U.S. patent application number 14/607107 was filed with the patent office on 2016-07-28 for well treatment.
The applicant listed for this patent is SCHLUMBERGER TECHNOLOGY CORPORATION. Invention is credited to J. Ernest Brown, Iain M. Cooper, Dmitriy Potapenko.
Application Number | 20160215604 14/607107 |
Document ID | / |
Family ID | 56433241 |
Filed Date | 2016-07-28 |
United States Patent
Application |
20160215604 |
Kind Code |
A1 |
Potapenko; Dmitriy ; et
al. |
July 28, 2016 |
WELL TREATMENT
Abstract
A combustible foamed fluid energized with gaseous fuel and
combustion oxidant sources. Also, an energized fluid system, a
treatment method using the combustible foamed fluid, and a method
to prepare the combustible foamed fluid are disclosed.
Inventors: |
Potapenko; Dmitriy; (Sugar
Land, TX) ; Brown; J. Ernest; (Sugar Land, TX)
; Cooper; Iain M.; (Houston, TX) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
SCHLUMBERGER TECHNOLOGY CORPORATION |
Sugar Land |
TX |
US |
|
|
Family ID: |
56433241 |
Appl. No.: |
14/607107 |
Filed: |
January 28, 2015 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
E21B 43/267 20130101;
E21B 43/263 20130101 |
International
Class: |
E21B 43/243 20060101
E21B043/243; E21B 43/25 20060101 E21B043/25; E21B 43/267 20060101
E21B043/267 |
Claims
1. A treatment method, comprising: introducing downhole a quantity
of a treatment fluid comprising a combustible foamed fluid
comprising a mixture of a fuel source and a combustion oxidant
source, wherein a gas phase of the foam comprises the mixture of
the fuel source and the combustion oxidation source; placing the
combustible foamed fluid in a downhole structure under
non-combustion conditions free of an active ignition source;
thereafter igniting the combustible foamed fluid to combust the
fuel source in the downhole structure forming a post-combustion
fluid.
2. (canceled)
3. The method of claim 1, wherein the combustion decomposes the
foamed fluid.
4. The method of claim 1, further comprising cooling the
post-combustion fluid to a reduced specific volume relative to the
combustible foamed fluid.
5. The method of claim 1, wherein the treatment fluid further
comprises proppant.
6. The method of claim 1, wherein the downhole structure comprises
a fracture above a fracturing pressure.
7. The method of claim 1, wherein the downhole structure comprises
a formation matrix below a fracturing pressure.
8. The method of claim 1, wherein the fuel source is selected from
hydrogen, hydrocarbon gases, or a mixture thereof.
9. The method of claim 1, wherein the combustion oxidant source
comprises molecular oxygen.
10. The method of claim 1, further comprising preparing the
combustible foamed fluid at a surface location and introducing the
mixture into a wellbore.
11. The method of claim 1, further comprising introducing the
combustion oxidant source into a wellbore in a first stream
separate from a second stream comprising the fuel source, and
mixing the first and second streams downhole to form the
combustible foamed fluid.
12. An energized fluid system, comprising: a combustible energized
fluid comprising a combustible gaseous mixture dispersed in a
continuous liquid phase; a downhole structure to receive the
combustible foamed fluid under non-combustion conditions free of an
active ignition source; and an ignition source in communication
with the downhole structure activatable to initiate combustion of
the dispersed gaseous mixture.
13. The energized fluid system of claim 12, wherein the combustible
gaseous mixture comprises oxygen mixed with a fuel source selected
from hydrogen, hydrocarbon gases and combinations thereof.
14. The energized fluid system of claim 12, wherein the downhole
structure comprises a formation matrix.
15. The energized fluid system of claim 12, wherein the structure
comprises a fracture.
16. The energized fluid system of claim 12, further comprising a
controller to remotely activate the ignition source, wherein the
ignition source comprises an electrical or chemical igniter.
17. A method, comprising: dispersing a gaseous fuel source and a
gaseous combustion oxidant source into a continuous liquid phase to
form a combustible foamed fluid; and isolating the combustible
foamed fluid in a downhole structure under non-combustion
conditions free of an active ignition source.
18. The method of claim 17, wherein the gaseous fuel source and
gaseous combustion oxidant are delivered in separate streams
through a wellbore and mixed downhole.
19. The method of claim 17, wherein the gaseous fuel source
comprises hydrogen, the gaseous combustion oxidant comprises
oxygen, and the continuous liquid phase comprises water, and
further comprising passing the liquid phase through an electrolysis
cell to generate the oxygen and hydrogen in the liquid phase.
20. The method of claim 17, wherein the downhole structure
comprises a fracture above a fracturing pressure, or a formation
matrix below the fracturing pressure.
Description
RELATED APPLICATION DATA
[0001] None.
BACKGROUND
[0002] The statements in this section merely provide background
information related to the present disclosure and may not
constitute prior art.
[0003] Foamed fluids, including energized fluids, are often used in
downhole applications such as fracturing and other treatments. In
some applications it may be desired to quickly break, dissipate,
and/or flow back foamed fluids in downhole applications, e.g., to
implement fracture closure, or to otherwise rapidly change the
properties of the foamed fluid after introducing it into the
wellbore.
[0004] Foamed fluids may be used in matrix treatments, for example,
in the injection of acidizing agents, chelating agents, paraffins,
scale inhibitors, and so on.
[0005] As another example, foamed fluids are often used as carrying
fluids to place proppant and/or other solids into a fracture. The
proppant in such applications may be homogeneously or
heterogeneously placed in a fracture, or sometimes in a combination
of such placement modalities. In US 2014/0262264 by Potapenko et
al. (also published as WO 2014/143490A1), incorporated herein by
reference, for example, a method for treating a subterranean
formation wherein a treatment slurry, which may include a foamed
carrying fluid among others, is injected into a fracture to form a
substantially uniformly distributed mixture of solid particulate
and agglomerant; and transforming the substantially uniform mixture
into areas that are rich in solid particulate and areas that are
substantially free of solid particulate, wherein the solid
particulate and the agglomerant have substantially dissimilar
velocities in the fracture so that the transformation results from
the substantially dissimilar velocities, e.g., during forced
fracture closure or flowback.
[0006] The industry is thus desirous of improvements to carrying
fluids and/or foamed fluids and/or methods of preparing and using
them for various applications.
SUMMARY
[0007] This summary is provided to introduce a selection of
concepts that are further described below in the detailed
description. This summary is not intended to identify key or
essential features of the claimed subject matter, nor is it
intended to be used as an aid in limiting the scope of the claimed
subject matter. The statements made merely provide information
relating to the present disclosure, and may describe some
embodiments illustrating the subject matter of this
application.
[0008] The present disclosure relates in some embodiments to a
combustible foamed fluid energized with a gaseous phase comprising
both fuel and combustion oxidant sources, as well as to energized
fluid systems, and treatment methods, relating to the combustible
foamed fluid, and methods to prepare the combustible foamed
fluid.
[0009] In some embodiments, a treatment method may comprise
introducing downhole a quantity of a treatment fluid comprising a
combustible foamed fluid comprising a mixture of a fuel source and
a combustion oxidant source, placing the combustible foamed fluid
in a downhole structure under non-combustion conditions free of an
active ignition source, and thereafter igniting the combustible
foamed fluid to combust the fuel source in the downhole structure
forming a post-combustion fluid.
[0010] In some embodiments, a gas phase of the foam may comprise a
mixture of the fuel source and the combustion oxidation source. In
some embodiments, the mixture may take the form of a gas phase of
homogenous composition dispersed in a continuous liquid phase, and
in further embodiments, the gas phase may be heterogeneous, e.g.,
the fuel source and combustion oxidation source may be separately
dispersed or dispersed in mixtures of varying proportions.
[0011] In some embodiments, the combustion may decompose the foamed
fluid. In some examples, the decomposition may occur such as by
vaporizing the liquid phase to an extent that a gas phase or mist
is formed, by forming combustion product(s) that condense to
liquid(s), or are miscible with the liquid phase, by thermally
decomposing a foaming agent, by forming a defoaming agent, or the
like, or a combination thereof.
