Note: Descriptions are shown in the official language in which they were submitted.
PATENT
Case D 8543
~a~~~~~
OLEOPHILIC BASIC AMINE COMPOUNDS
AS AN ADDITIVE FOR INVERT DRILLING MUDS
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to new drilling fluids based on
ester oils and to invert drilling muds based thereon which
combine high ecological compatibility with good stability
and performance properties. One important application for
the new drilling fluids is in offshore drilling for the
development of oil or gas sources, the particular object of
the invention in this regard being to provide technically
useful drilling fluids of high ecological compatibility.
l0 The use of the new drilling fluids is of particular im-
portance in, but is not limited to, the offshore sector.
The new drilling fluids may also be used quite generally
for land-supported drilling, including for example
geothermal drilling, water drilling, geoscientific drilling
and mine drilling. In this case, too, the ester-based
drilling fluids selected in accordance with the invention
basically simplify ecotoxic problems to a considerable
extent.
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2. Discussion of Related Art
It is known that liquid drilling fluids for sinking
bores in rock and bringing up the rock cuttings are slight-
ly thickened, water-based or oil-based fluid systems. Oil-
based systems are being increasingly used in practice,
particularly in offshore drilling or in the penetration of
water-sensitive layers.
Oil-based drilling fluids are generally used in the
form of so-called invert emulsion muds which consist of a
three-phase system, namely: oil, water and finely divided
solids. The emulsions in question are of the water-in-oil
(w/o) emulsion type, i.e. the aqueous phase is present in
the continuous oil phase in heterogeneous fine dispersion.
There is a whole range of additives, including in
particular emulsifiers and emulsifier systems, weighting
agents, fluid loss additives, alkali reserves, viscosity
regulators and the like, for stabilizing the system as a
whole and for establishing the desired performance
properties. Full particulars can be found, for example, in
the Article by P. A Boyd et al entitled "New Base Oil Used
in Low-Toxicity Oil Muds" in Journal of Petroleum
Technology, 1985, 137 to 142 and in the Article by R.B.
Bennet entitled "New Drilling Fluid Technology - Mineral
Oil Mud" in Journal of Petroleum Technology, 1984, 975 to
981 and the literature cited therein.
oil-based drilling muds were originally made from
diesel oil fractions containing aromatic constituents. For
the purposes of detoxification and reducing the ecological
problems thus created, it was then proposed to use hydro-
carbon fractions substantially free from aromatic
compounds, now also known as "nonpolluting oils", as the
continuous oil phase, cf. the literature cited above.
Although certain advances were achieved in this way through
elimination of the aromatic compounds, a further reduction
in the environmental problems caused by drilling fluids of
the type in question here seems to be urgently required.
This applies in particular to the sinking of offshore wells
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for the development of oil and gas sources because the
marine ecosystem is particularly sensitive to the
introduction of toxic and non-readily degradable
substances.
The relevant technology has for some time recognized
the significance of ester-based oil phases for solving
these problems. Thus, U.S. Patents 4,374,737 and 4,481,121
describe oil-based drilling muds in which nonpolluting oils
are said to be used. Non-aromatic mineral oil fractions
and vegetable oils of the peanut oil, soybean oil, linseed
oil, corn oil and rice oil type, and even oils of animal
origin, such as whale oil, are mentioned alongside one
another as now3polluting oils of equivalent rank. The ester
oils of vegetable and animal origin mentioned here are all
triglycerides of natural fatty acids which are known to be
environmentally safe and which, ecologically, are distinct-
ly superior to hydrocarbon fractions, even where they have
been de-aromaticized.
InterPStingly, however, not one of the Examples in the
US patents cited above mentions the use of such natural es-
ter oils in invert drilling muds of the type in question
here. Mineral oil fractions are used throughout as the
continuous oil phase.
The investigations on which the present invention is
based have shown that the use of readily degradable oils of
vegetable or animal origin, which was considered in the
prior art, is not feasible for practical reasons. The rhe-
ologic properties of such oil phases cannot be controlled
for the wide temperature range required in practice of 0 to
5C on the one hand, and up to 250C and higher on the
other hand.
