# Presentation: 772816

## Installing Plunger Lift in Gas Wells

**Lessons Learned**
** ****from Natural Gas STAR**
**Exploration & Production, **
**Gulf Coast Environmental Affairs Group, **
**American Petroleum Institute  and**
**EPA’s Natural Gas STAR Program**
**June 19, 2003**

**Notes:**
Mature gas wells often experience down-hole liquid build-up that suppresses gas pressure and flow rates
A common remedial action is to periodically “blow” the produced gas to the atmosphere to expel these liquids (water and hydrocarbon liquids)
This practice vents significant amounts of methane to the atmosphere, and wastes saleable gas production
This presentation describes Natural Gas STAR Partner experience with a cost effective, reliable alternative called “plunger lifts.”

## Installing Plunger Lift in Gas Wells

- Methane Losses
- Methane Recovery
- Is Recovery Profitable?
- Industry Experience
- Discussion Questions

**Notes:**
The presentation will discuss the nature of the problem with common methods of dealing with accumulated gas well liquids
The methane emission reduction potential and accomplishments for using plunger lift technology
How the technology works; what it does; the benefits
Shows how partners can determine if this technology is profitable for them
Provides actual industry experience with plunger lift installations
Closes with Lessons Learned from this technology and discussion questions

## What is the Problem?

- There are approximately 316,000 condensate and natural gas wells (on and offshore) in the U.S.
- Accumulation of liquid hydrocarbons or water in the well bores of gas wells reduces and can halt production
- Common practices to temporarily restore production vent significant quantities of methane

**Notes:**
There are approximately 316,000 gas wells in the U.S.
Accumulation of liquid hydrocarbons or water in the well bores of gas producing wells acts as a cap exerting a hydrostatic head downward, reducing production. 
One barrel of water will stand 258 feet in 2-3/8 inch tubing, exerting a back pressure of 110 psi on the gas formation
gas production rates are typically restored by “blowing” the well, which entails releasing a high volume of gas for a short period of time to “blow” the accumulated liquid from the well tubing.
In addition to wasting gas, this practice is very inefficient, as liquids coat the tubing walls, allowing gas to bypass much of the accumulated liquid.

## Methane Emissions

- By venting, or “blowing” the well to the atmosphere, a high volume of gas entrains accumulated liquids to the surface
- Methane is released to the atmosphere along with the gas
- On average, 50 to 600 Mcf of methane per well may be emitted each year
- To date, about 6 Bcf/yr of gas is being saved with plunger lift installations

**Notes:**
On average, 50 Mcf of gas per well is vented to the atmosphere in attempts to blow out liquids and maintain well productivity.
Some partners reported venting an average of 600 Mcf per year
Individual wells, as much as 1.6 MMcf/yr
Depends on the liquid buildup in the specific well.
To date, 120,000 plunger lift installations are estimated to save 6 Bcf/yr

## How Can Plunger Lifts Reduce Methane Emissions?

- Plunger lifts automatically produce liquids without blowing the well to the atmosphere
- Gas pressure stored in the casing annulus periodically pushes the plunger and liquid load from the well bottom to surface vessels
- Wells with the right combination of shut-in pressure, depth and liquid accumulation are kept productive without operator attention
- Other wells can use injected gas lift more efficiently with a plunger lift system

**Notes:**
Plunger lifts, operating solely from the well’s own energy, push accumulated liquid to the surface without blowing the well.  
The plunger falls to the bottom of the well, where the fluid is picked up by the plunger (acting as a swab) and is pushed to the surface with a liquid load 
This process also keeps the tubing free of paraffin, salt, or scale build-up. 
With continual removal of all produced liquids, there is less fluid weight on the formation, increasing the well’s productivity.

