Note: Descriptions are shown in the official language in which they were submitted.
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Description Manual
Mixing Device for Oil Well Fracturing Fluid
Technical Scope
This invention is about a mobile device for making oil well fracturing fluid
directly from guar
powder without taking the mid-step of slurry formation.
Technical Background
Hydraulic fracturing technology has been widely adopted in oil industry to
stimulate oil well
productivity through increasing extraction rate of petroleum from oil layer
and extending
oilfield's productive life span. The quality of fracturing fluid plays a vital
role in the
effectiveness of fracturing operation. The fracturing fluid is made of guar
gum (powder)
water solution at a certain concentration mixing with additives such as
demulsifier,
discharge-aiding agent, and viscosity-reducing agent to form an even-spread
liquid with
desired viscosity.
The fracturing technology has a strict requirement on the quality of
fracturing liquid. The
main requirements include: 1 ) The proportions of various components in
fracturing fluid
should be accurate with a maximum tolerance of t2%. 2) All components in
fracturing fluid
should be thoroughly mixed and no guar lumps should exist in the base liquid.
3) The
fracturing fluid is made on fracturing site. 4) The instantaneous viscosity of
the fracturing
fluid made on site must reach over 90% of the maximum level achieved in
laboratory.
5) On-the-site fracturing fluid preparing speed must reach 1.5m3/minute. 6)
When making
the fracturing fluid on-site, the fluid-making process and equipment must be
flexible enough
to quickly meet the different demands from fracturing operation under various
working
conditions.
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The above-mentioned requirements define the difficulties in developing an
efficient and
mobile fracturing-fluid-making device. Conventional fracturing fluid making
process mixes
water and guar powder to form a condensed guar-water mixture (usually called
guar slurry).
as a middle step, from which the guar slurry is diluted to guar solution with
desired
concentration. The conventional approach has following disadvantages: A)
Investment has
to be made on workshops and devices including several water tanks, each over
100m2 in
capacity in the vicinity of the operation sites. B) The viscosity release is
slow. Consequently,
the guar slurry has to be store for up to 4 hours before its viscosity reaches
the desired level.
C) The distance between the fixed workshop and the operating site is typically
50~200km. If
unexpected interruption occurs in the fracturing operation, all the guar
slurry (or fracturing
fluid) transported from 50-200km away to the site has to be discharged, which
results in not
only great economic losses but also environmental pollution.
Contents of this Invention
This invention is about a device that can be easily transported to the
fracturing location to
make the fracturing fluid directly from guar powder. It meets all the strict
requirements on
the fracturing fluid preparation while overcomes the weaknesses in the
conventional
approach.
The invention, a kind of mobile equipment for making oil well fracturing
fluid, is mounted on
a semi-trailer and has the following features:
The device consists of a machine room and a control cabin. All the mixing
equipment units
are installed in the machine room and are controlled through a control console
installed in
the control cabin. The semi-trailer is designed to be towed by a road tractor.
There are
foldable supporting legs on the front and back of semi-trailer.
As illustrated in Figure 1 & Figure 2, the device consists of following
working units:
~ Conveyer (3)
~ Feeding device (4)
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~ Water-powder mixer (5)
~ Release tank (6)
~ Static mixer (7)
~ High-speed stirrer (8)
~ Additive device (9)
~ Liquid delivery device (Not shown on Figure 1 or 2)
The conveyer includes two three-stage conveyer spirals driven by motors. The
conveyer
spiral on top is connected to the feeding device.
The feeding device includes guar gum reserve tank and granular anti-expansion
agent
reserve tank. In each tank, a set of motor-driven feeding spirals are
installed. An outlet is set
at the bottom of guar gum reserve tank, where it leads to a precise feeding
spiral driven by
a frequency-converting motor The outlet of anti-expansion agent reserve tank
is set on the
top of release tank.
The water-powder mixer includes:
~ An inlet pipeline, connected (in radial direction) to the outlet of precise
feeding spiral.
~ A gradually-narrowing suction chamber, connected to the inlet pipeline.
~ A gradually-expending diffusion chamber, connected to the outlet pipeline.
~ A choke, connected between the suction chamber and the diffusion chamber.
