Scale Analysis and Inhibitor Evaluation for an Offshore Asset · 2014-10-16 · Oil Trim Exchanger IP Separator Prod. Water Hydrocyclone Cell Oil Heater LP Separator Electrostatic

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


21.10.2014

Introduction


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.

Public

Suyun Wang


21.10.2014

Data Gathering


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


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


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.


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

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Suyun Wang


21.10.2014

Scale Modeling


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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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.


Modeling Results – Departing Pipelines

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Departing

Pipeline

T

(°F)

P

(psig)



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.


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


Modeling Results – CPP Facilities

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CPP Facility T

(°F)

P

(psig)



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.

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Suyun Wang


21.10.2014

DSL Experiment


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.


DSL Schematics

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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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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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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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Suyun Wang


21.10.2014

Conclusion and Recommendation


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.


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


21.10.2014

Questions?

Public

Suyun Wang


21.10.2014

Thank You!

Documents

Scale Analysis and Inhibitor Evaluation for an Offshore Asset · 2014-10-16 · Oil Trim Exchanger IP Separator Prod. Water Hydrocyclone Cell Oil Heater LP Separator Electrostatic