Note: Descriptions are shown in the official language in which they were submitted.
CA 02539946 2006-03-16
CROSS REFERENCE TO RELATED APPLICATIONS
This application claims the benefit of priority of ir.S. Provisional Patent
Application
No. 60/665,117 filed March 24, 2005, which is incorporated herein by
reference.
FIELD OF TLEI>E ~NYENTION
The present invention relates generally to a method and apparatus for
transferring
material into a fluid stream. More particularly, the present invention relates
to a method and
apparatus for transferring sieved solids into a high-pressure gas stream for
hydraulically
fracturing a subsurface reservoir or to deliver specialized chemical
treatments before, during,
ar after hydraulic fracturing.
BACKGROUND OF THE INVENTION
In general, during hydrocarbon production from subsurface reservoirs, a fluid
stream
is often injected into wells to alter the effective permeability in the
formation and assist in the
mobilization of the gas or oil towards the wcllbore for subsequent production
to the surface,
for example by hydraulically fracturing the subsurface reservoir.
During hydraulic fr'deturing, a high-pressure fluid is directed into the
reservoir causing
the xesexvoir to fracture. While the fractures are held open by the high-
pressure fluid, it is
desirable to place a proppant in the fractures to hold them open after
hydraulic fracturing.
In coal bed methane (CBlvJ] reservoirs, a gaseous fracturng fluid, preferably
nitrogen
is omen used. However, due to the viscosity and other properties of nitrogen,
it is not
particularly good at carrying or supporting a prappant down the wellbore and
into the
reservoir.
Accordingly, in view of the above-mentioned deficiencies in the art, it is
desirable to
provide an improved method and apparatus for transferring materials into a
fluid stream for
hydraulic fracturing. More specifically, there is a need for transferring
proppanC into a high-
pressure fluid stream for hydraulic fracturing of a subsurface reservoir.
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SUMMARX OF THl~ ~1VVENTI0111
It is an object of the present invention to obviate or mitigate at least one
disadvantage
of the previous systems.
In one aspect, the invention provides an apparatus for transferritxg material
into a fluid
streartt comprising: a reservoir for storing material; a f rst oonduit
connected to a tap portion
of the reservoir for flowing fluids and controlling pressure; a metering
device connected with
the reservoir and controlled by a metering controller for controlling the
pressure of a fluid
stream; and a mixing chamber connected with the metering device for contacting
the material
with the fluid stream.
Preferably, the fluids are liquids, fluid like solids ar nitrogen. Preferably,
the material
comprises sioved sand, resin-coated sand, resin coated ceramic proppant, glass
spheres, plastic
spheres, synthetic particles or a mix thereof Preferably, the reservoir can
subsist in high-
pressure, 10,000 psi. Preferably, the reservoir has a working volume between
about 0.001 m3
and 20 m3. Preferably, the first conduit inaludos a valve for controlling a
volume of fluids and
a valve for controlling atmosphere pressure. Preferably, the second conduit
includes a valve
for conirohing a volume of material. Preferably, the metering device includes
a seat and a dart
for controlling pressure of the fluid scream. Preferably, the seat is
cylindrically shaped and
tapered both top and bottom toward the central portion. Preferably, the dart
is cone shape and
is movable toward and away from the seat. Preferably, the dart includes a
linear actuator
which is connected w a metering controller. Preferably, the mixing chamber
includes an
entering gate for controlling pressure and an exit gate for injecting the
fluid stream.
Preferably, the first conduit includes an adjustable choke between the first
conduit and the
entering gate for creating a pressure differential.
In another aspect, the invention provides a method for transferring fluids
into a gas
stream comprising the steps of adding material in a reservoir; flowing a fluid
stream to the
material in a reservoir; controlling pressure of the material atld a fluid
stream using a metering
device; creating pressure differential using an adjustable choke; and
injecting the fluid stream
by desired iuj action rate and. pressure continuously.
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Preferably, the material comprises sieved sand, resin-coated sand, resin-
coated
ceramic proppant, glass spheres, plastic spheres, synthetic particles or a
rnix thereof
Preferably, the fluid is nitrogen. Preferably, the material is a proppant.
ether aspects and features of the present invention will become apparent to
those
ordinarily skilled in the art upon review of the following description of
specific embodiments
of the invention in conjunction with the accompanying figures.
