Flowback And Produced Waters

Produced waterâ€"water from underground formations that is brought to the surface during oil and gas productionâ€"is the greatest volume byproduct associated with oil and gas production. It is managed by some combination of underground injection, treatment and subsequent use, treatment and discharge, or evaporation, subject to compliance with state and federal regulations. Management of these waters is challenging not only for industry and regulators, but also for landowners and the public because of differences in the quality and quantity of produced water, varying infrastructure needs, costs, and environmental considerations associated with produced water disposal, storage, and transport. Unconventional oil and gas development involves technologies that combine horizontal drilling with the practice of hydraulic fracturing. Hydraulic fracturing is a controlled, high-pressure injection of fluid and proppant into a well to generate fractures in the rock formation containing the oil or gas. After the hydraulic fracture procedure is completed, the injected fluid is allowed to flow back into the well, leaving the proppant in the newly created fractures. As a result, a portion of the injected water returns to the surface and this water is called "flowback water" which initially may mix with the naturally occurring produced water from the formation. The chemistry and volume of water returning to the surface from unconventional oil and gas operations thus changes during the lifetime of the well due to the amount of fluid used in the initial stage of well development, the amount of water naturally occurring in the geologic formation, the original water and rock chemistry, the type of hydrocarbon being produced, and the way in which production is conducted. The volume and composition of flowback and produced waters vary with geography, time, and site-specific factors. A workshop was conducted by the National Academies of Sciences, Engineering, and Medicine to highlight the challenges and opportunities associated in managing produced water from unconventional hydrocarbon development, and particularly in the area of potential beneficial uses for these waters. This publication summarizes the presentations and discussions from the workshop.

Produced waterâ€"water from underground formations that is brought to the surface during oil and gas productionâ€"is the greatest volume byproduct associated with oil and gas production. It is managed by some combination of underground injection, treatment and subsequent use, treatment and discharge, or evaporation, subject to compliance with state and federal regulations. Management of these waters is challenging not only for industry and regulators, but also for landowners and the public because of differences in the quality and quantity of produced water, varying infrastructure needs, costs, and environmental considerations associated with produced water disposal, storage, and transport. Unconventional oil and gas development involves technologies that combine horizontal drilling with the practice of hydraulic fracturing. Hydraulic fracturing is a controlled, high-pressure injection of fluid and proppant into a well to generate fractures in the rock formation containing the oil or gas. After the hydraulic fracture procedure is completed, the injected fluid is allowed to flow back into the well, leaving the proppant in the newly created fractures. As a result, a portion of the injected water returns to the surface and this water is called "flowback water" which initially may mix with the naturally occurring produced water from the formation. The chemistry and volume of water returning to the surface from unconventional oil and gas operations thus changes during the lifetime of the well due to the amount of fluid used in the initial stage of well development, the amount of water naturally occurring in the geologic formation, the original water and rock chemistry, the type of hydrocarbon being produced, and the way in which production is conducted. The volume and composition of flowback and produced waters vary with geography, time, and site-specific factors. A workshop was conducted by the National Academies of Sciences, Engineering, and Medicine to highlight the challenges and opportunities associated in managing produced water from unconventional hydrocarbon development, and particularly in the area of potential beneficial uses for these waters. This publication summarizes the presentations and discussions from the workshop.

