Oleophilic alcohols as a constituent of invert drilling fluids

The use is described of PA0 a) mono- and/or polyfunctional alcohols of natural and/or synthetic origin which are at least largely water-insoluble and are fluid and pumpable in the temperature range of 0.degree. to 5.degree. C., or of PA0 b) solutions, fluid and pumpable in the given temperature range, in ecologically-acceptable water-insoluble oils, of at least largely water-insoluble mono- and/or polyfunctional alcohols of natural and/or synthetic origin, as the continuous oil phase of drilling fluids, which exist as W/O-emulsions, have a dispersed aqueous phase and preferably have further usual additives in the alcohol-containing oil phase, and which are suitable for the environment-friendly development of, e.g., petroleum and natural gas deposits. Drilling fluids of the above type are also described, which are characterized in that they contain as the continuous oil phase, or dissolved in ecologically-acceptable water-insoluble oils, an additive of at least largely water-insoluble mono- and/or polyfunctional alcohols, the oil phase in each case being fluid and pumpable in the temperature range of 0.degree. to 5.degree. C. and having flash points above 80.degree. C.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The invention discloses new drilling fluids and invert drilling muds based 
thereon, which are distinguished by high ecological acceptability and at 
the same time good storage and application properties. An important area 
of application for the new drilling fluid 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 industrially usable 
drilling fluids with high ecological acceptability. The use of the new 
drilling fluid systems has particular significance in the marine 
environment, but is not limited thereto. The new mud systems can be put to 
quite general use even in land-based drilling, for example, in geothermal 
wells, water bore-holes, in the drilling of geoscientific bores and in 
drilling for the mining industry. Here too it is essentially true that 
associated ecotoxic problems are substantially simplified by the 
ester-based drilling-oil fluids selected according to the invention. 
2. Discussion of Related Art 
Oil-base drilling fluids are generally used in the form of so-called 
invert-emulsion muds, which consist of a three-phase system: oil, water 
and finely particulate solids. These are preparations of the W/O-emulsion 
type, i.e. the aqueous phase is distributed as a heterogeneous fine 
dispersion in the continuous oil phase. A number of additives can be used 
to stabilize the system as a whole and to confer on it the desired 
application properties, particularly emulsifiers or emulsifier systems, 
weighting agents, fluid-loss additives, alkali reserves, viscosity 
regulators and the like. For details, refer, e.g., to the publication by 
P. A. Boyd et al., "New Base Oil Used in Low-Toxicity Oil Muds" Journal of 
Petroleum Technology, 1985, 137 to 142, and R. B. Bennett, "New Drilling 
Fluid Technology--Mineral Oil Mud" Journal of Petroleum Technology, 1984, 
975 to 981 and the literature cited therein. 
The importance of ester-based oil phases in reducing the problems created 
by such oil-base muds has been recognized for some time in the relevant 
field of technology. For example, U.S. Patent Specifications 4,374,737 and 
4,481,121 disclose oil-base drilling fluids in which non-polluting oils 
are to be used. The following are mentioned as of equal value as the 
non-polluting oils-mineral oil fractions which are free from aromatic 
hydrocarbons, and vegetable oils, such as peanut oil, soybean oil, linseed 
oil, corn 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 be of 
high environmental acceptability, and are clearly superior ecologically to 
hydrocarbon fractions--even when these do not contain aromatic 
hydrocarbons. 
Interestingly enough, however, not one of the examples in the above U.S. 
Patent Specifications describes the use of such natural ester oils in 
invert-drilling fluids of this type. In every case, mineral oil fractions 
are used as the continuous oil phase. Oils of vegetable and/or animal 
origin are not considered for practical reasons. The rheological 
properties of such oil phases cannot be controlled over the wide 
temperature range generally required in practice, from 0.degree. to 
5.degree. C. on the one hand, up to 250.degree. C. on the other. 
THE APPLICANT's EARLIER PROPOSALS 
Ester oils of the type in question do not in fact behave in the same way in 
practice as the previously used mineral oil fractions based on pure 
hydrocarbons. Ester oils are subject to partial hydrolysis in practical 
use, particularly in W/O-invert drilling muds. Free carboxylic acids are 
formed as a result. The Applicant's earlier Applications P 38 42 659.5 and 
P 38 42 703.6 U.S. Ser. Nos. 07/452,457 and 07/452,988 describe the 
problems caused thereby and give proposals for their solution. Further 
types of usable ester oils are disclosed in the earlier Patent 
Applications P 39 07 391.2 and P 39 07 392.0 (U.S. application Ser. No. 
07/752,694, filed Sep. 6, 1991, now abandoned and U.S. application Ser. 
No. 07/752,692, filed Sep. 6, 1991, now abandoned). 
The subject of these earlier Applications is the use of ester oils based on 
selected monocarboxylic acids or monocarboxylic acid mixtures and 
monofunctional, and optionally polyfunctional, alcohols. The earlier 
Applications show that, with the esters and ester mixtures they disclose, 
it is not only possible to invest fresh drilling fluid with satisfactory 
rheological properties, but it is also possible to use selected known 
alkali reserves in the drilling fluid and in this way to retard 
undesirable corrosion. As alkali reserves--particularly when ester oils 
based on carboxylic acids with at least 6 carbon atoms are used-calcium 
hydroxide, or lime, can be added and/or can be used with zinc oxide or 
comparable zinc compounds. In this case, however, an additional 
restriction is advisable. To prevent unwanted thickening of the oil-base 
invert mud system in practical use, the amount of alkalizing additive, and 
in particular the amount of lime, must be limited. The maximum amount 
permitted in the disclosure of the aforementioned earlier Applications is 
about 2 lb/bbl (pounds/barrel) of oil-base mud. 
