Water management presents challenges, brings opportunities
Increased hydraulic fracturing in oil and gas drilling has meant ever-greater amounts of water, in terms of both completion and disposal.
Handling water isn’t a new problem for the oil and gas industry. In fact, oil companies have been producing brine, along with crude oil, since the earliest days of the industry. Many early fields were uneconomic, because there was no way to separate saleable oil from waste water. A hundred years ago, oilfield chemicals and electrical methods were introduced to separate the two fluids, but disposing of the brine has remained an ongoing challenge.
As field development using hydraulic fracturing accelerates, water management in unconventional shale plays ranks as one of the biggest challenges facing operators, and one of the biggest opportunities for service providers. While oil companies strive to source, transport, transfer and treat millions of gallons of water for each fractured well, service suppliers are working to provide solutions to reduce the amount of water needed, recycle flowback water for reuse, and minimize risks to people and the environment throughout the water management cycle.
Hydraulic fracturing significantly increases the volumes of water that oil companies need to manage, because the method requires huge amounts of water to make up the frac fluid. Operators need to source, transport and transfer this water, as well as capture, treat and recycle water that flows back from the well during testing and production. Depending on the basin, each hydraulically fractured well can require between 2 million gal (in the Barnett) and 6 million gal of water (in the Eagle Ford) for frac fluid, of which 15% to 80% will flow back to the surface and must be treated. All of these operations must be conducted within state regulations to prevent spills, and to protect both surface and groundwater.
According to a recent IHS white paper, as much as 25 billion gal of water are needed every year to support hydraulic fracturing in the U.S. (assuming 5,000 new wells per year). IHS estimates that water management represents 10% of the total well cost, including the cost of hauling the water by truck from the source to the wellsite, which, by itself, represents 85% of the typical water management budget. While this amount of water is not expected to strain the nation’s water supply (it represents less than 0.03% of the total water use in the U.S.), it does present a significant logistical and operational challenge that is highly visible in areas where hydraulic fracturing is taking place. A typical well in the Marcellus play may require as many as 1,000 truckloads to haul water for the fracturing operation, including make-up, flowback and disposal water. In the Eagle Ford play of South Texas, more than 1,500 truckloads may be required.
In some areas, environmental regulations and cost considerations discourage the use of in-ground impoundments and frac tanks for water storage. Several vendors are now providing large above-ground storage tanks. For example, Rockwater Energy Solutions provides water storage tanks that hold up to 41,000 bbl and can replace more than 80 frac tanks and 150 truckloads, Fig. 1.
In some drought-stricken areas like South and West Texas, water used for fracturing may put a stress on the local water supply. Surface water sources in these areas are limited, and large volumes of water extracted from groundwater wells have been blamed for a drop in the water table used for irrigation or residential use.
Faced with supply pressures and high transportation costs, oil and gas operators are seeking to reduce the total volume of freshwater they need for their operations by recycling flowback water (and sometimes produced water), and by using innovative methods of treating the flowback and formulating frac fluid, using the recycled water.
ASPECTS OF WATER MANAGEMENT
Oilfield water management has four distinct phases: water sourcing, transfer, recycling and reuse, and disposal. Each requires specific expertise and technology, and suppliers in each phase may take different approaches, based on their experience and product offering.
As the name implies, water sourcing involves finding an economical, sustainable source of water to be used for makeup of drilling and frac fluids, and may involve purchasing surface or ground water from nearby landowners or municipalities. This water must be transported to the well or pad location by truck or pipeline, and may be stored on the lease in lined impoundments, frac tanks or larger temporary storage tanks.
Water transfer is the process of moving water between pits, tanks, mixing facilities, flowback pits and treatment equipment, without causing leaks or spills.
Water recycling and reuse involves removing heavy metals, suspended solids, bacteria and some dissolved solids to create a fluid that can be used as a base for hydraulic fracturing fluid. This process may produce solids or a concentrated waste fluid that can be disposed of in landfills or injection wells.
Disposal of frac fluids may involve trucking the final waste product to an injection well, or to a centralized treatment facility, which may have the capability to treat the fluid to a level that it may be discharged into rivers. Disposal wells and the constituents of effluent streams are closely regulated by the states and the EPA. There are more than 30,000 Class II disposal wells in the U.S., so operators in most shale basins have easy access to this disposal method. However, because no disposal wells are operating in Pennsylvania, waste water has to be trucked to wells in Ohio, increasing water management costs, and providing an incentive for operators to minimize the volume of waste fluid.
