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METHOD FOR l~ED~~~ INIG AQUEOUS CONTENT OF OIL-BASED FLUIDS
FIELD OF INVENTION
100011 I'he invention relates generally to weIlbore fluidS, and more
specifically
to -thhe removal of the aqueous content from the oil-based wellbore fltiids.
BA~~GR~~~~~ OF INVENTION
[00021 When d~.iling or cOmpletii-~g wells in earth ftarniat~onss various
fltiids
typically are used in the well for a variWy of r~~~~i is. Common uses for welI
fluids include; lubrication a-nd ccsoling of drill bit cutt~~ surfaces while
drilling generally or drFiling-in. (i.e.> drilling in a targeted
petro~li~erous
t't~rmat.iion)a transportation of <acuttiitgs ' (pieces of fonnat~~n dislodged
by tlie
cutting action of the teeth on a drill bit) to the surface, controlling fo.Ãm.
ation
fl-Lii~ pressure to prevent blowouts, maintaining well stabzliq-, suspending
solids i.n the well, minimizing fluid loss into and stabilizing the 1'o3r~-
natir~~
through. which the weIl. is being drilled, fracttiring the fOtination in the
vicinitv of the weli, displacing the i-luid within tl~e well with another ~l-
Liid,
cleaning the weli, testiiig ttie wt:ll, flitid used for emplat:ing a packer,
tihaiidOiiing the well or prt?parinp- the well for ah~~~~onn-ient, and
othem~,ist;
treating the well or the fo.rmation.
[00031 Drilling fluids or muds typically include a la~se, fluid (water, diesel
or
mineral oil, or asy-titlictic c~i-n~ound); weighting agents (most frequently
barium sulfate or barite is used), emulSx~`~ers and emulsifier systems, fluid
loss
additives, viscosaty regttTators and the like, for stabilizing the sysl:ezn as
a
whoic and for establishing the desired performance properties,
[0004] 0il-based drilling 'fltxids are, generally u.~ed in the f`s . of
irivert
emulsion miids. Invert eintiisior~ ~~iid~ are en~ployed in drilling processes
for
the development of oil or gas sources, as well as, in geOt~ernia.l ii:zilling,
Water
tl-rii7ing, ~eoscientific: drilling, and mine rlrilling, Specifically, tlte
tnvert
eriiulsion fluids are ctaitvetita~nally utilized for such purposes as
prottidin. g
t
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stability to the drilled hoIe, forining a thin filter cake, iubricatingthe
drilling,:
bor~. and the doWnhol~ area and assembly, and penetrating salt beds witliOut
sloughing or enlargement of the drilled hole.
[00051 An invert ~i-nuisioii n-iud consists of three phases; an. oleaginous
phase,
an aqueous phase, and a finely divided. particle phase. "rhe discontinuous
aqueotis phase i-s dispersed in an exfemal or ~ontit~~~ous oleagknou:s phase
tvi~h,
the aid of one or iilor~ emulsifiers. 'rhe oleaginous pl-xase may be a mineral
or
synthetic oil, diesel or crude oil, while the a~~~~oLis phase is u~~ially
calcium
chloride, sodium chloride or other brine.
~~~061 `Fhe dispersed aqueous phase has several functions. ~'be aqueous phase
replaces part of the oleaginous phase, thereby building volume and reducing
the total fluid cost. Further, the aqueous phase contributes to tluid density
through its higher specific gravity;. The highly dispersed state of the
aqueous
phase contributes to :rhe~lovy and to fluid loss control. The dispenss:d
aqueous phase als~.~ heIps improve the inhibition of iwrater~~~active shales
by
creating a favorabiessaiinit;: '~~lmice.
100071 `Flic volume ratio of ttie oIeaginotis phase tc? the aqueous phase is
referred to as tlte oil/water ratio (OU'R): I'~~ OWR is commonly quoted as
proportions out of a total of one hundred units, e.g. 90/10, 75!25, ete.
Occasionally, tin-ough contami~iati~n at surface or influx of fort-natbon
waters
downhole, the water cut of an oil-based fluid increases, thereby decreasing
the
OV,R< Such a decieas-e in the OWR. can have an adverse effect on the
rheology, density, and et:nulsion stability of the fluid. There ~~e also
occasions where ~ii e-xistingg fluid, designed originally to have. a higiaer
water
cc~~~ent, may have to be Lised in a drilling operation that requires a lower
water portion. In both such cases, the water cut of the fluid has to be
reduced
in order to bri-ng back the, fluid properties within specification. 'tn othcr
words, the OVvrR, kias to be increased.
