NO811848L - APPLICATION OF MIXTURES OF BETAINES OR AMINOXIDES AND POLYOXYTHYLETE ESTERS OF NITPHONIC ACIDS DURING OIL OIL TRANSPORT - Google Patents

Abstract

1. Use of a mixture of a) surface-active betaines which contain, as the hydrophilic radical, at least one quaternary ammonium group which is capable of forming an intramolecular salt with a carboxyl group or sulphonic acid group, and, as the oleophilic radical, at least one radical derived from naphthenic acids or amine oxides of the general formula see diagramm : EP0043495,P8,F1 in which R**1 is a naphthenoyl radical, R**6 is an alkylene radical having 2 to 5 carbon atoms, and R**7 and R**8 are identical or different and represent a methyl or ethyl radical, and b) polyoxyethylene esters of naphthenic acids, the ester having a molecular weight of 500-3,000, in an a) : b) weight ratio of 10:90 to 90:10 ; as surfactants for tertiary oil recovery.

Description

In crude oil transport, especially the secondary and tertiary crude oil transport, surfactants play a significant role. The petroleum sulphonates used here primarily have the advantage of low price, but the disadvantage of their sensitivity to polyvalent cations in particular. Thus, the calcium and magnesium salts of these compounds are no longer water-soluble and dissolve preferentially in the oil phase. As, however, oil and salt storage sites are often found together and the water that is located

at the storage site has a high electrolyte content, the above-mentioned cheap sulphonates are only usable within these limits set by their solubility.

One has also already used cation-active border surfactants such as e.g. quaternary ammonium salts, derivatives of fatty amines, polyamines. However, these compounds again have the disadvantage of substantivity on particularly silicate rock. They lose their effect upon absorption.

The known non-ionic surfactants certainly have the advantage of relative insensitivity to electrolytes, although with the help of electrolytes their solubility in water is likewise reduced and do not show the pronounced substantivity of cation-active compounds. However, this class of compounds, especially the addition products of ethylene oxide to compounds with active hydrogen, are relatively expensive, have limited activity and also affect the disemulsification of the transporting oil/water emulsion.

Detailed literature on the most important surfactants used to date can be seen in "Enzyklopadie der technischen Chemie" by Ullmann, 6th volume, page 468 ff.

The characteristic properties of non-ionic surfactants include the formation of so-called separation or cloud points (cloud points) which can be regarded as the temperature ranges of a phase separation that is visible to the naked eye (separation to flocculation). This phenomenon has, among other things, its basis in the formation of giant micelles and the achievement of temperature-dependent solubility limits. As the solubility of non-ionic surfactants is, according to the general opinion, primarily determined by the hydration of the ethoxy groups, an increase in temperature leads to partial dehydration which finally ends in phase separation.

The position of cloud points of non-ionic surfactants is only slightly dependent on the effective substance concentration, but is affected by e.g. strongly of electrolytes, namely is reduced.

Since at most oil storage sites the field temperature is far above the cloud point of non-ionic surfactants and, moreover, the use of relatively high-molecular HLB-directed products is severely limited due to the solubility limits, purely non-ionic surfactants can only be used conditionally because at the temperature of the cloud point (separation temperature) the surfactant solution separates into unstoichiometrically composed surfactant-rich resp. surfactant-poor mixed phases. Thereby, however, the division of substances between the water and oil phase, which is necessary for a correct HLB setting, is lost. There is also the possibility that self-solubilization of the tensides in the phases is no longer sufficient and, as a result, flocculation occurs. The remaining amount of residual surfactant is then no longer sufficient for interfacial tension lowering.

Depending on the chemical structure, solubilized hydrocarbons can both increase and decrease the cloud points.

It is known that a mixture of two non-ionic surfactants has a cloud point which roughly corresponds to the mean value of the cloud points of the starting surfactants.

The combination of non-ionic and ionic surfactants generally raises the position of the cloud point. Both mentioned effects are due to the formation of mixed micelles.

From German patent 25 32 469, it is known the use of surface-active betaines in crude oil production which, as a hydrophilic residue, have at least one quaternary ammonium group which intramolecularly is capable of internal salt formation with an acid group, preferably with a carboxyl group, and which as an oleophilic residue has at least one from naphthenic acids derived residue.

Among naphthenic acids is thereby understood the natural acids formed in crude oils by extraction with lye and subsequent acidification. These are mixtures in which alkylated cyclopentane- and cyclohexane-carboxylic acids predominate ("Erdollexikon", Dr. Alfred Hiithig, Verlag Heidelberg, page 192).

Examples of such usable betaines can be shown by formula I:

1 2 in which R is the acid residue derived from the naphthenic acids, R is 3 4

an alkylene radical with 2-6 C atoms, R and R are the same or different and preferably means a lower alkyl radical, especially a linear alkyl radical with 1-4 C atoms and R 5 is an alkylene radical with preferably 1-3 C atoms.

A further example corresponds to the following structure:

Hereby, the two nitrogen atoms are constituents of a heterocyclic ring, e.g. of piperazine. R corresponds in its meaning to the residue R or R in formula I. The residues R and R have the above meaning. It is clear to those skilled in the art that an additional carboxyl group, possibly separated from the nitrogen by an alkylene group, can be introduced to the tertiary nitrogen atom under quaternization conditions.

