Improving produced water management with electromagnetic flowmeters

TIM LELLMAN, KROHNE Group 

The oil and gas industry is turning to electromagnetic flowmeters (magmeters) to address the growing challenges of managing produced water—the water brought to the surface during hydrocarbon extraction. While the volume of produced water is surging, the industry also faces mounting constraints on its use and disposal.  

Fig. 1. Produced water lifecycle: Accurate, reliable flow measurement is needed at every stage to operate at optimal efficiency and control costs while ensuring that water is not lost into the environment.

These growing financial and environmental pressures have heightened the importance of accurate and reliable measurement of produced water flow at every stage — from extraction and separation to transportation, treatment, and eventual reuse or disposal, Fig. 1.  

SURGING VOLUME OF PRODUCED WATER 

Produced water volumes have surged alongside expanded oil and gas extraction activity in North America. As global energy demand intensifies, the industry continuously seeks out new reserves and employs methods to tap into previously inaccessible oil and gas fields.  

Extraction methods now include the exploitation of unconventional reserves, such as shale formations, which often involve hydraulic fracturing or fracing. This process requires large volumes of water to fracture the shale rock and release hydrocarbons, leading to a significant increase in the quantity of water that needs to be managed after the extraction process.  

Additionally, as fields mature, more water is produced for each volume of oil or gas extracted. 

CHANGING PERSPECTIVES 

Previously considered an inconvenient by-product, produced water has begun to gain recognition as a critical component of industry operations. This shift reflects the industry’s broader move toward circular economy principles and sustainability.  

Technological advances enable more effective treatment and use of produced water, transforming it from a cost center to a potential asset. Some companies are exploring new ways to convert the water’s constituents into valuable products or for reuse in operational processes. 

In the U.S. and globally, federal, state or local governments increasingly strive to effectively manage produced water to safeguard surface and groundwater resources while alleviating the future demand for fresh water. By pursuing the pollution prevention hierarchy of "reduce, reuse and recycle," the industry is exploring traditional and innovative approaches including the reuse of treated produced water for irrigation of non-edible agriculture, such as cotton or biofuel crops.  

In addition to protecting freshwater resources, regulators aim to mitigate seismic risks by imposing strict production limits and requiring detailed monitoring of water injection during oil and gas operations. Reinjection can increase stress along fault lines, potentially triggering seismic activity. 

METICULOUS MONITORING 

Accurate, stage-by-stage water measurement ensures accountability and prevents loss throughout the process. This meticulous monitoring helps maintain water integrity and sustainability throughout its lifecycle. 

Moreover, accurate flow measurement is essential for controlling costs and ensuring optimal operational efficiency. This is particularly evident in the transportation and treatment of produced water. Transportation, especially via truck, represents a significant expense and requires effective flow management. The treatment of produced water, removing the cocktail of organic and inorganic compounds, also necessitates precise flow measurement to maintain cost-efficiency and operational effectiveness. 

MAGMETERS: IDEAL FOR MEASURING PRODUCED WATER 

Fig. 2. KROHNE 10-in. ENVIROMAG meter installed on produced water line in West Texas.

The operational principle of electromagnetic flowmeters makes them particularly well-suited in produced water applications in the oil and gas industry, due to the saline nature of the water.  

Magmeters function, based on Faraday's Law of electromagnetic induction, where the voltage induced is directly proportional to the speed of the fluid, the magnetic field's strength and the length of the conductor. In a magmeter, the salty water serves as the conductor. Since produced water is high in salinity, it enhances the electrical conductivity of the water, leading to highly accurate measurement.  

Moreover, the non-intrusive design of magmeters enables them to operate efficiently even in corrosive saline water environments, without experiencing degradation. As a result, they provide a cost-effective and dependable solution for managing and monitoring produced water systems, Fig. 2. 

TRANSITION FROM MECHANICAL FLOWMETERS 

While mechanical flowmeters have traditionally been a common choice for measuring produced water, a rapid transition towards electromagnetic flowmeters is occurring in new installations and repair/replacement scenarios. 

Fig. 3. OPTIMASS 1400C Straight tube Coriolis mass flowmeter (foreground) and OPTIFLUX 2100C magmeter installed on an oil separator.

This transition is motivated by vastly improved accuracy, reliability, longevity and ease-of-maintenance. Moreover, electromagnetic flowmeters offer additional capabilities, such as online diagnostics and data collection.  

