The objective of the project is to develop an on-site multi-media filtration system. The five-stage modular design will permit efficient system operation and treatment of flowback water at conditions that vary over time.
West Virginia University
Shale gas development in the Marcellus gas play in the northern Appalachian Basin requires large volumes of water to fracture the formation and stimulate production. Known as “frac return water”, it and produced water are highly saline and currently require either disposal or treatment. Both options are expensive. Produced water that cannot be readily treated for local disposal (e.g., land application) could be hauled to an injection well for disposal. These are EPA Class II wells permitted under the federal Safe Drinking Water Act and are carefully controlled and monitored. Disposal costs are well established. In Texas, haulage and disposal costs average $1.47 per barrel. In the more populated East, the costs range from $1.68 to $2.10 per barrel. As an alternative to deep well disposal, produced water has been processed at municipal or commercial treatment plants (especially in Pennsylvania) but this practice is being re-evaluated. While this treatment removes some contaminants, it does not address salinity and throughput is limited by plant limitations and the ability to dilute the effluent to meet water quality standards. This is a costly alternative that will be less likely to be used in the future as small towns and cities find that their standard treatment is inadequate and that they lack the necessary existing capacity.
The more cost-effective alternative is on-site treatment of the produced water to the degree needed for re-use as frac water. Produced water has been successfully treated using Reverse Osmosis (RO) as the primary treatment technology. However, extension of the RO technology to the treatment of flow back from hydraulic fracture operations has required pre-treatment technologies designed to extend the life of the RO unit. RO protection is especially important during the initial frac water return period when it will have the maximum suspended solids and minimum dissolved solids.
Re-use technologies are just now being implemented, and as reported in a recent overview (GWPC, April 2009): “Current levels of interest in recycling and reuse are high, but new approaches and more efficient technologies are needed to make treatment and re-use a wide-spread reality.” The FilterSure multi-media filter technology offers a new, cost-effective approach ideally suited for removing suspended solids associated with frac return water while promising an order of magnitude improvement in operating efficiency. The filter is expected to replace all of the pre-treatment steps now being examined under the DOE contract, dramatically reducing the costs and enhancing the attractiveness of water re-use.
The successful development of an advanced FilterSure technology for clean-up and re-use of frac return water will advance shale gas exploitation and development through improved economics and resolution of environmental issues. Improved economics will be achieved by the reduction of frac return water trucking and disposal costs. By reusing the frac return water for subsequent fractures, the need for new, fresh frac water for future wells will be reduced by 30% to 50% depending on the percentage of injected water that is returned after the frac. There will be an additional cost savings due to reduced freshwater hauling and labor costs will be minimized because the mobile unit will operate continuously with little or no need for an attendant. Significant environmental benefits will be derived from this technology as well. Less fresh water will be needed for future fractures, thus lowering the demand stress on local streams. Fewer trips with water trucks will cause less damage to local roads, reduce fugitive dust and engine exhaust emissions, and reduce mud and muddy water which potentially could pollute streams. These derived environmental benefits will also provide indirect economic benefits through reduced cost of road repairs, and less need for local stream remediation. Perhaps the most important benefit from cleaner and less disruptive drilling will be the “good will” of all stakeholders affected by the shale gas development process.
FilterSure installed the Mobile Treatment Unit (MTU) and conducted a field test at a Marcellus Shale well site. The MTU successfully supported a nine (9)-stage fracture treatment. The average filtration rate during fracture operations was 104 GPM with an inlet pressure of 52 PSIG. The MTU removed 32% of the solids, a result similar to that achieved in controlled laboratory tests at West Virginia University. During the test the MTU processed 280,000 gallons of produced water. Of the total volume of water sent to the MTU, 98.6% was recycled with only 1.4% sent for disposal.
A “shakedown” test of the MTU was conducted in the field. The MTU filtered 200,000 gallons of frac return water at a maximum rate of 120 gallons per minute (GPM).
Development of the MTU has been completed and the unit is ready for field testing.
The design phase of the 150 GPM unit has been completed. Testing of a 6 GPM MTU in the laboratory has shown that 150 GPM throughput can be reached for the upcoming field test.
Preliminary laboratory results from a recent scale test show that the 150 GPM unit is feasible.
The Design of the 30 gallon per minute (GPM) Mobile Treatment Unit (MTU) has been completed. WVU has requested to change the MTU design to a 150 GPM throughput unit for use during field testing.
During a recent laboratory test using actual frac return water from a site similar to the upcoming test site, WVU concluded that the new filter unit captured particulate at and greater than 3 microns. Current industry requests are equal to or greater than 20 microns, showing that even at the high throughput the filter unit exceeds current industry needs.
No Naturally Occurring Radioactive Materials (NORMs), have been found in any of the field samples of frac return water received to-date. Any heavy metals will be removed via insoluble complexes for safe disposal.
Heavy metals and radioactive elements/compounds, if any, were contained in the EC-mobilized solids removed by filtration and managed as a part of the commercial process. Tests on the filter backwash waters following treatment of each sample showed “non-detect” levels for As, Cd, Cr, Pb, Se, Ag, and Hg. Barium was detected in amounts ranging from 1.61 to 5.33 mg/l, well below the MCL of 100 mg/l set for Ba.
One 20-gallon sample of Marcellus frac return water was shipped to a provider of Electrical Coagulation (EC) technology for testing as a potential pre-treatment option. The EC-treated water was returned to WVU for evaluation. The results show that the EC technology had a major impact on the distribution of the solids. Specifically, the EC technology caused the distribution of solids to shift from a few microns in size to larger solids having a single bell-shaped distribution.
Three applications of the FilterSure PDU on Marcellus Shale frac return water reduced the suspended solids by 76%, removing all suspended solids greater than 3 microns in size, a good result when compared to the most strict industry requirement of 5 microns. Other industry operators report a 5 to 10 micron requirement or standard sand filtration with no absolute size requirement.
Results of economic analyses indicate that the plausible system resulting from this project will be very cost competitive with any other system for achieving the ultimate objective of zero-discharge of frac return water. Preliminary estimates place the cost at $0.80 to $1.22/barrel.
Suspended solids in the EC treated water were easily removed with the FilterSure technology resulting in an effluent that was visually clear without particulates. The combination EC and FilterSure PDU treatment system removed 99.4% of all particles.
Electrical Coagulation (EC) shifted the distribution of the suspended particles, creating larger size particles compared with the raw water sample.
Industry Contact Group members have provided five flowback frac water samples. The WVU Radiation Safety Department tested all samples for radioactivity and found all to be at or below background values. WVU analyzed particle size distribution for all frac return water samples. A commercial laboratory and WVU measured the water chemistry of all samples. Tests of Marcellus water samples showed the FilterSure process development unit (PDU) removed 100% of the frac water suspended solids larger than three microns and 40% of particles larger than 1.5 microns.
Responses to a questionnaire developed for this project are providing engineering information on volumes of flowback water and water chemistry requirements for recycling of flowback water.
An Industry Contact Group was created to obtain representative water flowback samples and information on operating parameters.
The project has ended and the final report is available below under "Additional Information"