ( )drdP
RTkkrb
drdPkkrb
RTPqrbQf m
m
rmam
m
rma
mmrammmr
2
22µ
πµ
ππρρ =⎟⎟⎠
⎞⎜⎜⎝
⎛⎟⎠
⎞⎜⎝
⎛===
The discharge from the venting well to the atmosphere occurs under atmospheric pressure (standard conditions – ρm,Atm and PAtm) so the radial mass flux fr = ρm,Atm QAtm. Integrating this equation from the radius of the well rw where Pm = Pwell to the radius of influence R where Pm = Pmo gives
( ) ( )22, ln wellmo
m
rMawAtmAtmm PP
RTkkbrRQ −=µ
πρ
RJC 5/2/13
6
This may be written for the volumetric discharge of methane under atmospheric conditions
( )( )w
wellmo
mAtm
rmaAtm rR
PPPkkbQ
ln
22 −=
µπ
It is convenient to write this in terms of the aquifer hydraulic conductivity to water using Kw = ρw g k/µw as follows:
( )( )w
wellmo
mwwAtm
rmwaAtm rR
PPP
kKbQln
22 −=
µγπ (6)
In Eq. (6), µmw is the methane-water viscosity ratio (dimensionless), with magnitude approximately 0.0135.
Example Three: For the conditions of Example One with Kw = 5 ft/d, methane relative permeability = 0.66 and rw = 0.5 ft, what is the venting well discharge? From Eq. (6) the maximum discharge would occur with Pwell = PAtm. However, this corresponds to a pressure head loss of 115.4 ft across the flowing radius, and water upconing cuts the potential discharge. A well-choke is necessary to maintain sufficient pressure at the well and prevent detrimental water buildup. An allowable head loss of 3-ft is reasonable, resulting in a 3-ft water buildup. Thus the well pressure is Pwell = 9130 psfa. Equation (6) gives
( )( )
300,185.0200ln
913093200135.04.62212066.054.5 22
=−
××
×××=
πAtmQ ft3/d
Transient Analysis of Methane Venting
Within the area of capture Ac, the continuity equation for methane volume (under standard conditions) is
Atmmw
mw
mc
mc
m QdtdZ
dZdDA
dtdDA
dtdV
−=== (7)
To be useful, all variables must be expressed in terms of Zmw. From Eq. (5) one finds
( ) ( )⎥⎥⎦
⎤
⎢⎢⎣
⎡−⎟⎟
⎠
⎞⎜⎜⎝
⎛−++
⎟⎟
⎠
⎞
⎜⎜
⎝
⎛−−⎟⎟
⎠
⎞⎜⎜⎝
⎛ −−= −
−
∫ mwAq
mwAq
ZZemwPw
AtmZZ
emwAqwAtm
wr
mw
m SZZPdzSZZP
SndZdD 11
0 γγ (8)
Equation (6) can be written
RJC 5/2/13
7
( )( )
( )( ) ( )( )( )w
wwellmwPwAtm
mwwMo
rmwmwAqMo rR
PZZPP
kKZZQ
ln
22 γγµγ
π −−+−= (9)
The resulting continuity equation gives
( ) ( )( ) ( )( ) ( )( )
( )( )( ) ⎟⎟
⎠
⎞
⎜⎜
⎝
⎛
−−++−−
−−+−⎟⎟⎠
⎞⎜⎜⎝
⎛
−=
∫ eTmwPwAtmemwAq
wwellmwPwAtmmwAqrm
wmwwrc
wmw
SZZPdzSZZPZZPZZk
rRSnAK
dtdZ
1ln1
22
γ
γγ
µπ (10)
Once assumptions are made concerning the time-variation of Pwell, Eq. (10) is integrated to find Zmw(t). A simple spreadsheet model is used. The gas cap pressure, thickness, venting rate, and cumulative venting volume can be calculated accordingly.
Example Four: Calculate the recovery rate and volume for a methane gas cap with initial pressure = 50 psig (based on Example One). It is assumed that a 3-ft pressure head loss is maintained across the radius of influence R so that both Pm and Pwell decrease at the same rate as methane is vented. During venting, the gas cap thickness and relative permeability decrease. The recovery volume and rate are shown in the Fig. 4. It takes more than 5 months to achieve venting of the gas cap.
