scaling – from production to reinjection 3rd gns science...
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Scaling – From Production to Reinjection3rd GNS Science - JOGMEC Workshop
Ed MroczekGNS Science Wairakei New Zealand
Tokyo10 December 2018
GNS Science
Outline2
• The New Zealand geothermal reservoir • Rotokawa reservoir• ECC cement grout• Deep Acidity Examples and Management • Silica Scaling • Calcite Scaling • Anhydrite Scaling• Iron sulphides• Antimony sulphide (stibnite)• Silica and Calcite Scaling Management
GNS Science
B
A
C
D
EFG
near-neutralchloridefluids
mixing &conductive cooling
mixing &conductive cooling
hanging aquifercondensation
steam cap
boiling-point fumarolicdischarge
condensate potcold gas
seep
boilin
g oin p
tne
velop
erecharge
aquiclude
acidcondensate fluids
major convectiveupwelling
mixingrecharge
recharge
300
Co
200 Co
mixingrecharge
piezometric surface
The New Zealand Geothermal Reservoir3
B. Christenson (GNS)
• Boiling – injects CO2& H2S in
the shallow reservoir– Mixing with
oxygenated fluids– Very corrosive
• Deep Acidity - Magmatic Fluids – 4SO2 → H2S + 3H2SO4
– HClX
• Vapour Dominated– Cl in superheated vapour
• transported as HCl– concentration
• pH of the brine• temperature of
separation
X
GNS Science
The New Zealand Geothermal Acid Features4
Rotorua
Rotokawa
10B
Cl/10
10SO4
TauharaRelative B-Cl-SO4
TH1 (1964)TH1 (1967)TH2TH2 (1967)TH3 (1967)TH6TH9TH10TH11TH12TH13TH14
WairakeiRelative B-Cl-SO4
WK26BWk30Wk105Wk243Wk245Wk247
Relative B-Cl-SO4RotokawaOhaaki
Wairakei
TauharaCl/B
20
30
40
56
80
1960's
GNS Science
B
A
C
D
EFG
near-neutralchloridefluids
mixing &conductive cooling
mixing &conductive cooling
hanging aquifercondensation
steam cap
boiling-point fumarolicdischarge
condensate potcold gas
seep
boilin
g oin p
tne
velop
erecharge
aquiclude
acidcondensate fluids
major convectiveupwelling
mixingrecharge
recharge
300
Co
200 Co
mixingrecharge
piezometric surface
The New Zealand Geothermal Reservoir5
B. Christenson (GNS)
GNS Science
New Zealand Rotokawa Reservoirhighly corrosive acidic SO4-Cl rich fluids
• Rotokawa Cross Section Winick et al, 2009. NZGW
6
1 Deep upwelling reservoir fluids;
rise to shallow levels [5]
2 Clay Cap (weekly developed)
3 Central Field Fault
4 Lake Rotokawa extensive area
of acid-SO4-Cl fluids
6 Drain back downward to
generate advanced argillic
alteration in RK4/RK2
7. Boiled fluids inject large
quantities of CO2 and H2S into
steam condensates
8 Mix with oxygenated fluids
GNS Science
External Casing Corrosion of Cement Grouts7
Milestone, IRL Ltd; GRC 1990
Cement Grout Dissolution
• Ohaaki well Br23– 0.4 mol/kg H2CO3
– pH 5 @150°C• 10 months exposure
– fully carbonated all samples and cause severe corrosion
– Added quartz sample• lost over 60% of its volume
– Pure cement • 35% of its volume lost
GNS Science
L
Deep AcidityCommon in Many Volcanic Geothermal Fields
8
Not all acid is created equal!HSO4/SO4 & CO2/HCO3 Buffers
• SO4/HSO4/ & CO2/HCO3 Buffers – pH at depth is neutral– Acidity increases markedly at shallow depth– Well bore corrosion
• HCl– Completely dissociated– Low pH in reservoir and at shallow depths
Lichti et al; NZGW 1998
GNS Science
Deep Acidity – GNS reviews9
Cl/210K
TNa/K/oC
100
150
200
250
300
350
KCl
NaCl
Dissolved Rock
• Mt Apo; Philippines– pH 3.2-5.5– Cl-Na-K relative
proportions– No excess Cl– Acidity due to SO4
– Silica• 1000 mg/L• No deleterious scaling • Little pipe corrosion• Amorphous silica
protects from corrosion
Nogara et al. 27 Workshop on Geothermal Reservoir Engineering, 2002
GNS Science
Deep Acidity – Philippines 10
• Mt Apo; – Now lower pH 2.5– Corrosion observed– pH too low for Am Silica protection– NaOH injection trial
• pH to 4.5– Not successful
• Mahanagdong– pH 2.87 - 4.05 – NaOH solution through a 1″
Incoloy 825 tubing at 20 m depth– Thinning rate decline
• 1.05 to 0.21 mm day−1
– corrosion control pH of 4.5
Tamboboy et al. 2015; WGC
Ármannsson H (2012) Geochemical Aspects of Geothermal Utilization.