As discussed later, wells must have the right combination of pressure, liquid accumulation and geometry to work successfully with plunger lifts
Wells with too low pressure can employ plunger lifts to make externally introduced gas lift methods more efficient at removing liquid buildup

## Plunger Lift Schematic

**Notes:**
The technology is easily retrofitted onto the gas well
Five primary components:
plunger (several types)
down-hole spring stop
surface plunger catcher
surface valves and bypass line
solar powered electronic controls
Plunger drops by gravity to bottom stop
can fall at 1000+ fpm in gas
Gas is produced to sales line while liquids accumulate down-hole
Production is shut-in by timer, causing gas volume and pressure to build in the casing annulus
Production is opened through a bypass liquid trap, with the surge from the casing annulus lifting the plunger and liquid load to the surface
Plunger is caught, and gas flow diverted to sales line through normal outlet
Plunger is released and drops back to the bottom for another cycle
Plunger can cycle up to 100 times a day, lifting 1/2 to 2 barrels liquid per cycle

## Overall Benefits

- Higher gas production
- Reduced methane emissions
- Lower capital cost
- Lower well maintenance cost
- Extends the life of wells
- Removes scale, salt, paraffin

## Decision Process

- Determine if a plunger lift is
- technically feasible for the well

-  Determine the cost of a
- plunger lift

- Estimate the savings achieved by
-  plunger lift installation:
- capital and operating costs
- increased production value
- gas savings
- avoided well treatment costs
- salvage value
- reduced workover/electricity costs

- Is  a plunger lift
- cost-effective?

- Compare overall costs and benefits of
- traditional remedial techniques vs. plunger lifts

**Notes:**
Decision process
Is the technology feasible on a specific well?
What does the plunger lift facility cost?
What are the savings from alternative methods?
Economically evaluate the change
Compare economics measures with company criteria
Plunger costs must include the start-up costs as well as the facility and operating costs

## Plunger Lift Applications

- Plunger lifts are a long term solution
- Common plunger lift applications include
- Wells with gas-to-liquid ratios of 400 scf/bbl per 1,000 feet of depth
- Wells with shut-in pressure that is 1.5 times the sales line pressure
- Gas wells with coiled tubing
- Wells in need of paraffin and  scale control
- Oil wells with associated gas
- Using plunger lift when venting to the atmosphere
- Wells with shut-in pressure that is 1.5 times atmospheric pressure

**Notes:**
Wells with any of the following characteristics may be candidates for plunger lift systems:  
(1) blow downs are required to restore production; 
(2) formation gas and liquid ratio at least 400 cf of gas per barrel per 1,000 feet to be lifted; 
(3) shut-in wellhead pressure of at least 1.5 times sales line pressure; 
(4) wells producing by heading cycle with decreasing production rates; 
(5) paraffin, salt, or scale problem wells; 
(6) heavily deviated wells; 
(7) remote wells; or 
(8) marginal wells using a pumping unit.    

## Plunger Lift Costs

- Two elements: facilities and set-up costs
- Total costs range from $1,500-$6,000
- Largest variability is in set-up costs
- Tubing gage: check for obstructions/drift
- Broach to assure free movement
- Set/check depth of plunger stop bumper
- Swab to allow plunger to surface reliably

**Notes:**
Plunger lifts typical cost  
$5,000 per installation, including installation
Tubing gauge to check for obstructions and drift
Broach same size as plunger to assure free movement
Set/check depth of plunger stop bumper
May have to swab well up to several days before plunger will surface reliably
Annual maintenance costs of $500 to $1,000 (for replacement plungers).
Beam pump replacement includes significant salvage value, some gas emissions savings, often significant production increases.

## Avoided Emissions

- Estimating gas vented to expel liquids
- GRI studied more than 103,000 blowdown events
- 41% of the 6387 wells analyzed required liquid unloading
**Frequency ranged from once-per-year to once-per-day, averaging 40 times per year**
**Methane content was 78.8 mole %**** **
- ExxonMobil averaged savings of 640 Mcf/yr/well for 19 plunger lift installations in Big Piney, WY
- A conservative estimate is the well volume at shut-in pressure
- 0.37x10-6 x ID2 x Depth x Pressure x Vents/yr (Mcf/yr)
- 610 Mcf/yr for 8 inch, 10,000 ft well at 200 psig shut-in pressure with monthly venting

## Increased Productivity

- Using a well production plot, assume plunger lift can maintain peak average production rate

**Notes:**
Using well production plot, assume a plunger lift well be able to maintain the average peak production rate.
By inserting a line across the peak production rates, the area below the line can be conservatively valued as potential production with a plunger lift.
Areas below the line and above the production curve can be summed to estimate the gas production increase using plunger lift.
The curve on the right third is the plunger lift performance.

