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Packers:
General Information
A packer is an expandable plug used to isolate sections in a well or borehole.
Baski Inc. manufactures inflatable packers for a variety of
applications, including pumping, injection, hydrofracturing, grouting,
flow control, testing, and sampling.
The inflatable packer has significant advantages
compared to
other packer designs which include:
• High pressure rating and expansion
ratio.
• Minimal outside diameter and large interior
diameter.
• Long sealing section that conforms to uneven
sides in a borehole.
Our patented packers are available for:
• Borehole sizes ranging from 2" to 30" (50 to
760 mm).
• Pressure ranges from 50 to
10,000 psi (3 to 700 bar).
Furthermore, we provide our
customers with a wide selection of metal and elastomer combinations for
custom
packers. Baski Inc. is particularly noted for providing custom-designed
packer assemblies for unique applications. |
Our most popular products
include:
Medium-duty SE Packer:
sliding-end packer for a wide range of
hole sizes and depths.
ReFlex™ Packer:
Cost-effective fixed-end packer with a fully
reinforced element.
Fracker: High-pressure,
sliding-end
packer for hydrofracturing applications.
New
products derived from our ongoing custom products
business include a heavy-duty 15-inch packer, and packers
for N-size (3-inch) and H-size (3.78-inch) core holes.
Please call us for more
information on
these.
For more general information about packers, please read the following
sections
about packer types, components,
specifications, and typical
applications. |
INFLATABLE
PACKER TYPES:
Sliding-end
Packer
This
type of
packer allows the element gland to slide on one end. As the element
diameter increases during inflation, the packer construction which
incorporates an O-ring seal allows one end of the element to move (or
slide) on the pipe base. The sliding-end packer is recommended for
open borehole or high pressure applications where the
differential pressure between the top and bottom of the packer ranges
from 100 to 5,000 psi. Also, the fully-reinforced element
offers high expansion ratios.
Fixed-end
Packer
A fixed-end packer has both of the rubber element ends fixed to the
pipe mandrel. The element can be one of three styles: non-reinforced,
partially-reinforced, or fully reinforced. Non-reinforced or "balloon"
type packers can easily fail due to element extrusion into open
borehole
fractures or into the annular area between the packer ends and the
casing or
borehole. Partial reinforcement at the ends of the element prevents
extrusion
into the annular area near the packer ends, but the element can still
extrude
into borehole fractures. In 1993, Baski Inc. introduced the fixed-end ReFlexTM
packer with a fully-reinforced element to prevent extrusion problems.
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INFLATABLE
PACKER COMPONENTS:
Pipe Mandrel
Pipe base upon which the packer is built.
The pipe's
inside diameter provides the space necessary for tubes, wires, hoses,
or other feed-throughs and pumping injection access. Pipe sizes range
from 3/8 to 10 inch and larger.
Reinforced
Rubber Element
Outer
covering that is mounted on the mandrel and inflated to change the
packer's outer diameter. Standard elements are constructed of natural
rubber with high-strength reinforcing such as Kevlar (DuPont). After
the element seals against the borehole, fluids can only move from one
end of the packer to the other via pumping through its center.
Inflation port
Fitting on end of packer that allows gas, water
or a solidifying liquid
to enter between the element and mandrel to expand the rubber.
Connectors
Threaded, metal end-pieces attached at both ends
of the mandrel to
provide for attachment in a well string. National pipe taper
(NPT) threads are typically used to depths of 500 feet, whereas higher
strength oil field API threads are used for deeper sets.
The materials used to
manufacture our packers can be varied to suit individual applications.
Standard elements are constructed of natural rubber with high-strength
reinforcing such as Aramid. Optional elastomers include nitrile,
neoprene, or Viton*. The standard metal components of our packers
include a combination of aluminum, stainless steel, and steel for
applications in normal environments. All aluminum or all stainless
steel metal components can be supplied for used in semi-corrosive,
extended-term, or other applications. Titanium, copper, and Hasteloy
are examples of metals available for very specialized
applications.
*DuPont
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INFLATABLE
PACKER SPECIFICATIONS:
Uninflated O.D.
Outside diameter of the packer at rest, which
must always be smaller
than the hole size for which it will be used. Sizes are available from
1 to 16 inches and larger on special order.
