Note: Descriptions are shown in the official language in which they were submitted.
CA 02777449 2013-11-18
Serie 9189
LIQUEFIED INDUSTRIAL GAS BASED SOLUTION IN HYDRAULIC
FRACTURING
Technical Field
This invention relates to a method of fracturing subterranean formations
penetrated
by a well bore utilizing liquid carbon dioxide or liquid nitrogen as the
carrier for
chemicals and/or biocides instead of water.
Background
The treatment of subterranean formations penetrated by a well bore to
stimulate the
production of hydrocarbons therefrom or the ability of the formation to accept
injected fluids has long been known in the art. One of the most common methods
of
increasing productivity of a hydrocarbon-bearing formation is to subject the
formation
to a fracturing treatment. This treatment is effected by injecting a liquid,
gas or two-
phase fluid which generally is referred to as a fracturing fluid down the well
bore at
sufficient pressure and flow rate to fracture the subterranean formation. A
proppant
material such as sand, fine gravel, sintered bauxite, glass beads or the like
can be
introduced into the fractures to keep them open. The propped fracture provides
larger flow channels through which an increased quantity of a hydrocarbon can
flow,
thereby increasing the productive capability of a well.
A traditional hydraulic fracturing technique utilizes a water or oil-based
fluid to
fracture a hydrocarbon-bearing formation.
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Summary
The present invention is a cryogenic subterranean fracturing fluid, comprising
a
liquefied industrial gas and a first additive. The liquefied industrial gas
may be
liquefied carbon dioxide, liquefied nitrogen, or a blend of the two. The first
additive
may be a biocide. The liquefied industrial gas mixture should be substantially
free of
water. In this context, substantially free of water means less than 10% water
by
volume, or preferably less than 5% water by volume. In addition to the first
additive,
a proppant may be added to the fracturing fluid. Non-limiting examples of a
biocide
include glutaraldehyde, quaternary ammonium chloride, tetrakis hydroxymethyl-
phosphonium sulfate, or a combination thereof. In addition to the biocide
and/or
proppant additional additives may be added to the liquefied industrial gas as
required. Non-limiting examples of such additives include ozone, a friction
reducer,
an acid, a gelling agent, a breaker, a scale inhibitor, a clay stabilizer, a
corrosion
inhibitor, an iron controller, an oxygen scavenger, a surfactant, a cross-
linker, a non-
emulsifier, a pH adjusting agent, or any combination thereof.
Non-limiting examples of a cross-linker include petroleum distillate,
hydrotreated
light petroleum distillate, potassium metaborate, triethanolamine zirconate,
sodium
tetraborate, boric acid, zirconium complex, borate salts, ethyleneglycol,
methanol, or
a combination thereof.
Non-limiting examples of a non-emulsifier include lauryl sulfate, isopronanol,
ethylene glycol, or a combination thereof. Non-limiting examples of a pH
adjusting
agent include sodium hydroxide, potassium hydroxide, acetic acid, sodium
carbonate, potassium carbonate, or a combination thereof.
Non-limiting examples of an acid include hydrochloric acid. Non-limiting
examples of
a gelling agent include one or more of the following: guar gum, petroleum
distillate,
hydrotreated light petroleum distillate, methanol, polysaccharide blend,
ethylene
glycol, hydroxyethyl cellulose, or a combination thereof.
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Non-limiting examples of a breaker include one or more of the following:
ammonium
persulfate, magnesium peroxide, magnesium oxide, calcium chloride, sodium
chloride, or a combination thereof.
Non-limiting examples of a corrosion inhibitor include one or more of the
following:
isopropanol , methanol , formic Acid , acetaldehyde, N,N-dimethyl formamide,
or a
combination thereof. Non-limiting examples of an oxygen scavenger include
ammonium bisulfate.
Non-limiting examples of a surfactant include isopropanol. Non-limiting
examples of
a clay stabilizer include one or more of the following: choline chloride,
tetramethyl
ammonium chloride, sodium chloride, or a combination thereof.
Non-limiting examples of a friction reducer include one or more of the
following:
polyacrylamide, petroleum distillate, hydrotreated light petroleum distillate,
methanol,
ethylene glycol, or a combination thereof.
