PW Society 16 Conference

8/2/2019 PW Society 16 Conference

1/7

Produced Water Society16th

Annual Conference

TORR Canada Inc.www.torrcanada.com 1

Fundamental Approach to Produced Water Treatment:Validation of an Innovative Technology

Marc Saad, M.J. Plebon and Serge Fraser

TORR Canada Inc.

Introduction

The fundamental approach used to develop an innovative technology for produced water treatment

has recently been extensively validated. An understanding of the basic physical characteristics of produced

water, specifically the oil and emulsion droplet size distribution, poses the basis of performance of most

treatment processes. The presented innovative technology has been designed accordingly to address these

physical phenomena and has recently been validated through several field trials. The various successes of

the field trials provide a new alternative technology for produced water treatment that allows for meeting

the strictest of discharge regulations and re-injection criteria. Results have also proven that the need to

understand and appropriately quantify the produced water characteristics in order to be able to select and

efficient performing technology is inevitable.

Development and Control

Separation of smaller-sized oil-in-water (OIW) emulsions has been developed through extensive

experimental testing, in both the laboratory and on many fields, and resulted in an innovative technology.

The resulting technology separates and recovers small OIW emulsions with an optimum variable efficiency

that is distributed over the OIW droplet size distribution curve of site-specific PW to deliver an effluent that

meets the requirements of the treatment process.

The treatment process incorporates two stages of oil adsorbing, coalescing and desorbing porous

media in the form of radial-flow cartridges complemented by gravity separation. This is shown in the

process flow diagram of Figure 1 as follows:


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Figure 1: PFD of Technology Process

Development of the process was based on controlling the breaking of OIW emulsions through the

media with removal efficiencies as follows:

- 99% of OIW emulsions having characteristic lengths of 15m and above.

- 97% of OIW emulsions having characteristic lengths between 10m and 15m.



Removal efficiency calculations are weighed by particle count. These oil droplets are coalesced in

the media and released to the separation chamber. The gravity separation of the released oil droplets is

based on Stokes Law as follows:

18/)(2

oilwr gdV

Where rV is the oil droplet rise velocity

d is the diameter of the oil droplet

w is the density of water

oil is the density of oil

is the dynamic viscosity of water

g is the gravitational acceleration


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The process controls the gravity separation of the released oil droplets based on the following criteria:

- Recovery of all released oil droplets having characteristic lengths of 1000m.

- Variable optimum recovery efficiency based on the characteristics of the crude oil in the PW

(see following example).

As a typical case, a crude oil having an API Gravity of 30 would be separated as follows:

Oil Droplet Grav ity Separation Rate

0

10

20

30

40

50

60

70

80

90

100

-400 -200 0 200 400 600 800 1000 1200 1400Oil Droplet Rise Velocity (m/hr)

MediaCartridgeHeight(%)

250 um

500 um

750 um

1000 um

1250 um

1500 um

2000 um

Figure 2: Graph showing example of oil droplet rise velocity in technology process

The graph shows the rise velocity of released oil droplets versus the height of the media cartridges.

In other words, all oil droplets of a specific diameter will be recovered if they have a positive velocity. The

recovery of the oil droplets will depend on the location they were released with respect to the outlet

collection points. The droplets having a negative velocity will be entrained in the effluent. Measurements

of the size of the coalesced oil droplet released from the media cartridges have shown that the normal size

is in the order of millimeters.

The process controls the separated and released oil droplet rise velocity by controlling the flow

distribution in the separation chamber. Heavier oil (API 20) has been used as the basis for the process

design for optimum performance in both parts of the process (emulsion breaking and coalescing and gravity

separation). Removal efficiencies of OIW emulsion breaking and recovery efficiency of released coalesced

oil droplets will determine the OIW concentration of the effluent. This concentration is controlled through

the above process settings and has been measured and validated in several offshore produced water

treatment trials.


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Validation and Results

Two offshore produced water treatment field trials are presented. The results show that for

different site-specific characteristics of produced water, the technology manages to treat and polish the

OIW concentration to meet and exceed the regulation values for overboard discharge.

Offshore Trial I: North Sea FPSO

A trial has been performed on board an FPSO in the North Sea to validate the performance of the

technology in treating site-specific PW. This PW had an average size distribution, as measured by a third

independent party using the Jorin ViPA, as follows:

-10

th

percentile oil droplet diameter of 4.08 m

- 50th

percentile oil droplet diameter of 5.86 m

- 90th

percentile oil droplet diameter of 27.76m

1st StageSeparator1

1st StageSeparator2

Hydro-Cyclone1 Hydro-Cyclone2

INLET:150 - 850 ppm

T= 60- 70Celsius5- 20bar

OUTLET:75- 550 ppm

T = 60- 70Celsius5- 20bar

INLET:100 - 250 ppm

T = 60- 70Celsius5- 20bar

OUTLET:75- 150ppmT = 60- 70Celsius

5 - 20bar

Oil API: 31.8 Oil API: 42.2

ConnectiontoTORR

ConnectiontoTORR

Figure 3: Process Flow Diagram of Produced water treatment line showing TORR tie-in locations.

