Public
Suyun Wang
Oil & Mining Services
21.10.2014
Scale Analysis and Inhibitor Evaluation for an Offshore Asset
Suyun Wang, Oil & Mining Services, 21.10.2014
Table of Contents
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– Introduction
– Data Gathering
– Scale Modeling
– DSL Experiment
– Conclusion and Recommendation
Public
Suyun Wang
Oil & Mining Services
21.10.2014
Introduction
Suyun Wang, Oil & Mining Services, 21.10.2014
Objectives
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– Scale review of the offshore asset from the production wells to departing pipelines,
then to CPP facilities.
– Scale modeling to estimate the scaling severity.
– DSL experiment to evaluate the scale inhibitor performance.
– Recommendation on the suitable scale inhibitors and initial dose rates.
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Suyun Wang
Oil & Mining Services
21.10.2014
Data Gathering
Suyun Wang, Oil & Mining Services, 21.10.2014
Simplified Diagram of the Offshore Asset
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Production
wells
Departing
pipelines CPP facilities
WA1 WA2 WA3
WB1
WC1
HP
Separator
HGOR
Separator
Oil Trim
Exchanger
IP
Separator
Prod. Water
Hydrocyclone
Oil Heater
LP
Separator
Electrostatic
Heater Treater
Flotation
Cell To Skim Pile
Suyun Wang, Oil & Mining Services, 21.10.2014
Operation Conditions – Production Wells
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Well THT (°F) THP (psig) Production
Rate (BWPD)
Departing
Pipeline
WA1 144 704 122 HP
WA2 142 661 208 HP
WA3 137 649 103 HP
WB1 140 1199 131 HGOR
WC1 140 547 825 HP
Suyun Wang, Oil & Mining Services, 21.10.2014
Operation Conditions – CPP Facilities
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CPP Facility T (°F) P (psig)
HGOR Separator 129 1089
HP Separator 126 464
Oil Trim Exchanger 120 a464
IP Separator 111 160
Oil Heater 132 b160
LP Separator 128 10
Electrostatic Heater Treater 131 10
Prod. Water Hydrocyclone 120 168
Flotation Cell 128 30
– aPressure of Oil Trim Exchanger was assumed to be the same as that of HP Separator.
– bPressure of Oil Heater was assumed to be the same as that of IP Separator.
Suyun Wang, Oil & Mining Services, 21.10.2014
Brine Compositions
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Ion/Neutral
Species
Composition (mg/L)
WA1 WA2 WA3 WB1 WC1
Na+ 5,701 5,819 6,625 8,136 8,782
Ca2+ 2.59 6.72 5.12 17.45 18.67
Mg2+ 3 5 5 24 22
Ba2+ 0.5 3.1 1.5 4.7 4.3
Sr2+ 2.22 4.93 3.78 10.52 9.33
Fe2+ 0 0 0 0 0.2
Cl- 7,500 7,000 8,500 12,500 13,500
SO42- 230.4 211.2 25.6 44.8 12.8
HCO3- 2,184 3,416 3,233 646.6 707.6
Dissolved CO2 0.65 0.649 0.646 0.64 0.637
Physical Property Data
pH 8.1 7.9 8.3 8.1 7.9
Public
Suyun Wang
Oil & Mining Services
21.10.2014
Scale Modeling
Suyun Wang, Oil & Mining Services, 21.10.2014
Modeling Method
– Software: OLI ScaleChem
– Scale modeling performed for
- Production wells
- Departing pipelines: HP and HGOR lines
- CPP facilities
– Scale modeling results reported as
- Scale index
- Precipitation potential in mg/L
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Suyun Wang, Oil & Mining Services, 21.10.2014
Modeling Results – Production Wells
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Well THT
(°F)
THP
(psig)
Barite (BaSO4) Calcite (CaCO3) Strontianite (SrCO3)
SI PP (mg/L) SI PP (mg/L) SI PP (mg/L)
WA1 144 704 0.04 0.0 0.06 0.5 0.43 2.2
WA2 142 661 0.76 4.2 0.61 12.0 0.97 7.2
WA3 137 649 -0.46 0.0 0.42 7.3 0.79 5.1
WB1 140 1199 0.28 3.3 0.24 7.2 0.39 7.2
WC1 140 547 -0.31 0.0 0.32 12.4 0.40 5.9
– WA1: mild strontianite scale.
– WA2 and WB1: mild barite, calcite, and strontianite scales.
– WA3 and WC1: mild calcite and strontianite scales.
Suyun Wang, Oil & Mining Services, 21.10.2014
Modeling Results – Departing Pipelines
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Departing
Pipeline
T
(°F)
P
(psig)
Barite (BaSO4) Calcite (CaCO3) Strontianite (SrCO3)
SI PP (mg/L) SI PP (mg/L) SI PP (mg/L)
WA HP 144 464 0.48 2.2 0.47 8.0 0.83 5.4
126 464 0.57 2.4 0.35 6.7 0.74 5.2
WB HGOR 140 1089 0.28 3.4 0.24 7.5 0.40 7.3
129 1089 0.31 3.9 0.15 4.1 0.34 7.3
WC HP 147 464 -0.34 0.0 0.37 14.8 0.43 6.0
126 464 -0.26 0.0 0.21 8.1 0.33 5.8
– WA HP and WB HGOR: mild barite, calcite, and strontianite scales.