Non-limiting examples of a scale inhibitor include one or more of the
following:
ethylene glycol, copolymer of acrylamide and sodium acrylate, sodium
polycarboxylate, phosphonic acid salt, or a combination thereof.
Non-limiting examples of an iron controller include one or more of the
following: citric
acid, acetic acid, thioglycolic acid, 2-hydroxy 1, 2, 3-propaneticoboxylic
acid, sodium
erythorbate, or a combination thereof.
In accordance with another aspect of the present invention, there is provided
a
cryogenic subterranean fracturing fluid, comprising a liquefied industrial
gas, a first
additive, and a proppant, wherein said liquefied industrial gas, and said
first additive
are substantially free of water.
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In accordance with another aspect of the present invention, there is provided
the
cryogenic subterranean fracturing fluid wherein said first additive is
introduced into
said liquefied industrial gas prior to said introduction into said formation,
and stored
in admixed liquid form.
In accordance with another aspect of the present invention, there is provided
the
cryogenic subterranean fracturing fluid wherein said first additive is
introduced into
said liquid carbon dioxide In such a way as to form miscible liquid with
liquid carbon
dioxide.
In accordance with another aspect of the present invention, there is provided
the
cryogenic subterranean fracturing fluid wherein said first additive is
introduced into
said liquid nitrogen in such a way as to form discrete, frozen masses, thereby
producing a slurry with the liquid nitrogen.
In accordance with another aspect of the present invention, there is provided
a
method of fracturing a subterranean formation penetrated by a well bore
comprising:
introducing cryogenic subterranean fracturing fluid, comprising a liquefied
industrial
gas, a proppant, and at least a first additive into said formation.
In accordance with another aspect of the present invention, there is provided
a
method of fracturing a subterranean formation penetrated by a well bore
comprising:
introducing cryogenic subterranean fracturing fluid, comprising a liquefied
industrial
gas, a proppant, and at least a first additive into said formation, wherein
said
cryogenic subterranean fracturing fluid is substantially free of water.
Description of Preferred Embodiments
Illustrative embodiments of the invention are described below. While
particular
embodiments of the present invention have been described, it would be obvious
to
those skilled in the art that various other changes and modifications can be
made.
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The scope of the claims should not be limited by the embodiments set forth in
the
description, but should be given the broadest interpretation consistent with
the
specification as a whole.
It will of course be appreciated that in the development of any such actual
embodiment, numerous implementation-specific decisions must be made to achieve
the developer's specific goals, such as compliance with system-related and
business-related constraints, which will vary from one implementation to
another.
Moreover, it will be appreciated that such a development effort might be
complex
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and time-consuming, but would nevertheless be a routine undertaking for those
of
ordinary skill in the art having the benefit of this disclosure.
A hydraulic fracture is formed by pumping the fracturing fluid into the
wellbore at a
rate sufficient to increase pressure downhole to exceed that of the fracture
gradient
of the rock. The rock cracks and the fracture fluid continues farther into the
rock,
extending the crack still farther, and so on. Operators typically try to
maintain
"fracture width", or slow its decline, following treatment by introducing a
proppant
into the injected fluid, a material, such as grains of sand, ceramic, or other
particulates, that prevent the fractures from closing when the injection is
stopped.
Consideration of proppant strengths and prevention of proppant failure becomes
more important at deeper depths where pressure and stresses on fractures are
higher. The propped fracture is permeable enough to allow the flow of
formation
fluids to the well. Formation fluids include gas, oil, salt water, fresh water
and fluids
introduced to the formation during completion of the well during fracturing.
The location of one or more fractures along the length of the borehole is
strictly
controlled by various different methods which create or seal-off holes in the
side of
the wellbore. Typically, hydraulic fracturing is performed in cased wellbores
and the
zones to be fractured are accessed by perforating the casing at those
locations.
The fluid injected into the rock is typically a slurry of water, proppants,
and chemical
additives. Additionally, gels, foams, and compressed gases, including
nitrogen,
carbon dioxide and air can be injected.
