Guidelines & Recommended Practices
Selection of Artificial Lift Systems
for Deliquifying Gas Wells
Prepared by Artificial Lift R&D Council
2.4g Soap Sticks
This section discusses the practical limits of soap sticks in terms of liquid
production rate, gas production rate, depth, pressure, temperature, etc. It
presents rough guidelines on the relative costs of soap sticks. Obviously
precise costs can not be given as they depend on many factors. It presents
rough guidelines on the relative life expectancy of soap sticks. Clearly, precise expectations can not be given as they depend on many factors.

Introduction
The purpose of introducing solid surfactants into the well bore is to improve the Turner-Coleman rate inexpensively. Soap sticks accomplish
this but the benefit can be temporary. The surfactant mixes with the produced water down-hole and changes the surface tension of the water
molecule. This reduction of surface tension between molecules allows
the water droplets to break-up into ever-finer droplets. Water, in a mist
condition, will migrate to the surface with the up-flowing gas stream more
easily than larger, heavier droplets.
A falling soap stick will encounter and mix with the water that is nearest
the top of the water column. Typically the upper portion of the water column is a burst of activity as gas bubbles churn through to the surface.
This stirring effect, combined with the increased temperature down-hole,
promotes the dissolution of the solid surfactant. One soap stick will effectively treat one barrel of water, although the tubing can contain much
more water than that.
The weight of the standing water column in a gas well reflects the pressure of the near well-bore formation. Removing a portion of this water
from the top of the water column by the use of solid surfactants means
that the available pressure down-hole can, alone, burp-up an additional
amount of water. At this point, some wells will begin logging-off again
whereas other wells will continue to un-load. One soap stick therefore
can unload from 1 to 5 barrels depending on the well’s bottom-hole
pressure and inflow characteristics.
Selection of Artificial Lift Systems for Deliquifying Gas Wells

Page 2
Practical Limits
-
Depth limits
There is not a finite depth limitation with the use of soap sticks other than maximum temperature. This fact makes solid surfactants an
attractive option for deeper completions.
-
Size limits
Soap sticks are made as small as 5/8” diameter by 10” long
(16mm/25cm) for use in velocity strings. The largest soap sticks are
2” (50mm) in diameter for use in casing-only completions to delay
the requirement for tubing installation. The most common soap
sticks are 1.25” diameter by 16” long (32mm/40cm).
-
Pressure limits
Soap sticks are immune to increases in pressure and may be used
in high pressure applications. The exception is the less popular gel
stick, as produced by a few manufacturers. If the gel jacket contains an air pocket, the stick can distort under pressure causing the
stick to hang-up in the tree.
-
Temperature limits
Soap sticks may be purchased for higher temperature dissolution or
alternately for low temperature dissolution. Using surfactants at extreme temperatures, however, can cause a degeneration of the
chemical components used in the manufacture of the surfactant.
The variables involved in the decision to employ soap sticks are; a)
produced water volume, and b) water column surface temperature,
not bottom-hole temperature. This is because a solid surfactant,
used correctly, does not need to migrate deeply into the water column (see introductory paragraphs). Consult with reputable surfactant manufacturers for definitive temperature limitations.
-
Packaging and handling
A typical soap stick is a liquid surfactant in a chemical binder. This
binder gives the soap stick a hard wax-like texture. A ‘gel-stick’ is a
near-liquid surfactant in a gelatin sleeve giving the stick a higher ratio of active ingredients. The latest type of stick is known as the paper-shell stick. This surfactant is contained in a water soluble paper
shell. The paper shell remains clean and prevents losses due to
breakage.
Selection of Artificial Lift Systems for Deliquifying Gas Wells
-
Page 3
Rate limits
Concerning low flow rate wells; solid surfactants will lower by 5% to
20% the Turner-Coleman rates necessary to produce the well after
other variables are met. A weaker well or a loaded well can be
shut-in for an extended period to increase the flow rate for unloading liquid from the tubing. For higher producers, the maximum flow
rate at which a soap stick will fall is approximately 400 MCFD in 23/8 tubing and approximately 600 MCFD in 2-7/8 tubing. When a
well flows above these rates, the well should be shut-in for 5 to 10
minutes to allow the stick to fall into the water column.
-
Produced water and hydrocarbons
Foamer formulations are specific for the presence of fresh water or
water with high chloride count. Another variable is the presence of
oil or condensate. The Operator should inform the surfactant supplier about the water test report for the best result. Typically the oil
cut can be as high as 50% for the extended, continuous use of surfactants. The maximum amount of condensate is 30% when using
surfactants on a daily basis such as with an automated launcher.
These upper limits do not apply for the occasional use of surfactants.
-
User guidelines for vertical completions
For least cost and best results, vertically completed wells should be
treated with one soap stick at a time and re-charged with another
stick when the flow rate trends downwardly toward critical (at approximately 1.2 times the Turner critical velocity). The exception to
the minimum stick rule is larger tubing diameters and greater water
volumes. The Operator should review the production records to determine when the effectiveness of a stick drop has expired (typically
6 to 12 hours later, frequently longer). Another stick drop should be
scheduled prior to that time to maintain a more uniform flow rate.
Shutting-in the well during stick fall time is the exception, not the
rule, in a vertical completion.
-
User guidelines for horizontal completions
Horizontal completions differ from vertical completions. A horizontal
completion should be treated with 2 to 4 sticks and then shut-in for
an extended period. Once the flow time begins, it should be sufficiently long to re-charge the tubing with water.
Selection of Artificial Lift Systems for Deliquifying Gas Wells
-
Page 4
Other chemical sticks
The ‘foamer’ stick is the most common chemical stick for dewatering gas wells. Other sticks are manufactured for controlling
corrosion, paraffin, scale, H2S, and salt bridges. An acetylene stick
is available to create a gas release for thoroughly liquid-loaded
wells. Research is ongoing to create an effective foamer for oil laden formations

