NO179487B - Use of basic amine compounds as additive in water-in-oil invert drilling mud, the drilling mud obtained in use as well as additive for this - Google Patents

Abstract

A first embodiment of the invention concerns the use of basic amine compounds capable of forming salts with carboxylic acids and having a pronounced oleophilic character and minimal solubility in water, as additives in water-oil invert mineral oil muds. These compounds contain, in the closed oil phase, ester oils and, together with the disperse aqueous phase, emulsifiers, inert fillers, fluid-loss additives and, if desired, other additives to protect them from undesirable thickening in use and/or to improve their pourability. Another embodiment concerns water-oil invert mineral oil muds which are suitable for improved off-shore development of crude oil and natural gas deposits and the concomitant use of basic amine compounds which are capable of forming salts with carboxylic acids and are characterized by a pronounced oleophilic character.

Description

The present invention relates to the use of basic amine compounds suitable for salt formation with carboxylic acids as an additive in water-in-oil drilling mud.

The invention also relates to such drilling muds which are obtained using the amine compounds.

Finally, the invention relates to an additive for improving and aging protection of the pouring properties of the mud obtained.

An important area of application for the new drilling flushing systems is offshore drilling for the exploitation of oil and/or natural gas deposits, whereby the invention here particularly aims to provide technically usable drilling fluids with a high ecological tolerance.

The application of the new drilling flushing systems has particular importance in the maritime area, but should not be limited there. The new flushing systems are generally also used in land-based drilling, for example in geothermal drilling, water drilling, when carrying out geoscientific drilling or further also in the mining sector. In principle, however, it applies that the eco-toxic problems are greatly simplified with the aid of the invention's selected ester-based drilling oil fluids.

As is known, limited thickened, pourable water- or oil-based systems are used as liquid flushing systems for the lowering of rock bores during the simultaneous installation of triggered drill cuttings. These latter oil-based systems find increasing importance in practice, especially in the area of offshore drilling or when drilling through water-sensitive layers.

Oil-based drilling fluids are generally used as so-called invert emulsion muds, which consist of a three-phase system: oil, water and finely divided solids. This refers to preparations of the type water/oil emulsions, that is to say that the aqueous phase is heterogeneously finely dispersed and distributed in the continuous oil phase. For stabilization of the overall system and for setting the desired usage properties, a number of additives are aimed at, especially emulsifiers or emulsifier systems, weighting agents, fluid-loss additives, alkali reserves, viscosity-regulating substances and the like. When it comes to details, special reference should be made to P.A. Boyd et al. in "New Base Oil Used in Low-Toxicity Oil Muds", "Journal of Petroleum Technology", 1985, 137-142 as well as by E.B. Bennett, "New Drilling Fluid Technology - Mineral Oil Mud", "Journal of Petroleum Technology", 1984, 975-981, and the literature cited therein.

Oil-based drilling muds were first built up on the basis of diesel oil fractions with a content of aromatics. In order to remove toxins and reduce the resulting ecological problems, the aim was to use to a large extent aromatic-free hydrocarbon fractions, today known as "non-polluting oils", as a continuous oil phase, reference should be made here to the above-mentioned literature. Although in this way certain progress was achieved due to the exclusion of the aromatic compounds, a further reduction of the environmental problems caused by drilling mud of the type mentioned here seems to be required. This applies in particular when offshore drilling is carried out for the exploitation of oil or natural gas deposits, because the marine eco-system is particularly sensitive when it comes to the introduction of toxic and difficult-to-degrade substances.

Today's technology has long recognized the importance of ester-based oil phases to solve this problem. Thus, US-PS 4,374,737 and 4,481,121 describe oil-based drilling muds in which non-polluting oils could be used. As non-polluting oils are mentioned next to each other and as equivalent aroma-free mineral oil fractions and vegetable oils of the type peanut oil, soybean oil, 1 inseed oil, corn oil, rice oil, or also oils of animal origin such as whale oil. All the time, the ester oils mentioned here of vegetable or animal origin are triglycerides of natural fatty acids which, as is known, have a high environmental tolerance and which, in relation to hydrocarbon fractions, even when these are aroma-free, have superior properties with a view to ecological considerations.

Interestingly, however, there is no example in the above-mentioned US patents of the use of such natural ester oils in invert drilling mud of the type mentioned here. All the time, mineral oil fractions are mentioned as closed oil phase.

The investigations on which the present invention is based have shown that the use of easily degradable oils of vegetable and/or animal origin envisaged in the known technique cannot be considered for practical reasons. The rheological properties of such oil phases cannot be reconciled for the wide, practically required temperature ranges of 0 to 5°C on the one hand and up to 250°C and above on the other hand.