Corresponding sulfobetaines have been shown to be even more effective than the above-mentioned carboxybetaines. The method for producing such sulfobetaines is described in DE-OS 27 36 408. The sulfobetaines thereby correspond to the general formula:

in which

R"*" means the naphenoyl residue,

R 2 means an alkylene residue with 2-6 carbon atoms,

R3 and

R 4 are the same or different and mean linear alkyl residues with 1-4 carbon atoms,

R<5>means an alkylene residue with 1-4 carbon atoms,

x has the value 1 or 0, since when x means 0, the quaternary nitrogen atom is over a further group R 2 during ring formation connected to the first nitrogen atom and in this case R 2 is an alkylene group with 2 carbon atoms. In the course of the further investigation of naphthenic acid derivatives for the purpose of tertiary crude oil transport, it has been shown that also corresponding amine oxides containing a naphthenoyl residue are extremely effective compounds. Already in very small concentrations, they lower the interfacial tension between crude oil and water.

In a method which does not yet belong to the state of the art, the preparation of amine oxides with the general formula is described:

while

R"<1>"means the naphthenoyl residue,

R means an alkylene residue with 2-5 carbon atoms,

R 7 , R 8 are the same or different and mean a methyl or ethyl residue

as well as their application for the tertiary petroleum transport.

It is known to those skilled in the art that the influence of the oil/water interface reaches its maximum when the affinity of the surface-active compound exists in a balanced ratio to the oily and to the aqueous phase. If the compound is too hydrophilic, it concentrates particularly in the aqueous phase, and if it is too hydrophobic, it dissolves particularly in the oil phase. This hydrophobic/hydrophilic resp. hydrophilic/lipophilic balance can be expressed by the known HLB value.

In the case of the above-mentioned carboxy or sulfobetaines

and amine oxides on a naphthenic acid basis, for controlling the degree of hydrophobicity, professionals have the opportunity to use naphthenic acids of different molecular weight, since it can be assumed that naphthenic acids with a higher molecular weight and lower acid number are more hydrophobic than naphthenic acids with a low molecular weight and higher acid number. The influence of the hydrophobicity resp. the oleophilicity over the naphthenoyl residue in the above compound is only possible within these limits.

The invention is now based on that task

to provide surfactants or Surfactant combinations based on naphthenic acid whose hydrophilic/hydrophobic balance can be adjusted better on the soil oil present at the storage site during the synthesis of the storage site water.

According to the invention, success is achieved by using a mixture of

a) surface-active betaines which, as a hydrophilic residue, have at least one quaternary ammonium group which is intramolecular

capable of salt formation with a carboxyl group or sulfonic acid group, and as an oleophilic residue has at least one residue derived from the naphthenic acids or from amine oxides with the general formula

while

R"1" means the naphenoyl residue,

R g means an alkylene residue with 2-5 carbon atoms,

R 7 , R 8 are the same or different and mean a methyl or ethyl residue,

and

b) polyoxyethylene esters of naphthenic acids with a molecular weight of the ester of 500 - 3000 in a weight ratio a) : b) = 10 : 90 to 90 : 10 as surfactants for the tertiary crude oil transport.

In the combination of non-ionic naphthenic acid polyglycol esters with amphotensides or naphthenic acid-based amioxides, the cloud point is shifted very strongly in the direction of higher temperatures, with at the same time significantly improved insensitivity of the surfactant solutions in relation to high salt concentrations.

This is significant for the use of such products within the framework of tertiary precautions for crude oil transport, especially for the method of crude oil mobilization by setting extremely low interface tensions (low tension flooding).

The previously given frequently varying storage location conditions (temperature, pressure, salinity of the storage location water, crude oil composition, porosity and capillarity of the rock formation, mineralogical nature of the storage location rock and many other factors) make it necessary in practice to be able to control the surfactant properties.

Extremely low interfacial tensions between crude oil/storage water are only achieved if the surfactant used can be adapted to the HLB configuration corresponding to the system. Thereby, a specific HLB setting corresponds to a fixed ratio of the solubility of the surfactant in the aqueous and in the oil phase. This presupposes, to a certain extent, constant conditions of the tensiop solubility depending on the temperature and the salinity of the storage water.

It is thus a particular advantage of the object of the invention that it is possible to set the equilibrium with regard to the hydrophobicity and hydrofoil of the components in several ways. Thus, on the one hand, you can use esters of naphthenic acids whose polyoxyethylene residue is of different size. With increasing content of oxyethylene groups, the water solubility and the cloud point of the mixtures in the salt solutions increase. On the other hand, you can vary the ratio between betaine or : amine oxides and non-ionic compounds within wide limits. In this way, it is possible to obtain mixtures of surface-active compounds based on naphthenic acid whose cloud point in the possible storage site water is above the prevailing temperature in the storage site. This makes it possible to set the HLB range in which optimal interfacial active properties are to be expected.