[0012] In some embodiments, the method may further comprise cooling
the post-combustion fluid to a reduced specific volume relative to
the combustible foamed fluid. In some examples, the post combustion
fluid may contain a lower proportion of non-condensable,
non-soluble gases at the ambient formation pressure and temperature
conditions, e.g., a mixture of hydrogen and oxygen will form water,
which upon equilibration to ambient formation pressure and
temperature conditions and at least partial condensation, will
reduce the total volume of the resultant fluid relative to that of
the pre-combustion foam.
[0013] In some embodiments of the method, the treatment fluid may
further comprise proppant and/or the downhole structure may
comprise a fracture, e.g., above a fracturing pressure of the
formation. In some examples the treatment fluid may be a fracturing
fluid, e.g., a pad stage, proppant stage, flush stage, or the
like.
[0014] In some embodiments, the treatment fluid may further
comprise a matrix treatment agent, and/or the downhole structure
may comprise a formation matrix, e.g., below a fracturing pressure
of the formation.
[0015] In some embodiments, the combustion may improve the
effectiveness of treatment, reduce flowback volumes, minimize
formation damage, accelerate return to production following
treatment, or the like.
[0016] In some embodiments, the fuel source is selected from
hydrogen, hydrocarbon gases, or a mixture thereof, and/or the
combustion oxidant source may comprise oxygen, e.g., molecular
oxygen, in the form of air, oxygen-enriched air, purified oxygen,
oxygen formed by chemical reaction, or the like.
[0017] In some embodiments, the combustible foam is prepared at a
surface location and introduced into a wellbore, and in other
embodiments, the combustion oxidant source is introduced into the
wellbore in a first stream separate from a second stream comprising
the fuel source, and the first and second streams are mixed
downhole to form the combustible foamed fluid.
[0018] The present disclosure also relates to embodiments of an
energized fluid system comprising a combustible foamed fluid
comprising a combustible gaseous mixture dispersed in a continuous
liquid phase, a downhole structure to receive the combustible
foamed fluid under non-combustion conditions free of an active
ignition source, and an ignition source in communication with the
downhole structure activatable to initiate combustion of the
dispersed gaseous mixture. In some embodiments, the combustible
foamed fluid is substantially free of inert gas, e.g., comprised of
less than 5 vol % inert gases such as nitrogen, e.g., the mixture
may be comprised of oxygen mixed with a fuel source selected from
hydrogen, hydrocarbon gases, and the like, including combinations
thereof.
[0019] In some embodiments, the structure may comprise a wellbore,
a fracture, a formation matrix, or the like.
[0020] In some embodiments, the ignition source may comprise an
igniter, e.g., an electrical or chemical igniter, and/or the
energized fluid system may further comprise a controller to
activate the ignition source, which controller may automatically
activate the ignition source, e.g., after a predetermined time
period or at predetermined pressure, temperature, or chemical or
other downhole conditions, and/or which may be remotely located,
e.g., downhole or at the surface, for remotely activating the
ignition source.
[0021] The present disclosure also relates to embodiments of a
method, comprising dispersing a gaseous fuel source and a gaseous
combustion oxidant source into a continuous liquid phase to form a
combustible foamed fluid, and isolating the combustible foamed
fluid in a downhole structure under non-combustion conditions free
of an active ignition source. In some embodiments, the gaseous fuel
source and gaseous combustion oxidant may be delivered in separate
streams through a wellbore and mixed downhole, or the fuel source
and combustion oxidant may be mixed at the surface and the mixture
pumped downhole, e.g., in a combustible foam prepared at the
surface.
[0022] In some other embodiments, the method may comprise passing
the liquid phase through an electrolysis cell, either downhole or
at the surface, to electrolytically generate the fuel and
combustion oxidant sources, e.g., where the liquid phase is
aqueous, the gaseous fuel source may be hydrogen, and the gaseous
combustion oxidant may be oxygen.
[0023] In some embodiments, the downhole structure comprises a
fracture above a fracturing pressure, or a formation matrix below
the fracturing pressure, or a combination of a fracture and a
formation matrix.
BRIEF DESCRIPTION OF THE DRAWINGS
[0024] None.
DETAILED DESCRIPTION
[0025] In the following description, numerous details are set forth
to provide an understanding of the present disclosure. However, it
may be understood by those skilled in the art that the methods of
the present disclosure may be practiced without these details and
that numerous variations or modifications from the described
embodiments may be possible. Certain statements made in this
section may merely provide background information related to the
present disclosure, but may not constitute prior art.
[0026] At the outset, it should be noted that in the development of
any such actual embodiment, numerous implementation-specific
decisions may 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 and time consuming but would nevertheless be a
routine undertaking for those of ordinary skill in the art having
the benefit of this disclosure. In addition, the composition
used/disclosed herein can also comprise some components other than
those cited. In the summary and this detailed description, each
numerical value should be read once as modified by the term "about"
(unless already expressly so modified), and then read again as not
so modified unless otherwise indicated in context. Also, in the
summary and this detailed description, it should be understood that
a range listed or described as being useful, suitable, or the like,
is intended to include support for any conceivable sub-range within
the range at least because every point within the range, including
the end points, is to be considered as having been stated. For
example, "a range of from 1 to 10" is to be read as indicating each
possible number along the continuum between about 1 and about 10.
Furthermore, one or more of the data points in the present examples
may be combined together, or may be combined with one of the data
points in the specification to create a range, and thus include
each possible value or number within this range. Thus, (1) even if
numerous specific data points within the range are explicitly
identified, (2) even if reference is made to a few specific data
points within the range, or (3) even when no data points within the
range are explicitly identified, it is to be understood (i) that
the inventors appreciate and understand that any conceivable data
point within the range is to be considered to have been specified,
and (ii) that the inventors possessed knowledge of the entire
range, each conceivable sub-range within the range, and each
conceivable point within the range. Furthermore, the subject matter
of this application illustratively disclosed herein suitably may be
practiced in the absence of any element(s) that are not
specifically disclosed herein.
[0027] The following definitions are provided in order to aid those
skilled in the art in understanding the detailed description. Terms
may also be defined elsewhere in the specification and/or
claims.
[0028] The term "downhole structure" includes any subterranean
arrangement of materials below the surface that may hold, contain,
be filled with, or allow the passage of a fluid, such as, without
limitation, wellbore, drill pipe or string, tubing, casing,
wireline, screen, annulus, fracture, tool, matrix, cavern, lost
circulation zone, vug, pores, perforations, and the like. A
downhole structure thus refers to any downhole feature without
limitation through which fluid may flow or pass, including, but not
limited to, a formation matrix, screen or other porous media, or
surface thereof, fracture, formation void, vug, wormhole, fluid
loss zone, chamber, perforation, valve, opening, or a line, tubing
pipe or similar flow conduit, such as casing, tubing (including
coiled tubing), drill pipe, and including any annulus or space
between any of such structures, and any combinations thereof, or
the like.
[0029] The term "wellbore" is a drilled hole or borehole, including
the openhole or uncased portion of the well that is drilled during
a treatment of a subterranean formation. The term "wellbore" does
not include the wellhead, or any other similar apparatus positioned
over the wellbore or at the surface. The wellbore or other downhole
structure may be horizontally or vertically disposed, or
sloped.
[0030] The term "treatment" or "treating" refers to any
subterranean operation that uses a fluid in conjunction with a
desired function and/or for a desired purpose. The term "treatment"
or "treating" does not imply any particular action by the
fluid.
[0031] The term "injecting" describes the introduction of a new or
different element into a first element. In the context of this
application, injection of a fluid, solid or other compound may
occur by any form of physical introduction, including but not
limited to pumping.
[0032] The term "fracturing" refers to the process and methods of
breaking down a geological formation and creating a fracture, i.e.,
the geological formation around a well bore, in order to increase
production rates from a hydrocarbon reservoir. Fracture "creation"
includes initiation of a new fracture or fracture branch, as well
as propagation and/or expansion of a fracture. The fracturing
methods otherwise use techniques known in the art.
[0033] "Partial fracturing" refers to the formation of one or
especially a plurality fractures formed within a formation which do
not communicate directly to the wellbore, or do not connect to a
fracture that communicates directly to the wellbore and/or form a
part of a fracture network isolated from direct communication to
the wellbore.
