Lee Shafer

Basin Engineering

October 26, 2017

Why recycle?

Reduce water consumption and disposal volume

Reduce overall water life cycle costs

Potential improvement in compatibility with formation

Potential improvement in total fracturing fluid cost

Water – range of 0 to 100% recycled

Friction Reducer (FR) or linear gel with or without a cross linking additive; may require buffers to control pH for optimal performance

Biocide – chemical agents or mechanical methods used to control the “undesirables”

Enhancing production/minimizing damage:

Scale inhibitor

Clay stabilizers, organic and inorganic

Surfactants/non-emulsifiers

Spearhead acid pumped in the front end of the stage to help establish fracturing rate:

o Commonly 15% HCl with organic acid inhibitors to protect the steel

o Iron control agents for iron that is dissolved from the rock

o Non emulsifier to avoid creating acid/hydrocarbon emulsions

Corrosion inhibitors

Hydrogen Sulfide (H2S) scavengers

Surface tension modifying materials to aid in water recovery

Remove residual free oil

Mitigate hydrogen sulfide

Oxidation:

Chemical – bleach, chlorine dioxide, peroxide, etc

Air – lower cost, but slower than chemical

In-situ generation of peroxides etc.

Suspended solids reduction

Direct filtration and/or coagulation and flocculation

Clarify in pits

Remove iron and other metals that can interfere with fracturing system performance

Control undesirable biologic growth in storage

Test to confirm fracturing fluid and formation compatibility when re-using the water

Oil Separation to <30 mg/l Oil & Grease

Divert pit with skimming facility & submerged aeration

Treatment pond sized for 15 days average flow with

aeration sized for COD reduction to <1000 mg/l outlet

Storage pond(s) with submerged aeration sized

to polish COD to <500 mg/l during storage

Process Feed Treated water

Oil and Grease by HEM (O&G), mg/l >1000 <5

Total Dissolved Solids (TDS), mg/l 10,000 - 100,000 10,000 - 100,000

pH 5 to 10 6.5 to 8.5

Total Suspended Solids (TSS), mg/l >500 <100

Total Iron, mg/l >100 <10

Chemical Oxygen Demand (COD), mg/l >2500 <800

Dissolved Oxygen (DO), mg/l <2 5 - 8

Oxidation Reduction Potential (ORP), mV -300 +250

Sulfate Reducing Bacteria (SRB), CFU/ml >10^6 <10

Acid Producing Bacteria (APB), CFU/ml >10^6 <10