According to the invention, polyoxyethylene esters of naphthenic acids have a molecular weight of 500 - 3000. The compounds with a molecular weight of up to approx. 1000 is solubilized with the aid of the co-used betaine resp. amine oxides in the storage water so that they dissolve in the concentrated salt water. Depending on the temperature of the storage location, the degree of oxyethylation is chosen, as the rule applies that with increasing temperature of the storage location, the degree of oxyethylation must increase in order to

achieve the desired point of blur. As the conditions are different from storage location to storage location, it is inevitable from the possible storage location to take a sample of the storage location water and measure the cloudiness point of different mixtures within the area according to the invention in order to find the mixture that has a completely optimal cloudiness point, i.e. usually a cloud point not above the storage temperature. Such an indicative measurement can take place according to the spinning-drop method. Thereby no deformities are observed or the emulsification or solubilization of a rotating oil droplet in salt water.

The polyoxyethylene esters of the naphthenic acids may have a small content of oxypropylene groups. As this, however, lowers the hydrophilicity of the polyoxyalkylene residue, the content must be low, especially below 10 mol%.

Crude oil

A crude oil with the following data is used for the experiments:

Storage site water

The experiments were carried out with different salt water. Water 1 is a synthetic storage site water corresponding to DIN 50 900:

Water 2 is a synthetic reservoir water with the following data:

Surfactants based on naphthenic acid

The following compounds are used as naphthenic acid-based surfactants:

Polyoxyethylene naphthenic acid ester

Carboxybetaines

A^The molecular weight of naphthenic acid is 268

A2The molecular weight of naphthenic acid is 425

Sulfobetaines

Molar weight of naphthenic acid 368 Amino oxides

The molecular weight of naphthenic acid is 268

Cloud point (separation point) in polyoxyethylene naphthenic acid esters in distilled water and various salt waters, active substance content 1000 ppm.

The cloud point (separation point) of naphthenic acid carboxybetaines and polyoxyethylene naphthenic acid esters in distilled water and various salt waters, active substance content 1000 ppm.

The cloud point (separation point) of naphthenic acid carboxybetaines and polyoxyethylene naphthenic acid esters in various salt waters, active substance content 1000 ppm

The cloud point (separation point) of naphthenic acid sulfobetaines and polyoxyethylene naphthenic acid esters in salt water according to DIN 50 900 (water 1). Active substance content 1000 ppm.

The cloud point (separation point) of naphthenic acid amide amine oxide and polyoxyethylene naphthenic acid ester in various salt waters. Active substance content 1000 ppm.

Interfacial tension values in mN 2 as a function of temperature (measured with the spinning-drop method)

Interface: Crude oil/water 1.

Surfactant concentration: 1000 ppm

The measurement results show that, as expected, the separation temperature of the aqueous solutions of naphthenic acid polyglycol esters when adding naphthenic acid carboxy- or naphthenic acid sulphobentains and naphthenic acid amino oxides is not shifted linearly in the direction of higher temperatures. Associated with this is, in all cases, a significant increase in the stability of the surfactant solutions against pilling. Both effects are important prerequisites for practice.

The examples clarify with the help of the spinning-drop measurement results the importance of optimal HLB setting when achieving extreme interfacial tension values. For long-term surfactant action in the area of special system properties, a constancy of the material distribution of the active substances between oil and water phase is a basis.

Therefore, under the many possibilities of the formulation of the surfactant composition, they enjoy the advantage if the separation temperature is at or just above the field temperature (working temperature).

Whether a system of crude oil/storage water plus surfactant gives one or more areas of extreme interfacial tension depends not only on the general system properties, but also on the structure of the surfactant active ingredients, their absolute concentration, the HLB setting and finally the material phase distribution.

Thus, the example with the surfactant combination A^/IV shows that the spinning-drop values for the mixing ratio 0/100 and 10/90 first occur at a temperature of 60°C, i.e. above the separation temperature in the range 10 — 2 10 —3 mN<2>An iact- examination of the system has shown that there is the formation of new phases which can sometimes be regarded as liquid crystals.

Whether the spinning-drop method here is still able to give absolute interfacial tension values must remain unsettled.

However, the same surfactant combination A^/IV, now in a mixture ratio of 25/75 and 27/73, also gives interfacial tension minima at <60°C, which is below the separation temperature.

Similar phenomena occur in the examples with the surfactant combinations B/IV and C/V. In both cases, two minimum regions exist, one time below and one time above the separation temperature of the respective surfactant solution. Clearly visible during the measurement is the difference in phase relationships.

Claims (1)

Application of a mixture ava) surface-active betaines which as a hydrophilic residue have at least one quaternary ammonium group which is intramolecularly capable of salt formation with a carboxyl group or sulfonic acid group and which have as an olephilic residue at least one from . the naphthenic acid derived residue or from amino acids of the general formula where R"1" means the naphenoyl residue, R means an alkylene residue with 2-5 carbon atoms, 7 8 R , R are the same or different and mean a methyl- or ethyl residue, and b) polyoxyethylene esters of naphthenic acids with a molar weight of the ester of 500 - 3000 in the weight ratio a) : b) = 10 : 90 to 90 : 10 as surfactants for the tertiary petroleum transport.