Note: Descriptions are shown in the official language in which they were submitted.
CA 02302731 2000-03-08
WO 99/14286 PCT/EP98/05718
Electrically Conductive Non-Aqueous Wellhore Fluids
This invention relates to non-aqueous wellbore fluids and in particular
concerns wellbore
s fluids which are electrically conductive. The invention also relates to the
use of said wellbore
fluids for drilling fluids or completing fluids for subterranean wells such as
for instance oil
and gas wells.
In the process of rotary drilling a well, a drilling fluid or mud is
circulated down the rotating
drill pipe, through the bit, and up the annular space between the pipe and the
formation or
io steel casing, to the surface. The drilling fluid performs different
functions such as removal of
cuttings from the bottom of the hole to the surface, to suspend cuttings and
weighting
material ~ when the circulation is interrupted, control subsurface pressure,
isolate the fluids
from the formation by providing sufficient hydrostatic pressure to prevent the
ingress of
formation fluids into the wellbore, cool and lubricate the drill string and
bit, maximise
Is penetration rate etc. An important objective in drilling a well is also to
secure the maximum
amount of information about the type of formations being penetrated and the
type of fluids or
gases in the formation. This information is obtained by analysing the cuttings
and by
electrical logging technology and by the use of various downhole logging
techniques,
including electrical measurements.
2o The required functions can be achieved by a wide range of fluids composed
of various
combinations of solids, liquids and gases and classified according to the
constitution of the
continuous~phase mainly in two groupings : aqueous (water-based) drilling
fluids, and non-
aqueous (mineral oil or synthetic-base) drilling fluids, commonly ' oil-base
fluids'.
Water-based fluids constitute the most commonly used drilling fluid type. The
aqueous phase
zs is made of fresh water or, more often, of a brine. As discontinuous phase,
they may contain
gases, water-immiscible fluids such as diesel oil to form an oil-in-water
emulsion and solids
including clays and weighting material such as barite. The properties are
typically controlled
by the addition of clay minerals, polymers and surfactants.
In drilling water-sensitive zones such as reactive shales, production
formations or where
3o bottom hole temperature conditions are severe or where corrosion is a major
problem, oil-
based drilling fluids are preferred. The continuous phase is a mineral or
synthetic oil and
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- 2
commonly contains water or brine as discontinuous phase to form a water-in-oil
emulsion or
invert emulsion. The solid phase is essentially similar to that of water-based
fluids and these
fluids too contain several additives for the control of density, rheology and
fluid loss. The
invert emulsion is formed and stabilised with the aid of one or more specially
selected
s emulsifiers.
Although oil-based drilling fluids are more expensive than water-based muds,
it is on the
basis of the added operational advantage and superior technical performance of
the oil-based
fluids that these are often used for the drilling operations.
An area where oil-based muds have been at a technical disadvantage, because of
their very
low electrical conductivity, is in electrical well-logging. Various logging
and imaging
operations are performed during the drilling operation, for example while
drilling in the
reservoir region of an oil/gas well in order to determine the type of
formation and the
material therein. Such information may be used to optimally locate the pay
zone, i.e. where
the reservoir is perforated in order to allow the inflow of hydrocarbons to
the wellbore.
is ~ Some logging tools work on the basis of a resistivity contrast between
the fluid in the
wellbore (drilling fluid) and that already in the formation. These are known
as resistivity
logging tools. Briefly, alternating current flows through the formation
between two
electrodes. Thus, the fluids in the path of the electric current are the
formation fluids and the
fluid which has penetrated the formation by way of filtration. The filtercake
and filtrate
2o result from filtration of the mud over a permeable medium (such as
formation rock) under
differential pressure.
Another example where fluid conductivity plays an important part in the
drilling operation is
in directional drilling where signals produced at the drill assembly have to
be transmitted
through an electrically conductive medium to the control unit and/or mud
telemetry unit
2s further back on the drill string.
At present the use of resistivity logging tools is limited mainly to cases
where a water-based
drilling fluid is used for the drilling operation (the very low conductivity
of the base-oil in
the case of oil/synthetic-base muds precludes the use of resistivity tools in
such fluids).
Although the brine dispersed in the oil phase is electrically conductive, the
discontinuous
3o nature of the droplets prevents the flow of electricity. Indeed, the
inability of these
emulsions to conduct electricity (until a very high potential difference is
applied) is used as a
standard test of emulsion stability. To that extent it is worth bearing in
mind that the
CA 02302731 2000-03-08
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- 3
electrical conductivity k of the oil base is typically in the range 10'6 to 5
x 10-2 uS.rri 1 at a
frequency of 1 kHz while an electrical conductivity of not less than 10 pS.m-I
and preferably
of no less than 103pS.rn'~ is desirable for electrical logging operations. So
there is a need to
increase the electrical conductivity of the fluid by a factor in the order of
1(~ to 107.
s A few attempts to make oil-based drilling fluids electrically conductive for
the purpose of
electrical logging have been reported though none of them has been a
commercial success.
U.S. Patent No.2,542,020, U.S. Patent No.2,552,775, U.S. Patent No.2,573,961,
U.S.
