DE2210431C3 - Blends of crude oil - Google Patents

Description

The invention relates to blends of crude oils having improved flow properties, particularly at low levels Temperatures.

Depending on the particular oil production field, crude oils can contain significant amounts of wax. This wax gradually separates out of the oil when it cools below a certain temperature. Due to the cohesion of the wax crystals separated in three-dimensional structures, the oil becomes a imparted a certain degree of solidification. If the temperature is sufficiently low, the oil can dissolve even solidify completely. As explained below, the presence of crystallized wax in the Crude oil has an adverse effect on the flow properties and manageability of the oil.

Crude oil is extracted from a borehole that passes through layers with lower temperatures than those of the oil Leads containing formation, the oil coming into contact with the cold wall of the bore can settle solidify, which hinders the transport to the surface. If the funding is temporarily interrupted, can fto even completely solidify the oil, which is the case with the Resumption of production leads to serious problems.

When storing the oil? In tanks that are not provided with heating or insulation ^(l 5, the oil in contact with the cold walls and bottom of the tank cools down and can solidify as a result. This leads to difficulties in Herai.ispi. mpcn of the oil from the tank; it

This can result in significant amounts of solidified oil remain in the tank, reducing the effective capacity of the tank.

This problem arises when transporting waxy crude oil in unheated tankers which the walls of the chambers partly differ from those in direct contact with the cold sea water standing hulls are formed, even greater importance. Stay when the tanker is unloaded large amounts of solidified oil back and reduce the ship's carrying capacity; in addition the cargoes carried after the crude oil can become contaminated.

The poor flow properties of the oil at lower temperatures can also affect either by pumps or by the prevailing pressure or by level differences taking place transport of the oil through pipelines.

When pumping waxy crude oils through a pipeline, they can! Build up high flow resistances, which require a very high pumping force. This can lead to high transport costs, especially in the case of pipelines, that lead over long distances. If the resistance is very high, the existing delivery pressure the pump or the permissible pressure determined by the thickness of the tube are no longer sufficient, so that the oil can no longer be pumped.

If the pumping is interrupted while there is waxy crude oil in the pipeline, it cools down oil, which is often warmer than its surroundings. The wax deposited during cooling can create unhindered spatial structures that extend over the entire cross-section of the pipeline and which require very high pumping pressures to reduce them. If this pressure exceeds the available stationary or permissible delivery pressure, the transport cannot be resumed.

Both when a waxy crude oil is pumped through a pipeline and when it is in the If the pipeline is standing, the oil can solidify on the cold pipe wall and leave a residue Make deposit. This reduces the capacity of the pipeline and has the risk of contaminating the pipeline following batches of crude oil to be pumped through the pipeline.

When refining crude oil make certain processes, such as the separation of water or Sediment, e.g. B. by settling, centrifugation, filtration or coalescence, a thin oil is required. If, because of the presence of crystallized wax, the oil is not sufficiently flowable, it will pass There is a possibility that these procedures will not be carried out at all or only to a limited extent can.

Good flow properties of a crude oil are not only important for transport and storage, but also desirable for many other reasons. In this regard, z. B. the sampling, the transmission of Pressure signals through narrow pipes and the proper functioning of the in refineries and along the Pipelines for various purposes, such as B. Temperature and density measurements, attached automatic Registration devices are called.

From the above it can be seen that the flow properties of a crude oil both during the Production and storage as well as transport and refining of the oil play a major role. It is It is therefore extremely important that the effects of counteracting the good flow properties of the oil Keep wax as small as possible.

In order to be able to predict the flow behavior of a crude oil under operating conditions, often Laboratory measurements made of a property considered characteristic of the flow behavior of oil can be viewed, namely the pour point.