~ A jet pipe, on central line of the suction chamber and the diffusion
chamber.
The release tank consists of three cylinders placed one in another whose
diameters
decrease in sequence. The top of each cylinder is open. The inlet of the out-
most cylinder
connects to the outlet pipe of water-powder mixer. An outlet is arranged on
the bottom of
in-most cylinder.
The static mixer includes a mixing chamber formed by zigzag pipelines. The
inlet of the
mixing chamber connects to an outlet at the bottom of release tank. Several
rotating blades
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are installed at intervals inside the mixing chamber. The neighboring blades
are staggered
at 90 degree angles with each other and rotate in opposite directions.
The high-speed stirrer includes frame, motor, transmission, stirring rods, and
stirring
cylinders. The stirring cylinders includes 4~8 layers whose diameters increase
gradually
from the interior to the external. Supports are arranged between the bottoms
of those
cylinders. The bottoms of these cylinders are all connected to a vertical
delivery pipe. The
walls of the odd-numbered cylinders are lower than those of the even-numbered
ones.
Discharge holes are opened on the lower part of the odd-numbered cylinder
walls. The
above-mentioned delivery pipe connects to a feeding pipe. The feeding pipe
connects to the
outlet of static mixing device. A discharge pipe is set on the out-most
cylinder. Several
stirring rods are positioned between the layers of cylinders.
The additive device includes a demulsifier reserve tank, a discharge-aiding
agent reserve
tank, and a viscosity-reducing agent reserve tank. The outlets of these
reserve tanks
connect to the discharge pipe of the high-speed stirrer.
The liquid delivery device includes a liquid delivery pipe connected to the
end of high-speed
stirrer discharge pipe. The liquid delivery pipe goes from the middle of the
trailer to its
bottom. The pipe is divided into two routes and laid along both sides of the
semi-trailer to its
back, where each rout connects to a section of rotating pipe.
This invention, which adopts the above-mentioned design, has following
advantages:
1. It is mobile. The whole device is assembled on a semi-trailer, which is
designed to be
towed by a road tractor to the fracturing operation site and makes the
fracturing fluid
on the spot. As a result, it can not only save the investment on the fixed
workshops
and eliminate the slurry transportation expense accrued in conventional
approached
but also improve the working efficiency and quality.
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2. This device is suit to work in various operating environments and can
protects
operators and machines from harsh climate conditions. A thermal insulating
layer
has been placed around the while trailer-compartment, which is segregated into
a
control cabin and a machine room. As a result, the working temperature can be
maintained at above 5°C even if the outdoor temperature drops to -40oC.
3. The design of conveyer mechanism is compact and easy to work with. By
adopting
two groups of three-stage convey spirals, which shares a same first-stage
convey
spiral that is free to move up and down, the conveyer adapts well to the
limited
structural space inside the compartment and saves the construction cost.
4. The feeding device in this invention uses a set of feeding spirals for each
reserve
tank to work with a precise feeding spiral in providing guar gum for the water-
powder
mixer and to work with another feeding spiral in providing anti-expansion
agent to the
release tank. This design is simple, compact, reliable, and easy for repair
and
maintenance. Furthermore, it prevents the guar gum from caking.
5. The water-powder mixer device in this invention applies the jet principle
by adopting
a gradually-narrowing suction chamber, a choke and a gradually-expending
diffusion
chamber. The high-pressure spray of water or guar powder from the jet pipe
results
in a negative pressure around the jet pipe that sucks the guar powder or water
in
from the material hole, and the fine water spray and guar powder can be evenly
mixed. This design can effectively prevent the guar from caking and rapidly
increase
the viscosity of the guar solution. It is also discovered through experiments
that
reducing the choke length to zero can efFectively prevent the guar powder from
building up on the choke, which consequently clog the chock.
6. The release tank adopts three cylinders whose diameters decrease in
sequence.
The tops of these cylinders are open. When the guar solution flow a round-
about way
through the release tank, the vast amount of air bubble among the liquid will
be
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pressed and broken in the eddy current. This process releases the air from the
liquid so as to facilitate the next stage pumping operation.