Patent No. 2,696,468 and U.S. Patent No. 2,739,120, all to Fischer, disclose
soap-stabilised
oil-based fluids comprising an alkalinerearth metal base dissolved in up to
10% by weight
io water. Fischer claims to reduce the electrical resistivity to below 500 ohm-
m which
corresponds to an increase of conductivity to x > 2000 ~S m ~. However, those
fluids happen
to be very sensitive to contaminants and greater amounts of water lead to
unacceptable
increase of the fluid loss. In essence these fluids relied on the residual or
added water content
to dissolve the salts/surfactants. Moreover, the continuous oil phase fails to
exhibit any
~s increase of its electrical conductivity and there is no reference to what
happens to the filtrate
which under optimum conditions is made up essentially of the continuous oil
phase.
Twenty five years later; U.S. Patent 4, 012,329 disclosed an oil-external
micro-emulsion
made with sodium petroleum sulfonate and reported of resistivity < 1 ohm-m (x
> 1 S m 1).
In such a micro-emulsion, the sodium petroleum sulfonate forms micelles that
contain water
2o and the clay so that the clay has to be added as a dispersion in water and
cannot be added as
dry powder. It should be also emphasised that a micro-emulsion is distinctly
different from a
standard emulsion, being thermodynamically stable, smaller in size, higher in
surface to
volume ratio and forming both filtercakes and fluid filtrate of a different
nature. Obtaining
the necessary combination of bulk properties and non-damaging rock
interactions is more
2s difficult than for a standard direct or invert emulsion fluid, and such
fluids are not generally
favoured for drilling oil wells.
Although the Prior Art contains formulations for making oil-based drilling
fluid conductive,
the methods so described adversely affect other mud properties, another reason
why none
have been successfully commercialised. Further, the Frior Art only addresses
the problem of
so increasing the conductivity of the entire fluid but fails to teach any
drilling fluid that exhibits
a good conductivity of the oil phase making thus also a conductive filtrate
which is free of
solids and emulsion droplets.
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The aim of this invention is thus to provide a wellbore fluid whose continuous
phase is
non-aqueous and exhibits an electrical conductivity well above the
conductivity of organic
liquids known to those skilled in the art to be suitable as the 'liquid phase
of conventional
non-aqueous based wellbore fluids.
s To this end, the invention provides a wellbore fluid having a non-aqueous
continuous phase
comprising a polar organic liquid (POL) component that exhibits a dielectric
constant of at
least about 5.0, and preferably of at least 10, and a Hildebrand solubility
parameter of at least
about 17 (J cm'3)'~Z at 20 °C.
The Hildebrand solubility parameter b is a measure of solvent power and is
defined as the
~o square root of the cohesive energy density of a compound, that is the
energy required to
break the attractive forces between molecules of 1 cm3 of material at a
certain temperature T.
This energy is related to the molar heat of vaporisation DHm at this
temperature, the work
needed to expand the volume of the system from the liquid to the vapour phase
RT and the
molar volume of the solvent Vm according to the following formula : 8 - ~ V RT
in
m
is which R is the gas constant and T the temperature in °K. When
neglecting the RT term, the
Hildebrand solubility parameter can be roughly expressed as the square root of
the product of
the density d and the heat of vaporisation aH (OHm = OH x molecular weight.):
~- AH.d .
Said polar organic liquid POL component may be selected from the class
including but not
20 limited to alcohols, phenols, glycols, polyalkylene glycols, mono (alkyl or
aryl) ethers of
glycols, mono (alkyl or aryl) ethers of polyalkylene glycols, monoalkanoate
esters of glycols,
monoalkanoate esters of polyalkylene glycols, ketones possessing also hydroxyl
group(s),
diketones and polyketones.
The required dielectric and solubility properties can be also achieved with
aprotic solvents
2s such as ketones; nitriles; di(alkyl or aryl) ethers of polyalkylene
glycols; dialkanoate esters of
polyalkylene glycols; cyclic polyethers; N-(alkyl or cycloalkyl)-2-
pyrrolidones, N-alkyl
piperidones; N,N-dialkyl alkanoamides; N, N, N', N'-tetra alkyl ureas;
dialkylsulphoxides;
pyridine and alkylpyridines; hexaalkylphosphoric triamides; 1,3-dirnethyl-2-
imidazolidinone,
nitroalkanes, nitro-compounds of aromatic hydrocarbons, sulfolane,
butyrolactone, and
3o propylene carbonate.
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The polar organic liquid component that exhibits a dielectric constant of at
least about 5 and
a Hildebrand solubility of at least about 17 (J crri 3)'n at 20 °C may
be used,as part or all of
the organic liquid phase of a wellbore fluid to substantially increase the
electrical
conductivity whilst maintaining the expected performance advantages of oil-
based wellbore
s fluids.
Oils or other organic liquids known to be suitable as the continuous liquid
phase of wellbore
fluids, may be used in admixture with the POL component of this invention.
