Note: Descriptions are shown in the official language in which they were submitted.
~1~~J~ ~~
WO 94/02567 PC'f/US93/06231
_1_
10 HARTH SUPPORT FLUID COP2POSITIOT~T
AI~7D METHOD FOR ITS USH
This invention relates to fluids for use in boring and
trenching operations in the foundation drilling industry,
the subterranean construction industry, and in well
drilling. More specifically, this invention relates to
earth support fluids, their composition, and techniques for
preparing, using, and maintaining them.
In creating foundations and shorings for buildings,
bridges and other structures and in excavating and
subterranean boring for installation of utilities, barrier
walls, transit ways and drainage systems. fluids have been
used to support the surrounding earth during construction
operations. Whenever subterranean construction must be
accomplished in granular, unstable, water-saturated or
gas-charged soils, it has been customary to fill the
boreholes, tunnel faces or excavations temporarily during
construction with water-based earth-support fluids, also
known as slurries or mulls. These slurries have consisted
essentially of water, a thickening agent and earth solids
from the excavation.
Z ~ Tbsa r n ran t- i n 1 t
~O__t _.___O__3_ ma_erlalS for making these s1 urri ec
are clays. such as bentonite and attapulgite. More
recently, water-soluble polymers have been introduced and
used in place of or in combination with such clays . The i
most widely used type of water-soluble polymer in these
WO 94/02567 ~ ~ ~ ~ ~ ~ ~' PCT/L,'51310623~
-2-
applications is a partially-hydrolysed polyacrylamide
(PHPA), in the form of a primarily linear, or non-
crosslinked, long chain polymer with an anionic charge
density of twenty to thirty mole weight. This chemistry is
available in both liquid water-in-oil emulsion form and in
dry form. Other polymers include dry forms of guar gum,
xanthan gum, cellulosic polymers, and blends of these. All
of these polymers, including the PHPAs, have been optimized
to be completely water soluble and/or homogenizable.
These polymers are designed to mix without forming
masses or pearls of undissolved or semi-hydrated polymer.
It has been customary to prehydrate and maximize
solubilization and homogenization of these materials before
i
introduction of the fluid into the excavation or borehole.
This has been accomplished through the use of induction
systems, recirculation, agitation, and processing of the
polymer, and retaining the prepared fluid in a maturation
tank for a period of time to maximize solubilization and
homogenization of the constituents of the fluid, prior to
introduction of the fluid into the excavation or borehole.
Clay slurries or muds are formulated with about five
to ten percent bentonite in fresh water or about five to
ten percent attapulgite in salty water. When tradi-tional__
polymers are used, the dosage is generally much lower and
ranges from about 0.01 to about 3.0 percent for most
applicatior_s. Whether the slurries are formulated with
clays or polymers, the object is to create a viscous fluid
that stabilizes and supports the walls of the exc:a_vation,
excludes groundwater and gases from the exeavati.~n, and
facilitates the progress of the construction protect. R
key to success in these efforts is to avoid loss or seepage
of the excavating fluid into the surrounding earth during
the excavating operation. If the fluid is lost into the
WO 94/02567
PC.°T/U~93/06231
-3-
earth (e. g. into a sandy formation) and the excavation
cannot be kept full of fluid, the excavation can collapse
and groundwater or gases can enter the excavation.
Excessive fluid loss can also disrupt naturally occurring
cohesive forces between the formation solids. Disruption
of this natural cohesion destabilizes the formation.
In the prior art the viscosity of the earth support
slurries has been maintained by design generally in a range
of about 30 to about 45 seconds per quart as measured with
a Marsh Funnel according to viscosity measurement
procedures standardized by the American Petroleum
Institute. This range of viscosities was felt, in light of
"industry knowledge" of the prior art, to be the most
effective and least damaging.
The cohesion of granular earth solids is governed by
the earth binding coefficient of the slurry. The earth
binding c~effieient is the composition's affinity for earth
solids, which causes the earth support fluid to chemically
and physically bond or attach to excavated earth, both on
the excavation tool and on the excavation walls. This
property preserves or improves the tendency of grains of
earth to hold together in mass as opposed to separating
into individual grains or smaller masses. This property
also improves the low-shear adhesion of masses of granular
earth solids to excavating tools, which aids in conveying
of the earth solids up from the excavation. The earth
binding capacity is also manifested as the ability of the
earth support fluid to film or encapsulate clay bearing
mineral solids and thereby reduce their tendency to adsorb,
absorb or take up water.
When clays or dry-form conventional polymers are used
to prepare the slurries, specialized equipment and
~1~30~_?~~
WO 94/02567 PCT/LJS93/06231
-4-
procedures have been necessary to mix the clay an polymer
(powder or granules) into the water, stir and homogenize
the mixture, transfer the slurry between the boreholes or
excavations and the mixing equipment, and process the
slurry to remove sand and excavated solids. This equipment
normally includes large mixing and holding tanks,
agitators, pumps, hoses or pipes, cyclonic desanders and
vibrating screen machines. Such equipment is large,
relatively complex and costly.
r
'
With some polymers, it has been possible to simplify
the mixing and handling equipment to reduce the investment
required and to simplify the handling of the slurries.