An important further development of these invert-drilling fluids based on 
ester oils is the subject of the Applicant's earlier Application P 39 03 
785.1 U.S. Ser. No. 07/478,185. 
The teaching of this earlier Application is based on the concept of using a 
further additive in the invert drilling fluids based on ester oils, which 
is suited to keeping the desired rheological properties of the drilling 
fluid within the required range, even when ever larger amounts of free 
carboxylic acids are formed in use by partial ester hydrolysis. These 
liberated carboxylic acids should not only be caught in a harmless form, 
it should moreover be possible to convert these free carboxylic acids, 
preferably into valuable components with stabilizing or emulsifying 
properties for the whole system. According to this teaching, basic amine 
compounds of marked oleophilic nature and at most limited water 
solubility, which are capable of forming salts with carboxylic acids, can 
be used as additives in the oil phase. The oleophilic amine compounds can 
at the same time be used at least in part as alkali reserves in the invert 
drilling fluid, they can, however, also be used in combination with 
conventional alkali reserves, particularly together with lime. The use of 
oleophilic amine compounds which are at least largely free from aromatic 
constituents is preferred. In particular, optionally olefin-unsaturated 
aliphatic, cycloaliphatic and/or heterocyclic oleophilic basic amine 
compounds, can be considered, which contain one or more N-groups capable 
of forming salts with carboxylic acids. In a preferred embodiment the 
water-solubility at room temperature of these amine compounds is at most 
about 5% by weight and is most preferably below 1% by weight. 
Typical examples of such amine compounds are primary, secondary and/or 
tertiary amines, which are at least largely water-insoluble, and which can 
also to a limited extent be alkoxylated and/or substituted, particularly 
with hydroxyl groups. Further examples are the corresponding aminoamides 
and/or heterocyclic compounds with nitrogen as a ring constituent. For 
example, basic amine compounds are suitable which have at least one 
long-chain hydrocarbon radical, preferably of from 8 to 36 carbon atoms, 
particularly with 10 to 24 carbon atoms, which can also be olefin mono- or 
poly-unsaturated. The oleophilic basic amine compounds can be added to the 
drilling fluid in amounts of up to about 10 lb/bbl, preferably in amounts 
up to about 5 lb/bbl and particularly in the range of about 0.1 to 2 
lb/bbl. 
It has been found that the addition of such oleophilic basic amine 
compounds can effectively prevent thickening of the mud system, which 
presumably can be attributed to a disturbance of the W/O invert system and 
also to the formation of free carboxylic acids by ester hydrolysis.

THE INVENTION PROBLEM AND ITS TECHNICAL SOLUTION 
The problem of the present invention is further to develop systems of the 
type in question and in particular drilling fluids of high ecological 
acceptability. In a first embodiment the invention proposes to make 
available oils and oil mixtures for the production of drilling fluids 
based on W/O-emulsions, which can be used industrially and are easily 
accessible and at the same time are distinguished by high ecological 
acceptability. In a further embodiment the invention intends to make 
available additives for the aforementioned systems in question here which 
confer valuable additive properties on drilling fluids based on 
W/O-emulsions without having a disadvantageous effect on their ecological 
acceptability. 
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". 
The technical solution of the problems of the invention starts from the 
knowledge that selected alcohols suited to this use can result in new and 
improved drilling fluids of the type described. These alcohols are 
water-insoluble or essentially water-insoluble components, in particular 
therefore corresponding compounds with a pronounced oleophilic nature, 
which differ, however, from pure hydrocarbon compounds by the presence of 
the functional hydroxyl groups. As a result important technological 
improvements can be made and at the same time high ecological 
acceptability is ensured. Non-toxic hydrocarbon compounds with alcohol 
functions are known to be easily processed in the cycle of the living 
world. 
The subject of the invention, accordingly, in a first embodiment, is the 
use of 
a) mono- and/or poly-functional alcohols of natural and/or synthetic origin 
which are at least largely water-insoluble and are fluid and pumpable in 
the temperature range of 0.degree. to 5.degree. C. 
or of 
b) solutions, fluid and pumpable in the given temperature range, in 
ecologically-acceptable water-insoluble oils, of at least largely 
water-insoluble mono- and/or poly-functional alcohols of natural and/or 
synthetic origin 
as the continuous oil phase of drilling fluids, which exist as W/O 
emulsion, which have in the alcohol-containing oil phase a dispersed 
aqueous phase and preferably further usual additives, and which are 
suitable for the environmentally acceptable development of, for example, 
petroleum or natural gas deposits. 
In a further embodiment, the invention relates to invert drilling fluids, 
as described above, which are characterized in that they contain, as the 
continuous oil phase or dissolved in ecologically acceptable oils, and 
additive which consists at least predominantly of water-insoluble mono- 
and/or polyfunctional alcohols, such that the oil phase in each case is 
fluid and pumpable in the temperature range of 0.degree. to 5.degree. C. 
and has flash points above 80.degree. C. 
THE VARIOUS EMBODIMENTS OF THE INVENTION 
In a first embodiment the continuous oil phase of the invert drilling 
fluids is formed exclusively, or to by far the largest part, by the 
essentially water-insoluble and preferably markedly oleophilic alcohols. 