BRIEF DESGIfHpTION OF THE DRAWINGS
Embodiments of the present invention will now be described, by way of example
only,
with reference to the attached Figures, wherein:
Fig. 1 is a schematic representation of a system of the present invention for
transferring a material into a tlttid stream;
p'ig. 2 is a partial detail view of a metering device of the present
invention; and
Fig. 3 is a partial detail YIEW Of the 111eter111g controller of the present
invention.
DETAILED DESCRIPTION
Generally, the present invention provides a method and apparatus to transfer a
material
into a lugh pressure fluid stream.
Referring generally to f'l~uro 1, there is illustrated a transferring
apparatus 100 to
transfer fluids into a high-pressure fluid stream 7 using gravity andlor
pressure differential.
F~..TJ)ii) STREAM
A fluid stream 7 provides a fluid to the transferring apparatus I00.
Preferably, the
fluid stream 7 is a nitrogen stream. Preferably the fluid stream 7 flows at a
raie between about
1 to about 30 m3/minute {liquid rate equivalent). The fluid sTxeam 7 is
preferably at about
10,000 psi. Preferably the fluid stream 7 is at a temperature in the range of
about 0°C to 60°C.
More preferably, the temperature is about 40°G.
Other suitable Quids for the fluid stream '7 include liquid GQ2, water (as
liquid ar
steam), liquid hydrocarbons, methane, liquid propane, etc., or other fluids
used for hydraulic
fracturing or otherwise injected or forced into a subsurface
reservoir/formation.
RESERVOIR
A transferring apparatus 1DD includes a reservoir 10 such as a cylindrical
pressure
vessel to hold the material 1 ~ to be added. The reservoir 10 is designed for
a volume and
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working pressuxe suitable for the particular operation. Preferably, the
reservoir 10 is suitable
for about 10,000 psi and with a working volume between about 0.001 m3 to 20
m3. A first
conduit 21 is used to provide a positive blanket pressure to the reservoir 10
from the fluid
stream 7. A second conduit 22 transfers fluids from a transport truck or other
supply (not
shown) bo the reservoir 10. The first conduit 21 includes a valve 21a to
control blanket
pressure or isolate the reservoir 10 from the first conduit 21. A vent 21b may
be used to vent
the reservoir 10 to atmosphere and may be located on the first conduit 21 or
directly on the
reservoir 10.
MATERrAL ADDED
The material 15 may be a sieved solid. The sieved solid may be any material
used for
propping open (e.g. a proppant) a fracture created by the fluid, delivering a
chennical to the
fracture system (e.g. encapsulated chemicals, powders, etc,), or scouring or
eroding a fracture
system. Solids may include sieved sand, resin coated sand, resin coated
ceramic proppant,
glass spheres, plastic spheres or synthetic particles. Preferably, the
material 15 is a ceramic
round synthetic polishing type proppant. The material 15 may be an abrasive or
scaling type
prappant, hut may cause increased mechauieal wear when the fluid stream 7
containing the
material 15 is directed into the subsurface reservoir (net shown) through
regular or coiled
tubing (net shown) down a wellbore (not shown}.
The material 15 may also be a specialized chemical for treatment before,
during, or
after hydraulic fracturing.
METERING DEVICE
Referring to figures 1 and 2, a metering device 30 including a seat 31 and a
dart 32 is
mounted between the reservoir 10 and the ruixing chamber ~40. The seat 31 is
preferably
cylindrically shaped tapered both top aad bottom toward a central portion. The
dart 32 is
preferably cone shaped and is movable between a seated position and an open
position by a
linear actuator 32a for controlling flaw of material 15 from the reservoir 10.
The dart 32 has a
linear actuator 32a operable by a metering controller 50. The seat 31 and dart
32 are
replaceable. The taper on the seat 31 and dart 32 may range from 10° to
80° to adjust far solid
or liquid materials or to adjust flow control characteristics. Preferably the
linear actuator 32a
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is a standard hydraulically operated blow out preventor (BOl') known in the
art. Preferably
the linear actuator 32a includes an indicator to show the position of the dart
32.