Ester oils of the type described here do not behave in the same way as the hitherto used mineral oil fractions on a pure hydrocarbon basis. Regardless of their constitution, ester oils undergo a partial hydrolysis in practical use also and precisely in the described water/oil invert drilling mud. Thereby, free carboxylic acids are formed. These in turn react with the alkaline components always present in the drilling flushing systems of the type described here, for example with the alkali reserves added for corrosion protection, to form the corresponding salts. Salts of strongly hydrophilic bases and the acids predominantly present in the oils of natural origin in the range c^ 2— 2i' are, however, as known, compounds with relatively high HLB values which in particular lead to a setting and stabilization of oil/water emulsions The washing and cleaning technique makes use of this to a large extent. However, the formation of even small amounts of such oil/water emulsifier systems must interfere with the water/oil emulsions required within the scope of the invention and thereby lead to disturbances.

The subject of the parallel applications NO 171.562-B and NO 171.601-B as well as the separate NO 172.129-B and NO 172.130-B is the use of ester oils on the basis of monocarboxylic acids selected in each case, respectively monocarboxylic acid mixtures and associated monofunctional alcohols. The older applications describe that with the esters or ester mixtures of monofunctional reactants described there, one can not only satisfactorily set the theological properties in the fresh drilling fluids, but that one can also work with the co-use of selected known alkali reserves in the drilling mud and in this way to always hold back unwanted corrosion. It is essential, according to the teaching according to these publications, with regard to the alkali reserve, that one waives the co-use of strongly hydrophilic bases such as alkali hydroxide and/or diethanolamine. As alkali reserves, the aim is the addition of lime (calcium hydroxide or lime) and/or the combined use of zinc oxide or comparable zinc compounds.

Here too, however, a further restriction is necessary. If the unwanted thickening of the oil-based invert flushing system is to be prevented in practical use, the amount of alkalizing additives and especially the amount of lime must be limited. According to what is described in the above-mentioned previous applications, the intended highest amount is assumed to be 5.706 g/l (2 lb/bbl).

The teachings of the present invention, in contrast, are based on theories and realizations which lead further and which are unknown in the area of the invert drilling mud described here with a continuous oil phase. The teaching of the invention takes into account the fact that ester oil-containing drilling mud of the type described here undergoes limited partial hydrolysis in practical operation and thereby invariably forms free carboxylic acids to an increasing degree as a hydrolysis product, which sooner or later reach a critical or at least risky aging state that results result in an unwanted thickening of the drilling mud. The teaching of the invention is based on the concept that one uses an additional additive in drilling mud of the type described here, which is suitable to keep the desired rheological data in the drilling mud within the required range even when more and more is formed or even too large amounts of free carboxylic acid by partial ester hydrolysis. The teaching of the invention is thereby not only to capture the resulting free carboxylic acids in a harmless form, but also, if possible, to convert these into valuable components with stabilizing or emulsifying properties for the overall system.

According to this and as mentioned at the outset, the object of the invention is the use of basic amine compounds suitable for salt formation with carboxylic acids, with a pronounced oleophilic nature and highly limited water solubility as an additive in water/oil invert drilling oil mud which in the closed oil phase contains ester oils of monofunctional C ±q-24carboxylic acids and monofunctional C2_i2alkon°ler °S together with the dispersed aqueous phase contain emulsifiers, weighting agents, fluid-loss additives and possibly further additives, for their protection against unwanted thickening in use and/or to improve pourability.

As mentioned at the outset, the invention also relates to water-in-oil invert drilling mud which is suitable for offshore extraction of petroleum and natural gas deposits and which, in a continuous phase of ester oils of monofunctional C^_24 carboxylic acids and monofunctional C2_i2 alcohols, contains a dispersed aqueous phase together with emulsifiers, bulking agents, fluid-loss additives and possibly further common additives, and this sludge is characterized by the fact that it also contains "basic amine compounds, suitable for salt formation with carboxylic acids, with a pronounced oleophilic character and very limited water solubility which additive for protection against unwanted thickening in use and/or for improving pourability.

Finally, as mentioned at the outset, the invention also relates to an additive for improving and especially aging protection of the pouring properties of water/oil invert drilling mud on the basis of a continuous oil phase containing an ester oil, which together with the dispersed phase contains emulsifiers, weighting agents, fluid loss -additives and possibly further additives, and this additive is characterized by the fact that it contains, in a dissolved state, the basic amine compounds suitable for salt formation with carboxylic acid of a distinctly oleophilic character and with very limited water solubility in a solvent miscible with the oil phase, preferably on a base of non-polluting oils and especially on the basis of ester oil.

As a solvent, so-called non-polluting oils are preferred, especially here again the ester oils come into consideration.

In material mixtures of the type mentioned here, the aging protection agent on the basis of the oleophilic basic amine compounds suitably occurs in concentrations of at least approx. 20 weight #, and preferably in quantities of approx. 50 pounds weight.