Ester oils of the type in question here do not in fact
show the same in-use behavior as the pure hydrocarbon-based
mineral oil fractions used hitherto. In practice, ester
oils irrespective of their constitution undergo partial
hydrolysis precisely in the w/o invert drilling muds,
resulting in the formation of free carboxylic acids. These
3
~ooss8s
free carboxylic acids in turn react with the alkaline
constituents always present in the drilling mud systems of
the type in question here, for example with the alkali
reserve used for corrosion prevention, to form the cor-
responding salts. However, salts of highly hydrophilic
bases and the acids having carbon chain lengths of about
to C24 predominantly encountered in oils of natural
origin are known to be compounds having comparatively high
HLB values which, in particular, lead to the formation and
stabilization of o/w emulsions. Use is made of this on a
very wide scale in the field of detergents and cleaning
preparations. However, the formation of even limited
quantities of such o/w emulsifier systems must interfere
with the w/o emulsions required for solving the problem
addressed by the invention and, hence, must lead to prob-
lems.
Co-pending Canadian applications Serial Nos. 2,006,009
and 2,006,010, filed December 19, 1989 relate to the use of
ester oils based on selected monocarboxylic acids or
monocarboxylic acid mixtures and associated monofunctional
alcohols. The co-pending applications show that it is
possible with the disclosed esters or ester mixtures of
monofunctional reactants not only to establish satisfactory
rheological properties in the fresh drilling mud, but also
to work with selected known alkali reserves in the drilling
mud and thus to prevent unwanted corrosion. According to
the teaching of these co-pending applications, it is
crucial so far as the alkali reserve is concerned that no
hydrophilic bases, such as alkali hydroxide and/or
diethanolamine, are present. The alkali reserve is formed
by the addition of lime (calcium hydroxide) or by the
presence of zinc oxide or comparable zinc compounds.
However, an additional limitation is necessary in this
regard also. If unwanted thickening of the oil-based
invert drilling~mud is to be
4
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2aoss8g
prevented in practice, the quantity of alkalizing additive
and, in particular, the quantity of lime have to be
limited. According to the disclosure of the co-pending
applications mentioned, the maximum addition envisaged is
put at about 2 lb/bbl (barrel) oil mud.
By contrast, the teaching of the present invention is
based on deeper considerations and realizations hitherto
unknown in the field of the invert drilling muds in ques-
tion here with their continuous oil phase. The teaching
according to the invention takes into account the fact
that, in practice, drilling muds of the type in question
containing ester oils undergo limited partial hydrolysis so
that free carboxylic acids are unavoidably formed to an
increasing _xtsnt as a hydrolysis product and, sooner or
later, reach a critical or at least endangered state of
aging reflected in unwanted thickening of the drilling mud.
The teaching according to the invention is based on the
concept of using an additional additive in invert drilling
muds of the type in question here which is capable of
keeping the desired rheological properties of the drilling
mud within the required limits, even when increasingly more
and more or even excessive quantities of free carboxylic
acids are formed by partial ester hydrolysis. In this
regard, the teaching of the invention seeks not only to
trap the free carboxylic acids formed in a harmless form,
but also to convert them, if desired, into valuable
components having stabilizing or emulsifying properties for
the system as a whole.
3. Description of the Invention
Other than in the operating examples, or where
otherwise indicated, all numbers expressing quantities of
ingredients or reaction conditions used herein are to be
understood as modified in all instances by the term
"about".
In a first embodiment, therefore, the present inven-
tion relates to the use of basic amine compounds of pro-
nounced oleophilic character and at most limited solubility
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in water, which are capable of forming salts with car-
boxylic acids, as an additive for w/o invert drilling muds
which contain in the continuous oil phase ester oils and,
together with the disperse aqueous phase, emulsifiers,
weighting agents, fluid loss additives and, if desired,
other additives for protecting the drilling muds against
unwanted thickening in use or for improving their flow
properties.
In another embodiment, the invention relates to w/o
invert drilling mud: which are suitable for the offshore
development of oiI and gas sources and, in a continuous oil
phase containing ester oils, contain a disperse aqueous
phase together with emulsifiers, weighting agents, fluid
loss additives arid, if desired, other typical additives.
In this embodiment, the invention is characterized in that
the drilling muds contain as an additional additive basic
amine compounds of pronounced oleophilic character and at
most limited solubility in water which are capable of
forming salts with carboxylic acids. The addition of the
additives according to the invention affords the drilling
muds protection against unwanted thickening in use and,
overall, is suitable for improving their flow properties.
Finally, in another embodiment, the invention relates
to additive mixtures which are suitable for the stated
purpose in drilling muds containing ester oils and which
contain the basic amine compounds of pronounced oleophilic
character and at most limited solubility in water, which
are capable of forming salts with carboxylic acids, in a
solvent miscible with the oil phase. Preferred solvents
are so-called nonpolluting oils, particular significance
again being attributed in this regard to the ester oils.
In mixtures of the type just mentioned, the anti-aging
agents based on the oleophilic basic amine compounds are
best present in concentrations of at least about 20% by
weight and preferably in concentrations of at least about
50% by weight.