Depending on slurry composition and properties, it is
sometimes possible to operate without desanding equipment ,
and related tankage. For example, this might be possible
when non-thixotropic polymer slurries are in use. However,
all dry-form polymers in the prior art have required some
type of specialized equipment for successful prehydration
and mixing of the polymer into a homogeneous and fully-
dissolved form. The praetice of using such -mixing or
prewetting equipment is referred to herein -as - "ind~.rect
addition."
When the conventional liquid emulsion PHPA (mentioned
above) is used as the primary slurry additive, it has
occasionally been added directly into the borehole or
excavation, and the drilling or excavating tools-have been
used to mix it with water andlor fluid in the~borehole.
However, this is not the industry-preferred~me=thod for .
emulsion PHPA addition. Typically an eduction--.uni.t and
< hydration tank _ _- _ __W1t'h reri rCyl acing pypg acre ~ytil iZed tC ,
insure complete solubilization of the pohymer prior to
introduction to the excavation, or borehole.
WO 94/02567 PCTl~JS93/06231
Direct addition mixing has been claimed to be possible
far the liquid form of PHPAs, which has historically been
considered superior for mixability with, and solubility in,
water when compared to dry polymers, in a number of
industries. Emulsion polymers have been promoted as
possessing less tendency toward agglomeration and wastage
of polymer than can occur when attempting to mix dry-form
polymers with less-than-adequate equipment. Insufficient
shear is generally applied to accomplish complete inversion
of the emulsion PHPA and dispersion of the polymer in
direct-addition applieations. This has in actuality caused
considerable wastage of added polymer due to incomplete
inversion or inactivation of the polymer in the prior art.
The various industries have not widely recognized or
addressed the problems of incomplete inversion and
inactivation of liquid emulsion PHPA. Some manufacturers
and consumers have documented hydration and solubilization
problems occurring due to the hydrophobic surfactants and
the mineral oil contained in the emulsion polymers.
Problems such as delays in polymer inversion due to
inadequate inversion systems in the emulsions, and ---
inadequate mixing shear to fully break the emulsion micelle
and develop the polymer chains from an emulsion package
have also been noted. It has also been noted that the
surfactant and oil contained in the emulsion did not
completely disassociate from the emulsion-based PHPA. This
reduces performance efficacy through the coating and/or
blinding of active polymer sites. Some industries have
recommended the use of a high shear pump, such as the
Echols pump, or centrifugal pump, for premixing of both
emulsion and dry form PHPAs to insure cc~;plete
homogenization and solubilization. One publication -
specifically addressing these problems is '°Field
Application of PHPA Muds" by A. G. Kadaster & G. J. Guild,
~1 ~D~ ~'.~
WD 94102567 ~ '~ ' PCT/US93/U6231
Amoco Production Co.; G. L. Hanni, Amoco Norway Oil Co.;
and D. D. Schmidt, Amoco Production Co., SPA presentation,
1989, San Antonio, Texas.
The ability to rapidly mix and yield polymer directly
in the borehole or excavation is advantageous because it
eliminates the need for costly, cumbersome mixing and
processing equipment. It can significantly reduce time
required to drill, excavate and construct piers, walls,
pads, wells, etc.
Whenever polymer has been used, a primary objective in
mixing polymer into water or earth excavation fluid has
been to create a homogeneous solution or mixture and to
accomplish complete dispersion and dissolution of the
polymer as readily as possible. Completely dissolving and
homogenizing the polymer in the water or fluid has been
considered a key to optimum performance. Incompletely
homogenized polymer of any kind, whether in the form of
agglomerates, polymer strings, "fisheyes," gels,
microgels, pearls or masses has been- seen as
disadvantageous and wasteful. Avoiding the--presence of
incompletely hydrated polymer in the slurry has been a
prime objective of fluid design and mixing practice.
Although bentonite is the principal material used for
preparing slurries, bentonite slurries have become
increasingly regulated as pollutants, and as- a -result,
disposal costs have risen. Hentonite .slurries must now
generally be removed from a construction or drilling site
and disposed of in a designated landfill or~ir~.accordance
with local authorities and permits. Thi.~ additional cost,
along with the high capital cost and- complexity of
bentonite slurry mixing and processing equipment has
prompted increased use in subterranean construction and
WO 94/02567 ~ ~ ~R ~ ~~ ~ ', PC'f/LJ~93/06231
drilling industries of polymer, especially the liquid
emulsion PHPA.
According to current "industry knowledge", emulsion
PHPA requires less equipment to process and is seen as less
polluting. However, emulsion PHPA contains refined
hydrocarbon oils and surfactants, and thus creates
environmental pollution problems of a different kind. This
oil and surfactant-pollution problem has only recently been
acknowledged or widely considered. The EPA and other
regulatory agencies are beginning to recognize the
significant toxicity of these hydrocarbons in oil and gas
drilling. In addition to liberating a hydrocarbon into the
environment. PHPA emulsion is beginning to be recognized as
a potential fire hazard on-site. Special fencing and
precautions are now required or: sites where emulsion
polymer is being stored.
There has been little understanding of, or remedy
offered for a problem frequently encountered in boring,
drilling, and trenching (in non-mineral based slurries)°-
the problem of earth support fluid loss into permeable soil
formations. This seepage or "fluid loss" is common in
granular, permeable soils, such as sand and gravel, and in
fractured and fissured formations. Fluid loss can
seriously interfere with the processes of excavation,
drilling, or construction. Excessive fluid loss is a
primary cause of destabilization of the excavation,
pollution of groundwater, delays in excavation and boring
projects, increased concerns for safety, and increased
consumption of slurry, slurry additives, concrete, cement,
grout, etc.