Various types of proppant include silica sand, resin-coated sand, and man-made
ceramics. These vary depending on the type of permeability or grain strength
needed. The most commonly utilized proppant is silica sand. However, proppants
of
uniform size and shape, such as a ceramic proppant, is believed to be more
effective. Due to a higher porosity within the fracture, a greater amount of
oil and
natural gas is liberated. Sand containing naturally radioactive minerals is
sometimes
used so that the fracture trace along the wellbore can be measured.
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Chemical additives are applied to tailor the injected material to the specific
geological situation, protect the well, and improve its operation, though the
injected
fluid is approximately 98-99.5% water, varying slightly based on the type of
well. The
composition of injected fluid is sometimes changed as the fracturing job
proceeds.
Often, acid is initially used to scour the perforations and clean up the near-
wellbore
area. Afterward, high pressure fracture fluid is injected into the wellbore,
with the
pressure above the fracture gradient of the rock. This fracture fluid contains
water-
soluble gelling agents (such as guar gum) which increase viscosity and
efficiently =
deliver the proppant into the formation. As the fracturing process proceeds,
viscosity
reducing agents such as oxidizers and enzyme breakers are sometimes then added
to the fracturing fluid to deactivate the gelling agents and encourage
flowback. The
proppant's purpose is primarily to provide a permeable and permanent filler to
fill the
void created during the fracturing process.
At the end of the job the well is commonly flushed with water (sometimes
blended
with a friction reducing chemical) under pressure. Injected fluid is to some
degree
recovered and is managed by several methods, such as underground injection
control, treatment and discharge, recycling, or temporary storage in pits or
containers while new technology is being developed to better handle wastewater
and improve reusability. Although the concentrations of the chemical additives
are
very low, the recovered fluid may be harmful due in part to hydrocarbons
picked up
from the formation.
Hydraulic fracturing equipment used in oil and natural gas fields usually
consists of a
slurry blender, one or more high pressure, high volume fracturing pumps
(typically
powerful triplex, or quintiplex pumps) and a monitoring unit. Associated
equipment
includes fracturing tanks, one or more units for storage and handling of
proppant,
high pressure treating iron, a chemical additive unit (used to accurately
monitor
chemical addition), low pressure flexible hoses, and many gauges and meters
for
flow rate, fluid density, and treating pressure. Fracturing equipment operates
over a
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range of pressures and injection rates, and can reach up to 100 megapascals
(15,000 psi) and 265 litres per second (9.4 cu ft/s) (100 barrels per minute).
The present invention is a cryogenic subterranean fracturing fluid, that
includes at
least a liquefied industrial gas and a first additive. The liquefied
industrial gas may
be liquefied carbon dioxide, liquefied nitrogen, or a blend of the two. Other
liquefied industrial gases may be included in a mixture, but the primary
components
will be liquefied carbon dioxide or liquefied nitrogen. The liquefied
industrial gas
mixture should be substantially free of water. In this context, substantially
free of
water means less than 10% water by volume, or preferably less than 5% water by
volume. In addition to the first additive, a proppant may be added to the
fracturing
fluid.
As discussed above, in hydraulic or gas fracturing, a number of additives are
routinely added as the particular site requires. In the present invention, the
first
additive may be a biocide. The biocide may be any chemical known to one of
ordinary skill in the art. Non-limiting examples of such biocides include
glutaraldehyde, quaternary ammonium chloride, tetrakis hydroxymethyl-
phosphonium sulfate, or a combination thereof.
In addition to the first additive, a proppant may be added to the fracturing
fluid. Any
proppant known in the art may be used. Non-limiting examples of such proppants
include quartz sand, aluminum balls, walnut shells, glass beads, plastic
balls,
ceramic, and resin-clad sand.
In addition to the biocide and/or proppant, a second additive, or additional
additives,
may be added to the liquefied industrial gas as required. Any additional
additives
known in the art may be added. Non-limiting examples of such additives include
ozone, a friction reducer, an acid, a gelling agent, a breaker, a scale
inhibitor, a clay
stabilizer, a corrosion inhibitor, an iron controller, an oxygen scavenger, a
surfactant,
a cross-linker, a non-emulsifier, a pH adjusting agent, or any combination
thereof.
