Frac Water Reuse Technologies
From Frac Water Equipment
Over the last ten years, the US energy sector has accelerated the development of its unconventional oil and gas resources through increased use of horizontal drilling and hydraulic fracturing practices. Water is an essential element in the fracturing process. The volume of water required to fracture a well varies across the country, but it generally ranges from one million gallons to five million gallons. Operators face difficult challenges securing water sources for their operations, especially in the arid west. Furthermore, the management of waste water associated with hydraulic fracturing has an environmental impact and associated cost. The development of technology to recycle and reuse this water is now becoming critical and Anguil Aqua has integrated solutions to help.
Water generated during drilling, well completion, and production is categorized either as flowback or produced water. Flowback water is the initial fluid produced after hydraulic fracturing and is typically recovered during the first six weeks of well production. The flowback water characteristics stem from the initial source water, the natural formation brine, fracturing fluid additives, proppants, and drilling fluids. Generally, 20-40% of the fracturing fluid volume is recovered as flowback. Produced water is the water which naturally exists within shale formation and is recovered concurrently with oil and gas. After the initial flowback period, produced water resembles the characteristics of the formation brine. The volume recovery rate of produced water is lower in comparison to the flowback, but occurs over the decades of a well's lifetime. Currently, the majority of flowback and produced water is disposed of in salt water disposal wells.
Recycling and reuse of flowback and/or produced water reduces fresh water demand and the associated costs of water purchase, transportation, and disposal. In contrast to the usual practice of complete disposal, a portion of the flowback is treated for reuse either onsite or at an adjacent well. The primary economic benefit from recycling is a significant reduction in the number of truck loads required to ship fresh water to the well site and the flowback water offsite. Environmental benefits include reduced reliance on and competition for fresh water sources, a reduced carbon footprint from trucking, and less stress on the local infrastructure.
Treatment requirements for flowback and produced water are normally established by the company performing the well completion. Knowledge of the fracture fluid employed is required when considering the recycling methodology in order to identify the required treatment characteristics. Two common fracturing fluids are slick water and gels. Slickwater is normally used for natural gas production, whereas gels are often deployed for oil field development.
Anguil’s Frac Water Reuse System
Since there is a wide variation in flowback and produced water quality in oil and gas fields, Anguil Aqua Systems is presently focused on the treatment of flowback and/or produced water from natural gas wells.
Previously, the high levels of Total Dissolved Solids (TDS) in produced water were thought to render it unusable. However, well service companies have demonstrated that moderate TDS levels in recycled water do not impact well production capacity. Hence our solution is to focus on the minimization of Total Suspended Solids (TSS) and, overall reduction of bacteria and other contaminants affecting the fracturing fluid additives.
Of the many approaches to the minimization of TSS, the Anguil solution is a ballasted flocculation system. Similar systems have been successfully employed to treat drinking water as well as municipal and industrial waste waters containing many of the same contaminants found in flowback and produced waters.
The diagram below depicts the flow pattern for the clarification process. In the first tank, the raw water or influent is combined with a coagulant, commonly ferrous sulfate, ferric sulfate, ferric chloride, or alum. The coagulated influent then passes into the flocculation tank where a polymer and a ballast material such as microsand, iron oxides, or chemically enhanced sludge is added. Coagulation and sedimentation times are reduced by the addition of chemical additives and the ballast material. After ballast and polymer additions, the flocculated water then proceeds to the third tank where additional mixing occurs, allowing the floc to coalesce into larger precipitates. The matured, flocculated water proceeds to the clarification tank where the floc is separated from the water by passing through plate or tube settlers. Clarified water then exits from the top of the system.
Settled floc and ballast material are collected and pumped to the ballast recovery unit where the ballast is separated from the waste solids. The waste solids are sent to disposal and the recovered ballast is returned to the first flocculation tank.
- Reuse of Flowback and Produced Water: Physical and chemical treatment system that reduces suspended solids to acceptable reuse standards for hydraulic fracturing.
- Mobile Precipitation: A system easily deployed on site, allowing treatment for multi-well completions, or transport to a nearby well.
- High Contaminant Removal: Total Suspended Solids (TSS), turbidity, oil/grease, color, and bacteria.
- Chemical Coagulation: A wide range of available coagulants and polymers allows customization to site specific needs.
- Automated Chemical Feed System: Treatment begins with proper dosing of chemicals to precipitate dissolved contaminants. The Frac Water Reuse System incorporates chemical metering pumps, day tanks and pH instrumentation to ensure treatment objectives are being achieved.
- Lower Costs: Ballasted clarification allows for smaller equipment footprint, reduced power consumption, and reasonable chemical use. Recovery and reuse of ballast material lowers consumable costs.
- Short Term Lease Agreements: Flexibility to only pay for water recycling system during peak water demand.
- Customized Service and Project Management Contracts: Anguil personnel can be contracted to provide continuous service and/or operation of the entire water recycling system.