U.S. patent application number 14/490385 was filed with the patent office on 2016-03-24 for low pressure direct proppant injection.
The applicant listed for this patent is SCHLUMBERGER TECHNOLOGY CORPORATION. Invention is credited to Laurent Yves Claude Coquilleau, Rajesh Luharuka, Christopher Shen.
Application Number | 20160084044 14/490385 |
Document ID | / |
Family ID | 55525291 |
Filed Date | 2016-03-24 |
United States Patent
Application |
20160084044 |
Kind Code |
A1 |
Shen; Christopher ; et
al. |
March 24, 2016 |
LOW PRESSURE DIRECT PROPPANT INJECTION
Abstract
A multi-tank system for preparing fluids for hydraulic
fracturing of reservoirs and methods of injecting the prepared
fluid upstream from pumping units are disclosed. The multi-tank
system allows for a proppant slurry to be continuously formed and
mixed with a proppant carrier in staggered phases to form a
fracturing fluid. This fracturing fluid can then be injected into
the reservoir at normal injection pressures, thus reducing wear and
downtime on the blender, and allowing continuous flow of
proppant.
Inventors: |
Shen; Christopher; (Houston,
TX) ; Luharuka; Rajesh; (Katy, TX) ;
Coquilleau; Laurent Yves Claude; (Houston, TX) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
SCHLUMBERGER TECHNOLOGY CORPORATION |
Sugar Land |
TX |
US |
|
|
Family ID: |
55525291 |
Appl. No.: |
14/490385 |
Filed: |
September 18, 2014 |
Current U.S.
Class: |
166/280.1 ;
166/90.1 |
Current CPC
Class: |
E21B 43/267
20130101 |
International
Class: |
E21B 43/00 20060101
E21B043/00; E21B 43/267 20060101 E21B043/267; E21B 27/00 20060101
E21B027/00 |
Claims
1. An apparatus for preparing a proppant fluid for injection into a
reservoir, comprising: a) a first vessel, a second vessel and a
third vessel, wherein each vessel has a hopper containing
particulates above the vessel, such that the particulates can
gravity feed into the vessel; b) a clean fluid line in fluid
communication with each vessel, the clean fluid line transporting a
clean fluid from a source to each vessel; c) a concentrated
proppant carrier fluid line in fluid communication with each
vessel, the concentrated proppant carrier fluid line transporting a
concentrated proppant carrier fluid; d) a recycle fluid line in
communication with each vessel, the recycle fluid line transporting
a clean fluid from the vessel to form a make-up flow for the clean
fluid line; and e) a displaced proppant slurry line in fluid
communication with each vessel, wherein the proppant slurry line
feeds into the concentrated proppant carrier fluid line to form a
proppant fluid for introduction into a hydrocarbon-containing
reservoir.
2. The method of claim 1, further comprising a dilution line having
a dilution pump that connects the clean fluid line and the
concentrated proppant carrier fluid line such that the clean fluid
can dilute the concentrated proppant carrier fluid before the
proppant carrier fluid combines with the proppant slurry line.
3. The apparatus of claim 1, further comprising a makeup fluid line
connecting the recycle fluid line to the displaced proppant slurry
line.
4. The apparatus of claim 1, wherein the particulates are sand.
5. The apparatus of claim 1, wherein the clean fluid is treated
water.
6. The apparatus of claim 1, wherein the number of the vessels is a
multiple of three.
7. A method of preparing a proppant fluid for injection into a
reservoir using the apparatus in claim 1, comprising: a) filling
the first vessel with a clean fluid; b) partially displacing the
clean fluid from the first vessel, wherein the displaced clean
fluid serves as a make-up flow for the clean fluid into a
subsequent vessel; c) adding particulates into the first vessel to
refill the first vessel without creating fluid overflow; d) mixing
the particulates and clean fluid in the first vessel to form a
proppant slurry; e) displacing the proppant slurry and flushing the
first vessel with a fluid mixture, wherein the fluid mixture
comprises clean fluid and displaced clean fluid from another
vessel, combining the displaced proppant slurry with the
concentrated proppant carrier fluid to form the proppant fluid for
injection into a reservoir; g) repeating steps a)-f) in the second
vessel and the third vessel sequentially; and h) introducing the
proppant fluid into a low pressure side of a direct proppant
injection system.
8. The method of claim 7, further comprising using the clean fluid
to dilute the concentrated proppant carrier fluid before
combination with the displaced proppant slurry.
9. The method of claim 7, further comprising using the displaced
clean fluid to dilute the displaced proppant slurry.
10. The method of claim 7, wherein the particulates are sand.
11. The method of claim 7, wherein the clean fluid is treated
water.
