Note: Descriptions are shown in the official language in which they were submitted.
-1- _.2058636
Use of selected ester oils in water-based drilling fluids of the O/W- emulsion
tvpe and
corresponding drilling fluids with improved ecological acceptabilitx
The invention discloses new drilling fluids based on water-based 0/W-
emulsions and O/W-emulsion drilling muds based thereon, which are
distinguished by high ecological acceptability and at the same time
good standing and application properties. An important area of use
for the,new drilling mud systems is in off-shore wells for the
development of petroleum and/or natural gas deposits, the aim of the
invention being particularly to make available drilling fluids with
high ecological acceptability which can be used in industry. The use
of the new drilling mud systems admittedly has particular
significance in the marine environment, but is not limited thereto.
The new mud systems can also be put to quite general use in land-
based drilling, i.e. also for the development of petroleum and/or
natural gas deposits hare. They are, however, new valuable working
agents, for example, also in geothermal wells, in water bore-holes,
in the drilling of geoscientific bores and in drilling for the mining
industry. It is also essentially true hare that the associated
ecotoxic problems are substantially simplified by the new water-based
O/W-drilling fluids selected according to the invention.
The Prior Art
Liquid mud systems used in the sinking of rock bores for bringing up
the loosened drill cuttings are known to be flowable systems,
thickened to a limited extent, which can be assigned to one of the
three following classes:
Purely aqueous drilling fluids; drilling mud systems based on oil,
which as a rule are used in the form of so-called invert emulsion
muds, and represent preparations of the W/O-emulsion type in Which
the aqueous phase is distributed as a heterogeneous fine dispersion
in the continuous oil phase. The third class of the known drilling
fluids is composed of water-based O/W-emulsions, i.e. fluid systems
which contain a heterogeneous, finely-dispersed oil phase in a
continuous aqueous phase. The invention discloses improved systems
of this latter type.
X;
zo5ss~s
- 2 -
The application properties of the drilling fluids of such O/W-emulsion
systems take an intermediate position between the purely aqueous
systems and the oil-based invert fluids. The advantages, but also the
disadvantages, of the purely aqueous systems are connected with the
advantages and disadvantages of the oil-based invert-emulsions
disclosed hitherto. Detailed information on this subject can be found
in the relevant specialist literature, refer, for example, to the text
book by George R. Gray and H.C.H. barley, "Ca~osition and Properties
of Oil Well Drilling Fluids", 4th. edition, 1980/1981, Gulf Publishing
Co~any, Houston, and the extensive specialist and patent literature
cited therein and to the manual "Applied Drilling Engineering", Adam T.
Hourcpyne, Jr. et al., First Printing Society of Petroleum Engineers,
Richardson, Texas (USA).
One of the main weaknesses of purely water-based drilling mud systems
lies in the interaction of water-sensitive, particularly water-
swellable, rock and/or salt formations with the aqueous drilling fluid
and the secondary effects initiated thereby, in particular bore-hole
instability and thickening of the drilling fluid. Many proposals
are concerned with the reduction of this problem area and have, for
example, resulted in the development of the so-called inhibitive water-
based muds, cf. for exanple, "Applied Drilling Engineering", loc. cit.,
Chapter 2, Drilling Fluids, 2.4 and Gray and barley loc. cit., Chapter
2, in particular the sub-section on pages 50 to 62 (M~.uls for "Heaving
Shale", Muds for Deep Holes, Non-Dispersed Polymer Muds, Inhibited
Muds: Potassium Compounds).
In more recent practice, in particular drilling fluids based on oil,
which consist of the 3-phase system oil, water and finely particulate
solids and are preparations of the W/0-emulsion type, have succeeded
in overoaning the difficulties described above. Oil-based drilling
fluids were originally based on diesel oil fractions contain;ng
aranatics. For detoxification and to reduce the ecological problems
created thereby, it was then proposed to use hydrocarbon fractions
which are largely free of aranatics - nvw also lu~wn as "non-polluting
oils" - as the continuous oil phase, see in this regard, for example,
the publications by E.A. Hoyd et al. "New Base Oil Used in Low Zbxicity
Oil Muds", Journal of Petroleum Technology, 1985, 137 - 143 and R.B.
2U58636
- 3 -
Bennet "New Drilling Fluid Technology - Mineral Oil Mud", Journal of
Petroleum Technology, 1984, 975 - 981 and the literature cited therein.
Drilling fluids of the water-based 0/W-eqnulsion system type have also
hitherto used pure hydrocarbon oils as the dispersed oil phase, cf.
here, for exanple, Gray, barley loc. cit., p. 51/52 under the section
"Oil nnulsion Muds" and the tabular stunnary on p. 25 (Tables 1-3) with
details of water-based emulsion fluids of the salt-water mud, lime mud,
gyp mud and C~CLS mud type .
In this context in particular it is known that water-based 0/W-emxlsion
fluids represent a substantial improvement in many regards to the
purely water-based drilling mud systems. Particularly in more recent
times, however, the advantages and disadvantages of such water-based
emulsion fluids have also been examined critically in ca~~arison with
the oil-based invert-systems. Thie is due to the considerable
ecological reservations felt towards the oil-based invert drilling
fluids camanly used today.
