In mature gas wells fluids (water and hydrocarbons) can accumulate in the well such that well bottom hole pressure is no longer high enough to lift the weight of the fluids in the well. This reduces or stops gas production. Methods used to restore gas flow include removing accumulated fluids using a sucker rod pump and remedial actions, such as soaping, swabbing and routine periodic venting the well to the atmosphere known as “blowing down the well.“ This is often referred to as well venting from liquids unloading.
Fluid removal operations, especially well blowdowns, cause VOCs and methane releases to the atmosphere. A properly automated plunger lift system can be designed and operated so that produced gas pressure is high enough for consistent injection into the sales line and eliminate venting to the atmosphere.
EDI Smart Well Automation at wellhead surface location.
The EPA in its white paper entitled “Oil and Natural Gas Sector Liquids Unloading Processes” stated that well unloading operations are VOC emissions source of concern. The paper lists plunger lifts as a method for reducing well venting from unloading operations.
Plunger lifts are widely used as an artificial lift method to enhance gas production, especially for high gas to liquid ratio wells. Plunger lift systems can increase production sent to sales and reduce methane and VOC emissions associated with blowdown operations.
The plunger lift’s purpose is to remove liquids from the wellbore so that the well produces at the lowest bottom hole pressure. The plunger can also lower liquid fallback and reduce scale and paraffin buildup.
The plunger lift uses the well’s gas pressure to push a column of accumulated fluid to the surface and out of the well. Plunger lifts use a plunger (aka, rabbit, piston or pig) to push the fluid column above it up the well tubing to the surface.
Plunger lift operation depends on the natural buildup of pressure in a gas well during the time that the well is shut-in. The well shut-in pressure must be greater than the sales line pressure to lift the plunger and liquids to the surface. The true objective of a plunger lift is to send the gas to the sales line – not vent natural gas to the atmosphere.
The EPA Gas STAR program document on Installing Plunger Lift Systems in Gas Wells gives the following typical steps for the operation of a plunger lift system:
- The plunger rests on top of the bottom hole bumper spring at the well’s base. As gas is produced up the well and to the sales line, liquids accumulate in the well bore increasing backpressure that reduces gas production.
- At a predetermined set point, the well is shut-in at the surface using an automatic controller. In older systems this was accomplished by a timer with a fixed cycle – regardless of well conditions.
- While the well is shut-in, the well bottom hole pressure increases due to accumulation of high pressure gas in the annulus between the casing and tubing. Once a sufficient gas pressure and gas volume is achieved, the plunger and liquid load are pushed to the well surface. In the newer automated systems, the amount of accumulated fluid in the hole is monitored based on the hydrostatic pressure in the bottom hole. Smart systems use real time well data on the weight of the accumulated fluid in the hole and the sales line pressure to cycle the plunger (rabbit) so that fluid is lifted and the gas pressure is high enough to “buck” the line pressure. RESULT = Gas is sent to SALES and gas is not vented to atmosphere like blowdown of a well.Control well fluid and pressure to ensure successful plunger run!
- The plunger arrives and is captured in the lubricator.
- The gas lifting the plunger then flows to the sales line.
- Once gas production drops to a set point, the automatic controller releases the plunger dropping down the tubing and inactive till the cycle begins again.
NOTE: Plunger lifts only reduce air emissions if the gas from the well are sent to the gathering or sales line and not vented to the atmosphere. Ensure lifting pressure exceeds gas pipeline pressure or use compression to increase pressure for injection into the pipeline.
Smart Well Automation
Smart automation of well operations for plunger lift equipped wells use monitoring and control as best practice to maximize gas production. These systems use satellite, cellular or radio communications for remote control of plunger lift systems. Monitoring and control can take place locally or from a desktop computer.
By automating the system, operating costs are reduced because operators can then focus their visits to the wells that require attention.
Smart well automation systems allow the following:
- Remote control of wells
- Event history tracking and graphing
- Pressure graphs
- Alarms for set points
- Email and text alerts
- Oil storage tank levels
Plunger Lift Advantages
- Cost-effective method to lift fluids from gas wells that increases gas production
- Reduces VOC and methane emissions and from well blowdowns
- Uses well’s energy and no external power source needed
- Lower capital cost versus installing beam lift equipment
- Well gas velocity can be very low with a plunger compared to wells without a plunger
- Using plunger lifts to inject gas into a low pressure pipeline or with compression can produce wells to economic depletion
- Lower well maintenance costs because periodic swabbing or well blowdowns are reduced or no longer needed
- Can reduce paraffin and scale accumulation in wells with such problems
- With EPA focus on ways to reduce venting of natural gas from wells and production facilities, plunger lifts, designed and operated correctly, can be a way to reduce venting of natural gas and increase production.
EDI (Electronic Design for Industry) has specialized in plunger lifts since 1980; they received their first patent for plunger lift designs in 1985. Their expertise and experience can help your company now with plunger lift and smart well automation needs. For more information contact Mr. Rich Wynn or Scott Baker at .