The pour point is used as the criterion of the lowest, during storage or transport or

ίο during a possible interruption in transport permissible temperature. Compounds are known to be characterized by their presence in a crude oil lower the pour point of this oil, z. B. Polymers with aliphatic hydrocarbon side chains with at least 14 carbon atoms, which are optionally olefinically unsaturated by polymerization Connections have been obtained. As examples of this type of polymer, polyalkyl acrylates can be used to be named. From DE-OS 18 11577 is a

Known additive that contains ethylene as a building block and this building block with a comonomer that is either from a heterocyclic compound descends or z. B. alkyl acrylate or butyl acrylate is, combined This additive always contains considerable amounts of ethylene, e.g. B. 82 to 99 Mole percent L.

The pour point is determined according to a standard method, with the oil at a rate of about 0.5 ° C / min (= 30 ° C / h) is cooled. In the Practice, such as B. when transporting the pipeline or when the pipeline is shut down, you sometimes have to deal with it to do significantly lower cooling rates, e.g. B. with cooling rates of 5 ° C / h or even less than 3 ° C per day. It was found,

.15 that in this case the abovementioned compounds generally do not have the desired beneficial effect exercise the solidification temperature of the crude oil at which it can no longer be easily transported. Has the oil solidifies once, e.g. B. in a pipeline, must

a very high one to restore the oil flow Pressure is exerted, which is often not provided by the pumps installed in the pipeline can be. In addition, the viscosity of the crude oil must be reduced to one quickly after recycle acceptable value decrease, which is not always the case.

A connection type has now been found that corresponds to

Admixture to a waxy crude oil this solidification temperature not only at high, but reduced even at lower cooling rates.

Accordingly, the invention relates to a crude oil mixture consisting of a wax-containing crude oil and 0.001 to 2.0 percent by weight of a polymeric pour point depressant, the heterocyclic rings as building blocks of the Has polymer chain, which is characterized in that in the polymer in the polymer chain also aliphatic side chains with at least 10 carbon atoms are present, the ratio of The number of side chains to the number of heterocyclic rings is in the range from 1: 5 to 20: 1.

The polymer consists of a main chain made up of carbon atoms, the heterocyclic rings and carries long hydrocarbon side chains. The term used in the present description

(><,"Heterocyclicring" denotes all types of radicals with a heterocyclic ring system.

The polymers present in the crude oil mixture according to the invention, in which the long Kohienwas-

the hydrogen side chains are unbranched and saturated, d. H. Polymers in which the long hydrocarbon side chains by the formula

CH ₃ - (CH ₂ J _n -CH ₂ ■

where n> 8, can be represented, are preferably polymers with long hydrocarbon side chains used, in which the number of to carbon atoms 14 to 30 and in particular 16 to 26 amounts to

The polymers that can be used to lower the pour point according to the invention, consist of a main chain made up of carbon atoms with long hydrocarbon side chains. Part or all of those in a heterocyclic ring carbon atoms present can form part of the main chain, but generally carries the Main chain the heterocyclic rings. The long hydrocarbon side chains and / or the heterocyclic ones Rings can be linked either directly or indirectly to the main chain. In the former In this case there are no more atoms between the first carbon atom of the long hydrocarbon 2s side chain and / or the heterocyclic ring system present in the heterocyclic ring and the Carbon atom of the main chain to which the side chain is attached or the heterocyclic ring is bonded. Are the long hydrocarbon side chain and / or the heterocyclic one Ring indirectly bound to the main chain, there are one or more atoms, such as. B. Carbon, oxygen, sulfur, nitrogen or phosphorus atoms, between the first carbon atom the long hydrocarbon side chain and / or des .is heterocyclic ring system and the carbon atom of the main chain to which the side chain and / or the heterocyclic ring are bonded. Polymers with long hydrocarbon side chains are preferred used, which are indirectly linked to the main chain via one or more oxygen and / or carbon atoms are bound. Some examples of polymers in which the aliphatic hydrocarbon side chains are indirectly linked to the main chain via one or more oxygen and / or carbon atoms, are polymers with aliphatic hydrocarbon side chains that have a carboxyl group or a Oxygen atom are bound to the main chain. The heterocyclic ring is preferably directly attached to the Main chain tied.

