Installing Plunger Lift Systems In Gas Wells
Revenue from Increased Production
Nelson Price Indexes
In order to account for inflation in equipment and operating & maintenance costs, Nelson-Farrar Quarterly Cost Indexes (available in the first issue of each quarter in the Oil and Gas Journal) are used to update costs in the Lessons Learned documents.
The “Refinery Operation Index” is used to revise operating costs while the “Machinery: Oilfield Itemized Refining Cost Index” is used to update equipment costs.
The most significant benefit of plunger lift installations is the resulting increase in gas production. During the decision process, the increase in production cannot be
methodology for production varies methodology for
estimating this expected incremental depending on the state of the well. The continuous or non-declining wells is
relatively straightforward. In contrast, the for estimating the incremental production decline is more complex.
methodology for wells in
To use these indexes in the future, simply look up the most current Nelson-Farrar index number, divide by the February 2006 Nelson-Farrar index number, and, finally multiply by the appropriate costs in the Lessons Learned.
remove well bore fluids, acidizing to remove mineral scale and clean out perforations, fishing-out debris in the well, and other miscellaneous well clean out operations. These additional start-up costs can range from $700 to more than $2,600.
Operators considering a plunger lift installation should note that the system requires continuous tubing string with a constant internal diameter in good condition. The replacement of the tubing string, if required, can add several thousands of dollars more to the cost of installation, depending upon the depth of the well.
Estimating incremental gas production for non- declining wells. The incremental gas production from a plunger lift installation may be estimated by assuming that the average peak production rate achieved after blowdown is near the potential peak production rate for the well with fluid removed. A well log, like that illustrated in Exhibit 3, can be used to estimate the potential production increase.
In this exhibit, the solid line shows well production rate gradually, then steeply declining as liquids accumulate in the tubing. Production is restored by venting the well to the atmosphere, but then declines
again with reaccumulation of liquids. Note that production rate scale, in thousands of cubic feet
the per the
Exhibit 3: Incremental Production for Non-Declining Wells
Operating costs. Plunger lift maintenance requires routine inspection of the lubricator and plunger. Typically, these items need to be replaced every 6 to
12 months, per year. annually.
at an Other
approximate cost of $700 system components are
to $1,300 inspected
Step 3: Estimate the savings of a plunger lift. The savings associated with a plunger lift include:
Revenue from increased production;
Revenue from avoided emissions;
Additional avoided costs—well
reduced electricity costs, workover costs; and