## Additional Benefits: Plunger Lift Replaces Beam Lift

- Avoided well treatment
- Chemical treatments (solvents, hot fluids, dispersants, surfactants, etc.) = $10,000/yr
- Microbial cleanups = $5,000/yr
- Avoided workover costs
- Decreased need for remedial operations average = $12,000 to $30,000 three times in 10 yrs

**Notes:**
Well treatment costs include chemical treatments and microbial cleanups.  
Chemical treatment costs (inhibitors, solvents, dispersants, hot fluids, crystal modifiers, and surfactants) are reported at a minimum of $10,000 per well per year.
Microbial costs to reduce paraffin have been shown to be $5,000 per well per year.  Microbial treatments do not address the fluids influx problem.
Each of these treatment costs increase as the severity of the scale or paraffin increase, and as the depth of the well increases.

Reduced workover costs increase the economic return.  Commonly, at least three remedial treatment have to be performed on a well over a 10 year period, at a total workover cost of $12,000-$30,000.

## Economic Analysis

**Two Options for continuously unloading a well**

**Notes:**
Starting with temporary solutions (well venting, soaping)
Two alternative longer term approaches: Beam Lift and Plunger Lift
Beam Lift
Significant electrical power and chemical for paraffin/scale control
Substantial O&M costs
Assuming same gas emissions and productivity improvement benefits
Plunger Lift pays out in 1 month
Beam Lift pays out in 14 months
Gas emissions and productivity factors would further favor Plunger Lift option

## Partner Reported Experience

- Partners report methane reduction of 10 -1,650 Mcf/yr per well
- Past emission reduction estimates for 120,000 wells using plunger lifts is 6 Bcf/yr or $18 million/yr
- Future emission reduction potential estimated to be 1-5 Bcf/yr for 100,000 additional wells

## BP

- Midland Farm Field, replacement of beam lift, rod pump well production equipment with plunger lifts
- Initial decision based on paraffin blockage
- Installation costs = $10,000 /well
- Avoided costs of electricity, workover, and paraffin control = $20,000 /well/year
- Increased production = $22,548 /well/year
- Due to success, 190 plunger lifts units have been installed at other locations

## ExxonMobil E&P U.S.

- Plunger Lift Installation Program at Big Piney, Wyoming
- Between 1995 and 1998 installed 23 plunger lifts (19 during first 3 years)
- Total installation costs = $115,000
- Annual emissions reduction = 14,720 Mcf
- Average annual value = $44,160 (at $3/Mcf)
- Program continues installing plunger lifts

## Annualized Reduction of Methane Emissions

**Well Number**

**Annualized Reduction (MCF)***

***Total Annualized Reduction = 12,166 Mcf/yr (640 Mcf/yr/well)**

**Notes:**
These are the 19 gas wells cited in the Mobil Big Piney case study
The program is continuing to install plunger lifts in this field

## Lessons Learned

- Most remedial actions (many of which can be replaced by plunger lifts) are costly, repetitive, and lead to excessive gas emissions
- Plunger lift installations reduce the amount of remedial work needed throughout the lifetime of the well, and the amount of methane releases

## Lessons Learned

- An economic analysis of plunger lift installation should include incremental boost in productivity and associated extension of well life
- Plunger lift installations can offer quick paybacks and high return on investments

## Discussion Questions

- To what extent are you implementing this technology?
- How can the Lessons Learned study be improved upon or altered for use in your operation(s)?
- What are the barriers (technological, economic, lack of information, regulatory, etc.) that are preventing you from** **implementing this technology?