12. A method of fracturing a reservoir, comprising: a) injecting a
first fluid into a reservoir at an injection pressure high enough
to fracture the reservoir forming fractures; b) continuously
combining a proppant slurry with a proppant carrier to make a
proppant fluid, wherein the proppant slurry is continuously made in
at least three tanks in staggered phases such that one tank is
being washed with water partially obtained from a previously washed
tank, a second tank is partially full of wash water and is
receiving proppant, and a third tank is dispensing proppant slurry;
and c) injecting the proppant fluid into to the reservoir to prop
open the fractures.
13. The method of claim 12, further comprising adding one or more
additives to the proppant slurry or the proppant carrier or the
proppant fluid.
14. The method of claim 13, wherein the proppant carrier is in the
form of a gel, emulsion, foam, micelle, or viscoelastic surfactant.
Description
FIELD OF THE DISCLOSURE
[0001] The disclosure generally relates to methods, materials, and
systems for hydraulic fracturing of reservoirs to increase
production therefrom.
BACKGROUND OF THE DISCLOSURE
[0002] Hydraulic fracturing is the fracturing of rock by a
pressurized liquid. Some hydraulic fractures form
naturally--certain veins or dikes are examples. Induced hydraulic
fracturing (also hydrofracturing or fracking) is a mining technique
in which a high-pressure liquid fluid is injected into a wellbore
under pressure in order to create small fractures (usually less
than 1.0 mm wide) in the deep-rock formations in order to allow
natural gas, petroleum, and brine to migrate to the well.
[0003] Most induced hydraulic fracturing occurs in the oil and gas
industry. The first experimental use of hydraulic fracturing was in
1947, and the first commercially successful applications of
hydraulic fracturing were in 1949. Worldwide, as of 2012, 2.5
million hydraulic fracturing jobs have been performed on oil and
gas wells--more than one million of which were performed in the
US.
[0004] In order to keep the fractures open even after the pressure
is reduced and fluid travels back out of the fractures, small
grains of material call "proppants" are co-injected into the well.
The proppants (typically sand or aluminum oxide) hold open the
small fractures once the deep rock achieves geologic equilibrium.
Hereinafter, this type of treatment is referred as conventional
fracturing treatment and the type of proppant placed therein is
referred as homogeneous proppant pack.
[0005] FIG. 1 displays a schematic of a typical hydraulic
fracturing process. A pressurized mixture is injected into a well
and the pressure inside the well causes the reservoir rock to
crack. The mixture can also flow from the well into the cracks to
propagate the fractures. Recovered fracturing fluid and released
hydrocarbons can then be produced, separated and processed.
[0006] The ideal fracturing fluid should: [0007] Be able to
transport the propping agent in the fracture [0008] Be compatible
with the formation rock and fluid [0009] Generate enough pressure
drop along the fracture to create a wide fracture [0010] Minimize
friction pressure losses during injection [0011] Be formulated
using chemical additives that are approved by the local
environmental regulations [0012] Exhibit controlled-break to a
low-viscosity fluid for cleanup after the treatment [0013] Be
cost-effective
[0014] Water-based fracturing fluids have become the predominant
type of coalbed methane fracturing fluid. However, fracturing
fluids can also be based on oil, methanol, or a combination of
water and methanol. Methanol is used in lieu of, or in conjunction
with, water to minimize fracturing fluid leakoff and enhance fluid
recovery. Polymer-based fracturing fluids made with methanol
usually improve fracturing results, but require 50 to 100 times the
amount of breaker (e.g., acids used to degrade the fracturing fluid
viscosity, which helps to enhance post-fracturing fluid
recovery).
[0015] In some cases, nitrogen or carbon dioxide gas is combined
with the fracturing fluids to form foam as the base fluid. Foams
require substantially lower volumes to transport an equivalent
amount of proppant. Diesel fuel is another component of some
fracturing fluids although it is not used as an additive in all
hydraulic fracturing operations.
[0016] A variety of other fluid additives (in addition to the
proppants) may be included in the fracturing fluid mixture to
perform essential tasks such as formation clean up, foam
stabilization, leakoff inhibition, or surface tension reduction.
These additives include biocides, fluid-loss agents, enzyme
breakers, acid breakers, oxidizing breakers, friction reducers, and
surfactants such as emulsifiers and non-emulsifiers. Several
products may exist in each of these categories. On any one
fracturing job, different fluids may be used in combination or
alone at different stages in the fracturing process. Experienced
service company engineers will devise the most effective fracturing
scheme, based on formation characteristics, using the fracturing
fluid combination they deem most effective.