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~~~~~~ Previous attempts in the prior aTt to increase OWR has included
dilution
with the oleaginous phase, i.e. adding more oil to the oil-based drilling
fluid:
However, as more oil is added to the drilling fluid, the amount of fluid
additives, s-tach as rheology and fluid loss additives and weight material,
necessarily increases in order to maintain the varl0~s desirable fluid
properties. Consequently, not ortly does dilution of the oleaginous phase
increase the o-,~,erall volume of the drilling fluid, but it also increases
costs,
~~iventory5 and waste,
100091 Previous a~~inpts in the prior art have also used a desiccant to remove
small portions of water from a drilling fluid. This has been usefi.al in
applications requiring the drilling fluid remain in a water-free stafe.< While
these a~~~n-ipts have been sus:cessfiil a:t re:~~~~~~ small quantities of
water,
these attempts have not addressed the iieed to remove large amounts of water
~~om the drilling fluid during drilling, or adjusting aii existing fluid to
meet
the requirements 'for aparÃ.icWar application. Further, these attempts do not
address the need of removing aqueous content ftom an invert e~~.~Ãilsion oil-
based drilling ~~~~ido
[IDO1:OI Accordingly, thereexists a need for means to econoniica.lly iricrease
the
OWR while reducing the amount of contamiFiant water present in the fluid
ujith~ut altering the fluld s desired properties. Further, there exists a
lieeÃi to
remove large a.rns~uixts of nOn~~mLil5afied water from an oil-based drilling
fluld. Fu.rther yet, ihere exis-ts a need to remove the emtitslft+ed aqueous
content fr0rn an invert emulsion oil-based drilling fluid.
SUMMARY OF INVENTION
10011_1 In one aspect, the prcsent invention relates to a method for removing
the
aque~~~s content from awellbore fluid. The method may include the stcps of
coiita~~~~~g a wellbore fluid with a water absorbing polyrmera Wherc; the
wel1bore fluid includes an invert emulsion, al:loNvlng the water absorbing
polymer to interact with the wellbore I-luid for a sufficient penod of time so
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that t~~ ~~~~te.r abs0rbi~~~ polymer absorbs at least a porti0ii of the
aqueous
content, and ~~parating the water absorbing polymer containing th~.~ absorbed
water ttoiii the wellbore fluid,
100121 In another aspect, the present invention relates to a method for
removing
the non-c~i-nutsifie~ aqueous cotitent from an invert emulsion wellbore fluid
in
situ. 'rhe i-net-hod may inci~~~e th~~ steps of tietermini~~~ a design limit
of the,
oil-to-water ratio for the wellbore fluid, feeding the wellbore fluid to the
borehole, i-nonitori-ng the oil-to-water ratio of the wellbore tluid, adding a
water absorbing polymer wben the oil-to-water ratio decreases below the
design limit, aiio,.~?ing the water absorbing polymer to interact with tlie
wellbore fluid for a sufficient period of time so that the water absorbing
polymer absorbs sufficie.~t aqueou;~ content to return the oilatoWwater ratio
a~~~te the design limit, and scparat:i~~~ the water absorbi~ig poiymer
containing
th~.a absorbed water from the.wellb~.~re flui.d.
~~~~~~ In another as~~ct; the present %nventa0n relates to a method fOr
aemoving
the emulsified aqtzeous content from a weilbore fluid. The method mayr
include the steps of dete-miiiii~~~ a desired oil-to-water ratio for the exiS-
t~ng
i~~~~~ emulsion weilbore t~~id, addiiig a sufficient aniaunt ~~~~ater
absorbing
polymer tothe exist~tig wellbore tluiÃ~ to adjust the existing oil-to-water
ratio
to the desired oil-to-water ratio, allowing the water absorbing poiyirier to
interact with the existing wellbore :~luid for a s-tiffteient period of time
so that
the water absorbing polymer absorbs siifficient aqueous content to a.4juSt the
existing wellbore fluid to the desired oil-to-water ratio, thereby a-i~ldiaig
ail
adjusted wellbore fla~~~ and separating the water absorbing polymer
containing the absorbed at~~~~~s content frO:m the adjusted wellbore fluid,
100141 Other aspects and acivatitages of the claimed subject matter will be
apparent ~rom ttie following description and the appended cWms;
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Brief Description of the Drawings
~001-ii FIG. 1 shows a graphical representation of the c~~~~irptiOn of fresh
water
over a period of time.