7. The unique design of the mixing chamber increases the guar solution's
chances of
colliding on the pipe wall where the pipe bend and extends the time for which
the
guar solution stays in the pipeline so as to better release the solution
viscosity. This
design also improves the blend condition of the solution when the liquid is in
between
the blades, where it is stirred to rotate clockwise at one time and
counterclockwise at
next. In particular, the unique design of the rotating blades effectively
reduces the
viscosity degradation of guar solution.
8. The following designs of the high-speed stirrer gives the liquid a
continuous and
intense stir as well as effectively increases the times and duration of the
liquid being
stirred;
A) Multiple-cylinders structure in which the liquid is stirred in sequence by
several
stirring rods between the layers of the stirring cylinders, which effectively
increases the times and duration of the stirs.
B) An interlayer between the bottom of the out-most cylinder and the frame is
segregated by a partition board into a feeding area and a discharge area,
which
makes the whole structure compact.
As a result, the device is capable of releasing over 90% of the maximum
viscosity
level achieved in laboratory test at a rate of 1.5m3/minute.
9. The dual liquid delivery pipe design in the liquid delivery device enables
a non-stop
delivery of fracturing fluid to reserve tank vehicles, without having to stop
the
machine when switching from loading one reserve tank vehicle to loading
another.
The different working units of this invention are well integrated into each
other to optimize
the usage of the space confined by the compartment. The device is mounted on a
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semi-trailer and its working parts are controlled by a computer in control
cabin. This
invention meets the oil industry's demand for a reliable, mobile, and
efficient fracturing fluid
maker.
List of illustrations
Figure 1: General Structure
Figure 2: Top View of Figure 1
Figure 3: Conveyer
Figure 4: Side View of Figure 3
Figure 5: Feeding Device
Figure 6: Side View of Figure 5
Figure 7: Water-Powder Mixer
Figure 8: Water-Powder Mixer When Choke Length is Zero
Figure 9: Release Tank
Figure 10: Static Mixer
Figure 11: Slotting on the Rotary Blade in Figure 10
Figure 12: Rotary Blades in Figure 10 after Twist
Figure 13: High-speed Stirrer
Figure 14: Liquid Delivery Device
Figure 15: Upward View of Liquid Delivery Pipe in Diagram 14
Detailed Aaalication Scheme
As shown in Figures 1 and 2, the whole device consists of a semi-trailer (2)
towed by a road
tractor. The mixing devices are mounted on a semi-trailer. The upper part of
the trailer is an
externally-packed compartment with a thermal insulating layer placed at
interior. The
compartment on the semi-trailer frame (24) is segregated into control cabin
(21 ) and the
machine room (22). An operation and control console (23) is installed in the
control cabin
(21 ). The mixing device is installed in the machine room (22).
The mixer in this invention includes: conveyer (3), feeding device (4), water-
powder mixer
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(5), release tank (6), static mixer (7), high-speed stirrer (8), additive
device (9), and liquid
delivery device (10).
As shown in Figures 1 ~4, the function of conveyer (3) in this invention is to
lift powder
materials for making water solution from ground level to the feeding device
(4) on the
semi-trailer. Since two reserve tanks are needed for material conveyance, the
conveyer (3)
uses two sets of motor-driven three-stage conveying spirals (31, 32, and 33)
extend to the
tops of both reserve tanks. Meanwhile, since the two kinds of materials can be
delivered
intermittently, the two sets of second-stage and third-stage conveying spirals
can share a
same first-stage spiral (31 ). The first-stage spiral (31 ) is designed to
move up and down and
to rotate. Once the conveyance finished, simply take away the bucket (34) and
raise the
first-stage spiral to clear the space for other operations.
As shown in Figures 2, 5 and 6, the feeding device in this invention includes
two reserve
tanks (41, and 42) for guar, and anti-expansion agents. Each reserve tank (41
or 42) are
equipped with a set of three feeding spirals (45, 46, and 47) driven by motor
via a reducing
gear (44). These feeding spirals are positioned parallel to each other, with
spirals 45 and 46
on top and the other one (47) at the bottom. The inlets of both reserve tanks
(41, and 42)
are set on top, to where the third-stage conveying spirals (33) of the
conveyer (3) convey
the powder materials. The outlet of guar reserve tank (41 ) is set at its
bottom in the middle,
from where the material is delivered through a cylinder to a precise feeding
spiral (49)
driven by a frequency converting motor (48), which also precisely controls the
material
quantity. The outlet of anti-expansion agents reserve tank (42) is set a side,
where the
anti-expansion agent is directly added to release tank (6) from top by another
feeding spiral.