[0017] The viscosity of the fracturing fluid is an important point
of differentiation in both the execution and in the expected
fracture geometry. "Slickwater" treatments, use low-viscosity
fluids pumped at high rates to generate narrow, complex fractures
with low-concentrations of propping agent (0.2-5 lbm proppant added
(PPA) per gallon). In order to minimize risk of premature
screenout, pumping rates must be sufficiently high to transport
proppant over long distances (often along horizontal wellbores)
before entering the fracture. By comparison, for conventional wide
biwing fractures the carrier fluid must be sufficiently viscous
(normally 50 to 1000 cp at nominal shear rates from 40-100
sec.sup.-1) to transport higher proppant concentrations (1-10 PPA
per gallon). These treatments are often pumped at lower pump rates
and may create wider fractures (normally 0.2 to 1.0 inch).
[0018] The density of the carrier-fluid is also important. The
fluid density affects the surface injection pressure and the
ability of the fluid to flow back after the treatment. Water-based
fluids generally have densities near 8.4 ppg. Oil-base fluid
densities will be 70 to 80% of the densities of water-based fluids.
Foam-fluid densities can be substantially less than those of
water-based fluids. In low-pressure reservoirs, low-density fluids,
like foam, can be used to assist in the fluid cleanup. Conversely,
in certain deep reservoirs (including offshore frac-pack
applications), there is a need for higher density fracturing fluids
whose densities can span up to >12 ppg.
[0019] Heterogeneous proppant placement (HPP) is a new approach in
hydraulic fracturing, invented by Kevin England of Schlumberger
Technology Corporation (U.S. Pat. No. 6,776,235). The well
productivity is increased by sequentially injecting into the
wellbore alternate stages of fracturing fluids having a contrast in
their ability to transport propping agents to improve proppant
placement, or having a contrast in the amount of transported
propping agents. The propped fractures obtained following this
process have a pattern characterized by a series of bundles of
proppant spread along the fracture. In another words, the bundles
form "pillars" that keep the fracture opens along its length and
provide channels for the formation fluids to circulate.
[0020] The large volume of proppant that is currently being used in
hydraulic fracturing operations has led to excessive wear and
damage to service equipment. Erosion damage of all wetted parts is
an issue, but is particularly high in the pump and blender units.
Efforts to repair or replace such equipment contributes to downtime
and increases costs.
[0021] A previous concept to mitigate the erosion damage to the
pumps and blenders was described in US20100243255, also by
Schlumberger Technology Corporation. This application describes a
hydraulic fracturing method wherein a concentrated sand slurry is
injected directly into the fracturing base fluid at high pressure,
but downstream from the pumping units. Although this method has not
been commercially implemented to date, initial evidence suggests it
has potential for bypassing much of the wear on the pumping and
blending units. However, the method does not eliminate erosion and
further improvements could be made to optimize the implementation
of this concept.
[0022] What is needed in the art are yet further improvement to
methods, materials and systems for use in hydraulic fracturing,
particularly if such improvements could reduce erosion and damage
to oilfield equipment.
SUMMARY OF THE DISCLOSURE
[0023] The proposed system utilizes the basic concept described in
US20100243255, but with one or more modifications to further
optimize the method. Instead of using direct proppant injection at
the high-pressure area downstream from the pump units, it is
proposed to instead utilize a direct proppant injection system on
the low pressure side of the process. This would replace the
existing blender unit with a system of comparable functionality,
but significantly lower wear due to the decreased pressure. Since
the proppant is being introduced into the fluid upstream from the
high-pressure pumps, there would be no change in the wear on the
pumping units compared to current operations, but wear on the
blender is greatly reduced, plus a continuous stream of proppant is
now possible.
[0024] The proposed system utilizes multiple displacement tanks in
order to avoid disruption of proppant flow during operations. This
would allow at least one tank to be discharging at any given time,
while other tanks are being refilled with proppant and/or fluid. A
conceptual diagram for a system with three displacement tanks can
be seen in FIG. 3.
[0025] The diagram in FIG. 3 also implements various features for
proppant carrier fluid dilution and separating the clean fluid used
for the proppant displacement from the proppant carrier fluid.
Maintaining separation of the clean fluid and the proppant carrier
fluid is important because the proppant has a very slow settling
rate in viscous fluids, and therefore the filling and wetting of
proppant within the displacement tanks would most likely take too
long if the thick proppant carrier and clean fluid were
combined.
[0026] It is proposed to utilize non-gelled clean fluids for the
proppant displacement tanks in order to provide the fastest cycle
times and reduce the volume of tank space required for the system.
The non-gelled clean fluid can also be used to dilute the proppant
carrier fluid before it is mixed with the proppant.