[0034] The term "matrix acidizing" refers to a process where
treatments of acid or other reactive chemicals are pumped into the
formation at a pressure below which a fracture can be created. The
matrix acidizing methods otherwise use techniques known in the
art.
[0035] The terms "combustible fluid," "auto-combustible fluid," and
similar terms are used interchangeably herein refer to a mixture
comprising a combustion-sustaining mix of fuel and oxidant sources,
i.e., through which a flame can be propagated in situ by an
ignition source without the requirement of exogenous reactants, as
in an enclosed container.
[0036] The term "combustion" refers to the act or instance of
burning of a fuel with an oxidant to release energy, usually in the
form of heat and light, and also including the terms "detonation"
and "explosion" referring to combustion in which the flame
propagation exceeds the acoustic velocity of the reactant media, as
well as "ignition" referring to the initiation of combustion.
[0037] The term "non-combustion conditions" refers to a stable
combustible fluid that is not in fluid communication with a flame
or other active ignition source such as a static electrical
spark.
[0038] The term "ignition source" refers to a composition, device
or mechanism capable of initiating combustion of a combustible
fluid.
[0039] The terms "energized fluid" and "foam" refer to a fluid
which when subjected to a low pressure environment liberates or
releases gas from solution or dispersion, for example, a liquid
containing dissolved gases. Foams or energized fluids are stable
mixtures of gases and liquids that form a two-phase system. Foam
and energized fluids are generally described by their foam quality,
i.e. the ratio of gas volume to the foam volume (fluid phase of the
treatment fluid), i.e., the ratio of the gas volume to the sum of
the gas plus liquid volumes. If the foam quality is between 52% and
95%, the energized fluid is usually called foam. Above 95%, foam is
generally changed to mist. In the present patent application, the
terms "energized fluid" and "foam" may be used interchangeably
herein, and refer to any stable mixture of gas and liquid,
regardless of the foam quality unless context indicates otherwise.
Energized fluids comprise any of: (a) Liquids that at downhole
conditions of pressure and temperature are close to saturation with
a species of gas; for example the liquid can be aqueous and the gas
nitrogen or carbon dioxide or hydrogen or oxygen or air or methane
or fuel gas, etc.; associated with the liquid and gas species and
temperature is a pressure called the bubble point, at which the
liquid is fully saturated; at pressures below the bubble point, gas
emerges from solution; (b) Foams, consisting generally of a gas
phase, an aqueous phase and an optional solid phase; at high
pressures the foam quality is typically low (i.e., the
non-saturated gas volume is low), but quality (and volume) rises as
the pressure falls; additionally, the aqueous phase may have
originated as a solid material and once the gas phase is dissolved
into the solid phase, the viscosity of solid material is decreased
such that the solid material becomes a liquid; or (c) Liquefied
gases.
[0040] "Viscosity" as used herein unless otherwise indicated refers
to the apparent dynamic viscosity of a fluid at a temperature of
25.degree. C. and shear rate of 170 s.sup.-1. As used herein, when
not used in context relative to a higher viscosity fluid, a "low
viscosity" fluid or phase, e.g., a low viscosity carrier or liquid
phase, refers to one having a viscosity less than 50 mPa-s at a
shear rate of 170 s.sup.-1 and a temperature of 25.degree. C.
[0041] As used herein, "slurry" refers to an optionally flowable
mixture of particles dispersed in a fluid carrier. The terms
"flowable" or "pumpable" or "mixable" are used interchangeably
herein and refer to a fluid or slurry that has either a yield
stress or low-shear (5.11 s.sup.-1) viscosity less than 1000 Pa and
a dynamic apparent viscosity of less than 10 Pa-s (10,000 cP) at a
shear rate 170 s.sup.-1, where yield stress, low-shear viscosity
and dynamic apparent viscosity are measured at a temperature of
25.degree. C. unless another temperature is specified explicitly or
in context of use.
[0042] The term "particulate" or "particle" refers to a solid
3-dimensional object with maximal dimension less than 1 meter, or
less than 0.1 meter or less than 0.01 meter. Here, "dimension" of
the object refers to the distance between two arbitrary parallel
planes, each plane touching the surface of the object at least at
one point.
[0043] In embodiments, the combustible foamed fluid may comprise
multimodal particles. As used herein "multimodal" refers to a
plurality of particle sizes or modes which each has a distinct size
or particle size distribution, e.g., proppant and fines. As used
herein, the terms distinct particle sizes, distinct particle size
distribution, or multi-modes or multimodal, mean that each of the
plurality of particles has a unique volume-averaged particle size
distribution (PSD) mode. That is, statistically, the particle size
distributions of different particles appear as distinct peaks (or
"modes") in a continuous probability distribution function. For
example, a mixture of two particles having normal distribution of
particle sizes with similar variability is considered a bimodal
particle mixture if their respective means differ by more than the
sum of their respective standard deviations, and/or if their
respective means differ by a statistically significant amount. In
an embodiment, the particles contain a bimodal mixture of two
particles; in an embodiment, the particles contain a trimodal
mixture of three particles; in an embodiment, the particles contain
a tetramodal mixture of four particles; in an embodiment, the
particles contain a pentamodal mixture of five particles, and so
on. Representative references disclosing multimodal particle
mixtures include U.S. Pat. No. 5,518,996, U.S. Pat. No. 7,784,541,
U.S. Pat. No. 7,789,146, U.S. Pat. No. 8,008,234, U.S. Pat. No.
8,119,574, U.S. Pat. No. 8,210,249, US 2010/0300688, US
2012/0000641, US 2012/0138296, US 2012/0132421, US 2012/0111563, WO
2012/054456, US 2012/0305245, US 2012/0305254, US 2012/0132421,
PCT/RU2011/000971 and U.S. Ser. No. 13/415,025, each of which are
hereby incorporated herein by reference.
[0044] "Proppant" refers to particulates that are used in well
work-overs and treatments, such as hydraulic fracturing operations,
to hold fractures open following the treatment. In some
embodiments, the proppant may be of a particle size mode or modes
in the slurry having a weight average mean particle size greater
than or equal to about 100 microns, e.g., 140 mesh particles
correspond to a size of 105 microns. In further embodiments, the
proppant may comprise particles or aggregates made from particles
with size from 0.001 to 1 mm. All individual values from 0.001 to 1
mm are disclosed and included herein. For example, the solid
particulate size may be from a lower limit of 0.001, 0.01, 0.1 or
0.9 mm to an upper limit of 0.009, 0.07, 0.5 or 1 mm. Here particle
size is defined is the largest dimension of the grain of said
particle.
[0045] "Gravel" refers to particles used in gravel packing, and the
term is synonymous with proppant as used herein. "Sub-proppant" or
"subproppant" refers to particles or particle size or mode
(including colloidal and submicron particles) having a smaller size
than the proppant mode(s); references to "proppant" exclude
subproppant particles and vice versa. In an embodiment, the
sub-proppant mode or modes each have a weight average mean particle
size less than or equal to about one-half of the weight average
mean particle size of a smallest one of the proppant modes, e.g., a
suspensive/stabilizing mode.
[0046] As used herein, proppant loading is specified in weight of
proppant added per volume of treatment stream to which it is added,
e.g., kg/L (ppa=pounds of proppant added per gallon of carrier
fluid). Other materials in the treatment fluid are generally
expressed in terms of g/L based on the total volume of the
treatment fluid in which they are present (ppt=pounds of material
per thousand gallons of treatment fluid).
[0047] The term "fiber" refers to elongated particles having an
aspect ratio (ratio of length longest dimension to diameter or
shortest dimension) of at least 10. The term "carrier fibers"
refers to fibers which are suitable at an appropriate loading for
assisting in the transport of proppant into a fracture, e.g.,
either during initiation, propagation or branching of the fracture.
The term "non-bridging fibers" refers to fibers which are suitable
for use in a carrier fluid at specified conditions and loadings
generally without forming a bridge in the flow path of interest.
"Bridging fibers" refers to fibers that do not have the
non-bridging quality and/or non-bridging fibers used at
bridge-inducing loading rates. Carrier fibers may be bridging or
non-bridging.