As shown in Figures 1 and 7, the water-powder mixer (5) in this invention has
an inlet pipe
(51 ) with a material hole (52) at one end to receive materials from the
precise feeding spiral
(48). The other end of inlet pipe (51 ) connects, in sequence, to a gradually-
narrowing
suction chamber (53), a choke (54), and a gradually-expanding diffusion
chamber (55). A jet
pipe (56) is positioned on the centerline of suction chamber (53). The jet
pipe (56) connects
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a water pump (57 on Figure 1 ), which connects to water source.
Experiments show that powder tends to build up at the outlet of choke (54)
after the
extended use of jet pipe (56), which will eventually clog the jet pipe nozzle.
To overcome
this drawback, this invention minimizes the length of choke (54) to enlarge
the space of
liquid-water mixing chamber while ensuring sufficient negative pressure.
Experiments show
that the negative pressure produced is still sufficient to suck the guar
powder even when
the choke length reduces to zero (as shown in Figure 8). In this extreme case,
the
water-powder mixing space is the biggest and the powder build up can be
greatly alleviated,
which is an innovative application of the jet principle. The jet pipe (56) can
be use to spurt
either water or guar powder. In the case when the jet pipe is used to spurt
guar powder, the
connections of guar and water supply need be changed so that water will be
supplied from
the material hole (52). Experiments also show that the jet pipe can be
positioned in suction
chamber (53), at choke (54), or at the inlet of expansion chamber (55)
Figure 9 illustrates the release tank. The function of release tank is to
remove the air that
enters guar solution during the jet mixing process. The release tank includes
three cylinders
(61, 62, and 63), one placed in another, whose diameters reduce in sequence.
The top of
each cylinder is open for ventilation. Guar solution from the diffusion
chamber (55 of Figure
7) of water-powder mixer (5) enters the out-most cylinder (61 ) via the inlet
pipe (64). The air
goes up and is released from top while guar solution flows downward though the
inlets at
the bottom of the second cylinder (62). The pump (66 in Figure 1 ) connected
to the outlet
pipe (65) draws the liquid through the third cylinder on top from the second
cylinder and
goes to the outlet pipe (65) at the bottom of third cylinder (63). The inlet
pipe (64) connects
to the out-most cylinder in a position that the pipe is on tangents line of
cylinder's interior
wall. Several protruding bafflers (not shown in the figures) are installed on
the interior wall of
the out-most cylinder (6) so that the guar solution enters the cylinder (61 ),
rotates around it,
collides with the protruding bafflers, and releases the air in it as quick as
possible.
Figure 10 illustrates the static mixer, which includes a mixing chamber (71 )
formed by
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zigzag pipes and several rotary blades (72) in the mixing chamber (71 ). The
inlet of mixing
chamber (71 ) is connected, via the pipe (73), to the outlet pipe (65) of the
release tank (6).
The mixing chamber (71 ) is arranged downward in "S" shape from the top. This
design
increases the pipe length in a given mixing chamber space. The rotary blades
(72) in the
mixing chamber (71 ) are formed by round stainless steel sheets {as shown in
Fig. 11 ) which
are symmetrically slotted (74) in radial direction and the opposite pairs are
twisted for 60
degree in opposite directions (as shown in Figure 12). Alternatively, two
slots can be
opened on the rotary blades (72) and the rotary blades are twisted 60 degree
in opposite
direction. The axle centers of two neighboring rotary blades (72) are arranged
in a
staggered way at 90 degree and the two neighboring blades (72) will force the
liquid to
rotate in opposite directions. Since there is a space in between any pair of
neighboring
blades, when guar solution flows through the blades, the fluid is forced,
under the effect of
rotary blades, to self-rotate or self-stir clockwise followed by a counter
clockwise self-rotate
or self stir. The solution is thoroughly mixed in the gaps between the rotary
blades (72).