[0027] Another innovative part of the concept is that the clean
fluid required to displace the proppant from the tank full of
proppant slurry (Tank #2) is partially taken from the tank that was
displaced with clean fluid in the previous process step (Tank #1).
Therefore, tank #1 will be partially drained, and the remaining
space can then be refilled with proppant without having any excess
fluid overflow. The portion of the clean fluid filling Tank #2 can
then be used to displace the proppant slurry in a third tank (Tank
#3). This system design feature can be seen in the process steps
(Table 3) and diagram of FIG. 3.
[0028] A method of using the above system to generate a fracturing
fluid slurry utilizes a three-stage operation, which is illustrated
in Table 3 for a three tank system. Each tank undergoes all the
stages sequentially, but staggered in time. Thus, tank 1 undergoes
stage 1 when tank 2 undergoes stage 2, tank three undergoes stage 3
and so on. Such a process design prevents disruption in the
proppant slurry flow because at least one tank is always
discharging the slurry to the gel to prepare the final fracturing
fluid for downhole use. Thus, the system allows continuous
production of proppant for use downhole.
[0029] While the above system and method are exemplified using a
three-tank system, minor changes can be made to accommodate more
tanks. Furthermore, while multiples of three tanks are advantageous
to the three-stage method design, it is not required. A 4, 5, 7 or
8 tank system can easily implement the system.
[0030] One could possibly use only 1 or 2 tanks, but it would not
allow for continuous operation, and there would be operational
drawbacks to such design.
[0031] The invention includes one or more of the following
embodiments, in any combination:
[0032] Fracturing injection system having multiple displacement
tanks for sequential proppant mixing with a clean fluid such that
the resulting proppant slurry is continuous produced and means of
combining the proppant slurry with concentrated gel. Optional lines
for proppant carrier fluid dilution using the clean fluid is also
possible.
[0033] The disclosure provides the following one or more
embodiments, in any combinations thereof.
[0034] Methods of producing a continuous flow of proppant slurry
using a multi-stage washing, blending, and dispensing system.
[0035] Methods of producing a fracturing fluid for injection using
a continuous flow of proppant slurry and a concentrated proppant
carrier fluid.
[0036] Methods of injecting a fracturing fluid into a low-pressure
area of a direct proppant injector system upstream from the pumping
units.
[0037] An apparatus for preparing a proppant fluid for injection
into a reservoir comprising:
[0038] a) a first vessel, a second vessel and a third vessel,
wherein each vessel has a hopper containing particulates above the
vessel, such that the particulates can gravity feed into the
vessel;
[0039] b) a clean fluid line in fluid communication with each
vessel, the clean fluid line transporting a clean fluid from a
source to each vessel;
[0040] c) a concentrated proppant carrier fluid line in fluid
communication with each vessel, the concentrated proppant carrier
fluid line transporting a concentrated proppant carrier fluid;
[0041] d) a recycle fluid line in communication with each vessel,
the recycle fluid line transporting a clean fluid from the vessel
to form a make-up flow for the clean fluid line;
[0042] e) a displaced proppant slurry line in fluid communication
with each vessel, wherein the proppant slurry line feeds into the
concentrated proppant carrier fluid line to form a proppant fluid
for introduction into a hydrocarbon-containing reservoir;
[0043] wherein an optional dilution line having a dilution pump
connects the clean fluid line and the concentrated proppant carrier
fluid line such that the clean fluid can dilute the concentrated
proppant carrier fluid before the proppant carrier fluid combines
with the proppant slurry line.
[0044] A method of preparing a proppant fluid for injection into a
reservoir using the apparatus as herein described comprising:
[0045] a) filling the first vessel with a clean fluid;
[0046] b) partially displacing the clean fluid from the first
vessel, wherein the displaced clean fluid serves as a make-up flow
for the clean water fluid into a subsequent vessel;
[0047] c) adding particulates into the first vessel to refill the
first vessel without creating fluid overflow;
[0048] d) mixing the particulates and clean fluid in the first
vessel to form a proppant slurry;
[0049] e) displacing the proppant slurry and flushing the first
vessel with a fluid mixture, wherein the fluid mixture comprises
clean fluid and displaced clean fluid from another vessel,
[0050] f) combining the displaced proppant slurry with the
concentrated proppant carrier fluid to form the proppant fluid for
injection into a reservoir;
[0051] g) repeating steps a)-f) n the second vessel and the third
vessel sequentially; and
[0052] h) introducing the proppant fluid into a low pressure side
of a direct proppant injection system.