GNS Science
Deep Acidity – Philippines 11
• Tiwi– The production liner was removed and the corrosive zones isolated – injection of 4 wt.% NaOH at a depth of 1070 m (12.7 mm capillary tubing of
Inconel 625. – The pH is controlled at 4.5–5.0.– Overdosing with NaOH (pH > 6) is found to exacerbate silica scaling– Dissolved iron concentrations in the fluid have been reduced by 80%
Ármannsson H (2012) Geochemical Aspects of Geothermal Utilization.
GNS Science
NaOH Steam Scrubbing12
• Italy, Larderello. – downhole using a capillary
and at the wellhead using corrosion-resistant wellheads,
• USA, The Geysers, California. – Superheated to wellhead– NaOH has been used
similarly– trials successful with dry
steam scrubbing using calcite packed beds and amines which avoids the reduction in steam utilization efficiency
Ármannsson H (2012) Geochemical Aspects of Geothermal Utilization.
https://docplayer.net/50647816-The-geysers-steam-purity-steam-scrubbing-process-evolution-innovationsgrc-o-m-best-practices-workshop-october-23-2016.htm
GNS Science
• Major & difficult problem – given the large volumes of brine disposed• Above
surface piping• Reinjection
Wells
Silica Scaling in New Zealand 13
GNS Science
New Zealand “Unnatural” Acidity – pH Mod 14
0.0
1.0
2.0
3.0
4.0
5.0
6.0
7.0
8.0
9.0
10.0
0.00
1.00
2.00
3.00
4.00
5.00
6.00
7.00
8.00
9.00
10.0
0
11.0
0
12.0
0
13.0
0
14.0
0
15.0
0
16.0
0
mls 0.01N H2SO4 added
pH
pH 6.7 (86% of acid requirement)
pH 6.2 (7% of acid requirement)
pH 5.5 (7% of acid requiremen
• Control of silica scaling – H2SO4 dosing – 3 NZ Geothermal fields
• Including Rotokawa ! – Difficult process to control
• Adding acid• Corrosion pH 5.5 (@25°C• Heavy metal (Sb & As) causing
corrosion on Fe pipes (Quest Integrity GNS sponsored research (Lichti et al; WGC 2015)
• Water rock reaction of acidic fluids
• Operational and Infrastructural– Acid delivery, storage,
handling, cost Mroczek et al. WGC 2010.
GNS Science
Experimental Chemistry - Laboratory StudiesPrivate Companies (NZ & International) NEDO - GNS Corrosion studies
“real world”
“simulated world”
High Temp./Press. Apparatus400oC & 500 bar
15
GNS Science
Distance from well (m)0 20 40 60 80 100 120 140
Perm
eabi
lity
redu
ctio
n fa
ctor
0.50
0.55
0.60
0.65
0.70
0.75
0.80
0.85
0.90
0.95
1.00
Injection into of 130oC Fluid into a Reservoir at 80oC at 50 kg/s for 10 yearsAssumptions about the geometry of the porosity of the aquifer required
With silica deposition rate data we can calculatethe effect of scaling in the reinjection aquifer !
Days
0 1000 2000 3000 4000
Pres
sure
(mPa
)
5.0
5.1
5.2
5.3
5.4
5.5
5.6
with permeability reduction
without permeability reduction
Distance from well (m)
0 20 40 60 80 100 120 140
Dep
ositi
on (k
g m
-3)
0
2
4
6
8
10
12
14
16
18
20
t /oC
mg
cm-2
yea
r-1
40 60 80 100 1200
5
10
15
20
25
30
35
40
8wt% Al
6wt% Al1wt% Al
Geochimica, 1998; NZGW 1997, 1999; Geothermics 2000.