Figure 4. Venting rate and cumulative volume
Groundwater Pumping to Control Water Buildup
Example Four shows control of water table buildup by limiting the pressure head loss across the radius of influence to 3-ft. Larger venting rates can be achieved through use of dual pump systems, with an individual intake to control the water table elevation. While not directly applicable, the API LNAPL Distribution and Recovery Model (LDRM) was used to evaluate this situation. The same soil parameters are assumed for a vacuum-enhanced recovery system with the vacuum screen section = 5.4 ft and vacuum pressure = 0.2 atm, corresponding to an increased head loss of 7-ft. A groundwater pumping rate of 3 gpm over a screened interval of 15 ft is used to control
RJC 5/2/13
8
water table buildup. Figure 5 shows negligible impact on the net water table elevation due to combined venting and groundwater production.
Figure 5. Water-table buildup associated with venting with 7-ft head loss plus groundwater pumping at 3 gpm
Example Five: Repeat Example Four with a venting well pressure corresponding to 0.2 atm (7-ft = 437 psf) below gas cap pressure. Figure 6 shows that venting rates are much larger and the required venting time exceeds 2 months.
Figure 6. Venting cumulative recovery volume and rate for well pressure combined venting and groundwater pumping system
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Innovations inWater Monitoring
Level TROLL® 700 InstrumentOptimized for aquifer characterization•Gauged (vented) and absolute (non-vented) instruments•Linear, fast linear, linear average, event, step linear, and true •logarithmic logging modesRugged titanium probe and sensor (OD: 1.83 cm; 0.72 in)•
Level TROLL® 500 InstrumentIdeal for groundwater and surface-water monitoring •Gauged and absolute instruments•Linear, fast linear, and event logging modes•Durable titanium probe and sensor (OD: 1.83 cm; 0.72 in)•
Level TROLL® 300 InstrumentSuitable for fresh water and industrial monitoring•Absolute instrument•Linear, fast linear, and event logging modes•Stainless steel probe and sensor (OD: 2.08 cm; 0.82 in)•
Powerful, Accurate, Reliable PerformanceSuperior accuracy• —For guaranteed accuracy under all operating conditions, instruments undergo extensive calibration procedures for pressure and temperature. Each instrument includes a serialized calibration report.Telemetry and SCADA integration• —Access data when you need it. No adapters or confusing proprietary protocols are required. Outputs include standard Modbus/RS485, SDI-12, and 4-20 mA.Low power consumption• —Batteries have a typical life of 10 years or 2 million readings. 8-36 VDC input is compatible with external batteries and solar power.Intuitive interface• —Win-Situ® 5 and Win-Situ® Mobile Software simplify data collection and management. Software features setup wizards, fast data download rates, multiple water level reference options, and more.
Level TROLL® Instruments
Applications
Water Level Instruments for Every Application & Budget
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Level TROLL® 300, 500 & 700 Instruments
General Level TROLL 300 Level TROLL 500 Level TROLL 700 BaroTROLL
Temperature ranges1 Operational: -20-80° C (-4-176° F)Storage: -40-80° C (-40-176° F)Calibrated: -5-50° C (23-122° F)
Operational: -20-80° C (-4-176° F)Storage: -40-80° C (-40-176° F)Calibrated: -5-50° C (23-122° F)
Operational: -20-80° C (-4-176° F)Storage: -40-80° C (-40-176° F)Calibrated: -5-50° C (23-122° F)
Operational: -20-80° C (-4-176° F)Storage: -40-80° C (-40-176° F)Calibrated: -5-50° C (23-122° F)
Diameter 2.08 cm (0.82 in) 1.83 cm (0.72 in) 1.83 cm (0.72 in) 1.83 cm (0.72 in)
Length 22.9 cm (9.0 in) 21.6 cm (8.5 in) 21.6 cm (8.5 in) 21.6 cm (8.5 in)
Weight 245 g (0.54 lb) 197 g (0.43 lb) 197 g (0.43 lb) 197 g (0.43 lb)
Materials Stainless steel body; Delrin® nose cone Titanium body; Delrin nose cone Titanium body; Delrin nose cone Titanium body; Delrin nose cone
Output options Modbus/RS485, SDI-12, 4-20 mA Modbus/RS485, SDI-12, 4-20 mA Modbus/RS485, SDI-12, 4-20 mA Modbus/RS485, SDI-12, 4-20 mA