The essence of the teaching according to the invention
6
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in all its embodiments is the finding that, where the anti-
aging agents according to the invention based on oleophilic
basic amine compounds are used, the carboxylic acids una-
voidably formed in practice through partial hydrolysis of
the ester oils are trapped without the Theological proper-
ties of the invert mud being adversely affected. By
selecting suitable amine compounds, it is even possible to
form valuable stabilizing or emulsifying mixture
constituents in situ through the salt formation which now
occurs. The oleophilic basic amine compounds may be added
to the drilling mud systems from the outset or may be added
to them during use. It has been found that it is even
possible by adding or using the basic oleophilic amine
compounds according to the invention to regenerate aged and
undesirably thickened drilling muds of the type in question
here to such an extent that their Theology is reduced to
the range required for pumpability and free flow, even at
low terr~peratures.
The use of the additives according to the invention
has revealed another important simplification in the
composition of w/o drilling muds, namely: the alkalization
of the drilling mud required for corrosion prevention and,
in particular, the creation of an adequate alkali reserve,
particularly against inrushes of acidic gases, such as C02
and/or H2S, becomes unproblematical. The basic amine
compounds of pronounced oleophilic character proposed as
additives in accordance with the invention spontaneously
form a basicity buffer which may be used as an alkali
reserve. Of greater importance is the surprising obser-
vation that the use of conventional alkali reserves and, in
particular, the use of lime, which is particularly in-
expensive, becomes at least largely unproblematical if the
anti-aging additives acccording to the invention are simul-
taneously present in the drilling mud. In general, the
above-mentioned limit of approximately 2 lb/bbl (lime/oil
mud) for drilling muds based on ester oils, which is
disclosed in the earlier applications cited above, may be
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safely exceeded providing the basic amine compounds of
pronounced oleophilic character according to the invention
are present in the oil mud. Even if unwanted thickening
has occurred through the use of conventional, highly hydro-
philic alkali reserves, it may be eliminated by incorpora-
tion of the additive component according to the invention
in the system as a whole.
The basic amine compounds of pronounced oleophilic
character selected in accordance with the invention are
discussed in more detail in the following.
Basic amine compounds containing relatively short
carbon chains are known to be highly soluble in water and,
optionally, miscible with water in any quantitative ratios.
By contrast, the amine compounds selected in accordance
with the invention are characterized by distinctly limited
solubility in water with simultaneous development of their
oleophilic character. Their solubility in water at room
temperature is generally less than about 10% by weight and,
in the preferred embodiment, does not exceed a value of
approximately 5% by weight. Of importance above all are
oleophilic amine compounds which have very small limits for
their solubility in water at room temperature. An impor-
tant limit is at about 1% by weight and preferably at less
than about 0.1% by weight. Particularly important basic
amines for the purposes of the invention may be regarded as
substantially insoluble in water.
Oleophilic amines of the described type may generally
be used providing they are capable of forming salts with
the carboxylic acids released during the ester hydrolysis
and, preferably, are soluble in the oil phase. In the con-_
text of the aspect according to the invention of causing
minimal toxic environmental pollution, preference is
attributed to ecologically comparatively safe representa-
tives of this wide range of basically suitable amine com-
pounds. From these considerations, it follows that aromat-
is amines are generally less suitable so that another
preferred embodiment of the invention is characterized by
,~ 8
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zoo~ss9
the use of oleophilic amine compounds which are at least
substantially free from aromatic constituents. Suitable
compounds for carrying out the teaching according to the
invention may generally be assigned to the groups of
aliphatic, cycloaliphatic and/or heterocyclic amines. The
particular representatives may contain one or even more N
groups capable of forming salts with carboxylic acids.
Amine compounds of the described type may be nitrogen-
containing saturated hydrocarbon compounds, although amine
hydrocarbons containing one or more olefinically unsaturat-
ed groups in at least one of their hydrocarbon members are
also suitable.
There is considerable freedom of choice in regard to
the particsilar cotatitution of the amine components used in
accordance with the invention. Economic considerations
largely dictate the choice of the particular components.
In general, particularly suitable representatives may be
assigned to the following classes:
Primary, secondary or tertiary amines at least
substantially insoluble in water, corresponding aminoamides
or heterocycles containing nitrogen as a ring constituent.
