Workshop 4, Theme 2, Session 3

A Water Chemistry Perspective on 

Flowback Reuse with Several Case 

Studies

30 March 2011

Keith Minnich, Water Sustainability Advisor
2

Frac Flowback Reuse/Disposal – Early Shale Work

In the beginning, near fresh quality water was the standard 

for frac fluid preparation and flowback was disposed in deep wells. Deep 

well disposal is widely practiced. Approximately 3 billion cubic meters are 

injected in the USA annually from conventional energy production.

Injection Well and Tank Battery at 

Commercial Disposal Facility in Texas

from DOE Award DOE Award No.: FWP 49462 – Argonne Labs

• Source water not a 

constraint and frac 

makeup was typically 

fresh water

• Some believed at the 

time that near fresh 

quality water was 

necessary for the frac 

ingredients to perform as 

intended

• Deepwell disposal was 

available for flowback. 

Frac flowback injection is 

small fraction of the total. 
3

Frac Flowback Reuse/Disposal – Dealing with Constraints

Disposal constraints in new plays provided the motivation to reuse flowback by 

treating it to near fresh quality by removing dissolved solids (TDS)

• High Total Dissolved 

Solids (TDS) flowback 

water and the presence 

of organics present 

treatment challenges

• Very difficult 

application for Reverse 

Osmosis due to 

organics and clay

• Only proven option is 

evaporation technology

Range of Flowback TDS
4

Frac Flowback Reuse/Disposal – Dealing with Constraints

Application of water treatment 

technologies to create near fresh quality 

water from flowback

• Creating near fresh 

quality is feasible

• High capital and 

operating costs

• Evaporation does 

not allow 100% 

reuse of flow back

Pre-treatment

Evaporation Plant

Fountain Quail, Texas 
5

Frac Flowback Reuse/Disposal – Optimizing Constraints

Experience and testing shows that 

near fresh quality water is not always 

a requirement for fracking

• Options exist for saline tolerant 

chemical additives

• 100% Reuse has been 

demonstrated and practiced

Fountain Quail, Texas 

Friction Reducer Source: Schlumberger Water Services 

Good Enough for Fracking in 

some Cases
6

Two Perceived Obstacles to Flowback Reuse are 

Suspended Solids and Scaling Constituents

• Case Study 1; Removing Suspended Solids from Flowback,

Is Filtration Necessary ?

• Case Study 2; Managing Metals and Hardness

• Logistics of Transporting and Storing Flowback

− Any discussion on reuse must emphasize the differences between the 

North American (Western Canada, Eastern Canada, Eastern USA, and 

Southern USA) shale gas formations and the differences between 

different locations in the same formation. Reuse decisions and logistics 

will be site specific.
7

Data Collection to Support Reuse Water Management –

Case Study 1; Removing Suspended Solids from Flowback

Is Filtration Necessary ?

Filtration Recommended 

by Water Treatment 

Companies

Stokes Law Analysis 

Indicates Filter Not 

Necessary
8

Case Study 1; Flowback Filtration Necessary or Not?

Particle Size Distribution after Settling in Flowback Storage

Suspended Solids Profile after Surge Tanks

Total Suspended Solids ~ 1,500 mg/l
9

Case Study 1; Flowback Filtration Necessary or Not?

Particle Size Distribution after Settling in Flowback Storage

Suspended Solids Profile after Holding Tanks

Total Suspended Solids ~ 100 mg/l
10

Case Study 1; Flowback Filtration Necessary or Not?

Particle Size Distribution after Settling in Flowback Storage

Before After

0-10 728 75 -90%

10-25 442 22 -95%

25-100 346 17 -95%

>100 8 0 -100%

TOTAL 1523 113 -93%

Percent 

Removal

Particle Size 

Range,

microns

Concentration 

at Holding Tanks, mg/l
11

Case Study 1; Flowback Filtration Necessary or Not?

Particle Composition after Settling in Flowback Storage

XRD Analysis shows Suspended Solids after 

settling consist primarily of Barite
12

Case Study 1; Scheme for Removing Suspended Solids

Surge Tanks 

Arranged in 

Parallel

Surge Tanks 

Arrange in 

Parallel

Inlet and 

Outlet at 

Opposite 

Ends

Arrangement of 

Surge and Storage 

Tanks to Achieve

< 50 mg/l of 

SS > 30 microns
13

Case Study 1 Summary; Removing Suspended Solids from Flowback

• Attempts to filter flowback resulted in filter blockage with fines, creating 

an obstacle to reuse of flowback.

• Settling in surge and storage tanks reduces suspended solids to < 50 

mg/l of particles with a size range of 30 microns to 100 microns.

• The amount of suspended in the flowback has not had any noticeable 

impact on well performance. No long term studies have been made.

• Talisman has not observed biomass suspended solids which do not 

settle.