Understandably, the rheology of the alcohols used here must be suited to 
the technical requirements of the drilling fluids. Slight rheological 
adjustments are possible by adding small amounts of the diluents provided 
in this embodiment. In the case described here, in particular oil phases 
are considered, which are formed by more than 70% by weight, preferably by 
more than 80% by weight, and desirably exclusively, by the alcohols 
themselves. The general subject knowledge is applicable for the 
rheological requirements of such oils for use in drilling fluids, and this 
will be discussed again below. From the wide range of markedly oleophilic 
alcohols with in particular a straight-chain and/or branched-chain 
hydrocarbon structure, primary consideration is given here to the 
monofunctional alcohols with at least 6 or 7 carbon atoms, preferably with 
at least 8 carbon atoms, in which the possible upper limit for the number 
of carbon atoms is greatly influenced by the structure of the hydrocarbon 
radical. The rheology of branched-chain and/or unsaturated alcohols of the 
type in question here is known to satisfy the requirements of flowability 
and pumpability, even at lower temperatures, more easily than a 
straight-chain saturated hydrocarbon structure. Saturated straight-chain 
fatty-alcohols with from 16-18 carbon atoms are known to have high 
solidification ranges around 50.degree. C., while the olefin unsaturated 
oleylalcohol solidifies below 4.degree. C. Branched alcohols of the same 
carbon-number range can--depending on the extent and degree of 
branching--constitute completely acceptable fluid and pumpable oil phases 
in the sense of the invention. In the field of saturated monofunctional 
alcohols, the range with low numbers of carbon atoms is particularly 
suitable, particularly therefore those with from about 8 to 14 carbon 
atoms, and here too the branched-chain alcohols can have rheological 
advantages. 
The oil-mixture components optionally used in small amounts in this 
embodiment can be pure hydrocarbon compounds especially those free from 
aromatic hydrocarbons, in particular selected ester oils of the type 
described in the Applicant's earlier Applications mentioned above. 
The rheological properties of the alcohol components used according to the 
invention become less and less important, the greater the proportion of 
these mixture constituents in the admixture with one or more oil 
components. A second embodiment of the invention relates accordingly to 
the use of oil phases in systems of the type in question which still have 
considerable or even predominant amounts of non-water-miscible oils which 
are used in admixture with the markedly oleophilic alcohols provided 
according to the invention. The content of the alcohols selected according 
to the invention in this embodiment is as a rule more than 10% by weight 
and up to about 70% by weight--each referred to the fluid oil 
phase--alcohol fractions in amounts of at least about 35% by weight and 
preferably of at least about 50% by weight of the oil phase may be 
preferred. The rheology of such systems is already determined to a very 
great extent by the nature of the compounds used as mixture components. It 
will, however, also be shown that the use of alcohols as provided for in 
the invention can also have considerable practical significance for these 
embodiments. 
As the mixture components for this second embodiment of the invention, 
there can again be considered both pure hydrocarbon oils, particularly 
those free from aromatic hydrocarbons, and especially ester oils of the 
type described in earlier Applications by the Applicant. Admixtures of 
these types also fall within the framework of the invention, with both 
admixtures of ester oils with pure hydrocarbon compounds and mixtures of 
various ester oil types possible for use as mixture components for general 
application with the oleophilic alcohols. In preferred embodiments of the 
invention, the pure hydrocarbon oils with no functional groups at all are 
used in the oil phase in amounts of at most 50% by weight, preferably of 
at most about 35% by weight and particularly in amounts of at most about 
25% by weight--each referred to the oil phase. In the most important 
embodiments of the variants described here, mixtures of the alcohols and 
ester oils defined according to the invention are used as the oil phase 
without the addition of pure hydrocarbon compounds. 
The invention finally relates in a third variant to the use of practically 
water-insoluble alcohols with a particularly marked oleophilic character 
as additives in the oil phase of the aforementioned drilling fluids based 
on W/O-emulsions. The amount of alcohols used according to the invention 
is generally in the range of about 0.1 to a maximum of 10% by weight, 
preferably in the range of about 1 to 5% by weight of the oil phase. The 
range of suitable water-insoluble alcohols can understandably be enlarged 
substantially in this embodiment. The rheology of the system as a whole is 
no longer determined here by the rheological values of the alcohol. It is 
in this embodiment that the use of the alcohols defined according to the 
invention as additives achieves important improvements in the behavior of 
drilling fluids of the aforementioned type. 
This is true in particular for invert systems in which the main component 
of the continuous oil phase is formed exclusively or primarily by ester 
oils of the type described in the above earlier Applications of the 
Applicant. In the embodiment in question here, the oil phase is 
constituted accordingly by at least 25% by weight, preferably by at least 
50% by weight and particularly by at least about 75 to 80% by weight of 
the oil phase, by aster oil as the main component. Pure hydrocarbon oils 
of the prior art can be used for the rest of the oil phase, it is however 
advantageous to dispense with them altogether. 
By adding to the invert systems the water-insoluble alcohols defined 
according to the invention, important improvements can be achieved in the 
practical use of the drilling fluids. The following 4 aspects are 
particularly affected: reduction of the fluid-loss values, the 
facilitation and improvement of the emulsification of the dispersed 
aqueous phase, in some cases clearly improved lubrification by the 
drilling fluid and in some cases a distinct improvement in the rheological 
properties of invert drilling fluids based on ester oils. 
The Alcohol Components Used According to the Invention 
The use of the alcohols as the oil phase, but also their combination as a 
lesser or greater part in the oil phase, requires these alcohol components 
to have adequate water-insolubility. The water-solubility of suitable 
alcohols at room temperature preferably lies below 5% by weight, 
particularly under 1% by weight and preferably not more than about 0.5% by 
weight. 
The following general rules apply for the chemical nature of the alcohols: 
Monofunctional and/or polyfunctional alcohols are suitable, provided that 
the oleophilic character of the alcoholic components is safeguarded. In 
particular, difunctional compounds and/or partial ethers of polyfunctional 
alcohols with at least one free hydroxyl group can be considered in 
addition to the monofunctional alcohols. The alcohols themselves should be 
ecologically acceptable and accordingly in the preferred embodiment should 
have no aromatic constituents. Straight-chain and/or branched aliphatic or 
also corresponding unsaturated, particularly olefin mono- and/or 
poly-unsaturated, alcohols are the preferred compounds. Cycloaliphatic 
alcohols can also be considered. 