These ecological reservations can be subdivided into two problem areas:
In addition to the basic constituents, i.e. oil and water, all drilling
fluid systems based on water and/or oil require a large number of
additives for the establishment of the desired application properties.
The following can be mentioned here purely by way of example:
emulsifiers or emulsifier systems, weighting agents, fluid-loss
additives, wetting agents, alkali reserves, viscosity regulators, in
some cases auxiliary agents for the inhibition of drilled rock w2th
high water-sensitivity, disinfectants and the like. A detailed stunnary
can be found, for example, in Gray and barley, loc. cit., Chapter 11,
"Drilling Fluid Catponents". The industry has developed additives
which currently appear ecologically harmless, but also additives which
are evologically questionable or even ecologically undesirable.
The second problem area is caused by the oil phases used in such
drilling fluids. Even the hydrocarbon fractions which are largely free
from ara~atics, currently known as "non-polluting oils", are not
oonpletely harmless when released into the environment. A further
2o5s636
- 4 -
reduction in the enviiror~nental problems, which are caused by the fluid
oil phases of the type referred to here, appears urgently necessary.
This is true in particular for the sinking of off-shore wells, e.g.,
for the develo~nent of petroleum or natural gas deposits, because the
marine eco-system reacts particularly sensitively to the introduction
of toxic and poorly degradable substances.
There have recently been some proposals for reducing these latter
problems. For example, the US Patent Specifications 4,374,737 and
4,481,121 disclose oil-based invert-drilling fluids in which non-
polluting oils are to be used. The following can be mentioned together
as of equal value as non-polluting oils: mineral oil fractions which
are free from aromatics and vegetable oils, such as peanut oil, '
soybean oil, linseed oil, worn oil, rice oil or even oils of animal
origin, such as whale oil. These named ester oils of vegetable and
animal origin are all, without exception, triglycerides of natural
fatty acids, which are known to have high environmental acceptability
and are clearly superior from the evological point of view to
hydrocarbon fractions - even when these cb not contain aromatic
hydrocarbons.
In the above US Patent Specifications, however, not one oonc~ete
example describes the use of such natural ester oils in invert drilling
fluids. Without exception, mineral oil fractions are used as the
continuous oil-phase. In fact, oils of vegetable and/or animal origin
of the type mentioned here are not considered for invert drilling
fluids for practical reasons. The Theological properties of such oil
phases cannot be controlled over the wide temperature range generally
required in practice, from 0 to 5°C on the one hand, up to 250°C
and
more on the other.
The ALplicant's other proposals
A series of publications and co-pending Canadian Applications by
the Applicant describe the use of easily biodegradable and
ecologically harmless ester oils as the continuous oil phase in
W/O-invert drilling mud systems. Refer here in particular to the
publications DE 38 42 659 and DE 38 42 703 and the modifications
of the ester oils that can be used according to the details of
2058636
-5-
the co-pending Canadian Applications 2,047,697, filed March 1, 1990
and 2,047,706, filed March 1, 1990 (DE 39 07 391 and DE 39 07 392).
The subject of these co-pending Applications is the use of ester
oils based on selected monocarboxylic acids and monocarboxylic acid
mixtures and monofunctional and optionally polyfunctional alcohols
as the continuous oil phase in W/O-invert systems. The co-pending
Applications show that, using the esters and ester mixtures
disclosed therein, not only can satisfactory Theological properties
be established in the fresh drilling fluid, but it is also possible
by the additional use of selected, known alkali reserves in the
drilling fluid, for work to be carried out without fearing
undesired thickening effects when there is a partial ester
hydrolysis.
An important further development of such invert drilling fluids
based on ester oils is the subject of the Applicant's co-pending
Canadian Application 2,009,689, filed February 9, 1990 (DE 39 03
785).
The teaching of this co-pending Application starts with the concept
of also using a further additive in invert drilling fluids based on
ester oils which is suitable for keeping the desired Theological
data of the drilling fluid in the required range, even when in
practice larger and larger amounts of free carboxylic acids are
formed by partial ester hydrolysis. The co-pending Application
provides for the additional use of basic amine compounds, which are
capable of forming salts with carboxylic acids and have a marked
oleophilic nature and at most limited water-solubility, as
additives in the oil phase.
The invention~roblem and its technical solution
The present invention starts with the problem of providing
drilling mud systems of the highest, and in this form
previously unknown, ecological acceptability which
simultaneously have good application properties and which
also in particular enable satisfactory application in problem
areas. In the invention a conscious decision has therefore
been made to reject the oil-based type of invert drilling mud
systems and to return to the oil-modified water-based type of
O/W-emulsion systems. The auxiliary agents described in the
cited co-pending Applications and Publications of the
~~~8636
- 6 -
Applicant, and the ecological advantages associated theres~rith, are now,
however, also to be used in this class of drilling mud systems.