Battery type & life2 3.6V lithium; 10 years or 2M readings 3.6V lithium; 10 years or 2M readings 3.6V lithium; 10 years or 2M readings 3.6V lithium; 10 years or 2M readings
External power 8-36 VDC 8-36 VDC 8-36 VDC 8-36 VDC
MemoryData records3
Data logs
1.0 MB65,0002
2.0 MB130,00050
4.0 MB260,00050
1.0 MB65,0002
Log types Linear, Fast Linear, and Event Linear, Fast Linear, and Event Linear, Fast Linear, Linear Average, Event, Step Linear, True Logarithmic
Linear
Fastest logging rate & Modbus rate
2 per second 2 per second 4 per second 1 per minute
Fastest SDI-12 & 4-20 mA output rate
1 per second 1 per second 1 per second 1 per second
Real-time clock Accurate to 1 second/24-hr period Accurate to 1 second/24-hr period Accurate to 1 second/24-hr period Accurate to 1 second/24-hr period
Sensor Type/Material Piezoresistive; stainless steel Piezoresistive; titanium Piezoresistive; titanium Piezoresistive; titanium
Range Absolute (non-vented)30 psia: 10.9 m (35.8 ft)100 psia: 60.1 m (197.3 ft)300 psia: 200.7 m (658.7 ft)
Absolute (non-vented)30 psia: 10.9 m (35.8 ft)100 psia: 60.1 m (197.3 ft)300 psia: 200.7 m (658.7 ft)500 psia: 341.3 m (1120 ft)
Gauged (vented)5 psig: 3.5 m (11.5 ft)15 psig: 11 m (35 ft)30 psig: 21 m (69 ft)100 psig: 70 m (231 ft)300 psig: 210 m (692 ft)500 psig: 351 m (1153 ft)
Absolute (non-vented)30 psia: 10.9 m (35.8 ft)100 psia: 60.1 m (197.3 ft)300 psia: 200.7 m (658.7 ft)500 psia: 341.3 m (1120 ft)1000 psia: 703 m (2306.4 ft)Gauged (vented)5 psig: 3.5 m (11.5 ft)15 psig: 11 m (35 ft)30 psig: 21 m (69 ft)100 psig: 70 m (231 ft)300 psig: 210 m (692 ft)500 psig: 351 m (1153 ft)
0 to 16.5 psi; 0 to 1.14 bar
Burst pressure Max. 2x range; burst > 3x range Max. 2x range; burst > 3x range Max. 2x range; burst > 3x range Vaccum/over-pressure above 16.5 psi damages sensor
Accuracy @ 15° C4 ±0.1% full scale (FS) ±0.05% FS ±0.05% FS ±0.1% FS
Accuracy (FS)5 ±0.2% FS ±0.1% FS ±0.1% FS ±0.2% FS
Resolution ±0.01% FS or better ±0.005% FS or better ±0.005% FS or better ±0.005% FS or better
Units of measure Pressure: psi, kPa, bar, mbar, mmHg, inHg, cmH2O, inH2OLevel: in, ft, mm, cm, m
Pressure: psi, kPa, bar, mbar, mmHg, inHg, cmH2O, inH2OLevel: in, ft, mm, cm, m
Pressure: psi, kPa, bar, mbar, mmHg, inHg, cmH2O, inH2OLevel: in, ft, mm, cm, m
Pressure: psi, kPa, bar, mbar, mmHg, inHg, cmH2O, inH2O
Temperature Sensor
Accuracy & resolution ±0.1° C; 0.01° C or better ±0.1° C; 0.01° C or better ±0.1° C; 0.01° C or better ±0.1° C; 0.01° C or better
Units of measure Celsius or Fahrenheit Celsius or Fahrenheit Celsius or Fahrenheit Celsius or Fahrenheit
Warranty 1 year 2 years 2 years 2 years
Up to 5-year extended warranties are available for all instruments—call for details
BaroTROLL® InstrumentThe titanium BaroTROLL measures and logs barometric pressure and temperature. Use the BaroTROLL in conjunction with Level TROLL Instruments.
Win-Situ® Baro Merge™ Software simplifies post-correction of water level data. Barometric readings are automatically subtracted from data collected by an absolute Level TROLL to compensate for changes in pressure due to barometric fluctuations.
24/7 SupportIn-Situ technical support specialists assist with instrument setup, application support, and troubleshooting. Call for free technical support.
1 Temperature range for non-freezing liquids 2 Typical battery life when used within the factory-calibrated temperature range.3 1 data record = date/time plus 2 parameters logged (no wrapping) from device within the factory-calibrated temperature range4 Across factory-calibrated pressure range5 Across factory-calibrated pressure and temperature rangesSpecifications are subject to change without notice. Delrin is a registered trademark of E.I. du Pont de Nemours and Company.
Call to purchase or rent—www.in-situ.com221 East Lincoln Avenue, Fort Collins, Colorado, U.S.A. 805241-800-446-7488 (toll-free in U.S.A. and Canada)1-970-498-1500 (U.S.A. and international)Copyright © 2012 In-Situ Inc. All rights reserved. Mar. 2012 (T3; web)
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In-Situ High Pressure Transducer Cable Pass-Through Fitting