In addition, earthquakes associated with waste water injection have caused public concern, and regulators in Ohio and Arkansas have placed restrictions on disposal well placement and operation. This situation provides another incentive for operators to recycle and reuse their flowback and produced water.
Water sourcing. Water source options vary by basin, but operators typically will purchase the rights to surface or ground water from a land owner, as close as possible to the lease, or obtain a permit from the state and local authorities to use river water, and pay a fee for each barrel of water taken from the property. If the source is groundwater, the operator is responsible for drilling and constructing the water well.
Some operators may not understand the importance of proper water well placement, design and construction in managing the overall cost per barrel of sourced water. Hydrogeologists with experience at finding aquifers and evaluating their production potential should be consulted to identify the best water source and optimum well placement. Operators also should take as much care in drilling and completing water wells as they do for oil and gas wells.
“A basic slotted casing or gun-perforated completion without a gravel pack, and no or minimal development, will not produce as much water as a properly designed, constructed and developed well, completed with wire-wrap screen, gravel pack and a good cement seal. This is simple, proven science gained from over a hundred years of water well drilling experience.” said Kent Wartick, President of Layne Energy Services, which provides water sourcing and well drilling services. “The combination of hydrogeogical services and a well-constructed water supply well can increase water production and extend the well’s useful life substantially, resulting in a lower cost per barrel of water produced.
“The soft costs, such as additional maintenance, time and aggravation associated with a poorly designed, constructed and developed well, should not be discounted. Doing it right the first time can save a lot of headaches. In addition, we believe there is a responsibility to properly construct wells to prevent contaminants from entering the ground water from the surface, or comingling of water from fresh and brackish aquifers within a well.”
Water sourced for oilfield use does not need to be potable, and many source wells now are targeted at producing deeper, brackish aquifers, where water is not suitable for residential or agricultural use, but it can be treated for use in frac fluids.
Water transfer. Services are required to move source water, prepared frac fluid, flowback water and treated water between storage tanks and pits, and fracing operations on the wellpad throughout the water management cycle. Water is conveyed by hoses, line pipe or temporary pipelines with the required pumping equipment. If the flowback water treatment will be conducted at a central location away from the well pad, and no water pipelines have been installed, trucking will be required for water transfer.
At first glance, water transfer may seem to be a low-tech service, and this phase of water management has attracted many small-scale suppliers, who have entered the business with basic aluminum or heavy-line piping, pumps and relatively unskilled labor. However, the water transfer stage is critical to meeting operator objectives of minimizing water use, avoiding spills and maintaining a safe operation. Hoses with a minimum number of connections can reduce the chance of leaks, compared to jointed pipe, and hose made of more durable material can avoid failures caused while running the hose in the field, encountering rocks, cacti and other obstacles. Trained personnel and automated spooling systems, like those provided by Layne, also can reduce safety risks during water transfer operations.
To minimize freshwater use, operators need to recycle and reuse flowback and produced water. Treatment options vary depending on the content of the flowback water and the quality of water needed to formulate frac fluid for the next well. Flowback water contains minerals and fluids from the formation, oil and grease, suspended solids (measured as total suspended solids, or TSS) and dissolved solids, typically salts (measured as total dissolved solids or TDS).
A wide range of treatment options is available from numerous suppliers, including filtration, electrocoagulation, chemical precipitation, distillation and membrane filtration. Each water management supplier takes its own approach toward meeting the operator’s objectives, which will vary based on the project and the shale basin.
Utilizing high-TDS water. Halliburton began to develop solutions for water management challenges in 2008. “Initially, we focused on water treatment, biocide reduction and fluid quality,” said Walter Dale, Halliburton’s strategic business manager for Water Solutions. “In 2011, we established our Water Solutions program, which we now call our H20 Forward Service.” Since then, Halliburton has introduced a number of options to treat variable flowback and produced water, and has developed innovative ways to use high-TDS water in frac fluid.
Halliburton’s CleanWave water treatment service (Fig. 2) uses mobile units containing electrocoagulation cells that remove grease and oil, suspended solids and heavy metals from flowback and produced water. “CleanWave treatment technology cleans produced water enough to enable effective crosslinking and fracturing,” Dale said.