The oil in the PW had an API density of 31.8, a viscosity of 8 cSt @ 40C, a paraffin content of

6%, and an asphaltene content of 0.35%. The PW temperature was 65C. The production chemicals in the

fluid stream included: a corrosion inhibitor, a scale inhibitor, a demulsifier, and a defoamer.


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TORR Performance - FPSO

78.1

42

127.7

77.1

106.3122.6

3.28

2.21

5.5

1.87

4.02

1.28

190.1

514.2

129.7101.2

16.5

5.6

3.9

2.3

4.2 4.54.3

1.81

2.83.6

2.82.2

1.94

2.6 2.5

133.7

2.14

677.7843.8

42.5

45.5

35.63

44.248.545.32

47.83 42.81

1

10

100

1000

0 5 10 15 20 25 30 35 40 45Total Flow Treated (m)

OIW

(mg/L)

Inlet Conc. (ppm)

Outlet Conc. (ppm)

Figure 4: Oil Removal Performance on Board North Sea FPSO

The effluent from the technologys system was measured for OIW concentration using UK

Department of Trade and Industry approved methods on board the FPSO. The results for both the influent

and effluent are presented above in Figure 4. The trial showed that the technologys process was capable of

reducing the total OIW concentration of the FPSOs specific produced water with an average efficiency of

over 96%.

Offshore Trial II: North Sea Fixed Drilling and Production Platform

Another trial was conducted on board a fixed drilling and production platform in the North Sea to

validate the performance of the technology in treating this different site-specific PW. This PW was

produced from several wellheads and mixed together in a single stream. The platform produces

approximately 4000 BBL of oil (API Gravity 39, viscosity of 3.8cP, a paraffin content of 17%, and an

asphaltene content of 0.4%) and 100,000 BBL of produced water per day (PW Temperature: 70C, PW pH

6.5, and maximum H2S concentration of 2000ppm). Production fluids also come from another platform.

Through the first part of the trial, the technology was to treat the PW downstream of the first stage

separator and upstream of the WEMCO separators. The OIW concentration downstream of the separator

was around 250mg/L. The second part of the trial was performed downstream of the WEMCO separators,

where the PW effluent that is discharged overboard has an average OIW varying between 40 to 50 mg/L.


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1st StageSeparator B

INLET:250 - 400 ppmT = 75Celsius

OUTLET:30- 75ppm

T= 60- 70Celsius

Oil API: 39

Connecion to TORR

Connecion to TORR

WEMCO

Figure 5: Process Flow Diagram of Produced water treatment line showing TORR tie-in locations.

The production chemicals existent in the fluid stream treated by the technology included:

- Corrosion Inhibitor injected in the produced fluids at approximately 39 ppm.

- Scale Inhibitor injected in the produced water at approximately 15 ppm.

- Demulsifier injected in the produced fluids at approximately 15 ppm.

- Demulsifier injected in the produced water at approximately 4 ppm.

- Deoiler injected in the produced water prior to O/B discharge at approximately 4 ppm.

TORR Perfor mance - Fixed Platform

120

558610

23 1

350

220276

68

110

232

150 152

226212280 295

380297275 290 276 26 5 280

22 023 8270 245

592470

410

265

4.5

7

56.5

5 5 5.57

67

1012

15

2023

2630

38

21 2326

22 2428

2520

1620

2822

26

67757770

3024

53

74

32

50

76

1412

87

89

77

141211

172

5.5

1

10

100

1000

0 50 100 150 200 250 300 350

Total Flow Treated (m)

OIW

(mg/L)

Inlet Conc. (ppm)

Outlet Conc. (ppm)

Figure 6: Oil removal performance on board North Sea fixed drilling and production platform

The results demonstrated the technologys performance in terms of oil recovery and lowering the

PW oil concentrations to levels meeting the trial target of 15mg/Liter OIW or below. Department of Trade

and Industry (DTI) approved methods for oil-in-water analysis were conducted as a primary method for


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measuring the inlet and outlet oil concentrations from the technology. Results showed that the oil

concentration removal efficiency across the technologys process was maintained at levels around 95%.

Concluding Remarks

The technology merits serious consideration for applications of polishing produced water to meet and

exceed discharge regulations.

The technology is capable of coalescing and recovering oil from produced waters.

The technology demonstrates characteristics of handling upset hydrocarbon concentrations on the inlet

feed.

A clear understanding of oil-in-water measurement protocols utilized is necessary to derive a fair

conclusion on the performance results.

Documents

PW Society 16 Conference