U.S. patent application number 13/481453 was filed with the patent office on 2013-05-30 for time-delay fluids for wellbore cleanup.
This patent application is currently assigned to Baker Hughes Incorporated. The applicant listed for this patent is Lirio Quintero. Invention is credited to Lirio Quintero.
Application Number | 20130133886 13/481453 |
Document ID | / |
Family ID | 47357672 |
Filed Date | 2013-05-30 |
United States Patent
Application |
20130133886 |
Kind Code |
A1 |
Quintero; Lirio |
May 30, 2013 |
Time-delay Fluids for Wellbore Cleanup
Abstract
A method for delaying the removal of a majority of an oil-based
mud (OBM) filter cake from a hydrocarbon reservoir wellbore that
utilizes a multiple phase composition is described. The use of the
multiple phase composition allows for a microemulsion, a
miniemulsion, or a nanoemulsion to form in situ downhole at a
controllable time. The method includes pumping the multiple phase
composition comprising an additive into the wellbore. The multiple
phase composition may be broken thereby releasing the additive. The
broken multiple phase composition and the additive may contact the
OBM filter cake particles to form an in situ emulsion selected from
the group consisting of a nanoemulsion, a miniemulsion, a
microemulsion, a multiple emulsion, a water-continuous emulsion and
mixtures thereof. The in situ emulsion may incorporate more of the
external oil from the OBM filter cake in order to more easily
remove the OBM filter cake.
Inventors: |
Quintero; Lirio; (Houston,
TX) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Quintero; Lirio |
Houston |
TX |
US |
|
|
Assignee: |
Baker Hughes Incorporated
Houston
TX
|
Family ID: |
47357672 |
Appl. No.: |
13/481453 |
Filed: |
May 25, 2012 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61498249 |
Jun 17, 2011 |
|
|
|
Current U.S.
Class: |
166/279 |
Current CPC
Class: |
C09K 2208/14 20130101;
E21B 43/16 20130101; C09K 8/52 20130101 |
Class at
Publication: |
166/279 |
International
Class: |
E21B 43/16 20060101
E21B043/16 |
Claims
1. A method for removing a majority of oily material in the
near-wellbore area including oil-based mud (OBM) filter cake from a
hydrocarbon reservoir wellbore comprising: delivering a multiple
phase composition comprising an additive into the wellbore;
breaking the multiple phase composition thereby releasing the
additive; contacting the OBM filter cake particles with the broken
multiple phase composition and the released additive to form an in
situ emulsion downhole, wherein the in situ emulsion is selected
from the group consisting of a nanoemulsion, a miniemulsion, a
microemulsion, a water-continuous emulsion, and mixtures thereof;
and incorporating a majority of the external oil from the OBM
filter cake into the in situ emulsion.
2. The method of claim 1, wherein the multiple phase composition
has at least an internal phase and a second phase; and wherein the
additive is dispersed within the internal phase, the second phase,
and combinations thereof.
3. The method of claim 2, wherein the proportion of the internal
phase in the multiple phase composition ranges from about 1 vol. %
to about 90 vol. %.
4. The method of claim 2, wherein the internal phase comprises
vesicles ranging in size from about 0.01 microns to about 1000
microns.
5. The method of claim 1, wherein the additive is selected from the
group consisting of structural stabilizers, surfactants,
viscosifiers, chelating agents, filtration control additives,
suspending agents, dispersants, wetting agents, solvents,
co-solvents, co-surfactants, acids, and mixtures thereof.
6. The method of claim 5, wherein the surfactant is selected from
the group consisting of non-ionic surfactants, anionic surfactant,
cationic surfactants, amphoteric, zwitterionic surfactants,
extended surfactants, and combinations thereof.
7. The method of claim 5, wherein the proportion of the structural
stabilizer based on the total of the internal phase and the second
phase, prior to injection into the third phase for transport,
ranges from about 0.1 vol. % to about 90 vol. %.
8. The method of claim 1 further comprising drilling a wellbore in
a hydrocarbon reservoir with an OBM prior to delivering the
multiple phase composition into the wellbore.
9. The method of claim 1 further comprising forming an OBM filter
cake over at least part of the wellbore prior to breaking the
multiple phase composition for release of an additive.
10. The method of claim 1 where incorporating a majority of the oil
from the OBM filter cake into the in situ emulsion creates a
characteristic selected from the group consisting of where
formation skin damage to the wellbore is reduced, where subsequent
hydrocarbon recovery is increased, where subsequent water injection
rate into the reservoir is increased, and combinations thereof as
compared with an otherwise identical method absent the in situ
emulsion formed downhole.
11. The method of claim 1, wherein the in situ emulsion comprises a
non-polar liquid selected from the group consisting of synthetic
base and mineral oils, ester fluids, paraffins, isomerized olefins,
and mixtures thereof.
12. The method of claim 1, wherein a chelating agent has been added
to the multiple phase composition according to a procedure selected
from the group consisting of: adding the chelating agent to a phase
of the multiple phase composition; adding the chelating agent
directly to the OBM after the multiple phase composition has been
broken; adding the chelating agent to the broken multiple phase
composition; and a combination thereof; where the chelating agent
improves the incorporating of the external oil from the OBM filter
cake into the in situ emulsion as compared to an identical in situ
emulsion absent the chelating agent.
13. The method of claim 12, wherein the chelating agent comprises
an acid selected from the group of inorganic acids consisting of
hydrochloric acid, sulfuric acid, and organic acids consisting of
acetic acid, formic acid and salts thereof, and mixtures
thereof.
14. The method of claim 12, wherein the chelating agent is a
polyamino carboxylic acid selected from the group consisting of
nitrilotriacetic acid (NTA), ethylenediamine tetraacetic acid
(EDTA), trans-1,2-diaminocyclohexane-N,N,N',N',-tetraacetic acid
monohydrate (CDTA), diethylenetriamine pentaacetic acid (DTPA),
dioxaoctamethylene dinitrilo tetraacetic acid (DOCTA),
hydroxy-ethylethylenediamine triacetic acid (HEDTA),
triethylenetetramine hexaacetic acid (TTNA),
trans-1,2diaminocyclohexane tetraacetic acid (DCTA), and salts
thereof, and mixtures thereof.
