DE-FE0000975

Goal
The goal is to develop a sustainable approach for water management in the Marcellus Shale play, in which flowback water is economically treated on site and re-used for hydrofracturing adjacent wells. Optimal treatment processes will be identified, and acid mine drainage (AMD) water will be examined as a potential supplement to flowback water used for hydrofracturing. Novel viscosity modifiers that are stable under the high salinities observed in Marcellus shale flowback water will also be developed.

Performers
University of Pittsburgh, Pittsburgh, PA 15260
Carnegie Mellon University, Pittsburgh, PA 15213

Background
Hydraulic fracturing has enabled the economical recovery of natural gas from the Marcellus shale. The fracturing fluids used in development of the Marcellus consist mostly of freshwater withdrawn from local streams and amended with chemical additives. A single well hydrofracture in the Marcellus may require one to five million gallons of fracturing fluid, of which between 25 and 100% may be returned to the surface as "flowback" or "produced" water which must then be disposed. In addition to chemical additives, flowback water from Marcellus hydrofracturing typically contains high levels of total dissolved solids (TDS) (ranging from 70,000 to 250,000 mg/L) hydrocarbons, and heavy metals. The presence of these constituents precludes untreated re-use, reinjection, or direct discharge onto land or into receiving streams, as they may adversely impact human health and environmental quality. The flowback water is not amenable to reinjection due to high concentrations of barium and strontium and the potential for calcite precipitation in the injection well.

Conventional treatment processes, such as reverse osmosis and distillation, are not likely to be utilized due to their high capital costs and energy requirements. Disposal by dilution into Publically Owned Treatment Works (POTW), the common method to date for handling Marcellus flowback water in Pennsylvania, is not sustainable either, as transportation costs are extremely high, and POTWs are limited as to how much water they can accept and treat. In response to high TDS levels measured in the Monongahela River in the fall of 2008, the Pennsylvania Department of Environmental Protection ordered a restriction on the amount of produced water (including flowback) disposal to POTWs in the basin. This restriction effectively halted gas drilling operations in some locations in western Pennsylvania and has limited disposal options for expanding shale gas production.

Preserving the favorable economics of gas development in the Marcellus play and maintaining responsible stewardship of the environment are the two drivers of future water management strategies in the Marcellus. This research provides a holistic approach to water management through re-use of flowback water and use of supplemental AMD water for subsequent hydrofracturing operations. The location, quantity, and quality of flowback and AMD waters will be evaluated and their chemical interactions will be examined in order to identify optimal treatment processes. A field demonstration of the treatment process will be conducted and key technical and cost parameters for field demonstration of a hydrofracturing operation using the mixture of flowback and AMD waters will be assessed.

Impact
The Marcellus shale represents one of the largest reserves of on-shore natural gas in the country. However, development of this resource will be limited by the high volumes of difficult-to-treat wastewater produced during well development. By providing technically and economically feasible approaches for the re-use of flowback water, this project will effectively reduce the amount of freshwater needed for Marcellus Shale development and minimize the disposal liability and costs associated with new well drilling. The use of locally available AMD as make-up water will also reduce the amount of freshwater use as well as the transportation costs associated with bringing make-up water to the project site.

Accomplishments
The AMD database has been updated to include flow rates and chemical analyses over a period of time for 242 sites, so the variability in flow and contaminant levels can be taken into account. Users will be able to search for AMD sites based on desired flow rates, chemical analyses and location with search results being displayed on a map.

Ceramic microfiltration experiments of a mix flowback water and AMD were performed to determine sustainable operating conditions. Even under low transmembrane pressure and medium-high cross flow velocity, the membrane performance in terms of permeate flux is very poor. The membrane is rapidly fouled. Neither barite, nor calcite crystals that formed during the mixing of the AMD and flowback water, are responsible for the fouling. Organic matter present in the flowback appears to be the main fouling agent.

Three chemical equilibrium models have been used to determine the results of mixing simulated flowback water with solutions of sodium sulfate and sodium bicarbonate. These experiments will outline which metals can be removed from flowback water when mixed with AMD.

Site visits continue in order to select potential locations for field experiments involving flowback and AMD water. Researchers have established working relationships with major natural gas developers, well drilling and hydrofracturing companies, the Pennsylvania Department of Environmental Protection (PADEP), water treatment companies, and watershed groups interested in the outcome of this project.

Flowback water locations and AMD sites in Pennsylvania have been catalogued with assistance from the Appalachian Shale Water Conservation and Management Committee and the PADEP. To date, analyses of 160 samples of flowback water have been entered into their database. The average TDS is 106,000 mg/L (range of 680?345,000 mg/L) with a strong correlation between Cl and TDS concentrations. Water quality analyses on 140 AMD sites have been gathered. AMD flow rates, proximity to gas wells, and levels of sulfate and other constituents are being considered for use of AMD for flowback water treatment. Based on their chemistry, the collected AMD samples appear compatible for mixing with flowback water and re-use as fracturing fluid.

A Project Advisory Committee (PAC) consisting of seven industry partners and government agencies has been formed to help determine the most advantageous solution to the problem of produced water treatment and disposal in Pennsylvania. A presentation on the purpose and first results of the project led to a discussion on the benefits and limitations of the proposed management options. Objectives were redefined in accordance with advice from our industry partners. In particular, one of the most important project issues is to define a set of water quality parameters for water used in hydraulic fracturing.

Current Status (May 2012)
Researchers are working with the University of Pittsburgh Law School to investigate the Pennsylvania regulations regarding AMD usage and liabilities. Testing of various filtration methods and precipitation analysis continues in lab tests on simulated flowback water and AMD mixtures. An ultra-filtration system provided by a research partner will be used in lab tests. The system is similar to one that will be used to conduct the field tests. Membrane fouling is being investigated and pre-treatment options are being outlined.

Project Start: October 1, 2009
Project End: December 31, 2013

DOE Contribution: $794,226
Performer Contribution: $284,010

Contact Information:
NETL - Sandy McSurdy (sandra.mcsurdy@netl.doe.gov or 412-386-4533)
University of Pittsburgh - Dr Radisav Vidic (vidic@pitt.edu or 412-624-1307)
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