Note: Descriptions are shown in the official language in which they were submitted.
~O 92/07919 2 ~ ~ ~ G O ~ PCTtGB91/01944
aE~ a ~rrx~_~D
m is invention relates to a ~ Ltive~ for drillirrJ fluLd~.
Drilliny fluids are clrculat~l d~wn ~he w~llhor~ beln~
drilled during well drilling operations. 'l~e fluid i~ usually pu~p~d
down the ixside of the ~rillpipe and then passes through the drill
bit into the wellbore. qhe fl~ returns to the surfa oe throu3h the
annulus defined ketween the exterior of *he drillpipe an~ the
wellbore. The fluid is t~len reoovered, processed and reused.
Drilling fluids are desirabls in order to lubricate the drill
bit, to cool the drill bit, and to remove rock cuttings generated.
Ihe physical properties of the drilling fluid (su~h as
viscosity/ density, salinity and filtrate loss) can be modified as
One problem that occurs with water based drilling fluids is
hvdration of the rock being drilled. Ihis probl~m is particularly
acute when the ro~k includes clays and s~les.
Clays and shales display a great ~ffinity for water.
Absorption of water leads to swelling ol the clay or shale and the
resulting stresses can le~d to f ~lure. ~LS, when ~he rock has been
hydrated it can be subject to strlcdhr~iL ~ailure, and can col ~ e
into ~he wellbore. This ca~P~ wellbore ~ nsion, and can cause the
dril7pipe to beccme stuck.
O~e solution to this problem inNolve~ thQ use o~ oll based
drilling ~lui~s, which are usuaLLy ~ormiLated with m~l~n~L oil3.
Althou3h thse ~luids gen~Lly co ~ n water, it is tightly
emulsifisd using pcwe~i~iL sur~actants. Such ~luids are oubctan*ially
mert to hydratable rocks.
Su~h oil based drilling fluids are expensive kut have been
use~ extRnsively, particularly in the Morth Sea area. However, dNe
~o environmental problems they are being used less extensively.
Another solution to the problem involvcs the use of water
bQscd drilling fluids ~hidh Lnocrpcrate additives havlnq sur~ace
active properties; such additive~ ar~ eorbed onto the rock, rçducing
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W O 92/07919 2 0 3 ~ PCT/GB91/019~4 f
the access of water, and thereb~ reducing the rate of hydration.
Anionic, cationic and nonionic matexials ~re used, because
dif~erence parts of a rock struc~ure show di~ere~t a~inities to
differe~t ionic charg~. s
EXamples of known additives ~or reducing hydration include:
potassium chloride, partially hydrolysed polyacrylamides (PffPA);
gilsonite; pol~glycerols; carbcxymethyloe llulose deriva~ives, such as
polyanionic cellulose; calcium chloride; and ~cdium silicate.
Potassium chloride combined with PHPA has been widely used,
despite ~he high c06ts and the dif~iculty in using the materials.
Cationic Materials can b~ highly e~fective but tend to ~e
incompa~ible with other additives (mostly anionic) u~3d in water
based drilling fluids.
Ihere exists a need for an effective addi~ive for use with
water kased drilllng fluids, which additive is campatible with the
other co~po~ents of dr;l-ing ~luids.
~cocdin~ to one a~ of the present invention thQre is
pravided an additiv~ fc~-a drilling fluidl, n~rising a ~5itiall
which is at least dispersible in said drilling fluid at a~bient
temper~tures, and has a solubility in said drilling fluid at
drilling temperatures which is lo~er th~n the solubility at said
ambient t~mperatures, and said OO~pO6itiOIl, when dispersed in water,
has a higher affinity than water for the sur~ace o~ a rock b~mg
drilled.
- ~.Advantageously said co~positio.n is sub6tan¢ially insoluble in
said drilling fluid at said drilling temperatures; and is soluble at
ambient t ~ tures. A~bient te~pexatures wculd ge~erally be ~rom 0 to
50& typically 0 to 30. qhe upper end o~ th~ range is only likely to
be reache~ in desert areas.