Maximum Inflated O.D.
Outside diameter of the packer upon inflation,
which is the largest
suggested hole size for which the packer should be used. Sizes are
available for 1-1/4 to 40 inch and larger hole sizes.
Borehole Differential Pressure
Difference between the test zone pressure below
and the borehole
pressure above the packer, i.e. drawdown or injection pressure.
Packer Inflation Pressure
Sum of the three pressures necessary 1) to match
the water pressure
above the packer (submergence pressure), 2) to stretch the rubber
element out to the borehole, and 3) to seat the packer firmly enough
against the well hole to prevent any movement caused by the borehole
differential pressure.
Uninflated Rubber Element Length
Affects the "holding power" and sealing ability
of the packer. A longer
element has more rubber contact against the hole and provides a larger
frictional force to support a larger borehole differential pressure.
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TYPICAL INFLATABLE PACKER APPLICATIONS
Inflatable
packers
have been used in the oil and gas industry since
the 1940s. Until recently, however, their use was restricted by
prohibitive
costs and limited availability. Now, several disciplines (e.g. ground
water
development, contamination studies, dewatering, geothermal, mining,
coal bed
methane, and geotechnical studies) use a wide selection of reasonably
priced
packers.
The selection of a packer for a particular job application is very
important for success at a reasonable cost. The differential
pressure and hole size are primary considerations. Next,
the
materials of construction should be considered, especially when
adverse chemical and physical conditions could exist.
First, we will discuss the hole diameter size and borehole differential
pressure in a packer application. For example, to pump a 2-inch
diameter by 50-foot deep monitor well that is full of water, the
maximum borehole differential pressure (maximum drawdown) would be 50
feet of water times 0.433 psi/foot of water equals 22 psi. Therefore, a
1-3/4 inch O.D. packer with a 22 psi differential pressure rating would
do the job. In addition, the packer should be constructed of stainless
steel and have an element gland covered with Viton* to reduce sample
contamination. A Baski Purge PackerTM would be
ideal.
Another packer application might be in a mud-filled pilot drill
hole at a potential water well site. If there is nonpotable water
at an unknown depth, packer testing can define where the "poor" water
is located. A straddle packer configuration is attached to
the drill pipe and lowered into the open borehole. Water is then pumped
from a specific zone between the straddle packers by using airlift
pumping methods inside the drill pipe. The testing would normally start
from the bottom of the hole and progress upward. After locating the
poor water, it can be cased off and a potable water well completed.
As an example, let us examine a straddle packer arrangement
for the above application with a 7-7/8 inch I.D. by 1,000-foot
deep hole. For a competent rock hole, a 5-1/2 inch O.D. packer with
a 2-1/2 inch (Sch. 80) mandrel would be an economical choice. However,
if unstable hole conditions are possible, then a better choice would be
a 6-1/2 inch O.D. packer with a 3-inch (Sch. 160) mandrel. API round
threads for a higher joint strength are also recommended in case the
hole collapses. If the hole were completely pumped dry, there would be
a 433 psi differential pressure. Therefore, a packer with a 500 psi
differential pressure rating is recommended. Standard construction
materials (aluminum, stainless steel and steel components, and a
reinforced, natural rubber element) should be sufficient. All stainless
steel construction with Viton* and a longer than standard element
length are available options.
A third packer application could be hydrofracturing a
low-yielding, 6-inch diameter, domestic well with an installed pitless
adapter. A good selection would be the fracture packer (Fracker™)
with a 4.9 inch O.D. to clear the pitless adapter which may protrude
inside the well casing. A 3,000 psi differential pressure rating would
be sufficient for most fracking jobs up to a 3,000 psi injection
pressure. The life of the FrackerTM (i.e., the number of
packer settings with high pressure injection) is a direct function of
the inflatable packer specifications, the hole conditions and the
proper procedures used by the contractor.
Hydrofracturing between two packers can develop an
extremely high force on the connecting pipe between the packers. In a
10-inch hole at 3,000 psi, the tension force is close to a
quarter of a million pounds! Proper selection of pipe and thread
pattern between the packers prevents failure that can result in the
loss of the lower packer and damage to both packer elements from
sliding in the hole. *DuPont
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