Extreme cases of fluid loss have been attacked by
dumping bentonite, silts, andlor other available colloids
CA 02140125 2004-05-04
66382-175
_8_
into the excavation or by boring native silts and clays in
an attempt to form a mineral-enhanced filter cake at the
formation interface of the excavation. When a mineral-
based or mineral supplemented slurry is used in fine-grain
sands, the dispersed mineral colloids in the slurry can
provide improved control of fluid loss because the pores in
the soil are small. B»t mineral-based and mineral
supplemented slurries, due to the thick filter cakes they
create, reduce borehole gauge. This reduced gauge can
reduce the diameter of formed structures or casings created
in the excavations and boreholes. Similarly, mineral-based
and mineral supplemented filter cakes can negatively affect
the geometry of the formed structures or casing.
Additionally, mineral-based or mineral supplemented filter
cakes, as a sheath of continually reactive and hydratable
colloids at the interface between the concrete and
surrounding earth, can reduce skin friction on which formed
or poured structures rely for their load-bearing
capacities. Reduced friction may promote instability,
movement and stress on these structures, which can damage
the subterranean structure and the super-structure that
rests on them.
With polymer-based slurries containing no bentonite or
other cake-building inorganic colloids, fluid loss control
has been unattainable or poorly realized. The dissolved
water-soluble polymers cannot plug the pores in the
granular soil or create a filter cake as can bentonite and
inorganic colloids. It has been impossible to control
fluid loss without adding mineral colloids, similar
colloids or finely-divided materials such as native clays
and silts incorporated into the slurry from the excavation.
CA 02140125 2004-05-04
66382-175
-8a-
In one aspect, the invention provides a method
for the preparation and use of an earth stabilization
fluid having a Marsh funnel viscosity of at least
35 seconds/quart, comprising: a) adding an aqueous based
5~ continuous phase into an earth cavity; b) adding an anionic
polyacrylamide co-polymer having an anionic charge density
between about 5 and 900, said co-polymer forming a plurality
of transitory, deformable masses in said continuous phase;
and c) excavating to form said cavity while a portion of
said co-polymer is in a transitory partially-hydrated
swollen state.
In a further aspect, the invention provides an
earth stabilization fluid for use in a low shear environment
comprising an aqueous continuous phase and a plurality of
transitory composition pearls or masses larger than 10
microns suspended therein, said composition pearls or masses
being formed from a functionally effective polymer, wherein
the polymer is composed of monomers selected from the group
consisting of: acrylic acid, methacrylic acid, malefic acid,
malefic anhydride, fumaric acid, itaconic acid, acrylamide,
methacrylamide, an N-substituted acrylamide, acrylonitrile,
methyl acrylonitrile, vinyl and styrene sulfonic acid, vinyl
acetate, 2-acrylamido-2-methylpropane sulfonic acid,
methallylsulfonic acid, water soluble salts thereof, and
combinations thereof, and wherein the polymer has a
molecular weight greater than 10,000.
Figure 1 is a graphic representation of the Marsh
funnel viscosity versus the CDP dosage. The term ~~CDP"
aJ
WO 94/02567 P~'1US93/06231
_g_
shall be understood to refer to the trade name for a
polymer based product within the scope of this invention
marketed by ICS Technologies Ltd.
Figure 2 is a chart showing a comparison of viscosity
development efficiency using a composition and method of
this invention.
Figure 3 is a graphic representation of the flLlid loss
control characteristics of the composition and method of
this invention in comparison to prior art compositions and
methods. Figure 3 also shows the effects of hydration time
on fluid loss control of a composition and method of this
invention and on a prior art polymer composition and
method, both compared to bentonite. ,
Figure 4 is a chart showing filtration control
performance versus time at equal hydration times (30
minutes) for a preferred embodiment of this invention and
for a composition of the prior art.
Figure 5 is a graphic.representation of peak values of -
perimeter frictionlcell pressure from extraction testing
for fine sand specimens drilled under CDP slurries.
Figure 6 is a graphic representation of a comparison
of perimeter load transfer coefficients for various
materials.
Figure 7 is a graphic representation of viscosity
development efficiency of CDP versus emulsion PHPA at high
dosage ranges.
WO 94/02567 PCf/US93/ObZ31
-10-
Figure 8 is a graphic representation of a comparison
of mean normalized perimeter shear for 24 hours contact
time.
The present invention is a water-soluble,
water-swellable, hydratable and/or water-dispersible
materials) and a method for using the materials) to
prepare and maintain earth support fluids. The earth
support fluids have suspended therein partially-dissolved
or hydrated or dispersible synthetic, natural" or modified
natural polymers; synthetic and natural resins and latexes;
as well as all grafts and blends of the above materials
with or without surfactants or hydration inhibitors. The
earth support fluids are prepared and maintained without
added commercial mineral colloids, and exhibit fluid loss
I
control and preferably one or more of the following
properties: borehole or excavation wall stabilization,
earth solids encapsulation, improved cohesion of the
excavated earth" and improved development of perimeter load
transfer at concrete-to-earth interfaces in subterranean
structures formed in excavations. It should be understood
that for purposes of this application the t-erms '"perimeter
load transfer", "perimeter shear", and °'skin friction" are
used interchangeably. . ___
A preferred embodiment of the present invention
displays, due to the combination of molecular weight and
anionic charge density of a polymer of the--invention,
improved earth b3_nding characteristics expressed by
improved cohesion of excavated earth solids-,=- especially ,
sands and gravels. This improvement is earth;_binding and
cohesion facilitates ~xcavatior~ operations, especially
auger drilling, and results in greater productivity.