This generally
includes any water immiscible organic liquid (OL) known to those skilled in
the art to be
suitable as the liquid phase of non-aqueous based wellbore fluids (such
liquids typically
io exhibiting electrical conductivity in the range 1.0 x 10'~ to 1.0 x 10-2
p.S m' at a frequency of
1 kHz).
It has further been found that certain inorganic salts, organic bases,
quaternary ammonium
salts or hydroxides (the dissolved component, DC), display su~cient solubility
(and current
carrying abilities) in POL, OL or in mixtures of liquid (POL) and liquid (OL),
that the
~s electrical conductivity of the mixture is greatly improved. Therefore, in
this instance the use
of liquid (POL) may not be necessary.
It is further found that when the polar organic liquid POL is used as part or
all of the organic
liquid, water can dissolve to some extent and increase electrical conductivity
substantially.
Generally, the best results are obtained from a combination of (POL) and (DC),
either alone
20 or in admixture with (OL). In any case, the liquid phase is characterised
by exhibiting an
electrical conductivity of not less than 10 p,S ni'. This is an increase of at
least 104 fold over
the conductivity of conventional organic liquids used as the wellbore fluid
continuous phase.
For convenience, any of the above combinations of (POL), (OL) and (DC) are
designated
hereafter as NBL (Novel Base Liquid).
2s Thus, the continuous liquid phase according to the present invention may be
(i) entirely (POL)
(ii) 1 to 99.9% by volume of (POL) + 99 to 0.1 % by volume (OL)
(iii) 50 to 99.5% by volume of (POL) + 50 to 0.5% by volume (DC)
(iv)50 to 99.5% by volume of (OL) + 50 to 0.5°~o by volume (DC}
30 (v) 1 to 98.5°!o by volume (POL) + 1 to 98.5% by volume (OL) + 0.5
to 50% by
volume (DC).
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6
The liquid phase exhibits an electrical conductivity of not less than 10
pS.m'' at 1 kHz.
The most important attribute of this invention is that the electrical
conductivity of the fluid is
increased by a factor of the order of 104 to 107. This allows for the first
time the successful
application of many electrical logging techniques and the transmission of
electrical telemetry
s signals when organic liquid-based wellbore fluids fill the borehole.
In this invention it has been found that for the first time electrically
conductive, organic
liquid-based drilling fluids can be provided which maintain the performance
advantages
expected from known oil-based (or synthetic organic liquid-based) drilling
fluids. Therefore,
the fluids of this invention minimise adverse interactions with drilled rock
formation, such as
io clay formation swelling or dispersion, hole collapse, or the undesirable
dissolution of
underground salt formations. They also provide the performance advantages
expected from
oil-based fluids with regard to enhanced lubricity, reduced differential
sticking of drill pipe,
and good stability at high temperatures.
Optionally, as in conventional organic based weLlbore fluids, a discontinuous
liquid phase
is such as water or a brine may be added together with one or more emulsifiers
to form a water-
in-NBL emulsion wherein the discontinuous phase is present at up to 70% by
volume of the
emulsion.
The electrical conductivity of the wellbore fluid based on NBL, and that of
its filter cake
formed on permeable rock formations, may be further enhanced by dispersing in
the wellbore
2o fluid finely divided particles of an electrically conducting solid which is
insoluble in the
NBL or the water (or brine) phase. These particles may comprise of (but not be
limited to)
metals, carbon in the form of carbon fibre or graphite, metal coated carbon
fibre or graphite,
conductive polymers such as polypyrrole, polyaniline, or organometallic
phthalocyanines. It
is preferred that the solid particles are of very small particle size (in
order not to be removed
2s by solids control equipment), and exhibit an anisotropic particle shape
such as needles,
fibres, flakes or platelet shaped particles. Such shapes minimise the volume
fraction at
which the particles can form a connecting, percolating, conductive structure
with each other
and/or the dispersed, conductive emulsion phase.
In order to provide other properties required from wellbore fluids, the
wellbore fluids of this
3o invention may further contain any known weLlbore fluid additives such as
clay, organoclay,
or polymeric viscosiflers, filtration reducers such as Lignite derivatives,
asphalts, asphaltites
or polymers swollen by the NBL, weighting agents such as finely divided
barytes or
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hematite, lubricating additives, or any other functional additive known to
those skilled in -
the art. These additives aim to provide a drilling mud that has the following
characteristics
~ be fluid and produce affordable pressure drop in surface pipes and drill
string
~ have a yield stress suitable for supporting/transporting mud solids and
drill cuttings
s ~ be chemically, thermally and mechanically stable
~ provide hole stability
~ provide good lubricity
~ prevent excessive fluid loss to the formation
The electrically conductive non-aqueous base of the present invention and the
use thereof in
io drilling fluids is further illustrated.
The Polar Organic Liquid Component
The polar organic liquid POL component of the present invention exhibits a
dielectric
constant of at least about 5.0, and preferably of at least 10, and a
Hildebrand solubility
~s parameter of at least about 17 (J cm 3)~~ at 20 °C.
Polar organic liquids that exhibit low water-miscibility and higher oil-
miscibility are
generally preferred.