-
Limits with sand, corrosion, erosion, H2S, CO2, etc.
-
Power requirements
-
Operating requirements
-
Maintenance requirements
Cost Guidelines
-
CAPEX
The easiest method of introducing soap sticks into the well bore is
by a submarine hatch arrangement of ball valves, i.e. two ball
valves above the tree cap separated by 18”of pipe at a cost of
about $600 in 2007 dollars. A more expensive method is to employ
an automatic soap stick launcher at about ten times the expense of
the homemade launcher. The extra expense can be justified if a
production increase is the result.
-
OPEX
The on-going cost of de-watering a gas well with solid surfactants is
the expense of the soap stick. Soap sticks are purchased at supply
stores from $5 to $10 depending on formulations. Volume purchases reduce the cost per stick. An additional reduction in operating
expense can be realized by introducing the minimum number of
sticks into the well at a time. See User Guidelines.

R&M
Life Expectancy Guidelines
-
Infant mortality (early time failure)
Selection of Artificial Lift Systems for Deliquifying Gas Wells
-
Page 5
Normal operating life
The failure of soap sticks in the de-watering process falls into two
categories. The first is an incorrect formulation for the liquids being
produced, for example an excess of liquid hydrocarbons or excessive chlorides. The second cause of failure is insufficient flow rate.
Surfactants will reduce the Turner-Coleman rate required by a limited percentage only. See Rate Limits.

Soap Sticks vs. Competing Methods of Artificial Lift
-
Soap sticks
Use of soap sticks is the least expensive artificial lift technique requiring minimal Capex. The disadvantage is that the total amount of
fluid removable by this method peaks at about 50 to 100 BPD. Another disadvantage is the Opex for the personnel required to deliver
soap sticks into the well bore.
-
Plunger lift
The cost of plunger lift is on par with the use of automatic soap
stick launchers and plunger lift is a preferred method when liquid
hydrocarbons vs. water exceed the limitation outlined above.
Plunger lift is equal to solid surfactants in removing a maximum
amount of fluid, i.e. 50 to 100 BPD. Plunger lift requires a more
skilled operator, however.
-
Capillary string
Capillary strings are approximately 30 times more expensive than a
homemade stick launcher and three times the expense of plunger
lift or automatic stick launching. The surfactant from a capillary system is discharged at the perfs, where temperature issues might exist. The advantage to the cap string is the duration between recharge cycles. The Opex disadvantage is the cost of the liquid surfactant per MCF increase.
-
PCP, ESP, Rod pump
Although more expensive, the advantage of a PCP or a rod pump is
in the total volume of fluid removed. Each technique will exceed the
volume of fluid remove by surfactants by one order of magnitude.
The disadvantage is the CAPEX and OPEX.
Selection of Artificial Lift Systems for Deliquifying Gas Wells
Page 6

Recommended Practices for Installation, Operation, and Maintenance of Soap Stick Systems

Recommended Practices for Automation, Surveillance, and Optimization of Soap Stick Systems