[0053] A method of fracturing a reservoir, the method
comprising:
[0054] a) injecting a first fluid into a reservoir at an injection
pressure high enough to fracture the reservoir forming
fractures;
[0055] b) continuously combining a proppant slurry with a proppant
carrier to make a proppant fluid, wherein the proppant slurry is
continuously made in at least three tanks in staggered phases such
that one tank is being washed with water partially obtained from a
previously washed tank, a second tank is partially full of wash
water and is receiving proppant, and a third tank is dispensing
proppant slurry; and
[0056] c) injecting the proppant fluid into to the reservoir to
prop open the fractures.
[0057] An apparatus or method as herein described, further
comprising a makeup fluid line connecting the recycle fluid line to
the displaced proppant slurry line.
[0058] An apparatus or method as herein described, wherein the
particulates are sand.
[0059] An apparatus or method as herein described, wherein the
clean fluid is treated water.
[0060] An apparatus or method as herein described, wherein the
number of the vessels is a multiple of three.
[0061] An apparatus or method as herein described, further
comprising using the clean fluid to dilute the concentrated
proppant carrier fluid before combination with the displaced
proppant slurry.
[0062] An apparatus or method as herein described, further
comprising using the displaced clean fluid to dilute the displaced
proppant slurry.
[0063] An apparatus or method as herein described, further
comprising adding one or more additives to the proppant slurry or
the proppant carrier or the proppant fluid.
[0064] An apparatus or method as herein described, wherein the
proppant carrier is in the form of a gel, emulsion, foam, micelle,
or viscoelastic surfactant.
[0065] The terms "proppant" and "particulate" are used
interchangeably to refer to a granular solid suitable for use in
subterranean operations. Suitable solids include, but are not
limited to, sand; bauxite; ceramic materials; glass materials;
polymer materials; Teflon.RTM. materials; nut shell pieces; seed
shell pieces; cured resinous particulates comprising nut shell
pieces; cured resinous particulates comprising seed shell pieces;
fruit pit pieces; cured resinous particulates comprising fruit pit
pieces; wood; composite particulates and combinations thereof.
[0066] Composite particulates may also be suitable, suitable
composite materials may comprise a binder and a filler material
wherein suitable filler materials include silica, alumina, fumed
carbon, carbon black, graphite, mica, titanium dioxide,
meta-silicate, calcium silicate, kaolin, talc, zirconia, boron, fly
ash, hollow glass microspheres, solid glass, and combinations
thereof. The proppant pack can be either homogeneous or
heterogeneous, as desired.
[0067] By "proppant slurry" what is meant is a fluid mixture having
granular solid with a liquid, e.g., proppant plus water.
[0068] By "proppant fluid," or what is meant herein is the proppant
carrier (aka base fluid) plus proppant slurry (plus optional
additional liquids and/or additives) that is used to prop open
downhole fractures.
[0069] By "proppant carrier" or "base fluid," what is meant is any
thick and/or dense fluid that can carry the proppant under the
conditions of use. Typical proppant carriers include gels, foams,
viscoelastic surfactants, emulsions, micelles, and the like, that
carry the proppant into the fractures. We have exemplified a
gel-based carrier fluid herein, but other base fluids could be
used. See Table 1 for typical base fluids and their uses.
TABLE-US-00001 TABLE 1 FRACTURING FLUIDS AND CONDITIONS FOR THEIR
USE Base Fluid Fluid Type Main Composition Used For Water Linear
Guar, HPG, HEC, Short fractures, low temperature CMHPG Crosslinked
Crosslinked + Guar, Long fractures, high temperature HPG, CMHPG or
CMHEC Micellar Electrolite + Surfactant Moderate length fractures,
moderate temperature Foam Water based Foamer + N.sub.2 or CO.sub.2
Low-pressure formations Acid based Foamer + N.sub.2 Low pressure,
carbonate formations Alcohol based Methanol + Foamer + N.sub.2
Low-pressure, water-sensitive formations Oil Linear Gelling agent
Short fractures, water sensitive formations Crosslinked Gelling
agent + Long fractures, water-sensitive Crosslinker formations
Water emulsion Water + Oil + Emulsifier Moderate length fractures,
good fluid loss control Acid Linear Guar or HPG Short fractures,
carbonate formations Crosslinked Crosslinker + Guar or Longer,
wider fractures, carbonate HPG formations Oil emulsion Acid + Oil +
Emulsifier Moderate length fractures, carbonate formations
[0070] Further, for simplicity of description, only a simple
proppant fluid comprising a base fluid (e.g., gel), water and
proppant is described, but of course any of the usual additives can
be included therein, such as anti-corrosive agents, anti-scaling
agents, friction reducers, acids, salts, anti-bacterial agents,
wetting agents, buffers, and the like. Typical additives are shown
in Table 2. These can be added to the fluid mixed with proppant,
added to the fracture slurry, added to the base fluid, or added at
any other convenient point during mixing, injection or downhole, as
appropriate.