21~ ~~.:
WO 94/02567 PC'flIJS93/06231
-11°
The materials of the present invention, due to one or
any combination of their properties (their ionic charge
density, molecular weight, chemical composition, cross-
linking, surfactant treatments, physical granulometry,
particle shape, plasticity, hydration characteristics,
solubility characteristics), can provide fluid loss control
when used according to the methods defined in this patent.
This method provides for partially--hydrated or functional,
insoluble particles (hereinafter referred to as ',pearls°' or
"masses") to be dispersed in the slurry at all times or at
specific times of need during the excavation or drilling
process.
The "gel masses" or "pearls" of this invention are
formed upon hydration. These masses are foraned in a
variety of sizes and shapes, including but not limited to
planar configurations (such as a potato-chip
configuration); spheroidal configurations, elongated i
finger--like configurations, and deformable globules.
The dimensions of the hydrating or hydrated masses can
range from 10 microns to about 100 mm with presently
available materials, and can be larger if composed of
multiple individual masses which have fused together in the
process of hydrating. Still larger hydrating or hydrated
masses may be possible with modifications in the
preparation of the dry compositions to produce larger dry
particles which are the precursors of the hydrated masses.
The smallest hydrated masses are produced by dissociation
of larger hydrated masses or by direct hydration of finely-
divided dry composition particles.
The masses, when present in the fluid, can be
partially or fully hydrated. The masses are preferably
deformable. This deformability helps the masses conform
PC'I"/iJS93/06231
WO 94/02567 ~ ~ r~ ~ ~' ~ '~
-12-
to, lodge in and constrict or.plug pore spaces in granular
permeable formations. This mechanism eontrols fluid loss.
The masses can have a finite life span in the fluid,
corresponding to the time required for the masses to
completely hydrate and dissolve in the case of compositions
which are completely water-soluble. For compositions which
are hydratable or water-swellable, the masses may go
through phases of hydration followed by dissociation.
During the hydrational phase the masses generally become
larger; then at some point they can begin to dissociate and
may produce many smaller hydrated particles or
hydrocolloids in the fluid:
The hydrated or partially-hydrated natural and
synthetic polymers which form masses that plug the pores in
granular soils, and thereby slow the seepage of the earth
support slurry into the surrounding soil, are preferred.
Polymers whieh exhibit earth binding capacity are
preferred. Polymers which allows high formation-to-
concrete adhesion, which is expressed as "perime.ter_ load
transfer coefficient", are also preferred. --- _- _
The ability of the polymeric and resinous materials to
form both transient or degradable pearls or masses ox foxm__ _
more persistent pearls or masses for controlling fluid
loss, or for optimally plugging porosity in permeable
formations is achieved in the manufacturing or processing
of the material or during preparation of the fluid_in the
field by one or more of the following techniques:_-(a)
partially crosslinking the material to retard hydr-ation,
reduce solubility, and increase branchirc: (b) r~iahly
crosslinking the material to retard hydration and reduce
solubility; (c) surface treatment (including in-situ
co-addition) of the materials, as with a surfactant; a
2~_r~~ ~~~
W~ 94/02567 P~'/US93/06231
-13-
coating, microencapsulation, or physical processing, to
retard hydration; (d) blending the materials with
co-additives (e. g. electrolytes, divalent rations, etc.)
which retard hydration; (e) granulation or flaking or
agglomeration and sorting to optimize particle size of the
dry materials, which impacts rate of hydration for
hydratable materials and the size of semi-hydrated
particles in the slurry; granulation and size sorting also
ianpact pore-plugging performance of insoluble or plastic
particulates; (f) copolymerizable surfactants being
incorporated in the polymers backbone which impact
hydrophilic tendencies; (g) polymerization to yield an
amphoteric or ampholytic structure; (h) grafting materials
together to form an optimized end material; and (i) the
incorporation of a hydrophobic or semi-hydrophobic, or
non-water soluble material to retard water solubilization.
r
within the scope of this invention are synthetic,
natural and modified natural polymers, including blends and
grafts, which are prepared and used in ways which create a
fluid comprising a continuous liquid phase in which is
present a plurality of hydrat~.ng or hydrated polymer
masses. Examples of such materials are synthetic polymers,
polysaccharides, gums, biopolymers and combinations
thereof. In a preferred embodiment of this invention an
anionic, polyacrylarnide copolymer forms both the continuous
fluid phase and the discontinuous phase of hydrating or
hydrated masses dispersed in the fluid. In an alternate
embodiment, hydrating or hydrated masses of natural
polymers or modified polysaccharides are suspended in a
continuous fluid phase of solubilized anionic
polyacrylamide copolymer.
