Heavy metals such as arsenic, cadmium, copper, lead, mercury, etc. can be critical components of many wastewaters and often require treatment. Conventional precipitation & coagulation (P&C) processes are well-practiced to treat heavy metals. Saltworks has modernized these processes to reduce footprint, maintenance, and operating costs.
Shale Water and NORM
Jun 14th 2018, Updated Sep 29th 2021
- There are four types of shale waters, each with unique properties, uses, and treatment approaches.
- If your frac or produced water contains NORM (naturally occurring radioactive material), plan to manage them by keeping them in solution, precipitating them for safe handling, or diluting them followed by water disposal.
- Many factors should be considered in assessing petrolithium extraction projects: concentration of lithium, quality of the water, disposal availability, cost of power, location, flow rate, and more. In the past, concentrations lower than 500 mg/L would have been considered non-viable. With otherwise favourable conditions, wastewaters with lithium >70 mg/L and sustained flow rates >1,000 m3/day might now be considered viable.
Shale water management starts with understanding the distinct types of water, their uses, and their volumes. This will enable better management of the site’s water balance to ensure that the right amount of water is available when needed and excess water does not exceed your storage capacity. Practitioners also need to consider the chemistry, which may include scalants, total dissolved solids (TDS), and NORM (naturally occurring radioactive material). The water chemistry significantly impacts shale produced water treatment strategy, as well as informing end-of-life options for the waste by-products that are left behind once clean water is removed. These by-products are often referred to as reject or residuals.
The Different Types of Waters Used in Shale Gas Operations
Four primary types of water are used in shale gas operations.
Source water is drawn from nearby water sources, such as surface waters or groundwater, and is typically used for hydraulic fracturing (also known as ‘fracking’).
Saline re-use water is the water that returns after the fracking process, with increased salinity, but can sometimes be re-used as source water. It may require mild treatment before being used for another fracking process.
Frac flowback is the water that returns from the ground, following a fracking process. Most of it returns rapidly after the fracking process and will include chemicals employed in fracking that can change the treatment process. The flowback flow rate slows over the first week(s) while TDS concentrations increases. Some of this flowback may become saline re-used water, if needed for future fracking applications.
Produced water also returns to the surface, like flowback, but produced water largely originates in the formation. It tends to flow more steadily over longer periods of time and will have a higher TDS.
See the table below for additional details about each water type.
|Water Type||Utilization||Characteristics||Treatment||Flow (m3/day)|
|Source water||Fracking||Usually locally sourced freshwater, such as surface water or groundwater with little to no TDS||Chemicals and sand enhancements may be added||High during fracking process, then tapers to zero|
|Saline re-used water||Fracking (re-used)||TDS: 10,000 to 200,000 mg/L and scaling ions can be present||If re-used in a fracking process, the water is often filtered and occasionally softened (to remove barium & calcium)||Best maximized to reduce future management volumes|
|Frac flowback||Re-used if source water needed, otherwise disposed of or treated||TDS increases over the first week of flowback||See our shale water treatment options||High immediately post fracking (~70% of injected water returns), flow rate tapers down over the first week|
|Produced water||Re-used if source water needed, otherwise disposed of or treated||TDS varies but often as high as 100,000 to 200,000 mg/L||See our shale water treatment options||Ranges from 10-1,000 m3/day (63–6,300 BBL/day) per well|
NORM: NORM are naturally occurring radioactive materials, with radium and its many forms being the most common. Not all produced water contains NORM, but they are occasionally encountered in North American shale.
- It is important to understand the major risks associated with handling water that contains NORM since these risks can be managed. First, ingestion of radioactive material either through inhalation or swallowing is the primary hazard. Always wear gloves and wash your hands and clothes whenever working around potentially radioactive material. Never eat food near NORM and do not bring gloves used to handle NORM into a food zone. Second, gamma rays given off by NORM can be harmful; however, water is an effective insulator. Putting this into context, humans are exposed to more radiation on a 2-hour flight, than standing next to NORM containing produced water for an extended period.
- There can be some risk if NORM precipitate and become dried out, removing the insulating properties of water. NORM can be precipitated alongside barium, which can be achieved by adding sulfates (sodium sulfate) or carbonates (sodium carbonate) at an elevated pH (pH > 9). NORM may also precipitate as a sludge on the bottom of tanks and filter bags, and they should be checked with a radioactive test before handling for safe disposal by a certified party. Diluting NORM sludge with water can improve safety for the reasons mentioned above; however, this will create more liquid waste. The best strategy is to measure the presence of NORM in your water and develop a plan to manage them, either through precipitation removal and safe handling or water disposal.
- Chlorine dioxide treatment and removal: Chlorine dioxide is used in shale waters to precipitate iron with possible NORM co-precipitation. As a benchmark, the cost of removing iron using chloride dioxide varies widely from $3–$50/m3 ($0.5–$8/BBL), depending on the volume of water that needs to be treated. Chlorine dioxide will damage membrane treatment systems, so be sure to remove the chlorine dioxide upstream of a membrane system. There are many options for this, including activated carbon (expensive) or sulfites addition (more common).
Lithium: Some oil field brines contain lithium in the 60–100 mg/L range (0.006–0.01%) and there is excitement for the potential of harvesting lithium from oil field brines (overview of lithium brine extraction technologies here). This is a new and rapidly developing space so concluding that these resources could be economic at the time of writing would be premature.
Saltworks holds patents on lithium extraction, has built machines for lithium companies, and has technology to selectively extract lithium. While the best economics for produced water management are typically achieved through sound water management and treatment, options that incorporate lithium extraction from brine may be worthy of study.
Shale gas and oil production presents a leading energy source moving forward, yet its future and production is tightly linked to water management. Every water type, job site, and economic case is different. Contact us to review your specific situation, benefit from our expertise, and assess if your water management costs or risks can be lowered.
Saltworks Technologies is a leader in the development and delivery of solutions for industrial wastewater treatment and lithium refining. By working with customers to understand their unique challenges and focusing on continuous innovation, Saltworks’ solutions provide best-in-class performance and reliability. From its headquarters in Richmond, BC, Canada, Saltworks’ team designs, builds, and operates full-scale plants, and offers comprehensive onsite and offsite testing services with its fleet of mobile pilots.
Comtech Industries and Saltworks partnered to deliver the innovation. Before today, there were two types of shale evaporators: the open type that evaporates direct to atmosphere, presenting air emissions risk; and the closed type that produces distilled water requiring subsequent management of release or re-use. Comtech and Saltworks tested an innovative new third option known as the “AirBreather.”
Although there are many water management options available for shale operators, there is no one-size-fits-all solution. It is important to understand the costs, alternatives, and technical limitations of each option and develop a blended water management strategy.
We treat oil & gas produced waters to reduce waste volumes and disposal costs, minimize chemical usage, and recover more hydrocarbons.