TABLE-US-00002 TABLE 2 SUMMARY OF CHEMICAL ADDITIVES Type of
Additive Function Performed Typical Products Biocide Kills bacteria
Glutaraldehyde carbonate Breaker Reduces fluid viscosity Acid,
oxidizer, enzyme breaker Buffer Controls the pH Sodium bicarbonate,
fumaric acid Clay stabilizer Prevents clay swelling KCl, NHCl, KCl
substitutes Diverting agent Diverts flow of fluid Ball sealers,
rock salt, flake boric acid Fluid loss additive Improves fluid
efficiently Diesel, particulates, fine sand Friction reducer
Reduces the friction Anionic copolymer Iron Controller Keeps iron
in solution Acetic and citric acid Surfactant Lowers surface
tension Fluorocarbon, Nonionic Gel stabilizer Reduces thermal
degradation MEOH, sodium thiosulphate
[0071] By "clean fluid" what is meant is a fluid that does not
contain proppant. Typically, the clean fluid is water, preferable
one that has been treated to remove excess contaminants and
hydrocarbon products (if produced water).
[0072] The use of the word "a" or "an" when used in conjunction
with the term "comprising" in the claims or the specification means
one or more than one, unless the context dictates otherwise.
[0073] The term "about" means the stated value plus or minus the
margin of error of measurement or plus or minus 10% if no method of
measurement is indicated.
[0074] The use of the term "or" in the claims is used to mean
"and/or" unless explicitly indicated to refer to alternatives only
or if the alternatives are mutually exclusive.
[0075] The terms "comprise", "have", "include" and "contain" (and
their variants) are open-ended linking verbs and allow the addition
of other elements when used in a claim.
[0076] The phrase "consisting of" is closed, and excludes all
additional elements.
[0077] The phrase "consisting essentially of" excludes additional
material elements, but allows the inclusions of non-material
elements that do not substantially change the nature of the
invention, such as instructions for use, buffers, and the like.
[0078] The following abbreviations are used herein:
TABLE-US-00003 ABBREVIATION TERM PPA proppant added HPG
(hydroxypropyl) guar HEC hydroxyethyl cellulose CMHEC carboxymethyl
hydroxyethyl cellulose CMHPG carboxymethyl hydroxypropyl guar lbm
Pound (mass) cp centipoise ppg pounds per gallon
BRIEF DESCRIPTION OF THE DRAWINGS
[0079] FIG. 1: General illustration of induced hydraulic fracturing
in a shale oil field.
[0080] FIG. 2: Oilfield material delivery mechanism used to
introduce an oilfield material into a high-pressure fluid flow to a
well bore. From US20100243255.
[0081] FIG. 3: Low-pressure direct proppant injection concept
diagram according to one embodiment.
[0082] FIG. 4: Schematic of a three-stage method to continuously
produce proppant slurry wherein the lines are simplified, so that
only those lines in use are shown.
DETAILED DESCRIPTION
[0083] In the following detailed description, reference is made to
the accompanying drawings that show, by way of illustration,
specific embodiments in which the invention may be practiced. These
embodiments are described in sufficient detail to enable those
skilled in the art to practice the invention. It is to be
understood that the various embodiments of the invention, although
different, are not necessarily mutually exclusive. For example, a
particular feature, structure, or characteristic described herein
in connection with one embodiment may be implemented within other
embodiments without departing from the spirit and scope of the
invention. In addition, it is to be understood that the location or
arrangement of individual elements within each disclosed embodiment
may be modified without departing from the spirit and scope of the
invention. The following detailed description is, therefore, not to
be taken in a limiting sense, and the scope of the present
invention is defined only by the appended claims, appropriately
interpreted, along with the full range of equivalents to which the
claims are entitled. In the drawings, like numerals refer to the
same or similar functionality throughout the several views.
[0084] It should also be noted that in the development of any such
actual embodiment, numerous decisions specific to circumstance must
be made to achieve the developer's specific goals, such as
compliance with system-related or business-related constraints,
which may vary from one implementation to another. Moreover, it
will be appreciated that such a development effort might be complex
and time-consuming but would nevertheless be a routine undertaking
for those of ordinary skill in the art having the benefit of this
disclosure.
[0085] This work improves the methodology and systems described in
US20100243255, expressly incorporated by reference. US20100243255
described an apparatus and method for injecting a particulate
(proppant) slurry into a high-pressure line downstream from the
high-pressure pumping units for reservoir fracturing purposes. The
method utilized a two-stage process, wherein the particulate solids
are introduced into a pressure vessel isolated from the
high-pressure line in the first stage, and providing a
high-pressure flow into the isolated vessel in the second stage.