Amine bases containing at least one long-chain hydrocarbon
radical preferably having approximately 8 to 36 carbon
atoms and, more preferably, approximately 10 to 24 carbon
atoms in the molecule can be particularly suitable. These
hydrocarbon radicals may be directly attached to the
nitrogen atom. However, they may also be attached to an N-
containing part of the molecule through a functional group,
as in the case of the aminoamides for example. In this
case, it is important to ensure that at least one basic N
atom capable of forming a salt with the carboxylic acids
released by ester hydrolysis is present in the molecule as
a whole. Typical examples of the various classes mentioned
here are discussed in more detail in the following.
A first group comprises primary, secondary and terti-
ary amines containing one or more N atoms, the ratio of
hydrocarbon groups to amine groups in the particular
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compound being selected so that the conditions stated above
with regard to limited solubility in water and pronounced
oleophilic character are fulfilled. In simple unsubstitu-
ted compounds of the type in question, the C:N ratio is at
least about 5 or, better yet, 6, but preferably higher. In
amines of the type in question readily obtainable on an
industrial scale, 1 or 2 comparatively long-chain hydrocar-
bon radicals and, far the rest, methyl groups are often
present at the aminonitrogen. Typical examples of the type
l0 in question here contain 1 nitrogen atom per molecule.
Comparable compounds derived from polyfunctional amines,
partic~.~larly lower diamines, for example ethylenediamine or
propylenediamine, are also readily obtainable on an in-
dustrial scale. Lower polyamines of the type in question
here are highly soluble in water. However, if one or more
long-chain hydrocarbon radicals of the above-mentioned type
are introduced into their molecule, suitable additives
according to the invention are formed providing at least
one nitrogen atom is capable of salt formation with the
carboxylic acids. Suitable representatives of this type
are, for example, compounds corresponding to the general
formula R-NH-(CH2)~-NH2 where R is, for example, a hydrocar-
bon radical containing approximately 8 to 22 C atoms and n
is a low number of up to about 6 and, more preferably, from
2 to 4.
Primary and possibly even secondary amines in which
parts of the molecule are of pronounced oleophilic charac-
ter may be suitable for the purposes of the invention even
when oligo-alkoxide groups are introduced at the NH groups
present by alkoxylation with, for example, ethylene oxide
(EO) or propylene oxide (PO) or higher homologs, for
example butylene oxide. For example, long-chain primary
or secondary amines are sufficiently oleophilic, even where
up to about 8 to 10 EO or PO groups are introduced, so that
they may be considered for use in accordance with the
invention.
Industrially readily obtainable amine compounds for
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use in accordance with the invention are derived from the
epoxidation of olefinically unsaturated hydrocarbon com-
pounds with subsequent introduction of the N function by
addition to the epoxide group. The reaction of the epoxi-
dized intermediate components with primary or secondary
amines to form the corresponding alkanolamines is of parti-
cular significance in this regard. Polyamines, particular-
ly lower polyamines of the corresponding alkylenediamine
type, are also suitable for opening of the epoxide ring.
Another important class of the oleophilic amine com-
pounds for ~'!-xe purposes of the invention are aminoamides
derived fro: preferably long-chain carboxylic acids and
polyfunctiorlal, particularly Lower, amines of the above-
mentioned type. The key factor in their case is that at
least one of the amino functions is not bound in amide
form, but remains intact as a potentially salt-forming
basic amino group. Both in this case and in all the cases
dicussed in the foregoing, the basic amino groups, where
they are formed as secondary or tertiary amino groups, may
contain hydrc~;yalkyl substituents and, in particular, lower
hydroxyalkyl ~ubstituents containing up to 5 and preferably
up to 3 C atoms in addition to the oleophilic part of the
molecule. Suitable N-basic starting components for the
preparation of such adducts containing long-chain oleophil-
is molecule constituents are monoethanolamine or
diethanolamine. Thus, in one preferred embodiment, suit-
able additives according to the invention are reaction
products from the epoxidation of long-chain olefins con-
taining, for example, 8 to 36 and, in particular, approx-
imately 10 to 18 C atoms and mono- or diethanolamine. a-
Olefins of the type mentioned may be particularly important
as a starting material for the epoxidation and the
subsequent reaction to the secondary or tertiary amine
containing hydroxyalkyl groups at the N atom.
An important class of heterocyclic additives for
regulating the flow properties of the drilling muds accord-
ing to the invention are the imidazoline compounds. Other
11
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important members of this heterocylic group are alkyl-
pyridines.
The additives based on oleophilic basic amine com-
pounds according to the invention are preferably added to
the drilling muds in quantities of no more than about 10
lb/bbl and, more preferably, in quantities of no more than
lb/bbl. The quantity used may be determined inter alia
by the type of application envisaged in practice. Many
variants are possible in this regard and may even be
combined with one another.