Bacteria in flowback water can cause corrosion and create H2S, which can impact safety and lower the fluid viscosity. To remove bacteria with a reduced amount of chemical biocides, Halliburton developed the CleanStream Ultraviolet Light Bacteria Control Process. This service is provided with mobile units that use ultraviolet light to treat up to 100 bbl/min. The cellular DNA in the bacteria absorbs the energy from the UV light, rendering it incapable of reproducing. “If wellsite logistics permit using the CleanStream service on the fly, biocide addition can be reduced to zero,” Dale said.
Halliburton has leveraged its experience in designing cross-linked and slickwater frac fluids to develop formulations that can use minimally treated flowback water (with TDS as high as 300,000 ppm) to achieve production results similar to those obtained with fresh source water.
Operators can take three approaches to water treatment. They can treat the water to high quality, which creates high volumes of waste and is inordinately expensive. They can add fresh water to flowback water to meet specifications, but this compromise option doesn’t achieve the full benefits of recycling. Or they can perform the minimum treatment necessary, and then adjust the frac fluid formulation to reuse 100% of the available waste stream.
“We believe that through fluid adjustment and development of high-TDS fluids, like our UniStim fracturing fluid, we help ensure that operators can cost-effectively recycle flowback water without jeopardizing fluid integrity or well integrity while using any source of alternative water to replace fresh water,” Dale said.
This approach proved successful for an operator on a Permian basin well. The operator wanted to re-use produced and flowback water, but high TDS concentrations of up to 285,000 ppm made it unsuitable for making up a conventional crosslinked frac fluid. Halliburton treated the water onsite, using its CleanWave Service to remove hydrocarbons, heavy metals and suspended solids. Halliburton estimates that 1,400 truck trips were eliminated by treating fluid onsite. The resulting high-TDS water was used in a new crosslink fluid formulation that enabled the operator to frac the well effectively while saving 8 million gal of water and more than $500,000 in operating cost.
Know your water’s chemistry. In 2010, when Baker Hughes entered the oilfield water management business, there were no standard practices across the industry. “The term water management referred to trucking, logistics, disposal, and in some cases, flowback dilution with fresh water,” said Steve Monroe, Baker Hughes product manager for Surface Water Management. “We believed, at the time, that water management should include the entire life cycle of water in the oil field.”
Four years later, Baker Hughes’s H2prO line of water management services includes water sourcing, logistics, storage, conveyance and treatment to minimize the volume of water to be disposed, Fig. 3. The company offers fit-for-purpose solutions to reuse produced water, including treatment equipment, if necessary.
“Baker Hughes leverages its reservoir expertise, and its 100 years of upstream chemical experience, to fully understand water life cycles and the chemical makeup of water on each project, and to design solutions that meet each operator’s needs,” Monroe said. “Our sampling, testing and analysis expertise includes upstream chemistry, water treatment and frac fluid chemistry.”
Baker Hughes has introduced mobile units for onsite treatment of flowback and produced water to address heavy metal and solids removal, hydrogen sulfide (H2S) remediation, disinfection, desalinization and filtration. Before each project, oilfield water application engineers conduct pretreatment water analyses to ensure that treated water will meet specifications for reuse.
The H2prO HMS service uses chemical-free electrocoagulation technology to remove heavy metals and suspended solids, to limit scaling and formation damage during fracturing.
The H2prO HD service uses environmentally preferred chlorine dioxide (ClO2) chemistry to neutralize microorganisms, H2S, iron sulfide, phenols, mercaptans and polymers. This prevents corrosion and plugging, when water is used downhole. The H2prO SR service removes suspended solids using proven filtration technology. Each modular unit can filter 10,000 bwpd.
Baker Hughes has treated 50 million bbl of water for hydraulic fracturing since mid-2012, including water used in 500 wells in North America during 2013.
Marcellus case history. An operator in Butler County, Pennsylvania, in the Marcellus shale, was trucking pit water from one impoundment to another. The operator was challenged with treating flowback and produced Marcellus water that had significant amounts of bacteria, dissolved iron, hydrogen sulfide (H2S) and iron sulfide, which resulted in poor water quality and a pungent odor. The destination impoundment for these fluids contained fresh water for use in a multi-well fracturing operation. Adding the untreated produced and flowback water to the impoundment would have contaminated the entire volume of water.
After reviewing multiple potential treatment strategies, Baker Hughes recommended its H2prO HD system that generates chlorine dioxide (ClO2) and can treat H2S, iron sulfide and bacteria simultaneously. A mobile H2prO HD system was used to treat the 76,000 bbl of water at a rate of 20–25 bbl per minute, as it was being transferred from the storage pit to working tanks. The water was then hauled via truck to the second impoundment location, where it was tested, again, to ensure it met quality and safety standards.