Said polar organic liquid POL may be compounds comprising at least one
hydroxyl group
selected for example from the following list
20 ~ aliphatic and -alicyclic alcohols of carbon numbers CS-Coo such as n-
pentanol,
cyclohexanol, n-octanol, 2-ethylhexanol, and n-decanol;
~ phenols such as ortho-, meta-, or para-cresol;
~ glycols such as 1,3-butane diol, 1,4-butane diol, 2-ethylhexane-I,3-diol;
~ polyalkylene glycols such as polypropylene glycols of molecular weight above
2s about 1000 (higher molecular weight leads to a oil-miscibility and lower
water-
miscibility), polybutylene glycols, polytetrahydrofuran, polyalkylene glycols
or
copolymers of ethylene oxide and/or propylene oxide and/or butylene oxide
initiated by any hydroxylic or amino-functional moiety wherein the
polyalkylene
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_ 8
glycol or copolymer is further characterised by exhibiting a cloud point (at 1
%
concentration in water) of less than about 10 °C;
~ mono-alkyl or mono-aryl ethers of glycols or polyalkylene glycols such as
ethylene glycol monobutyl ether, diethylene glycol monobutyl ether,
dipropylene
s glycol monomethyl ether, tripropylene glycol monomethyl ether, propylene
glycol
monobutyl ether, dipropylene glycol monobutyl ether, tripropylene glycol
monobutyl ether, propylene glycol phenyl ether, dipropylene glycol phenyl
ether;
~ diacetone alcohol (4-hydroxy-4-methyl-1,2-pentanone); acetylacetone;
acetonylacetone and polyketones such as the copolymer of ethylene and carbon
to monoxide.
Another class of suitable compounds includes aprotic solvents having no proton
that can be
donated to a solute such as
~ methylisobutyl ketone, cyclohexanone, isophorone;
~ dialkyl ethers of polyethylene glycols such as the dimethyl ethers of
oligomers of
is ethylene glycol, the dimethyl ethers of polyethylene glycols such as PEG
400 or
PEG 600 or PEG 1000, the dimethyl ethers of oligomers of propylene glycol or
of
polypropylene glycols;
~ cyclic polyethers such as 1,4,7,10,13,16-hexaoxacyclooctadecane ([ I 8]
Crown-6);
~ N-alkyl-2-pyrrolidones wherein the alkyl is of carbon number Cl-C,2, such as
N
2o methyl-2-pyrrolidone, N-cyclohexyl-2-pyrrolidone, N-octyl-2-pyrrolidone, N
dodecyl-2-pyrrolidone;
~ N-methylpiperidone;
~ N,N-dialkyl alkanoamides such as dimethylformamide, dimethylacetamide, and
higher homologues such as N,N-dimethyloctanoamide and N,N
2s dimethyloleamide;
~ N,N,N',N'-tetramethylurea; dimethylsulphoxide; hexamethyl phosphoric
triamide; 1,3-dimethyl-2-imidazolidinone; nitromethane or nitroethane;
nitrobenzene; tetramethylene sulphone; ~-butyrolactone; and propylene
carbonate.
The relationship between the relative permittivity, Er, thought to be measured
at 10 kHz (for
3o pure liquid the dielectric constant varies only at very high frequencies,
i.e. 105 Hz or higher)
and 20 °C) and the Hildebrand solubility parameter is shown in the
following tables I and II.
Dielectric constant is the permittivity of the substance divided by the
permittivity of vacuum.
CA 02302731 2000-03-08
WO 99!14286 PCT/EP98l05718
_ 9
Table I provides examples of material suitable for the present invention while
table II shows
examples of non-acceptable materials. To this aspect, it is worth noting that
SHELLSOL
D70, a product available from Shell Chemical Co-UK, may be considered as a
typical
mineral oil while the butyl oleate is a typical ester.
TABLE I Solubility
T a Com ound Relative Parameter
YP P
rmittivit (J cm s)vz
E,.