Figure 13 illustrates that the high-speed stirrer consists of a frame (81 ),
stirring cylinders
(82), stirring rods (83), a transmission (84), and a motor (85). The stirring
cylinders (82) and
the motor {85) are all mounted on the frame (81 ). The motor (85) is connected
to the stirring
rods (83) via transmission (84), which uses four C-type V-belts to transmit
the power. The
stirring cylinders (82) include six layers {821, 822, 823, 824, 825, and 826).
Each layer is
supported by three to six supporting columns at the bottom. A stainless steel
pipe (87),
served as a delivery pipe, goes through the bottom of each cylinder (821, 822,
823, 824,
and 825). Ail the layers are fixed to the delivery pipe (87) with nuts and are
integrated as a
whole. The walls of odd numbered cylinders (821, 823, and 825) are higher than
those of
the even numbered ones (822, 824, and 826). Discharge holes are opened on the
lower
part of even numbered cylinder walls (822, 824, and 826). The inlet of
delivery pipe (87)
connects to the outlet of the static mixer via a feeding pipe (88). The
discharge hole (829)
of the out-most cylinder (826) connects to a discharge pipe (89). There are
several stirring
rods (83) arranged between the layers of cylinders. On the bottom of its
frame, there are
foundation bolts (not shown in the figures) so that the frame can be installed
on the floor of
io
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semi-trailer. An interlayer is added to the space between the frame and the
bottom of the
out-most cylinder, The interlayer is segregated in to two parts by a partition
board (812): the
space on one side of the partition board is used as a feeding pipe (88) that
connects to
delivery pipe (87) while the space on the other side of the partition board
(812) connects to
discharge hole of the out-most cylinder and serves as discharge pipe (87).
This
arrangement makes the whole structure compact, integrated, and convenient for
transportation and storage. The number of cylinders layers may change depends
on needs.
Similarly, the transmission (84) can use V belts or other scheme(s).
When the high-speed stirrer is operating, the guar solution flows through the
feeding pipe
(88) and delivery pipe (87) into the first layer cylinder (821 ). Liquid is
keeps on being stirred
and sheared by the stirring rod (83) while it rises in the first layer
cylinder, overflows from
top into the second layer (822), where it is stirred and sheared by the
stirring rods inside the
second layer. The stirring rods in third layer will do the same thing when the
liquid flows into
third layer cylinder (823) from the discharge hole (827) on the lower part of
the second layer
cylinder (822). The same repeats in the rest of the layers as guar solution
flows through
them. After six times of high-speed stirring and shearing, the liquid flows
into the discharge
pipe (89) from the discharge hole (829) at the bottom of the out-most layer of
cylinder and
flows out from the discharge pipe (89).
Figure 2 shows that the additive device (9) includes a demulsifier reserve
tank (91 ), a
discharge-aiding agent reserve tank (92), and a viscosity-reducing agent
reserve tank (93).
The outlets of these reserve tanks (91, 92, and 93) all connect to the
discharge pipe (89 of
Figure 13) of the high-speed stirrer (8 of Figure 2), where they mix with the
guar solution
and form qualified fracturing fluid.
As illustrated in Figure 14, the liquid delivery device (10) starts at a
liquid delivery pipe (11 )
to receive prepared fracturing fluid. The liquid delivery pipe goes from mid
semi-trailer to its
bottom and is fixed to the frame by suspension clips. At that point, the
delivery pipe is
divided into two routes (12). These two routes go from both sides of semi-
trailer to the back
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of vehicle, extend to a certain height (13) (as shown in Figures 14 and 15),
and each
connects to a rotating pipe (14) to facilitate delivering liquid to the
reserve tank. Each of the
two liquid delivery pipes installs an electric-magnetic valve controlled from
control cabin, so
that each delivery line can independently deliver the liquid.
This device uses computer to realize centralized working process control. In
the control
cabin (24), after the operator inputs various parameters such as discharge
rate and
ingredients from control cabin, the computer will start the device, control
the action of the
valves, adjust the frequency-altering motor, and control material feeding
speed. Meanwhile,
the operators can monitor the current system status through the readings on
gauges and
material level meters.
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