The treatment resulted in an eight-bottle log reduction in bacteria, and oxidized the iron sulfide and H2S to improve water clarity and eliminate the odor. The ClO2 treatment enabled the operator to reuse a greater percentage of the produced and flowback water in hydraulic fracturing operations, while using the same frac fluid formulation used on previous wells. Treating this water before transporting it preserved the quality of the 5 million gal of fresh water already contained in the impoundment, so additional treatment was not required.
Adapting to each basin. Formed in 2011, through the combination of water management and oilfield chemical companies, Rockwater Energy Solutions provides water sourcing, water transfer, logistics, storage, flowback and production testing, water recycling, and completions and production chemicals. The company offers most of these services in every major shale play in the U.S., as well as in Western Canada. Several of Rockwater’s legacy companies have been in operation over 40 years.
“The most critical aspect of a successful water reuse program is finding a solution that provides an economic benefit for operators while maintaining performance with the frac fluid and formation chemistries,” said Larry O’Donnell, Chairman, President and CEO of Rockwater. “The degree to which water needs to be conditioned varies significantly from basin to basin, or even well to well.”
“Rockwater’s involvement in the full range of water management services coupled with our chemists who have been designing fracturing fluids for over 25 years, enables us to provide custom solutions that can help our customers improve efficiencies throughout the water life cycle and reduce their costs,” O’Donnell said.
Rockwater’s water treatment services include a patent-pending electro-oxidation treatment that can condition produced water to a level that is compatible with both slickwater and crosslinked frac chemistry without freshwater dilution.
This technology was applied recently for an operator in Utah’s Uinta basin to reuse produced water in a crosslinked frac fluid. Rockwater chemists first evaluated the operator’s produced water to determine the appropriate treatment solution to adapt to the borate frac chemistry. Produced water was then collected at a centralized mobile treatment facility, to be conditioned to the pre-determined specifications, Fig. 4.
Because the quality of the incoming produced water was highly variable, operations staff monitored it and treated it on the fly to maintain the target water specifications. The top three frac stages were performed with 100% undiluted treated produced water. The bottom three stages were completed with fresh water.
The results from the top three stages were positive, and the operator reduced overall water management cost by 31% compared to offset wells. Currently, the well is producing at a rate similar to those of other nearby wells in the basin, and the water treatment program has been integrated into the operator’s ongoing completions operations.
A range of water-treatment technologies. Based on its 130-year history of solving water management and water well drilling problems for industrial, municipal and mining clients, Layne Energy Services, a division of Layne Christensen, recently entered the oilfield water management business. In addition to water sourcing and transfer capabilities, the company has a full range of water treatment technologies, including electrocoalgulation, reverse osmosis, filtration, oxidation, distillation, evaporation and ion exchange processes to help operators recycle and reuse flowback and produced water. Depending on treatment requirements, Layne also can provide modules to remove boron, H2S or other contaminants, as well as filter presses to further reduce the amount of waste generated.
Layne recently introduced its MOS mobile water-recycling system, which provides consistent treatment results for produced and flowback water, Fig. 5. According to Layne’s Kent Wartick, the system delivers water of higher quality than other available systems at the same or less cost per barrel.
The MOS system removes oil and grease and bacteria, while dramatically reducing total suspended solids and iron. The result is clear, clean brine that is ready for reuse in the hydraulic fracturing process. The unit incorporates a module that removes hydrocarbons and heavy metals, and an exclusive membrane system that removes 100% of the bacteria and 98% of the TSS from the treated water.
WATER MANAGEMENT STILL EVOLVING
The science and practice of oilfield water management are still evolving, as operators and service companies work to meet the challenge of providing enough water to sustain hydrocarbon development in shale plays in a responsible, sustainable manner. No single solution can address all water management challenges. Some operators, with easy access to fresh water and inexpensive disposal, will not invest in the storage and logistics required to recycle flowback and produced water. However, increasing costs and environmental scrutiny have made water reuse a priority for most operators developing unconventional resources today. The oilfield service industry is responding with a wide range of solutions to meet this challenge.
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- What’s new in well logging and formation evaluation (April 2019)
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- ConocoPhillips’ Greg Leveille sees rapid trajectory of technical advancement continuing (February 2019)