~~~161 FIG. 2 sh~~~~ a graphical representation of the absorption of sea water
oN%er a period of time.
10017] ~ICi. 3 shows a graphical representation of the effect of
~emp~erat.Eire on
sea water absorption over a ~~~~od of time.
[00181 FIG. 4 shows a graphi~kil representation of the ~bs-OrptiO~ of sea
water in
an oil environment over a period of tinie.
[00191 FIG. 5 ~~~~~ a p
,raphic~~ repreS~iiiatioFi of the absOrptis.~~i of sea water in
an oil environment containing an invert emulsifier over a period of time.
100201 FIGn 6 shows a graphical representation of the absorption of sea water
in
ari oil environment cOntainzng an in-v~rt emulsifier and barite over a period
of
ti.~~~
100211 FIG. 7 shows a graphical representation of t~~e absorption of
emulsified
fresh w~~~r over a period of time.
100221 FIG. 8 shows a graphical representation of the absorption ~~ ~inulSiied
brine over a period of time,
(00231 FTG3 9 shows a graphical r~~resentatiOit of the absorption of nonR.
~mtil~ified brine, setting the percent concentration (w/w) against the w<t~~r
activity.
[00241 FIG, 10 shOWs a floW chart for removing aqueous content fr0in an invert
~mWsaon drilling t1.tiid using a water absor~ing polymer.
f 00251 FJGn I1 shows a fle~Nv chart for removing the rion-emuisified aqueous
content fro~n an invert caiiuisic~n drilling flitid when the fluid is in
process.
[0026] FIG. 1;2 shows a flr~Nv chart for removiaig eFnulsi~'~~d aqueous
contelig
from an ~~ivert emulsion drilling fluid usF~g a water ~~sorb~ng, polymer.
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Detaal~~ ~~~cripti0n
[00271 In one aspect, ~~~~~~imejits of ttie inveritioti are generally directed
to a
Tiaethod for removing aqueous content fi~orn an oil based drilling ~luad,
thereby
incr~~~in~ the OW'R. As described ab0ve, dtia=.xng t~~ use of a wellbore
fluid,
water often cc~~t-arrt~nat~s the We] lbor~ fluid so as to ine~ea~~ the total
volume
of ~~e, wc;lfbc~~e -tluid and aI~e-r the OW~, as well as the concentration of
~~lts
or otl~er wellbore additives tr0m their initial, desired concentration.
AccOrdin~ to the embodir~ent~ of tl-te present invention, excess aqtteous
content may be removed froni a wellbore fluid by coiitactin~ the wellbore
fluid with a waÃer absorbing po1yii-~er. Weilbore tItaids that mayb~ used wi~
a Nvater absorbin~ ~~c~l~~mc~r in ~.c~~s~rd~:i~.ce Wit~. the pr~.sent
invention ~~.~:~~
inel.-Li~e any invert emulsion fluids having excess water ~~~at have been
collected fr~n-n a wellbo:re, such as drilling tltzids, completion tluids,
workover
fluids, and drill-in fliiid_~.
100281 In one embodiment of the invention, a method 100 of removing at least
a portion of th:c aqueous content frotn a wellbore tlu:id is depicted in M&
10.
The wellbore fluid. comprises an invert em-uls~on oi1rtbased drilling fluid.
As
stated ki~ove, an invert ei-n-ulsi0n consists of tlixe~, 'ph~~~ an
olekginoii:~
phase, ati aqueous phase, and a finely divided ~~~~le. phase. In the invert
eFiiul~ion oil-based drilling fluid, the discontinuous ~queotis phase is
dispersed in an exteriiaI ore~.~titinuoLiS oleaginous phase with the. aid of
one or
more emalsifiers.
f00291 'Fhe ~.~leaginous c0nfi~~~~~z phase is prefer~~~~~ selected from at
least one
of the follc~wing: inineral oil synthetic 0il, diesel, crude oi~ ~~~ mixtures
Ãhereof, The aqueous discontinuous phase is preferably selected from at least
one of the followingm -fr.~~~i water, sea water, brine, mixture of water and
water
soluble organic c:ompounds, and inixtureS thereof. As kase~ herein, brine
refers to various salts ai~~ salt mixtures dissolved in an aqueous solution. A
brine of t1-ic pres~tit invention may include m~~oNfalent or/and divalent
salts of6
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i~~~rganic or oà gat~ic acids. Preferably, a brine of the present invv;ntioii
includes calc;ium., sodium or potassium ~l-doride; calcium, sodium or
potassium brc~i-nide, potassium or cesium formate diss0lved. in an aqueous
solution.