Alcohols Methanol 31.2 29.7
Propan-2-of 18.6 23.5
1-pentanol I 3.9 22.3
Diacetone alcohol 18.2 18.9
n-octanol 10.3 21
Phenols o-cresol 11.5 27.1
m-cresol 11.8 27.1
-cresol 9.9 27.1
Aprotics Dimethylformamide (DMF~ 36.7 24.9
Dimethylacetarnide (DMAC} 37.8 22.1
N-methyl -2-pyrrolidone (NMP) 32 23.1
N-octyl-2-pyrrolidone 18.9
N-dodecyI-2-pyrrolidone I 8.2
Dimethylsulfoxide (DMS) 48.9 24.5
1,3-dimethyl-imidazolidinone 37.6 (IMHz
Tetrahydrothiophene 1,1-dioxide43.3
(sulfoiane or tetramethylene-sulfone)
Propylene Carbonate 64.92 27.2
Hexamethylphosphoric triamide 29.3
O = P [N(CH3)2]3
Tetramethylurea 23
Nitrobenzene 35.7
Ketone-typeDiacetone alcohol (4-hydroxy-4-methyl-2- 18.9
compounds pentanone)
Acetyl acetone 25
Methyl isobutyl ketone 13.1 17.2
Isophorone 19.2
C clohexanone 18.3 20.3
Glycols 1,2 propylene glycol 32 25.8
1,3 butanediol 23.7
Hexylene glycol (2-methyl-2,4-7.7 23.1
ntanediol)
Ethers Ethylene glycol monobutylether9.4 18.4
(EGMBE)
Dipropylene glycol mono- methyl9 19.3
ether
Eth lene 1 col mono- bu 1 ether9.4 18.4
s
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TABLE II Solubility '
Relative Parameter
Compound rmittivit (J cm ~~
~
n-pentane 1.84
n-hexane 14.87
SHELLSOL D70(Iike mineral oil) 2.15 15.5
n-butyl acetate 5.1 17.6
Butyl oleate(like typical ester)4
Benzene 2.28 18.7
The Organic Liquid Component
The high-resistivity OL component can be crude oil, hydrocarbon refined
fractions from
crude oil such as diesel fuel or mineral oil, synthetic hydrocarbons such as n-
parafflns, alpha-
s olefins, internal olefins, and poly-alphaolefins; synthetic liquids such as
dialkyl ethers, alkyl
alkanoate esters, acetals; and natural oils such as triglycerides including
rape-seed oil,
sunflower oil and mixtures thereof. Low toxicity and highly biodegradable oils
will be
generally preferred especially for offshore drilling.
The OL component may be present at up to 99.5% by volume of the NBL but
formulations
~o comprising up to 95% generally provides the better results.
The Dissolved Component.
The dissolved component DC is a conductivity enhancing component. It has to
display
is sufficient solubility and current carrying abilities in the POL, the OL or
the mixture of POL
and OL. It has been found that different types of materials may be used
~ water if POL is used as part of the NBL
~ some inorganic salts
~ some organic bases
~ quaternary ammonium salts or hydroxides
CA 02302731 2000-03-08
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11
Inorganic salts _
Suitable inorganic salts (including metal salts of partially organic acids
such as
methanesulphonic acid, toluenesulphonic acid) are characterised in that the
anion of the salt
is the conjugate base of an acid whose dissociation constant (pK~ in water at
298 °K is less
s than about 1.0, and the cation is ammonium ion or a metal ion with an ionic
radius which is
less than about 2/3 of the ionic radius of the pre-selected anion.
The crystal ionic radii of typical cations and anions are shown table III.
Table III Radius in Radius in
Cations* Angstroms Aeons ~gs~'oms
NH4+ 1.48 F 1.33
Li+ 0.68 CI- 1.81
Na+ 0.97 Bi 1.96
K+ 1.33 T 2.20
Rb+ 1.47 SCN-
Cs+ 1.67 0104
M~2+ 0.66 Methanesulphonate INCREASING
Ca + 0.99 Benzenesulphonate
Sr2+ 1.12
A13+ 0.51
Fe3+ 0.64
Zn2+ 0.74
Cu2+ 0.72
* Some uncertainty depending on source
The ratio of , ionic radii M°+ / A"- is shown in table IV. Salts with
ratio smaller than about
io 0.67 are generally acceptable, provided the dissociation constant (pKa) in
water at 298 °C of
the acid providing the anion is less than about 1Ø LiF and MgF2 are thus
excluded on pKa
grounds.
CA 02302731 2000-03-08
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- - 12
Table IV : Ratio of cation/anion radius -
Anions F' Cl' Br' ~ I' SCN' C104 CH3so; C6H,SO;
Ca'ons
y
NI-i4+ 1.11 0.82 0.76 0.67 ~ Decreasin
Li+ 0.51 0.375 0.347 0.309 ~ Decreasin
*
Na+ 0.73 0.536 0.495 0.441 ~ ~
Decreasin
K'' 1.00 0.735 0.679 0.605 -~
Decreasin
Rb+ I.11 0.81 0.75 0.668 ~ Decreasin
Cs+ 1.26 0.92 0.85 0.76 ~ Decreasin
M + 0.49* 0.36 0.34 0.30 -~
Decreasin
Ca + 0.74 0.55 0.51 0.45 ~ Decreasin
S + 0.84 0.62 0.57 0.5I ~ Decreasin
A1 + 0.28 0.26 0.23 ~ Decreasin
Fe + 0.35 0.33 0.29 ~ Decreasin
Zn + 0.41 0.38 0.34 ~ Decreasin
~ Cu + ~ 0.40 0.37 0.33 -~
~ ~ Decreasing
~
(*) = excluded on pKa grounds
The pKa values at 298 °K of certain acids providing anions useful (or
not useful) in this
s invention are shown in table V
Table V
"Allowed" Anions of Acid
1NCLUDED:-
Chloride < -1
Bromide < -I
Iodide < -1
Thioc anate ~ 1
Perchlorate -1
Nitrate -1.4
Trichloracetate 0.7
Benzene sul honate 0.7
Toluene sul honate 0.7
Na hthalene sul honate 0.57
Picrate 0.38
Perman anate -1
Methanesul honic acid -1
Trifluoromethanesul honic < -1
acid
2,4-dinitrobenzenesul honic -1
acid
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WO 99/14286 13 PCT/EP98/05718
EXCLUDED:
Fluoride 3.45
Phos hate O = P OH 3 ste s 2.12, 7.21,
1,2 & 3] 12.67
Carbonate ste s 1 & 2 6.37, 10.25
Acetate 4.75
Hi her alkanoates 4.8 - 5.0
Dichloracetic 1.48
For instance, the inorganic salt comprises anions which are the conjugate base
of an acid
selected from the class including hydrochloric acid; hydrobromic acid;
hydroiodic acid;
thiocyanic acid; perchloric acid; nitric acid; permanganic acid; sulphuric
acid; alkane
s sulphonic acids such as methane sulphonic acid and ethane sulphonic acid;
arene sulphonic
acids such as benzene sulphonic acid, toluene sulphonic acid and naphthalene
sulphonic
acid; alkane and arene sulphonic acids substituted with electron-withdrawing
groups such as
trifluoromethane sulphonic acid and 2,4-dinitrobenzene sulphonic acid; picric
acid and
trichloracetic acid. It is to be noted that phosphates, carbonates, alkanoates
and fluorides are
to excluded.