The core of the teachings of the invention in all of its embodiments is the recognition that in practical use during partial hydrolysis of the ester oils the inevitably free carboxylic acid can be captured by the co-use of the invention's defined aging protection agents based on oleophilic basic amine compounds, without there being a disturbance of the rheological properties in the invert sludge. By choosing suitable amine compounds, it is thereby even possible, with the help of the now occurring salt formation, to form valuable stabilizing and/or emulsifying mixture components in situ. The oleophilic basic amine compounds can be added to the drilling fluid systems from the start and/or can be added during use. It has been shown that by adding or co-using the basic oleophilic amine compounds used according to the invention, it is even possible to freshen up already aged and undesirably thickened drilling fluid systems of the type described here to such an extent that the rheology is lowered to that for pumpability and pourability as well at low temperatures, the required area.

In connection with the use of the additives defined according to the invention, a further important relief has been shown in the build-up of water/oil drilling mud: The necessary alkalization of the drilling mud for corrosion prevention and especially the preparation of a sufficient alkali reserve, especially against the intrusion of acidic gases such as C0£ and/or H2S, become unproblematic. The distinctly oleophilic basic amine compounds proposed as additives according to the invention form by themselves a basicity buffer which can be used as an alkali reserve. More important is the surprising realization that the co-use of conventional alkali reserves and here in particular the co-use of the particularly inexpensive lime, at least to a large extent becomes problem-free when at the same time aging protection additives according to the invention are present in the drilling mud. The previously mentioned limit value of approx. 2 lb/bbl (lime/oil flushing) for flushing systems based on ester oils, and which is mentioned in the older applications, can usually be exceeded without problems when the distinctly oleophilic basic amine compounds within the scope of the invention are present in the oil sludges. Even when unwanted thickenings form when using conventional strongly hydrophilic alkali reserves, these can be set aside again by incorporating the additive components of the invention into the overall system.

In what follows, some detailed information is first summarized with a view to the invention's selected basic amine compounds with a pronounced oleophilic nature.

Basic amine compounds with shorter hydrocarbon chains are known to be water-soluble to a considerable extent and also water-miscible in any proportion. In contrast, the selected amine compounds of the invention are characterized by a typically limited water solubility with simultaneous development of the oleophilic character. Their water solubility at room temperature is generally below approx. 10 weight-# and in the preferred embodiment does not exceed the value approx. 5 weight #. Important above all are such oleophilic amine compounds which have very low limit values for water solubility at room temperature. An important limit value is approx. 1 weight #, preferably at less than approx. 0.1 weight #. Basic amines which are particularly important for the invention can be considered to be practically water insoluble.

Oleophilic amines of the type described are generally usable to the extent that they have the ability to form salts with the carboxylic acid released by ester hydrolysis and are preferably soluble in the oil phase. Within the framework of the purpose of the invention, to trigger the lowest possible environmental impact, in this large area of objectively suitable amine compounds, ecologically relatively harmless compounds are preferred. Aromatic amines are generally less suitable from such considerations, so that within a further preferred embodiment of the invention, oleophilic amine compounds are used which are at least predominantly free of aromatic components. Suitable compounds for carrying out the teachings of the invention can generally be assigned to the group of aliphatic, cycloaliphatic and/or heterocyclic amines. The respective representatives can thereby contain one or more N groupings which can form salts with carboxylic acids. Amine compounds of the type described can be nitrogen-containing saturated hydrocarbon compounds, however, amine hydrocarbons are also suitable which contain one or more olefinically unsaturated groups in their hydrocarbon links.

There is a great deal of freedom when choosing the specific constitutions of the amine components used in the invention. Economic considerations here largely determine the choice of the specific components in each case. In general, particularly suitable representatives can be assigned in practice to the following classes: At least largely water-insoluble, primary, secondary and/or tertiary amines, corresponding to the aminoamide and/or heterocycles containing nitrogen as a ring component. Particularly suitable can be such amine bases which exhibit at least one long-chain hydrocarbon residue with preferably approx. 8 to 36 C atoms and especially with approx. 10 to 24 C atoms in the molecule. Such hydrocarbon residues can attack immediately on the nitrogen atom. However, they can also, for example in the case of amino amides, be bound via a functional group on an N-containing molecular part, thereby ensuring that there is at least one basic N atom in the overall molecule that has the ability to form salts with the carboxylic acid released during ester hydrolysis. Characteristic examples for the general classes mentioned here shall be described in detail below.

