CA2006010C - The use of selected ester oils in drilling fluids and muds - Google Patents
The use of selected ester oils in drilling fluids and muds Download PDFInfo
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- C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
- C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
- C09K8/00—Compositions for drilling of boreholes or wells; Compositions for treating boreholes or wells, e.g. for completion or for remedial operations
- C09K8/02—Well-drilling compositions
- C09K8/32—Non-aqueous well-drilling compositions, e.g. oil-based
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Abstract
Invert emulsion muds for drilling of gas and oil, which are environmentally safe, and which contain:
A. a continuous oil phase composed predominantly of at least one monocarboxylic acid ester of a C2-C12 monofunctional alkanol wherein the monocarboxylic acid contains from 16 to 24 carbon atoms and is olefinically mono- or poly-unsaturated, B. a disperse aqeuous phase, C. at least one emulsifier, D. at least one weighting agent, E. at least one fluid loss additive, and F. a mild alkaline reserve.
A. a continuous oil phase composed predominantly of at least one monocarboxylic acid ester of a C2-C12 monofunctional alkanol wherein the monocarboxylic acid contains from 16 to 24 carbon atoms and is olefinically mono- or poly-unsaturated, B. a disperse aqeuous phase, C. at least one emulsifier, D. at least one weighting agent, E. at least one fluid loss additive, and F. a mild alkaline reserve.
Description
Patent Docket No.: D 8523 BACKGROUND OF THE INVENTION
1. Field of the Invention This invention relates to new drilling fluids based on ester oils and to invert drilling muds based thereon which combine high ecological compatibility with good stability and performance properties.
1. Field of the Invention This invention relates to new drilling fluids based on ester oils and to invert drilling muds based thereon which combine high ecological compatibility with good stability and performance properties.
2. State of Related Art It is known that liquid drilling fluids for sinking bores in rock and bringing up the rock cuttings are slightly thickened, water-based or oil-based fluid systems. Oil-based systems are being increasingly used in practice, particularly in offshore drilling or in the penetration of water-sensitive layers.
Oil-based drilling fluids are generally used in the form of so-called invert emulsion muds which consist of a three phase system, namely: oil, water and finely divided additives, including in particular emulsifiers and emulsifier systems, weighting agents, fluid loss additives, alkali reserves, viscosity regulators and the like, for stabilizing the system as a whole and for establishing the desired performance properties. Full particulars can be found, for example, in the Article by P. A. Boyd et al entitled "New Base Oil Used in Low-Toxicity Oil Muds" in the Journal of Petroleum Technology, 1985, 137 to 142 and in the Article by R. B.
Bennet entitled "New Drilling Fluid Technology - Mineral oil Mud" in Journal of Petroleum Technology, 1984, 975 to 981 and the literature cited therein.
Oil-based drilling fluids were originally made from diesel oil fractions containing aromatic constituents. For the purposes of detoxification and reducing the ecological problems thus created, it was then proposed to use hydro-carbon fractions substantially free from aromatic compounds - now also known as "nonpolluting oils" - as the continuous oil phase, c~. the literature cited above. Although cer-tain advances were achieved in this way through elimination of the aromatic compounds, a further reduction in the envi-ronmental problems caused by drilling fluids of the above type seems to be urgently required. This applies in particular to the sinking of offshore wells for the de-velopment of oil and gas sources because the marine ecosys-tem is particularly sensitive to the introduction of toxic and non-readily degradable substances.
The relevant technology has for some time recognized the significance of ester-based oil phases for solving these problems. Thus, U.S. Patents 4,374,737 and 4,481,121 describe oil-based drilling fluids in which nonpolluting oils are said to be used. Non-aromatic mineral oil fractions and vegetable oils of the peanut oil, soybean oil, linseed oil, corn oil and rice oil type, and even oils of animal origin, such as whale oil, are mentioned alongside one another as nonpolluting oils of equivalent rank. The ester oils of vegetable and animal origin mentioned here are all triglycerides of natural fatty acids which are known to be environmentally safe and which, ecologically, are distinctly superior to hydrocarbon fractions, even where they have been de-aromaticized.
Interestingly, however, not one of the Examples in the US patents cited above mentions the use of such natural es-ter oils in invert emulsion drilling muds. Mineral oil fractions are used throughout as the continuous oil phase.
In its general descriptive part, U.S. 4,481,121 men-tions not only triglycerides, but also a commercial product "Arizona 208'~~ of the Arizona Chemical Company, Wayne, N.J., which is a purified isooctyl-monoalcohol ester of high-* Trade-mark A
purity tall oil fatty acids. An ester of a monofunctional alcohol and monofunctional carboxylic acids, mentioned for the first time here, is described as equivalent to trigly cerides of natural origin and/or de-aromaticized hydrocar bon fractions.
The cited US patent does not contain any reproducible Examples relating to the use of such an ester of monofunc-tional components.
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 investigations on which the present invention is based have shown that the use of readily degradable oils of vegetable and/or animal origin, which was considered in the prior art, is not feasible for practical reasons. The rheologic properties of such oil phases cannot be controlled for the wide temperature range required in practice of 0 to 5C on the one hand up to 250C and higher on the other hand.
The teaching of the present invention is based on the observation that it is in fact possible to produce oil-based invert drilling fluids based on ester oils of high environmental compatibility which correspond in their storage and in-use behavior to the best of the hitherto known oil-based drilling fluids, but have the additional advantage of increased environmental compatibility. Two key observations in this regard dominate the teaching according to the invention:
The triglycerides accumulating in the form of natural oils are not suitable for the production of mineral-oil-free oil-based invert drilling fluids, whereas the esters of monofunctional carboxylic acids with monofunctional al-cohols derived from those oils or fats are suitable for the production of such drilling fluids. The second key observation is that ester oils of the present type do not in fact show the same in-use behavior as the mineral oil fractions used hitherto based purely on hydrocarbons. In practical application, the ester oils of monofunctional components of the invention undergo partial hydrolysis, resulting in the formation of free fatty acids. These free fatty acids react in turn with the alkaline constituents always present in invert drilling fluids, for example with the alkali reserve used to prevent corrosion, to form the corresponding salts. However, salts of highly hydrophilic bases and the acids in the range of from scout C16 to C24 commonly encountered in fats and oils of natural origin are known to be compounds having comparatively high HLB values which lead in particular to the formation and stabilization of o/w emulsions. Use is made of this to a very considerable extent in the field of detergents and cleaning preparations.
However, the formation of undesirably large quantities of such o/w emulsifier systems must interfere with the w/o emulsions required for solving the problem addressed by the invention and, hence, leads to problems. The teaching of the present invention as described in the following shows how invert drilling fluids based on ester oils can be effectively used in practice despite these difficulties inherent in the system.
Thus the present invention provides an invert drilling mud free of mineral oil comprising A. a continuous oil phase composed predominately of at least one monocarboxylic acid ester of a C2-C12 monofunctional alcohol wherein the monocarboxylic acid contains from 16 to 24 carbon atoms and is olefinically mono- or poly-unsaturated, B. a disperse aqueous phase, C. at least one emulsifier, D. at least one weighting agent, E. at least one fluid loss additive, and F. a mild alkaline reserve.
In a first embodiment, therefore, the present invention relates to the use of selected esters - flowable and pumpable at temperatures in the range of from 0 to 5'C - of monofunctional C2-12 alcohols (alkanols) and olefinically mono- and/or polyunsaturated C16-24 monocarboxylic acids or mixtures thereof with small quantities of other, more especially saturated monocarboxylic acids as the oil phase, or at least a substantial part of the oil phase, of invert drilling muds which contain in a continuous oil phase a disperse aqueous phase and also emulsifiers, weighting agents, fluid loss additives and, if desired, other stand-4a and additives together with an alkali (alkaline) reserve, with the proviso that strong hydrophilic bases, such as alkali metal hydroxides and/or diethanolamine, are not used in significant quantities. Lime (calcium hydroxide) is often added as the alkali reserve, more especially for protection against inrushes of COZ and/or HZS into the drilling fluid and hence for protection against corrosion. An addition of lime such as this may be used as the alkali reserve in accordance with the invention. However, it is important to ensure that only comparatively small quantities of this alkaline component are incorporated. The maximum addition of lime is of the order of about 2 lb/bbl (line/oil mud) and is thus distinctly below the quantities typically used in practice in oil-based invert drilling fluids.
In another embodiment, the invention relates to mineral-oil-free invert drilling fluids which are suitable for the offshore development of oil and gas sources and, in a continuous oil phase based on ester oils, contain a disperse aqueous phase together with emulsifiers, weighting agents, fluid loss additives and, if desired, other standard additives. The new drilling fluids are characterized in that the oil phase consists at least substantially of esters of monofunctional C2_1z alcohols and olefinically mono- and/or polyunsaturated Cls-z4 monocarboxylic acids and in that the w/o emulsion is mildly alkalized and, where lime is added, this alkali reserve does not exceed quantities of about 2 lb/bbl (lime/oil mud). The lime content is preferably slightly below this limit.
In a further embodiment, the invention relates to an invert drilling fluid that is free of mineral oil and is substantially free from highly hydrophilic basic materials selected from the group consisting of alkali metal hydroxides and amines selected from diethanolamine and triethanolamine, said fluid consisting of (A) a continuous oil phase composed of at least one monocarboxylic acid ester of a CZ-C1z monofunctional alcohol wherein the monocarboxylic acid contains from 16 to 24 carbon atoms and comprises at least about 60% by weight of mono-olefinically unsaturated acids and no more than about 35% by weight of di- and poly-olefinically unsaturated acids, (B) a disperse aqueous phase, and (C) a mildly alkaline alkali reserve component consisting essentially of lime in a quantity not exceeding above about 2 lb/bbl of said drilling fluid.