[0048] In the present disclosure, the terms "low temperature
fibers", "mid temperature fibers" and "high temperature fibers" may
be used to indicate the temperatures at which the fibers may be
used for delayed degradation, e.g., by hydrolysis, at downhole
conditions. Low temperatures are typically within the range of from
about 21.degree. C. (70.degree. F.) to about 79.degree. C.
(175.degree. F.); mid temperatures typically from about 80.degree.
C. (176.degree. F.) to about 149.degree. C. (300.degree. F.); and
high temperatures typically about 150.degree. C. (302.degree. F.)
and above, or from about 150.degree. C. (302.degree. F.) to about
232.degree. C. (450.degree. F.).
[0049] As used herein, an agglomerant is any material, such as
fibers, flocs, flakes, discs, rods, stars, etc., for example, which
may be heterogeneously distributed in the fracture and have a
different movement rate, and/or cause some of the first solid
particulate to have a different movement rate, which may be faster
or preferably slower with respect to the settling of the first
solid particulate and/or clusters. As used herein, an agglomerant
may also be or include an "anchorant," referring to a material, a
precursor material, or a mechanism, that inhibits movement such as
settling, or preferably stops movement, of particulates or clusters
of particulates in a fracture, whereas an "anchor" refers to an
anchorant that is active or activated to inhibit or stop the
movement. As used herein, the term "flocs" includes both
flocculated colloids and colloids capable of forming flocs in the
treatment slurry stage.
[0050] Some embodiments of this disclosure relate to systems and
methods to treat a well and/or downhole structure with a foamed
fluid comprising a combustible gaseous phase, e.g., for hydraulic
fracturing, matrix treatments, wellbore cleanout operations, and
the like. Combustion of the fluid as a process feature in some
embodiments generally results in an energy release from the
exothermic combustion process and a transient temperature, pressure
and/or volume increase of the fluid, generally followed by a return
to ambient downhole temperature and pressure conditions.
[0051] In some specific embodiments, especially where the
combustion products may include condensable components such as
water and/or a post-combustion gaseous phase of lower volume, an
ultimate reduction of the overall fluid volume relative to the
combustible foamed fluid just prior to combustion. For example,
oxygen, hydrogen and light hydrocarbons such as methane, ethane or
the like may occur in the gaseous phase of the combustible foamed
fluid, but upon combustion, there may be fewer gaseous products on
a molar or volumetric basis, and also, some common combustion
products such as water may condense largely to liquid phase at the
ambient downhole pressure and temperature, while carbon dioxide may
dissolve in and/or be miscible with other downhole liquids. For
example, a gaseous mixture of stoichiometric oxygen and hydrogen
(1:2 molar ratio) may form almost entirely into water condensate,
which has a negligible volume relative to the gaseous reactants.
Further, transient pressure or temperature increases during the
combustion may lead to the escape of some gaseous phase, e.g.,
through the wellbore, or into adjacent porous formation matrix or
other porous material, or into fractures created by the combustion,
or the like, and the escaped fluid may not, or not fully return
post-combustion to the situs of the original combustible foamed
fluid.
[0052] In some embodiments, the combustion of the combustible fluid
in a downhole structure such as a wellbore, annulus, formation
fracture, formation matrix, or the like, may enhance the
effectiveness of one or more treatment attributes, such as, for
example, more desirable proppant placement (e.g., well-defined
pillars and channels), reduced formation damage, reduced flowback
volume, shortening of the unproductive period of time for the
treatment and/or more rapid initiation or return of the production
of reservoir fluids following treatment, and the like.
[0053] In various embodiments, the properties of the combustible
foamed fluid, including the combustion parameters such as dynamics
and kinetics, are in various embodiments controlled by foam
quality, size and size distribution of the dispersed fluid phase
droplets, fluid chemistry, composition of the gaseous and/or liquid
phases, and the like.
[0054] In specific embodiments of the present disclosure, the
combustible foamed fluid is used for performing matrix treatments,
e.g., below fracturing pressure of the subterranean formation
and/or in conjunction with fracturing. Examples of such treatments
include matrix acidizing, injection of chelating agents into the
matrix, injection of paraffin into the matrix, injection of scale
inhibitors into the matrix, etc. In matrix treatment embodiments,
at or near the conclusion of the treatment process, all of a
significant portion of the combustible foamed fluid may remain in
various openings inside the treated formation, with the size and
configuration of the openings defined by the type of the treatment
as well as the formation geology: acid etched fractures, hydraulic
fractures, wormholes, open natural fractures, caverns, vugs,
interstices, etc. When the combustible foamed fluid is ignited and
combustion otherwise occurs in accordance with embodiments of the
present disclosure, the combustion of the fluid in such openings
may result in increasing effectiveness of the performed treatment,
such as, for example, by reducing the flowback volume, and/or by at
least partially fracturing the formation, e.g., due to an initial
pressure increase during the combustion process that can locally
exceed the fracture pressure as well as an initial temperature
increase that can locally reduce the fracture pressure of the
formation, or the like.
[0055] The following discussion is directed in the main to
hydraulic fracturing embodiments, by way of illustration and
example, and is not intended to thereby limit the scope of the
disclosure or claims, it being understood that the systems and
methods described herein as well as the principles thereof may be
equally applicable, with or without appropriate modification, to
other downhole treatments and structures such as matrix treatments,
wellbore treatments, etc. In hydraulic fracturing, the combustible
foamed fluid may be employed in the initiation, propagation or
other creation of a fracture, such as, for example, in one, or a
combination, or all, of a pad or pre-pad stage, a proppant stage, a
non-proppant stage, spacer stage, tail-in stage, flush stage, or
the like.
[0056] The combustible foamed fluid in various embodiments may
comprise a liquid phase or phases, a gaseous phase or phases, fuel
source(s), combustion oxidant source(s), inert(s) such as nitrogen,
argon, and the like, combustion modifier(s), including inhibitors,
retardants, accelerants, and/or initiators, foaming agent(s),
gelling agent(s), proppant(s), fluid loss additive(s),
sub-proppant(s), fiber(s), polymer(s), crosslinker(s),
surfactant(s), breaker(s), biocide(s), friction reducer(s),
corrosion inhibitor(s), temperature stabilizer(s), clay
stabilizer(s), chelant(s), scale inhibitor(s), diverting agent(s),
proppant or other solid flowback control additive(s),
agglomerant(s), and the like, including multifunctional components
that perform two or more of these functions. For example, nitrogen
gas is an inert gas which can inhibit flame propagation as well as
reduce any transient temperature increase following combustion due
to a lower heating value of the gaseous phase of the fluid. Lower
foam quality, i.e., a higher volumetric proportion of water or
other non-flammable liquid, can likewise be used in some
embodiments to inhibit flame propagation and reduce the transient
temperature and/or pressure increases due to a lower heating value
and the latent heat for volatilization of the liquid component of
the foam.
[0057] The liquid phase of the combustible foamed fluid may be
aqueous in some embodiments, or can be non-aqueous, or a mixture,
such as an oil/water emulsion or invert emulsion. The presence of
fuel materials such as hydrocarbons and/or oxidant materials such
as peroxides can also accelerate the combustion process and/or
increase the resulting transient pressures and temperatures,
whereas the presence of non-flammable components such as brine can
serve to inhibit the combustion process. In some embodiments, the
carrier fluid comprises brine, e.g., sodium chloride, potassium
bromide, ammonium chloride, potassium choride, tetramethyl ammonium
chloride and the like, including combinations thereof. In some
embodiments the diluted stream may comprise oil, including
synthetic oils, e.g., in an oil based or invert emulsion fluid.
[0058] The combustible foamed fluid may be mixed at the surface
before or during pumping downhole, or one or more components may be
delivered downhole separately, e.g., in separate flow paths or
containers, and mixed downhole, e.g., in the wellbore or in or
adjacent the formation, or one or more components may be generated
or formed downhole, e.g., by electrolysis, chemical reaction, or
the like. For example, the gaseous fuel source may be separated
from the combustion oxidant source by using separate lines, tubing,
coiled tubing, including concentrical coil-tubing (e.i. containing
one or more tubing inside the coil tubing itself), or the like, and
a downhole mixer to combine or mix the separate streams together
prior to introduction into the formation. In some embodiments,
mixing or other formation of the combustible mixture is caused to
occur below (relative to the surface) a flow direction check valve,
flame arrester or the like to inhibit combustion through the
wellbore to the surface, or combustion of the combustible foamed
fluid or components at or adjacent the surface can be inhibited by
locating a flame arresting device in the wellbore, e.g., above the
ignition source. In some embodiments, the wellhead and/or surface
equipment are designed to withstand any pressure and/or temperature
increases that might result from combustion of the combustible
foamed fluid, whether the combustion is planned or occurs
inadvertently, e.g., after shut in of the well and/or during
pumping, e.g., after shut in of the well and/or during pumping of
the combustible foamed fluid.