An important general requirement in the sense of the invention is that 
these alcohols as such are not only ecologically acceptable, but also do 
not initiate any other toxicological risks, particularly by inhalation. 
Alcohols with a marked oleophilic nature, as required according to the 
invention, are in any case usually distinguished by such a low volatility 
that this requirement is satisfied without any problem. 
The following should also be noted for the admixture of the alcohols used 
in the invention with ester oils: The free alcohols used according to the 
invention can be the same as or different from the alcohol components 
employed in the ester oil. While the alcohol component in the ester oils 
is determined, for example, by considerations of the rheology of the ester 
oil and/or of the availability of the ester-forming alcohols, the use of 
the free alcohols as in the invention is proposed in order to achieve the 
desired improvements in the invert drilling fluid. 
If the alcohols are used as at least a substantial part, as the major part 
of even as the only compound in the oil phase, then the alcohols should be 
fluid and pumpable at lower temperature, particularly in the range of 
0.degree. to 5.degree. C., it should be possible for them to be liquefied 
to the flowable phase with the limited amounts of ecologically acceptable 
mixture components. The solidification values of such oil phases (pour 
point and setting point) should be below 0.degree. C., preferably below 
-5.degree. C. and particularly below -10.degree. C. The alcohols 
themselves should have flash points of at least 80.degree. C., preferably 
of at least 100.degree. C. a of at least 120.degree. C. In addition to the 
already mentioned monofunctional alcohols with at least 8 carbon atoms and 
of an upper carbon number determined by their structure and rheological 
requirements, selected polyols or their partial ethers can also be 
considered. Suitable polyols are in particular optionally branched-chain 
diols with a sufficient content of the oleophilic hydrocarbon radical in 
the molecule. Suitable examples are oleophilic diols with hydroxyl groups 
in the alpha,omega-position and/or diols which have their hydroxyl groups 
on adjacent carbon atoms. Characteristic examples of compounds of this 
type are 2,2-dimethyl-1,3-propanediol (neopentylglycol) or the 
saponification products of epoxidized olefins. Partial ethers of such 
diols with monofunctional alcohols, however, are also particularly to be 
considered. 
Particularly in the embodiments in which the rheology of the system as a 
whole is determined primarily by the water-insoluble mixture components, 
thus particularly by the ester oils, there is increasing freedom in the 
choice of suitable alcohol components. Among others, at least largely 
water-insoluble polyalkyleneglycolethers or corresponding mixed ethers of 
lower alkyleneglycols have proved to be usable additives here. For 
example, corresponding mixed ethers of ethylene oxide and propylene oxide 
are also usable additives in the sense of the invention if they reach 
molecular weights of, e.g. 5000, and show sufficient water-insolubility in 
the system as a whole. Compounds of the latter type are particularly 
important in the embodiment, the subject of which is the addition of the 
water-insoluble alcohols as additives in an amount of a maximum of about 
10% by weight. 
In an important embodiment of the invention, water-insoluble alcohols are 
used which are themselves free from basic amino groups and also preferably 
do not contain any other reactive groups, e.g. carboxyl groups. 
THE MIXTURE COMPONENTS IN THE OIL PHASE 
Suitable oil components for the admixture according to the invention are 
the mineral oils currently used in drilling fluids, and preferably 
aliphatic and/or cycloaliphatic hydrocarbon fractions essentially free 
from aromatic hydrocarbons, with the required rheological properties. 
Refer here to the prior-art publications cited above and the available 
commercial products. 
Particularly important mixture components, however, are ester oils which 
are ecologically acceptable as used in the invention, as described in 
particular in the aforementioned earlier Applications P 38 42 659.5, P 38 
42.703.6, P 39 07 391.2 and P 39 07 392.0. U.S. Ser. Nos. 07/452,457, 
07/452,988 U.S. application Ser. No. 07/752,694, filed Sep. 6 1991, now 
abandoned and U.S. application Ser. No. 07/752,692, filed Sep. 6, 1991, 
now abandoned. To complete the invention disclosure, the essential 
characteristics of these esters, or ester mixtures, are now briefly 
summarized. 
In a first embodiment, as the oil phase, esters (fluid and pumpable in the 
temperature range of 0.degree. to 5.degree. C.) are used of monofunctional 
alcohols with from 2 to 12, particularly with from 6 to 12, carbon atoms 
and aliphatic-saturated monocarboxylic acids with from 12 to 16 carbon 
atoms, or an admixture thereof with at most about the same amounts of 
other monocarboxylic acids. Ester oils are preferred here which are based, 
to at least about 60% by weight--referred to the respective carboxylic 
acid mixture--on esters of aliphatic C.sub.12-14 -monocarboxylic acids, 
the remaining percentage preferably being based on smaller amounts of 
shorter-chain aliphatic and/or longer-chain, in particular olefin mono- or 
poly-unsaturated, monocarboxylic acids. Esters are preferably used which 
in the temperature range of 0.degree. to 5.degree. C. have a Brookfield 
(RVT) viscosity of not above 50 mPa.s, preferably not above 40 mPa.s and 
particularly of at most about 30 mPa.s. The esters used in the drilling 
mud have solidification values (pour and setting point) below -10.degree. 