The ester oils selected in accordance with the invention which are intended to form the entire continuous oil phase of the invert drilling muds or at least a substantial part thereof (i.e. over 50% by weight thereof) are discussed first in the following.
As already stated, an important criterion lies in the choice of esters which may be assigned to the class of reaction products of monofunctional carboxylic acids with 5a ~00~010 mono functional alcohols. In addition, however, it is in-tended in accordance with the invention exclusively or at least predominantly to use C~6-CZ4 carboxylic acids within this class. The carboxylic acids may be derived from un-branched or branched hydrocarbon chains, preferably linear chains. Monocarboxylic acids of this type and of the C~6 to CZ4 range and esters thereof are unsuitable as predominantly saturated hydrocarbon compounds due to their comparatively high solidification points. Even then, however, esters of this type are flowable and pumpable down to temperatures of 0 to 5C providing an adequate level of olefinically unsaturated ester constituents is guaranteed. In the preferred embodiment of the invention, therefore, esters of the described type of which more than 70% by weight and preferably more than 80% by weight are derived from olefinically unsaturated C~b.Z,~ carboxylic acids are used.
Important natural starting materials are carboxylic acid mixtures which contain at least 90% by weight olefinically unsaturated carboxylic acids in the above C range. The unsaturated carboxylic acids may be mono- and/or polyolefinically unsaturated. Where carboxylic acids or carboxylic acid mixtures of natural origin are used, the double ethylenic double bond in particular and, to a lesser extent, even a triple ethylenic double bond per carboxylic acid molecule plays a role in addition to a single ethylenic double bond in the molecule. Particulars of this are given in the following.
In conjunction with the choice of esters of monofunc-tional reactants in accordance with the invention, the choice of such a comparatively highly unsaturated carbox-ylic acid component in the ester oils ensures that the es-ter oils and, ultimately, the final invert emulsions show the rheologic properties required in practice, particularly at relatively low temperatures. The comparatively highly unsaturated ester oils containing 16 to 24 C atoms in the monocarboxylic acid component, which are used in accordance with the invention, have solidification points (pour point and setting point) below -10'C and more especially below -15'C in the preferred embodiment. Despite this high mo-bility at low temperatures, the molecular size of the ester oil prescribed in accordance with the invention ensures that the flashpoints of the ester oils are sufficiently high, being at least 80'C, and generally exceeding a tem-perature limit of approximately 100'C. Ester oils having flashpoints above 160'C are preferred. Ester oils of the described type showing high mobility, even at low temper-atures, and having flashpoints of 185'C or higher can be produced without difficulty.
In conjunction with these high flashpoints determined by the size of the molecule, it is possible at the same time to ensure that the viscosity values are within the required limits. Thus, preferred ester oils of the des-cribed type show a Brookfield (RVT) viscosity at a temper-ature of 0 to 5'C of not more than 50 mPa.s and preferably of at most 45 mPa.s or lower. It is possible to adjust values of 30 or even higher, for example in the range of from 20 to 25 mPa.s, at temperatures in the range indicated.
Among the unsaturated ester oils suitable for use in accordance with the invention, there are two sub-classes of particular importance.
The first of these sub-classes is based on unsaturated 4 monocarboxylic acids of which no more than about 35%
by weight are diolefinically and, optionally, polyolefinic-ally unsaturated. In their case, therefore, the content of di-and polyunsaturated carboxylic acid residues in the ester oil is comparatively limited. Within this sub-class it is preferred that at least about 60% by weight of the carboxylic acid residues are monoolefinically unsaturated.
In contrast to the first sub-class described above, the second sub-class of ester oils of particular signifi-cance is derived from C~6.2,~ unsaturated nonocarboxylic acid mixtures of which more than 45% by weight and preferably more than 55% by weight are derived from diolefinically A
2oososo and/or polyolefinically unsaturated acids within the above C range.
The most important monoethylenically unsaturated car-boxylic acids within the above carbon range are hexa-decenoic acid (palmitoleic acid (C~6) ) , oleic acid (C~8) , the related ricinoleic acid (C~e) and erucic acid (CZZ) . The most important di-unsaturated carboxylic acid within the range in question here is linoleic acid (C~8) while the most important triethylenically unsaturated carboxylic acid is linolenic acid (C~8) .
Selected individual esters formed from an unsaturated monocarboxylic acid and a monoalcohol can be used as the ester oil in accordance with the invention. One example of such esters are the esters of oleic acid, for example of the oleic acid isobutyl ester type. So far as the rheology of the system is concerned and/or for reasons of availability, it is frequently desirable to use esters from acid mixtures. This is of importance so far as meeting the above-stated specifications of the two sub-classes for preferred ester oils is concerned.
As already mentioned, the first of these two sub-classes is distinguished by the fact that its content of di-unsaturated and polyunsaturated acids is limited and does not exceed about 35% by weight. Vegetable oils of natural origin, of which the hydroly$is or transesterifi-cation gives mixtures of carboxylic acids or carboxylic acid esters of the type required here, are for example palm oil, peanut oil, castor oil and, in particular, rape-seed oil. Suitable rapeseed oils are both traditional types of high erucic acid content and also the more modern types of reduced erucic acid content and increased oleic acid content.
Ester oils of the first sub-class which correspond to this definition are particularly important for the simple reason that problems possibly arising from the lack of stability to oxidation are reduced. In practice, the drilling fluid is of course continuously pump-circulated and, in the process, is brought constantly into contact with atmospheric oxygen, often over a large area and at at least slightly elevated temperatures, for the purpose of separating out the rock cuttings brought up, for example by sieving.
However, carboxylic acid mixtures of the second sub-class mentioned above are also of considerable practical significance for use in accordance with the invention.
This is attributable in part to their broad accessibility from natural fats of animal and/or vegetable origin. Clas-sic examples of oils which have a high content of C~b_~8 or 06_22 carboxylic acids and which, at the same time, contain at least about 45% of at least diethylenically unsaturated carboxylic acids are cottonseed oil, soybean oil, sunflower oil and linseed oil. The tall oil acids isolated during the recovery of cellulose also fall within this range.
However, starting materials of the last type are generally distinguished by more or less large additional contents of resin constituents. A typical animal starting material for the production of corresponding carboxylic acid mixtures is fish oil, particularly herring oil.
As already mentioned, the ester oils used in accor-dance with the invention can be certain selected individual esters corresponding to the above definition. However, mixtures of esters of corresponding monocarboxylic acids and monoalcohols will normally be present. In this regard, the scope of the invention encompasses above all those mix-tures which, on the one hand, meet the viscosity require-ment according to the invention and of which, on the other hand, at least 50% comprise the monofunctional esters of the olefinically mono- and/or polyunsaturated C~6_2' car-boxylic acids. Ester constituents and, in particular, car-boxylic acid esters of monofunctional alcohols and mono-functional carboxylic acids of different constitution may be present as minor constituents of the mixture providing the mixture has the required property profile. This is im-portant where carboxylic acid mixtures of natural origin ~~~so~.o are used. Natural starting materials such as these gener-ally also contain more or less large proportions of satu-rated carboxylic acids, often including linear C
car-~6_~a boxylic acids. Saturated fatty acids of this type and their esters readily give rise to rheologic difficulties due to their comparatively high melting points. According to the invention, therefore, saturated C~6_~8 carboxylic acids preferably make up no more than 20% by weight and in , particular, no more than 10% by weight of the ester oils.
By contrast, the presence of saturated carboxylic acids containing less than 16 carbon atoms and more , especially, from 12 to 14 carbon atoms is more acceptable.
In small quantities, the contents of such lower, fully saturated fatty acids often present in natural starting materials are frequently valuable mixture components in the context of the problem addressed by the invention. Their esters are not vulnerable to oxidation under practical in-use conditions and their rheologic properties promote the objective of the invention, namely to replace the pure hydrocarbon oils hitherto solely used in practice b est y er oils or ester oil fractions.
The alcohol radicals of the esters or ester mixtures according to the invention are preferably derived from straight-chain and/or branched-chain saturated alcohols, particular significance being attributed to alcohols c -on taining at least 3 C atoms and, more especially, to alco-hols containing up to about 10 C atoms. The alcohols can also be of natural origin, in which case they have normally been obtained from the corresponding carboxylic acids or their esters by hydrogenating reduction. However the in-, vention is by no means limited to starting materials of natural origin. Both on the monoalcohol side and on the monocarboxylic acid side, the starting materials of natural origin may be partly or completely replaced by correspond-ing components of synthetic origin. Typical examples of alcohols are the corresponding oxo alcohols (branched alcohols) and the linear alcohols obtained by the Ziegler process. Similarly, monocarboxylic acid components present in particular in carboxylic acid mixtures can be derived from petrochemical synthesis. However, the advantages of starting materials of natural origin lie in particular in their proven lower toxicologic values, their ready degradability and their ready accessibility. The natural destruction of the used oil mud ultimately required presupposes that ester oils of the type described herein be both aerobically and anaerobicaliy degradable.
l0 However, one important limitation is associated with the use of these ester oils in invert oil muds of the type used in the present invention. This limitation arises out of the difficulty mentioned at the beginning that, in principle, the carboxylic acid esters are vulnerable to hydrolysis and, accordingly, have to behave differently than the pure hydrocarbon oils hitherto used.