In a first embodiment, the flow-control additive is
added to the drilling mud in a considerable quantity from
the outset and, in this case, may perform a dual function.
On the one hand, it forms the alkali reserve of the dril-
ling mud to trap any inrushes of acidic constituents, such
as COZ and/or H2S; on the other hand, the basic amine
compound optionally present in a large excess takes up the
carboxylic acid components formed by hydrolysis as they are
being formed and converts them into the corresponding oil-
soluble salts. In the opposite extreme case, the invention
initially operates with the drilling mud based on ester oil
without the additives according to the invention, for
example in accordance with the teachings of the co-pending
applications cited above. If aging of the drilling mud
occurs, as reflected in an incipient increase in viscosity,
the flow-control additive according to the invention is
added to the drilling mud continuously or in portions.
This may readily be done during drilling. It is clear that
any combinations between these two extremes are possible
for the introduction of the additive according to the
invention before and during the drilling operation or the
use of the drilling mud. Providing suitable amine
compounds forming effective emulsifier systems are used, it
is even possible to save emulsifier in the oil to be
subsequently added and, instead, to use the emulsifying
amine salts formed in situ to stabilize the system as a
whole.
12
Ate
The amine compounds may be added to the invert dril-
ling muds directly or indirectly. Thus, they may be
incorporated beforehand in the oil phase containing ester
oil or are added to the overall system as such. In one
particularly suitable embodiment, additive concentrates are
prepared and may then be added to the drilling mud, par-
ticularly during drilling. The products in question are
solutions of the oleophilic amine compounds in suitable
solvents with preferred concentrations of the additive of
at least about 20% by weight, but preferably of at least
about 50% by weight. Suitable solvents are nonpolluting
oils which may be homogeneously incorporated in the drill-
ing mud. Ester oils, for example of the type mentioned in
the two co-pending applications cited, and described herein
below, are particularly suitable for this purpose.
As already mentioned, it is an important advantage of
the invention that the use of the additives according to
the invention to regulate the flowability and pumpability
of the drilling muds now opens up the possibility, even in
the case of oil phases based on ester oil, of using conven-
tional alkali reserves in the quantities hitherto typically
used for drilling muds based on mineral oils as the oil
phase. For example, lime may be used in quantities of up
to 5 lb/bbl with no risk of lasting damage to the drilling
mud in operation. The same applies to the zinc compounds
mentioned in the co-pending applications, such as zinc oxide,
zinc complex compounds and the like. Surprisingly, how-
ever, it is even possible to use the strongly hydrophilic
bases hitherto typically used for the alkalization of dril-
ling muds. If the alkali reserve is formed as described
by conventional means, for example by the use of consider-
able quantities of lime, the quantity of amine-based
additives selected in accordance with the invention may be
reduced into the range required during the process as a
result of ester saponification. In one important embodi-
ment, only a slight excess of the oleophilic amine base is
used and the amount consumed by salt formation is added
13
continuously or in portions during the drilling operation.
In this embodiment, the quantity of amine base added may
be, for example, in the range from 0.1 to 2 lb/bbl (amine
base/drilling mud) or even smaller.
Particularly suitable ester oils are esters of mono-
functional carboxylic acids or carboxylic acid mixtures and
monofunctional alcohols, more especially the esters de-
scribed in detail in the co-pending applications cited above,
To complete the disclosure of the invention, essential
characteristics of those ester or ester mixtures are
briefly summarized in the following.
In a first embodiment, esters which are flowable and
pumpable at 0 to 5°C of monohydric C2_~2 and, more
particularly, C4_~2 alcohols and aliphatic saturated
~6 monocarboxylic acids or mixtures thereof with at most
substantially equal quantities of other monocarboxylic
acids are used as the oil phase. Preferred ester oils are
those of which at least about 60% by weight, based on
carboxylic acid mixture, are esters of aliphatic C
monocarboxylic acids and optionally, for the remainder,
small quantities of relatively short-chain aliphatic or
relatively long-chain, in that case more especially mono-
or polyolefinically unsaturated monocarboxylic acids.
Preferred esters are those which have a Brookfield (RVT)
viscosity at 0 to 5'C of no more than 50 mPa.s, preferably
of no more than 40 mPa.s and, more preferably, of at most
30 mPa.s. The esters used in the drilling mud have
solidification values (pour point and setting point) below
-10'C and preferably below -15'C and, in particular, flash
points above 100'C and preferably above 150'C. The
carboxylic acids present in the ester or ester mixture are
at least predominantly linear and, preferably, of vegetable
origin. They may be derived from corresponding
triglycerides, such as coconut oil, palm kernel oil or
babassu oil. The alcohol radicals of the esters used are
derived in particular from linear or branched saturated
alcohols preferably containing 4 to 10 C atoms. These
14
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alcohol components may also be of vegetable or animal
origin, having been obtained by reductive hydrogenation of
corresponding carboxylic acid esters.