The polymers of the present invention are preferably
added in a solid granular, flaked, or agglomerated state
2~~~ ~~_
W~ 94/~D2567 ~~.TlUS93/06231
_14_
with the dry particles ranging in size from 0.01 mm to 50
mm (in certain flaked products), and currently :in a range
of 0.01 mm to 10.0 mm, and with the majority by weight of
the particles being between 0.10 mm and 2.5 mm for most
available products. All of these materials become larger
when initial hydration occurs, although dissociation may
eventually reduce the hydrated particle size.
The polymers of the present invention form vi.scuous
fluids with Marsh Funnel viscosities ranging from about 35 '
to about 300 seconds per quart, and more preferably within
the range of about 40 to about 120 seconds per quart.
Increased viscosity is a key feature ,of the present
invention. Viscosity, polymer selection and polymer dosage
are specified in relation to reactivity, hydrational
l
potential, granularity and porosity of the earth formation.
The resultant slurries should allow settling of disturbed l
earth solids larger than about 70 microns as well as j
dispersion of additional fresh polymer.
The present invention comprises a method of
formulating and using an earth support fluid containing
polymers which controls fluid loss, stabilizes the
formation being excavated, improves loading and removal of
earth by excavating tools, and allows development of high_ _
concrete-to-formation friction coefficients. The methods
may be used in subterranean construction operations,
excavations, and well drilling wherein an earth support
fluid or drilling fluid is used in a vertical, angled, or
f~
horizontal borehole, tunnel, trench, or other excavation.
_ __ _ _ ._ _ ._ _
_ _
The proportion of material in this fluid composition
can range from 0.1 to 100 kilograms per cubic meter by dry ,
weight of material on volume of water or slurry. The Marsh
Funnel viscosity of the fluid is preferably maintained
WO 94/02567 PCf/LJS93/06231
-15-
between 35 seconds and 300 seconds per quart: more
preferably between 45 and 120 seconds per quart; and most
preferably between 55 and 100 seconds per quart. Figure 1
is a chart showing the Marsh funnel viscosity versus
polymer dosage for one embodiment of this invention.
The method comprises formulating as the earth support
fluid an aqueous slurry having suspended therein water-
soluble, water--swellable, hydratable and/or water-
dispersible compositions. The earth support fluids contain
suspended therein partially-dissolved and/or hydrated
and/or dispersible synthetic or natural polymers, resins
and/or latexes; and all grafts of the above compositions.
The molecular weight of the compositions) may vary over a
wide range, e.g.. 10,000 - 40,000,000 or higher. The
invention, however, finds its greatest usefulness when
acrylamide copolymers having molecular weights of 100,000
or more, preferably one million or more, and most
preferably in excess of 10,000,000 are applied. The
anionicity of the copolymer may be obtained from the
hydrolysis of acrylamide during the polymerization or from
the copolymeration of acrylamide with the anionic monomers
comprising acrylic acid, methacrylic acid, malefic acid,
malefic anhydride, fumaric acid, itaconic acid, vinyl or,
styrene sulfonic acid, 2-acrylamido-2-methylpropane
sulfonic acid (AMPS) and the like, and water soluble salts
thereof. The preferred anionic monomers are acrylic acid,
methacrylic acid, malefic acid, vinyl or styrene sulfonates
and AMPS or their salts. Copolymers comprising acrylamide
and/or other non-ionic monomer, with more than one anionic
monomer foregoing is also within the scope of the
invention.
The molar percentage of the comonomers in the polymer
may vary within certain limits, provided that the total
WO 941025f>7 ~ ~ ' ~ ~ '~ 'j PCT/LJ~93/06231
-16-
adds up to 100.. The anionic charge density will vary from
about 5~ to 90$, preferably 10~ to 80~, and most preferably
35~ to 65~ in the polymer. The composition, anionicity,
and molecular weight of the copolymer may be optimized for
the particular earth formation and water conditions in
order to achieve the desired drilling, boring, or
excavation and earth supporting functions.
The anionic copolymer of the invention may be further
modified by incorporating certain cationic monomers in the
polymer forming ampholytic polymers. The cationic monomers
are selected from the group consisting of:
diallyldimethylammonium chloride, quaternized
dimethylaminoethyl (meth)acrylates and N,N-
dimethylaminopropyl (methacrylamides) and combinations
thereof. The quaternizing agent may be methyl chloride or
dimethyl sulfate.
Non-ionic monomers for use in the practice of the
present invention axe selected from the group consisting:
acrylamide, methacrylamide, N-vinyl pyrrolidone, _vinyl
acetate, stryrene, N-vinyl formamide, N-vinyl aceta~nidewo-r
mixtures of the forgoing. Especially preferred is
acrylamide.
A small amount of water insoluble/hydrophobic-monomers
such as Cs to C,o long chain alkylates , hydroxyalkylates , and
N-alkyl substituted acrylamides may also be incorporated in
the copolymer of the invention. These hydrophobic_groups
tend to associate with one another in an aqueous salution
to form an inter/intra molecular association. As a result,
the solution viscosity is increased a~.d the viscosity is
relatively insensitive to salts as compared to polymers
without the hydrophobia groups.