C., preferably below -15.degree. C. and at the same time have flash points 
above 100.degree. C., preferably above 150.degree. C. The carboxylic acids 
present in the ester or ester mixture are straight-chain and/or branched, 
and are of vegetable and/or synthetic origin. They can be derived from the 
corresponding triglycerides, such as coconut oil, palm kernel oil and/or 
babassu oil. The alcohol radicals of the esters used are derived in 
particular from straight-chain and/or branched saturated alcohols, 
preferably with from 6 to 10 carbon atoms. These alcohol components can 
also be of vegetable and/or animal origin and can thus be obtained by the 
reductive hydrogenation of the corresponding carboxylic acid esters. 
A further class of particularly suitable ester oils is derived from olefin 
mono- and/or poly-unsaturated monocarboxylic acids with 16 to 24 carbon 
atoms or their admixtures with smaller amounts of other, particularly 
saturated, monocarboxylic acids and monofunctional alcohols with 
preferably from 6 to 12 carbon atoms. These ester oils are also fluid and 
pumpable in the temperature range of 0.degree. to 5.degree. C. In 
particular those esters are suitable which are derived, by more than 70% 
by weight, preferably by more than 80% by weight and in particular by more 
than 90% by weight, from olefin-unsaturated carboxylic acids with from 16 
to 24 carbon atoms. 
Here too, the solidification values (pour and setting point) lie below 
-10.degree. C., preferably below -15.degree. C., while the flash points 
lie above 100.degree. C. and preferably above 160.degree. C. In the 
temperature range of 0.degree. to 5.degree. C., the esters used in the 
drilling mud have a Brookfield (RVT) viscosity of not more than 55 mPa.s, 
preferably not more than 45 mPa.s. 
Two subclasses can be defined for the ester oils of the type in question. 
In the first, the unsaturated C.sub.16-24 -monocarboxylic acid radicals 
present in the ester are derived by not more than 35% by weight from 
olefin di- and poly-unsaturated acids, with preferably at least about 60% 
by weight of the acid radicals being olefin monounsaturated. In the second 
embodiment, the C.sub.16-24 -monocarboxylic acids present in the ester 
mixture are derived, by more than 45% by weight, preferably by more than 
55% by weight, from olefin di- and/or polyunsaturated acids. It is 
desirable for the saturated carboxylic acids with from 16 to 18 carbon 
atoms, which are present in the ester mixture, to amount to not more than 
about 20% by weight and in particular not more than about 10% by weight. 
Preferably, saturated carboxylic acid esters, however, have lower numbers 
of carbon atoms in the acid radicals. The carboxylic acid radicals present 
can be of vegetable and/or animal origin. Examples of vegetable raw 
materials are, for example, palm oil, peanut oil, castor oil and in 
particular rapeseed oil. The carboxylic acids of animal origin are in 
particular the corresponding mixtures of fish oils, such as herring oil. 
A further interesting class of ester oils which can be used as mixture 
components for the use according to the invention, are esters which are 
fluid at room temperature and have flash points above 80.degree. C., from 
C.sub.1-5 -monocarboxylic acids and mono- and/or polyfunctional alcohols, 
which are preferably also fluid and pumpable in the temperature range of 
0.degree. to 5.degree. C. Particularly suitable are the corresponding 
esters of these lower carboxylic acids with monofunctional alcohols with 
at least 8 carbon atoms and/or esters of these acids with di- to 
tetra-hydric alcohols with preferably 2 to 6 carbon atoms. Acetic acid in 
particular is suitable for practical reasons as the ester-forming acid 
component in this class. The specifications for the rheology and 
volatility and the solidification values of the preferred esters in this 
sub-class correspond to the values given above. 
From this sub-class, the suitable mixture components are, in particular, 
esters from monofunctional alcohols of natural and/or synthetic origin, 
the chain length of which in the presence of predominantly 
aliphatic-unsaturated alcohols can be in the range of 8 to 15 carbon 
atoms, but in the case of olefin mono- and polyunsaturated alcohols, can 
also consist of higher numbers of carbon atoms, for example, up to about 
24 carbon atoms. Details can be found in the Applicant's earlier Patent 
Application P 39 07 391.2 (U.S. application Ser. No. 07/752,694, filed 
Sep. 6, 1991, now abandoned). 
Suitable mixture components are finally, however, the esters, as described 
in the co-pending Application P 39 07 392.0 (U.S. application Ser. No. 
07/752,692, filed Sep. 6, 1991, now abandoned), from monocarboxylic acids 
of synthetic and/or natural origin with from 6 to 11 carbon atoms and 
mono- and/or polyfunctional alcohols, which are preferably also fluid and 
pumpable in the temperature range of 0.degree. to 5.degree. C. To complete 
the invention disclosure, reference is made here to this extent to the 
above co-pending Application, the contents of which are hereby also made 
subject of the present disclosure. 
Multi-substance mixtures fall within the scope of the invention which, 
together with the alcohols defined according to the invention, can contain 
one or more of the mixture components listed here individually. 
Essentially any mixtures can be used provided that they fulfil the basic 
rheological requirements for invert drilling fluids of the type referred 
to here. Examples of such multi-component mixtures are materials based on 
various types of ester oils or also substance mixtures additionally 
containing mineral oil. 
FURTHER MIXTURE COMPONENTS OF THE INVERT DRILLING FLUID 
These may be any of the usual mixture components for conditioning and for 
the practical use of invert drilling muds, such as are used currently when 
mineral oils provide the continuous oil phase. In addition to the 
dispersed aqueous phase, in particular emulsifiers, weighting agents, 
fluid-loss additives, viscosifiers and alkali reserves can be considered. 
In an important embodiment of the invention, oleophilic basic amine 
compounds are used as additives together with the ester oils, these amine 
compounds are described in detail in the aforementioned earlier 
Application P 39 03 785.1 U.S. Ser. No. 07/478,185 of the Applicant. For 
details reference should be made to the disclosure of this earlier 
Application, as described above. 