A first group includes primary, secondary and tertiary amines with one or more N atoms, whereby in the respective compounds, the ratio between hydrocarbon groups and amine groups is chosen so that the previously given conditions for limited water solubility and pronounced oleophilicity are met. In certain, unsubstituted compounds of the type described here, the numerical ratio C:N amounts to at least approx. 5 or preferably 6, however, is preferably above that. In large quantities of readily available amines of the type described here, there are often one or two comparatively long-chain hydrocarbon residues and, possibly other methyl residues, on the amino nitrogen. Typical examples of the type described here contain per molecule a nitrogen atom. Technically readily available, however, are also comparable compounds derived from polyfunctional amines, especially lower diamines, for example from ethylenediamine or propylenediamine. Lower polyamines of the type described here are very water-soluble. If, however, one or more long-chain hydrocarbon residues of the type described above are introduced into the molecule, suitable additives arise within the context of the invention as long as at least one nitrogen atom has the ability to form salts with the carboxylic acid. Suitable representatives for this technique are, for example, compounds with the general formula R-NH-(CH2)n-NH2. Here, R means, for example, a Cg_22 hydrocarbon residue and n a lower number to, for example, 6, for example 2 to 4.

Primary and possibly also secondary amines with strong oleophilic molecular constituents can even be used within the scope of the invention when oligo-alkoxide groups have been introduced to the present NH groups, by alkoxylation with, for example, ethylene oxide and/or propylene oxide, respectively higher homologues, for example butylene oxide. Thus, for example, long-chain primary and/or secondary amines are sufficiently oleophilic even when introducing up to approx. 8-10 EO and/or PO groups so that they can find application within the context of the invention.

Technically readily available amine compounds for use within the framework of the invention are derived from epoxidation of olefinically unsaturated hydrocarbon compounds with the subsequent introduction of the N function by addition to the epoxide group. Of particular importance here is the reaction of the epoxidized intermediate components with primary and/or secondary amines during development of the corresponding alkanolamines. Polyamines are also suitable for opening the epoxide ring, especially lower polyamines of the type corresponding to alkylenediamines.

A further important class of the oleophilic amine compounds for the purposes of the invention are amino amides which derive from preferably long-chain carboxylic acids and polyfunctional especially lower amines of the above-mentioned type. It is essential here that at least one of the amino functions is not bound in amide form, but remains as a potentially salt-forming basic amino group. Both here and in the previously described cases, the basic amino groups when formed as secondary or tertiary amino groups in addition to the oleophilic molecular part can exhibit hydroxyalkyl substituents and here especially lower hydroxyalkyl substituents with up to 5 and preferably up to 3 C atoms. Suitable N-basic starting components for the production of such addition products with long-chain oleophilic molecular components are monoethanolamine and/or diethanolamine. Thus, suitable additives within the scope of the invention and in a preferred embodiment are reaction products from epoxidation of long-chain olefins with, for example, 8 to 36 and especially approx. 10 to 18 C atoms and mono- and/or diethanolamine. oc-standing olefins of the aforementioned type can be of particular importance as starting material for epoxidation and the subsequent conversion to secondary and/or tertiary amines with hydroxyalkyl groups on the N atom.

An important class of heterocyclic additives for regulating the flow properties of drilling mud within the framework of the invention are the imidazoline compounds. Likewise, alkylpyridines can be of importance from this heterocyclic group.

The additives based on oleophilic basic amine compounds within the scope of the invention are added to the drilling fluids preferably in amounts of no more than approx. 10 lb/bbl, and preferably in quantities not exceeding 5 lb/bbl (Conversion factor: 1 lb/bbl = 2.8530 g/l). The added quantity can be determined, among other things, by the form of the intended application in practice. Here it is possible with different variants that can also be connected to each other.

In a first embodiment, the rheology-regulating additive is added to the drilling muds from the very beginning and in significant quantities. It can thereby take on a dual function. On the one hand, it forms the alkali reserve in the drilling mud to capture any intrusions of acidic components such as CO2 or H2S, on the other hand, it absorbs the basic amine compound present in any strong excess, the carboxylic acid produced by hydrolysis as it is formed and transfers this to the corresponding oil-soluble salts. In the opposite borderline case, the invention first works with the ester oil-based sludge without the addition of the invention's additives, for example according to the teaching that appears from the above-mentioned older publications. If there is an aging of the drilling mud which is noticeable by an initial increase in the viscosity values, the additive of the invention is dosed to regulate the rheology in the drilling mud step by step or continuously. This can happen without difficulty during drilling. It is obvious that between these two extreme possibilities there are numerous combinations for dosing the additive of the invention before and during the drilling or the use of the drilling mud. By choosing amine compounds that form suitable effective emulsifier systems, it is even possible to save emulsifier shares in the oil share that is fed to gradually and instead of settling for the in situ formed amine salt with an emulsifier effect to stabilize the overall system.