[0059] Electrolysis of water or another aqueous liquid in some
embodiments can be used to generate a mixture of hydrogen and
oxygen gases according to the reaction:
2H.sub.2O.fwdarw.2H.sub.2+O.sub.2. Electrolysis can be performed at
the surface or downhole in an electrolytic cell by passing an
electrical current between electrodes in contact with the aqueous
liquid. In some embodiments, either direct current (DC) or
alternating current (AC) can be used, including a variable voltage
such as a frequency modulated voltage, e.g., in the frequency range
of from 1 Hz to 1 MHz. The mixture of hydrogen and oxygen in the
gaseous phase of the foamed fluid can be stoichiometric or
approximately stoichiometric (due to different solubilities or
reactivities etc.) in the foamed fluid media, and in some
embodiments may be the only gases introduced into the foamed fluid,
or can be used with other gaseous materials.
[0060] In some embodiments, the combustible foamed fluid is placed
in the fracture or other downhole structure under non-combustion
conditions free of an active ignition source, and thereafter
ignited. In contrast to methods employing a downhole burner or
other combustion device in which a steady state or moving flame
front is maintained as in dry combustion, reverse combustion, wet
combustion and like in situ combustion techniques, in some
embodiments, the combustible foamed fluid herein is not ignited
and/or combustion initiated until after the fluid is placed in the
fracture or otherwise used to at least partially complete a
treatment function, e.g., fracture creation, matrix acidization, or
the like. At some point during performance of the fracture
treatment, i.e., during placement into the downhole structure, or
after completion of the fracturing treatment, i.e., after placement
into the downhole structure, a combustion process is initiated in
the gaseous phase of the combustible foamed fluid.
[0061] In some embodiments, ignition of the combustible foamed
fluid is achieved by one or more of surface ignition and
propagation through the wellbore or tubing installed in the
wellbore; downhole ignition with an electrical arc or other igniter
which may be deployed via coiled tubing, wireline or the like;
chemical systems such as Mg/H.sub.2O, Al/NaOH, KMnO.sub.4/glycerol,
or the like, that increase the temperature at a point or region of
the combustible foamed fluid above the ignition point, e.g., by
encapsulating one or more reactants wherein a coating dissolves,
melts or is crushed at downhole conditions such as pressure,
temperature, pH, fracture closure, or the like; the use of
explosive materials that can detonate downhole.
[0062] In some embodiments, the direction of the combustion or
flame front(s) during the combustion process may be selected by the
placement of the ignition source, e.g., at the tip of the fracture
for a "reverse" combustion propagation toward the wellbore, at a
location near the wellbore-fracture junction for "forward"
propagation through the fracture away from the wellbore toward the
tip(s), and/or placement of a plurality of ignition sources at
multiple locations to form a plurality of propagation zones
corresponding to each of the respective ignition sources, which may
or may not have propagation fronts that meet intermediate the
ignition sources. According to some embodiments, proppant may
accumulate to form pillars or ridges at the outer edges of the
respective propagation zones and/or where the propagation fronts
meet between adjacent ones of the ignition sources.
[0063] In some embodiments, combustion of the combustible foamed
fluid in a fracture may result in a reduction of the volume of the
foamed fluid placed in the formation fracture, e.g., a fracture
network, and achieve relatively instantaneous fracture closure,
e.g., especially relative to a shut-in procedure where the
fracturing fluid may need a period of time, first to chemically
break and/or then to generally only gradually permeate into the
formation matrix.
[0064] Rapid fracture closure in some fracturing embodiments can
assist in achieving and/or retaining a desired proppant placement
modality, for example, by reducing the opportunity for proppant to
settle or excessively settle in the formation. In some embodiments,
the proppant is "frozen" in place by rapid fracture closure, e.g.,
trapping the proppant in a relatively homogeneous distribution that
preserves a high porosity and/or conductivity for fluid to flow
through the interstices in the proppant pack, or trapping the
proppant in pillars spaced apart by conductive flow channels
between the proppant pillars or islands.
[0065] In some embodiments, the fracturing method or system
optionally includes isolating the fracture from fluid communication
from the fracture prior to or during combustion of the foamed fluid
in the fracture, e.g., using isolation sleeves, isolation valves,
or diversion plugs. Isolation of the fracture can inhibit fluid
flowback during the combustion process, and inhibit turbulence
and/or fluid flow during combustion that might otherwise result in
movement of the proppant within the fracture from its desired
location.
[0066] In some embodiments, fluid communication between the
wellbore and another downhole structure in which the combustible
fluid has been placed, such as a fracture, is established during
the combustion of the combustible foamed fluid. A transient
pressure increase resulting from the combustion in some embodiments
may create or increase fluid flow into the wellbore from the other
downhole structure to facilitate fluid flowback, facilitate cleanup
(e.g., by entrainment and expulsion of flow damaging materials),
and/or or facilitate proppant placement, e.g. by forming or
assisting in the formation of proppant pillars, or by placing
and/or consolidating proppant in a gravel pack in a screen annulus
and/or in a near wellbore portion of the fracture.
[0067] In some embodiments, a proppant injection stage comprises
alternating proppant-rich and proppant-lean or proppant-free
substages, or otherwise alternating the characteristics between
substages, so as to form a pillar-channel proppant placement
configuration. The present disclosure in some embodiments includes
injecting the combustible foamed fluid, e.g., in or with the
proppant injection stage, wherein the combustion operation
facilitates quickly closing the fracture and preserves the
pillar-channel proppant placement. According to some embodiments,
the proppant stage(s) may be injected into a fracture system using
any one of the available proppant placement techniques, including
heterogeneous proppant placement techniques, wherein the low
viscosity treatment fluid herein is used in place of or in addition
to any proppant-containing treatment fluid, such as, for example,
those disclosed in U.S. Pat. No. 3,850,247; U.S. Pat. No.
5,330,005; U.S. Pat. No. 7,044,220; U.S. Pat. No. 7,275,596; U.S.
Pat. No. 7,281,581; U.S. Pat. No. 7,325,608; U.S. Pat. No.
7,380,601; U.S. Pat. No. 7,581,590; U.S. Pat. No. 7,833,950; U.S.
Pat. No. 8,061,424; U.S. Pat. No. 8,066,068; U.S. Pat. No.
8,167,043; U.S. Pat. No. 8,230,925; U.S. Pat. No. 8,372,787; US
2008/0236832; US 2010/0263870; US 2010/0288495; US 2011/0240293; US
2012/0067581; US 2013/0134088; EP 1556458; WO 2007/086771; SPE
68854: Field Test of a Novel Low Viscosity Fracturing Fluid in the
Lost Hills Fields, California; and SPE 91434: A Mechanical
Methodology of Improved Proppant Transport in Low-Viscosity Fluids:
Application of a Fiber-Assisted Transport Technique in East Texas;
each of which is hereby incorporated herein by reference in its
entirety.
[0068] According to some embodiments herein, the proppant injection
stage comprises alternating the injection of a combustible foamed
fluid substage with another substage comprised of a non-combustible
fluid, which may be a liquid or a foam, e.g., a foam of similar
quality, density, and/or viscosity to inhibit mixing between the
alternating adjacent substages. The proppant or other materials or
components may be otherwise homogeneous or of similar content
between the alternating substages, or they may have different
concentrations of proppant, agglomerant, anchors or the like. Upon
placement and/or combustion of the alternating substages in the
fracture, optionally wherein the substages are segregated within
the fracture, according to some embodiments, the proppant may
accumulate to form pillars selectively within the combustible foam
substages, or within the non-combustible foam substages, or within
both, or at interfaces between the combustible and non-combustible
foam substages. In some embodiments, the combustible foamed fluid
substages may each comprise at least one respective ignition
source. In some embodiments, the combustible foamed fluid substages
are ignited simultaneously, sequentially or in a combination
thereof.