Examples of suitable salts are
~ ammonium iodide, ammonium thiocyanate, ammonium trichloracetate,
ammonium methanesulphonate, and ammonium salts of higher molecular weight
organosulphonic acids including halogeno-substituted or nitro-substituted
is sulphonic acids;
~ potassium bromide, potassium perchlorate, potassium nitrate, potassium
permanganate and potassium salts of the anions listed in this Claim for
ammonium;
~ sodium chloride and sodium salts of the other anions listed previously;
20 ~ any lithium salt of any of the anions listed previously;
~ a salt formed from any of the anions listed previously with any of magnesium
ion,
calcium ion, and strontium ion;
~ a salt formed from any of the anions listed in this Clairn with any of the
divalent
canons of manganese, iron, cobalt, nickel, copper, or zinc;
2s ~ a salt formed from any of the anions mentioned before with the trivalent
cations
of iron or aluminium.
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Organic bases -
Another type of suitable material comprises of organic bases that are
characterised by
exhibiting a pKa in water at 298 °K of more than 10Ø
pK8 data for some organic bases are shown in table VI
Table VI
Compound K at 298 K
Triethylamine 11.01
n-amylamine 10.6
n-decylamine 10.64
~
n-dodecylamine 10.63
Diethylene triamine ( 1 10.1
s' ionisation)
Triethylene tetramine( 10.2
ls' ionisation)
Piperidine 11.12
2,2,6,6-tetramethylpiperidine11.07
Pyrrolidine 11.27
1,2-dimethylpyrrolidine 10.2
1,3-diaminopropane (ls' 10.94
ionisation)
1,4-diaminobutane 11.15
Hexameth lene diamine 11.9
io
Examples of suitable organic bases are tri-alkylamines wherein the alkyl
groups contain from
2 to 18 carbon atoms; piperidine; alkylpiperidines such as 1-ethylpiperidine
and 2,2,6,6-
tetramethylpiperidine; pyrrolidine; alkylpyrrolidines such as 1,2-
dimethylpyrrolidine;
ethyleneamines such as diethylene triamine, triethylenetetramine; N-alkylated
ethyleneamines such as N,N,N',N'-tetramethylethylene diamine; alkylene
diamines such as
1,3-diaminopropane, 1,4-diaminobutane and hexylene diamine; guanidine;
N,N,N',N'-
tetramethylguanidine.
Quaternary ammonium salts
is A third type of dissolved component is a quaternary ammonium salt or
hydroxide. Those
include chlorides, bromides, iodides, methosulphates, ethosulphates or
hydroxides of
quaternary ammonium cations having alkyl and/or aryl and/or alkylaryl groups
such that the
total number of carbon atoms in all the groups combined with the nitrogen atom
is in the
range 8 to 60, and more preferably in the range 12 to 40. Examples include
tetrabutyl
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ammonium halides, tetraoctyl ammonium halides, dimethyldioctyl ammonium
halides,
methylbenzyldioctyl ammonium halides, tetradodecyl ammonium bromide.
N Alkyl pyridinium salts or hydroxide
s Another type of dissolved component is N-alkyl pyridinium salts or
hydroxides that possess
an alkyl, aryl, or alkylaryl group having between 6 and 24 carbon atoms
combined with the
nitrogen, and are provided as the chloride, bromide, iodide or hydroxide. An
example is
cetylpyridinium bromide.
to Examples of continuous liquid phase with enhanced electrical conductivity:
An impedance- analyser has been used to measure the electrical conductivity of
various liquid
samples over a range of frequencies from 5 Hz to 100 kHz. In the examples
below, the
measurements at 1 kHz and 10 kHz are given. The specific conductivity is in
units of
~,S m-'.
! s Example 1.
The conductivity of C,~ C,6 linear a-olefin (LAO) as component OL was
measured:
Frequency kHz) Specific Conductivi~r (,~S m'~)
0.03
0.2$
Example 2.
