Lura Parrent, application engineer at Emerson and Brian Van Vliet, Entrepreneurial Team member at Spartan Controls, recently published an article in the December 2020 issue of Processing. The article describes new methane emission standards in the United States and Canada and discusses ways to comply while saving significant sums. The article is titled Meeting New Methane Emission Standards Profitably and is summarized below.
Reducing greenhouse gas emissions has become a major goal in both the United States and Canada, and methane remains the focus of that effort since it is 25-30 times more damaging than carbon dioxide. Upstream oil and gas operations are a significant source of methane emissions, so recent regulations are targeted to this area.
Upstream emission issues
Lura and Brian describe the problem:
Many upstream oil and gas sites are located in very remote areas. The control requirements at the well head and early separation sites are relatively simple, but they do require a source of pneumatic or electric energy to operate valves and other instruments. Since compressed air or power are often not available, many companies utilize pressurized natural gas to operate their pneumatic instruments and control valves. This solution works well but creates a problem.
Pneumatic instruments are designed to bleed air constantly, and they vent still more air as they operate the valves. When natural gas is used, it is continuously emitted in considerable quantities.
In response to this issue, both the U.S. and Canadian governments have passed regulations requiring any equipment installed and/or modified to meet new source performance standards, including a natural gas bleed rate of < 6 SCFH. There are also revised standards for leak detection and repair (LDAR), which tie inspection schedules to emission performance.
Hidden savings
One might consider these regulations as burdensome, but they offer an opportunity for significant savings. A single pneumatic pressure controller and an associated pneumatic control valve with positioner operating on natural gas bleeds approximately 80 SCFH. That amounts to 700,800 SCF of fuel gas per year, wafting away $1,400 of gas per loop per year. If that pneumatic equipment could be replaced with a low or zero bleed option, it would satisfy the new regulations and save money.
Low bleed pneumatic money saving options
One method to satisfy the regulations is replacing the pneumatic components with low-bleed pneumatic components. All of the controllers, pressure pilots, and level controllers shown in Figure 1 offer bleed rates below 6 SCFH.
Figure 1: All of the pneumatic components shown above have steady state natural gas bleed rates of less than 6 SCFH. From left to right: Fisher C1 Controller, 4195K Controller, 4660 High-Low Pressure Pilot, L2 Level Controller, and L2SJ Level Controller.
Lower cost retrofit kits are available for some pneumatic models to convert them to low bleed operation without a full replacement. Usually these replacements/upgrades reduce vented methane by a factor of eight to 10, saving hundreds of dollars a year. Replacing a pneumatic controller with a Fisher C1 would save $845 in natural gas per year, resulting in a quick ROI.
Low bleed electric/electro pneumatic money saving options
Another alternative to meet the standards and recover gas is replacing the existing pneumatic components with all electric and/or electro-pneumatic low-bleed components. These devices combine a zero-bleed electronic component with low-bleed pneumatics to further reduce methane venting. All of the transducers, positioners, and level controllers shown in Figure 2 offer bleed rates below 6 SCFH.
Figure 2: All of the electric and electro-pneumatic instruments shown above have steady state natural gas bleed rates of 0 to 6 SCFH. From left to right and top to bottom: Fisher i2P-100 Transducer, FIELDVUE DVC6200 Positioner, FIELDVUE DVC2000 Positioner, L2e Controller, FIELDVUE DLC3010 Controller, and FIELDVUE DLC3100 Controller.
Pneumatics are still required to operate the valves, but the vented gas is further reduced, increasing pneumatic controller loop savings from $845 to $1,240 per year.
Zero venting with electric actuators
The authors describe a third option for further reducing emissions:
If sufficient power is available, pneumatic control valve actuators can be replaced with all electric actuators, such as the Fisher easy-Drive electric actuator shown in Figure 3. This type of actuator can be retrofitted to a number of different control valve brands and styles, and it offers a means to achieve zero methane bleed for the entire site.
Figure 3: The zero bleed Fisher easy-Drive 200L is an all-electric control valve actuator with built in positioner and a 0.75” stroke. It can be retrofitted to a number of 1” and 2” control valves from different vendors.
Reduced LDAR inspections
The new standards allow a producer to reduce inspection intervals if the percentage of devices exceeding 500 ppm emissions can be reduced below certain thresholds. One method to minimize seal leaks is to swap any troublesome packing with spring-loaded packing, such as the ENVIRO-SEALTM packing shown in Figure 4.
Figure 4: Live-loaded packing, such as ENVIRO-SEALTM packing, utilizes springs to maintain compression on the packing, helping to ensure the control valve seal leak rate remains below the LDAR action level with minimal adjustment or maintenance.
Evaluate your options
Emerson offers an Energy Responsible Tool, empowering users to compare existing instruments against low-bleed devices to determine the emission reduction and natural gas savings of various options. The tool is free and can be accessed at: http://www.fisher.com/energyresponsibletool/.
Conclusion
Brian and Lura finished their article with the following thought:
The latest methane reduction regulations need not be an onerous and expensive burden to energy producers. When the cost of recovered gas and/or carbon credits are considered, the replacement equipment can generate a quick ROI, even as it helps the site meet regulatory requirements.
Figures all courtesy of Emerson
About the Authors
Lura Parrent is an application engineer for Emerson specializing in Fisher control valves and instruments and is responsible for end users in the upstream oil and gas industry. Lura has been in her current role for two years since her graduation in 2018 from the University of Nebraska-Lincoln with a degree in chemical engineering.
Brian Van Vliet is part of an entrepreneurial team at Spartan Controls. He has worked with Spartan for over 15 years providing environmental solutions and improving field efficiencies for industries across western Canada. Brian received his Bachelor of Science in Mechanical Engineering (Co-op with Distinction) from the University of Alberta and lives in Calgary, Alberta.
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