The amine compounds can be added to the invert drilling muds in an immediate or intermediate manner. Thus, they can be incorporated into the ester oil-containing oil phase from the beginning or they can be added to the total system as such. In a particularly suitable embodiment, additive concentrates are prepared which can then, especially during continuous operation, be added to the drilling mud. This refers to solutions of the oleophilic amine compounds in suitable solvents at preferred concentrations of the additive of at least approx. 20 weight-# and preferably at least approx. 50 weight #. Non-polluting oils that can be incorporated homogeneously into the drilling mud should be mentioned as suitable solvents. Particularly suitable, however, are ester oils and especially those described in the previously mentioned applications.

As already mentioned, it is an important advantage of the invention that the combined use of the additives of the invention for regulating the pourability and pumpability of drilling mud, also with oil phases based on ester oils, opens up the possibility of also using conventional alkali reserves in such quantities that until now was only possible for drilling oil mud based on mineral oils as oil phase. Thus, for example, lime can be added in quantities of up to 5 lb/bbl without having to fear damage to the drilling mud during operation. The same also applies to the zinc compounds mentioned in the older publication such as zinc oxide, zinc complex compounds and the like. Surprisingly, however, even strongly hydrophilic bases from the previous practice of alkalizing drilling mud can also be used. If the alkali reserve is ensured in the described manner by conventional means, for example by co-using not insignificant amounts of lime, the amount of the invention's selected amine-based additive can be lowered to the range that is necessary due to the ester saponification during continuous operation. In an important embodiment, one only works there each time with a slight excess of oleophilic amine base and doses the proportion consumed during salt formation step by step or continuously during drilling. In such embodiments, the addition of amine base can, for example, be in the range of 0.1 to 2 lb/bbl (amine base/bore flush) or even below.

Particularly suitable ester oils are esters of monofunctional carboxylic acids, respectively carboxylic acid mixtures and monofunctional alcohols, especially the ester types mentioned individually in the previously mentioned applications. In order to complete the description of the invention, essential characteristic data for such esters or ester mixtures shall be briefly summarized here.

In a first embodiment, in the temperature range from 0 to 5°C, pourable and pumpable esters of monofunctional Cg-12 alcohols are used, especially with C^^-al^o^ols and aliphatically saturated C 2_i6 monocarboxylic acids eHere their mixtures with at most approx. equal amounts of other monocarboxylic acids, as oil phase. Preference is hereby given to ester oils which, at least 1, an amount of approx. 60 weight-Sb, calculated on the carboxylic acid mixture, is to lead back to esters of aliphatic C12_14-monocarboxylic acids and possibly what concerns the rest is to lead back to subordinate amounts of shorter-chained aliphatic and/or longer-chained and then especially once and/or several times olefinic, unsaturated monocarboxylic acids. Preferably, esters are used which, in the temperature range from 0 to 5°C, have a Brookfield-RVT viscosity within the range not exceeding 50 mPas, and preferably not exceeding 40 mPas, in particular at most approx. 30 mPas. The esters used in drilling mud exhibit solidification values (pouring and solidification points) of below -10*C, preferably below -15°C, and thereby particularly have flash points above 100°C and most preferably above 150°C. The carboxylic acids present in the ester or the ester mixture are at least predominantly straight-chain and thus preferably of vegetable type. They can be derived from similar triglycerides such as coconut oil, palm kernel oil and/or babassu oil. The alcohol residues for the esters used derive in particular from straight-chain and/or branched saturated alcohols with preferably 4 to 10 C atoms. These alcohol components can also be of vegetable and/or animal origin and thereby be obtained by reductive hydration of corresponding carboxylic acid esters.

A further class of particularly suitable ester oils are derived from olefinically mono- and/or polyunsaturated C1-24-monocarboxylic acids or their mixtures with minor amounts of other, especially saturated monocarboxylic acids and monofunctional alcohols with preferably 2-12 C atoms. These oils are also pourable and pumpable in the temperature range 0-5°C. Particularly suitable are esters of the type which in an amount of more than 70% by weight, preferably more than 80% by weight and most preferably more than 90% by weight, are derived from olefinically unsaturated C-j^. 24-carboxylic acids.

Here too, the solidification values (pour and solidification point) are below -10°C, preferably below -15°C, while the flash point is above 100°C and preferably above 160°C. The esters used in the drilling mud exhibit in the temperature range 0-5°C a Brookfield-RVT viscosity of no more than 55 mPas, preferably no more than 45 mPas.