• Settled solids are removed from tanks by vacuum trucks and disposed in 

licensed landfills.
14

Case Study 2; Managing Metals and Hardness for Scale Control

Ionic 

balance 

shows 

closure 

within 8.5%, 

which is 

acceptable

Anions Cations

Constituent Units Concentration

Alkalinity as CaCO3 mg/L CACO3 253.9 5.1

Bromide mg/L 901.9 11.3

Chloride mg/L 105,338.7 2,971.5

Hardness as CaCO3 mg/L CACO3 48,092.2

Ammonia Nitrogen mg/L 89.9 5.0

pH STD Units 6.4

TDS @ 180 C mg/L 193,106.0

Total Suspended Solids mg/L 1,822.4

Sulfate mg/L 50.0 1.0

Aluminum, Total mg/L 13.0 1.4

Barium, Total mg/L 9,082.7 132.3

Calcium, Total mg/L 12,632.7 631.6

Iron, Total mg/L 185.0

Iron, Dissolved mg/L 186.3 10.0

Lithium, Total mg/L 633.9 91.3

Magnesium, Total mg/L 1,185.0 97.5

Sodium, Total mg/L 39,080.9 1,699.9

Strontium, Total mg/L 3,715.6 84.8

2,988.9 2,753.9

Shale Flowback Water Analysis

Equivalents
15

Case Study 2; Managing Metals and Hardness for Scale Control

Ions of Concern for Scaling

Low concentrations of 

scale forming anions

Very high 

concentrations of 

scale forming cations

Enough iron to have a 

concern Constituent Units Concentration

Alkalinity as CaCO3 mg/L CACO3 253.9

Bromide mg/L 901.9

Chloride mg/L 105,338.7

Hardness as CaCO3 mg/L CACO3 48,092.2

Ammonia Nitrogen mg/L 89.9

pH STD Units 6.4

TDS @ 180 C mg/L 193,106.0

Total Suspended Solids mg/L 1,822.4

Sulfate mg/L 50.0

Aluminum, Total mg/L 13.0

Barium, Total mg/L 9,082.7

Calcium, Total mg/L 12,632.7

Iron, Total mg/L 185.0

Iron, Dissolved mg/L 186.3

Lithium, Total mg/L 633.9

Magnesium, Total mg/L 1,185.0

Sodium, Total mg/L 39,080.9

Strontium, Total mg/L 3,715.6

Shale Flowback Water Analysis
16

Case Study 2; Managing Metals and Hardness for Scale Control

Potential Scaling Compounds

BaSO4 is at its 

saturation concentration 

with large amounts of 

excess Ba to precipitate 

with SO4 from fresh 

blend makeup or 

formation water

There is some potential 

for CaCO3 or SrCO3 

precipitation with large 

amounts of excess Ca 

and Sr

There is some potential for 

ferrous carbonate or other 

iron scale precipitation Compound Chloride

CaHCO3 411

BaSO4 122

BaCl2 from Ba 13,663 4,652

CaCl2 from Ca 34,743 22,211

MgCl2 from Mg 4,641 3,456

SrCl2 from Sr 5,219 2,334

LiCl from Li 3,872 3,238

AlCl3 from Al 64 51

NH4Cl from NH4 267 177

FeCl2 from Fe 423 185

NaBr from Br 1,161

NaCl from Cl 113,803 69,033

Sum of Cl Salts 176,695 105,339

Sum of All Salts 178,389

Measured TDS 193,106

Concentration, mg/l Compound
17

Case Study 2; Managing Metals and Hardness for Scale Control 

Ionic Strength Increases BaSO4 Solubility, but not to a 

Significant Degree Compared to Ba Availability

Source: – Solubility of Barium Sulfate in Sodium Chloride Solutions from 25 C to 90 C, 

Charles Templeton, Journal of Chemical and Engineering Data, October 1960
18

Case Study 2; Managing Metals and Hardness for Scale Control

Typical Recommendations for Scale Control and Alternative

• Scaling Potential 

− BaSO4 is at saturation point with large amounts of excess Ba

− Large amounts of excess Ca and Sr are present to drive CaCO3 or 

SrCO3 precipitation

− Soluble iron is present to form FeCO3 precipitate

− SO4 and alkalinity from fresh makeup increase potential for precipitation

• The traditional recommended approach is to remove Ba, Sr, Ca and 

Mg from flowback using Na2SO4 and Na2CO3 and CaO which 

requires large amounts of chemicals and also trucking:

− 1.5 tons of Na2SO4 for every 500 bbl of flowback

− 3.5 tons of NaCO3 for every 500 bbl of flowback

− Trucking chemicals and flowback to and from treatment facility

− Solids generated by treatment must be landfilled
19

Case Study 2; Managing Metals and Hardness for Scale Control

Typical Recommendations for Scale Control and Alternative

• Alternative is to take advantage of formation water chemistry in above 

ground blending of flow flowback and source water to reduce scaling 

potential

− The constituents in flowback will react with the constituents in source 

water to reduce the scaling potential of the blend
20

Case Study 2; Managing Metals and Hardness for Scale Control

Using Natural Barite Seed Crystals for Scale Control

Source: – Solubility of Barium Sulfate in Sodium Chloride Solutions from 25 C to 90 C, 