Scaling – Experiments and Modelling 16
GNS Science
Calcite Deposition – Production Problem
Ca++ + CO3= ↔ CaCO3
Most CO3= present as HCO3
- or H2CO3
On boiling H2CO3 → CO2
↑ + H2O2HCO3
- → CO3= + CO2
↑ + H2OOverall2HCO3
- + Ca++ → CaCO3 + CO2(g) + H2O
Calcite Scaling Thermodynamics
RETROGRADE SOLUBILITY
17
GNS Science
• Deposition Kinetics - Rapid (heterogeneous nucleation – seed available)
• Occurs within wellbore just above flash point • Scaling calibrated for the field
Some wells predicted to scale but don’t Depends on how the boiling occurs and
rapidity of depressurization• Severe scaling can results out in the formation
Cannot remediate easily• Surface Pipes
• Mixing of incompatible fluids (high HCO3and high Ca
• Degassing due to depressurization
Calcite Scaling Kinetics
Water+Steam
Water Pres
sure
incr
easi
ng
scaling
18
GNS Science
Anhydrite Scaling
• Ca2+ + SO4= = CaSO4
• Caused by mixing Ca and SO4 fluids • Independent of pH• Retrograde solubility• Not common in production wells• Mainly volcanic geothermal
environments• But often shallow acid-sulphate zone
present • Antiscalant (like for calcite) effective• Often self limiting • Treat during well drilling (case off or
injecting calcium salts can work)
19
After Mubarok & Zarrouk,2017
Neutral (Calcium)
Acid-SO4
GNS Science
Iron Sulphides
• Acid fluid can carry a lot of iron from corrosion/ erosion
• Precipitates in response to boiling & cooling- sensitive to pH and H2S & H2
gas fugacity (redox)• Severe problem can occur
- when mixing incompatible fluids (low and high pH, high iron, gas , differing enthalpy)
20
Pyrite FeS2; Pyrrhotite Fe(1-x)S (x = 0 to 0.2)
Jamero et al. 2018
Jamero et al. 2018 Geothermics
GNS Science
Antimony (& Arsenic) Sulphides
• Particular problem in NZ Geothermal Fields (Brown, 2011)
• Now reported elsewhere• Binary Plants• pH mod for silica inhibition
• Low pH and cool temperatures required
• Highly insoluble under these conditions
• e.g. pH 5 & 15 mg/l H2S 150oC 3.34 mg/l; 100oC 0.008 mg/l
• Caustic dissolves (anion H2SbO3-)
• Antiscalants show promise (Gill, 2013)
2H3SbO3 + 3H2S = Sb2S3 + 6H2O
21
GNS solubility experiments (Olsen et al 2018)
GNS Science
• Keep the scaling in the wellbore• Maintain WHP and control output
NZ Calcite Scaling Management
0.1 mg/l Ca
0.25 g/tonne CaCO3
300 275 250 225 200 175 150t/ oC
-3
-2
-1
0
1
2
3
Log
Q/K
BR56BR59BR61
1 Step Flash
Paul Bixley
scaled liner
22
0 0.05 0.1 0.15 0.2 0.25g calcite/tonne flow
1800
1600
1400
1200
1000
800
Casin
g de
pth/
m
After Brown (UNU-GTP-2013-39,2013)
GNS Science
• Antiscalant injection • Highly effective• Below boiling point• Many commercially available• Need to choose appropriate
one (lab and field testing)• Not out in the formation
NZ Calcite Scaling Management 23
GNS Science
NZ Scaling Management – calcite & silica• Periodic Well Workovers
• Reaming• Acidizing (implications for well integrity!)
– HCl & HF• High pressure water blasting• Broaching• Novel Chemical treatment (Alkali, EDTA)
24
Broaching Tool
Rig
What is more expensive Avoidance or workovers ?
GNS Science
Geo40 (New Zealand) Manufacture of colloidal silica
Ohaaki Commercial Demonstration Plant (in co-operation with Contact Energy Ltd and Ngati Tahu Tribal Lands)
25
GNS Science
Conclusions
Scaling occurs from Production to Reinjection. It cannot be totally avoided.
However thorough chemical understanding of the influent and effluent composition and chemistry, good power station design, monitoring of the reservoir response to production and knowledge on how to deal with the problem all work to minimizes the potential for disaster.
26
GNS Science
Acknowledgements
GNS ScienceContact Energy LtdMercury Energy LtdWairakei Prawn park New Zealand Government Research Funding