15. The method of claim 12, wherein the concentration of the
chelating agent in the multiple phase composition ranges from about
1 to about 30 vol %.
16. The method of claim 1, wherein the multiple phase composition
further comprises a water-soluble filtration control additive
selected from the group consisting of modified starch, polymers,
and mixtures thereof.
17. The method of claim 16, wherein the proportion of the
water-soluble filtration control additive in the multiple phase
composition ranges from about 0.1 lb/bbl to about 10 lb/bbl.
18. The method of claim 1, wherein the filter cake particles are
selected from the group consisting of calcium carbonate, hematite,
ilmenite, manganese tetroxide, manganous oxide, iron carbonate,
magnesium oxide, barium sulfate, and mixtures thereof.
19. A method for removing a majority of an oil-based mud (OBM)
filter cake from a hydrocarbon reservoir wellbore comprising:
breaking a multiple phase composition after delivery of the
multiple phase composition into a wellbore thereby releasing the
additive, wherein the multiple phase composition comprises an
internal phase having at least one component thereby releasing the
at least one internal phase component, wherein the at least one
internal phase component is selected from the group consisting of
structural stabilizers, surfactants, viscosifiers, chelating
agents, filtration control additives, suspending agents,
dispersants, wetting agents, and mixtures thereof; contacting OBM
filter cake particles with the broken multiple phase composition
and the released internal phase component to form an in situ
emulsion downhole, wherein the in situ emulsion is selected from
the group consisting of a nanoemulsion, a miniemulsion, a
microemulsion, and mixtures thereof; and incorporating a majority
of the external oil from the OBM filter cake into the in situ
emulsion.
20. A method for removing a majority of an oil-based mud (OBM)
filter cake from a hydrocarbon reservoir wellbore comprising:
delivering a multiple phase composition comprising an internal
phase having at least one component into the wellbore; breaking the
multiple phase composition thereby releasing the at least one
internal phase component, wherein the at least one internal phase
component is selected from the group consisting of structural
stabilizers, surfactants, viscosifiers, chelating agents,
filtration control additives, suspending agents, dispersants,
wetting agents, and mixtures thereof; contacting OBM filter cake
particles with the broken multiple phase composition and the
released internal phase component to form an in situ emulsion
downhole, wherein the in situ emulsion is selected from the group
consisting of a nanoemulsion, a miniemulsion, a microemulsion, and
mixtures thereof; and incorporating a majority of the external oil
from the OBM filter cake into the in situ emulsion.
Description
CROSS REFERENCE TO RELATED APPLICATION
[0001] This application claims the benefit of U.S. Provisional
Application Ser. No. 61/498,249 filed Jun. 17, 2011, incorporated
by reference herein in its entirety.
TECHNICAL FIELD
[0002] The present invention relates to a method for delaying the
formation of a downhole emulsion selected from the class consisting
of a microemulsion, a miniemulsion, a multiple phase emulsion, a
water-continuous emulsion, a nanoemulsion, and mixtures thereof for
removal of a majority of an oil-based mud filter cake from a
hydrocarbon reservoir wellbore.
BACKGROUND
[0003] Drilling fluids used in the drilling of subterranean oil and
gas wells along with other drilling fluid applications and drilling
procedures are known. In rotary drilling, there are a variety of
functions and characteristics that are expected of drilling fluids,
also known as drilling muds, or simply "muds". The drilling fluid
should carry cuttings from beneath the bit, transport them through
the annulus, and allow their separation at the surface, while the
rotary bit is cooled and cleaned. A drilling mud is also intended
to reduce friction between the drill string and the sides of the
hole, while maintaining the stability of uncased sections of the
borehole.
[0004] The drilling fluid is formulated to prevent unwanted
influxes of formation fluids from permeable rocks penetrated and
also often to form a thin, low permeability filter cake which
temporarily seals pores, other openings and formations penetrated
by the bit. The drilling fluid may also be used to collect and
interpret information available from drill cuttings, cores and
electrical logs. It will be appreciated that as defined herein, the
term "drilling fluid" also encompasses "drill-in fluids" and
"completion fluids".
[0005] Drilling fluids are typically classified according to their
base fluid. In water-based muds, solid particles are suspended in
water or brine. Oil can be emulsified in the water. Nonetheless,
the water is the continuous phase. Oil-based muds are the opposite
or inverse. Solid particles are suspended in oil, and water or
brine is emulsified in the oil and therefore the oil is the
continuous phase. Oil-based muds which are water-in-oil
macroemulsions are also called invert emulsions. The oil in
oil-based (invert emulsion) mud can consist of any oil that may
include diesel, mineral oil, esters, or alpha olefins. Brine-based
drilling fluids, of course are a water-based mud in which the
aqueous component is brine. It is apparent to those selecting or
using a drilling fluid for oil and/or gas exploration that an
essential component of a selected fluid is that it be properly
balanced to achieve the necessary characteristics for the specific
end application.
[0006] Drilling fluids have a number of tasks or functions to
perform simultaneously. One specific function of the drilling fluid
is to form a filter cake to control the filtrate invasion into the
formation. Filter cakes are the residue deposited on a permeable
medium, such as a formation surface when a slurry or suspension,
such as a drilling fluid, is circulated within the wellbore where
the pressure is overbalanced. Filtrate is the liquid that passes
through the medium, leaving the filter cake on the medium. Filter
cake properties, such as cake thickness, toughness, slickness and
permeability are important because the cake that forms on permeable
zones in a wellbore can cause stuck pipe and other drilling
problems. Reduced hydrocarbon production can result from reservoir
or skin damage when a poor filter cake allows deep filtrate
invasion.
