Installing Plunger Lift Systems In Gas Wells
for an unloaded well producing 100 Mcf per day, the gas vented to the atmosphere can be estimated at 2 Mcf per hour of blowdown.
Exhibit 5: Example—Estimate Avoided Emissions from Blowdowns
Avoided Emissions per Hour of
= (0.56251 x Sustained Daily Flow
Blowdowna Avoided Emissionsb
Annual Value of Avoided Emissionsc
Rate) / 24 hrs/day
= (0.5625 x 100 Mcfd) / 24 = 2 Mcf per hour of blowdown = 2 Mcf x 12 x $7.00/Mcf = $168 per year
Recommended methane emission factor reported in the joint GRI/EPA study, Methane Emissions From the Natural Gas Industry, Volume 7: Blow and Purge Activities (June 1995). The study estimated that at the beginning of a blowdown event, gas flow is restricted by fluids in the well to 25 percent of full flow. By the end of the blowdown event, gas flow is returned to 100 percent. The integrated average flow over the blowdown period is 56.25 percent of full well flow. a
Assuming a sustained daily production rate of 100 Mcfd. Assuming 1 blowdown per month lasting 1 hour.
This method is simple to use, but anecdotal evidence
suggests that it produces estimates of emissions avoided that are unrealistically
methane low. For avoided
Avoided well treatment costs are applicable when plunger lifts replace beam lifts or other remedial techniques such as blowdown, swabbing, or soaping. Reduced electricity costs, reduced workovers, and recovered salvage value are only applicable if plunger lifts replace beam lifts.
costs. Well treatment treatments, microbial rods and scraping the shallow 1,500-foot wells
minimum of $13,200 per well per year. costs to reduce paraffin have been shown to
Microbial be $6,600
and removal of
costs (inhibitors, solvents,
treatments do Each of these
treatment costs increases as the severity or paraffin increases, and as the depth increases.
well per year (note that address the fluids influx
emissions from blowdowns, see the Appendix.
Reduced electricity costs compared to beam
Given the high degree of variability in emissions
based on well measurement
determining avoided emissions.
because battery avoided
most controllers are solar-powered with backup. Exhibit 6 presents a range of electricity costs reported by operators who
have installed plunger lifts. operation, avoided electricity to $7,300 per year.
Assuming costs range
365 days of from $1,000
Avoided emissions when replacing beam lifts. In cases where plunger lifts replace beam lifts rather than blowdowns, emissions will be avoided due to reduced workovers for mechanical repairs, to remove debris and cleanout perforations, to remove mineral scale and paraffin deposits from the sucker rods. The average emissions associated with workovers have
Reduced workover costs compared to beam
Workover costs associated with reported as $1,300 per day.
beam lifts have While typical
Exhibit 6: Electricity Costsa Avoided by Using a Plunger Lift in Place of a Beam Lift
been reported the frequency range from 1
as approximately 2 Mcf per workover;
workovers has been
reported to well-specific
characteristics such as flow during duration of workover, and frequency of avoided emissions can vary greatly.
Avoided Costs and Additional Benefits
Avoided costs depend on the type of liquid removal systems currently in place, but can include avoided well treatment, reduced electricity costs, and reduced workover costs.
Motor Size (BHP)
Operation Cost ($/day)
Electricity cost assumes 50 percent of full load, running 50 percent of the time, with cost of 7.5 cents/ kWh. a