403
19
Foamers for Gas Well
Deliquication
19.1 INTRODUCTION
Liquid buildup in gas wells causes an additional back-pressure that can reduce gas productivity and,
in worse cases, stop production completely. Gas well deliquication is the subject of its own annual
European conference, and the reader is encouraged to browse the lists of presentations for other
information not provided here.
1–3
Besides mechanical techniques, a well-known chemical method to
remove the liquid (usually water) is to inject a foaming surfactant.
4–8
The surfactant is injected at the
bottom of the well, where it mixes with the liquid and gas, lowering the surface tension and forming
a foam of lower density than the bulk liquid, which can then be produced from the well.
9
The sur-
factant can be applied as a liquid concentrate, either continuously or batchwise, or it may be applied
as “foam sticks.” The latter is more common for low-volume gas-producing wells: the surfactant is
compounded within a wax “candle,” which is simply lowered down the well. The use of foaming
surfactants to unload liquid in gas wells is very common. About 40% of gas wells worldwide suf-
fer from liquid buildup and are therefore producing at below optimum rate. Most deliquiers are
designed for use in gas and gas condensate wells. Few products are available for foaming crude
oil. General test methods for foamers have been reported using model surfactants.
7,10
This usually
involves measuring the dynamic surface tension as well as foaming properties in customized rigs.
Laboratory testing of a wide range of crude oils and water cuts have led to the development of a new
foamer that has been eld-trialed successfully.
11
19.2 PROPERTIES AND CLASSES OF FOAMERS
A variety of surfactants, anionic, cationic, zwitterionic, and nonionic, can be used, with varying
properties, but they should not damage the reservoir or cause emulsion problems if there are liquid
hydrocarbons present.
12
Other factors to consider include
Cloud point issues at high temperature and/or high salinity
Foaming tolerance to liquid hydrocarbon (condensate)
Degradation at elevated temperature
pH dependency
Ease of winterization
Some surfactants also have the benet of corrosion inhibition properties, although specic cor-
rosion inhibitors and other chemicals, such as scale inhibitors, can be added also if required.
13,14
Typical foaming surfactants are α-olen sulfonates, alcohol ether sulfates, and betaines, the latter
two categories being more biodegradable.
15
Organic solvents are often used to improve secondary
properties such as pour point, viscosity, and/or pumpability of the foamer formulations. Traditional
foaming surfactants tend to be ineffective as the condensate-to-water ratio increases.
16
A novel
foamer specically designed to unload condensate from wells has been reported.
17
Noncorrosive foamers have been reported.
18
They were developed to tolerate high temperatures,
moderate amounts of oil, condensate, corrosion inhibitor, and clay solids. They are not affected
by water salinity, and, at the same time, are compatible with produced water. It has been used

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