[0007] In a conventional drilling operation, the filter cake also
helps maintain control of the well and isolate formations from
drilling fluids. A filter cake may form external to the formation,
as well as a small filter cake formed internal to the formation by
the spurt loss and solids. However, the external filter cake should
be thin but strong enough with low permeability to prevent
formation damage or fluid invasion. The internal filter cake has a
higher potential for formation damage. It will be appreciated that
in the present context the term "filter cake" includes any emulsion
or invert emulsion part of the filter cake, and that the filter
cake is defined as a combination of any added solids, if any, and
drilled solids. It will also be understood that the drilling fluid,
e.g. invert emulsion fluid, is concentrated at the bore hole face
and partially inside the formation. Further, an open hole
completion is understood to be a well completion that has no liner
or casing set across the reservoir formation, thus allowing the
produced fluids to flow directly into the wellbore. A liner or
casing may be present in other intervals, for instance between the
producing interval and the surface.
[0008] Many operators are interested in improving formation clean
up after drilling into reservoirs with invert emulsion drilling
fluids. More efficient filter cake and formation clean up is
desired for a number of open hole completions, including
stand-alone and expandable sand screens as well as for gravel pack
applications for both production and water injection wells. Skin
damage removal from internal and external filter cake deposition
during oil well reservoir drilling with invert emulsion drill-in
and drilling fluids is desirable to maximize hydrocarbon
recovery.
[0009] Further, it is often desirable in the destruction and
removal of invert emulsion filter cake to not do so quickly, but
rather to delay the destruction and removal of the filter cake.
Without control of the destruction rate, massive brine losses may
occur quickly and before the work string can be safely pulled out
of the open wellbore. Post drill-in treatment and alteration of a
majority of filter cake particles can be accomplished by pumping a
multiple phase composition downhole to form an in situ emulsion
where the in situ emulsion may be a nanoemulsion, a miniemulsion, a
microemulsion, a water-continuous emulsion, or mixtures thereof as
will be described in more detail.
[0010] It would be desirable if methods could be devised to aid and
improve the ability to clean up filter cake, and to remove it more
completely, without causing additional formation damage. It is also
desirable to delay the rate of destruction and removal of the
filter cake by delaying the formation of a nanoemulsion, a
miniemulsion, a microemulsions, or mixtures thereof.
SUMMARY
[0011] There is provided, in one form, a method for removing a
majority of oil-based mud (OBM) filter cake from a hydrocarbon
reservoir wellbore. The method may include delivering a multiple
phase composition into the wellbore. The multiple phase composition
may be broken downhole thereby releasing an additive. The broken
multiple phase composition and the released additive may contact
the OBM filter cake to form an in situ emulsion downhole selected
from the group consisting of a nanoemulsion, a miniemulsion, a
microemulsion, a multiple emulsion, a water-continuous emulsion,
and mixtures thereof. The oil from the OBM filter cake may be
incorporated into the in situ emulsion and the filter cake
particles are slurrified for subsequent removal of the filter cake
from the wellbore.
[0012] There is further provided in another non-limiting embodiment
a method for forming an in situ emulsion within a hydrocarbon
reservoir wellbore for removing a majority of oil-based mud (OBM)
filter cake particles from a hydrocarbon reservoir wellbore. The
method may include delivering a multiple phase composition into the
wellbore where the multiple phase composition may have an internal
phase with at least one component. The multiple phase composition
may be broken downhole for release of the at least one internal
phase component. The internal phase component may be selected from
the group consisting of structural stabilizers, surfactants,
co-surfactants, viscosifiers, chelating agents, filtration control
additives, suspending agents, dispersants, wetting agents,
solvents, co-solvents, acids, and mixtures thereof. The broken
multiple phase composition and the released internal phase
component may contact the OBM filter cake particles to form an in
situ emulsion selected from the group consisting of a nanoemulsion,
a miniemulsion, a microemulsion, a water-continuous emulsion, a
multiple emulsion, and mixtures thereof. The oily material of the
filter cake may be incorporated into the in situ emulsion.
[0013] By forming an in situ emulsion downhole, such as a
nanoemulsion, a miniemulsion, a multiple emulsions, a
water-continuous emulsion, or a microemulsion, the in situ emulsion
may absorb more of the non-polar hydrocarbon phase from the filter
cake than if the emulsion were formed at the surface and lowered
into the wellbore. Thus, more filter cake particles may be
removed.
DETAILED DESCRIPTION
[0014] It has been discovered that post drill-in treatment and
alteration of a majority of an OBM filter cake may be accomplished
by delaying the formation of an in situ emulsion selected from the
group consisting of a microemulsion, a miniemulsion, a
nanoemulsion, and mixtures thereof, so that the formation of the in
situ emulsion occurs downhole. The delayed formation of the in situ
emulsion downhole may improve, enhance, or increase the ability of
the time delayed emulsion to incorporate the oil from the OBM
filter cake. The forming of the in situ emulsion may be delayed by
delivering an additive from the multiple phase emulsion necessary
to form the in situ emulsion that incorporates the oil portion of
the OBM filter cake. The multiple phase emulsion should not be
confused with the in situ emulsion. The in situ emulsion forms once
the multiple phase emulsion has been pumped downhole; said
differently, the in situ emulsion cannot form without first
delivering the multiple phase emulsion to the desired location.
[0015] The additive is delivered by pumping a multiple phase
emulsion downhole and subsequently breaking the multiple phase
emulsion and releasing the additive. In a non-limiting embodiment,
the additive is in an internal phase of the multiple phase
emulsion. The additive then helps create the in situ emulsion that
may be a nanoemulsion, a miniemulsion, a multiple emulsion, a
water-continuous emulsion, or a microemulsion. The in situ emulsion
then incorporates encountered oil from the filter cake.
[0016] Multiple emulsions, also called a multiple phase composition
herein, may be defined as an emulsion within an emulsion that is
typically stabilized by an emulsifier or a surfactant. An emulsion
is a mixture of two or more immiscible liquids. In an emulsion, a
dispersed phase is dispersed in a continuous phase. Because the two
or more liquids are immiscible, the dispersed phase liquid forms
droplets within the continuous phase. In a typical multiple
emulsion, the dispersed phase droplets may have smaller dispersed
droplets.