The long hydrocarbon side chains bound to the polymer main chain have a hitherto unexplained effect Way together with the heterocyclic rings that a special effect regarding the lowering of the pour point is achieved especially at low cooling speeds (see Tables A and B, in which, for comparison, a copolymer of stearyl acrylate, Eicosyl acrylate and docosyl acrylate and, among others, an unspecified commercial agent were applied).

The production of such polymers can basically be carried out in two ways. First these polymers can be prepared by copolymerizing olefinically unsaturated compounds those, of which at least a part consists of olefinically unsaturated compounds, in addition to a polymerizable> C = C <group carry a long hydrocarbon chain, and at least a part from compounds which, in addition to a polymerizable> C = C <group, form a heterocyclic ring system wear. A second way in which these polymers can be made is by copolymerization olefinically unsaturated compounds without a long hydrocarbon chain and / or heterocyclic ring system and a subsequent treatment of the polymer, through which the long Hydrocarbon chain and / or the heterocyclic ring are introduced into the polymer.

Of course, polymers with different types of long hydrocarbon side chains (e.g. with different numbers of carbon atoms) and / or different heterocyclic rings are used will.

The molecular weight of the inventive improvement of the flow properties. Polymers that can be used for oil mixtures can vary within wide limits. For practical use, polymers with an average molecular weight (number average Ai _n ) between 1000 and 1,000,000 and in particular between 4,000 and 100,000 are preferably chosen.

Depending on the particular type of paraffin waxes present in the crude oil, this According to the invention, crude oil mixture are preferably admixed with polymers in which the in each Long hydrocarbon side chains present in each molecule by a number of carbon atoms differ.

The heteroatoms in the heterocyclic rings are in particular sulfur, oxygen or Phosphorus atoms. An example of a compound suitable for incorporation into the polymer is sulfolene. Preferably are heterocyclic ring systems with a nitrogen atom, such as. B. piperidine or pyrrolidone, and in particular aromatic heterocyclic ring systems, such as. B. quinoline, isoquinoline and especially pyridine, used. It is also possible to use heterocyclic ring systems with two or more heteroatoms will.

The polymers are preferably prepared by radical copolymerization.

Examples of compounds with a pyridine ring and an olefinic double bond, which are good for Suitable for the preparation of polymers according to the invention are 2-methyl-5-vinylpyridine and, in particular, 4-vinylpyridine.

Examples of olefinically unsaturated compounds with long hydrocarbon chains, which can be used for production Of the polymers present in the crude oil mixture according to the invention, vinyl esters and allyl esters are suitable saturated monocarboxylic acids, such as. B. vinyl and allyl esters of arachidic and behenic acid; Alkyl esters unsaturated monocarboxylic acids, such as. B. alkyl esters of methacrylic acid and especially the alkyl esters Acrylic acid; Alkylamides of unsaturated monocarboxylic acids, such as. B. n-eicosyl acrylamide and n-docosyl methacrylamide; Dialkyl esters of unsaturated dicarboxylic acids, such as. B. di-n-octadecyl maleate and di-n-docosyl fumarate; Dialkylamides of unsaturated dicarboxylic acids, such as. B. Di-n-eicosylmaleindiamid and Di-n-docosylfumardia..iid; Imides of unsaturated dicarboxylic acids, such as. B. n-Octadecyl maleic acid imide and n-eicosyl maleic acid imide: Alkyl vinyl ethers such as n-docosyl vinyl ether and n-tetracosyl vinyl ether, and monoolefins such as. B. 1-octacoses and 1-docoses.

If desired, olefinically unsaturated compounds without long hydrocarbon chains can be used in the polymers are incorporated, e.g. B. vinyl esters of unsaturated monocarboxylic acids, such as. B. vinyl acetate, Alkyl esters of unsaturated mono- and dicarboxylic acids, such as. B. methacrylate and diethyl maleate, alkyl vinyl ether, such as B. octyl vinyl ether, and monoolefins, such as. B. Athens and isobutene.