2
WO 94/0267 PCf/1JS93/06231
-I7-
Polymerization of the monomers may be conducted in the
presence of a crosslinki.ng agent to form the crosslinked or
branched composition. The crosslinking agent comprises
molecules having either a double bond and a reactive group,
two reactive groups or two double bonds. The agent may be
selected from a group comprising N,N-
methylenebisacrylamide, N,N-methylenebismethacrylamide,
polyethyleneglycol di(meth)acrylate, glycidyl acrylate,
acrolein, methyoacrylamide, aldehydes, glyoxal,
diallylamine, triallylammonium salts, ammonia, C$ to Cu
amines (including diamine or triamine), epichorohydrine,
diepoxycompounds or the like and mixtures of the foregoing.
The crosslinking or branching is due to the inter or intra
molecular reactions of the monomeric units in the polymer
chain with the crosslinking agent. The agent is to be used
r
in sufficient quantities to assure a crosslinked or
branched composition so long as the resulting polymer is
still water soluble or hydratable. Preferably, 0.001$ to
20%, and more preferably 0.01 to 10~ based on the total
monomer weight, is used for the purpose. The proportion of
these materials in this application can range from 0.01 to
300 kilograms per cubic meter by dry weight of polymer on I
volume of water or slurry.
_ 25 The Theological profile of the polymer fluid is
significantly impacted by the anionicity and the degree and
type of crosslinking. Figure 2 is a chart showing a
comparison of viscosity development efficiency using a
composition and method of this invention.
The composition pearls or masses can exhibit a finite
and co;~;rollable life span in the excavation fluid. This
life span can range from several minutes to several weeks
based on the composition chemistry, physical and chemical
properties of the excavation fluid. The composition
WO 94/02567 ~ . ;~ ~~ P~T/U~93/06231
~~~~ ~~_;~~
-la-
masses' life span can be controlled by any one or a
combination of the following chemical mechanisms: (1)
degree of crosslinking and/or branching; (2) method of
crosslinking and/or branching; (3) solubility, and/or
hydrophilic/hydrophobic nature of the compositions; and (4)
inclusion of coadditives and/or surface treatments to the
compositions.
The composition masses' life span may be influenced
in-situ either positively or negatively by continued
exposure to shear stress, exposure to cations or '
electrolytes, exposure to earth solids, or continued
hydration over time. A composition pearl or mass can be
defined as a discrete constituent, or element, existing . !
independently within an excavation fluid, and possessing
the characteristics given above in the Summary of
Invention. These pearls or masses impart unique
performance characteristics to the fluid allowing for the
reduction of fluid loss to the excavated formation. The !
composition pearls' or masses' ability to decrease
formation porosity at the formation interface is achieved
through the pearls or masses being drawn into the formation- -
voids and completely or partially plugging and sealing
these voids. i
As these composition pearls or masses build on one
another they constrict or plug pore throats to reduce fluid
loss. A filter cake or matrix seal of synthetic or natural.- --
polymer and/or resin is formed. This filter cake nr sealw.
3C may incorporate water soluble polymer or resin to furthers_
improve filtration control and filter cake constructian~ __
The optimization of these pearls or masses is essential to
the unique properties of the fluid and the filter c-ake.
These composition pearls or masses of synthetic or natural
polymer or resin or combinations thereof allow for the
r 9 r
WO 94/02567 PC.'T/LJS93/06231
-19-
elimination of bentonite, silt, and/or other colloidal
material from the fluid design when used in one method of
this invention.
The interaetion between the pearls or masses. the
polymer, and the earth forms a filter cake on the fluid
column walls. The polymer filter cake significantly
assists in maintaining a stable side wall in the formation.
Side wall stabilization is enhanced by reduction i.n fluid
loss to the formation, maintenance of hydrostatic pressure
differential transferred through the wall cake and j_n-depth
matrix seal, and increased earth binding capacity of the
fluid.
i
The polymer filter cake produced by this invention
significantly reduces the fluid loss to the surrounding
formation. Fluid loss to the formation hydrates the
formation and disrupts the natural cohesive forces between
formation solids. This loss of cohesive forces causes side
wall sloughing and cave-ins. The polymer filter cake
maintains a significantly more stable excavation than that
known in the prior art by reducing the hydration of the
formation and maintaining a hydrostatic pressure
differential through the cake.
Figure 3 shows the fluid loss control versus hydration
time of the preferred embodiment of this invention and two
other commercially available construction drilling slurry
products. Hydration times shown in Figure 3 are time
elapsed between introduction of polymer into mix water and
initiation of filtration test. Commercially available
products were mixed at iow-s::ear with a single corrugated
disk impeller at approximately 3,000 RPM. The products
were stirred for 5 to 10 minutes and were unstirred during
the remainder of the hydration time. Bentonite was mixed
2
w'O 94/02567 P~"/U~93/06231
-20-
at a high shear to assure good dispersion. The test was
conducted at a 5 psi pressure differential against a
manufactured, artificial sandstone disk, 1/4" thick having
a permeability of 20 darcies and a pore diameter of 60
microns nominal.
Figure 4 is a chart comparing filtration control
performance of a preferred embodiment of this invention to
filtration control of a prior-art~polymer fluid, when both
polymers have equal times of hydration.
In a preferred embodiment of this invention, the
polymer materials are introduced into the fluid by direct '
addition into the mouth of the borehole or excavation and
the excavating or drilling tools are used to mix the fluid
in-situ without benefit of other specialized mixing or
pre-mixing equipment or procedure. ;
In an alternate preferred embodiment of this
invention, the materials used to create the earth support
slurry are introduced indirectly into the mouth of the
borehole or excavation, without the excavating or drilling --
tools being exclusively used to mix the fluid in-situ.