[0017] Multiple phase compositions are anticipated as being useful
to organize a liquid phase to isolate one miscible phase from
another. An oil-based vesicle could be used in an invert emulsion,
hydrocarbon-based or ester-based or other water immiscible,
non-aqueous-based system, while a water-based vesicle could be used
in an aqueous system. In another non-limiting embodiment,
alcohol-based vesicles may be used in hydrocarbon-based or other
water immiscible, non-aqueous-based systems, or in aqueous systems,
depending upon the particulars of the vesicle design.
[0018] In short, the multiple phase compositions may be applied to
any two miscible phases such that one phase (the first phase) can
be partitioned and isolated from the other phase (the third phase)
by the use of a surface active material bilayer membrane (the
second phase). The phases need not be "oil" or "water", although
such phases are likely to be the most common implementation. One
non-limiting example is the combination of a water soluble,
relatively low molecular weight glycol that forms an emulsion with
brine. The vesicles described herein may also be termed
liposomes.
[0019] One important application of this kind of organization would
be the controlled release of the internal phase and/or the internal
phase contents, such as any conventional additive at least within
the innermost (first) phase. A non-limiting example of such an
application would be the inclusion of, for instance, structural
stabilizers, surfactants, co-surfactants, viscosifiers, chelating
agents, filtration control additives, suspending agents,
dispersants, wetting agents, solvents, co-solvents, acids, and
mixtures thereof alone if liquid or in solution, as a first,
internal phase in an aqueous or hydrophilic carrier such as a
water-based drilling fluid (third phase) separated by a surface
active material bilayer membrane (the second phase).
[0020] The surfactants/emulsifiers, viscosifiers, stabilizers, and
mixtures thereof may be added to the surface active material as a
structural stabilizer to increase the mechanical stability and to
aid in delaying release or breaking of the surface active material
bilayer membrane. Any of the surfactants/emulsifiers, viscosifiers,
stabilizers, or mixtures thereof previously mentioned may be used
in the surface active material bilayer membrane, the inner phase of
the multiple phase composition, or both.
[0021] Alternatively, polymerizable surface active materials may be
used to form the bilayer membranes followed by polymerization to
stabilize the vesicles. Polymerization of the tail portion of the
molecule adds stability to the vesicles. Materials suitable to form
the surface active material bilayers include, but are not
necessarily limited to phospholipids, alkyl polyglycosides, gemini
surfactants, sorbitan monooleate, sorbitan trioleate, glycerol
fatty acid esters including mono- and/or dioleates, polyglycerol
fatty acid esters, polyglycols, alkanolamines and alkanolamides
such as ethoxylated amines, ethoxylated amides, ethoxylated
alkanolamides, including non-ethoxylated ethanolamides and
diethanolamides, and the like as well as block copolymers,
terpolymers and the like, and other polymerizable surface active
materials, gelling agents, and the like that can exist as bilayers
in aqueous solutions. The hydrophobic portion, that is, the
hydrocarbon tails, are shielded in the middle of these bilayers.
The hydrophilic portion is exposed on both sides (opposite sides of
the respective bilayers) to water or another aqueous solution.
[0022] While surface active material bilayers are more commonly
seen in aqueous systems, they are also found in non-aqueous systems
where two miscible oil or non-aqueous phases are separated by a
surface active material bilayer in which the molecules are arranged
oppositely from that described above, i.e. where hydrophobic
portions or tails are exposed on both sides of the layer, while the
hydrophilic heads are shielded together in the middle or center of
the bilayer. Forming multiple phase vesicles using surface active
material bilayers may require special but known techniques
involving relatively high shear mixing and long shear times, as
well as relatively high applications of energy.
[0023] In one non-limiting embodiment, when sorbitan monooleate
(SMO) is used to form the surface active material surface active
material bilayers, it is difficult to get the SMO into an aqueous
fluid. Optionally, a carrier may be used to help introduce the
surface active material bilayer compound into the fluid. While SMO
can form a surface active material bilayer by itself, generally
more time and energy are required than when a carrier is used.
Suitable carriers for SMO include, but are not necessarily limited
to ethoxylated alcohols and polyalkyleneglycols. It is expected
that the carrier may be specific to the surface active material
bilayer compound to some extent. The vesicle shape may include, but
is not limited to, spherical, ovoid, elongated, cylindrical,
lamellar, onion layered, worm-like, ribbons, hexagonal rods and
mixtures thereof.
[0024] If appropriate or desirable, the additive may be in aqueous
or hydrocarbon solution. In some non-limiting embodiments, the
additive to be delivered may be in both the first phase and the
second phase, and in identical or different concentrations. Such a
system could provide a two-stage delivery of the additive. The
first or internal phase may be soluble in the external or
continuous phase (the third phase). Thus, if the continuous phase
(third phase) is an aqueous fluid, the first, internal phase should
be aqueous; if the continuous phase (third phase) is non-aqueous or
hydrophobic, the first, internal phase should be non-aqueous or
hydrophobic.
[0025] Vesicles have several advantages over multiple emulsions.
The lack of appreciable amounts of an immiscible intermediate
(second) carrier phase of different density helps prevent gravity
separation of the final multiphase system. Leaving out the second
phase carrier fluid maximizes the viscosity/consistency of the
surface active material bilayer membrane and helps stabilize the
membrane. Leaving out the second phase carrier fluid also minimizes
the amount of "inert" material in a product, which can add to the
storage and shipping costs of that product undesirably. Indeed, an
important advantage of vesicles in many embodiments is the
increased stability of the product and/or liquid they exist in.
[0026] The speed of stirring or mixing of the two phases would
depend upon the desired size of the vesicles, and the particular
system used. It is expected that the size of the first phase
vesicles would range from about 0.01 to about 1000 microns or less,
in another non-limiting embodiment, from about 1 to about 100
microns or less, as non-limiting examples. In one non-limiting
embodiment, the vesicles would be as large as is practical.
[0027] The proportion of the first, internal phase to the overall
multiple phase composition may range from about 1 vol %
independently to about 90 vol % independently, 40 vol %
independently to about 60 vol %, or in another non-limiting
embodiment about 50 vol % or less, as non-limiting examples. A
lower threshold of 1 vol % may be appropriate in some embodiments.