[00301 Method 100 comprises a contacting step I 10, where, a water absorbing
polymer is coti#.acted with the we~lbore fluido The water absorbing polymer is
preferably a water absorbing crystalline pok~i-tict capable of absorbing at
least
times its own weight in fresh water. Particularly, the water absorbing
polymer may include acrylamide based polymers and copolymers, starch
der~vEttives, and ~~n-i~~aations thereof, as weli as other water absorbilig
polymers knON~,7n in the art.
J0031] 'fhe absorbance capacity of the water absorbing polaa-n-ier~ ~~ay be
expla~~~~ by the matix-like str~icture o~.~ dry water absorbing polymer
p~~icle.
The dry polymer may cOiatain ch~~~~ species wIthin the matrix, suae,b that the
ionization of the polymer will cause the matrix network to open and create
cavities that may absorb water by capillairy action. Water absorbed into the
polymer ma)j be retained by hydrogen bonds that fon-n between the charged
~~eci:es and th~.~ wat(m The actual F-nc:cha~~~sm for water absorb~~ic~ and
retention may kar), based on the structure of a particular water absorbing,
polymer. For example, polyacrylamide, in the dry p~Avdered state, contains a
coiled backbone, lined witl-~ amide grotaps. When exposed to an aqt~~o-Lis
sOtution, th~ ~~ide groups dissociate into negatively charged an-iide iolls;
which nuay repel one aÃ~~tlier along the polyrner chaiii. The repelling amide
ions thereby widen the polymer coils and alic~NA, water to move into contact
with inner amide grO-Laps, further continuing the widening or we11ing of the
~~lymer: Water is retaiii~d within the polymer due to hydrogen bonding
between the water and ttie amide iotis on the potymero Because of the
crcassli.nking that in these water a~;bs0tbang- polymers, the ~~.~ter
absorbing polymers remain iiiso1ubI~ ~n. an aqueoLis sOlutkon.
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100321 Method 100 -further cornprises an interacting step 120, where rh~
'%va~~r
absorbing polymer is allowed to contact the W~~~~ore, fluid for a period of
~ime. T~~e period of ti~ne. should be sufficient so that the water absorbing
polymer absorbs at least a portion of the aqueous fluid froni the in-v~~
emulsion, 'The amount of ~~~~e will vM= depending on the appiicatioii, and
can, be easily ascertained through ~~~~~~~~tafi~,e testiti.g. H0wever,
equilibritam has been obtained between I and three hours, depending on
salinity as well as the state of emtaisification.
100331 Method 100 fiirth~r comprises a separating step 130, wher~~ the water
absorbing polymer containing the absorbed water fromthe w-eilbore fluid is
separated from the wellbore fluid. This can be achieved ghr~~~~~ various
filtration tÃ:ch-niques, including passing the invert ~i-niiisior~ ~~~~lb~~~
~l-uid
containing the water absOrbitig poly~iie~ over appropriate sized shaker
screens
to remov-e ttie swollen water absorbi~~~ polymer. Alt~m, at.irrei4F,
centrifuges or
hydrocylcoties, which wcark- on the basis of size and density difference5, may
atso be used to effectuate separation of the water a:b- sOrbing ptklymer
froxii the
wellbore flWd.
~~~~~~ In another a5pect, eniboc~iments, of the invention are generally
directed.
to a method for adjustiiag the OWR of the invert emulsion wellbc~re, fluid.
T'his may become necessary to remove excess da'.N-Rhole itiflux of water, or
a~ju~~ the OWR of an existingwellbore fluid so it may meet the specifications
of a particular application.
