## Re -use: Treatment Technologies Shale Gas Water Management Marcellus Initiative Pittsburgh, PA Dean Ritts, PE, CEM Principal Engineer ± USAC

Water WorleyParsons Houston, Texas, USAWater Management for Unconventional Gas 

## A Case Study of a Centralized Water Treatment 

## System X 

### 16,000 BBL Day system for Flowback and Produced Water X 

### Under Design and will be Located In Eagle Ford Play X 

### Availability of Water suitable for fracturing and the environmentally responsible disposal of wastewater is 

### critical for sustainable development X 

### Knowledge Transfer for MarcellusWater Management for Unconventional Gas 

### A Tale of Two Shale Gas Plays Marcellus and Eagle Ford X Marcellus ± Pennsylvania, USA x Water is generally available for hydraulic fracturing x Disposal is the challenge as out-of ± state disposal options become more costly. x Increasing interest in Water Re-useWater Management for Unconventional Gas 

### Eagle Ford Shale, South Texas

x South Texas and West Texas are experiencing severe drought x Water is usually sourced from aquifers, typically the Carrizo and Gulf Coast x Carrizo and Gulf Coast aquifers are major water suppliers for ranching, municipal and industrial uses including fracturing x Wastewater disposal in injection wells is readily availableWater Management for Unconventional Gas 

## Management of Water Options X 

### Marcellus ± Challenge of Limited Disposal x Reuse flowback and produced water for fracturing x Deep well disposal in Ohio x Evaporation/crystallization to remove salts x Treatment for metals, oil and suspended solids and discharge to rivers X 

### Eagle Ford ± Challenge of Limited Water x Reuse flowback and produced water for Fracturing x Use brackish water from deeper aquifers (e.g. Wilcox) for fracturingWater Management for Unconventional Gas X 

### Hydraulic Fracturing (Gel) Fluids Contain x Water x Proppant (typically sand or silica beads) to hold fractures open x Salts, acids and caustics

í to prevent /minimize clay swelling (sodium and potassium chloride, acids and caustics for pH adjustment)

í to promote movement of water from the formation (methanol, surfactants)

í to limit chemical changes on the fracture face that reduce permeability x Ingredients help keep the proppant in suspension (guar gums for gel, surfactant for slick frac solutions) x Crosslink enhancer (metaborate) for guar gums x Biocides (borates, others) x Chemicals to degrade the guar gum gels (pH for borates, oxidizers)Water Management for Unconventional Gas 

### Flowback and Produced Water Treatment Goals for Eagle Ford Shale Plays 

### Treated water suitable for reuse as Fracturing water or for injection after well development is completed

 Low suspended solids and turbidity  Remove polymers (guar gum)  Remove free and emulsified oil  Remove Scale-Forming Metals  Salts are not an issue in this applicationwater is either reused for fracturing or injectedWater Management for Unconventional Gas 

### Flowback Water

 Flowback water is produced initially in very large volume and is typically stored in portable steel tanks at the wellhead.

 Flowback water is pumped to storage tanks or ponds and from there to treatment or disposal.Water Management for Unconventional Gas 

### Produced Water may be routed to a Centralized Processing Facility (CPF) for gas and condensate capture X 

### After Pressure Let-down to near Atmospheric 

### Pressure the Produced Water Contains:

x Residual dissolved gas x Trace amounts of oils (condensate), both free and emulsified x Sand (amount varies from field to field) x Polymeric gels (floating and dispersed in water, but less than in flowback) x Higher salt content than flowback water, higher amount of calcium and magnesium may cause scaling problemsWater Management for Unconventional GasWater Management for Unconventional Gas 

### Proposed Treatment ± General Issues x Natural gas dissolved in water / explosion hazard for produced wastewater x Variability of chemical composition of flowback water, from large quantity of highly viscous water (partially broken gel) on initial release, to more salty lower volume as gas appears in the water x 8VHRI3*UHHQ ́FKHPLFDOVIRU fracturing results in flowback and produced water with a high BOD (Biological Oxygen Demand) , readily degradable x Anaerobic degradation of wastewater, sulfate is converted to hydrogen sulfide rapidly x Generation of finely divided ferrous sulfide solids x US air emission rules apply to storage/treatment tanks x Disposal of removed solids as slurry or as dry cakeWater Management for Unconventional Gas 

## Treatment Operations X 

### Primary Separation (removal of gas, sand, oil and solids) x Three-phase separation (gas, oil, water and solids) is implemented at CPF after pressure let-down to release dissolved natural gas

í Some oil and most of the floating gel will pass through

í Not required for flowback water x Sand Separation

í Desanding Cyclone or Clarifier

í May be unnecessary for flowback Water if sand is allowed to settle and left in portable tanks x Clarifier

í Removal of floating gel and oil

í Small amounts of sand and suspended solidsWater Management for Unconventional Gas X 

### Equalization (for averaging chemical composition and varying flow)

í Could be first treatment stage Ƈ Sand would be difficult to remove Ƈ Mixing is limited if oil and gel are to be removed Ƈ May be difficult to remove gel and oil with an overflow weir or other passive removal system.