In a first embodiment, the aim of the invention is therefore to make
use of the advantages that O/W-emulsion mud systeqns have against purely
water-based drilling fluids, but at the same time to replace the
mineral-oil phase at least to a substantial amount - preferably
co~pletely - with ecologically harmless ester oils.
In a further approach, the invention aims also to reduce the ecological
concerns of the second problem area, i.e. that associated with the
additives and auxiliary agents in drilling fluids, by selecting fran
the wide range of additives known in this field, at least to a large
extent and preferably in all cases, those auxiliary agents which are
distinguished by their ecologically harmless nature.
The subject of the invention is accordingly in a first embodiment the
use of water-emulsifiable esters which are fluid and/or at least
plastically deformable at working temperature and have flash points of
at least 80°C, frown saturated and/or unsaturated carboxylic acids with
up to 36 carbon atoms and mono- and/or polyhydric alcohols as at least
the predc~ninant constituent of the dispersed oil-phase of water-based
O/W-emulsion drilling fluids, which are suitable for an envi.rornrentally
friendly develapnent of geological formations, and, if desired, contain
insoluble, finely particulate weighting agents for the formation of
water-based O/W-e~lsion drilling mode and/or further additives, such
as emulsifiers, fluid-loss additives, wetting agents, alkali reserves
and/or auxiliary substances for the inhibition of drilled crock with
high water-sensitivity.
In a further embodiment, the invention relates to water-based O/W-
emulsion drilling fluids, which in a continuous aqueous phase contain,
in stable dispersion, an oil phase in amounts of about 5 to 50 % by
weight - the percentage by weight referred to the sum of the unweighted
water phase and oil phase - together, if required, with dissolved
and/or dispersed auxiliary substances of the type mentioned and are
characterized in that at least the largest part of the dispersed oil
phase is formed by water-emulsifiable ester oils which are fluid or at
;r , _
205866
_,-
least plastically deforznable at working temperature, and have flash
points of at least 80oC, from saturated and/or unsaturated carboxylic
acids with up to 36 carbon atoms and mono- and/or polyfunctional
alcohols.
Both embodiments of the teaching according to the invention include the
additional preferred step of also using for the water-based emulsion
drilling fluids or emulsion drilling mode, at least to a large extent,
those inorganic and/or organic auxiliary and loading substances which
are at least predominantly ecologically and toxicologically harmless.
And thus, for example, in the most important eqnbodiments of the
invention the use of auxiliary agents based on soluble, toxic heavy-
metal compounds is awided.
The preferred embodiments of the invention
The mixture ratios of the ester oil/water phases cover the usual range
for the previously lazaan O/W-emulsion drilling fluids based on mineral
oils. The lower limit values for the oil phase are usually at least
about 5 % by weight, or preferably between about 5 and 10 % by weight,
e.g., therefore 7 or 8 % by weight - each percentage by weight referred
to the total weight of the fluid phases ester oil + water, each in the
unweighted state. Minim~un amounts of the order given ensure that use
can be made of the characteristic peculiarities of an O/W-emulsion
fluid. The upper limit value for the oil content is usually about 50 %
by weight or even slightly higher, e.g., a maximum of about 65 % by
weight. Assuming that the droplet size of the dispersed oil phase is
sufficiently even, the range with the most dense packing is therefore
already achieved, and thus conversion into the fluid type of the W/0-
invert fluids is obvious or appears logical.
The upper limit for the ester~il content in the O/W-fluids according
to the invention is generally determined by oost/benefit considerations
and is, for exanple, about 45 % by weight, preferably less, e.g., about
40 % by weight.
An ester-oil amount from about 10 to 40 % by weight - percentage by
weight calculated ae before - and in particular amounts of the ester
~~58636
_8-
oil fran about 15 to 35 % by weight facilitate the exploitation of many
- lmown and not previously described - advantages of such emulsion
fluids. Oil contents of, for example, 20 % by weight, or in an extreme
case, 30 % by weight provide the basis of high-quality drilling fluids
which approach, at least very closely, the oil-based invert fluids in
the way they function, but require very much less ester~il phase.
The definition of the ester oils used acoordinQ to the invention
The following general considerations apply initially for the selection
and adaptation of the estex oils for each application:
The ester oils should be fluid at ambient temperature, but also under
their conditions of use, with the range of materials thought to be
fluid, however, also including materials which are at least plastically
deformable at ambient t~rQerature and which soften to became fluid at
the usually high working tett~eratures. For reasons of easier
processability, ester oils with solidification values (pour point and
setting point) below 10°C and usefully below OoC are preferred in
practice. Corresponding ester oils with solidification values not
above -5°C can be particularly suitable. One should take into account
here the fact that the drilling fluids are usually produced on site
using, for example, sea water at va~paratively low water-temperatures.
For reasons of industrial safety, it must be a requirement that the
ester oils have flash points of at least 80°C, fir, higher flash
points of at least 100°C and substantially higher values are preferred,
for example, those above 150 or 160 °C.