~~~~~~ In one e$nbodirnen#. of the invention, a method 200 for removitig the,
non-esiiuisified aqueous c:ontent during the drilling process is depicted in
Fig.
l I , It may become necessary to remove excess aqueous ~~~~~en. t tilroEighout
the drilling process if, for exanipie, there is an i~~~tLx o~water into the
wellbore or tttere is surface contamination of the weliisor~ fluid. If the
Nvater
portion <~f the invert emulsion wellbore fluid increases, the 'water absorbing
poIyni4r can be added to absorb at least a portion of the aqueous cotiteiit,
thereby increasing the ONVR. The water absorbing pOly~~~i-ier will absorb the
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~~iflux water fi-rst, and then absorb the discontinuous aqueous phase of the
wellbore flttad.
100361 Method 200 con-vpriseS a dQ#.erminin~ step 2 10, NN-bere the design
1irni~ of
the OWR for the invert c~~oulsion xvel:~~ore fluid is determbned. The design
limit is the minimuni OWR the weiTbOr~: fluid. will tolerate without adversely
~~~~~~~~g the rheology, density, and emulsion stability of the well~bo~ ~
tlu~d.
Accc~rding:tv, the design limit Nvill vary dependiia~ ~ipon t~~~ partic~~~~r
application.
~00371 Method 200 .~~artli~r comprises a feeding step 220, where an iuve~
emulsion wellbore t~.Liid is ~e-d to the borehole. '-l'he wellbore fluid is
generally
fed to a boreb0le via nozzles in a drill bit, or other iiietbods already
k.~~~~n in
the art:
[00381 Method 200 ftirth~~ ~~i-npri~~~ a monitoring step 230, q~~~~~~ the OWR
of the wellbore fluid is monitored. Dcte:rn~ination of the OWR can be done
by distilling the ]:iquid part of the drilling fluid in a device called
ritorÃti or
other means known in tlae art. The ideal OWR will vary depending upon the
particular application, as will the design liiai~~ of the wellbore fluida If
the
deteniiined O'WR falls below the design limit OWR, removal of ~~e, cxc~~s
aqueous content becomes necesSarye
[00391 Method 200 ~~.~rtl~er cor~ipri~~s a c0iiÃ,ac:ting step 240, where the i-
nv~~
e-mulsion drilling fluid is, contacted with a water absorbilig pb~y-mer
tb.~ougb:
i-ntrcaducing the watef absorbing polymer to the circulating drilling fluid in
the
weIlbore, 'rhe water absorbing polyiner can be added directly to the active
pit, or ~~~e'":a[er absorbing polymer may be added in the ~~~~~ ~in, c
carrying the
invert eiiiulsiOn weilbore fluid.
[00401 ~etl-iod 200 furt.l-xer comprises ai-i interacting stop 250, where the
water
absorbing polymer interacts with the invert emLilwiun drilling tltii:d for a
sufficic;nt period of time so that the water absorbing polymer absorbs
sufficient aqueous content to .retui'~ the ONN'R above the ~~~~~~ limit. In
one
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etnbodiment; sub-niiit:imetric polymer
granules are added to the wellbore fltiid
aiid ail0wed to continuously circulate within the wellbore. As the poiyx-ner
.~ anu~~s circulate wiib. the welibore fluid, at least a portion of tlae
aqueous
content of the welib0~~ fluid will be absorbed by the polymer granules. As
the polymer 6-raiauies absorb the aqueoLis content, the polymer gTranuies will
begin c~ expand.
[00411 The size of the water absorbiiig polymer is in-.tporttant, as it
affects the
rate of absorption. The smaller the size of the water absorbaiig polymer
granules, the larger the surface area of the ga:rÃiciesV yielding a higher
absorption rate. However, the gruiules sbo-uid not be so sznall that they
negatively inipaci the rheology of the drilling fluid. The rheolo~e~3 of the
iLLrilling fluid may become negatively impacted if the particle size of the
polymer granules become conipara~le to that of the drilling fluid solid
constituents, Le. the weight material and the fluid loss :additxve.
Additionally,
the gTwiuies shoLild not be so small in size that they will pass through the
shak-er screens before they have sWO~~en. Consequentlyt the particle size of
t~ie polymer granules is at least 300 microii.