The multiple phase vesicles may be suspended in the drilling and/or
completion fluid (the third phase). If the third phase is
non-aqueous, in one non-restrictive embodiment, the phase may, in
some non-limiting embodiments, be a synthetic material, and, for
instance, may include, but is not necessarily limited to, esters,
iso-olefins, alpha-olefins, polyolefins, poly(alpha-olefins),
paraffins, Fischer-Tropsch reaction products, and the like. The
non-aqueous phase may be a mixture or blend of petroleum
distillates and synthetic hydrocarbons. Suitable petroleum
distillates include, but are not limited to, diesel oil, kerosene,
mineral oils, food grade mineral oils, paraffinic oils,
cycloparaffinic oils, aromatic oils, or n-paraffins, isoparaffins
and similar hydrocarbons.
[0028] Crude oil could be used in some cases. In the case where the
third phase is an oil-based phase, it is anticipated that any of
these hydrocarbons may be used. In the case where first and third
miscible phases are aqueous, the aqueous phases may be brine. It is
expected that brine will be a common component of the multiple
phase composition, and any of the commonly used brines, and salts
to make them, are expected to be suitable in the methods herein.
Careful adjustment of the internal phase salinity may be required
(osmotic pressure gradient adjustment). Too much salt in a first
aqueous phase may make the vesicles unstable. However, this
mechanism may be intentionally used to cause failure or rupture of
the vesicles or liposomes downhole. For example, the droplets could
be designed to grow on the journey downhole and break at or near
the desired zone.
[0029] Dilution is prevented, suppressed, or delayed until the
surface active material bilayer membrane is intentionally broken. A
likely area for breakage of the multiple phase composition is the
high shear environment of and below the drilling bit, where the
additive is released to the borehole and cuttings in concentrated
form on a localized basis. It may be noted that the high shear
conditions used in making the compositions are at surface pressures
and temperatures, and that downhole temperatures and pressures will
be higher. Further, it is expected that in some high shear
applications, vesicles may be created at the same time others are
broken to maintain a pseudo-steady state, or in some cases an
increase in vesicle content. It will also be understood in the
context described herein that the internal phase or first phase may
be the same as or co-extensive with the agent or the product being
delivered. Of course, emulsifiers, viscosifiers, or other
structural stabilizers may also be added to increase the mechanical
stability of the vesicles in some cases to delay release of the
contents (additive).
[0030] In one embodiment, the vesicles may be as large as possible.
The larger the first phase vesicles in the second phase, all things
being equal, the easier it would be to break the surface active
material bilayers to release the agents and/or internal phase
contents from the first phase. The proportions of the vesicles in
the second phase as a product completion fluid (additional second
phase) may range from about 0.5 vol % independently to about 90 vol
%. Alternatively the lower limit of this range may be about 1 vol %
independently or about 2 vol %, while the upper limit of this range
may be about 40 vol %, in one non-limiting embodiment about 10 vol
%, in another embodiment up to about 5 vol %, and in still another
non-restrictive embodiment up to about 6 vol %, as non-limiting
examples, to make the overall multiple phase composition.
[0031] The method described may find particular usefulness in
increasing the local concentration of an additive downhole after
rupture of the surface active material bilayers, while keeping the
overall concentration of the agent in the drilling mud (including
the entire multiple phase composition) low. For example, polymers
or copolymers, such as styrene-butadiene rubber (SBR) in one
non-limiting embodiment, may be useful as viscosifiers and/or
filtration control additives, could be the additive in the first
phase and be in relatively low concentrations overall. However,
once the surface active material bilayers of the vesicles are
broken or caused to fail, the local concentration of SBR at the
vesicle failure zone would be relatively increased.
[0032] However, the multiple phase composition is designed to be
broken in one non-limiting embodiment. That is, the internal phase
or first phase which contains an additive or where the internal
phase is the additive itself is released or delivered from within
the surface active material bilayer. Indeed, the vesicles are
desirably and controllably broken within a certain area of the
wellbore at designated and relatively controlled time. The
preparation of the vesicles would typically involve the mixing of
the first phase with the second phase, in the presence of the
surface active material bilayer material, where any emulsifier or
structural stabilizer might also be present. Alternatively, one
liquid may be used which contains the surface active material
bilayer compound, with or without a structural stabilizer.
[0033] Using the multiple phase composition is straightforward and
requires no special equipment. The vesicles are injected into a
fluid that is pumped downhole. The fluid may be a drilling fluid,
drill-in fluid, a completion fluid or the like. In one
non-restrictive embodiment, the fluid is a drilling fluid or
drill-in fluid. A number of mechanisms could be used to break the
multiple phase composition at a particular time, including, but not
necessarily limited to, a change in energy input, e.g. a change in
temperature, a change in pressure, an increase in shear stress, an
increase in shear rate, mechanical action (e.g. a rotating drill
bit or drill string), a change in pH, a change in electrical
potential, a change in magnetic flux, solvent thinning, presence of
a chemical agent, presence of a catalyst, and the like, and
combinations thereof.
[0034] A non-limiting, but useful method is breaking the multiple
phase composition by subjecting it to a high shear environment, in
particular the fluid stream exiting a nozzle impinging on the
borehole such as below a bit or opposite a reamer or hole opener.
In one non-limiting embodiment, the surface active material
bilayers are broken within a required period of time, and within a
required physical volume. In another non-limiting embodiment, if
the additive being delivered could be delivered essentially
instantaneously to the borehole and cuttings in a concentrated form
on a localized basis. It would also be understood that more than
one additive may be delivered downhole, and that two or more
additives may interact or react with each other to provide a
beneficial effect. For example, cross-linkers could be transported
in a first vesicle product in the same aqueous third phase as
second vesicle product containing the agent to be crosslinked.