Material would be added to the system with the benefit of
other specialized mixing, pre-mixing equipment, hoppers, or -- --- _ _
other indirect procedures.
The charge density characteristics of the polymers of-
the invention are a primary factor in the earth binding
capacity of the fluid. Earth binding capacity is--a.
polymer's or material's ability and capacity to bond to and_._
stabilize exposed or excavated earth. This affinity
i
functions to improve side wall stabilization, borehole i
gauge and removal of excavated earth. Anionic charge
density, or the ratio of anionically charged pendant units
WO 94/U2567 PCT/US93/Oti231
-21-
on the polymer, is a primary contributor to the degree of
earth binding capacity a polymer possesses.
In one preferred embodiment of this invention, the
excavation carrying capacity, or the ability of the
excavation tools or systems to hold and remove increased
loadings of earth, is significantly improved due to the
earth binding capacity of the slurry. The improved earth
binding capacity allows removal of excavated solids, or
earth, with excavation tools not previously successful when
prior art materials have been used. Improved excavation
carrying capacity increases the efficiency of the
excavation operations.
In a preferred embodiment of this invention, the
polymer is a water-soluble or partially water-soluble or
hydratable or water-dispersible linear, branched,
crosslinked, partially-crosslinked, or grafted material,
which is further treated with hydrophobic surfactant to
retard hydration or through blending the materials.
Hydrophobic surfactants can be added by in-situ co-
addition, coating, micro encapsulation, or physical
processing.
__ _ 25 When the polymer of the subject invention is non-
crosslinked and water-soluble, partially water-soluble,
hydratable or water-dispersible, the granulometry,
hydrophiliciLy/hydrophobicity, molecular weight, rate of
dissolution, and other factors are combined with an
application technique which exploits the transitory '
hydrational phase (the period of time during which the
polymer is suspended in the fluid as discrete partially-
dissolved or dissolving masses or pearls) to accomplish
control of fluid loss.
WO 94/02567
PC'fl~JS93/06231
-22-
Hydrophobic surfactants can be incorporated into the
polymer during manufacture and as an~'interstitial component .
dried within the polymer granuleylor as a post-manufacture
surface treatment to retard~hydtation and prolong the
duration of pearls or masses with and without crosslinking.
The hydrophobic surfactants comprise surface active agents
having HLB (hydrophilic/lipophilic balance) values in the
range of about 2 to about I0, preferably less than 8.
Suitable surfactants include sorbitan esters, phthalic
esters , fatty acids , glycerides , glycerines esters , as well
as amides and ethoxylated or propoxylated versions of the
above. A preferred embodiment of this invention
incorporates slightly to moderately crosslinked polymers
with slight surfactant treatment. i
In one preferred embodiment of this invention, the
pearls or masses are transitory. The transitory nature of
the pearls or masses is controlled by the type and amount
of crosslinking of the polymers. The polymer crosslink
ruptures over time and the pearls and masses degrade.
Hydration, shear and ionization degrade the total polymer_
and disrupt the mass structure. The soluble polymers-,- --_-
pearls, and masses, collapse or degradation can be
accelerated by contact with divalent and trivalent cations,
oxidizers and/or chlorides. This collapse or degradation- _- -
of the pearls and masses is critical for construction and
other industries where concrete, grout, cement, or other
materials are placed in a column, wall, or trench. In _ _.-
these applications side wall friction, or side wall load-
bearing capabilities are important. This invention.
provides for significantly reduced residual interference ___4
with side wall characteristics. thereby producing improved
structural integrity and load bearing capacity. -
WO 94/025b7 Pf.T/U~93/06231
-23-
The degradation of the solubilized polymer, pear~.s and
masses within the fluid as well as at the side wall
interface significantly improves the side wall friction
coefficients over prior art drilling and excavation fluid
technologies. Figure 5 shows a graphical representation of
perimeter friction/cell pressure from extraction testing
for fine sand specimens drilled utilizing prior art
technology and a preferred embodiment polymer. Slurry
degradation also improves displacement by concrete, cement,
grout, etc. yielding improved quality of the final i
structure or plug due to decreased contaminant intrusions,
voids within, and/or direct contam~.nation of the concrete,
cement, grout, etc. of the final structure.
In one preferred embodiment, the hydrated or
partially-hydrated natural and synthetic polymers form
masses that plug the pores in granular soils. and thereby
slow the seepage of the earth support slurry into the
surrounding soil. Polymers which exhibit earth binding
capacity are preferred. Polymers which allows high
formation-to-concrete adhesion, which is expressed as
"perimeter load transfer coefficient", are also preferred.
See Figures 6 and 8.
Figure 8 shows skin friction development of a
preferred embodiment of the invention after 24 hours
contact time in an experimental drilled shaft. The figure
shows that the preferred embodiment outperformed bentonite
in developing skin friction. The figure also shows, by
omission when compared to Figure 6, that slurries
formulated from attapulgite and from emulsion PHPA failed
to maintain. a column of slurry in the experimental drilled
shafts due to complete fluid loss. The polymer of the
present invention developed the highest skin friction of
WO 94/02567 PCTlLJ~93/OG231
-24-
the slurry formulations which were capable of maintaining
fluid in the experimental drilled shaft for 24 hours.