[00421 Metlioci 200 further comprises a separating step 260, w1i~~~ the water
absorbing polymer coiitaining the absorbed aqueous content is separated irom
the invert emulsion drilling fluid. After the water absorbing polymer b.as bee-
n
allowed to c~~~~~~t the invert emtilsioiz drilling il-uid long enough for at
least a
portion of the aqueous content to be absorbed by the Nvater ahsOfbing
pc~lymer, the water absorbing polymer may removed fr~~-i the invert
~~iiulsiori
drilling fltiid. Tbis, may be done by passing the fluid througb: suitable
sized
shaker :screeiis. Filtration of the aqueous content-bearing water absorbing
polyin~r can be achieved after the water absorbing polymer has swelled
enoEigb to be caught by the sha~~~ screens. However, if the water absorbing
polymer has not swollen sufficientlya the water absorbing polymer will pass
tiir~~gh the si3ak-er screen and cvnta~~~~~ to circulate through the wellbore.
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This allows for continual aqueous content rernoval until all the water
a I bsOrbing polymer swells enough to be re`.o-vYÃ;~ by the shas:er screens.
~~~~~~ ~n another embodiment of the present inveniion, a method 300 for
removing a portion of the emulsified aqueous content of an existing invert
em-uI:~~~~n wellbore I-Iiiid is depicted in Fig. 12. The existing OWR of all.
existing invert emulsion wellbore fluid ca~~ be determined by retort, as
stated
above. In c~nain eircuinS.tances, the existing C~~ of an invert emulsion
wellbore fluid may need to be increased so that the invert emulsion wellbore
~~~id meets ~~~~~iftcations of a. particular ~~~~~catiorze Conseqxaeiitlv, it
would
be necessary to remove part of the discontinuous aqueous phase of the.~~~~~~
emulsion wellbore fluid.
[00441 Method 300 comprises a detenminataon step 3 10, ~~~~re. the desired
OWR is determined. 'rhe desired OWR will vary depending Ãip0-ri a given
application. Factors considered when determining the desired OWR fncltis~e
the fluid densitv, rheology, flitid loss properties and costs.
f00451 Method 300 further comprises an addition step 320; where a sufficient
amount of the water absorbing polymer is added to the existing wetibore fluid
to adjust the existi~~~ OWR. to a desired OWR. In one embodiment, the
existing wellbore fluid is held in storage, and polymer ~~~~~~~ are added to
the emsting wellbore fluid, As previously stated, ~l-ie size of the polymer
granules af~ects the rate of absorption. Because the existing wellbore ~~uid
is
held in storage, and is not actively involved in drilling a welibore, the
amount
of time it takes to adjust the OWR tk) the desired OW'R is not as critical.
Consequently, larger polymer granules are preferred. While larger gr~~~~~s
n~ay be used, ~l-iey should not be so large as to be prematurely filtered
during
separating step 340. Therefore, polymcr granules ~~t-ween 0.3 and 1.0
millimeter are most p~re-i~erred
[00461 Method 300 f~~rther comprises an intera~~~niz step 330, where the
in~~ert
cmulsi0n wellbore fluid interacts with the wat~r absorbing polymer fo.r a
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sufficient period of time for the water absorbing polymer to absorb sufficient
aq-ueous cOtit~~t to adjust the existing O'W'R to the desired OWR. In oite
e~~~odhnent, the i~iveat emulsion WelIhore fÃ-tti~ is moderately agitated for
the
duratic~n of the time period. I'he agitationshould be of au adequate leveI to
distribute the polymer granules unif~~raly throughout the drilling flLtid, Le.
p:~evenÃ:separat.ion due to density difference.
10047.1 Method 300 fi.arther comprises a separating step 340, where the water
absorbing polymer containing the absorbed aqueous %ori-t~nt is separated from
the i~vert emul5ioTi Well.bore fluid. Once the desired OWR is reached,
separation in~.~ ~~ done by passing the invert emulsion wellhor~ fluid through
suitable sized shaker screens.
]0048] EXAMPLES
[0049] The following examples demonstrate the capability of water-swelling
polyrriers to remove water or salt soluti~nfirOm an aqLieoLxs and n0n-a-queaus
liquid environment: Granules of an acryiamide copolymer (POLYSW~LL~,
M-1 WA~~~) were used in all the examples given ~~~~"v. The granules were
rough1y cubic in shape, with approximate size 2-4 mni. These were ground in
a small laboratory Prinder to a 490 of about 400 inicron. Unless oth~nvise
stated, all the tests wc:re carried out in ai~~~ent temperatu-t+e (20-25 T),
[0050] Examples 1-3 are general demonstrations of water absorption capacity
of the polymer. Examples 4-~6 ~~~~eTally show tt~c high capacity of th~
polymer for removing non-emulsified wa.ter 1~~~ a non-aqueous environment
such as an oil-based fluid. This is ai-ialogous to surface c-otiÃaminatio~ or
down hole i~ifltax of water. Examples 7-9 getir>rally illustrate the ability
of the
polyTner, dispersed in an oil phase, to extract Wa~~~fte~m an emulsified
aq-ucot~s phase. This is analogous to treating an existing oil-based fluid in
order to i~~~~~~e its OWR.