The end result is a heterogeneous flow of slurry into the
high-pressure line. The operating stages can be varied to create
intermittent flow of slurry or continuous flow. However, wear on
the proppant blender is exacerbated by the high-pressure injection
conditions.
[0086] The presently disclosed methods and apparatuses improve upon
US20100243255.
[0087] In particular, the proppant fluid is introduced upstream
from the pumping units under low-pressure conditions. By changing
the pressure conditions, a new blender system can be used,
resulting in less wear. However, the wear on the pumping unit is
still present.
[0088] FIG. 2, adapted from US20100243255, is a schematic
illustration of one approach for dealing with overflow of fluid
resulting from the introduction of proppant into the pressure
vessel 203. This figure shows a cross-section of an embodiment of
the oilfield material delivery subassembly during a recharging
operation. In the embodiment of FIG. 2 the subassembly 285 contains
a perforated pipe 251 connecting the pressure vessel 203 to the
reservoir 201.
[0089] As discussed herein above, the pressure vessel 203 goes
through two major operational stages, referred to herein is as
Stage 1: refill and Stage 2: release. In Stage 1: a low-pressure
recharging phase in which oilfield material 275 is introduced into
the pressure vessel 203 via gravity from the supply reservoir 201,
via actuator 216 which opens (lowers) valve 217, wherein metering
gate valve 207 controls the amounts delivered via valve 217.
[0090] In Stage 2: after the pressure vessel 203 has been charged
with oilfield material 275, the pressure vessel 203 is, by
operation of the valves on inlets and outlets thereto, transitioned
into a high-pressure phase in which the contents of the pressure
vessel 203 is released into the pressure vessel discharge line 229
that in turn connects to the fluid line 270 through the exit port
213 that is controlled by a check valve 215.
[0091] FIG. 2 illustrates the recharging phase. During the
recharging phase, the oilfield material 275 enters the pressure
vessel 203 from the supply reservoir 201 and flows to the lower
portion of the pressure vessel 203 by operation of gravity and
mixes with fluid 253, which is supplied from a high-pressure line
211 and controlled by a high-pressure valve 210, to form a slurry
277. This oilfield material 275 displaces some of the fluid present
in the pressure vessel 203. The overflow caused by the displaced
fluid exits the pressure vessel 203 through the overflow outlet 221
that is optionally controlled by valve 219. In this embodiment of
subassembly 285, the overflow fluid also exits the pressure vessel
203 through the oilfield material inlet aperture 205 into the
perforated pipe 251. The overflow fluid may then exit the pipe
through the perforations.
[0092] Because the presently disclosed method introduces a slurry
mixture under low-pressure conditions upstream from the pumping
units, the blender subassembly unit described above can be replaced
with a system with comparable functionality but lower wear.
Furthermore, multiple tanks can be utilized to avoid disruptions of
proppant flow.
[0093] FIG. 3 shows one embodiment of the system 300 described
herein, wherein proppant hoppers 301, 302 and 303 are arranged over
tanks 311, 312, and 313 respectively. Clean water line 320 and
displacement pump 335 brings clean water to each of tanks 311, 312,
and 313 via branches 321, 322, and 323. The clean water line 320
also has an optional branch (past valve 324) through dilution pump
330, thus adding diluent to high concentration proppant carrier
fluid line 340 if needed.
[0094] Clean water mixes in tanks 311, 312, and 313 with proppant
from hoppers 301, 302 and 303, and proppant slurry exits through a
slurry line 344 via branches 341, 342 and 343 from the respective
tanks to the proppant carrier fluid line 340 and from there the
final fracturing fluid (labeled "final slurry") is delivered to the
well, off to the right.
[0095] Overflow line 350 allows clean fluid in an upstream tank to
feed into a downstream tank, thus allowing space in the upstream
tank for proppant to be added thereto. Thus, branches 351, 352, and
353 allow used fluid to combine with the clean water to fill or
displace a given tank.
[0096] Recycle line 360 allows for excess clean fluid to be emptied
from a tank before proppant has been added and recycled as makeup
water in e.g. slurry stream, fluid injection stream and the like.
Thus, branches 361, 362, and 363 allow for clean fluid to be
displaced from each tank and pumped into other fluid streams. For
example, the displaced fluid from Tank 1 311 flows through branch
361 and is pumped by the displacement pump 335 back to Tank 2 312
through branch 352 while the valves on branches 351, 353 are
closed. Ideally, displaced fluid from a first tank will be used to
form part of the clean fluid needed to displace the proppant slurry
from a second tank. The partially drained first tank will then have
free space available for accepting proppant without excess fluid
overflow.