[0035] It may be necessary or desirable to add
surfactants/emulsifiers, viscosifiers, stabilizers, and mixtures
thereof as structural stabilizers to increase the mechanical
stability of the internal phase. Emulsifiers should be understood
to include, but are not limited to, surfactants and the like, and
viscosifiers should be understood to include, but are not limited
to, gelling agents and the like. The emulsifiers and viscosifiers
may be in liquid or solid (e.g. powder) form. Suitable emulsifiers
may include, but are not necessarily limited to, nonionic, anionic,
cationic, amphoteric, zwitterionic, and extended surfactants and in
particular, blends thereof. Co-solvents or co-surfactants such as
alcohols are optional additives within the multiple phase
composition that may aid in filter cake removal once the in situ
emulsion has formed downhole.
[0036] In another non-restrictive embodiment, the additive may be a
co-surfactant which is an alcohol having from about 3 to about 10
carbon atoms, in another non-limiting embodiment from about 4 to
about 6 carbon atoms. A specific example of a suitable
co-surfactant includes, but is not necessarily limited to butanol.
In one non-limiting embodiment, the multiple phase composition
contains non-polar liquid, which may include a synthetic fluid
including, but are not necessarily limited to, ester fluids;
paraffins (such as PARA-TEQ.TM. fluids from Baker Hughes Drilling
Fluids) and isomerized olefins (such as ISO-TEQ.TM. from Baker
Hughes Drilling Fluids). However, mineral oils such as Escaid 110
(from Exxon) or ECD 99-DW oils (from TOTAL) can also be used as a
non-polar liquid in preparing the fluid systems herein. It will be
appreciated that the amount of emulsion-forming components to be
used is difficult to determine and predict with much accuracy since
it is dependent upon a number of interrelated factors including,
but not necessarily limited to, the brine type, the bridging
particle type, the temperature of the formation, the particular
surfactant or surfactant blend used, whether a chelating agent is
present and what type, etc. Nevertheless, in order to give some
idea of the quantities used, in one non-limiting embodiment, the
proportion of non-brine components in the multiple phase
composition may range from about 1 vol % independently to about 50
vol %, from about 5 vol % independently to about 20 vol %, and in
another non-limiting embodiment may range from about 5 vol % to
about 20 vol %.
[0037] Suitable nonionic surfactants include, but are not
necessarily limited to, alkyl polyglycosides, sorbitan esters,
methyl glucoside esters, amine ethoxylates, diamines ethoxylates,
polyglycerol esters, alkyl ethoxylates, polypropoxylated and/or
ethoxylated alcohols, sorbitan fatty acid esters including
phospholipids, alkyl polyglycosides, gemini surfactants, sorbitan
monooleate, sorbitan trioleate, glycerol fatty acid esters
including mono- and/or dioleates, polyglycols, alkanolamines and
alkanolamides such as ethoxylated amines, ethoxylated amides,
ethoxylated alkanolamides, including non-ethoxylated ethanolamides
and diethanolamides, and the like as well as block copolymers,
terpolymers and the like. Suitable cationic surfactants include,
but are not necessarily limited to, arginine methyl esters,
alkanolamines and alkylenediamides. In one non-limiting embodiment
the suitable anionic surfactants include alkali metal alkyl
sulfates, alkyl ether sulfonates, alkyl sulfonate, branched ether
sulfonates, alkyl disulfonate, alkyl disulfate, alkyl
sulfosuccinate, alkyl ether sulfate, branched ether sulfates.
[0038] Amphoteric or zwitterionic surfactants include, but are not
necessarily limited to alkyl betaines and sulfobetaines. Others
surfactants, such as extended surfactants may include, but are not
necessarily limited to surfactants having a non-ionic spacer-arm
between the polar head and the lipophilic tail. The non-ionic
spacer-arm central extension may result from a process that may
include, but is not necessarily limited to polypropoxylation,
polyethoxylation, or combinations thereof. Viscosifiers and gelling
agents may include, but are not necessarily limited to, polymers of
ethylene, propylene, butylenes, butadiene, styrene, vinyltoluene,
and various copolymers and terpolymers thereof, organophilic clays,
aluminum soaps and alkoxides and other aluminum salts, alkaline
earth soaps, lithium soaps, fumed silica and alumina and the like
and mixtures thereof.
[0039] Other suitable stabilizers may include, but are not
necessarily limited to, cholesterol and long chain oil soluble waxy
alcohols, and the like. These structural stabilizers may be added
directly to the second phase prior to the addition of the first
phase, directly to the first and second phase emulsion, or they may
be added to the fully formed multiple phase vesicle system, if that
is more convenient. In one non-limiting embodiment, the proportion
of structural stabilizer based on the total of the first and second
phases, prior to injection into the third phase for transport, may
range from about 0.1 vol % independently to about 90 vol. %, in
another non-limiting embodiment from about 1 to about 50 vol. %. As
used herein with respect to a range, "independently" means that any
lower threshold may be used together with any upper threshold to
give a suitable alternative range.
[0040] The internal phase may optionally include a chelating agent.
The chelating agent improves the incorporation of the external oil
in the filter cake particles into the in situ emulsion as compared
to an identical in situ emulsion formed absent the chelating agent.
The use of the multiple phase composition in open hole completion
optionally allows for the direct contact of a chelating agent once
the multiple phase composition has broken and the chelating agent
has been released. The chelating agent may be an acid and/or an
acid blend mixed in conventional brine completion fluids, without
causing a high viscosity oil continuous emulsion (sludge) and
formation blockage. The action of the in situ emulsion formed
alters the deposited filter cake, which allows the chelating agent
such as an acid or a salt of an acid, such as a polyamino
carboxylic acid (PACA) and/or a mineral acid or salt thereof, e.g.
hydrochloric acid or an organic acid or salt thereof, e.g. acetic
acid, or other acid, to solubilize the bridging and formation
particles, such as calcium carbonate, hematite, ilmenite, and
barite. Bridging particles composed of manganese tetroxide (in one
non-limiting embodiment) may be treated with the multiple phase
composition, providing the acid is an organic acid in one
non-limiting embodiment. It has been found that PACAs perform
relatively better in an alkaline environment as the salt of these
acids, which further differentiates them from the more common
acidic acids and salts thereof.