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10051] ~xa~ ~ ~~ ~ ~
~0052] One gram ofthÃ> polymer was added to a 250 mL beaker coiit.aining
fresh water and stirred ~~~~ly. The polymer granules were removed by
s~evi-ng and weighed at intervals, then ~~~umed to the ~eaker. Fig. I shows.
the weight gain of the polymer ayai:nst time of interaction bà ~Nveen the
poIy~~~r and the fte5h~~~~ .~~er. The results show that the polymer absorbs
more
than one hundred (100) times i~~ own weight of fresh water in two hours.
[00531 ~xa~nple
[0054] One gram of the polymer was added to a 250 inL beaker containing sea
water ~~id 5tii ~~~ gent1y. The pOlya~~~~ granules v~~er~ removed by saevi.~g
and
weighed at int~rvaisq then returned to t~~ ~eaker. Fig. 2 sho-w~ the weight
gain of the polymer against ~~~~ of interaction between the polymer and the
sea water. The results show that the polymer absorbs more than ten (10)
times its 0~~-n weiglit of s~a. water in tNvo tioursa
[0055] ~~ample :~~.
[0056] Fig. 3 shows t~~~ effect of a thirty (30) degree rise in teitiperature
on ~ea
water absorption. The hig
,h:er temperature does not have a negative effect on
water absorption capacity of the polymer.
100571 ~~~MpL 4o
10058] One gram of polymer was dispersed in a 100 ml1 beaker ofa mineral oil
(EDC 95? 11, Tota1). The mixture was gently stirred for two hours to altow
the polymer surfaces to become fully oilywet. A 50 ~~il., volume of sea water
was then added to the oil phase as the stirrirzg c~~~inLiede The ~~~~~~~~
~ranules were weighed at i~~~ervals. Fig. 4 c-harts the weight of the absorbed
sea water against time. Coiiipari~on with Fig. 2 shows that the presence of
the
oil does in.0t inhibit absorption of sea water by the polymer.
13
CA 02674478 2009-06-30
WO 2008/086385 PCT/US2008/050564
100591 Example 5:
[00601 Two and a half (2.5) grams of an invert emulsifier (VERSACT.~~~~
FL4; M-1 SWACO) was dissolved in 100 mL of mineral oil. On~.~ ~.~arn of
poiym~~r -waS added to the oile Sti~~ing; continued for t~vo hours to altov'r
the
~~~lvr~~~~ surfaces to become fully oiiwwet. A 50 mL volume of sea ivatQt
then added to the oil phase witi~ gentle stizing. The polymer 'granui~s were
weighed at interiais. Fig. 5 shows the Weight of the absorbed sea wat:er
against time. Comparison with Figs. 2~5 shows t~iat the presence of the oil
and en-niisifier does not inhibit ab~orpti~~ of sea water Il}= the polymer. it
should h~.a noted that iugh-shea.r mixing, which is required for fOnning a
stable
eitiuision, was not applied in tfiis test. (i.e. the mixture was stirred
gelitly at
all times)
~~~~~~ ~~ample 6:
[00621 Two and a half (2.5) grams of emulsifier was dissolved in 100 mL of
mineral oil. One hundred eighteen (I 18) grams of barite was added tothe oil
and the i-nixture, was sheared fior thirty (30) niinutes. One ~~~rn of the
polymer was dtds~ed t~.~ the oil-barite suspension and stirring continued for
tw-o
hours. A 50 mL volume of sea water was then added to the suspeai5iÃsn, witb
gentle stirring. The polymer granules were removed at int~-rval~ by sieving
and shaking to enstire that Tnost of the oily suspension was removed from tl-
ie
swollen particles before weilohing. Fig. 6 sh0NN-s the weight of absorbed sea
water ag.a:inst time. Comparison with Figs. 4 and 5 shows ti1at. the preseli~~
of
barite particles reduces Water absoi-ption by the pOlyrner. ~'his may be due
to
coverage of polymer granules with fine particles of barite. Nevertheless, the
~~ly~~er is capable of absorbing ~~veit times its owai weight of sca water iTi
three (3) b:ours,
14
CA 02674478 2009-06-30
WO 2008/086385 PCT/US2008/050564
1005-31 The follssWi~g examples shoNAr the water absorpti.~~i capability of
the
polytiier w-hen the water is preseiit in an emulsified state, which is the
case
with invert ~~n-tilsiOn fluids.