The ratio between the in the in the invention The number of long hydrocarbon side chains present in the polymers contained in the crude oil mixture the number of heterocyclic rings can vary within wide limits, e.g. B. between 1: 5 and 20: 1. A ratio of between I: 1 and 10: 1 is particularly suitable.

Copolymers of 4-vinylpyridine are particularly suitable and alkyl esters of unsaturated carboxylic acids, e.g. B. alkyl esters of unsaturated monocarboxylic acids, such as methacrylates and especially alkyl acrylates.

The concentration in which the polymers can be used in waxy crude oils vary within wide limits, depending on the nature, structure and molecular weight of the to be used polymers, the type and amount of paraffin wax present in the crude oil and the intended improvement of the flow properties. In some cases a lot is enough of 0.001 percent by weight, based on the crude oil mixture, in order to achieve the desired improvement in To achieve flow properties. In most cases an amount of 2.0 weight percent is perfect sufficient. Preferably, from 0.002 percent by weight to 0.2 percent by weight of the crude oil Mixed with polymers.

The wax-containing crude oil mixture according to the invention, to which the polymers are added, can consist of one waxy crude oil or a mixture of waxy crude oils. If desired, the Polymers can also be mixed into mixtures that consist of one or more wax-containing crude oils and consist of one or more non-waxy crude oils.

The present polymers, in particular as additives for facilitating the transportation of waxy Crude oils through pipelines, by tankers or

ίο other means of transport are important are also particularly suitable for use in oil wells producing waxy crude oil for this purpose Way to prevent the formation of wax deposits or to avoid such wax deposits on the

Dissolve ι s walls of the hole.

For the production of crude oil mixtures according to the invention, the polymers can expediently the waxy crude oil as such or in the form of a concentrate, e.g. B. in a hydrocarbon solvent, that is a single hydrocarbon, such as. B. toluene, or a mixture of hydrocarbons, e.g. B. a crude oil or a crude oil fraction can be added. Concentrations from 2 to 50 percent by weight of the polymer in the solvent are very suitable.

2s When a polymer is a waxy crude oil promotional bore must be added, it is particularly useful to use the polymer (z. B. in a Solution) into the waxy crude oil present in the bore, especially in the lower part of the Bore, e.g. B. with the help of a macaroni tube. It is also possible to use the polymer as a concentrate in To lead down the annulus at intervals, the production of a well is temporarily interrupted a solution of the polymer prior to resumption of oil production from the well into the oil-containing formation to be printed.

example 1

Two copolymers of alkyl acrylates and 4-vinyl pyridine were made. In the starting mixture for For the preparation of polymer A, the alkyl acrylates consisted of a mixture of eicosyl and docosyl acrylates with an average alkyl side chain length of 21 carbon atoms. The polymerization was carried out by radical copolymerization with programmed addition of 4-vinylpyridine until 70 Percent of the alkyl acrylates had been polymerized. The ratio of alkyl acrylates to 4-vinylpyridine im Copolymer A was 1: 0.3. The average molecular weight was 40,000.

The polymer B was obtained by polymerizing a mixture of 4-vinylpyridine, eicosyl acrylate and Oocosyacrylate produced (average length of the alkyl side chain of the alkyl acrylates 21.5 carbon atoms), up to 10 percent by weight of the monomers had been converted into the polymer. The ratio of Alkyl acrylates to 4-vinylpyridine in polymer B was 1:03, the average molecular weight 40,000.

For comparison, a copolymer C of stearyl acrylate, eicosyl acrylate and docosyl acrylate was used (average length of side chain 20 carbon atoms) with an average molecular weight manufactured by 60,000.