Invert drilling muds of the type used herein contain the finely disperse aqueous phase, normally together with the continuous oil phase, in quantities of from 5 to 45% by weight and preferably in quantities of from 5 to 25% by weight. Particularly preferred is the range of 10 to 25%
by weight of disperse aqueous phase. This precondition from the constitution of conventional drilling muds also applies to the ester-based invert drilling muds of the invention. It is clear that, in continuous practical operation, disturbances of the equilibrium can occur in the multiphase system as a result of partial ester hydrolysis.
The situation is complicated by the fact that, in practice, drilling muds of the present type always contain an alkali reserve. This alkali reserve is particularly important in affording protection against corrosion caused by unexpected inrushes of acidic gases, particularly C02 and/or H2S. The danger of corrosion to the drill pipe requires the safe establishment of pH values at least in the mildly alkaline range, for example in the range from pH
8.5 to 9 and higher.
In oil muds based on pure hydrocarbon fractions as the 1l oil phase, strongly alkaline and, at the same time, highly hydrophilic inorganic or organic additives are generally used in practice without any difficulty. Particular signi-ficance can be attributed to the alkali hydroxides and in , particular, to sodium hydroxide on the one hand or t o highly hydrophilic organic bases, diethanolamine and/or triethanolamine being particularly typical additives for binding impurities of H2S . In addition to and/or instead of the highly hydrophilic inorganic and organic bases me -n tinned here, lime or even more weakly basic metal oxides, especially zinc oxide or comparable zinc compounds, are particularly important as the alkali reserve Lime in -.
par ticular is widely used an inexpensive alkalizing agent. It may safely be used in comparatively high quantities of, for example, from 5 to 10 lb/bbl (lime/oil mud) or even higher.
The use of the ester-based oil muds of the invention requires a departure from standard practice so far as these variables are concerned. It is of course necessary in this case, too, to ensure that the pH value of the drilling mud is kept at least in the mildly alkaline range and that a sufficient quantity of alkali reserve is available for unexpected inrushes of, in particular, acidic gases. At the same time, however, the ester hydrolysis should not be undesirably promoted and/or accelerated by such an alkali content.
Thus, in the preferred embodiment of the invention, no significant quantities of highly hydrophilic, inorganic and/or organic bases are used in the oil mud. In particu-lar, the invention does not use alkali hydroxides or highly hydrophilic amines of the diethanolamine and/or triethanol-amine type. Lime may be effectively used as the alkali re-serve. In that case, however, it is best to limit the max-imum quantity of lime used in the drilling mud to around 2 lb/bbl or slightly lower, for example to between 1 and 1.8 lb/bbl (lime/drilling mudj. In addition to or instead of lime, it is also possible to use other known alkali reserves, including in particular the less basic metal oxides of the zinc oxide type and other comparable zinc compounds. However, even where acid-binding agents such as these are used, it is important not to use excessive amounts to prevent unwanted premature ageing of the drilling mud accompanied by an increase in viscosity and hence a deterioration in the rheologic properties. The particular aspect of the teaching according to the inv -en tion prevents or at least limits the formation of unwanted quantities of highly active o/w emulsifiers to such an extent that the favorable rheologic properties are maintained for long periods in operation, even in the event of thermal ageing. In relation to the recommendations of the prior art which have hitherto remained in the realm of theoretical considerations, this represents a significant surplus which actually enables the low toxic properties of ester oils of the present type to be utilized in practice for the first time.
The esters based on olefinically unsaturated C~6_z4 monocarboxylic acids defined in accordance with the inven-tion, which flow and can be pumped at temperatures in the range from 0 to 5'C, generally make up at least about half the continuous oil phase of the drilling mud. However, preferred oil phases are those in which esters or ester mixtures of the type according to the invention are very much predominantly present. In one particularly important embodiment of the invention, the oil phase consists almost entirely of such ester oils. Components suitable for mix-ing with the ester oils defined in accordance with the in-vention are, in particular, selected other ester oil frac-3 0 tiOns which are described in copending Canadian application Serial No. 2,006,009 "Drilling Fluids and Muds Containing Selected Ester oils", filed of even date herewith. The invention also encompasses mixtures with such other selected ester oils. These ester oils, which are described in the above copending application, are esters of monofunctional Cz.~z alcohols and saturated aliphatic C~z_~6 monocarboxylic acids.
A
The following rheologic data apply to the rheology of preferred invert drilling muds according to the invention:
plastic viscosity (PV) in the range of from 10 to 60 mPa.s and preferably in the range of from 15 to 40 mPa.s, yield point (YP) in the range of from 5 to 40 1b/100 ft2 and preferably in the range of from 10 to 25 1b/100 ftz as , measured at 50'C. Full information on the determination of these parameters, on the measurement techniques used and on the otherwise standard composition of the invert oil muds described herein can be found in the prior art cited above and, for example, in "Manual of Drilling Fluids Technology"
published by BAROID DRILLING FLUIDS, INC., cf. in particular the Chapter entitled "Mud Testing - Tools and Techniques" and "Oil Mud Technology", which is freely available to interested experts. In the interests of fullness of disclosure, the following summary observations may be made:
Emulsifiers suitable for use in practice are systems which are capable of forming the required w/o emulsions.
Selected oleophilic fatty acid salts, for example those based on amidoamine compounds, are particularly suitable, examples being described in the already cited U.S. Patent No. 4,374,737 and the literature cited therein. One particularly suitable type of emulsifier is the product marketed under the name of "EZ-MULi'" by BAROID DRILLING
FLUIDS, INC.
Emulsifiers of the above type are marketed in the form of concentrates and can be used, for example, in quantities of from 2.5 to 5% by weight and more especially in quantities of from 3 to 4% by weight, based in each case on the ester oil phase.
In practice, organophilic lignite is used as a fluid-loss additive and forms an impervious coating in the form of a substantially water-impermeable film over the walls of the well. Suitable quantities are, for example, in the range of from 15 to 20 lb/bbl or in the range of from 5 to 7% by weight, based on the ester oil phase.
20~16~.(~
In drilling muds of the present type, the thickener normally used to create viscosity is a cationically modified, finely divided organophilic bentonite which can be used in quantities of from 8 to 10 lb/bbl or in the range of from 2 to 4% by weight, based on the ester oil phase. The weighting agent normally used in practice to establish the necessary pressure equalization is barite which is added in quantities adapted to the particular conditions to be expected in the well. For example, it is l0 possible by addition of barite to increase the specific gravity of the drilling mud to values of up to about 2.5 and preferably in the range from 1.3 to 1.6.
In invert drilling muds of the present type, the disperse aqueous phase is charged with soluble salts, generally calcium chloride and/or potassium chloride, the aqueous phase preferably being saturated with the soluble salt at room temperature.
The emulsifiers or emulsifier systems mentioned above can also be used to improve the oil wettability of the in-organic weighting materials. In addition to the amino-amides already discussed, alkyl benzenesulfonates and imi-dazoline compounds are further examples. Additional information on the relevant prior art can be found in the following literature references: GB 2,158,437, EP 229 912 and DE 32 47 123.
One important application for the new drilling fluids is in offshore drilling for the development of oil and/or gas sources, to provide technically useful drilling fluids of high ecological compatibility. The use of the new drilling fluids is of particular importance in, but is not limited to, the offshore sector. The new drilling fluids can also be used quite generally for land-supported drilling, including for example geothermal drilling, water drilling, geoscientific drilling and mine drilling. In this case, too, the ester-based drilling fluids selected in accordance with the invention basically simplify ecotoxic problems to a considerable extent. In addition, the zoosolo drilling fluids based in accordance with the invention on the co-use of ester oils of the described type are also distinguished by distinctly improved lubricity. This is particularly important when the path of the drill pipe and hence the well deviate from the vertical during drilling, for example at considerable depths. In such cases, the rotating drill pipe readily comes into contact with the well wall and embeds itself therein. Ester oils of the type used as oil phase in accordance with the invention have a distinctly better lubricating effect than the mineral oils hitherto used, which is an important advantage of the present invention.
The invention will be illustrated but not limited by the following examples.
EXAMPLES
An invert drilling mud was prepared using an undistil led isobutyl rapeseed oil ester as the continuous oil phase. This rapeseed oil ester was based on a mixture of predominantly unsaturated, straight-chain carboxylic acids which correspond substantially to the following distribution: 60% oleic acid, 20% linoleic acid, 9 to 10%
linolenic acid, olefinically unsaturated Czo-z2 monocarboxylic acids approximately 4%, remainder saturated monocarboxylic acids predominantly in the C~b_~8 range.
The rapeseed oil ester used had the following charac-teristic data: density (20'C) 0.872 g/cm3; pour point below -15°C; flash point (DIN 51584) above 180'C; acid value (DGF-C-V 2) 1.2; viscosity at 0°C 32 mPa.s, viscosity at 5°C 24 mPa.s; no aromatic compounds.