The conductivity of LAO as OL containing 1.1 % by weight of tetrabutylammonium
bromide
(TBAB) as component DC was measured:
Frequency (kHz Specific Conductivit~~~t.S m 1)
2s 1 0.17
10 0.49
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Example 3. -
The conductivity of dipropylene glycol monomethyl ether (DPM, ~ = 9,
solubility parameter
= 19.3) as component POL was measured:
Freauency (kHz) Specific Conductivity (~ m-1)
s 1 57.6
59.3
Example 4.
The conductivity of mixtures of TBAB in DPM at 1, 2 and 5% by weight were
measured:
Specific conductivity
(~.S m-~)
Frequency (kHz) 1 % TBAB 2% TBAB % TBAB
5
1 3.3 x10' 6.0x10' 1.5x104
10 3.4 x10' 6.0x10' 1.6x104
Example 5.
The conductivity of a mixture of LAO and DPM at 60/40 volume ratio,
respectively, was
measured:
Frequency (kHz) Specific Conductivit~yu,S m 1)
is 1 2.4
10 4.0
Example 6.
The conductivities of mixtures of LAO and DPM at 60/40 volume ratio,
containing 1, 2 and
3% of dissolved component TBAB were measured:
Specific conductivity
(p.S m ~ )
Frequency 1 % TBAB 2% TBAB 3 % TBAB
1 2.1x10 2.9x10 3.4x10
10 2.1 x 10' 2.9x 10~ 3.6x 10
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Figure 1 shows the measured conductivity depending on the chosen frequency for
the above -
mentioned OL, OL and POL at 60/40 ratio and OL and POL at 60/40 ratio
containing 1, 2
and 3% of dissolved component DC. The above examples show that the beneficial
use of
components DPM and TBAB increases the electrical conductivity of component LAO
by up
s to five orders of magnitude.
Example 7.
~o
is
A 60/40 volume mixture of LAO/N-octyl-2-pyrrolidone (SURFADONE LP-100
available
from GAF, USA ) + 5% TBAB produced conductivity of 550 uS m ~ at 500 Hz.
Examples of drilling fluid with enhanced electrical conductivity:
Example 8.
The mixture of example 7 was used as the liquid phase of a drilling fluid
according to the
following formulation of density 10.5 lb/gal:
Example 7 Base Fluid 224.6 g
ULT1DRILL EMUL HT 5.0 g
~~~ S 3.0 g
TRUVIS 8.0 g
L~ 2.0 g
BARITE 198.6
The conductivity of the above mud was 730 ~S m-1.
Example 9.
The organic-water ratio of the mud of example 8 was reduced to 97/3 by adding
the
2o proportional amount of brine to produce a water activity of 0.75:
Example 7 Base Fluid 218.0 g
ULTI17RILL EMUL HT 5.0 g
1N'TERDR1LL S 3.0 g
TRUVIS g,0 g
L~ 2.0 g
CaCl2 (83.5%) 3.53 g
WATER 8.36 g
BARITE 193.3
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The conductivity was measured to be1200 pS m-'. -
Example 10.
The organic-water ratio of the mud of example 8 was further reduced to 90/10
and the
s conductivity was measured to be 1,400 uS m-1.
Example 11.
The organic-water ratio of the mud of example 8 was further reduced to 60/40
and the
conductivity increased to 3,400 pS m''. The mud appeared stable but exhibited
an electrical
to stability (ES) voltage of only 6 Volts.
Example 12.
A 77/23 volume mixture of N-octyl-2-pyrrolidone and dimethyloctanoamide
(HALLCOMID
M8-10 available from CP HALL, USA) was produced. To this was added
10°l0 of TBAB.
is The conductivity of this mixture was 15,00011S m-~.
Ex$mple 13.
To 60 parts by volume of the mixture of example 12 was added 40 parts by
volume of LAO.
The conductivity of this mixture was 5.,500 E1S m-1.
Example 14.
The mixture of example 13 was used as the liquid phase of a drilling fluid
with the following
formulation (density 10.516/gal):
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Example 13 base Fluid 224.6 g
ULTIDRILL EMUL HT S.0 g
INTERDRILI, S 3.0 g
TRUVIS 8.0 g
LIME 2.0 g
BARTTE 198.6
The measured conductivity of this fluid was 5,000 pS m-' .
Example 15.
The organic-water ratio of the formulation of example 14 was reduced to 95/5
by adding a
s proportional amount of brine (density 10.5 lb/gal ; water activity 0.75):
Example 13 Base Fluid 213.7 g
ULTIDRILL EMUL HT 5.0 g
INTERDRILL S 3.0 g
TRUVIS 8.0 g
LIME 2.0 g
CaCl2 (83.5k) 5.89 g .
WATER 13.96 g
BARTTE 189.7 a
The measured conductivity of this formulation was 8,100 pS m-1.
Example 16.
The oil-water ratio of the formulation of example 15 was further reduced to
70/30. The
to conductivity increased to 11,700 pS m ~. The mud appeared stable but
exhibited an Electrical
Stability value of 0 Volts.