A further important requirement for the optimal employment of the
subject of the invention is that the ester oils have a biologically or
ecologically acceptable constitution, i.e. in particular are free from
undesired toxic constituents. In the preferred embodiment of the
invention, ester oils are accordingly used which are free from araratic
constituents and in particular have saturated and/or olefin-
unsaturated, straight-chain and/or branched hydrocarbon chains. The
use of oa~onents containing cycloaliphatic structural constituents is
possible from ecological points of view, but for reasons of cost will
y .... ..
205636
_ g -
be of less significance in practice.
Carboxylic acid esters of the type in question here are subject to a
limited degree, as the highly dispersed oil-phase in a continuous
aqueous phase, to hydrolytic ester-cleavage with liberation of the
ester-forming constituents carboxylic acid and alvohol. ~ closely
linked issues should be taken into account as regards the application
properties of the ester oils in the sense of the invention, namely
vonsiderations of the possible toxicity of the liberated components, in
particular of the alcohol ca~onents, when inhaled and also the change
in the oo~c~osition of the emulsion fluid and any associated change
which may take place in its application properties.
For oa~rehension of the teaching according to the invention, these
considerations should be examined separately for each of the ester-
forming basic constituents - on the one hand the aloohols and on the
other the carboxylic acids.
According to the invention, both m~nohydric alcohols and polyhydric
alcohols are suitable as the ester-forming alcohol components, and any
mixtures of these types can also be used. A further distinction can be
made between alaohols acvordi.ng to their solubility behavior in water.
The aloohols can be water-soluble and/or water-insoluble.
In a first group, polyhyriric alcohols are to be considered.
Particularly preferred here are the industrially easily available
la~w~er, polyfunctional aloohols with 2 to 5, preferably 2 to 4 hydroxyl
groups and in particular 2 to 6 carbon atoms, which forni esters with a
suitable rheology.
Characteristic representatives are ethylene glycol, the prnpanediols
and particularly glycerin.
Polyhydric alcohols of the type referred to here are distinguished by
high water-solubility and at the same time by such low volatilization
values that considerations of the exclusion of toxic hazards when
inhaled cb not usually apply.
205636
- 10 -
Polyhydric lower aloohols of the type referred to here can be used as
totally esterified oil oo~ponents and/or as partial esters with some
free hydroxyl groups and/or can be formed in the practical use of the
emulsion fluid according to the invention. Provided that the partial
esters formed retain the at least largely water-insoluble character of
the oil phase, no substantial change takes place as regards the
oil/water ratio in the emulsion fluid. The situation is only different
when water-soluble hydrolysis products form - in particular therefore
the free lower polyhydric aloohols. The changes which occur in
practical operation in such emulsion fluids as a result of this process
are, however, insignificant. Firstly, a oc~g~aratively high stability
of the ester bond is ensured under the working conditions according to
the invention. O/W-emulsion fluids are known to operate usually in the
pH-range of approx. neutral to moderately alkaline, for example, in the
pH-range of about 7.2 to 11 and in particular about 7.5 to 10.5, and
thus for these reasons alone there is no aggressive hydirolytic attack
on the ester bond. In addition, and moreover, the following is in
particular also true:
In the practical use of the drilling fluid, and the associated driving
forward of the bore into ever deeper earth strata, there is a continual
consumption of the drilling fluid and in particular of the oil-phase
used in the drilling fluid. ~ulsion fluids are knaan - and this is an
i~ortant point of value in their use - for the fact that the
emulsified oil phase clings on to solid surfaces and therefore both
seals the filter bed to the wall of the bore shaft and hinders, or even
prevents, interaction between the drilled rock and the aqueous phase of
the drilling fluid. This continual consumption of drilling fluid, and
in particular of the oil-phase necessitates a continual supply of oil-
based mud. In practical operation, a state of equilibrium is therefore
rapidly established in the drilling fluid which prevails for long
periods of time facilitates a oontin~us operation.
Fmm acme viewpoints, further considerations should be taken into
account when monohydric aloohols are used in the ester oils. Here only
the lamer representatives of these alvohols are water-soluble or, in an
unlimited quantity, water-miscible. In addition, however, volatility
is a nat unimportant consideration in the case of these alcohols. In
- m - I 2058636
the practical operation of a bore, at least moderately increased
temperatures are rapidly established in the circulated drilling fluid
and therefore the parts exposed by the ping to remove the drill
cuttings have a temperature, for exanple, in the range of 50 to 70 °C.
Considerations of toxicological effects when inhaled must therefore be
taken into account here. Even C4-aloohols, e.g.; isobutyl alcohol; can
be so volatile under the operating conditions on the drilling platform
that hazards to personnel must be taken into account. According to the
invention, therefore, when ester oils are employed together with
moryohydric alcohols, the lamer carbon number limit for these monohydric
alcohols is preferably selected as 6, and working with esters of
monofunctional alvohols with at least 8 carbon atoms can be
particularly preferred.