The other class of particularly suitable ester oils is
derived from mono- or polyolefinically unsaturated 06_24
monocarboxylic acids or mixtures thereof with small
quantities of ather, in particular, saturated
monocarboxylic acids and monofunctional CZ_iZ alcohols.
These ester oils are also flowable and pumpable at
l0 temperatures in the range from 0 to 5C. Particularly
suitable esters of this type are those of which more than
70% by weight, pri~ferably more than 80% by weight and, in
particular, more than 90% by weight are derived from
olefinically unsafi~e~:cated 06_24 carboxylic acids.
In their case, too, the solidification values (pour
point and setting point) are below -10C and preferably
below -25C, while the flash points are above 100C and
preferably above 160C. The esters used in the drilling
mud have a Broakfield (RVT) viscosity at 0 to 5C of no
more than 55 mPa.s and preferably of no more than 45 mPa.s.
Ester oils of the type herein may be divided into two
sub-classes. In the first sub-class, no more than 35% by
weight of the unsaturated 06_24 monocarboxylic acid residues
in the ester are derived from di- and polyolefinically
unsaturated acids, preferably at least about 60% by weight
of the acid residues being mono-olefinically unsaturated.
In the second sub-class, more than 45% by weight and
preferably more than 55% by weight of the 06_24 monocar-
boxylic acids in the ester mixture are derived from di- or
polyolefinically unsaturated acids. Saturated
carboxylic acids in the ester mixture best make up no more
than about 20% by weight and, in particular, no more than
about 10% by weight. However, saturated carboxylic acids
preferably have relatively low C chain lengths of the acid
residues. In this case, too, the carboxylic acid residues
present are at least predominantly linear and are of
preferably vegetable or animal origin. Vegetable starting
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materials are, for example, palm oil, peanut oil, castor
oil and, in particular, rapeseed oil. Carboxylic acids of
animal origin are, in particular, corresponding mixtures of
fish oils, such as herring oil.
Invert drilling muds of the type herein typically
contain the finely disperse phase, together with the
continuous oil phase, in quantities of from about 5 to 45%
by weight and preferably in quantities of from about 5 to
25% by weight. The range from about 10 to 25% by weight
l0 of disperse aqueous phase can be particularly important.
The following rheologic data apply to the rheology of
preferred invert drilling muds according to the invention:
plastic viscosity (PV) in the range from about 10 to 60
mPa.s and preferably in the range from about 15 to 40
mPa.s, yield point (YP) in the range from about 5 to 40
lb/100 ftz and preferably in the range from about 10 to 25
Ib/100 ft2, as measured at 50C. Full information on the
determination of these parameters, on the measurement tech-
niques used and on the otherwise standard composition of
the invert oil muds described herein can be found in the
prior axt cited above and, for example, in "Manual of Dril-
ling Fluids Technology" published by NL-Baroid, London, GB,
cf. in particular the Chapter entitled "Mud Testing - Tools
and Techniques" and "Oil Mud Technology", which is freely
available to interested experts. In the interests of
fullness of disclosure, the following summary observations
may be made:
Emulsifiers suitable for use in practice are systems
which are capable of forming the required w/o emulsions.
Selected oleophilic fatty acid salts, for example those
based on amidoamine compounds, are particularly suitable,
examples being described in the previously cited U.S.
Patent 4,374,737 and the literature cited therein. One
particularly suitable type of emulsifier is the product
marketed under the name of "EZ-mul~" by NL Baroid, London.
Emulsifiers of the type in question here are marketed
in the form of concentrates and may be used, for example,
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in quantities of from about 2.5 to 5% by weight and more
especially in quantities of from about 3 to 4% by weight,
based in each case on the ester oil phase.
In practice, hydrophobicized lignite in particular is
used as a fluid-loss additive and, hence, in particular for
forming an impervious coating in the form of a substan-
tially water-impermeable film over the walls of the well.
Suitable quantities are, for example, in the range from
about 15 to 20 lb/bbl or in the range from about 5 to 7% by
weight, based on the ester oil phase.
