Guidelines & Recommended Practices
Selection of Artificial Lift Systems
for Deliquifying Gas Wells
Prepared by Artificial Lift R&D Council
1.8 Know the Performance of Your Wells
This describes the information you must know about the performance of your
wells; static fluid level, operating fluid level, inflow performance relationship.
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Fluid level in the casing
For several types of artificial lift systems, e.g. most pumping systems, it
is important to know the fluid level in the production casing. This can
give an indication whether the well is “pumped off” and it can be used
to calculate the flowing bottom-hole pressure when the well is producing and the static bottom-hole pressure when the well is off production.
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Fluid level in the tubing
For some types of artificial lift systems, e.g. plunger lift, soap sticks,
and batch chemical treatments, it can be useful to measure the fluid
level in the tubing. This can be used to determine plunger fall velocity,
and if the plunger is falling all the way to bottom. It can be used to determine the fall velocity of soap sticks and how far they fall in the tubing.
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Static bottom-hole pressure
The current static bottom-hole pressure (SBHP) must be known to determine the well’s inflow performance. See Section 1.6, Know Your
Reservoirs, for a discussion of this variable..
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Flowing bottom-hole pressure
The current flowing bottom-hole pressure (FBHP) must be known to
determine the well’s inflow performance. See Section 1.6, Know Your
Reservoirs, for a discussion of this variable.
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Inflow performance relationship
The current inflow performance relationship (IPR) must be known to
determine the potential for additional production. See Section 1.6,
Know Your Reservoirs, for a discussion of this relation.
Selection of Artificial Lift Systems for Deliquifying Gas Wells
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Track changes in inflow and out flow performance
A useful well surveillance tool can be to track (plot) well inflow performance and outflow performance vs. time. Changes in inflow or outflow
performance can give indications of problems with inflow due to wellbore problems, or outflow due to liquid loading or other causes.
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Decline curve, decline analysis
It is important to keep track and analyze the plot of production rate vs.
time or cumulative production and perform decline curve analysis.
This can be used to determine if the well is declining normally or if it is
experiencing abnormal decline which may be caused by the onset of
liquid loading or an increase in the degree of liquid loading.
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P/Z plot
The P/Z plot is one way to analyze gas well performance. A detailed
discussion of this plot, how to generate it, and how to use it is included
in an annex to this Recommended Practice.
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Cumulative production
It is important to know the cumulative production and to plot this vs.
time and vs. static reservoir pressure. See Section 1.7, Know Your
Wells.
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Estimated ultimate recoveries
One use of the plot of cumulative production vs. time and vs. pressure
is to estimate the ultimate recovery of gas that can be recovered from
the reservoir before the final abandonment pressure is reached. See
Section 1.6, Know Your Reservoirs.
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Production analysis
Production analysis can be performed with tools like Topaz, RTA (rate,
time, pressure relationships), etc. to estimate drainage shapes, production capacities, etc. See Section 1.6, Know Your Reservoirs.
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Artificial lift performance indicators
Artificial lift performance indicators can be useful tools in spotting problems with individual wells or groups of wells. The method for calculating artificial lift performance indicators is different for each type of arte-
Selection of Artificial Lift Systems for Deliquifying Gas Wells
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rials lift. These are described in an annex to this Recommended Practice.
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Monitor pressures and rates
Another useful surveillance approach is to monitor and plot pressures,
rates, fluid levels, performance indicators, etc. vs. time. This can be
provided by any SCADA system.
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Proper procedures for collecting good data
Effective production surveillance requires use of proper measurements, systems, and procedures. These are discussed in an annex to
this Recommended Practice.