MIXING CgAM>sER
Referring to figure 3, a mixing chamber 40 provides a connection between the
fluid
stream 7 and the material 15. Upstream of the mixing chamber 40, an adjustable
choke ZIc
may be used to provide a pressure differential between the mixing chamber 40
and the
reservoir 10. The choke 21c preferably is adjustable to create a pressure
differential of
between about 0 to about 1000 psi. A guide bushing 51 directs the linear
actuator 32a, and
sealing means in the form of a packing seal 52 allows the linear achtator 32a
to he movable
while retaining pressure within ilte mixing chamber 40.
Preferably, the pressure of the fluid stream 7 is about from 30 to 70 NlPa,
and more
preferably is from 35 to 55 M>?a. Preferably, volume flaw rate is from about
100 to 5000
SCMfmin. (standard cubic meters per minute) and more preferably is from about
500 to 2000
SCMlmin. Most preferably, the volume rate is 1500 SCMlmin. Preferably, the
velocity of the
fluid stream 7 is about 125 m/sec in at least a portion of the mixing chamber
40. Depending
upon pressures and specific gravity of the material being added, velocity
ranges from about 50
m/sec to over 300 mlsec.
OPEIItATIOhI
In operation, in order to fill the reservoir 10, the dart 32 is seated in the
seat 31 to
isolate reservoir 10 $om the mixing chamber 40. The valve 21a is closed and
the valve 21b
opened to vent the reservoir 10 to atmosphere, and the valve 22a opened to
allow material 15
to transfer through the second conduit 22 from the transport truck or other
source (not shown)
into the reservoir 10. Once the reservoir l 0 is filly with material 15 to a
desired level, the
valve 21b and the valve 22a are closed, arid the valve 21 a opened to allow
pressure from the
fluid stream 7 to pressurize the reservoir 10.
When the fluids such as liquids, fluid like solids ar nitrogen (N2) are
flowing through
the fluid stream 7, the adjustable choke 21c tray be used to ereate a pressure
differential
between th.e mixing chamber 40 and the reservoir 10. This differential
pressure will push
material 15 towards the metering device 3D. The Bow of the material 1S into
the fluid stream
7 may be controlled by moving the dart 32 towards or away frour the seat 31 to
vary the flow
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area available for the material 15 through the metering device 30. pifferent
seat 31 arid dart
32 pairs can be used to further refine the control the flow of materials, e.g.
by using different
taper on the seat 31 or on the dart 32.
The amount of the material 15 in an outlet fluid stream 8 may be monitored by
means
laiown i.u the art, such as a measurement of density using a radioactive or
ultrasonic
densometer (not shown), and adj ustment made by moving the dart 32 in
response.
xn a hydraulic fracturing operation or chemical treatment operation, the
outlet filuid
stream 8 may be directed into the reservoirlformation as is lrnown in the
industry.
MULTI-BATCH
In a normal hydraulic fiaeturing operation a large quantity of fracturing
fluid (e.g.
nitrogen) may be used requiring a corresponding relatively large duantity of
material (e.g.
sieved solids). This relatively large quantity of material can be supplied in
a single reservoir
similar to the reservoir 10, sized to suit the quantity of material. As
outlined above, a batch of
material is loaded into the reservoir 10 and then mixed into the fracturiaag
fluid (e.g. nitrogen)
until it is all gone.
Alternatively, a plurality of reservoirs similar to the reservoir 10 may be
used together
to provide a suitable size (e.g. at least two reservoirs to provide at least
two times the volume,
etc.), or to provide for different materials (e.g, different reservoirs may
contain different
materials}.
In such a mufti-reservoir, or mufti-batch configuration, a plurality of sets
(or trains)
having a reservoir 10, a metering device 30, and a mixing chamber 40 and
additional conduits
(e.g, piping) may be used to allow the isolation or sequencing of trains to
operate the mixing
of material in a semi-continuous batch mode. In operation, at least one train
could be
operating, while at least a second train is isolated from the fluid stream 7
and being filled
from the transport truck or other source (not shown). When the reservoir 10 of
the first train is
empty or near empty, the second train may be brought into operation by opening
and closing
appropriate valuing. Thus, allowing substantially continuous flow of the fluid
stream 7.
The above-described embodiments of the present invention are intended to be
e~camples only_ Alterations, modifications and variations may be effected to
the particular
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embadimcnts by those of skill in the art without departing from the scope of
the invEntian,
which is defined solely by the claims appended hereto.