If ester oils are used as mixture components in the scope of the 
invention--in particular ester oils based on carboxylic acids with at 
least 6 carbon atoms--it can be advantageous not to employ significant 
amounts of strongly hydrophilic inorganic or organic bases in the oil-base 
fluid. Lime can be used effectively as an alkali reserve, in which case it 
is advantageous to limit the maximum amount of lime to be used to about 2 
lb/bbl, and it may be preferred to work with a drilling-mud lime content 
slightly below this figure, e.g. from about 1 to 1.8 lb/bbl (lime/drilling 
fluid). Other known alkali reserves can be used in addition to, or in 
place of, the lime. The less basic metal oxides, such as zinc oxide, 
should particularly be mentioned. Even when these "acid traps" are used, 
care should still be taken to ensure that the amounts used are not too 
large, so as to prevent undesired premature ageing of the drilling fluid, 
which is associated with an increase in viscosity and therefore a 
deterioration in the rheological properties. The special features 
discussed here of the use according to the invention prevent, or at least 
restrict, the formation of undesirable amounts of highly active 
O/W-emulsifiers so that good rheological properties are maintained in 
practice for a sufficient period of time even when there is thermal 
ageing. 
The following also applies: 
Invert-drilling muds of the type being considered usually contain, together 
with the continuous oil phase, a finely dispersed aqueous phase in amounts 
from about 5 to 45% by weight and preferably from about 5 to 25% by 
weight. A dispersed aqueous phase from about 10 to 25% by weight can be 
regarded as particularly useful. 
The following rheological data apply for the rheology of the preferred 
invert drilling muds according to the invention: plastic viscosity (PV) 
from about 10 to 60 mPa.s, preferably from about 15 to 40 mPa.s; yield 
point (YP) in the range from about 5 to 40 lb/100 ft.sup.2, preferably 
from about 10 to 25 lb/100 ft.sup.2 -each measured at 50.degree. C. 
Further details on the measurement of these parameters, the measuring 
methods used and the rest of the conventional composition of the invert 
drilling fluids described here, are given in the prior art as cited above 
and, for example, described in full in the "Manual of Drilling Fluids 
Technology" of NL-Baroid Co., London, GB, particularly in the chapters 
"Mud Testing-Tools and Techniques" and "Oil Mud Technology", which is 
freely accessible to interested experts. In summary, to complete the 
invention disclosure the following can be said: 
The emulsifiers that can be used in practice are systems suitable for the 
formation of the required W/O-emulsions. In particular, selected 
oleophilic fatty acid salts, e.g. those based on amidoamine compounds, can 
be considered. Examples of these are described in the already cited U.S. 
Pat. No. 4,374,737 and the literature cited therein. A particularly 
suitable type of emulsifier is the product sold by NL-Baroid Co. under the 
brand name "EZ-mul". 
Such emulsifiers are sold commercially as highly concentrated 
active-substance preparations and can, for example, be used in amounts 
from about 2.5 to 5% by weight, particularly in amounts from about 3 to 4% 
by weight--based on the ester oil phase. 
Hydrophobized lignite particularly is used in practice as the fluid-loss 
additive and thus in particular to form a dense coating of a largely 
liquid-impermeable film on the bore-hole walls. Suitable amounts are, for 
example, from about 15 to 20 lb/bbl or from about 5 to 7% by weight, based 
on the oil phase. 
The viscosifier usually employed in drilling fluids of the type in question 
is a cation-modified finely particulate bentonite, which can be used 
particularly in amounts from about 8 to 10 lb/bbl or from about 2 to 4% by 
weight, based on the oil phase. Barite is the weighting material generally 
used in relevant applications to establish the necessary pressure 
compensation, the amounts added being varied according to the drilling 
conditions anticipated in each case. By adding barite, it is, for example, 
possible to raise the specific gravity of the drilling fluid to 2.5 and 
preferably to a value in the range from about 1.3 to 1.6. 
The dispersed aqueous phase in these invert drilling fluids is loaded with 
soluble salts, calcium chloride and/or potassium chloride are mainly used 
here. Saturation, at room temperature, of the aqueous phase with the 
soluble salt is preferred. 
The aforementioned emulsifiers, or emulsifier systems, optionally also 
serve to improve the oil wettability of the inorganic weighting materials. 
In addition to the aminoamides already mentioned, further examples are 
alkylbenzene sulfonates and imidazoline compounds. Additional information 
regarding the relevant Prior Art can be found in the following Patent 
Specifications: GB 2 158 437, EP 229 912 and DE 32 47 123. 
EXAMPLES 
EXAMPLES 1 TO 4 
In the following Examples 1 to 4, invert fluids based on selected alcohols, 
or based on alcohol mixtures, in a ratio of oil/water of 80/20 are used in 
the following basic formulation: 
200 ml alcohol 
50.9 ml water 
1.5 g organophilic bentonite (Geltone II of NL Baroid Co.) 
1.9 g diethanolamine 
7.8 g organophilic lignite (Duratone of NL Baroid Co.) 
7.8 W/O-emulsifier (EZ-mul NT of NL Baroid Co.) 
326.2 g barite 
17.5 g KCl. 
First of all, the plastic viscosity (PV), the yield point (YP) and the gel 
strength of each of the invert drilling fluids tested are measured after 
10 seconds and after 10 minutes by a viscosity measurement at 50.degree. 
C. on the unaged material. 
The invert drilling fluid is then aged for 16 hours at 125.degree. C. in 
the autoclave in the so-called "roller-oven", to test the effect of 
temperature on the stability of the emulsion. The viscosity values are 
then measured again at 50.degree. C. 