In drilling muds of the type herein, the thickener
normally used to create viscosity is a cationically
modified, finely divided bentonite which may be used in
particular in quantities of from about 8 to 10 lb/bbl or
in the range from about 2 to 4% by weight, based on the es-
ter oil phase. The weighting agent normally used in prac-
tice to establish the necessary pressure equalization is
baryta which is added in quantities adapted to the partic-
ular conditions to be expected in the well. For example,
it is possible by addition of baryta to increase the speci-
fic gravity of the drilling mud to values of up to about
2.5 and preferably in the range from about 1.3 to 1.6.
In invert drilling muds of the type herein, the
disperse aqueous phase is charged with soluble salts,
generally calcium chloride or potassium chloride, the
aqueous phase preferably being saturated with the soluble
salt at room temperature.
The emulsifiers or emulsifier systems mentioned above
may also be used to improve the oil wettability of the in-
organic weighting materials. In addition to the amino-
amides already mentioned, alkyl benzenesulfonates and imi-
dazoline compounds are mentioned as further examples. Ad-
ditional information on the relevant prior art can be found
in the following literature references: GB 2,158,437, EP
229 912 and German 32 47 123.
In addition to the advantages already mentioned, the
drilling fluids based in accordance with the invention on
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the co-use of ester oils of the described type are also
distinguished by distinctly improved lubricity. This is
particularly important when the path of the drill pipe and
hence the well deviate from the vertical during drilling,
for example at considerable depths. In such cases, the
rotating drill pipe readily comes into contact with the
well wall and embeds itself therein. Ester oils of the
type used as oiI phase in accordance with the invention
have a distinctly better lubricating effect than the
mineral oils hitherto used, which is an important advantage
of the teaching according to the invention.
E x a m p 1 a s
In the following Examples, two typical ester oils are
used as the oil phase of the invert drilling muds. In both
cases, the ester oils in question are monocarboxylic acids/
monoalcohol esters which may be characterized as follows:
Examples 1 to 3: distilled n-hexyl lauric acid ester having
the following characteristic data:
flash point above 165C, pour point above -5C, density
(20C) 0.857 to 0.861, iodine value and acid value below 1,
water content below 0.3%, and the following viscosity data
(Brookfield mFa.s) in the low-temperature range:
-5C, 22.5 to 25.5; + 2C, 15 to 18; + 5C, 15 to 18: +
10C, approx. 15; 20C, 12 to 14.
Examples 4 to 10: isobutyl rapeseed oil ester based on a
mixture of predominantly unsaturated linear carboxylic
acids corresponding to substantially the following distri-
bution: 60% oleic acid, 20% linoleic acid, 9 to 10% lino-
lenic acid, olefinically unsaturated C2o_ZZ monocarboxylic
acids approx. 4%, remainder saturated monocarboxylic acids
predominantly in the C~b_~8 range.
The rapeseed oil ester used has the following charac-
teristic data: density (20C) 0.872 g/cm3; pour point below
-15C; flash point (DIN 51584) above 180C; acid value
(DGF-C-V 2) 1.2; viscosity at 0C 32 mPa.s, viscosity at
5C 24 mPa.s.
18
An invert drilling mud is conventional~~~~~d
using the following constituents:
230 ml ester oil
26 ml water
6 g organophilic bentonite (Geltone II~, a product of
NL Baroid)
12 g organophilic lignite (Duratone~, a product of NL
Baroid)
x g lime
6 g w/o emulsifier (EZ-mul NT~, a product of NL
Baroid)
346 g baryta
9.2 g CaClz x 2 H20
y g oleophilac basic amine
The plastic viscosity (PV), the yield point (YP) and
the gel strength after 10 secs. and 10 mins. of the partic-
ular invert drilling mud tested are first determined by
~~neasuring the viscosity of the unaged material at 50°C.
The invert drilling mud is then stored in an autoclave
(so-called roller oven) for 16 hours at 125°C to investi
gate the effect of temperature on emulsion stability. The
viscosities are then remeasured at 50°C.
ExamQl a 1
The n-hexyl ester of lauric acid was used as the oil
phase. Lime was added in a quantity of 2 g to the above
starting formulation. There was no addition of a basic
amine of pronounced oleophilic character corresponding to
the definition according to the invention. The following
values were detex-mined on the material before and after
aging:
Unaged Aged
material material
Plastic viscosity (PV) 19 50
Yield point (YP) 8 36
Gel strength (lb/100 ftz)
10 secs. 6 41
10 mins. 7 48
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The drilling mud undergoes considerable thickening
after aging for only 16 hours at 125'C. The quantity of
lime used is above the threshold value of 2 lb/bbl.
Example 2
0.5 g of a basic amine of pronounced oleophilic
character was added to the invert drilling mud of Example
1. The reaction product of an epoxidized~c~2_~4 a-olefin and
diethanolamine (Applicants' Araphen G2D') was used as the
basic amine.