[0069] In some embodiments, as in, for example, US 2014/0262264 by
Potapenko et al. (also published as WO 2014/143490A1), incorporated
herein by reference, a method for treating a subterranean formation
comprises injecting a treatment slurry, which includes a
combustible foamed carrying fluid according to embodiments of the
present disclosure, into a fracture to form a substantially
uniformly distributed mixture of solid particulate and agglomerant;
initiating combustion of the combustible foamed fluid in the
fracture; and transforming the substantially uniform mixture into
areas that are rich in solid particulate and areas that are
substantially free of solid particulate, wherein the solid
particulate and the agglomerant have substantially dissimilar
velocities in the fracture so that the transformation results from
the substantially dissimilar velocities. In some embodiments, the
combustion induces a flow of fluid in the fracture to initiate
transport and/or promote further transport the solid particulate
and the agglomerant at the substantially dissimilar velocities. In
some embodiments, the combustion induces rapid fracture closure to
substantially preserve, i.e., inhibit degrading or blurring of, the
solid particulate-rich and solid particulate-lean areas. In some
embodiments, the combustion induces a flow of fluid in the fracture
to transport or further transport the solid particulate and the
agglomerant at the substantially dissimilar velocities. In some
embodiments, the combustion initially induces a flow of fluid in
the fracture to initiate transport and/or promote further transport
the solid particulate and the agglomerant at the substantially
dissimilar velocities, and subsequently then induces rapid fracture
closure to substantially preserve (or inhibit degrading or blurring
of) the solid particulate-rich and solid particulate-lean
areas.
[0070] According to some embodiments herein, the combustion of the
combustible foamed fluid may create fractures in the subterranean
formation, e.g., initiate new fractures and/or extend existing
fractures. In some embodiments, combustion of the combustible
foamed fluid in the downhole structure may at least temporarily
raise the pressure of the fluid, and in some embodiments the
elevated pressure may exceed a fracture pressure of the adjacent
formation. In some embodiments, extension of fractures may be
coordinated with isolation of the fracture from the wellbore during
combustion of the combustible foamed fluid in the existing or
created fracture. In some embodiments, initiation of new fractures
may be coordinated with isolation of any pre-existing fractures
from a wellbore during combustion of the combustible foamed fluid
in the wellbore, and/or by isolating the combustible foamed fluid
to an interval of the wellbore and igniting the combustible foamed
fluid to create an at least temporary increase in pressure above
the fracturing pressure of the formation.
[0071] In further embodiments according to the present disclosure,
the combustion may at least temporarily increase the temperature of
the post-combustion fluid. In some embodiments, the treatment fluid
may comprise a thermally sensitive viscosity or rheology modifier,
and the temperature increase can effectively break the treatment
fluid, i.e., reduce the viscosity and/or gel strength of the fluid
or a portion thereof. In some embodiments, the combustible foamed
fluid may comprise a thermally sensitive foaming system, e.g.,
foaming agents or stabilizers or liquid surface tension that cease
to support the foam structure at the elevated temperature, and the
temperature increase, alone or together with the changes in foam
quality associated with combustion (at least transient changes
and/or fluctuations in the gas:liquid ratio due to temporary
expansion and ultimate reduction of the gas volume) can effectively
destabilize and/or degrade the foam.
[0072] In some embodiments, the present disclosure can use a
treatment fluid that is thermally stable at the expected downhole
conditions of use, but readily broken, degraded, or destabilized,
at the fluid temperature profile resulting from combustion of the
combustible foamed fluid used as the treatment fluid or as a
sufficient portion of the treatment fluid effective to provide the
fluid temperature. For example, treatment fluids such as fracturing
fluids are designed by taking into consideration the downhole
temperature and the viscosifiers needed to meet the viscosity
requirements during a fracturing treatment at that temperature, and
also by considering the requirements for breaking as well as fluid
destruction requirements in the end of it. Taking into account that
combustion temperature may be relatively higher than that of the
ambient formation, in some embodiments a fracturing fluid may be
used having a composition normally considered as too damaging or
otherwise unsuitable for use due to a low ambient formation
temperature. In a specific embodiment of the present disclosure a
single composition of such fracturing fluid can be used for
treating wells regardless of their temperature range, e.g., a
"universal" fracturing fluid can be used over a wide range of
formation temperatures.
[0073] In some embodiments herein, a combustible foamed fluid may
comprise proppant, or be used or pumped with another stage or
substage comprising proppant in a fracturing operation. The
proppant, when present, can be naturally occurring materials, such
as sand grains. The proppant, when present, can also be man-made or
specially engineered, such as coated (including resin-coated) sand,
modulus of various nuts, high-strength ceramic materials like
sintered bauxite, etc. In some embodiments, the proppant of the
current application, when present, has a density greater than 2.45
g/mL, e.g., 2.5-2.8 g/mL, such as sand, ceramic, sintered bauxite
or resin coated proppant. In some embodiments, the proppant of the
current application, when present, has a density greater than or
equal to 2.8 g/mL, and/or the treatment fluid may comprise an
apparent specific gravity less than 1.5, less than 1.4, less than
1.3, less than 1.2, less than 1.1, or less than 1.05, less than 1,
or less than 0.95, for example. In some embodiments a relatively
large density difference between the proppant and carrier fluid may
enhance proppant settling during the clustering phase, for
example.
[0074] In some embodiments, the proppant of the current
application, when present, has a density less than or equal to 2.45
g/mL, such as light/ultralight proppant from various manufacturers,
e.g., hollow proppant. In some embodiments, the treatment fluid
comprises an apparent specific gravity greater than 1.3, greater
than 1.4, greater than 1.5, greater than 1.6, greater than 1.7,
greater than 1.8, greater than 1.9, greater than 2, greater than
2.1, greater than 2.2, greater than 2.3, greater than 2.4, greater
than 2.5, greater than 2.6, greater than 2.7, greater than 2.8,
greater than 2.9, or greater than 3. In some embodiments where the
proppant may be buoyant, i.e., having a specific gravity less than
that of the carrier fluid, the term "settling" shall also be
inclusive of upward settling or floating.
[0075] In some embodiments herein, a combustible foamed fluid may
optionally further comprise fibers and/or fiber mixtures, proppant
and/or other materials such as particles other than fiber or
proppant, dispersed in the carrier fluid. In embodiments, even in
absence of proppant, the conductivity may be optimized by
alteration of the fracture walls, for example by heat, pressure or
compounds generated from the combustion reaction of the present
energized fluid. In embodiments the intrinsic formation
characteristics may provide sufficient conductivity.
[0076] The liquid phase of the combustible foamed fluid may include
water, fresh water, seawater, connate water or produced water. The
liquid phase may also include hydratable gels (such as guars,
polysaccharides, xanthan, hydroxy-ethyl-cellulose (HEC), guar,
copolymers of polyacrylamide and their derivatives, e.g.,
acrylamido-methyl-propane sulfonate polymer (AMPS), or other
similar gels, or a viscoelastic surfactant system, e.g., a betaine,
or the like), a cross-linked hydratable gel, a viscosified acid
(such as a gel-based viscosified acid), an emulsified acid (such as
an oil outer phase emulsified acid), and an oil-based fluid
including a gelled, foamed, or otherwise viscosified oil. The
liquid phase may be a brine, and/or may include a brine. The liquid
phase may include hydrochloric acid, hydrofluoric acid, ammonium
bifluoride, formic acid, acetic acid, lactic acid, glycolic acid,
maleic acid, tartaric acid, sulfamic acid, malic acid, citric acid,
methyl-sulfamic acid, chloro-acetic acid, an amino-poly-carboxylic
acid, 3-hydroxypropionic acid, a poly-amino-poly-carboxylic acid,
and/or a salt of any acid. In embodiments, the carrier fluid
includes a poly-amino-poly-carboxylic acid, such as a trisodium
hydroxyl-ethyl-ethylene-diamine triacetate, mono-ammonium salts of
hydroxyl-ethyl-ethylene-diamine triacetate, and/or mono-sodium
salts of hydroxyl-ethyl-ethylene-diamine tetra-acetate, or other
similar compositions. When a polymer is present in a low viscosity
liquid phase, for example, in some embodiments it may be present at
a concentration below 1.92 g/L (16 ppt), e.g. from 0.12 g/L (1 ppt)
to 1.8 g/L (15 ppt). When a viscoelastic surfactant is used in a
low viscosity liquid phase, for example, in some embodiments it may
be used at a concentration below 10 ml/L, e.g. 2.5 ml/L to 5
ml/L.