An invert drilling mud was conventionally prepared us-ing the following mixture constituents:
230 ml rapeseed oil fatty acid ester 26 ml water 6 g organophilic bentonite (GELTONEt", a product of BAROID DRILLING FLUIDS, INC. of Aberdeen, Scotland) 0.2 g lime 6 g water in oil emulsifier ("EZ-MULt'~~, a product of BAROID DRILLING FLUIDS, INC.) 340 g barite 9.2 g CaClz x 2H20 20 g organophilic lignite ("DURATONEL"'", a product of BAROID DRILLING FLUIDS, INC.) Plastic viscosity (PV), yield point (YP) and gel strength after 10 seconds and 10 minutes were first deter-mined on the material before ageing by viscosity measure-ment at 50°C.
The invert drilling mud was then aged for 16 h at 125°C in an autoclave in a so-called "roller oven" to determine the effect of temperature on the stability of the emulsion. The viscosity values were then redetermined at 50°C.
The following results were obtained:
Unaged Aged material material Plastic viscosity (PV) 35 62 Yield point (YP) 21 24 Gel strength (1b/100 ft2) 10 seconds 12 12 10 minutes 14 15 Another invert drilling mud was prepared in the same way as in Example 1, except that on this occasion the quan-tity of lime was increased to 4 g, i.e. drastically beyond the limit of approximately 2 lb/bbl.
Once again, the viscosity values and gel strength of the material were determined before and after ageing. The following results were obtained:
Unaged Aged material material Plastic viscosity (PV) 41 cannot be meas-ured Yield point (YP) 22 cannot be meas-ured Gel strength (1b/100 ft2) 10 seconds 11 74 10 minutes 17 72 Another invert drilling mud was prepared with a continuous oil phase. The oil phase consisted of distilled oleic acid isobutyl ester which has the following characteristic data: density (20°C) 0.86 g/cm3; viscosity (20°C) 8 to 10 mPa.s; pour point below -25°C; flash point (DIN 51584) above 185°C; acid value (DGF-C-V 2) below 1; no aromatic compounds.
A drilling mud of the following composition was prepared:
210 ml isobutyl oleate 6 g fatty-acid-based emulsifier (INVERMULtma product of BAROID DRILLING FLUIDS, INC.) 6 g organophilic bentonite (GELTONE Iltm a product of BAROID DRILLING FLUIDS, INC.) 13 g organophilic lignite (DURATONEt', a product of BAROID DRILLING FLUIDS, INC.) 1 g lime 3 g water in oil emulsifier (EZ-MULt', a product of BAROID DRILLING FLUIDS, INC.) 270 g barite 58.2 g saturated aqueous CaCl2 solution Plastic viscosity, yield point and gel strength after seconds and 10 minutes were determined before and after ageing (16h at 125°C in a roller oven) in the same way as in Example 1. The results obtained are shown below. In the 5 formulation used here, 1.9 g added lime substantially corresponds to the limit of 2 lb/bbl of alkali reserve.
Unaged Aged material material Plastic viscosity (PV) 46 41 Yield point (YP) 35 32 Gel strength (1b/100 ftz) 10 seconds 17 18 10 minutes 21 29 Another invert drilling oil emulsion was prepared using the formulation of Example 2, except that the addition of lime was increased to 2 g and hence to within the limit of about 2 lb/bbl of alkali reserve. The plastic viscosity, yield point and gel strength of the material before and after ageing are shown in the following:
Unaged Aged material material Plastic viscosity (PV) 53 46 Yield point (YP) 61 45 Gel strength (1b/100 ft2) 10 seconds 33 24 10 minutes 40 29
Oil-based drilling fluids are generally used in the form of so-called invert emulsion muds which consist of a three phase system, namely: oil, water and finely divided additives, including in particular emulsifiers and emulsifier systems, weighting agents, fluid loss additives, alkali reserves, viscosity regulators and the like, for stabilizing the system as a whole and for establishing the desired performance properties. Full particulars can be found, for example, in the Article by P. A. Boyd et al entitled "New Base Oil Used in Low-Toxicity Oil Muds" in the Journal of Petroleum Technology, 1985, 137 to 142 and in the Article by R. B.
Bennet entitled "New Drilling Fluid Technology - Mineral oil Mud" in Journal of Petroleum Technology, 1984, 975 to 981 and the literature cited therein.
Oil-based drilling fluids were originally made from diesel oil fractions containing aromatic constituents. For the purposes of detoxification and reducing the ecological problems thus created, it was then proposed to use hydro-carbon fractions substantially free from aromatic compounds - now also known as "nonpolluting oils" - as the continuous oil phase, c~. the literature cited above. Although cer-tain advances were achieved in this way through elimination of the aromatic compounds, a further reduction in the envi-ronmental problems caused by drilling fluids of the above type seems to be urgently required. This applies in particular to the sinking of offshore wells for the de-velopment of oil and gas sources because the marine ecosys-tem is particularly sensitive to the introduction of toxic and non-readily degradable substances.
The relevant technology has for some time recognized the significance of ester-based oil phases for solving these problems. Thus, U.S. Patents 4,374,737 and 4,481,121 describe oil-based drilling fluids in which nonpolluting oils are said to be used. Non-aromatic mineral oil fractions and vegetable oils of the peanut oil, soybean oil, linseed oil, corn oil and rice oil type, and even oils of animal origin, such as whale oil, are mentioned alongside one another as nonpolluting oils of equivalent rank. The ester oils of vegetable and animal origin mentioned here are all triglycerides of natural fatty acids which are known to be environmentally safe and which, ecologically, are distinctly superior to hydrocarbon fractions, even where they have been de-aromaticized.
Interestingly, however, not one of the Examples in the US patents cited above mentions the use of such natural es-ter oils in invert emulsion drilling muds. Mineral oil fractions are used throughout as the continuous oil phase.
In its general descriptive part, U.S. 4,481,121 men-tions not only triglycerides, but also a commercial product "Arizona 208'~~ of the Arizona Chemical Company, Wayne, N.J., which is a purified isooctyl-monoalcohol ester of high-* Trade-mark A
purity tall oil fatty acids. An ester of a monofunctional alcohol and monofunctional carboxylic acids, mentioned for the first time here, is described as equivalent to trigly cerides of natural origin and/or de-aromaticized hydrocar bon fractions.
The cited US patent does not contain any reproducible Examples relating to the use of such an ester of monofunc-tional components.
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 investigations on which the present invention is based have shown that the use of readily degradable oils of vegetable and/or animal origin, which was considered in the prior art, is not feasible for practical reasons. The rheologic properties of such oil phases cannot be controlled for the wide temperature range required in practice of 0 to 5C on the one hand up to 250C and higher on the other hand.
The teaching of the present invention is based on the observation that it is in fact possible to produce oil-based invert drilling fluids based on ester oils of high environmental compatibility which correspond in their storage and in-use behavior to the best of the hitherto known oil-based drilling fluids, but have the additional advantage of increased environmental compatibility. Two key observations in this regard dominate the teaching according to the invention:
The triglycerides accumulating in the form of natural oils are not suitable for the production of mineral-oil-free oil-based invert drilling fluids, whereas the esters of monofunctional carboxylic acids with monofunctional al-cohols derived from those oils or fats are suitable for the production of such drilling fluids. The second key observation is that ester oils of the present type do not in fact show the same in-use behavior as the mineral oil fractions used hitherto based purely on hydrocarbons. In practical application, the ester oils of monofunctional components of the invention undergo partial hydrolysis, resulting in the formation of free fatty acids. These free fatty acids react in turn with the alkaline constituents always present in invert drilling fluids, for example with the alkali reserve used to prevent corrosion, to form the corresponding salts. However, salts of highly hydrophilic bases and the acids in the range of from scout C16 to C24 commonly encountered in fats and oils of natural origin are known to be compounds having comparatively high HLB values which lead in particular to the formation and stabilization of o/w emulsions. Use is made of this to a very considerable extent in the field of detergents and cleaning preparations.
However, the formation of undesirably large quantities of such o/w emulsifier systems must interfere with the w/o emulsions required for solving the problem addressed by the invention and, hence, leads to problems. The teaching of the present invention as described in the following shows how invert drilling fluids based on ester oils can be effectively used in practice despite these difficulties inherent in the system.
Thus the present invention provides an invert drilling mud free of mineral oil comprising A. a continuous oil phase composed predominately of at least one monocarboxylic acid ester of a C2-C12 monofunctional alcohol wherein the monocarboxylic acid contains from 16 to 24 carbon atoms and is olefinically mono- or poly-unsaturated, B. a disperse aqueous phase, C. at least one emulsifier, D. at least one weighting agent, E. at least one fluid loss additive, and F. a mild alkaline reserve.
In a first embodiment, therefore, the present invention relates to the use of selected esters - flowable and pumpable at temperatures in the range of from 0 to 5'C - of monofunctional C2-12 alcohols (alkanols) and olefinically mono- and/or polyunsaturated C16-24 monocarboxylic acids or mixtures thereof with small quantities of other, more especially saturated monocarboxylic acids as the oil phase, or at least a substantial part of the oil phase, of invert drilling muds which contain in a continuous oil phase a disperse aqueous phase and also emulsifiers, weighting agents, fluid loss additives and, if desired, other stand-4a and additives together with an alkali (alkaline) reserve, with the proviso that strong hydrophilic bases, such as alkali metal hydroxides and/or diethanolamine, are not used in significant quantities. Lime (calcium hydroxide) is often added as the alkali reserve, more especially for protection against inrushes of COZ and/or HZS into the drilling fluid and hence for protection against corrosion. An addition of lime such as this may be used as the alkali reserve in accordance with the invention. However, it is important to ensure that only comparatively small quantities of this alkaline component are incorporated. The maximum addition of lime is of the order of about 2 lb/bbl (line/oil mud) and is thus distinctly below the quantities typically used in practice in oil-based invert drilling fluids.