Charles Templeton, Journal of Chemical and Engineering Data, October 1960

625 mg/l of barite 

de-supersaturates 

Flowback after 

settling has 250 mg/l 

of primarily barite 

SS

Co-precipitation of 

scaling salts is 

known from other 

applications – this 

has not been 

studied for flowback
21

Case Study 2; Managing Metals and Hardness for Scale Control

Typical Chemistry after Blending Flowback and Fresh Water

• Talisman has reused 

flowback with only 

settling 

• No chemical addition 

for precipitating metals 

and hardness

• Blend TDS of 

approximately 50,000 

mg/l

• No apparent negative 

impact on the formation 

or gas production

Constituent Units Concentration

Alkalinity as CaCO3 mg/L CACO3 250.0

Bromide mg/L 180.4

Chloride mg/L 21,067.7

Hardness as CaCO3 mg/L CACO3 9,618.4

Ammonia Nitrogen mg/L 18.0

pH STD Units 6.4

TDS @ 180 C mg/L 38,621.2

Total Suspended Solids mg/L 364.5

Sulfate mg/L 90.0

Aluminum, Total mg/L 2.6

Barium, Total mg/L 1,816.5

Calcium, Total mg/L 2,566.5

Iron, Total mg/L 37.0

Iron, Dissolved mg/L 37.3

Lithium, Total mg/L 126.8

Magnesium, Total mg/L 237.0

Sodium, Total mg/L 7,816.2

Strontium, Total mg/L 743.1

Shale Flowback and Fresh Water Blend
22

Case Study 2 Summary; 

Managing Metals and Hardness for Scale Control

Blending of Flowback and Fresh Water for Scale Control

• Talisman has reused flowback with only settling, and no chemical addition for 

metals and hardness reduction, for blend TDS of approximately 50,000 mg/l

• Why might blending of flowback and fresh water reduce scaling potential?

− Iron is likely oxidized and precipitated as Fe(OH)3 in surface tanks

− Reduction in ionic strength reduces BaSO4 solubility by 50%. SO4 from surface 

water reacts with excess Ba and likely precipitates on seeds

− Some CaCO3 and SrCO3 precipitation will occur. However, at this time scale 

control is indicated because of inverse solubility with respect to temperature and 

lack of definite information on co-precipitation

• What about formation compatibility?

− The presence of barite “seeds” should reduce down hole and formation scaling 

due to preferential precipitation on the seeds

− Caution is recommended for formations with soluble sulfate. However, barite 

“seeds” might be useful in such situations

− In principle, fewer salts should be solubilized from the formation with higher TDS 

frac fluid

− The impact of increased frac fluid density has not been investigated
23

Importance of Logistics for Managing Flowback Reuse

• Number of wells per pad – Flowback reuse on Multi-Well pads 

reduces movement of flowback off the pad

• Timing - storage required to deal with when flowback is available and 

when it is required 

• Variations in the amount of flowback. The range is 10% to 50% of the 

injected frac fluid

• Location of fresh makeup

• Contiguousness of leases

The logistics of transporting and handling flowback to minimize 

environmental and public health risks must take the following into 

consideration:
24

Flowback Logistics – Multi-Well Pads Reduce Truck Traffic 

when Flowback is Reused

Multi-Well Pads

(6 to 24 per pad) 

Source: Statoil

Reuse of flowback significantly 

reduces the amount of flowback 

removed from the pad versus no 

reuse of flowback
25

Flowback Logistics for < 20% Flowback

Flowback 

Storage

Portable 

tanks are 

suitable for 

smaller 

volumes of 

flowback
26

Flowback Storage for > 40% Flowback

Source Water

Flowback 

Storage

Portable tanks are 

less suitable for 

smaller volumes of 

flowback and field 

erected tanks are 

more practical
27

Logistics for Managing Flowback Reuse

Pipelines versus Trucks

• Trucks

− Justified when flowback volumes are small

− Truck traffic reduced substantially by multi-well pads

• Pipelines

− Justified when flowback volumes are large

− Reduces truck traffic

− More land disturbance than trucks

• There is no specific rule for one versus the other
28

Shale Gas Flowback Water Reuse Summary

• Water chemistry considerations indicated that flowback does not 

require extensive treatment in all cases before it is reused

• Talisman Energy has successfully reused flowback with only settling 

of suspended solids for TDS of approximately 50,000 mg/l

• From a scale control perspective it might be advantageous not to 

remove metals and hardness before blending

− Takes advantage of the de-supersaturation capability of naturally 

occurring barite seed crystals. Co-precipitation of other scaling salts 

might be a benefit.

− The seed crystals might reduced down hole and formation scaling

• Reuse reduces truck traffic when disposal wells are not available

• Due to variations between locations, the flowback reuse and logistics 

issues are site specific