The selection and limitation of the carbon number in the ester-forming
alcohol, hvw~ever, at the same time has the follc~aing result as regards
the oo~r~osition of the ester-oil phase when there is a partial
hydrolysis during operation: The hydrolyzing parts of such ester oils
r are converted to the free alcohol which remains as a practically water-
insoluble mixture constituent in the dispersed ester-oil phase. This
can bring about quite specific advantages for the functionability of
the dispersed oil phase. Oil-based invert drilling- mud systems based
on flowable, in particular monofunctional, alcohols with high
ecological acceptability are disclosed in the Applicant's co-
pending Canadian Application 2,051,624, filed March 29, 1990 (DE
39 11 238). The use of these alcohols as a material for O/W-
emulsion fluids of the type comparable to that in the present
invention is the subject of the co-pending Application by the
Applicant. To this extent the teaching of the invention is
connected with that of the co-pending Application and therefore
this need not be dealt with in any further detail here.
Essentially, however, the above consideration also applies here, i.e.
that in practical use a quasi-static state adjusts rapidly through
equilibrium forn~ation in the cocrposition of the ester-oil phase which
is characterized by large contents of non-hydrolyzed ester oil.
A number of points must also be considered with regard to the
carboxylic acids formed by the partial hydrolysis of the ester oil
2058~3~
- 12 -
fluid.
Here it is possible, depending on the specific constitution of the
carboxylic acids used, to distinguish between two basic types -
without there being a rigid transition between the tux: carboxylic
acids which give rise to carboxylic acid salts with an ~lsifier
effect, and those which give rise to inert salts.
The respective chain-length of the liberated carboxylic acid molecule
is in particular decisive here. Moreover, the salt-forming ration
usually present in the alkali reserves of the drilling fluid should
also be considered.
In general the following rules apply: Lower carboxylic acids, for
example those with 1 to 5 carbon atoms, give rise to the formation of
inert salts, for exanple, the formation of corresponding acetates or
propionates. Fatty acids of higher chain-length and in particular
those with frodn 12 to 24 carbon atoms result in o~OUnds with an
emulsifier effect.
By the selection of suitable ester oils - and to a certain extent also
the salt-forming rations in the emulsion fluid - the specific control
of the secondary products in the emulsion fluid is therefore possible,
which can also have considerable influence on the nature and effect of
the emulsion fluid. The above also applies here: It is not only the
dispersed organic phase, but also the aqueous phase, which is subject
to continual consumption in practice and thus requires replacement. In
stationary operation, therefore, rapidly controllable states of
equilibrium will be established, even with regard to the reaction by-
products based on the ester-forming carboxylic acids as discussed here.
General details of the definition of suitable ester oils
In the sense of the invention, the corresponding reaction products of
monocarboxylic acids with monofunctional and/or polyfunctional alcohols
of the type given are preferred as the ester oils. The additional use
of polyvalent carboxylic acids is not, haa~ever, excluded, but they are
of less significance, in particular for reasons of cost.
.~ 2~58~~~
- 13 -
The carboxylic acids here can be of natural and/or synthetic origin,
they are, as already indicated, preferably straight-chain and/or
branched and optionally cyclic, but not aromatic in structure. The
ester-forming carboxylic acids can be saturated and/or unsaturated,
with unsaturated compounds here being understood, in particular, to be
olefin-unsaturated compounds, which can be mono- but also poly-olefin-
unsaturated. Olefin-unsaturated components can be of particular
significance for adjusting the predetermined rheology values. It is
known that olefinic longer-chain ca~ounds are suitable as
corresponding saturated components for the forn~ation of esters with
lower melting points.
The preferred range for the carbon number of the carboxylic acids
extends from 1 to 36 and in particular from 2 to 36. For reasons of
easy availability, an upper limit for the carbon number can be about 22
to 24. The respective chain length of the ester-forming carboxylic acid
ca~onents is selected - depending on the nature of the alvohols
oomponent(s) used - by consideration of the various issues already
discussed, and refers not only, for example, to the ester and/or its
rheology directly, but also to the reaction by-products formed in
particular by partial hydrolysis.
Suitable aloohols are, as indicated, both monofunctional alcohols -
provided the above limitations are taken into consideration - and
polyfunctional alcohols, particularly lower polyfunctional alcohols
with 2 to 6 carbon atoms and preferably with a maxinsun of 4 hydroxyl
9m~
The alcohol oatponents here can also be of natural and/or synthetic
origin, they are straight-chain or branched and in particular in the
case of the monofunctional aloohols are saturated and/or also olefin-
unsaturated. Monofunctional alaohols have in particular up to 36
carbon atcms, preferably up to about 24 carbon atoms. Alcoh~ols with 6
to 18, in particular 7 to 15 carbon atoms, of natural and/or synthetic
origin can only be of particular significance in the formation of the
ester oils.
_ _--_ -~ f ~, . . _ ~: _ _ _~ .~___ . _
-~ ~ .... _ 14 _ 2058636
Particularly important ester oils in the sense of the use in the
invention are the ecologically-acceptable ester oils as described
in particular in the cited Publications and co-pending
Applications DE 38 42 659, DE 38 42 703, 2,047,697 (DE 39 07 391)
and 2,047,706 (DE 39 07 392). To complete the invention
disclosure, the essential characteristics of these ester oils or
ester mixtures are briefly summarized below.