In another embodiment, the invention relates to mineral-oil-free invert drilling fluids which are suitable for the offshore development of oil and gas sources and, in a continuous oil phase based on ester oils, contain a disperse aqueous phase together with emulsifiers, weighting agents, fluid loss additives and, if desired, other standard additives. The new drilling fluids are characterized in that the oil phase consists at least substantially of esters of monofunctional C2_1z alcohols and olefinically mono- and/or polyunsaturated Cls-z4 monocarboxylic acids and in that the w/o emulsion is mildly alkalized and, where lime is added, this alkali reserve does not exceed quantities of about 2 lb/bbl (lime/oil mud). The lime content is preferably slightly below this limit.
In a further embodiment, the invention relates to an invert drilling fluid that is free of mineral oil and is substantially free from highly hydrophilic basic materials selected from the group consisting of alkali metal hydroxides and amines selected from diethanolamine and triethanolamine, said fluid consisting of (A) a continuous oil phase composed of at least one monocarboxylic acid ester of a CZ-C1z monofunctional alcohol wherein the monocarboxylic acid contains from 16 to 24 carbon atoms and comprises at least about 60% by weight of mono-olefinically unsaturated acids and no more than about 35% by weight of di- and poly-olefinically unsaturated acids, (B) a disperse aqueous phase, and (C) a mildly alkaline alkali reserve component consisting essentially of lime in a quantity not exceeding above about 2 lb/bbl of said drilling fluid.
The ester oils selected in accordance with the invention which are intended to form the entire continuous oil phase of the invert drilling muds or at least a substantial part thereof (i.e. over 50% by weight thereof) are discussed first in the following.
As already stated, an important criterion lies in the choice of esters which may be assigned to the class of reaction products of monofunctional carboxylic acids with 5a ~00~010 mono functional alcohols. In addition, however, it is in-tended in accordance with the invention exclusively or at least predominantly to use C~6-CZ4 carboxylic acids within this class. The carboxylic acids may be derived from un-branched or branched hydrocarbon chains, preferably linear chains. Monocarboxylic acids of this type and of the C~6 to CZ4 range and esters thereof are unsuitable as predominantly saturated hydrocarbon compounds due to their comparatively high solidification points. Even then, however, esters of this type are flowable and pumpable down to temperatures of 0 to 5C providing an adequate level of olefinically unsaturated ester constituents is guaranteed. In the preferred embodiment of the invention, therefore, esters of the described type of which more than 70% by weight and preferably more than 80% by weight are derived from olefinically unsaturated C~b.Z,~ carboxylic acids are used.
Important natural starting materials are carboxylic acid mixtures which contain at least 90% by weight olefinically unsaturated carboxylic acids in the above C range. The unsaturated carboxylic acids may be mono- and/or polyolefinically unsaturated. Where carboxylic acids or carboxylic acid mixtures of natural origin are used, the double ethylenic double bond in particular and, to a lesser extent, even a triple ethylenic double bond per carboxylic acid molecule plays a role in addition to a single ethylenic double bond in the molecule. Particulars of this are given in the following.
In conjunction with the choice of esters of monofunc-tional reactants in accordance with the invention, the choice of such a comparatively highly unsaturated carbox-ylic acid component in the ester oils ensures that the es-ter oils and, ultimately, the final invert emulsions show the rheologic properties required in practice, particularly at relatively low temperatures. The comparatively highly unsaturated ester oils containing 16 to 24 C atoms in the monocarboxylic acid component, which are used in accordance with the invention, have solidification points (pour point and setting point) below -10'C and more especially below -15'C in the preferred embodiment. Despite this high mo-bility at low temperatures, the molecular size of the ester oil prescribed in accordance with the invention ensures that the flashpoints of the ester oils are sufficiently high, being at least 80'C, and generally exceeding a tem-perature limit of approximately 100'C. Ester oils having flashpoints above 160'C are preferred. Ester oils of the described type showing high mobility, even at low temper-atures, and having flashpoints of 185'C or higher can be produced without difficulty.
In conjunction with these high flashpoints determined by the size of the molecule, it is possible at the same time to ensure that the viscosity values are within the required limits. Thus, preferred ester oils of the des-cribed type show a Brookfield (RVT) viscosity at a temper-ature of 0 to 5'C of not more than 50 mPa.s and preferably of at most 45 mPa.s or lower. It is possible to adjust values of 30 or even higher, for example in the range of from 20 to 25 mPa.s, at temperatures in the range indicated.
Among the unsaturated ester oils suitable for use in accordance with the invention, there are two sub-classes of particular importance.
The first of these sub-classes is based on unsaturated 4 monocarboxylic acids of which no more than about 35%
by weight are diolefinically and, optionally, polyolefinic-ally unsaturated. In their case, therefore, the content of di-and polyunsaturated carboxylic acid residues in the ester oil is comparatively limited. Within this sub-class it is preferred that at least about 60% by weight of the carboxylic acid residues are monoolefinically unsaturated.
In contrast to the first sub-class described above, the second sub-class of ester oils of particular signifi-cance is derived from C~6.2,~ unsaturated nonocarboxylic acid mixtures of which more than 45% by weight and preferably more than 55% by weight are derived from diolefinically A
2oososo and/or polyolefinically unsaturated acids within the above C range.
The most important monoethylenically unsaturated car-boxylic acids within the above carbon range are hexa-decenoic acid (palmitoleic acid (C~6) ) , oleic acid (C~8) , the related ricinoleic acid (C~e) and erucic acid (CZZ) . The most important di-unsaturated carboxylic acid within the range in question here is linoleic acid (C~8) while the most important triethylenically unsaturated carboxylic acid is linolenic acid (C~8) .
Selected individual esters formed from an unsaturated monocarboxylic acid and a monoalcohol can be used as the ester oil in accordance with the invention. One example of such esters are the esters of oleic acid, for example of the oleic acid isobutyl ester type. So far as the rheology of the system is concerned and/or for reasons of availability, it is frequently desirable to use esters from acid mixtures. This is of importance so far as meeting the above-stated specifications of the two sub-classes for preferred ester oils is concerned.
As already mentioned, the first of these two sub-classes is distinguished by the fact that its content of di-unsaturated and polyunsaturated acids is limited and does not exceed about 35% by weight. Vegetable oils of natural origin, of which the hydroly$is or transesterifi-cation gives mixtures of carboxylic acids or carboxylic acid esters of the type required here, are for example palm oil, peanut oil, castor oil and, in particular, rape-seed oil. Suitable rapeseed oils are both traditional types of high erucic acid content and also the more modern types of reduced erucic acid content and increased oleic acid content.
Ester oils of the first sub-class which correspond to this definition are particularly important for the simple reason that problems possibly arising from the lack of stability to oxidation are reduced. In practice, the drilling fluid is of course continuously pump-circulated and, in the process, is brought constantly into contact with atmospheric oxygen, often over a large area and at at least slightly elevated temperatures, for the purpose of separating out the rock cuttings brought up, for example by sieving.
However, carboxylic acid mixtures of the second sub-class mentioned above are also of considerable practical significance for use in accordance with the invention.
This is attributable in part to their broad accessibility from natural fats of animal and/or vegetable origin. Clas-sic examples of oils which have a high content of C~b_~8 or 06_22 carboxylic acids and which, at the same time, contain at least about 45% of at least diethylenically unsaturated carboxylic acids are cottonseed oil, soybean oil, sunflower oil and linseed oil. The tall oil acids isolated during the recovery of cellulose also fall within this range.
However, starting materials of the last type are generally distinguished by more or less large additional contents of resin constituents. A typical animal starting material for the production of corresponding carboxylic acid mixtures is fish oil, particularly herring oil.
As already mentioned, the ester oils used in accor-dance with the invention can be certain selected individual esters corresponding to the above definition. However, mixtures of esters of corresponding monocarboxylic acids and monoalcohols will normally be present. In this regard, the scope of the invention encompasses above all those mix-tures which, on the one hand, meet the viscosity require-ment according to the invention and of which, on the other hand, at least 50% comprise the monofunctional esters of the olefinically mono- and/or polyunsaturated C~6_2' car-boxylic acids. Ester constituents and, in particular, car-boxylic acid esters of monofunctional alcohols and mono-functional carboxylic acids of different constitution may be present as minor constituents of the mixture providing the mixture has the required property profile. This is im-portant where carboxylic acid mixtures of natural origin ~~~so~.o are used. Natural starting materials such as these gener-ally also contain more or less large proportions of satu-rated carboxylic acids, often including linear C
car-~6_~a boxylic acids. Saturated fatty acids of this type and their esters readily give rise to rheologic difficulties due to their comparatively high melting points. According to the invention, therefore, saturated C~6_~8 carboxylic acids preferably make up no more than 20% by weight and in , particular, no more than 10% by weight of the ester oils.
By contrast, the presence of saturated carboxylic acids containing less than 16 carbon atoms and more , especially, from 12 to 14 carbon atoms is more acceptable.
In small quantities, the contents of such lower, fully saturated fatty acids often present in natural starting materials are frequently valuable mixture components in the context of the problem addressed by the invention. Their esters are not vulnerable to oxidation under practical in-use conditions and their rheologic properties promote the objective of the invention, namely to replace the pure hydrocarbon oils hitherto solely used in practice b est y er oils or ester oil fractions.