– WC HP: mild calcite and strontianite scales.
Suyun Wang, Oil & Mining Services, 21.10.2014
Modeling Results – Departing Pipelines
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WB HGOR line to CPP
WC HP line to CPP
Mild barite, calcite, and strontianite scales
Mild calcite and
strontianite scales
Suyun Wang, Oil & Mining Services, 21.10.2014
Modeling Results – CPP Facilities
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CPP Facility T
(°F)
P
(psig)
Barite (BaSO4) Calcite (CaCO3) Strontianite (SrCO3)
SI PP (mg/L) SI PP (mg/L) SI PP (mg/L)
HGOR Separator 129 1089 0.33 3.9 0.17 4.1 0.37 7.30
HP Separator 126 464 0.40 3.4 0.46 18.2 0.65 8.5
Oil Trim Exchanger 120 464 0.42 3.7 0.39 16.5 0.59 8.5
IP Separator 111 160 0.50 4.1 0.38 15.0 0.62 8.6
Oil Heater 132 160 0.36 3.4 0.48 19.7 0.64 8.9
LP Separator 128 10 0.39 3.5 0.47 19.1 0.64 8.9
Electrostatic Heater
Treater 131 10 0.37 3.4 0.48 19.8 0.65 9.0
Hydrocyclone 120 168 0.43 3.8 0.41 17.1 0.61 8.7
Flotation Cell 128 30 0.38 3.5 0.46 19.1 0.64 8.9
– All facilities: mild barite, calcite, and strontianite scales.
Public
Suyun Wang
Oil & Mining Services
21.10.2014
DSL Experiment
Suyun Wang, Oil & Mining Services, 21.10.2014
DSL Equipment
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– Three-pump system to enable testing of multiple dosages of a scale inhibitor.
– Monitor differential pressure change across the coil for indication of scale
formation.
Suyun Wang, Oil & Mining Services, 21.10.2014
DSL Schematics
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Suyun Wang, Oil & Mining Services, 21.10.2014
Test Method
– Test conditions
- Brine: adjusted synthetic WA2 produced brine (100 mg/L Ca2+)
- Temperature: WA2 tubing head temperature of 142°F
- Scale inhibitors: SCALETREAT A and SCALETREAT B (phosphonate types)
- Inhibitor dosages: 70 ~ 0 ppm
- Test duration: 75 minutes for each inhibitor dosage
– Test procedure
- Prepared the cation, anion, and inhibitor dosed anion brines according to water
compositions.
- Pumped the cation and total anion brines in a 1:1 ratio, with a combined flow rate
of 3 mL/min.
- Introduced the inhibitor stepwise from high concentration to low concentration.
Pressure increase during dosing indicated that the inhibitor was not effective at the
dosed concentration.
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Suyun Wang, Oil & Mining Services, 21.10.2014
Blank Test Results
– DSL blank tests with various adjusted calcium contents to make sure scale
forms in reasonable time at 142 °F.
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Suyun Wang, Oil & Mining Services, 21.10.2014
Inhibitor Test Results
– DSL inhibitor tests with 100 mg/L calcium in brine at 142 °F.
– MIC = 60 ppm for SCALETREAT A, 40 PPM for SCALETREAT B.
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Public
Suyun Wang
Oil & Mining Services
21.10.2014
Conclusion and Recommendation
Suyun Wang, Oil & Mining Services, 21.10.2014
Conclusions
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– Scale modeling results suggested
- Production wells: mild strontianite scale for WA1 well; mild barite, calcite, and
strontianite scales for WA2 and WB1 wells; mild calcite and strontianite scales for
WA3 and WC1 wells.
- Departing pipelines: mild barite, calcite, and strontianite scales for WA HP and
WB HGOR lines; mild calcite and strontianite scales for WC HP line.
- CPP facilities: mild barite, calcite, and strontianite scales for all facilities.
– DSL experimental data showed
- Both SCALETREAT A and SCALETREAT B were able to inhibit scale formation
at 142°F in the adjusted synthetic WA2 produced brine (100 mg/L Calcium).
- MIC were determined to be 60 ppm for SCALETREAT A and 40 ppm for
SCALETREAT B.
- SCALETREAT B exhibited better performance than SCALETREAT A.
Suyun Wang, Oil & Mining Services, 21.10.2014
Recommendation
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– Two treatment plans
- Continuously inject SCALETREAT A with an initial dosage of 60 ppm upstream of
the departing pipelines.
- Continuously inject SCALETREAT B with an initial dosage of 40 ppm upstream of
the departing pipelines.
– The actual dosage can be optimized in field trials.
– Final selection on SCALETREAT A or SCALETREAT B for field trial are based on
their compatibility with produced fluids and other production chemicals, product
price, raw material availability, etc.
Public
Suyun Wang
Oil & Mining Services
21.10.2014
Questions?
Public
Suyun Wang
Oil & Mining Services
21.10.2014
Thank You!
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