For many oil & gas producing sites, the traditional way to power valve actuators has been from the natural gas pressure from the well. The issue with this approach is the venting of methane into the atmosphere.
In an Oilfield Technology article, Switching on to Electric Control Valves’ Potential, Emerson’s Scott Losing and Andrew Prusha describe how electric valve actuators have advanced to replace pneumatic actuators driven by natural gas.
Scott and Andrew note the driving force behind a change in practice.
Recent government actions are driving major changes in wellhead instrumentation. In an effort to curb methane emissions, the US, Canada and many European countries have passed regulations that significantly impact field instrumentation activated by natural gas…
Options to replace natural gas-driven actuators include electric/electronic actuators, air compressors for compressed air substitution, or low-bleed actuator alternatives. Technology has advanced to support greater use of electric/electronic actuators.
Solar systems, batteries and small natural gas generators are becoming increasingly available — and the electrical efficiency of instrumentation is improving. When natural gas-powered pneumatic instruments are replaced with electric alternatives, methane bleed emissions are cut to zero.
Another critical advancement for change:
…is the introduction of powerful, low-cost electric drives that can be easily retrofitted to many existing control and on/off valves.
Not only does this electric approach eliminate methane emissions, but it also enables:
…profitable, advanced control strategies that we not easily implemented before these upgrades.
Scott and Andrew share several examples of how these advanced control strategies drive operational improvements. These examples include oil separator level controls, enhanced recovery methods, plunger lift controls, and rod lift “flumping” controls. I’ll share the oil separator level controls example and invite you to read the article for the other improvement opportunities.
An oil separator uses gravity to separate incoming well fluids into gas, oil and water.
An oil separator separates the three phases found in producing wells—oil, gas, and produced water. They describe its operation from this diagram.
…a liquid/vapour mixture enters the left side of the vessel and the liquids quickly disengage and fall out to the bottom of the vessel. The gas vapours continue across the top of the vessel and exit via overhead piping to downstream gas processing.
Water and oil can be separated from the process of oil floating on top of the water.
A transmitter detects the oil/water interface, and the water valve is modulated to keep the interface about halfway of the weir.
Another transmitter detects the oil level on the other side of the weir.
The oil level is kept high enough to block gas vapours from escaping through the oil line.
Electronically controlled valve actuators enable control performance improvements.
The valves can be programmed to open and close at varying levels and to operate continuously in between levels. This method results in tighter level control and more consistent oil flows, using the same basic control equipment.
Scott and Andrew cite a U.S. North Dakota producer who deployed electronic control valves and measured:
…reduced gas loss down the oil line by 80% and improved oil flow measurement accuracy by 5%, effectively increasing well production.
Read the article for the other examples of how electric actuators drive performance improvements. Visit the Fisher easy-Drive Electric Actuator page on Emerson.com for more on the products to drive improvements in sustainable operations.