Drilling temperatures may be ~ g from ambi~.L up to
200 & or mcre. A typical "kottom hole" temperature in the North Sea
w~uld be abcut ~20C.
qh~s, the additive a~cordlng to the invention wilL readily
~mix with the fluid at ambient tenperatures, but will cc~e out o~ ~
solution at drilling te~peratures and attach itsel~ to the rock,
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'.` ~O 92/07919 2 ~ 9 J ~ !J ~ PCT/CB91/01944
thereby protectiny the rock frcm hydrat:ion by water in th~ drilling
fluid.
Preferably the comçosition oompri~es a polym~r con~aining
aIkylene oxide repeat mg units.
It is particularly preferred that the alkylene oxide inclu~s
ethylene oxlde and/or propylene oxide.
~ he poly~er may ahvan~ageously be selected from the group
consisting of:
An ethylene oxide/prcpylene oxide blocX copolymer; a
` polyalkylene cxide-modified polymethyl siloxane; a polyalkylene
oxide modi~ied polyamine, alcohol or glycerine; an~ polyprcpylene
glyool.
It is preferable that the polymer conta m s S to 75 wk%
ethylene oxide and 25 to 95 wt% prcpylene oxide, more pre~erably 5
to 50 wt% e~hylene o~ide and 50 to 95 wt% prcpylene oKide.
Desirably the molecular weight of the polymer is g~eater than
1000.
A paxticularly effective polyalky].ene oxide n~dified diamine
is available, under the registered trade mark SEPAEASE 31. Ihis
material is available frcm BASF.
; A particularly effe~tive polyalkylene cxide n~dified alcc~ol
is available under the registered trade! mark BP 75W 18000. Ihis
material is available LLam BP and is disclosed in a BP publication
relatinq t~ ERE~X polyalkylene glyucol flt~ an~ lubricants.
Some of thQ a~ditives according to the invention also provide
excellent lubricity characteristics, particularly the ethylene
oxide/prcQylene oxide block copolymers.
~. ~ to ansthcr aspect of the ~ on there i~
provid2d the use in thQ wellbore drilling o~ a 3LL~tum, o~ a
saturated or unsaturated aqueous 601ution o~ a s=bctonce whlch
exhibits a critical solution temperature between ambient temperature
and the service te~perature at the stratum.
The ~ub~tanD~ may cumpri~e an additive having any oambination
of ~he ~eatures o~ the ~ tive descr~bed above.
The invention will n~l be further d~scrib3d with reference to
the follawing e3s~pl~;.
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W 0 92/07919 2 0 9 S 6 0 ~ PC~/CB9l/~l')44 ,.-~
CcmparatiVe E~a~E~e~-l
A test was devised to establi.sh a relat.ive measure o~ shale
stabilisation performance ~or varicus dr:Llling ~lul~L~ he t~st
inv~lved static storage of 250 - 1000 micron sLeved raw be~tonite
~are in the fluid un~er test ~or 16 hour.s at ~0C. ~terwards the
be~tonite was washed with a solution o~ 10% potassium chloride in
tap water, and then resieved. Ihe test was cæried out twioe f~ar
each flllid (tes* A and test B), and the rr~sults are summ~rlsed in
Table 1.
Example 1
Ihe test o~ comparative e ~ le 1 was carried GUt with a
drilling fluid oonsisting of seawater mixed with 1% ky weight of a
~luid acGording to the present i~vention. The test was carried GUt
twioe for each fluid (test C and test D) and the results are
summarised in qable 2.
EXample 2
Ihe test of example 1 was repeat~d using 5% ~y weight of
~dlitive, instead of 1%. The test was ca~ried out twi oe for each
~luid t~est E and test F) and the results are summaris~d in Table 3.
In co~çaratiYe example l~ and examples 1 and 2, swelling
~ to particle ~;~integration and weight ln~, althsu3h in scme
cases aksorbance can lead to a weight ~ e. The results from
examples 1 and 2 ~hcw that use o~ 5 wt% of the additive accGrding tD
the i~vention, rather than 1 wt%, may lead to a siqnificant
~ impccvem=rt in inhibition only wlth certain additions and that
: ~- performance may be cpkimized by suitable material selection.