The dispersed ester-oil phase accordingly contains carboxylic acid
esters from at least one of the following sub-classes:
a) Esters from C1_5-rrnnocarboxylic acids and mono- and/or
polyfunctional alcohols, in which radicals from monohydric
aloohols have at least 6, preferably at least 8 carbon atans, and
the polyhydric aloohols preferably have 2 to 6 carbon atoms in the
molecule,
b) esters fran monocarboxylic acids of synthetic and/or natural
origin with 6 to 16 carbon atoms, in particular esters of
corresponding aliphatic-saturated monocarboxylic acids and mono-
and/or polyfunctional alvohols of the type indicated under a),
c) esters of olefin mono- and/or poly-unsaturated monocarboxylic
acids with at least 16, in particular 16 to 24 carbons atoms, and
in particular m4nofunctional straight-chain and/or branched
aloohols.
The latter esters of olefinic mono- and/or poly-unsaturated
monocarboxylic acids with at least 16 carbon atans (c) are preferably
assigned to at least one of the following sub-classes:
cl) esters which are derived by rrore than 45 % by weight, preferably
by more than 55 % by weight frncn di- and/or poly~lefin-
unsaturated C16-24-~n~°xylic acids,
c2) esters which are derived by not more than 35 % frcm di- and poly-
olefin-unsaturated acids, and are preferably at least about 60 %
by weight mono-olefin-unsaturated.
The raw materials for obtaining many of the monocarboxylic acids in
these sub-classes, in particular those with a higher carbon number, are
-15 - ~ I 2058636
vegetable and/or animal oils. Coconut oil, palm kernel - oil and/or
babassu oil, can be mentioned in particular as materials used for
obtaining mc~nocarboxylic acids mainly in the range of up to 18 carbon
atat~s, and with essentially saturated components. ~anples of
vegetable ester oils, in particular for olefinic mono- and optionally
poly-unsaturated carboacylic acids with from 16 to 24 carbon atoms, are
palm oil, peanut oil, castor oil and in particular rapeseed oil.
Carboxylic acids of animal origin of this type are in particular
corresponding mixtures of fish oils, such as herring oil.
The teaching of the invention expressly includes also and in particular
the use of m~nocarboxylic acid triglyoerides and therefore in
particular also the use of corresponding glyceride oils of natural
origin. Here, haaever, the following must be considered: Natural oils
and fats usually occur in a form so highly contam;nated, for example,
with free carboxylic acids or other accompanying substances, that there
is as a rule no question of immediately processing them in O/W-emulsion
fluids of the type referred to here. If such natural materials are
added in the commercially available form to water-based drilling
fluids, then almost immediately, such a large aimunt of foam forms in
the drilling fluid being used as to constitute a serious hindrance or
even to result in the drilling fluid being unusable. This may not be
the case if cleaned and/or synthetically produced selected
triglyoerides are used in the dispersed oil phase. The teaching
according to the invention can be realized without exception with
these. In principle, ha~aever, with such esters of high-grade aloohols
one must always anticipate a not inconsiderable tendency towards foam
formation. Partial esters of glycerin - the mr~no- or di-glycerides -
are known to be effective emulsifier components.
As already indicated, it is not only the comparatively low-
viscosity ester oils as in the disclosure of the cited Publications
and co-pending Applications of the Applicant in the field of invert
drilling fluids which are based on ester-oils, which are suitable
for the purposes of the invention, but within the framework of O/W-
emulsion fluids, in particular comparatively viscous ester oils can
be of advantage as the dispersed phase. They are, for example,
valuable auxiliary agents for sealing the finest pores in the
filter cake of the bore shaft, or in rendering
gy
-16 - 2058636
inert swellable rack. The lubricating ability of such ester oils of
oatparatively high viscosity even at elevated te~eratures in the bore
shaft, and in particular also in deviated bore-holes, is in some cases
distinctly better than that of the comparatively low-viscosity ester
oils. A dispersed ester oil phase of catQaratively hick-viscosity
ester oils does not cause any detrimental effect on the drill-
technology, the rheology of the system as a whole is determined by the
continuous aqueous phase. In this sense it may be preferred to use
ester oils as the dispersed phase which have a Brookfield viscosity of
up to about 500,000 mPa.s or even higher, for ale, up to about 1
million mPa.s or even 2 million mPa.s (determined at roan te~perature).
This constitutes an important extension of the teaching in the noted
Publications and co-pending Applications of the Applicant in the
field of oil-based invert drilling fluids based on ester-oils.
In one cinbodiment of the invention, branched-chain oc~onents and in
particular alpha-branched-chain aloohols and/or carboxylic acids can be
of particular significance. Branches of this type are known on the one
hand to influence the rheology, the esters formed by such chain-
branching are usually more mobile. Moreover, such alpha-branching can,
however, also promote increased hydrolysis stability under working
conditions, this is therefore exploited in the invention.
The actueous phase
All types of water are suitable for the production of the O/W-e~tlsion
fluids according to the invention. These can therefore be based on
fresh water and in particular' also on salt water - particularly sea
water for use in off-shore wells.