The alcohol radicals of the esters or ester mixtures according to the invention are preferably derived from straight-chain and/or branched-chain saturated alcohols, particular significance being attributed to alcohols c -on taining at least 3 C atoms and, more especially, to alco-hols containing up to about 10 C atoms. The alcohols can also be of natural origin, in which case they have normally been obtained from the corresponding carboxylic acids or their esters by hydrogenating reduction. However the in-, vention is by no means limited to starting materials of natural origin. Both on the monoalcohol side and on the monocarboxylic acid side, the starting materials of natural origin may be partly or completely replaced by correspond-ing components of synthetic origin. Typical examples of alcohols are the corresponding oxo alcohols (branched alcohols) and the linear alcohols obtained by the Ziegler process. Similarly, monocarboxylic acid components present in particular in carboxylic acid mixtures can be derived from petrochemical synthesis. However, the advantages of starting materials of natural origin lie in particular in their proven lower toxicologic values, their ready degradability and their ready accessibility. The natural destruction of the used oil mud ultimately required presupposes that ester oils of the type described herein be both aerobically and anaerobicaliy degradable.
l0 However, one important limitation is associated with the use of these ester oils in invert oil muds of the type used in the present invention. This limitation arises out of the difficulty mentioned at the beginning that, in principle, the carboxylic acid esters are vulnerable to hydrolysis and, accordingly, have to behave differently than the pure hydrocarbon oils hitherto used.
Invert drilling muds of the type used herein contain the finely disperse aqueous phase, normally together with the continuous oil phase, in quantities of from 5 to 45% by weight and preferably in quantities of from 5 to 25% by weight. Particularly preferred is the range of 10 to 25%
by weight of disperse aqueous phase. This precondition from the constitution of conventional drilling muds also applies to the ester-based invert drilling muds of the invention. It is clear that, in continuous practical operation, disturbances of the equilibrium can occur in the multiphase system as a result of partial ester hydrolysis.
The situation is complicated by the fact that, in practice, drilling muds of the present type always contain an alkali reserve. This alkali reserve is particularly important in affording protection against corrosion caused by unexpected inrushes of acidic gases, particularly C02 and/or H2S. The danger of corrosion to the drill pipe requires the safe establishment of pH values at least in the mildly alkaline range, for example in the range from pH
8.5 to 9 and higher.
In oil muds based on pure hydrocarbon fractions as the 1l oil phase, strongly alkaline and, at the same time, highly hydrophilic inorganic or organic additives are generally used in practice without any difficulty. Particular signi-ficance can be attributed to the alkali hydroxides and in , particular, to sodium hydroxide on the one hand or t o highly hydrophilic organic bases, diethanolamine and/or triethanolamine being particularly typical additives for binding impurities of H2S . In addition to and/or instead of the highly hydrophilic inorganic and organic bases me -n tinned here, lime or even more weakly basic metal oxides, especially zinc oxide or comparable zinc compounds, are particularly important as the alkali reserve Lime in -.
par ticular is widely used an inexpensive alkalizing agent. It may safely be used in comparatively high quantities of, for example, from 5 to 10 lb/bbl (lime/oil mud) or even higher.
The use of the ester-based oil muds of the invention requires a departure from standard practice so far as these variables are concerned. It is of course necessary in this case, too, to ensure that the pH value of the drilling mud is kept at least in the mildly alkaline range and that a sufficient quantity of alkali reserve is available for unexpected inrushes of, in particular, acidic gases. At the same time, however, the ester hydrolysis should not be undesirably promoted and/or accelerated by such an alkali content.
Thus, in the preferred embodiment of the invention, no significant quantities of highly hydrophilic, inorganic and/or organic bases are used in the oil mud. In particu-lar, the invention does not use alkali hydroxides or highly hydrophilic amines of the diethanolamine and/or triethanol-amine type. Lime may be effectively used as the alkali re-serve. In that case, however, it is best to limit the max-imum quantity of lime used in the drilling mud to around 2 lb/bbl or slightly lower, for example to between 1 and 1.8 lb/bbl (lime/drilling mudj. In addition to or instead of lime, it is also possible to use other known alkali reserves, including in particular the less basic metal oxides of the zinc oxide type and other comparable zinc compounds. However, even where acid-binding agents such as these are used, it is important not to use excessive amounts to prevent unwanted premature ageing of the drilling mud accompanied by an increase in viscosity and hence a deterioration in the rheologic properties. The particular aspect of the teaching according to the inv -en tion prevents or at least limits the formation of unwanted quantities of highly active o/w emulsifiers to such an extent that the favorable rheologic properties are maintained for long periods in operation, even in the event of thermal ageing. In relation to the recommendations of the prior art which have hitherto remained in the realm of theoretical considerations, this represents a significant surplus which actually enables the low toxic properties of ester oils of the present type to be utilized in practice for the first time.
The esters based on olefinically unsaturated C~6_z4 monocarboxylic acids defined in accordance with the inven-tion, which flow and can be pumped at temperatures in the range from 0 to 5'C, generally make up at least about half the continuous oil phase of the drilling mud. However, preferred oil phases are those in which esters or ester mixtures of the type according to the invention are very much predominantly present. In one particularly important embodiment of the invention, the oil phase consists almost entirely of such ester oils. Components suitable for mix-ing with the ester oils defined in accordance with the in-vention are, in particular, selected other ester oil frac-3 0 tiOns which are described in copending Canadian application Serial No. 2,006,009 "Drilling Fluids and Muds Containing Selected Ester oils", filed of even date herewith. The invention also encompasses mixtures with such other selected ester oils. These ester oils, which are described in the above copending application, are esters of monofunctional Cz.~z alcohols and saturated aliphatic C~z_~6 monocarboxylic acids.
A
The following rheologic data apply to the rheology of preferred invert drilling muds according to the invention:
plastic viscosity (PV) in the range of from 10 to 60 mPa.s and preferably in the range of from 15 to 40 mPa.s, yield point (YP) in the range of from 5 to 40 1b/100 ft2 and preferably in the range of from 10 to 25 1b/100 ftz as , measured at 50'C. Full information on the determination of these parameters, on the measurement techniques used and on the otherwise standard composition of the invert oil muds described herein can be found in the prior art cited above and, for example, in "Manual of Drilling Fluids Technology"
published by BAROID DRILLING FLUIDS, INC., cf. in particular the Chapter entitled "Mud Testing - Tools and Techniques" and "Oil Mud Technology", which is freely available to interested experts. In the interests of fullness of disclosure, the following summary observations may be made:
Emulsifiers suitable for use in practice are systems which are capable of forming the required w/o emulsions.
Selected oleophilic fatty acid salts, for example those based on amidoamine compounds, are particularly suitable, examples being described in the already cited U.S. Patent No. 4,374,737 and the literature cited therein. One particularly suitable type of emulsifier is the product marketed under the name of "EZ-MULi'" by BAROID DRILLING
FLUIDS, INC.
Emulsifiers of the above type are marketed in the form of concentrates and can be used, for example, in quantities of from 2.5 to 5% by weight and more especially in quantities of from 3 to 4% by weight, based in each case on the ester oil phase.
In practice, organophilic lignite is used as a fluid-loss additive and forms an impervious coating in the form of a substantially water-impermeable film over the walls of the well. Suitable quantities are, for example, in the range of from 15 to 20 lb/bbl or in the range of from 5 to 7% by weight, based on the ester oil phase.
20~16~.(~
In drilling muds of the present type, the thickener normally used to create viscosity is a cationically modified, finely divided organophilic bentonite which can be used in quantities of from 8 to 10 lb/bbl or in the range of from 2 to 4% by weight, based on the ester oil phase. The weighting agent normally used in practice to establish the necessary pressure equalization is barite which is added in quantities adapted to the particular conditions to be expected in the well. For example, it is l0 possible by addition of barite to increase the specific gravity of the drilling mud to values of up to about 2.5 and preferably in the range from 1.3 to 1.6.
In invert drilling muds of the present type, the disperse aqueous phase is charged with soluble salts, generally calcium chloride and/or potassium chloride, the aqueous phase preferably being saturated with the soluble salt at room temperature.
The emulsifiers or emulsifier systems mentioned above can also be used to improve the oil wettability of the in-organic weighting materials. In addition to the amino-amides already discussed, alkyl benzenesulfonates and imi-dazoline compounds are further examples. Additional information on the relevant prior art can be found in the following literature references: GB 2,158,437, EP 229 912 and DE 32 47 123.
One important application for the new drilling fluids is in offshore drilling for the development of oil and/or gas sources, to provide technically useful drilling fluids of high ecological compatibility. The use of the new drilling fluids is of particular importance in, but is not limited to, the offshore sector. The new drilling fluids can also be used quite generally for land-supported drilling, including for example geothermal drilling, water drilling, geoscientific drilling and mine drilling. In this case, too, the ester-based drilling fluids selected in accordance with the invention basically simplify ecotoxic problems to a considerable extent. In addition, the zoosolo drilling fluids based in accordance with the invention on the co-use of ester oils of the described type are also distinguished by distinctly improved lubricity. This is particularly important when the path of the drill pipe and hence the well deviate from the vertical during drilling, for example at considerable depths. In such cases, the rotating drill pipe readily comes into contact with the well wall and embeds itself therein. Ester oils of the type used as oil phase in accordance with the invention have a distinctly better lubricating effect than the mineral oils hitherto used, which is an important advantage of the present invention.
The invention will be illustrated but not limited by the following examples.