[0077] According to some embodiments of the present disclosure, the
combustible foamed fluid comprises fibers, or may be used with
another treatment fluid or stage or substage comprising fibers.
Different types of fibers may be used optionally at different
loadings to provide different functionalities, which may not
necessarily be mutually exclusive, to a particular treatment fluid
or stream.
[0078] In some embodiments, the treatment fluid comprises from 1.2
to 12 g/L of fibers based on the total volume of the carrier fluid
(from 10 to 100 ppt, pounds per thousand gallons of carrier fluid),
e.g., equal to or less than 4.8 g/L of the fibers based on the
total volume of the carrier fluid (equal to or less than 40 ppt) or
from 1.2 or 2.4 to 4.8 g/L of the fibers based on the total volume
of the carrier fluid (from 10 or 20 to 40 ppt). In some
embodiments, the fibers, which may be proppant-suspending carrier
and/or non-bridging, are crimped staple fibers. In some
embodiments, the crimped fibers comprise from 1 to 10 crimps/cm of
length, a crimp angle from 45 to 160 degrees, an average extended
length of fiber of from 4 to 15 mm, and/or a mean diameter of from
8 to 40 microns, or 8 to 12, or 8 to 10, or a combination thereof.
In some embodiments, the fibers comprise low crimping equal to or
less than 5 crimps/cm of fiber length, e.g., 1-5 crimps/cm.
[0079] In some embodiments, the fibers may have a length of from
about 2 to about 25 mm, such as from about 3 mm to about 20 mm. In
some embodiments, the fibers may have a linear mass density of
about 0.111 dtex to about 22.2 dtex (about 0.1 to about 20 denier),
such as about 0.167 to about 6.67 dtex (about 0.15 to about 6
denier).
[0080] Depending on the temperature that the treatment fluid will
encounter downhole, including transient temperatures associated
with the combustion of the foamed fluid, the carrier, bridging or
non-bridging fibers may be chosen with an emphasis more on their
functionality as carrier, bridging and/or non-bridging fibers based
on their resistance to degradability at the ambient downhole
temperatures and their degradability at the temperature and
duration of the combustion process. For example, since low, mid or
high temperature fibers may be selected solely for their treatment
functionality and resistance to degradation at the formation
temperature, whereas any or all of the low, mid or high temperature
fibers can be degraded at the temperatures associated with the
downhole combustion, e.g., high temperature fibers can be used
regardless of the ambient downhole temperatures, e.g., in low or
mid temperature formations, since such fibers might sufficiently
degrade upon combustion of the foamed fluid. This provides an
example of a universal fluid that can be used in a wide variety of
formations, regardless of the downhole temperature conditions.
[0081] Suitable fibers may optionally degrade under ambient
downhole conditions, which may include temperatures as high as
about 180.degree. C. (about 350.degree. F.) or more and pressures
as high as about 137.9 MPa (about 20,000 psi) or more, in a
duration that is suitable for the selected operation, from a
minimum duration of about 0.5, about 1, about 2 or about 3 hours up
to a maximum of about 24, about 12, about 10, about 8 or about 6
hours, or a range from any minimum duration to any maximum
duration.
[0082] In some embodiments, the fibers comprise polyester. In some
embodiments, the polyester undergoes hydrolysis at a low
temperature of less than about 93.degree. C. as determined by
slowly heating 10 g of the fibers in 1 L deionized water until the
pH of the water is less than 3, and in some embodiments, the
polyester undergoes hydrolysis at a moderate temperature of between
about 93.degree. C. and 149.degree. C. as determined by slowly
heating 10 g of the fibers in 1 L deionized water until the pH of
the water is less than 3, and in some embodiments, the polyester
undergoes hydrolysis at a high temperature greater than 149.degree.
C., e.g., between about 149.5.degree. C. and 204.degree. C. In some
embodiments, the polyester is selected from the group consisting of
polylactic acid (PLA), polyglycolic acid (PGA), copolymers of
lactic and glycolic acid, and combinations thereof.
[0083] In some embodiments, the fibers may be degradable or
non-degradable, and are selected from the group consisting of
polylactic acid (PLA), polyglycolic acid (PGA), polyethylene
terephthalate (PET), polyester, polyamide, polycaprolactam and
polylactone, poly(butylene) succinate, polydioxanone, nylon, glass,
ceramics, carbon (including carbon-based compounds), elements in
metallic form, metal alloys, wool, basalt, acrylic, polyethylene,
polypropylene, novoloid resin, polyphenylene sulfide, polyvinyl
chloride, polyvinylidene chloride, polyurethane, polyvinyl alcohol,
polybenzimidazole, polyhydroquinone-diimidazopyridine,
poly(p-phenylene-2,6-benzobisoxazole), rayon, cotton, cellulose and
other natural fibers, rubber, and combinations thereof.
[0084] In some embodiments, the injection of the treatment fluid
including at least one stage or substage comprising the combustible
foamed fluid forms a homogenous region within the fracture of
continuously uniform distribution of the proppant or other solid
particulate. In some embodiments, the alternation of the
concentration of the agglomerant and/or agglomerant aid forms
heterogeneous areas within the fracture comprising
agglomerant/agglomerant aid-rich areas and agglomerant/agglomerant
aid-lean areas.
[0085] In some embodiments, the agglomerant may comprise a
degradable material. In some embodiments, the agglomerant is
selected from the group consisting of polylactic acid (PLA),
polyglycolic acid (PGA), polyethylene terephthalate (PET),
polyester, polyamide, polycaprolactam and polylactone,
poly(butylene succinate, polydioxanone, glass, ceramics, carbon
(including carbon-based compounds), elements in metallic form,
metal alloys, wool, basalt, acrylic, polyethylene, polypropylene,
novoloid resin, polyphenylene sulfide, polyvinyl chloride,
polyvinylidene chloride, polyurethane, polyvinyl alcohol,
polybenzimidazole, polyhydroquinone-diimidazopyridine,
poly(p-phenylene-2,6-benzobisoxazole), rayon, cotton, or other
natural fibers, rubber, sticky fiber, or a combination thereof. In
some embodiments the agglomerant may comprise acrylic fiber. In
some embodiments the agglomerant may comprise mica.
[0086] In some embodiments, the agglomerant is present in the
agglomerant-laden stages of the treatment fluid in an amount of
less than 5 vol %. All individual values and subranges from less
than 5 vol % are included and disclosed herein. For example, the
amount of agglomerant may be from 0.05 vol % less than 5 vol %, or
less than 1 vol %, or less than 0.5 vol %. The agglomerant may be
present in an amount from 0.5 vol % to 1.5 vol %, or in an amount
from 0.01 vol % to 0.5 vol %, or in an amount from 0.05 vol % to
0.5 vol %.
[0087] In further embodiments, the agglomerant may comprise a fiber
with a length from 1 to 50 mm, or more specifically from 1 to 10
mm, and a diameter of from 1 to 50 microns, or, more specifically
from 1 to 20 microns. All values and subranges from 1 to 50 mm are
included and disclosed herein. For example, the fiber agglomerant
length may be from a lower limit of 1, 3, 5, 7, 9, 19, 29 or 49 mm
to any higher upper limit of 2, 4, 6, 8, 10, 20, 30 or 50 mm. The
fiber agglomerant length may range from 1 to 50 mm, or from 1 to 10
mm, or from 1 to 7 mm, or from 3 to 10 mm, or from 2 to 8 mm. All
values from 1 to 50 microns are included and disclosed herein. For
example, the fiber agglomerant diameter may be from a lower limit
of 1, 4, 8, 12, 16, 20, 30, 40, or 49 microns to an upper limit of
2, 6, 10, 14, 17, 22, 32, 42 or 50 microns. The fiber agglomerant
diameter may range from 1 to 50 microns, or from 10 to 50 microns,
or from 1 to 15 microns, or from 2 to 17 microns.