For ester oils of the type in question here, two subclasses can be defined. In the first, the unsaturated C^g^-monocarboxylic acid residues present in the ester originate in an amount of no more than 35% by weight from doubly and more times olefinically unsaturated acids whereby preferably at least approx. 60 wt-56 of the acid residues are once olefinically unsaturated. In the second embodiment, the monocarboxylic acids present in the ester mixture originate in an amount of more than 45% by weight and preferably more than 55% by weight from di- and/or doubly olefinically unsaturated acids. In the ester mixture present saturated carboxylic acids from the range Ci£,_ig suitably amount to no more than approx. 20 weight-56 and preferably no more than approx. 10 weight-56. Preferably, however, saturated carboxylic acid esters lie in the range of lower carbon numbers in the acid residue. Here, too, the present carboxylic acid residues are at least predominantly straight-chain and thereby preferably of vegetable and/or animal origin. Vegetable starting materials are, for example, palm, peanut, castor and especially beet oil. Carboxylic acids of animal origin are especially the corresponding mixtures of fish oil such as herring oil. Invert drilling mud of the type described here usually contains, together with the closed oil phase, the finely dispersed aqueous phase in amounts of approx. 5 to 45 weight # and preferably in quantities of approx. 5 to 25 weight-56. The area of approx. 10 to 25 wt-# of dispersed aqueous phase may be of particular importance.

For the rheologically preferred invert drilling mud within the scope of the invention, the following rheological data apply: Plastic viscosity (PV) in the range of approx. 10-60 mPas, preferably approx. 15-40 mPas; yield point (Yield Point YP) in the area approx. 5-40 lb/100 ft2, preferably approx. 10-25 lb/ft2 , all determined at 50°C (Conversion factor: 1 lb/100 ft<2> = 2.0885 Pa). When it comes to the determination of these parameters and the measurement methods used thereby, as well as for the otherwise common compositions of the invert drill flushes described here, what is stated in the known technique applies in simplicity as it is stated at the beginning and described in detail, for example in the manual " Manual Of Drilling Fluids Technology" from the company NL-Baroid, London, GB, there especially under the chapter "Mud Testing - Tools and Techniques" as well as "Oil Mud Technology", which is freely available to the interested professional world. As a summary, to complete the description of the invention, the following can be said: Practically usable emulsifiers are systems which are suitable for forming the required water/oil emulsions. Specially selected oleophilic fatty acid salts, for example those based on amidoamine compounds, come into consideration. Examples of these are described in the above-mentioned US-PS 4,374,737 and the literature indicated there. A particularly suitable type of emulsifier is the product which is commercially available from the company NL Baroid, London, under the commercial name "EZ-mul".

Emulsifiers of the type described here are available commercially as highly concentrated active ingredient preparations and can be used in amounts of approx. 2.5-5 weight #, especially in quantities of approx. 3-4% by weight, all calculated on the ester-oil phase.

As a fluid-loss additive and thereby especially for the formation of a thick coating on the drill walls with a largely liquid-impermeable film, particularly hydrophobic lignite is used in practice. Suitable amounts are, for example, in the range of approx. 15-20 lb/bbl or in the area of approx. 5-7 weight #, calculated on the ester oil phase.

In drilling mud of the type described here, the usually used viscosity former is a cationically modified, finely divided bentonite which can especially be used in amounts from approx. 8 to 10 lb/bbl or in the range of approx. 2-4 weight #. The generally used weighting agent for setting the necessary pressure equalization is baryte, the amount of which is added to the expected conditions in the borehole. By adding baryte, for example, it is possible to raise the specific weight of the drilling mud to values in the range of approx. 2.5, preferably within the range of approx. 1.3-1.6.

The dispersed aqueous phase is filled with soluble salts in invert drilling mud of the type in question here. Predominantly calcium chloride and/or potassium chloride are used here, whereby saturation of the aqueous phase with the soluble salt at room temperature is preferred.

The previously mentioned emulsifiers or emulsifier systems may also serve to improve the oil wettability of the inorganic bulking agent. Alongside the already mentioned amino amides, alkylbenzene sulphonates and imidazoline compounds should also be mentioned as further examples. Further information for the current known technique can be found in GB 2 158 437, EP 229 912 and DE 32 47 123.

In addition to the advantages already mentioned, the invention's drilling mud, which is built up by the combined use of the ester oil of the type described, is characterized by a clearly improved lubricity. This is particularly important in such cases where the borehole exhibits deviations from the vertical line. The rotating drill string thus easily comes into contact with the borehole wall and digs into it during operation. Ester oils which, according to the invention, are used as the oil phase, have a clearly better lubricating effect than the mineral oils currently used. In this lies a further important distribution for the object of the invention.

EXAMPLES

In the following examples, two typical ester oils are used as the oil phase in the invert drilling muds. In both cases, it concerns monocarboxylic acid/monoalcohol esters which are characterized as follows: Examples 1 to 3: Distilled n-hexyl lauric acid ester with the following characteristic values: Flash point above 165°C, pour point below -5°C, density (20° C) 0.857 to 0.861, iodine number and acid number always below 1, water content below 0.3$ and the following viscosity values (Brookfield mPas) in deep temperature ranges: -5°C 22.5-25.5, +2°C 15-18; +5°C 15-18; -10°C about 15; 20°C 12-14.