The oil phases--i.e. the alcohols or alcohol mixtures--used in these 
examples are as follows: 
Example 1: Synthetic oxoalcohol with a chain length of 10 carbon atoms 
(commercial product "Etoxo C 10") 
Example 2: 100 ml of the synthetic alcohol from Example 1 in admixture with 
100 ml of a C.sub.8-10 -alcohol mixture of natural origin (Applicant's 
commercial product "Lorol 810") 
Example 3: 100 ml of the alcohol as in Example 1 in admixture with 100 ml 
of a C.sub.12-18 -alcohol mixture of natural origin (Applicant's 
commercial product "Lorol technisch") 
Example 4: Synthetic alcohol mixture C.sub.12/13 (commercial product "Lial 
123"). 
The following values were determined for the unaged and aged material: 
______________________________________ 
Example 1 
unaged material 
aged material 
______________________________________ 
plastic viscosity (PV) 
45 55 
yield point (YP) 29 39 
gel strengths (lb/100 ft.sup.2) 
10 sec. 15 15 
10 min. 14 15 
______________________________________ 
______________________________________ 
Example 2 
unaged material 
aged material 
______________________________________ 
plastic viscosity (PV) 
36 47 
yield point (YP) 33 21 
gel strengths (lb/100 ft.sup.2) 
10 sec. 10 5 
10 min. 13 6 
______________________________________ 
______________________________________ 
Example 3 
unaged material 
aged material 
______________________________________ 
plastic viscosity (PV) 
80 62 
yield point (YP) 51 27 
gel strengths (lb/100 ft.sup.2) 
10 sec. 28 6 
10 min. 29 9 
______________________________________ 
______________________________________ 
Example 4 
unaged material 
aged material 
______________________________________ 
plastic viscosity (PV) 
85 108 
yield point (YP) 45 53 
gel strengths (lb/100 ft.sup.2) 
10 sec. 35 40 
10 min. 38 40 
______________________________________ 
EXAMPLES 5 TO 8 
Comparative tests were carried out with an oil-drilling fluid with the 
following composition. 
200 ml oil phase 
50.9 ml water 
1.9 g lime 
7.8 g organophilic lignite (Duratone of NL Baroid Co.) 
326.2 g barite 
17.9 g CaCl.sub.2 .times.2 H.sub.2 O. 
There is no W/O-emulsifier in this drilling fluid formulation. The 
following alcohols or alcohol/ester oil mixtures are used in Examples 5 to 
8 respectively. 
Example 5: C.sub.8/10 -alcohol cut of natural origin (Applicant's 
commercial product "Lorol 810") 
Example 6: A mixture of 102 ml of the alcohol in Example 5 and 98 ml of 
isobutyl oleate 
Example 7: Synthetic oxo-alcohol C.sub.13 (isotridecyl alcohol) 
Example 8: oxo-oil. 
The viscosity values determined for the unaged and aged material are as 
follows: 
______________________________________ 
Example 5 
unaged material 
aged material 
______________________________________ 
plastic viscosity (PV) 
53 40 
yield point (YP) 23 10 
gel strengths (lb/100 ft.sup.2) 
10 sec. 9 3 
10 min. 15 3 
______________________________________ 
______________________________________ 
Example 6 
unaged material 
aged material 
______________________________________ 
plastic viscosity (PV) 
36 28 
yield point (YP) 17 21 
gel strengths (lb/100 ft.sup.2) 
10 sec. 7 11 
10 min. 10 13 
______________________________________ 
______________________________________ 
Example 7 
unaged material 
aged material 
______________________________________ 
plastic viscosity (PV) 
85 108 
yield point (YP) 45 53 
gel strengths (lb/100 ft.sup.2) 
10 sec. 35 40 
10 min. 38 40 
______________________________________ 
______________________________________ 
Example 8 
unaged material 
aged material 
______________________________________ 
plastic viscosity (PV) 
45 55 
yield point (YP) 29 39 
gel strengths (lb/100 ft.sup.2) 
10 sec. 14 15 
10 min. 15 15 
______________________________________ 
EXAMPLES 9 TO 12 
These are carried out with a formulation of the following basic 
composition. 
200 ml oil phase 
50.9 ml water 
1.2 g organophilic bentonite ("Geltone II" of NL Baroid Co.) 
1.9 g lime 
7.8 g organophilic lignite ("Duratone" of NL Baroid Co.) 
7.8 g W/O-emulsifier ("EZ-mul NT" of NL Baroid Co.) 
326.2 g barite 
17.9 g CaCl.sub.2 .times.2 H.sub.2 O. 
In these Examples 9 to 12, mixtures of an ester oil based on rapeseed oil 
and the already mentioned C.sub.8/10 -alcohol mixture ("Lorol 810") are 
used as the oil phase with increasing proportions in the mixture of the 
C.sub.8/10 -alcohol cut. 
An undistilled isobutyl rapeseed-oil-ester is used as the ester oil, which 
is based on a mixture of mainly unsaturated straight-chain carboxylic 
acids, which correspond approximately to the following distribution: 60% 
oleic acid, 2% linoleic acid, 9 to 10% linolenic acid, olefin unsaturated 
C.sub.20/22 -monocarboxylic acids about 4%, the remaining percentage being 
saturated monocarboxylic acids mainly with from 16-18 carbon atoms. This 
rapeseed-oil-ester has the following characteristics: 
Density (20.degree. C.) 0.872 g/cm.sup.3 ; pour point below--15.degree. C.; 
flash point (DIN 51584) above 180.degree. C.; acid number (DGF-C-V 2) 1.2; 
viscosity at 0.degree. C. 32 mPa.s; viscosity at 5.degree. C. 24 mPa.s; no 
aromatics content. 