Shale gas has become one of the most rapidly developing natural gas, providing approximately half of the natural gas for the U.S. Together with the development of shale gas exploration, large quantity of flowback and produced water is being produced. Management of flowback and produced water has become one of the most challenging issues for shale gas operators. Traditional disposal of flowback and produced water is challenged by the increased freshwater demand, water shortage, and more restraining regulations. Beneficial reuse of flowback and produced water is becoming a more attractive option, as it reduces freshwater demand for hydraulic fracturing, minimizes disposal costs, and helps to meet regulations. This study aimed to develop a decision-support tool for shale gas produced water management, treatment and beneficial use. Water quality and quantity data were retrieved from national produced water database and industrial database. Treatment technologies were critically reviewed about their capacities to treat shale gas flowback and produced water. A case study was conducted to evaluate shale gas flowback and produced water beneficial use potentials in Tioga County and Washington County in Marcellus Shale, Pennsylvania. The results showed that the costs of produced water treatment and beneficial use decreased significantly as the treated water flow rate increased. Produced water reuse is more cost-efficient than deep well injection when flowback and produced water from a cluster of wells collected together, and treated in a satellite facility. Small operators are recommended to cooperate to treat and reuse shale gas wastewater together to be more cost-effective. In addition to monetary benefits, reuse of flowback and produced water also augments water resources, reduces the industry reliance on local water supplies, decreases the risks of wastewater spill, remits traffic load and road wearing, helps to meet regulations and policies, and reduces public concerns.

Sediment contamination is a widespread environmental problem that can potentially pose a threat to a variety of aquatic ecosystems. The sediment test methods in this manual will be used by The United States Environmental Protection Agency (USEPA) to make decisions under a range of statutory authorities concerning such issues as: dredged material disposal, registration of pesticides and toxic substances, superfound site assessment, and assessment and cleanup of hazardous waste treatment, storage, and disposal facilities. The use of uniform sediment testing procedures by USEPA programs is expected to increase data accuracy and precision, facilitate test replication, increase the comparative value of test results, and ultimately, increase the efficiency of regulatory processes requiring sediment tests.

A state-of-the-art review of scientific knowledge on the environmental risk of ocean discharge of produced water and advances in mitigation technologies. In offshore oil and gas operations, produced water (the water produced with oil or gas from a well) accounts for the largest waste stream (in terms of volume discharged). Its discharge is continuous during oil and gas production and typically increases in volume over the lifetime of an offshore production platform. Produced water discharge as waste into the ocean has become an environmental concern because of its potential contaminant content. Environmental risk assessments of ocean discharge of produced water have yielded different results. For example, several laboratory and field studies have shown that significant acute toxic effects cannot be detected beyond the "point of discharge" due to rapid dilution in the receiving waters. However, there is some preliminary evidence of chronic sub-lethal impacts in biota associated with the discharge of produced water from oil and gas fields within the North Sea. As the composition and concentration of potential produced water contaminants may vary from one geologic formation to another, this conference also highlights the results of recent studies in Atlantic Canada.

The Promise and the Peril

This study evaluated the feasibility of using abandoned mine drainage (AMD) as make- up water for the reuse of produced water for hydraulic fracturing. There is an abundance of AMD sources near permitted gas wells as documented in this study that can not only serve as makeup water and reduce the demand on high quality water resources but can also as a source of chemicals to treat produced water prior to reuse. The assessment of AMD availability for this purpose based on proximity and relevant regulations was accompanied by bench- and pilot-scale studies to determine optimal treatment to achieve desired water quality for use in hydraulic fracturing. Sulfate ions that are often present in AMD at elevated levels will react with Ba2 and Sr2 in produced water to form insoluble sulfate compounds. Both membrane microfiltration and gravity separation were evaluated for the removal of solids formed as a result of mixing these two impaired waters. Laboratory studies revealed that neither AMD nor barite formed in solution had significant impact on membrane filtration but that some produced waters contained submicron particles that can cause severe fouling of microfiltration membrane. Coagulation/flocculation was found to be an effective process for the removal of suspended solids and both bench- and pilot-scale studies revealed that optimal process conditions can consistently achieve the turbidity of the finished water below 5 NTU. Adjusting the blending ratio of AMD and produced water can achieve the desired effluent sulfate concentration that can be accurately predicted by chemical thermodynamics. Co-treatment of produced water and AMD will result in elevated levels of naturally occurring radioactive materials (NORM) in the solid waste generated in this process due to radium co-precipitation with barium sulfate. Laboratory studies revealed that the mobility of barite that may form in the subsurface due to the presence of sulfate in the fracturing fluid can be controlled by the addition of appropriate antiscalants.