~00641 Exam 1~ ~~
[00651 Two and a half (2.5) grams of emulsifier was dissolved in 100 rn.~ of
mineral oil. A 30.7 mL voluTne of fresh water w-as added to tlie oil and the
mixture was Sut~jÃ;cted to high shear for thirt), (30) minittes using a
Hainzlton
Beach mixer. One Qram of polymer was then added to the eniulsion and the
mixture ~,vas stirred gen#1y. The polymer gTanules were removed at i~~~t-val
and weighed. Fig. 7 shows the w-eight of absorbed fresh water against time.
`I'he polymer readily absorbs ~~sh water, up to fourteen (14) times its own
weight, even uThen the water is i-n an ~mtilsif~e~ state.
~00661 ~~am le 8:
[0067] A 22% (w/w) ca1cluni chloride hrhi~ was made by dissolving 10.9
granis of calciu~~~ chloride (vilficid grade, 83.5% purity) in 30.7 ~~iL of
fresh
water (equivalent Ã~~ a water phasesalinaty of 173,887 mgi'L of chluridc,
ions, a
coznmon s~~lfieFd u~it). Tivs~ and a half (2.5) granis of ~intiisi~'ier was
dissolved in 100 n~ of mineral oil. The 30.7 mL volume of 22% (~.~ /w)
calciLim chloride brine w~ss added to the oil and the mixture was subjJected
to
high shear for ~irty (30) minutes using a I-Tainilton Beach mixer. One gram
ofp~lym~r was then added to the emulsion and the mixture và as stirred
ge:~~ly.
The polymer granules we.r~ ~emoved at interval and we~~lied. Fig. 8 Show.~
~~e, weight of absorbed brine against time. This is the worst case scenario
for
water absorption as bOtl-i salinity and eiiaulsification reduce absorption of
water, by the palymer. ~evertheless, the polymer is cap~~~~ of absorbing
more than three t~racs its ~~im weight of hra.nefrom a c0ncei-itrat~~
emulsified
brine phase.
[00681 Example 9:
CA 02674478 2009-06-30
WO 2008/086385 PCT/US2008/050564
100691 A t~~t was conducted to determine whether it was water or brine tlaat
was absorbed by the polymer. 'I`hree hundred (300) gr-ams of a 22% (Wlw)
so1uCtoii of calcium chloride was prepared as described in Example 8. The
water activity of this solution was measured by a Novasina Water Activity
Meter (Model niSlraW) to be 0.796 at 22.5 'C. Fifleen (15) grams of the
polymer was added to the brine and mixed by gentle sttrring, After eight
hours, the polymer granules we-re removed by sieving, and subsequently
weighed. A weight gain of 7'7a9 grain w-as registered. Tbe Water activity of
the remaining brine was measured to ~e more or less unchanged, 0.790 at 24.0
QCa
100701 Fig. 9 shows the percent concentration (Nk7/"W) against water activity;
If
the weight gain of the polymer was due to absorption of pure water, r='~.ther
ihaii brine sc~lution., then the salt concentration of the remaining brill_e
would
have increased to 29.9%, ec~~ivalenà to a water activity of about 0.64, as
shmxn in Fig. 9. As mentioned above, the measured w-ater activity of the
remaining brine w-a5 0.79. Therefore, it is concluded that the polymer absorbs
the salt solution rather than pLire water.
~007,11 While the claimed su~ject matter has been described with respect to a
limited number of embodiments, those skilled in the art, having benefit of
this
discIosu.re, will appreciate that other e~~~~~~iments can be devised which do
not depart from the scope of the claimed subject matter as disclc.~s~d herein.
Accordingly, the scope of the claimed subject matter should be limited oiit~
by the attached cIaimso
1.6