Examples 4 to 10: Isobutyl beet oil esters based on a mixture of predominantly unsaturated straight-chain carboxylic acids approximately corresponding to the following distribution: 60$ oleic acid, 20$ linoleic acid, 9-1056 linolenic acid, olefinically unsaturated C2Q 22-monocarboxylic acids approx. 4$, the remainder being saturated monocarboxylic acids, predominantly from the range C16 lg.

The beet oil ester used also has the following characteristic data: Density (20°C) 0.872 g/cm5 ; pour point below -15°C; flash point (DIN 51584) above 180°C; acid value (DGF-CV 2) 1.2; viscosity at 0'C 32 mPas, viscosity at 5°C 24 mPas.

An invert drilling mud is prepared in a conventional manner using the following mix ingredients:

First, the plastic viscosity in mPas (PV), the yield strength in mPas (YP) and the gel strength after 10 seconds and 10 minutes respectively were determined from the tested invert drilling fluids by viscosity measurements at 50°C on non-aged material (where 1 lb/100 ft<2> = 2.0885 Pa).

The invert drilling mud was then placed for 16 hours at 125°C in an autoclave in a so-called "Roller oven" and aged there to determine the effect of temperature on emulsion stability. The viscosity values were then determined again at 50°C.

, Example 1

They worked with lauric acid/n-hexyl ester as the oil phase. Lime was added in an amount of 2 g of the indicated framework recipe. Thereby, without the addition of a basic amine with a pronounced oleophilic character, the work was within the scope of the invention's definition. The following values were determined on unaged and aged material:

Already by aging for just 16 hours at 125°C, a significant thickening of the drilling mud occurs. The amount of lime used is above the threshold value of 2 lb/bbl.

Example 2

To the invert drilling mud according to example 1, 0.5 g of a distinctly oleophilic basic amine was additionally added. As basic amine, the reaction product of an epoxidized C^g i4~a" olefin and diethanolamine ("Araphen G2D" from the applicant's company) is used.

The rheological data determined on unaged and aged materials are as follows:

Example 3

The scheme from example 2 is repeated, however, the oleophilic basic amine ("Araphen G2D") is added to the invert drill flushing in an amount of 1 g. The values determined in non-aged and in aged material are as follows:

Comparison of examples 1 to 3 clearly shows the stabilizing effect of an addition of an oleophilic basic amine within the definition of the invention.

Example 4

In this and in the following examples 5 to 9, the isobutyl beet oil ester defined above is used as the continuous oil phase.

In the present example 4, one first works without the addition of lime, but with the addition of 2 g of the above-defined oleophilic basic amine ("Araphen G2D"). The values determined on unaged and aged material are as follows:

Example 5

The addition according to example 4 is repeated, but here stearylamine is used as oleophilic basic amine in an amount of 2 g. The values determined on non-aged and aged material are as follows:

Example 6

For the sake of comparison, 1 g of lime is added to the isobutyl beet oil ester, although without simultaneously using an oleophilic basic amine compound. The quantity of 1 g of lime used in the framework recipe is below the threshold value of 2 lb/bbl, which in the recipe used here corresponds to an addition of approx. 1.35 g lime.

The rheological values determined on non-aged and aged material are as follows:

Example 7

The recipe from example 6 is repeated except that 2 g of the oleophilic basic amine compound "Araphen G2D" are also added. The rheological values determined for this drilling mud are as follows:

Example 8

An isobutyl beet oil ester is again examined without co-use of the oleophilic basic amine, but with the addition of 2 g of lime to the framework recipe. The measured rheological data are as follows:

Comparison of this example 8 with the above-mentioned example 6 shows the weighty thickening effect which is triggered by increasing the amount of lime above the threshold value of approx.

2 lb/bbl on aging.

Example 9

To an invert drilling mud according to example 8, 2 g of "Araphen G2D" is additionally added. The rheological values determined on non-aged and aged material are as follows:

The comparison with rheology data from example 8 shows the influence of the oleophilic basic amine compound added according to the invention.

Example 10

To an invert drilling mud according to example 8, 2 g of diethylenetriamine is additionally added, i.e. with a distinctly hydrophilic base. The rheological values of non-aged material are then determined.

This invert sludge is then aged as previously indicated for 16 hours at 125° C. It turns out that the sludge is so strongly thickened that it is not possible to numerically determine the available rheology data.

2 g of the oleophilic basic amine compound "Araphen G2D" is now added to the thickened mass and this substance mixture is aged again for 16 hours at 125°C in the Roller oven. A liquefaction of the thickened mass occurs, which enables a metrological determination of the available rheology data.