EXAMPLES
An invert drilling mud was prepared using an undistil led isobutyl rapeseed oil ester as the continuous oil phase. This rapeseed oil ester was based on a mixture of predominantly unsaturated, straight-chain carboxylic acids which correspond substantially to the following distribution: 60% oleic acid, 20% linoleic acid, 9 to 10%
linolenic acid, olefinically unsaturated Czo-z2 monocarboxylic acids approximately 4%, remainder saturated monocarboxylic acids predominantly in the C~b_~8 range.
The rapeseed oil ester used had the following charac-teristic data: density (20'C) 0.872 g/cm3; pour point below -15°C; flash point (DIN 51584) above 180'C; acid value (DGF-C-V 2) 1.2; viscosity at 0°C 32 mPa.s, viscosity at 5°C 24 mPa.s; no aromatic compounds.
An invert drilling mud was conventionally prepared us-ing the following mixture constituents:
230 ml rapeseed oil fatty acid ester 26 ml water 6 g organophilic bentonite (GELTONEt", a product of BAROID DRILLING FLUIDS, INC. of Aberdeen, Scotland) 0.2 g lime 6 g water in oil emulsifier ("EZ-MULt'~~, a product of BAROID DRILLING FLUIDS, INC.) 340 g barite 9.2 g CaClz x 2H20 20 g organophilic lignite ("DURATONEL"'", a product of BAROID DRILLING FLUIDS, INC.) Plastic viscosity (PV), yield point (YP) and gel strength after 10 seconds and 10 minutes were first deter-mined on the material before ageing by viscosity measure-ment at 50°C.
The invert drilling mud was then aged for 16 h at 125°C in an autoclave in a so-called "roller oven" to determine the effect of temperature on the stability of the emulsion. The viscosity values were then redetermined at 50°C.
The following results were obtained:
Unaged Aged material material Plastic viscosity (PV) 35 62 Yield point (YP) 21 24 Gel strength (1b/100 ft2) 10 seconds 12 12 10 minutes 14 15 Another invert drilling mud was prepared in the same way as in Example 1, except that on this occasion the quan-tity of lime was increased to 4 g, i.e. drastically beyond the limit of approximately 2 lb/bbl.
Once again, the viscosity values and gel strength of the material were determined before and after ageing. The following results were obtained:
Unaged Aged material material Plastic viscosity (PV) 41 cannot be meas-ured Yield point (YP) 22 cannot be meas-ured Gel strength (1b/100 ft2) 10 seconds 11 74 10 minutes 17 72 Another invert drilling mud was prepared with a continuous oil phase. The oil phase consisted of distilled oleic acid isobutyl ester which has the following characteristic data: density (20°C) 0.86 g/cm3; viscosity (20°C) 8 to 10 mPa.s; pour point below -25°C; flash point (DIN 51584) above 185°C; acid value (DGF-C-V 2) below 1; no aromatic compounds.
A drilling mud of the following composition was prepared:
210 ml isobutyl oleate 6 g fatty-acid-based emulsifier (INVERMULtma product of BAROID DRILLING FLUIDS, INC.) 6 g organophilic bentonite (GELTONE Iltm a product of BAROID DRILLING FLUIDS, INC.) 13 g organophilic lignite (DURATONEt', a product of BAROID DRILLING FLUIDS, INC.) 1 g lime 3 g water in oil emulsifier (EZ-MULt', a product of BAROID DRILLING FLUIDS, INC.) 270 g barite 58.2 g saturated aqueous CaCl2 solution Plastic viscosity, yield point and gel strength after seconds and 10 minutes were determined before and after ageing (16h at 125°C in a roller oven) in the same way as in Example 1. The results obtained are shown below. In the 5 formulation used here, 1.9 g added lime substantially corresponds to the limit of 2 lb/bbl of alkali reserve.
Unaged Aged material material Plastic viscosity (PV) 46 41 Yield point (YP) 35 32 Gel strength (1b/100 ftz) 10 seconds 17 18 10 minutes 21 29 Another invert drilling oil emulsion was prepared using the formulation of Example 2, except that the addition of lime was increased to 2 g and hence to within the limit of about 2 lb/bbl of alkali reserve. The plastic viscosity, yield point and gel strength of the material before and after ageing are shown in the following:
Unaged Aged material material Plastic viscosity (PV) 53 46 Yield point (YP) 61 45 Gel strength (1b/100 ft2) 10 seconds 33 24 10 minutes 40 29
Claims (42)
1. An invert emulsion drilling mud free of mineral oil and substantially free from highly hydrophilic basic materials selected from the group consisting of alkali metal hydroxides and amines selected from diethanolamine and triethanolamine, consisting essentially of A. a continuous oil phase composed predominantly of at least one monocarboxylic acid ester of a C2-C12 monofunctional alcohol wherein the monocarboxylic acid contains from 16 to 24 carbon atoms and is olefinically mono- or poly-unsaturated, B. a disperse aqueous phase, C. at least one emulsifier, D. at least one weighting agent, E. a viscosifier, F. at least one fluid loss additive, and G. a mildly alkaline alkali reserve component consisting essentially of lime in a quantity not exceeding about 2 lb/bbl of said drilling mud.
2. The invert emulsion mud of Claim 1, wherein the disperse aqueous phase B contains at least one of CaCl2 or KCl as a dissolved salt.
3. The invert emulsion mud of Claim 1 or 2, wherein from 5 to 45a by weight of component B is present therein.
4. The invert emulsion mud of Claim 3, wherein from 10 to 25% by weight of component B is present therein.
5. The invert emulsion mud of any one of Claims 1 to 4, wherein component A has a Brookfield (RVT) viscosity at 0 to 5°C of below 50 mPa.cndot.s.
6. The invert emulsion mud of any one of Claims 1 to 5, wherein the invert emulsion mud has a plastic viscosity (PV) in the range of from 10 to 60 mPa.cndot.s and a yield point (YP) in the range of from 5 to 40 lb/100 ft2, as measured at 50°C.
7. The invert emulsion mud of any one of Claims 1 to 6, wherein component A also contains small quantities of esters of saturated monocarboxylic acids.
8. The invert emulsion mud of any one of Claims 1 to 7, wherein in component A the oil phase contains at least 70%
by weight of the at least one monocarboxylic acid ester.
by weight of the at least one monocarboxylic acid ester.
9. The invert emulsion mud of Claim 8, wherein 80% by weight of the at least one monocarboxylic acid ester is present.
10. The invert emulsion mud of Claim 8, wherein 90% by weight of the at least one monocarboxylic acid ester is present.
11. The invert emulsion mud of any one of Claims 1 to 10, wherein the at least one monocarboxylic acid ester of component A has a pour point and setting point below -10°C, and a flash point above 100°C.
12. The invert emulsion mud of Claim 11, wherein the pour point and setting point is below -15°C, and the flash point is above 160°C.
13. The invert emulsion mud of any one of Claims 1 to 12, wherein in component A the acid moiety of the at least one monocarboxylic acid ester contains at least 60% by weight of mono-olefinically unsaturated acids and no more than 35% by weight di- and poly-olefinically unsaturated acids.
14. The invert emulsion mud of any one of Claims 1 to 12, wherein in component A the acid moiety of the at least one monocarboxylic acid ester contains more than 45% by weight of either di-olefinically unsaturated acids, poly-olefinically unsaturated acids, or a mixture of di- and poly-olefinically unsaturated acids.
15. The invert emulsion mud of Claim 14, wherein said percentage is more than 55%.
16. The invert emulsion mud of any one of Claims 1 to 15, wherein in component A the continuous oil phase further contains no more than 20% by weight of esters of saturated C16-C18 carboxylic acids.
17. The invert emulsion mud of Claim 16, wherein said percentage is no more than 10% by weight.
18. The invert emulsion mud of any one of Claims 1 to 17, wherein in the at least one monocarboxylic acid ester of component A the monocarboxylic acid is linear.
19. The invert emulsion mud of any one of Claims 1 to 18, wherein the at least one monocarboxylic acid ester of component A the alcohol moiety contains from 3 to 10 carbon atoms and is saturated, and is straight chain or branched.
20. The invert emulsion mud of claim 1 wherein said lime is present in an amount of from 1 to 1.8 lbs/bbl of said drilling mud.
21. The invert emulsion mud of claim 1 wherein said alkali reserve component comprises a weakly basic metal oxide, zinc oxide, or zinc compound.
22. An invert drilling fluid that is free of mineral oil and is substantially free from highly hydrophilic basic materials selected from the group consisting of alkali metal hydroxides and amines selected from diethanolamine and triethanolamine, said fluid consisting of A. a continuous oil phase composed of at least one monocarboxylic acid ester of a C2-C12 monofunctional alcohol wherein the monocarboxylic acid contains from 16 to 24 carbon atoms and comprises at least about 60% by weight of mono-olefinically unsaturated acids and no more than about 35% by weight of di- and poly-olefinically unsaturated acids, B. a disperse aqueous phase, and C. a mildly alkaline alkali reserve component consisting essentially of lime in a quantity not exceeding above about 2 lb/bbl of said drilling fluid.
23 23. The drilling fluid of claim 22 wherein in component A
has a Brooksfield (RVT) viscosity at 0° to 5° C of below 50 mPa.cndot.s.
has a Brooksfield (RVT) viscosity at 0° to 5° C of below 50 mPa.cndot.s.