[0088] In further embodiments, the agglomerant may be fiber
selected from the group consisting of polylactic acid (PLA),
polyester, polycaprolactam, polyamide, polyglycolic acid,
polyterephthalate, cellulose, wool, basalt, glass, rubber, or a
combination thereof.
[0089] In further embodiments, the agglomerant may comprise a fiber
with a length from 0.001 to 1 mm and a diameter of from 50
nanometers (nm) to 10 microns. All individual values from 0.001 to
1 mm are disclosed and included herein. For example, the
agglomerant fiber length may be from a lower limit of 0.001, 0.01,
0.1 or 0.9 mm to any higher upper limit of 0.009, 0.07, 0.5 or 1
mm. All individual values from 50 nanometers to 10 microns are
included and disclosed herein. For example, the fiber agglomerant
diameter may range from a lower limit of 50, 60, 70, 80, 90, 100,
or 500 nanometers to an upper limit of 500 nanometers, 1 micron, or
10 microns.
[0090] In some embodiments, the agglomerant may comprise an
expandable material, such as, for example, swellable elastomers,
temperature expandable particles, Examples of oil swellable
elastomers include butadiene based polymers and copolymers such as
styrene butadiene rubber (SBR), styrene butadiene block copolymers,
styrene isoprene copolymer, acrylate elastomers, neoprene
elastomers, nitrile elastomers, vinyl acetate copolymers and blends
of EV A, and polyurethane elastomers. Examples of water and brine
swellable elastomers include maleic acid grafted styrene butadiene
elastomers and acrylic acid grafted elastomers. Examples of
temperature expandable particles include metals and gas filled
particles that expand more when the particles are heated relative
to silica sand. In some embodiments, the expandable metals can
include a metal oxide of Ca, Mn, Ni, Fe, etc. that reacts with the
water to generate a metal hydroxide which has a lower density than
the metal oxide, i.e., the metal hydroxide occupies more volume
than the metal oxide thereby increasing the volume occupied by the
particle. Further examples of swellable inorganic materials can be
found in U.S. Application Publication Number US 20110098202, which
is hereby incorporated by reference in its entirety. An example for
gas filled material is EXPANCEL.TM. microspheres that are
manufactured by and commercially available from Akzo Nobel of
Chicago, Ill. These microspheres contain a polymer shell with gas
entrapped inside. When these microspheres are heated, e.g., during
the combustion stage and/or due to the ambient formation
temperature, the gas inside the shell expands and increases the
size of the particle. The diameter of the particle can increase 4
times which could result in a volume increase by a factor of
64.
[0091] In some embodiments the agglomerants may be gel bodies such
as balls or blobs made with a viscosifier, such as for example, a
water soluble polymer such as polysaccharide like
hydroxyethylcellulose (HEC) and/or guar, copolymers of
polyacrylamide and their derivatives, and the like, e.g., at a
concentration of 1.2 to 24 g/L (10 to 200 ppt where "ppt" is pounds
per 1000 gallons of fluid), or a viscoelastic surfactant (VES). The
polymer in some embodiments may be crosslinked with a crosslinker
such as metal, e.g., calcium or borate. The gel bodies may further
optionally comprise fibers and/or particulates dispersed in an
internal phase. The gel bodies may be made from the same or
different polymer and/or crosslinker as the continuous crosslinked
polymer phase, but may have a different viscoelastic characteristic
or morphology.
[0092] In some embodiments, when proppant is present as in the
initiation, propagation or other fracture creation operation, the
treatment fluid, e.g., the combustible foamed fluid or another
treatment fluid or stage or substage associated or used in a
treatment job therewith, comprises from 0.01 to 1 kg/L of the
proppant based on the total volume of the carrier fluid in the
treatment stream (from 0.1 to 8.3 ppa, pounds proppant added per
gallon of carrier fluid), e.g., from 0.048 to 0.6 kg/L of the
proppant based on the total volume of the carrier fluid in the
dilute stream (0.4 to 5 ppa), or from 0.12 to 0.48 kg/L of the
proppant based on the total volume of the carrier fluid in the
dilute stream (from 1 to 4 ppa), or from 0.12 to 0.18 kg/L of the
proppant based on the total volume of the carrier fluid in the
dilute stream (from 1 to 1.5 ppa). Exemplary proppants include
ceramic proppant, sand, bauxite, glass beads, crushed nut shells,
polymeric proppant, rod shaped proppant, and mixtures thereof.
[0093] In some embodiments the treatment fluid comprising the
combustible foamed fluid may include a fluid loss control agent,
e.g., fine solids less than 10 microns, or ultrafine solids less
than 1 micron, or 30 nm to 1 micron. According to some embodiments,
the fine solids are fluid loss control agents such as
.gamma.-alumina, colloidal silica, CaCO.sub.3, SiO.sub.2, bentonite
etc.; and may comprise particulates with different shapes such as
glass fibers, flocs, flakes, films; and any combination thereof or
the like. Colloidal silica, for example, may function as an
ultrafine solid loss control agent, depending on the size of the
micropores in the formation, as well as a gellant and/or thickener
in any associated liquid or foam phase.
EXAMPLES
[0094] Any element in the examples may be replaced by any one of
numerous equivalent alternatives, only some of which are disclosed
in the specification. Although only a few example 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 the concepts
described herein. The disclosed subject matter may be embodied in
other forms without departing from the spirit and the essential
attributes thereof, and, accordingly, reference should be made to
the appended claims, rather than to the foregoing specification, as
indicating the scope of the disclosed subject matter. 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.
Example 1
Combustible Fluid Foamed with Stoichiometric Hydrogen/Oxygen
Mix
[0095] An electrolysis cell had graphite and copper electrodes with
surface area of 30 cm.sup.2 spaced 2 cm apart. The cell was loaded
with water and powered by a DC unit with a voltage or potential of
24 volts. Gas formed in the cell comprising an oxygen/hydrogen mix
was transferred to a bottle through a plastic tube and bubbled
through water containing a sodium laurate foaming agent. Bubble
size was controlled to 1-2 mm using a choke at the end of the tube.
The foam generation rate was up to 10 ml/min of a foam quality of
60% at atmospheric pressure and ambient temperature.
Example 2
Combustion of Combustible Foam in a Narrow Slot
[0096] A 30 ml quantity of the combustible foamed fluid of Example
1 was placed in a 1.5 mm wide slot between opposing 10 cm by 20 cm
surfaces of aluminum foil wrapped construction bricks. The slot was
sealed and the foam was ignited at a side of the slot using a spark
igniter. Rapid combustion of the fluid resulted in complete
disappearance of the fluid, which was confirmed by opening and
visually inspecting the slot after the experiment.
Example 3
Reduction of Foam Volumes
[0097] The potential reduction of the volume of the gas phase of
foams from the complete combustion of stoichiometric fuel/oxygen
ratios was estimated for some gas fuel sources. The estimations
assumed the same before and after pressures and temperatures, that
the volume of liquid water produced as a combustion product was
negligible compared to the initial gas phase volume in the foam,
that the carbon dioxide produced as a combustion product was in gas
form and/or at least partially soluble in any liquid present, and
that all gases in the fluid before and after combustion followed
the ideal gas law (PV=nRT). The estimated results are presented in
the following Table:
TABLE-US-00001 TABLE Combustion Reaction Gas phase volume reduction
(%) 2H.sub.2 + O.sub.2 .fwdarw. 2H.sub.2O >99 CH.sub.4 +
2O.sub.2 .fwdarw. CO.sub.2 + 2H.sub.2O >67 2C.sub.2H.sub.6 +
7O.sub.2 .fwdarw. 4CO.sub.2 + 6H.sub.2O >56 C.sub.2H.sub.4 +
3O.sub.2 .fwdarw. 2CO.sub.2 + 2H.sub.2O >50 2C.sub.2H.sub.2 +
5O.sub.2 .fwdarw. 4CO.sub.2 + 2H.sub.2O >43
[0098] Although the preceding description has been described herein
with reference to particular means, materials and embodiments, it
is not intended to be limited to the particulars disclosed herein;
rather, it extends to all functionally equivalent structures,
methods and uses, such are within the scope of the appended
claims.
* * * * *