í Mixing option Ƈ Better averaging of variable influent stream Ƈ Not feasible if gel is to be removed

í Capacity/retention time Ƈ Select based on variability of flow and chemical composition

í Some sand will accumulate Ƈ Periodic manual removal requiredWater Management for Unconventional Gas X 

### Secondary Separation x Dissolved Air or Gas Flotation

í Coagulant addition (iron or aluminum salts) and polymer

í Flotation and removal of polymers, oils, suspended solids in floating foam

í Very flexible system for removal of a wide variety of contaminantsWater Management for Unconventional Gas X 

### Polishing and Storage x Filtration

í Solids and oil polishing x Treated Water Storage (Pond or Tank)

í Consider exposure of domestic and wild animals to water if stored in ponds

í Bactericide addition to control bacterial growth x Cartridge Filtration (at injection well)

í Not required for Fracturing X 

### Sludge Management x Additional dewatering for collected solids x Possibly break gels by pH adjustment or oxidant x Ship off-site as slurry or as dried cakeWater Management for Unconventional Gas 

### Air Pollution Control Issues
x Treatment under Gas Blanket

í Gas supplied by degassing from produced water and from CPF

í Gas returned to CPF

í Can be applied to all tanks and process vessels

í Limits access to process vessels by operator

í Repairs are more difficult x Treatment in Open Vessels or Closed with Sweep Air

í Sweep air to air pollution control device

í Requires air pollution controls for sweep air and ductwork to convey

í Open top clarifier and DAF allow easier operator inspection and intervention x Permitting and Emissions EstimationWater Management for Unconventional Gas 

### Treatment under Reduced or Oxidized Conditions X 

### Choice depends on local conditions and preference x Reduced

í Typical for produced water from oil fields

í Water is reducing upon injection; flowback and produced water is reducing

í Reduced water is less corrosive than oxidized water

í Ferrous sulfide particulate may be produced and is difficult to remove from suspension due to small size

í Anaerobic sludge will be produced in the storage tanks and ponds due to high biodegradability and high organic content, particulate may require removal from water stream

í A substantial amount of hydrogen sulfide may be produced from the sulfate in the wastewaterWater Management for Unconventional Gas 

### Treatment under Reduced or Oxidized Conditions X 

### Choice depends on local conditions and preference x Oxidized

í Add an oxidant such as bleach, hydrogen peroxide

í Due to large quantity of degradable BOD, degradation will continue unless some excess chlorine is maintained or a biocide is added

í Need several addition points to maintain excess oxidant

í Use substantial quantity of oxidant

í Solution is more corrosive when oxidized

í Larger quantity of some metals are removed, e.g. iron

í May implement open top reaction vessels, especially the DAF

í Simpler to add air in flotation process than gas in a DGFWater Management for Unconventional Gas X 

### Lessons Learned ± Gel Frac Solutions are Different x Sand and Gel should be removed before equalization x Removal of oil is not as critical as with produced water and will be removed with gel x Gel will plug v-notch weirs; utilize other designs x *HO3KDQJVXS ́XVHSRVLWLYHGLVSODFHPHQWGHYLFHWRLQVXUH removal x A floating sludge, a sinking sludge and sand are produced; if mixed, thickening (removal of water) may be difficult x Difficult to separate and concentrate mixed sludges from water (floating/gel, DAF foam and settling sludges) x The most significant difference between produced and flowback water is the huge range of flows and rapid changes in chemical characteristics of flowback water compared with produced water x Oil and Gas workers are relatively inexperienced with water treatment

## SUMMARY X 

### Shale Gas and Oil Field Development Has Challenges 

## x Water Resources x Wastewater Treatment/Disposal 

## x Environmental Compliance x Public Perception X 

### Water Re-use is a Sustainable Engineering Approach to Meet the Challenge

20 21 - Mar - 12 Water Management for Unconventional GasWater Management for Unconventional Gas

21 21 - Mar - 12 

# Thank You Dean Ritts, PE, CEM dean.ritts@worleyparsons.com