24. The drilling fluid of claim 22 wherein in component A
the oil phase contains at least about 70% by weight of the at least one monocarboxylic acid ester.
the oil phase contains at least about 70% by weight of the at least one monocarboxylic acid ester.
25. The drilling fluid of claim 22 wherein the at least one monocarboxylic acid ester of component A has a pour point and setting point below about -10 ° C, and a flash point above about 100°C.
26. The drilling fluid of claim 22 wherein in the at least one monocarboxylic acid ester of component A the monocarboxylic acid is linear.
27. The drilling fluid of claim 22 wherein in the at least one monocarboxylic acid ester of component A the alcohol moiety contains from 3 to 10 carbon atoms and is saturated, straight chain or branched.
28. An invert emulsion drilling mud free of mineral oil and substantially free from highly hydrophilic basic materials selected from the group consisting of alkali metal hydroxides and amines selected from diethanolamine and triethanolamine, consisting essentially of A. a continuous oil phase composed predominantly of at least one monocarboxylic acid ester of a C2-C12 monofunctional alcohol wherein the monocarboxylic acid contains from 16 to 24 carbon atoms and comprises at least about 60% by weight of mono-olefinically unsaturated acids and no more than about 35% by weight of di- and poly-olefinically unsaturated acids, B. a disperse aqueous phase, C. at least one emulsifier, D. at least one weighting agent, E. a viscosifier, F. at least one fluid loss additive, and G. a mildly alkaline alkali reserve component consisting essentially of lime in a quantity not exceeding about 2 lb/bbl of said drilling mud.
29. The invert emulsion mud of claim 28 wherein from about to about 45% by weight of component B is present therein.
30. The invert emulsion mud of claim 29 wherein from about to about 25% by weight of component B is present therein.
31. The invert emulsion mud of claim 30 wherein component A
has a Brookfield (RVT) viscosity at 0° to 5° C of below 50 mPa.cndot.s.
has a Brookfield (RVT) viscosity at 0° to 5° C of below 50 mPa.cndot.s.
32. The invert emulsion mud of claim 28 wherein the invert emulsion mud has a plastic viscosity (PV) in the range of from about 10 to about 60 mPa.cndot.s and a yield point (YP) in the range of from about 5 to about 40 lb/100 ft2, as measured at 50°C.
33. The invert emulsion mud of claim 28 wherein in component A the oil phase contains at least about 70% by weight of the at least one monocarboxylic acid ester.
34. The invert emulsion mud of claim 28 wherein the at least one monocarboxylic acid ester of component A has a pour point and setting point below about -10° C, and a flash point above about 100°C.
35. In the development of a source of oil or gas by drilling using a drilling mud, the improvement comprising pumping the invert emulsion mud of claim 2 into said source.
36. In the development of a source of oil or gas by drilling using a drilling mud, the improvement comprising pumping the invert emulsion mud of claim 6 into said source.
37. In the development of a source of oil or gas by drilling using a drilling mud, the improvement comprising pumping the invert emulsion mud of claim 11 into said source.
38. In the development of a source of oil or gas by drilling using a drilling mud, the improvement comprising pumping the invert emulsion mud of claim 13 into said source.
39. In the development of a source of oil or gas by drilling using a drilling mud, the improvement comprising pumping the invert emulsion mud of claim 1 into said source.
40. In the development of a source of oil or gas by drilling using a drilling mud, the improvement comprising pumping the invert emulsion mud of claim 28 into said source.
41. The invert emulsion mud of claim 19 wherein the alcohol moiety is branched and the monocarboxylic acid is predominantly oleic acid.
42. The invert emulsion mud of claim 41 wherein the monocarboxylic acid is derived from rape seed oil.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DE3842659A DE3842659A1 (en) | 1988-12-19 | 1988-12-19 | USE OF SELECTED ESTEROILS IN DRILLING RINSING, IN PARTICULAR FOR THE OFF-SHORE DEVELOPMENT OF PETROLEUM OR. NATURAL GAS DEPOSIT (I) |
| DEP3842659.5 | 1988-12-19 |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CA2006010A1 CA2006010A1 (en) | 1990-06-19 |
| CA2006010C true CA2006010C (en) | 2004-06-29 |
Family
ID=6369495
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002006010A Expired - Lifetime CA2006010C (en) | 1988-12-19 | 1989-12-19 | The use of selected ester oils in drilling fluids and muds |
Country Status (22)
| Country | Link |
|---|---|
| EP (2) | EP0374671B1 (en) |
| AR (1) | AR247911A1 (en) |
| AT (1) | ATE103627T1 (en) |
| AU (1) | AU639219C (en) |
| BR (1) | BR8907835A (en) |
| CA (1) | CA2006010C (en) |
| DE (2) | DE3842659A1 (en) |
| DK (1) | DK170786B1 (en) |
| ES (1) | ES2061909T3 (en) |
| GE (1) | GEP20001918B (en) |
| IE (1) | IE65152B1 (en) |
| MX (1) | MX174181B (en) |
| MY (1) | MY108504A (en) |
| NO (1) | NO171562B (en) |
| NZ (1) | NZ231827A (en) |
| PT (1) | PT92597B (en) |
| RO (1) | RO111579B1 (en) |
| RU (1) | RU2044025C1 (en) |
| TJ (1) | TJ195R3 (en) |
| TR (1) | TR24786A (en) |
| WO (1) | WO1990006980A1 (en) |
| ZA (1) | ZA899693B (en) |
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-
1988
- 1988-12-19 DE DE3842659A patent/DE3842659A1/en not_active Withdrawn
-
1989
- 1989-12-05 MY MYPI89001702A patent/MY108504A/en unknown
- 1989-12-11 EP EP89122819A patent/EP0374671B1/en not_active Revoked
- 1989-12-11 ES ES89122819T patent/ES2061909T3/en not_active Expired - Lifetime
- 1989-12-11 WO PCT/EP1989/001512 patent/WO1990006980A1/en not_active Application Discontinuation
- 1989-12-11 RO RO147837A patent/RO111579B1/en unknown
- 1989-12-11 NZ NZ231827A patent/NZ231827A/en unknown
- 1989-12-11 AU AU46551/89A patent/AU639219C/en not_active Expired
- 1989-12-11 GE GEAP19893716A patent/GEP20001918B/en unknown
- 1989-12-11 EP EP90900103A patent/EP0448579A1/en active Pending
- 1989-12-11 AT AT89122819T patent/ATE103627T1/en not_active IP Right Cessation
- 1989-12-11 DE DE89122819T patent/DE58907349D1/en not_active Revoked
- 1989-12-11 IE IE405689A patent/IE65152B1/en not_active IP Right Cessation
- 1989-12-11 BR BR898907835A patent/BR8907835A/en not_active IP Right Cessation
- 1989-12-15 PT PT92597A patent/PT92597B/en not_active IP Right Cessation
- 1989-12-18 MX MX018753A patent/MX174181B/en unknown
- 1989-12-18 ZA ZA899693A patent/ZA899693B/en unknown
- 1989-12-19 TR TR90/0006A patent/TR24786A/en unknown
- 1989-12-19 AR AR89315714A patent/AR247911A1/en active
- 1989-12-19 CA CA002006010A patent/CA2006010C/en not_active Expired - Lifetime
-
1991
- 1991-06-17 NO NO912337A patent/NO171562B/en not_active Application Discontinuation
- 1991-06-17 RU SU914895872A patent/RU2044025C1/en active
- 1991-06-18 DK DK117591A patent/DK170786B1/en not_active IP Right Cessation
-
1994
- 1994-12-30 TJ TJ94000025A patent/TJ195R3/en unknown
Also Published As
| Publication number | Publication date |
|---|---|
| IE65152B1 (en) | 1995-10-04 |
| BR8907835A (en) | 1991-10-22 |
| ATE103627T1 (en) | 1994-04-15 |
| ZA899693B (en) | 1990-08-29 |
| GEP20001918B (en) | 2000-01-05 |
| NO912337D0 (en) | 1991-06-17 |
| MY108504A (en) | 1996-10-31 |
| CA2006010A1 (en) | 1990-06-19 |
| EP0448579A1 (en) | 1991-10-02 |
| NO912337L (en) | 1991-06-17 |
| TR24786A (en) | 1992-05-01 |
| AU639219C (en) | 2003-11-13 |
| EP0374671A1 (en) | 1990-06-27 |
| MX174181B (en) | 1994-04-27 |
| RU2044025C1 (en) | 1995-09-20 |
| TJ195R3 (en) | 1998-10-28 |
| ES2061909T3 (en) | 1994-12-16 |
| WO1990006980A1 (en) | 1990-06-28 |
| EP0374671B1 (en) | 1994-03-30 |
| NZ231827A (en) | 1991-12-23 |
| DE3842659A1 (en) | 1990-06-28 |
| IE894056L (en) | 1990-06-19 |
| DK170786B1 (en) | 1996-01-15 |
| RO111579B1 (en) | 1996-11-29 |
| PT92597B (en) | 1995-09-12 |
| AR247911A1 (en) | 1995-04-28 |
| NO171562B (en) | 1992-12-21 |
| DK117591A (en) | 1991-08-13 |
| DE58907349D1 (en) | 1994-05-05 |
| PT92597A (en) | 1990-06-29 |
| AU4655189A (en) | 1990-07-10 |
| DK117591D0 (en) | 1991-06-18 |
| AU639219B2 (en) | 1993-07-22 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| EEER | Examination request | ||
| MKEX | Expiry |