In total, the following values are determined:

Claims (19)

1. Application of basic amine compounds suitable for salt formation with carboxylic acids with a distinctly oleophilic nature and highly limited water solubility as an additive in water/oil invert drilling oil mud which in the closed oil phase contains ester oils of monofunctional C^o_24 carboxylic acids and monofunctional C2-12 alcohols and together with the dispersed aqueous phase contains emulsifiers, weighting agents, fluid-loss additives and possibly further additives, for their protection against unwanted thickening in use and/or to improve pourability. 2. Use according to claim 1 of the basic and thereby oleophilic amine compounds at the same time, at least partially, as alkali reserve for the invert drilling mud. 3. Use according to claims 1 and 2 of the oleophilic basic amines are used together with conventional alkali reserves, especially together with lime. 4. Use according to claims 1 to 3 of oleophilic amine compounds which are at least predominantly free of aromatic components. 5 . Use according to claims 1 to 4 of optionally olefinically unsaturated aliphatic, cycloaliphatic and/or heterocyclic oleophilic basic amine compounds which contain one or more N groupings which can form salts with carboxylic acids. 6. Use according to any one of claims 1 to 5, of basic amine compounds whose water solubility at room temperature is at most 5 wt-# and which is preferably below 1 wt-# and especially below 0.1 wt-#. 7. Use according to claims 1 to 6 of at least largely water-insoluble primary, secondary and/or tertiary amines which may also be limited alkoxidized and/or substituted with hydroxyl groups in particular. 8. Use according to claims 1 to 7 of basic amine compounds which at least have a long-chain hydrocarbon residue with 8 to 36 C atoms and preferably 10 to 24 C atoms, and which can also be one or more times olefinically unsaturated. 9. Use according to claims 1 to 8 of the oleophilic basic amine compound in an amount in the drilling mud in amounts up to 20.885 Pa (10 lb/bbl), preferably in amounts up to 10.442 Pa (5 lb/bbl) and especially in the range 0.209 to 5.706 ( 0.1 to 2 lb/bbl). 10. Use according to any one of claims 1 to 9, of the oleophilic basic amine compounds in drilling mud which at least partially contain ester oils of monofunctional alcohols and monofunctional carboxylic acids of natural origin with 8 to 24 C atoms. 11. Water/oil invert drilling mud which is suitable for offshore extraction of petroleum or natural gas deposits and which in a continuous phase of ester oils of monofunctional C()_ 24carboxylic acids and monofunctional C2_i2alkonols> contains a dispersed aqueous phase together with emulsifiers, weighting agents, f fluid loss additives and possibly further common additives, characterized by the fact that they also contain basic amine compounds, suitable for salt formation with carboxylic acids, with a pronounced oleophilic character and very limited water solubility as an additive for protection against unwanted thickening in use and/or for improving the pouring ability. 12. Drilling mud according to claim 11, characterized in that the oleophilic basic amine compounds constitute at least the predominant proportion of the alkali reserve in the drilling mud and/or are present in a mixture with conventional alkali reserves, especially together with lime. 13. Drilling mud according to claims 11 and 12, characterized in that as a drilling mud rheology protective additive there are possibly oleophilic unsaturated, aliphatic, cycloaliphatic and/or heterocyclic basic amine compounds with an oleophilic character which exhibit one or more N-grouping rings which can form salts with carboxylic acids. 14. Drilling mud according to claims 11 to 13, characterized in that there are basic amine compounds with a water solubility at room temperature of at most approx. 5 weight-5é and preferably below approx. 1 weight #. 15 . Drilling mud according to claims 11 to 14, characterized in that, as a rheology-protecting additive, there are at least largely water-insoluble primary, secondary and/or tertiary amines which can also be limited carboxylated and/or substituted with hydroxyl groups in particular, corresponding to amino amides and heterocycles with N as a ring component. 16. Drilling mud according to claims 11 to 15, characterized in that the additive contains "basic amine compounds which at least have a long-chain hydrocarbon residue with preferably 8 to 36 C atoms, especially with 10 to 24 C atoms, whereby these residues can also be a - and/or several times olefinically unsaturated. 17. Drilling mud according to claims 11 to 16, characterized in that the oleophilic basic amine compound is present in drilling mud in amounts of approx. 20.885 Pa (10 lb/bbl), preferably however not above approx. 10.442 Pa (5 lb/bbl). 18. Drilling fluid according to claims 11 to 17, characterized in that the ester oil phase at least partially contains esters of monofunctional carboxylic acids with at least predominantly 12 to 24 C atoms. 19. Additive for improvement and especially aging protection of the pouring properties of water/oil invert drilling mud on the basis of a continuous oil phase containing an ester oil, which together with the dispersed phase contains emulsifiers, weighting agents, fluid-loss additives and possibly further additives, characterized by that in a dissolved state it contains the basic amine compounds suitable for salt formation with carboxylic acid of distinctly oleophilic character and with very limited water solubility in a solvent miscible with the oil phase, preferably on the basis of non-polluting oils and especially on the basis of ester oil.