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The combination of liquefied industrial gas, proppant, biocide and any
additional
additives should be substantially free of water.
The additives may be introduced into the liquefied industrial gas prior to the
introduction into said formation, and stored in admixed liquid form. The
additives
may introduced into the liquid nitrogen in such a way as to form discrete,
frozen
masses, thereby producing a slurry with the liquid nitrogen. The additives may
be
introduced into the liquid carbon dioxide in such a way as to form miscible
liquid with
the liquid carbon dioxide.
Any cross-linker known to one skilled in the art may added, as needed, to the
liquefied industrial gas. Non-limiting examples of such cross-linkers include
petroleum distillate, hydrotreated light petroleum distillate, potassium
metaborate,
triethanolamine zirconate, sodium tetraborate, boric acid, zirconium complex,
borate
salts, ethylene glycol, methanol, or a combination thereof.
Any non-emulsifier known to one skilled in the art may added, as needed, to
the
liquefied industrial gas. Non-limiting examples of such non-emulsifiers
include non-
emulsifiers lauryl sulfate, isopronanol, ethylene glycol, or a combination
thereof.
Any pH adjusting agent known to one skilled in the art may added, as needed,
to the
liquefied industrial gas. Non-limiting examples of such pH adjusting agents
include
is sodium hydroxide, potassium hydroxide, acetic acid, sodium carbonate,
potassium
carbonate, or a combination thereof.
Any acid known to one skilled in the art may added, as needed, to the
liquefied
industrial gas. A non-limiting example of such an acid is hydrochloric acid.
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Any gelling agent known to one skilled in the art may added, as needed, to the
liquefied industrial gas. Non-limiting examples of such gelling agents include
guar
gum, petroleum distillate, hydrotreated light petroleum distillate, methanol,
polysaccharide blend, ethylene glycol, hydroxyethyl cellulose, or a
combination
thereof.
Any breaker known to one skilled in the art may added, as needed, to the
liquefied
industrial gas. Non-limiting examples of such breakers include ammonium
persulfate, magnesium peroxide, magnesium oxide, calcium chloride, sodium
chloride, or a combination thereof.
Any corrosion inhibiter known to one skilled in the art may added, as needed,
to the
liquefied industrial gas. Non-limiting examples of such corrosion inhibitor
include
isopropanol , methanol , formic Acid , acetaldehyde, N,N-dimethyl formamide,
or a
combination thereof.
Any oxygen scavenger known to one skilled in the art may added, as needed, to
the
liquefied industrial gas. A non-limiting example of such a corrosion inhibitor
is
ammonium bisulfate.
Any surfactant known to one skilled in the art may added, as needed, to the
liquefied
industrial gas. A non-limiting example of such a surfactant is isopropanol.
Any clay stabilizer known to one skilled in the art may added, as needed, to
the
liquefied industrial gas. Non-limiting examples of such clay stabilizer
include
choline chloride, tetramethyl ammonium chloride, sodium chloride, or a
combination
thereof.
Any friction reducer known to one skilled in the art may added, as needed, to
the
liquefied industrial gas. Non-limiting examples of such friction reducer
include
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polyacrylamide, petroleum distillate, hydrotreated light petroleum distillate,
methanol,
ethylene glycol, or a combination thereof.
Any scale inhibiter known to one skilled in the art may added, as needed, to
the
liquefied industrial gas. Non-limiting examples of such scale inhibitor
include
ethylene glycol, copolymer of acrylamide and sodium acrylate, sodium
polycarboxylate, phosphonic acid salt, or a combination thereof.
Any iron controller known to one skilled in the art may added, as needed, to
the
liquefied industrial gas. Non-limiting examples of such iron controller
include citric
acid, acetic acid, thioglycolic acid, 2-hydroxy 1, 2, 3-propaneticoboxylic
acid, sodium
erythorbate, or a combination thereof.
This invention also includes a method of fracturing a subterranean formation
penetrated by a well bore comprising: introducing cryogenic subterranean
fracturing
fluid, comprising a liquefied industrial gas, a proppant, and at least a first
additive
into said formation.
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