The Theological data of the material before and after
aging are as follows:
Unaged Aged
material material
Plastic viscosity (PV) 19 36
Yield point (YP) 9 18
Gel strength (lb/100 ft2)
secs. 5 20
10 rains. 7 33
Example 3
The same oleophilic basic amine as in Example 2
("Araphen G2D") was added to the invert drilling mud in a
quantity of 1 g. The material shows the following values
before and after aging:
Unaged Aged
material material
Plastic viscosity (PV) 20 21
Yield point (YP) 8 6
Gel strength (Ib/100 ft2) .
10 secs. 5 4
10 rains. 6 5
Comparison of Examples 1 to 3 with one another clearly
shows the stabilizing effect of the addition of an oleophi-
C
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lic basic amine corresponding to the definition according
to the invention.
Example 4
In this Example and in Examples 5 to 9, the isobutyl
rapeseed oil ester defined above was used as the continuous
oil phase.
In Example 4, no lime was added, although 2 g of the
oleophilic basic amine ("Araphen G2D") defined above was
incorporated in the drilling mud. The material shows the
following values before and after aging:
Unaged Aged
material material
Plastic viscosity (PV) 28 28
Yield point (YP) 11 4
Gel streAzgth (lb/100 ft2)
10 secs. 15 6
10 mins. 13 9
Example 5
Example 4 vas repeated, except that stearyl amine was
used in a quantity of 2 g as the oleophilic basic amine.
The material shows the following values before and after
aging:
Unaged Aged
material material
Plastic viscosity (PV) 27 27
Yield point (YP) 16 5
Gel strength (lb/100 ftZ)
10 secs. 12 5
10 mins. 13 7
Example 6
For comparison, 1 g lime was added to the isobutyl
rapeseed oil ester in the absence of oleophilic basic amine
21
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compounds. The quantity of 1 g used in the starting
formulation is below the threshold value of 2 lb/bbl which,
for the formulation used here, corresponds to an addition
of approximately 1.35 g lime.
The rheological data of the material before and after
aging are as follows:
Unaged Aged
material material
Plastic viscosity (PV) 27 28
Yield point (YP) 10 18
Gel Strength (lb/100 ftZ)
10 secs. 6 6
10 mins. 8 8
Example 7
2 g of the oleophilic basic amine compound "Araphen
G2D" were added to the formulation of Example 6. The
drilling mud shows the following rheological values:
Unaged Aged
material material
Plastic viscosity (PV) 30 32
Yield point (YP) 10 11
GeI strength (lb/100 ft2)
10 secs. 8 7
10 mins. 9 7
Example 8
An isobutyl rapeseed oil ester was again investigated
with addition of 2 g lime to the starting formulation, but
without the addition of the oleophilic basic amine. The
rheol~~gical data are as follows:
Unaged Aged
material material
Plastic viscosity (PV) 27 84
Yield point (YP) 12 22
Gel strength (lb/100 ft2)
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secs. 7 21
10 mires. 8 51
Comparison of Example 8 with Example 6 shows the
considerable thickening effect which is initiated during
5 aging when the quantity of lime is increased beyond the
threshold value of approximately 2 lb/bbl.
Example 9
2 g ~'Araphen G2D" was added to the invert drilling mud
10 of Example 8. The material shows the following Theological
values before and after aging:
Unaged Aged
material material
Plastic viscosity (PV) 28 32
Yield point (YP) 15 12
Gel strength (lb/100 ftZ)
10 secs. 8 6
10 mires. 8 6
Comparison with the Theological data of Example 8
shows the effect of the oleophilic basic amine compound
added in accordance with the invention.
Example 10
2 g diethylenetriamine, i.e. a strongly hydrophilic
base, was added to the invert drilling mud of Example 8.
The Theological data of the material was determined before
aging.
This invert drilling mud was then aged for 16 hours at
125°C in the same way as described above. It was found
that the mud thickened to such an extent that the Theologi-
cal data could not be measured.
2 g of the oleophilic basic amine compound "Araphen
G2D" were added to the thickened mass and the resulting
mixture re-aged for 16 hours at 125°C in a roller oven.
The thickened mass was liquefied so that its Theological
23
2009689
data could now be measured.
Overall, the following values were determined:
Unaged 1st aging 2nd aging
material after addi-
tion of the
amine com-
pound
Plastic viscosity (PV) 31 cannot be 45
measured
Yield point (YP) 24 25
Gel strength
10 secs. 16 114
10 mins. 23 120
24