Additives in the emulsion fluid
In principle, all the additives used in co~~parable drilling fluid types
can be considered, which are usually added in ~nnection with a quite
specific desired range of drilling fluid properties. The additives can
be water-soluble, oil-soluble and/or water- or oil-dispersible.
Classical additives for water-based O/W-atwlsion fluids can be:
~0~863fi
- 17 -
emulsifiers, fluid-loss additives, structure-viscosity-building soluble
and/or insoluble substances, alkali reserves, agents for the inhibition
of undesired water-exchange between drilled formations - e.g. water-
swellable clays and/or salt strata - and the water-based drilling
fluid, wetting agents for better adhesion of the emulsified oil phase
to solid surfaces, e.g. for improving the lubricating effect, but also
for the improvement of the oleophilic seal of exposed rock formations,
or rock surfaces, disinfectants, e.g. for inhibiting bacterial attack
on such O/W-emulsions, and the like. For details, reference should be
made here to the relevant prior art, as described in detail in the
specialist literature cited above, refer here in particular to Gray and
barley, loc. cit., Chapter 11, "Drilling Fluid Co~c~onents". We will
therefore only cite extracts below:
Finely-dispersed additives for increasing the fluid density: Barium
sulfate (barite) is widely used, but also calcium carbonate (calcite)
or the mixed carbonate of calcium and magnesium (dolomite).
Agents for building up the structure-viscosity, which at the same time
also act as fluid-loss additives: Bentonite in particular should be
mentioned here which is kno~m to be used in water-based fluids in a
non-modified form and is therefore ecologically safe. For salt-water
fluids other oo~parable clays, in particular attapulgite and sepiolite,
are of considerable significance in practice.
The additional use of organic polymer ornpounds of natural and/or
synthetic origin can also be of considerable in~ortance in this
context. The following should in particular be mentioned here: starch
or chemically modified starches, cellulose derivative, such as
carboxymethylcellulose, guar gum, xanthan gum, or also purely synthetic
water-soluble and/or water-dispersible polymer oa~pounds, such as in
particular the polyacrylamide compounds of high molecular weight with
or without anionic or cationic modification.
Zhinners for viscosity-regulation: So-called thinners can be of
organic or inorganic nature; exanple of organic thinners are tannins
and/or quebracho extract. Further e~les are lignite arxi lignite
derivative, particularly lignosulfonates. As indicated above, in a
_ ___~_.._..:~...-.~.~ _ __.. . . _ _ _ _. ___
-18 - 2058636
preferred embodiment of the invention the use of toxic cutponents is
particularly to be excluded, and in particular the corresponding salts
with toxic heavy metals, such as chromium and/or copper. Polyphosphate
compounds are exiles of inorganic thinners:
Ffiulsifiers: For the teaching according to the invention, two features
in particular should be considered. It has emerged that a stable
dispersion of ester oils is very much more easily produced than the
corresponding dispersion of pure mineral oils as used in the state of
the art. This in itself is a first simplification. Furthermore, it
should be vonsidered that, when longer-chain carboxylic acid esters are
used, by the partial saponification of the ester oils under the
additional effect of suitable alkali reserves, effective O/W-
emulsifiere are also formed which contribute to the stabilization of
the system.
Additives which inhibit undesired water-exchange with, for example,
clays: The additives known from the state of the art for use in water-
based drilling fluids can be oonsi.dered here. In particular, halides
and/or carbonates of the alkali and/or alkaline-earth metals, with
particular importance given to corresponding patassiiun salts,
optionally in vatibination with lime. Reference is made for example to
the appropriate publications in "Petroleum Engineer International",
September 1987, 32 - 40 and "World Oil", Nov~ber 1983, 93 -97.
Alkali reserves: inorganic and/or orc~nic bases adapted to the total
behavior of the fluid can be considered, in particular corresponding
basic salts or hydroxides of alkali and/or alkaline-earth metals and
orcganic bases .
In the field of organic bases, a conceptual distinction must be drawn
between water-soluble orcganic bases - for example, compounds of the
diethanol~ine type - and practically water-insoluble bases of marked
oleophilic character as described in the Applicant's co-pending
Application 2,009,689 (DE 39 03 785) cited above as additives in
invert drilling muds based on ester oil. The use of such oil-
soluble bases in the framework of the present invention in
particular falls within the new teaching. Oleophilic bases of
this type, which are distinguished
-19 - 2058636
in particular by at least one longer hydrocarbon radical with, for
example, 8 to 36 carbon atoms, are, however, not dissolved in the
aqueous phase, but in the dispersed oil phase. Here these basic
oc~onents are of multiple significance. On the one hand they can act
immediately as alkali reserves. On the other, they give the dispersed
oil droplets a certain positive state of charge and therefore result in
increased interaction with the negative surface charges which can be
found in particular in the hyd~hilic clays which are capable of ion-
exchange. According to the invention one can thus influence the
hydrolytic cleavage and the oleophilic sealing of water-reactive rock
strata.