[0041] For instance a salt of PACA dissociates barium sulfate from
the calcium carbonate treated; the PACA takes on the cation. In a
non-limiting example, a Na or K salt of PACA when contacting
calcium carbonate contacts and dissolves the barium salt through
cationic exchange. The salt form of PACAs performs relatively
better than the plain acid form, but the non-salt acid form still
performs the functions and achieves the desired results of the
methods herein. The plain acid form works somewhat better at
relatively low pH.
[0042] In the non-limiting embodiment where the multiple phase
composition contains at least one chelating agent, the chelating
agent should be capable of solubilizing or dissolving the bridging
particles that make up the filter cake. The chelating agent may be
an inorganic acid or salt thereof including, but not necessarily
limited to, hydrochloric acid, sulfuric acid, and/or an organic
acids including, but not necessarily limited to, an organic agent
or salt thereof, e.g. acetic acid, formic acid and mixtures
thereof. In one non-limiting embodiment, the acid may be only one
mineral acid or only one organic acid.
[0043] In most embodiments, the multiple phase composition may
contain a chelating agent that is a polyamino carboxylic acid
(PACA) or a salt of PACA. Suitable PACAs include, but are not
necessarily limited to, nitrilotriacetic acid (NTA),
ethylenediamine tetraacetic acid (EDTA),
trans-l,2-diaminocyclohexane-N,N,N',N',-tetraacetic acid
monohydrate (CDTA), diethylenetriamine pentaacetic acid (DTPA),
dioxaoctamethylene dinitrilo tetraacetic acid (DOCTA),
hydroxyethylethylenediamine triacetic acid (HEDTA),
triethylenetet-ramine hexaacetic acid (TTNA),
trans-l,2-diaminocyclohexane tetraacetic acid (DCTA), and mixtures
thereof.
[0044] The net effect of such a treatment system will improve an
operator's chance of injecting water in a reservoir to maintain
reservoir pressure (for example, for injection wells), and improve
production rates in producing wells. In either case, skin (filter
cake) alteration is accomplished by circulating and placing the
broken multiple phase composition and additive across the injection
production interval. The multiple phase composition may be used for
open hole expandable and non-expandable screen applications or
other various open hole operations.
[0045] The concentration of chelating agent in the multiple phase
composition has a lower limit of about 1 vol % independently,
alternatively of about 5 vol %, and an upper limit of about 30 vol
%, alternatively about 20 vol %, and in another non-restrictive
embodiment up to about 15 vol %. There are various ways by which
the chelating agent may be delivered. The chelating agent may be an
additive within the multiple phase composition and released onto
the filter cake once the multiple phase composition is broken; or
may be added after the broken multiple phase composition has
contacted the filter cake; or may be added to the broken multiple
phase composition once it is in place before removing the majority
of the OBM filter cake, or invert emulsion, and combinations
thereof.
[0046] With the optional employment of a filtration control
additive, also called an additive for delay herein, the skin
removal rate may be controlled for operational flexibility. In
brief, one non-limiting embodiment OBM or invert emulsion filter
cake clean up technology utilizes the in situ emulsion formed and
optional chelating agent techniques and optional filtration control
additives in a single blend to change the OBM or invert emulsion
filter cake to a microemulsion and simultaneously decompose its
acid soluble components. Altering the filter cake using the in situ
emulsion facilitates solubilization of solids by preventing a
sludge that could form between the chelating agent and OBM or
invert emulsion cake and making soluble particles unavailable to
unspent chelating agent.
[0047] In one non-limiting embodiment, the methods herein utilize a
filtration control additive (fluid loss control additive), such as
a polymer and/or solid particulates such as sized salts, to convert
an OBM cake to a water-based filter cake. The benefits of such
conversions are several. When an OBM filter cake is oil wet and
poses compatibility problems for certain completion operations,
such as water injection and gravel packing, a water-based filter
cake is naturally compatible with injection water and brine-based
gravel pack carrier fluids. Additionally, a water-based filter cake
is ideal for damage remediation (filter cake destruction) when
mineral acids, organic acids, oxidizing agents, water soluble
enzymes (catalysts) and in situ acid generators are spotted in a
wellbore after (or during) the filter cake reversal process. This
non-restrictive method may use a polymeric filtration control
additive, such as but not limited to a non-ionic starch or other
cellulosic additives, such as, but not limited to HEC (hydroxyethyl
cellulose). When one of these fluid loss control additives is
pre-solubilized in the water phase of a multiple phase composition,
the fluid loss control additive retards the disintegration of the
filter cake that happens when the oil is solubilized. The filter
cake becomes water-wet, but maintains a compact consistency for a
longer time when compared to the treatment without a fluid loss
additive in the multiple phase composition. The solid particulates
that once comprised the OBM filter cake, such as sized calcium
carbonate and barite, or any other particulates, are still in place
after the conversion. The fluid loss control additive found in the
multiple phase composition is deposited in and around pre-existing
particulates to redevelop a waterbased filter cake. It should be
recognized that this process, reversal of an oil wettability (OBM)
to water-based wettability, including the deposition of the
water-based fluid loss control additive occurs in a single
step.
[0048] As the OBM filter cake is converted with the aforementioned
water-based filtration control additive, the internal phase may
also contain acids, barite dissolvers (chelants) or other precursor
additives that can dissolve the acid-soluble particles or dissolve
the barite and break down the fluid loss additive (polymeric or
otherwise). The value of such a conversion using a multiple phase
composition to delay the forming of an in situ emulsion is that
more of the OBM filter cake may be converted to a water-based
filter cake containing dissolvable particulates that may be removed
in a single operational step compared to an emulsion formed at the
surface and lowered downhole.
[0049] Modified starches and/or biopolymers may be used to increase
the viscosity and/or other rheological properties of the multiple
emulsion, which also helps to control or delay the release of the
additives from the multiple phase emulsion by increasing the
viscosity and/or rheology of the multiple phase emulsion. Typical
modified starches used are known by those skilled in the art.