The mixture ratios of rapeseed-oil ester/Lorol 810 are chosen as follows 
and displaced in the direction of increasing Lorol 810 content: 
Example 9: 170 ml ester oil/30 ml alcohol cut 
Example 10: 150 ml ester oil/50 ml alcohol cut 
Example 11: 120 ml ester oil/80 ml alcohol cut 
Example 12: 100 ml ester oil/100 ml alcohol cut. 
The viscosity values determined for the unaged and aged drilling fluids are 
follows: 
______________________________________ 
Example 9 
unaged material 
aged material 
______________________________________ 
plastic viscosity (PV) 
60 43 
yield point (YP) 62 39 
gel strengths (lb/100 ft.sup.2) 
10 sec. 33 19 
10 min. 34 21 
______________________________________ 
______________________________________ 
Example 10 
unaged material 
aged material 
______________________________________ 
plastic viscosity (PV) 
45 39 
yield point (YP) 51 39 
gel strengths (lb/100 ft.sup.2) 
10 sec. 25 17 
10 min. 28 19 
______________________________________ 
______________________________________ 
Example 11 
unaged material 
aged material 
______________________________________ 
plastic viscosity (PV) 
45 33 
yield point (YP) 40 24 
gel strengths (lb/100 ft.sup.2) 
10 sec. 19 13 
10 min. 22 14 
______________________________________ 
______________________________________ 
Example 12 
unaged material 
aged material 
______________________________________ 
plastic viscosity (PV) 
36 28 
yield point (YP) 17 21 
gel strengths (lb/100 ft.sup.2) 
10 sec. 7 11 
10 min. 10 13 
______________________________________ 
COMATIVE EXAMPLE AND EXAMPLES 13 TO 16 
In the following Comparative Example and the Examples 13 to 16, drilling 
fluids of the following formulation are used: 
200 ml ester oil 
50.9 water 
1.2 g organophilic bentonite ("Geltone II" of NL Baroid Co.) 
1.9 g diethanolamine 
7.8 g organophilic lignite ("Duratone" of NL Baroid Co.) 
7.8 g W/O-emulsifier ("EZ-mul NT" of NL Baroid Co.) 
326.2 g barite 
12.5 g KCl. 
The Comparative Example uses this formulation with the undistilled isobutyl 
repeseed oil ester from Examples 9 to 12 as the ester oil. In the 
subsequent Examples 13 to 16, in each case a selected strongly oleophilic, 
water-insoluble alcohol as in the teaching of the invention is added to 
the drilling fluid formulation. The following are the details of these 
Examples: 
Example 13: Addition of 2 g of docosanol, i.e. a linear C.sub.22 -alkanol 
Example 14: Addition of 5 g of an EO/PO addition product of a C.sub.12-18 
-alcohol cut of natural origin (Applicant's commercial product "Lorol 
technisch") with the following composition: C.sub.12-18 -alcohol cut/3 
EO/6 PO (Applicant's commercial product "Dehyton LT 36") 
Example 15: Addition of 5 g of an EO/PO-polyalkyleneglycol with an average 
molecular weight of about 2000 (commercial product "Dehydran 240") 
Example 16: Addition of 2 g of 2,2-dimethyl-1,3-propane-diol 
(neopentylglycol). 
For each of the drilling oil fluids of Examples 13 to 16 and in the 
Comparative Example, the viscosity values and also the fluid-loss value 
were determined according to the HTHP method. For the determination of the 
HTHP fluid-loss value, see the hand book mentioned of NL Baroid Co., 
London "Manual of drilling fluids technology", subsection "Oil mud 
technology", chapter PROPERTIES AND TESTING PROCEDURES "HTHP-filtrate". 
The comparison of the values measured shows that by adding small amounts of 
selected alcohols in some cases a distinct improvement in the rheology is 
obtained (Example 16), and in all cases a marked reduction in the HTHP 
filtrate, i.e. a definite improvement in the fluid-loss value, is 
obtained. 
The following values apply in detail: 
______________________________________ 
Comparative Example 
unaged material 
aged material 
______________________________________ 
plastic viscosity (PV) 
61 47 
yield point (YP) 37 41 
gel strengths (lb/100 ft.sup.2) 
10 sec. 24 17 
10 min. 26 19 
HTHP: 20 ml 
______________________________________ 
______________________________________ 
Example 13 
unaged material 
aged material 
______________________________________ 
plastic viscosity (PV) 
54 39 
yield point (YP) 48 31 
gel strengths (lb/100 ft.sup.2) 
10 sec. 27 14 
10 min. 29 15 
HTHP: 6 ml 
______________________________________ 
______________________________________ 
Example 14 
unaged material 
aged material 
______________________________________ 
plastic viscosity (PV) 
45 42 
yield point (YP) 36 36 
gel strengths (lb/100 ft.sup.2) 
10 sec. 20 18 
10 min. 23 19 
HTHP: 7 ml 
______________________________________ 
______________________________________ 
Example 15 
unaged material 
aged material 
______________________________________ 
plastic viscosity (PV) 
70 36 
yield point (YP) 52 27 
gel strengths (lb/100 ft.sup.2) 
10 sec. 35 13 
10 min. 34 14 
HTHP: 9 ml 
______________________________________ 
______________________________________ 
Example 16 
unaged material 
aged material 
______________________________________ 
plastic viscosity (PV) 
44 40 
yield point (YP) 24 8 
gel strengths (lb/100 ft.sup.2) 
10 sec. 11 4 
10 min. 14 5 
HTHP: 11 ml 
______________________________________