The quantity of auxiliary substances and additives used in each case
moves essentially within the usual boundaries and can therefore be
found in the cited relevant literature.
~sanples
Firstly, a 6% by weight harogenized bentonite suspension is prepared
using commercially available bentonite (not hydrophobized) and tap
water, and a pH value of 9.2 to 9.3 is adjusted by means of a sodium
hydroxide solution.
Starting with this pre-swollen aqueous bentonite phase, the individual '
components of the water-based ester-oil emulsion as in the 'following
formulation are incorporated in successive stages of the process - each
under intensive intermixing:
350 g 6 % by weight bentonite solution
rM
1.5 g industrial carboxymethylcellulose low-viscosity (gelatin U 300
S9)
35 g sodium chloride
70 g ester oil (according to the definition given below)
1.7 g emulsifier (sulf. castor oil "Turkey-red oil", unless otherwise
indicated)
219 g barite
Viscosity measurements are carried out on the thus pregared O/W-
2U58~35
- 20 -
emulsion fluids as follows:
Firstly, the plastic viscosity (PV), the yield point (YP) and the gel
strength after 10 sec. and after 10 min. of the emulsion fluid are
determined at 50°C on the unaged material.
The emulsion fluid is then aged for 16 hours at 125oC in an autoclave
in the so-called "roller-oven" to examine the effect of temperature on
the stability of the emulsion. Then the viscosity values at 50oC are
determined once again. In each of the following exanples the nature of
the ester oil used, details of the emulsifier, the values determined
for the unaged and aged material and - if necessary - general comments
are given.
Ele 1
Ester~il used: 2-ethylhexylester of a Cg_14-fatty acid mixture
(essentially saturated)
Turkey-red oil as the emulsifier
unaged aged
material material
plastic viscosity [mPa.s] 8 14
yield point [Pa] 19.2 13.4
gel strength [Pa]
sec. 13.4 9.6
10 min. 16.3 23.0
- 21 -
Example 2
The formulation in Example 1 is repeated, but without using the
emulsifier (Turkey-red oil).
The viscosity values measured on the unaged and aged material are as
follows:
unaged aged
material material
plastic viscosity [mPa.s] 11 10
yield point [Pa] 16.8 18.2
gel strength [Pa]
sec. 18.2 16.3
10 min. 35.9 24.0
Even in the fresh formulation a slight droplet
formation can be seen on
the surface, after ageing the solid substanceto settle.
tends
Exanple 3
Ester-oil used: Oleic-acid isobutylester
Emulsifier: Turkey-red oil
The viscosity values measured on the unagedaged drilling
and the fluid
are as follows:
unaged aged
material material
plastic viscosity [mPa.s] 11 13
yield point [Pa] 18.2 12.9
gel strength [Pa]
1
10 sec. 12.5 9.6
10 min. 15.8 18.7
. . ~ ~ - 22 - 205863b
~ple 4
The formulation in ale 3 is repeated, but now soybean lecithin
"N
(oa:mercial product: Drilltreed ) is used as the emulsifier in a
quantity of 1.7 g. The viscosity values measured on the unaged and
aced drilling f laid are as follows
unaged aged
material material
plastic viscosity [mPa.s] 11 12
yield point [Pa] 12.5 14.9
gel strength [Pa]
sec. 12.5 6.2
10 min. 8.6 16.3
~tanple 5
With Turkey-red oil as the e:rnulsifier, p~pylene-glyaolamno-cleats is
used as the ester oil. The following viscosity values are determined:
unaged aged
material material
plastic visvosity [mPa.s] 20 14
yield point [Pa] 20.1 16.3
gel strength [Pa]
10 sec. 15.8 12.5
10 min. 24.9 24.9
Fle 6
Again using Turkey-red oil as the emulsifier, a trimethylolpropane tri-
fatty-acid ester is used as the ester-oil phase. The values measured
for the unaged and aged material are as follows:
- 23 - 2058636
~g~ age _
material material
plastic viscosity [mPa.s] 15 16
yield point [Pa] 17.7 15.8
gel strength [Pa]
sec. 13.9 12.9
10 min. 20.6 23.0
le 7
In the context of the teaching of ale 6, a corresponding glycerin
tri-fatty-acid ester is used as the ester oil phase. The values
determined for the unaged and aged emulsion drilling fluid are as
follows:
unaged aged
material material
plastic viscosity [mPa.s] 13 12
yield point [Pa] 8.6 8.1
gel strength [Pa] '
10 sec. 8.6 6.2
10 min. 9.1 5.8
~anple 8
Using Turkey-red oil as the emulsifier, the residue, esterified with n-
hexanol, from the fatty-acid dimerization (monomer fatty acid Alip~hat~
47 ) is incorporated as the ester-oil phase. The viscosity values
determined for the unag~ed and aged material are as follows:
.~ . ~ ~~~8~3~
- 24 -
unaged aged
material material
plastic vis~sity [mPa.s] 14 16
yield pint [Pa] 17.2 14.4
gel strength [PaJ
sec. 12.0 9,1
10 min. 12.9 22.5