[0097] The tank filling and emptying operations occur sequentially,
as expressed in steps described in Table 2, wherein at step 1, tank
311 is full of a proppant/water slurry, already exiting via the
slurry line 341 to combine with the proppant carrier to make the
final proppant fluid. At the same time, tank 312 is full of water
having just been cleaned, and tank 313 is partially full of water,
allowing ingress of proppant into tank 313 at this time. By
utilizing the multi-tank design and sequential operations, a
continuous flow of proppant is possible.
TABLE-US-00004 TABLE 3 Low-pressure direct proppant injection
concept process steps Tank 311 Tank 312 Tank 313 Beginning
Beginning Beginning Step Status Action Status Action Status Action
1 Full of proppant Displacing into line Full of water Pumping into
Tank 40% Full of Filling with proppant slurry 311 water 2 Full of
water Pumping into Tank 313 40% Full of water Filling with Full of
proppant Displacing into line proppant slurry 3 40% Full of water
Filling with proppant Full of proppant Displacing into line Full of
water Pumping into Tank 2 slurry
[0098] In more detail, FIG. 4 shows a schematic of the three stages
that each tank 411, 412, and 413 undergo. In stage 1, the proppant
slurry in the first tank 411 is displaced via branch 441 and
combined with proppant slurry from other tanks in proppant slurry
line 444. The proppant slurry line 444 then combines with a
concentrated proppant carrier in line 440 to form the final
proppant fluid for injection. The clean fluid necessary to displace
the slurry and remove all proppant from the tank 411 partially
comprises clean fluid from a second tank in the system and from the
clean fluid source 420.
[0099] Once the proppant slurry is completely displaced from the
tank 411, the tank 411 will be full of clean fluid, such as water,
in Stage 2. During Stage 2 approximately 40-60% by tank volume of
the clean fluid in the tank 411 will be displaced or emptied
through the recycle line 461 for use in displacing the proppant
slurry from a third tank. Though not shown in FIG. 4, the displaced
clean fluid may also be used as makeup flow for the low-pressure
proppant slurry line 444.
[0100] This removal of clean fluid frees up space within the tank
411 for accepting proppant without potential fluid overflow. Thus,
in Stage 3, the proppant from the hopper 401 will be gravity
drained into the tank 411 to form a proppant slurry.
[0101] Stages 1-3 are performed by for all tanks within a system
simultaneously, but in a staggered fashion. As such, the number of
tanks used in the system is preferably multiples of three. However,
it is possible to modify the system for any number of tanks,
provided there are at least 3 tanks. For instance, in a four-tank
system, two tanks can undergo stage 1 while the remaining two tanks
undergo stage 2 and 3.
[0102] FIG. 4 also shows the optional dilution line 430 wherein
clean fluid 420 is introduced into the concentrated proppant
carrier fluid line 440. This is shown for clarity only and is not a
requirement in the three stage operation.
[0103] The proppant slurry is combined with the concentrated
proppant carrier fluid to form a final proppant fluid, the carrier
fluid serving to carry the proppant more effectively than a thin
fluid could. This final proppant fluid can be introduced under
low-pressure conditions into a direct injection system upstream
from the pumping units. The high-pressure pump assembly is
configured to deliver the fluid mixture therein to a downstream
component at an injection pressure, wherein the injection pressure
is greater than the fracture fluid blending pressure.
[0104] Although only a few exemplary embodiments have been
described in detail above, those skilled in the art will readily
appreciate that many modifications are possible in the example
embodiments without materially departing from this invention.
Accordingly, all such modifications are intended to be included
within the scope of this disclosure as defined in the following
claims. In the claims, means-plus-function clauses are intended to
cover the structures described herein as performing the recited
function and not only structural equivalents, but also equivalent
structures. Thus, although a nail and a screw may not be structural
equivalents in that a nail employs a cylindrical surface to secure
wooden parts together, whereas a screw employs a helical surface,
in the environment of fastening wooden parts, a nail and a screw
may be equivalent structures. It is the express intention of the
applicant not to invoke 35 U.S.C. .sctn.112, paragraph 6 for any
limitations of any of the claims herein, except for those in which
the claim expressly uses the words `means for` together with an
associated function.
[0105] The following are incorporated by reference herein in their
entireties for all purposes.
[0106] US20100243255
[0107] U.S. Pat. No. 7,044,220
[0108] U.S. Pat. No. 7,281,581
[0109] U.S. Pat. No. 7,325,608
[0110] U.S. Pat. No. 8,061,424
[0111] U.S. Pat. No. 6,776,235
[0112] US20080135242
[0113] US20080128131
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