Example 17
The plot of figure 2 shows the variation of conductivity with volume ratio of
LAO to
pynrolidone-amide-salt mixture (defined in Example 12).
Example 18.
In this example, the mud was a 70130 organic-water ratio invert emulsion- of
density
10.5 Ib/gal. The organic liquid (continuous phase) of this mud consisted of a
40/60 volume
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mixture of LAO and a conductivity enhancing formulation. The conductivity
enhancing '
formulation was as described in Example 12, except. that the concentration of
TBAB was
7.5%.
The brine phase was saturated sodium bromide with a specific gravity of 1.50.
The water
s activity of the mud system was 0.58, measured at 22.5 °C. The
prepared formulation is
Components Amount to make 350
ml
ORGANIC LIQUID 154.3g
ULTmRILL EMUL HT 10.0 g
INTBRDRILL S 3.0 g
TRUVIS 8.0 g
LIME 2.Og
NaBr brine 136.7g
BARITE - 127.1 g
The drilling fluid was hot rolled at 250 °F (121 °C) for 16
hours and the Theological
properties determined before and after hot rolling
Parameter Before Hot RollingAfter Hot Rolling
Fann Dial Reading @ 600 rpm 57 57
Fann Dial Reading @ 300 rpm 35 36
Fann Dial Reading @ 200 rpm 27 28
Fann Dial Reading @ 100 rpm 18 18
Fann Dial Reading @ 6 rpm 6 6
Fann Dial Reading @ 3 rpm 5 5
s gel strength (Ib/100 5 8
sq ft)
10 rn gel strength {Ib/100 5 8
sq ft)
Apparent Viscosity {cps) 28'/x 28 ~/2
Plastic Viscosity (cps) 22 21
Yield Point {1b/100 sq ft) 13 15
Electrical Stability (V) 0 0
HTHP filtrate @ 250 C, 500 14
psi {ml)
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Conductivity Results (at 500 Hz and at room temperature):
Before Hot Rollin After Hot RolIin'~
.
Organic Liquid Phase0.9 x 104 ~,S
m'
Full mud 1.4 x 104 p,S 1.45 x 104 p,S ni'
rri'
Filtercake 1.3 x 104 ~S lri'
Filtrate (organic 0.4 x 104 p.S m''
phase)
The conductivity of freshly made mud is about 14,000 p,S rri'. This level is
maintained
through thermal aging at 250 °F. The filtercake and filtrate also show
increased conductivity.
The conductivity additives do not have a deleterious effect on the rheology,
both before and
s after thermal aging.
The volume of filtrate at 14 ml is an acceptable value for oil-based muds.
Shale dispersion inhibition
50 g of reactive cuttings (sized Oxford clay, 2-4 mm) was mixed in with 350 ml
of the mud.
is The mixture was then rolled in an oven at 50 °C for 2 hours. The
weight loss occurring in the
cuttings as a result of dispersion of the clay into the mud was then measured
on a dry weight
basis. For comparison with a water-based mud, a similar test was performed
with a sea-
water VISPLF.X mud. VISPLEX II, mark of Schlumberger, is a mixed-metal
hydroxide
system. The results are:
is Conductive OBM: ~0°7o dispersion
VISPLEX II: 10°!o dispersion
The conductive organic-based mud provided the shale dispersion inhibition
typical of oil-
based muds.
2a Example 19.
5°l0 (w/w) of sodium bromide (NaBr) was added to a 70/30 volume mixture
of ethoxylated
iauryl alcohol and tripropyleneglycol methylether. The room temperature
conductivity at
500Hz was 5000 N,S m-'.
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Example 20. -
The solvent mixture of example 19 was used to produce an invert emulsion mud
in which the
volume ratio of Ultidrill base fluid to the solvent mixture was 60/40. The
volume ratio of the
total organic liquid phase to the aqueous phase was 90/10. The formulation is
shown below:
ULTLDRILL base fluid119.3 TRUFLO 100 3.75
g g
Solvent mixture 96.3 TRUVIS HT 8.0 g
g
Sodium bromide I4.0 Lime 5.0 g
g
ULTIDRILL EMUL HT 10.0 Water 30.0
g g
ULTIDRILL FL 3.5 Barite 151.3
g g
s The room temperature conductivity at SOOHz was 600 p.S m-1.
Example 21.
10% (w/v) of lithium bromide (Liar) was added to a 50/50 volume mixture of
Ultidrill base
fluid and dipropylene glycol n-butyl ether (DPnB). The room temperature
conductivity at
io SOOHz was 7300 p.S m'1.
Example 22.
An invert emulsion
mud was produced
in which the volume
ratio of the organic
phase to the
aqueous phase was The
95/5. full
formulation
is
shown
below:
ULTIDRILL base 48.23 TRUVIS HT 12.0
fluid g g
195.8 LIIvvIE 5.0 g
g
LITHIUM BROMIDE 44.5 WATER 15.24g
g
ULTIDRILL EMUL 6.0 BARTTE 152.9
HT g g
INTERDRILL S 6.0
g
is The room temperature conductivity at 500 Hz was 9400 (p.S/m).
