Innovation optimizes produced water disposal

Abstract

Water is considered a byproduct of oil and gas production and must be carefully managed. This water, usually referred to as “produced water”,
is the largest volume waste stream associated with upstream petroleum operations.

Most oil shale fields include pipeline infrastructure to gather produced water from wells. Pipelines transfer the water to temporary storage at either a disposal well location or at a central treatment facility.

Wolseley Industrial Group worked closely with its customer, a leading produced water management company, to develop solar-powered control stations for water-gathering pipelines located in the oilfields of West Texas and New Mexico. These innovative systems enabled remote operation of single-stage isolation and modulating valves to control the flow of produced water in the high-pressure pipeline network.

By partnering with a trusted automation equipment supplier like Wolseley, oilfield service companies can find new ways to improve the efficiency and reliability of their water disposal infrastructure while improving safety and reducing costs.

WATER DISPOSAL CHALLENGES

With a growing focus on corporate responsibility and sustainability, the proper handling and disposal of waste streams is critical to all oil- and gas-related businesses. Operators must ensure regulatory compliance while protecting assets, personnel and the environment.

Produced water from hydraulic fracturing contains chemicals that are potentially toxic and cannot be exposed to fresh water ponds or groundwater. Government and industry regulations require the water be disposed of in an approved and effective manner.

Deep well underground injection has become a popular method for the disposal of fracturing fluids and other substances from shale oil and gas extraction operations. The produced water is deposited into deep geologic structures, many of which have trapped brine for millions of years.

These structures are often a mile or more below underground drinking water sources, separated by billions of tons of impenetrable rock.

NEED FOR RELIABLE AUTOMATION

As part of the water treatment operation, there is a need for automated valve technology to control the flow in high-pressure water-gathering pipelines. In many cases, however, these pipelines run for miles with no power to activate the valves.

The customer wanted to optimize its water-gathering operations and had specific requirements for the valve application:

  • Control system pressure to and from well sites
  • Shut down lines in the event of a break or other failure
  • Eliminate high-maintenance devices such as air compressors and other rotating equipment

The customer sought a reliable pipeline control solution, as valves and other equipment would be situated every five miles or so in areas that were “off the grid.” Without the availability of gas and electricity in these locations, the use of solar-power for pipeline control stations seemed like a logical choice.

Solar power has had a significant role in oil and gas production for decades, largely due to the vastness of most producing fields. However, solar systems can be highly complex. Proper design is key, from the size of solar panels selected to the converters used. If there is a mismatch in load capacity at any point in the system, failures or accidents can occur. Therefore, it is best to have experts analyze load requirements and design an appropriate system for the application.

 

By partnering with a trusted automation equipment supplier, oilfield service companies can improve the efficiency and reliability of their water disposal infrastructure while improving safety and reducing costs.

Background

A major oilfield services company within the US owns and operates an extensive network of water gathering pipelines and saltwater disposal well focused on eliminating the problem of produced water for oil and gas producers. Its approach to produced water disposal minimizes environmental impact and improves health and safety, while reducing lease operating costs and improving reliability.

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Results and Measureables

The use of solar power in industrial valve automation goes back several decades. However, technological advances in efficiency and storage mean the technology has become a practical, dependable alternative for many isolated locations.

The customer is now utilizing a robust solar system providing power to operate PLCs and electric valve actuators for pipelines transporting contaminants from fracturing sites to water gathering and disposal facilities.

The innovative solar power solution provides the proper voltage to operate automated modulating and isolation valves with a tremendous safety factor. The electric actuators incorporate an internal battery system that also provides position feedback and diagnostics. A feature programmed the system provides a low-voltage alarm to notify pipeline operators if the power from the solar system has dropped below the level required for valve operation.

In addition, the solar system includes a control panel that utilizes a series of voltage regulators to monitor the battery voltage. The system only provides charging when the voltage drops below specified levels. This prevents overcharging the battery and possible degradation.

Testing of the solar-powered valve packages provided valuable insights on system wiring. A default 24Vdc signal had been used to open the valve, and when de-energized, it would close. Upon loss of signal power, the valve would again close. This function was set up in the actuator’s two-wire priority to close on loss of signal. It was subsequently requested that the valve fail in place with one 24Vdc signal to open and another to close. All of the units were reconfigured and successfully retested.

The project team also learned the pipelines would be hydro-tested after the valves were installed. Instead of shipping the devices in the closed position, it was decided that they should remain open. This way, the hydro-tests could proceed even if the solar system was not yet connected to the valves.

Finally, the project team realized that it is impossible to predict the weather. Upon completion of assembly, there was a good balance of sunny, cloudy and rainy days, and engineers were able to fully test the valves and confirm they would stroke with no sunlight for at least two days. However, just before the viewing of the testing procedures, there was complete sunlight and a proper test could not be emulated. This required the placement of covers over the solar panels. The valves were stroked fully open and fully closed five times off battery power each day over a three-day period. Upon removal of the covers, the batteries immediately started charging and were fully charged in two to three hours depending on the solar system.

CONCLUSION

Oilfield service companies seek to optimize their network of produced water pipelines and underground injection wells, which are designed to gather and dispose of saltwater for the shale oil industry. By partnering with a trusted automation equipment supplier like Wolseley Industrial Group, they can find ways to improve the efficiency and reliability of their water disposal infrastructure while improving safety and reducing costs.

 

Figure 2: Pipeline control stations employ 12 and 16-inch ball valves automated with electric actuators. Each value has its own solar panel.

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