A North African waxy crude oil that had been stored at room temperature for several weeks was heated to a certain temperature (rewarming temperature). The polymer was admixed with the doping temperature, which was lower in two cases equal to the reheating temperature and in one case at 10 ⁰ C when the reheating temperature in an amount of 400TpM. The pour points were determined using two cooling rates. In the first series of tests, the cooling rate described in ASTM D 97-66 was used, namely a cooling rate of about 0.5 ° C./min (= 30 ° C./h). In the second series of tests, the cooling rate was reduced to 5 ° C./h and the last temperature at which the oil just showed a flow (as described in the ASTM D 97-66 method) was taken as the pour point. Table A shows that the effect of Polymers A and B on the pour point when cooled relatively quickly was equal to or superior to the effect of Polymer C and that of a commercial pour point depressant D. With slow cooling (second trial

f> 5 he) was that with polymers A according to the invention and B, the lowering of the pour point obtained is considerably greater than that of the polymers C and D.

809 611/107

10

label A

example waxy crude oil + 400 ppm C Correctional temperature (C) 50 40 JRlIlIl ((I 40 the same comparison 50 mp + 400 ppm I) DoliuiiingstL 40 24 the same comparison 50 9 + 400 ppm Λ l'ourpoint ( 24 the same + 400 ppm B 24 12th 15th the same 21 waxy crude oil + 400 ppm C 24 12th A b cool wind speed the same comparison 21 12th 30 CVh + 400 1 pM D 12th 24 the same comparison 12th 12th 21 + 400 ppm A 12th 24 the same + 400 ppm B 24 24 12th the same , o Belle B shows the 24 2 21 <-3 Cooling rate 21 6th 5 CVh 0 to see that d 0 6th 6th is Results; it

In this example, the pumping of a crude oil through a pipeline was simulated. The flow of the oil through the pipeline was simulated by slow movement (stirring) while cooling, and the pumping process by occasionally pressing it through a nozzle. A standstill of the oil in the pipeline, as can occur in the event of a fault, was simulated by cooling the stagnant crude oil in a queue.

A container was filled at about 3O ⁰ C with a crude oil and stirred slowly under cooling at a Abkühlungsge speed of 3 ° C per day. The contents of the container was pressed at a temperature of 30 ⁰ C, 15 ° C, 13.5 ° C or 12.5 ° C through a 2 cm long nozzle having a diameter of 0.5 mm After reaching a temperature of 11 , 5 ° C, a 1 to 6 m long line having a diameter of 6 mm filled with oil from the container This snake, in which the found oil in the resting state, was subsequently at a rate / on 3 ° C per day up to a temperature of 9 ° C. Then, by exerting increasing pressure (a pressure increase of 1 N / m ² per quarter hour) on the contents of the snake, the pressure was determined which was necessary to restart the oil flow in the snake. After wave formation had just started in the crude oil in the snake, the pressure was increased to 8 N / m ² and the viscosity of the contents of the snake was determined after 50 and 100 seconds

The following crude oils were used in three successive experiments: A North African waxy crude oil with an added copolymer of alkyl acrylate (average number * of carbon atoms in the alkyl chain 19.5) and 4-vinylpyridine (ratio in the copolymer 2: 1; polymer E), and Once again the same oil with the added commercial pour point depressant D. Ta can be set in motion much more easily than the crude oil with additives C and D. Since the pumps used in the pipelines in operation today are not able to transport over long distances To achieve a pressure of more than 8 N / m ² , only a crude oil with the polymer E can be conveyed through these pipelines, while the restoration of a crude oil that has stood still for some time at 90 ° C in the case of waxy crude oils with the additives C and D is extraordinary difficult, if not impossible.

Table B. comparison C. D. Polymer H 400 400 200 7.5 > 20 Concentration (tpm) 1.5 Flow resistance at 9 C - (N / m ² ) *) <1 850 Viscosity after 50 s after 100 s

*) N = Newton (IN = 0.101972 Kp).

Example 3

A copolymer of alkyl acrylate (average number of carbon atoms in the alkyl chain 19) and 4-vinylpyridine (molar ratio of alkyl acrylate to 4-vinylpyridine 3.3: 1; molecular weight 60,000) was prepared (polymer F). The polymers C, E and F were dissolved in three types of waxy crude oils and the solidification points were determined by cooling at a rate of 3 ° C. per day

to simulate shear stresses occurring during the flow of the crude oil through a pump the crude oil mixtures after cooling to 21 ° C and 18 ° C through a nozzle with a length of 17 mm and a Pressed diameter of 1.2 mm. In a number of cases the flow through this nozzle was at 15 ° C

repeated. Table C shows the results. It can be seen that the polymers E and F (according to the invention Polymers) lead to crude oil blends that have a lower solidification point after shear stress than crude oil blends with the not polymers according to the invention C.

