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Guidelines
for Deliquefying Gas Wells
This article presents insights on common
artificial lift systems, but more importantly describes an
ongoing industry effort to develop proven deliquification
guidelines. The guidelines, which are online within the
Artificial Lift Research & Development Council’s (ALRDC)
website (www.alrdc.com), have four sections.
1st Section:
Presents guidelines for producers and the service sector for
creating an optimum artificial lift selection process. Many
issues influence selecting the “best” process and guidelines
can vary for different companies, for onshore versus
offshore, domestic versus international, etc. Economics,
personnel and availability are factors.
2nd Section:
Presents the fundamentals of gas well deliquification and
presents separate guidelines for all 15 forms of artificial
lift with the guidelines for each form developed by a
separate team of experts.
3rd section: Presents guidelines
for selecting the most appropriate system for a given
well/field.
4th Section: Presents guidelines for
installation, maintenance and operation over the long term.
It also covers automation, surveillance and optimization
issues.
Since guideline development is ongoing, if you have
something you wish to contribute, contact Cleon Dunham at ALRDC (ph 512-732-0545, email
cleon@oilfieldautomation.com).
Excerpted from “Guidelines Help Operators Select Artificial
Lift Systems for Deliquefying Gas Wells,” The American Oil &
Gas Reporter, June 2008, pp. 93-99. |
Another Look at Deliquefying Gas
Wells
Considering the prior “guidelines”
article, excerpting this article on the same topic seemed to
be an obvious choice. Rather than repeat the need and
plethora of solutions, this focuses on just a few
innovations discussed.
Velocity strings. With velocity
strings there is a tradeoff with increased friction, plus
the optimum size is continually changing. Tubing-flow
control allows liquids to be produced up the tubing at the
minimum gas velocity while additional gas is produced up the
tubing/casing annulus through a control valve.
Solar-powered, continuous-fiberglass-rod pumping unit. Often
liquid volumes in gas wells are very low. BP has piloted a
system powered by 700-W solar panels that can lift five (5)
barrels of liquid per day from 1,300 ft with a 1/3-hp motor.
Near-wellbore deliquification. Typically, the end of tubing
is installed above the perforations, which means that
accumulated liquids could be pulled by capillary pressure
back into the formation, which would increase water
saturation and decrease gas relative permeability. Research
is ongoing about this phenomena and how much it might be
reversible. There are documented examples seeming to support
the model. If the effect is significant but not reversible,
then tubing location below the perfs should be practiced
during both initial natural flow and subsequent artificial
lift.
Excerpted from “Getting the Last Gasp: Deliquification of
Challenging Gas Wells,” Journal of Petroleum Technology,
July 2008, pp. 79-81.
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Alternatives for
Formulating Low-Density Cements
Alternatives for Formulating
Low-Density Cements Many situations require low-density
cements. Conventional cement slurries weigh between 15.6 -
16.4 ppg (pounds per gallon). Density can be reduced as low
as 5 ppg through using different alternatives alone or in
combination. Water extension: Affordable, but it degrades
cement performance in proportion to the amount of dilution.
Reduction below 11.5 ppg severely degrades performance.
Foamed: Can reduce density to about 12 ppg. Experience
indicates that the base slurry should be foamed no more than
25%. Requires the right equipment and careful control to
maintain homogeneity.
Hollow beads: Quite low densities
can be achieved using low-specific-gravity hollow ceramic
beads (cenospheres). Although inexpensive, cenosphere
quality can vary widely. The cenosphere tend to
size-segregate during transport, and they are affected by
pressure.
Glass microspheres: Smaller than ceramic
cenospheres, more uniform, and they don’t experience
segregation problems during transport. They also handle
pressure better. Equipment is simpler and less costly
than for foaming. Using glass bubbles alone, a slurry of
very low density can be achieved.
Excerpted from “Alternatives in Low-Density Cement
Formulation,” Hart’s E&P, May 2008, pp. 103-105.
Foamed Cement in
Woodford Shale Wells Increases Production, Improves Frac
Success
Focused multistage fracture treatments are central to
success of Woodford Shale horizontal completions.
Maintaining zonal isolation between stages is critical. As
of early 2008, there is a significant database from which to
draw conclusions. There were 116 horizontal production
casing strings cemented with conventional slurries, and 229
cemented using nitrogen-foamed cement. Of the 105 wells
where production data were available, wells cemented using
foamed cement averaged 28% higher peak 30-day gas
production. From a fracturing standpoint, foamed cement
increased fracture initiation and successful job placement
to more than 96%, whereas conventionally cemented wells were
successful in only 80% of the planned stages. (continued
on next page) |
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