However, a modified starch usually refers to a carboxymethylated
starch, although the starch may be modified in other ways. One or
more carboxymethyl groups may be grafted on to a simple starch to
give it additional temperature stability as well as improved
rheological properties. Starches may also be crosslinked, such as
with agents including, but not necessarily limited to,
epichlorohydrin, polyvinyl alcohol, boric acid, glyoxal, succinic
acid, urea/formaldehyde, and combinations thereof.
[0050] In one non-limiting embodiment, the proportion of filtration
control additive in the multiple phase composition ranges from
about 0.1 lb/bbl independently to about 10 lb/bbl (about 0.7 to
about 29 g/liter). Alternatively, the upper proportion range of the
filtration control additive may be about 2.0 lb/bbl (about 5.7
g/liter). The exact or desired proportion of filtration control
additive in the multiple phase composition will depend upon a
number of interrelated factors, including, but not necessarily
limited to, the type of filtration control additive, the desired in
situ emulsion to be formed and type and proportion of components
therein, as well as the nature of the OBM filter cake being
contacted. In another non-limiting embodiment, the salts suitable
for use in creating the brine include, but are not necessarily
limited to, sodium chloride, potassium chloride, calcium chloride,
sodium bromide, calcium bromide, sodium formate, potassium formate,
cesium formate and combinations thereof. The density of the brines
may range from about 8.4 lb/gal independently to about 15 lb/gal
(about 1 to about 1.8 kg/liter), although other densities may be
given elsewhere herein.
[0051] It will be appreciated that it is not necessary for all of
the particles to be removed from a filter cake for the methods to
be considered successful. Success is obtained if more particles are
removed using the multiple phase composition than if it is not
used, as compared to the case where no multiple phase composition
is used. Alternatively, the methods herein are considered
successful if a majority of the OBM filter cake is removed. In
general, of course, it is desirable to remove as much of the OBM or
invert emulsion and corresponding filter cake as possible. One
non-restrictive goal is to remove filter cake particles to obtain
90% injection or production permeability.
[0052] The methods herein have the advantages of reduced formation
skin damage to the wellbore, and consequently increased hydrocarbon
recovery, and/or increased water injection rate, as compared with
an otherwise identical method absent the delivery of a multiple
phase composition that is broken for release of an additive in
order to form an in situ emulsion downhole.
[0053] Once the multiple phase composition has been broken, and the
internal phase or additive released, the released additive/internal
phase and the broken multiple phase composition may contact the
filter cake, so that an in situ emulsion forms downhole, such as a
microemulsion, miniemulsion, nanoemulsion, or mixtures thereof;
i.e. for purposes of wellbore cleanup. In a non-limiting
embodiment, additives that may aid in forming the in situ emulsion
include structural stabilizers, surfactants, co-surfactants,
viscosifiers, chelating agents, filtration control additives,
suspending agents, dispersants, wetting agents, solvents,
co-solvents, acids, and mixtures thereof.
[0054] Microemulsions are thermodynamically stable, macroscopically
homogeneous mixtures of at least three components: a polar phase
and a nonpolar phase (usually, but not limited to, water and
organic phase) and a surfactant. Microemulsions form spontaneously
and differ markedly from the thermodynamically unstable
macroemulsions, which depend upon intense mixing energy for their
formation. Microemulsions are well known in the art, and attention
is respectfully directed to S. Ezrahi, A. Aserin and N. Garti,
"Chapter 7: Aggregation Behavior in One-Phase (Winsor IV)
Microemulsion Systems", in P. Kumar and K. L. Mittal, ed., Handbook
of Microemulsion Science and Technology, Marcel Dekker, Inc., New
York, 1999, pp. 185-246.
[0055] A miniemulsion may form by having two immiscible liquid
phases mixed together, such as a surfactant and a co-surfactant,
via high shear mixing. Droplets of about 50 nm to about 500 nm may
form. A nanoemulsion has an inner phase that may act as an
emulsifier, such that the inner state disperses into nano-size
droplets within the outer phase. These types of emulsions may form
spontaneously.
[0056] In the foregoing specification, the method has been
described with reference to specific embodiments thereof, and has
been suggested as effective in providing a method for forming and
using a multiple emulsion for purposes of delaying the removal of a
majority of an oil-based mud (OBM) filter cake from a hydrocarbon
reservoir wellbore. The method may include delivering a multiple
phase composition downhole and breaking the multiple phase
composition for release of an additive or internal phase to delay
the forming of in situ emulsion, e.g. a microemulsion, a
miniemulsion, a nanoemulsion, or mixtures thereof, where the
delivered additive is utilized to form the in situ emulsion, for
wellbore cleanup for purposes of contacting the OBM filter cake
particles to remove the filter cake.
[0057] The multiple phase composition allows for controlled release
in space and time to form the in situ emulsion. However, it will be
evident that various modifications and changes can be made thereto
without departing from the broader spirit or scope of the invention
as set forth in the appended claims. Accordingly, the specification
is to be regarded in an illustrative rather than a restrictive
sense. For example, specific combinations of phases, agents,
additives, surface active material bilayers, structural
stabilizers, etc. and proportions thereof falling within the
claimed parameters, but not specifically identified or tried in a
particular method to improve the delivery of agents and components
herein, are anticipated to be within the scope of this
application.
[0058] The present application may suitably comprise, consist or
consist essentially of the elements disclosed and may be practiced
in the absence of an element not disclosed. For instance, the
method may consist of or consist essentially of a method for
removing a majority of an oil-based mud (OBM) filter cake from a
hydrocarbon reservoir wellbore by delivering a multiple phase
composition comprising an additive into the wellbore; subsequently
breaking the multiple phase composition thereby releasing the
additive; and then contacting the OBM filter cake particles with
the broken multiple phase composition and the released additive to
form an in situ emulsion downhole. This in situ emulsion may be a
nanoemulsion, a miniemulsion, a microemulsion, or mixtures thereof.
Finally, the method consists of or consists essentially of
incorporating a majority of the external oil from the OBM filter
cake and into the in situ emulsion.
[0059] The words "comprising" and "comprises" as used throughout
the claims, are to be interpreted to mean "including but not
limited to" and "includes but not limited to", respectively.
* * * * *