I abclle C Type of waxy crude oil 21 21 nigeri: inish 21 6th 21 north african 21 21 north african 18th 18th 22nd 18th <-12 <-12 18th 30th 18th 18th 30th 15th <-12 <-12 15th - 15th Doping temperature, C - <-12 9 Shear stress at C - - 6th 9 <-12 0 0 12th 6th <-12 21 0 6th polymer 18th 18th - 9 -3 12th 12th none (1 -6 E. 3 -9 F. 9 C (comparison)

Claims (17)

Palent claims: 1. Crude oil mixture, consisting of a waxy crude oil and 0.001 to 2.0 percent by weight of one polymer pour point depressant, which has heterocyclic rings as building blocks of the polymer chain, characterized in that in the polymer in the polymer chain also aliphatic Side chains with at least 10 carbon atoms are present, the ratio of the number of Side chains to the number of heterocyclic rings is in the range from 1: 5 to 20: 1 2. crude oil mixture according to claim 1, characterized in that the polymer by Copolyrne- i.s ization of olefinically unsaturated compounds has been obtained. 3. crude oil mixture according to claim 1 and 2, characterized in that the aliphatic hydrocarbon side chains with at least 10 carbon atoms in the polymers used are unbranched and saturated. 4. crude oil mixture according to claim 1 to 3, characterized in that the polymers are aliphatic Contain hydrocarbon side chains with 14 to 30 carbon atoms. 5. crude oil mixture according to claim 4, characterized in that the polymers are aliphatic Contain hydrocarbon side chains with 16 to 26 carbon atoms. 6. crude oil mixture according to claim 1 to 5, characterized in that the polymer consists of a Main chain consists of carbon atoms and that this main chain is aliphatic Hydrocarbon side chains of at least 10 carbon atoms and the heterocyclic rings wearing. 7. crude oil mixture according to claim 6, characterized in that the aliphatic polymers Hydrocarbon side chains indirectly via 4 "one or more oxygen and / or carbon atoms are tied to the main chain. 8. crude oil mixture according to claim 6 or 7, characterized characterized in that in the case of the polymers, the heterocyclic ring is directly attached to the main chain is bound. 9. crude oil mixture according to claim 1 to 8, characterized in that the average molecular weight of the polymer in the range from 1000 up to 1 COO 000 and in particular from 4000 up to 100,000 lies. 10. crude oil mixture according to claim 1 to 9, characterized in that the chain length of the polymers of the aliphatic hydrocarbon side chains present in each molecule with at least 10 carbon atoms differed by a few carbon atoms. 11. crude oil mixture according to claim 1 to 10, characterized characterized in that the heterocyclic rings present in the polymers have a nitrogen atom contain. 12. Crude oil mixture according to claim 11, characterized characterized in that the heterocyclic ring present in the polymers is a pyridine ring. 13. crude oil mixture according to claim 1 to 12, characterized in that the polymer by radical copolymerization has been received. 14. crude oil mixture according to claim 1 to 13, characterized in that 4-vinylpyridine for the production of the copolymer has been used. 15. Crude oil mixture according to claim 1 to 14, characterized characterized in that an alkyl ester of acrylic acid has been used to prepare the copolymer is. 16. Crude oil mixture according to claim 1 to 15, characterized in that the ratio between the number of aliphatic hydrocarbon side chains with at least 10 carbon atoms to the number of heterocyclic rings present in the polymers is 1: 1 to 10: 1 . 17. Crude oil mixture according to claim 1 to 16, characterized characterized in that the polymer is a copolymer of 4-vinyl pyridine and alkyl acrylates.