~ - Cbnparative Ex3m~le 2
- : - ~ ative example 3 ~a5 repeated for three prior art
A~;tiv~s, using a dif~erent bentonite ore part~le slze o~ 1.0 to
2.0 mm~
The te5t5 were repeated twice for each fluid (tests G an~ H),
and the result5 are summæi~ed in Table 4.
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~ 92/07919 2 ~ 9 ~ ~ Q ~ PCI'/C-B91/01~44
Comparative example 2 was repeated, each drilling fluid al~o
be m g mixed with an additiv~ aocording to the invention, as well as
the priar art additive.
The tests were repeated twice 2cr each 21uid ~tests I and J),
and the results are summarised in Table 5.
A ccmparison of Table 5 wi~h Table 4 shows that the addition
of additives according to the invention to the drilling ~luid c~n
cause a significan~ reduction in weight lo~s, even when the drilling
fluid already contains other additives.
T~BLE 1~ RÆsults of Ccmparative ExamPle 1
TEgr A T~ B
~ g6 Weiqht C~ar~e g6 W~iaht ~e
Seawate~r. -25. 4 -26 . 2
Ben~cnite/PAC (polyanionic
oe llulo6e)/Seawater. -23.5 -24.4
Oil ba~e mud (low aromatic
mineral oil). ~5.9 +4.3
Xanthan gum salt saturated
(Sodiurn *~laride) . -6 . 5 -6 . 8
PAC/35ppD P~t~ssium chl~ide/
Seawa~. -8 . 4 -9 . 7
20~ H~100 (Hydrafluids
polyglycer~ls)/Seawater.+7.5 -~9.6
5% ~E100 -25.0 -2~.5
1% ~E100 -30.0 -32.0
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W O 92/07919 2 ~ 9 5 6 0 ~ PC~/GB91/~1944 ~--~
~BLE 2: Resul~s o~ E~@~ElQl
TES~ C IESr D
ADDrTIVE ~ igh~ t-k~gLe 3~r~gh~_Ç$~yge
Sepabase A31. -15.9 -13.3
Silwet ~7500. -g.4 -13.5
BP 75 W 18000. -9.2 -1~.5
PE 3100. -2.6 -9.2
30 C 05. -10.4 -12.2
Silwet L 7001. -6.3
P400 -17.4 -1~.6
: l~E1E 3: RRsults o~ E~ample 2
ADDITTVE TEST E IEST F
; % Weiqht Chanae % Weioht Chanae
Sepabase A31 + 9.4 +10.0
Silwet L7500 ~40.4 ~49.2
BP 75 W 18000 -1.8 -1.3
PE 3100 -7.0 -11.4
30C05 -9.8 -10.6
SILWEr L7001 +12.0 ~15.5
p400 -13.3 -13.9
I~KLE 4: Results o~ comParative Example 2
TESr G ~EST H
FIUID~ Weioht Chanqe 3 ~ e
Seawater. -83.0 -81.0
Ebntonite/PA~/seawater. -64.0 -60.0
Xanthan gum/6eawatcr. -34.0 -35,0
-- NO 92~07919 2 ~ 9 .~ ~ O a PCT/(JB91/01944
l~BIE 5: ~esults of Examp].e 3
TESr I TEST J
FLUID % Weiqht Chanqe% Wbi~ht Chanqe
As Eentonite/PAC/seawater
In comparative example 2
+ 5% PE 310 -29.0 -ll.0
As Bentonite/PAC/ssawater
In comparative example 2
~ 5% Silwet 720. -2.0 o.o
As a~chan g~n/seawa~
In compara~ive example 2
+ 2.8% Sil~et 720. -l2.O -6.0
As Xa~than gum/seawater
In oomparative example 2
+ 2.2% PE 3100. -16.0 -~16.