In still another preferred embodiment of this
invention, dry particles, flakes;', agglomerates, or crystals
of materials used to prepare a slurry are sorted or
produced to consist of various size particulates or flakes,
ranging in size from 0.01 mm to 50 mm, preferably 0.01 mm
to 10.0 mm, and most preferably 0.10 mm to 2.5 mm as
l
determined by screening with sieves having openings of
these sizes. The dry particles, flakes, or crystals of
materials used to prepare the slurry are of various sizes. G°.
The materials are produced, sorted and selected in various
particle-size sub-ranges to optimize fluid loss control
performance in specific types of granular, vugular or
fractured earth formations having varying sizes of pores, ,
vugs or fractures. The larger particle sizes are required
for such porous formations as sand, gravels, cobbles and
glacial tills. Less porous formations, such as hydratable
shales, clays, and silts requi~~e smaller particle sizes.
The choice of particle size is important in optimizing
product efficiency in different formations. In a preferr-ed _
embodiment of this invention, the particle size for the
granular, flaked or agglomerated polymer ranges from 0.01 _
mm to 50 mm, preferably 0.01 mm to 10.0 mm, and most=---- _
preferably 0.1 mm to 2.5 mm, with the majority by weight of
the granules being between 0.40 mm and 2.5 mm.
All embodiments of this invention may be manufactured
and used in liquid farm, i.e., as an emulsion (oil---
continuous or water-continuous), suspension form,
dispersion form, solid form, or solution form. The
preferred physical form is dry granules, flakes or
agglomerates.
21~~~ ~/~..
:~.J ty
WO 94/02567 PCT/~1593/06231
-25-
One preferred embodiment of this invention is a
polymer with anionicity ranging from approximately 35$ to
approximately 65~ with a molecular weight in excess of
100,000, preferably in excess of one million and most
preferably in excess of ten million, as measured prior to
cross-linking, which is slightly crosslinked from 0.01 to
10~ using either aldehyde, C1 to Cu alkylamines including
diamine and triamine, and/or methylene bis acrylamide. The
polymer is either a copolymer of acrylamide and acrylic
acid or malefic acid, maleie anhydride, or fumaric acid, or
AMPS, styrene sulfonic acid. vinyl sulfonic acid.
methallylsulfonic acid, and their salts and any combination
thereof. The molar ratio of these components can vary in
order to achieve the desired anionicity for the particular r
a
formation and water conditions. particle size for the
granular polymer in most formation conditions should range
from 0.01 mm to 10.0 mm with the majority of the particles
being between O.l mm and 2.5 mm. A viscous earth support
fluid is preferable with Marsh Funnel viscosities ranging
from approximately 35 to in excess of 300 seconds depending
on the reactivity and porosity of the formation. all.
fluids should be as non-gelling as possible to allow
settling of disturbed earth solids as well as dispersion of
additional fresh polymer.
Example
A dry granular water-soluble polymer slurry of the
present invention was tried under a field test in Seattle,
Washington. The field test drilled over twenty soldier
piles for the foundation of a building. The new dry
polymer demonstrated very good performance in comparison to
an industry-standard oil continuous phase emulsion polymer
with an average charge density of 30~ anionic, which had
previously been used, and displayed advantages in
21y~~
WO 94!02567 PCT/US93/06231
-26-
controlling fluid loss to the borehole, cleaning the hole
and loading the auger, simplirying polymer handling and
addition, increasing drilling efficiency, and reducing
polymer waste and environmental impact. This initial
applieation of the polymer was successful and indicates
that the novel dry polymer may be a valuable new tool for
the foundation drilling industry.
Small quantities of a dry granular polymer of the
present invention, CDP solid, and a liquid emulsion analog
of the present invention, CDP Liquid, were supplieCl. Of
fourteen soldier pile holes , nine were drilled with the new
dry~polymer, CDP Solid, three were drilled with the liquid
analog, CDP Liquid, and two were drilled with the industry
standard 30~ anionic PHPA emulsion polymer.
The soldier pile holes drilled with slurries prepared
from the three different polymers ranged in diameter from
30 inches to 42 inches, and in depth from 28 feet to 42
feet. The formation was glacial till, poorly sorted, with
lenses of sand, layers of silty clayey sand, and sandy silt
with cobbles and gravel. Water was encountered a.t-various
depths within the boreholes, and in some holes strong water
flows were encountered. One hole was a re-drilling or
reaming-out of a water extraction well previously drilled
on the property to help lower the water table on_site.
The competitive test showed that the polymers o~.the
invention had advantages over the conventional emulsion
polymer with the dry form of the invention demonstrating
__
advantages in ease of use. The advantages ~i.ncluded:
superior control of fluid loss to the borehole: greater
ease of use by the drilling crew; reduced product
requirement [the dry polymer replacing the conventional
polymer emulsion on a 1:6 basis!; reduced wastage;
~~.~~:~3~.~r
WO 94/2567 pCT/LJ~93106231
-27-
increased rate of penetration; improved cohesive loading of
drilled earth solids on the excavation tool, and reduced
environmental pollution.
Although particular detailed embodiments of the
apparatus have been described herein, it should be
understood that the invention is not restricted to the
details of the preferred embodiment. Many changes in
design, eonfiguration, and dimensions are possible without
20 departing from the spirit and scope of the iaastant
invention.