Reliability. Electromagnetic flowmeters are completely electronic, eliminating the need for moving parts, Fig. 3. This makes them far more robust and less prone to wear-and-tear, thereby reducing the need for frequent maintenance and replacement. As a result, they have an exceptionally long lifespan. Krohne has magmeters that have been in service for over 25 years, continuing to provide accurate flow measurement of produced water.  

Superior accuracy. Electromagnetic flowmeters offer better accuracy compared to their mechanical counterparts. Mechanical flowmeters can be affected by the viscosity of the fluids they measure, which can lead to inaccuracies. On the other hand, electromagnetic flowmeters are independent of fluid properties, such as viscosity, temperature and pressure, offering more reliable readings. 

Ease of maintenance. Magmeters offer significantly easier maintenance compared to mechanical flowmeters. The latter necessitate frequent maintenance, including an annual check and periodic removal from the line. Internal components require inspection and replacement, and often need to be sent for rebuilding. Available information within the magmeter also can be periodically monitored to alert the user to any potential issues, such as electrode wear or coating or even a degradation of the liner in extreme conditions, without having to take the meter out of service. 

SMART METERS: ELECTRONIC AND SMART CAPABILITIES 

The intrinsic electronic nature of magmeters enables the seamless integration of essential, groundbreaking smart functionalities that are beyond the capabilities of mechanical flowmeters. 

Leak detection. Advanced leak detection is a key smart feature of magmeters that adds significant value over mechanical meters. These sophisticated devices are capable of continuously monitoring the flow rate and identifying discrepancies, which can indicate a leak within the system. By doing so, magmeters can alert operators to even small leaks that might go unnoticed with less sensitive devices. Moreover, when combined with a relatively simple mass balance system, the magmeters can also provide information about the location, extent and severity of the leak, allowing for prompt action to be taken when needed and avoiding false alarms that waste resources. 

Online diagnostics. These intelligent devices can self-monitor and provide operational status updates, ensuring they are functioning correctly and alerting maintenance personnel to any irregularities. The online diagnostics perform health checks on the meter, detecting issues, such as electrode fouling, liner deformation, and ensuring accuracy within factory specifications. 

Fig. 4. Magmeters have no moving parts, making them more robust and less prone to wear and tear. As a result, they have an exceptionally long lifespan.

This proactiveness empowers operators to address issues before they escalate, avoiding costly downtime and enhancing overall system reliability. Mechanical meters offer no such visibility: if the reading appears inaccurate, the entire meter must be removed from the line for maintenance. 

Magmeters not only provide continuous monitoring of the meter's performance, but also continuously track variations in the qualities of the water passing through, including the water's conductivity.  

Data collection and analytics. Mechanical meters typically only provide a flowrate reading, but electronic magmeters can record and store a wealth of data over time. This information can be used for detailed analysis, optimizing system performance, and improving resource management through trends and patterns identification. The integration of magmeters with industrial Internet of Things (IoT) platforms can also facilitate remote monitoring and advanced data analytics for strategic decision-making. 

SELECTING A MAGMETER 

When measuring produced water, it's important to consider that magmeters are not the only type of meter required. While magmeters are well-suited for water lines, Coriolis meters are more ideal for oil lines, and Ultrasonic or Coriolis meters are commonly used for gas lines. To ensure efficiency and avoid redundancy, incompatibility, and training hassles, consider an integrated approach by leveraging the same electronics to manage all meters in your portfolio. With instrumentation and metering systems from a single vendor, operators can rely on seamless integration of all components. 

Choose suppliers offering models for your full pressure and application range, including high-pressure magmeters specifically designed for injection wells, Fig. 4. By considering these factors, you can optimize the performance and effectiveness of your metering systems. 

LOOKING FORWARD 

As produced water volumes rise and disposal regulations tighten, electromagnetic flowmeters are becoming vital solutions for efficient, sustainable operations.  

The transition from conventional mechanical meters to intelligent electromagnetic flowmeters is driving more efficient and effective management of produced water throughout its lifecycle. By embracing these advancements, the industry can navigate the financial and environmental pressures while ensuring sustainable practices in water management. 

TIM LELLMAN has been with KROHNE since 2020 and resides in the greater San Diego, Calif., region. He has North America responsibility for all electromagnetic flowmeter products, including the OPTIFLUX and ENVIROMAG magmeters mentioned in this article.