EP0175879A2 - Transportation of viscous crude oils - Google Patents

Abstract

The invention relates to a process for the transport of viscous crude oils, an oil-in-water emulsion containing emulsifier being transported with at least 10 to 15% water and then being separated again into crude oil and water. A carboxymethylated oxethylate of the formula R- (O-CH2-CH2) nO-CH2-COOM is used as emulsifier, in which R is a linear or branched aliphatic radical having 6 to 20 carbon atoms, an alkyl- or dialkylaromatic radical having 5 to 16 carbon atoms per alkyl group, n is 1 to 40 and M is an alkali or alkaline earth metal ion or ammonium.

Description

Heavy oils are difficult to transport in pipelines under conditions of usual outside temperatures due to their very high viscosity. In order to increase their mobility, they are therefore often ohölen with _low-R or mixed refinery sections; such a procedure requires relatively high additives in order to achieve a noticeable improvement in flow. In addition, such a process is only possible where light oil fields exist at the same location or where a nearby refinery can supply low-viscosity gasoline fractions.

Another method also used is to add heat to the heavy oil in order to lower its viscosity and accordingly improve its fluidity, which requires considerable amounts of heat. So it is z. B. necessary, a heavy oil of 10.3 ° API, its viscosity at 20 ° C 40 000 mPa. s is to heat to a temperature of approx. 95 C in order to achieve a viscosity of approx. 100 mPa. s to achieve a threshold value frequently required for oil transportation in pipelines (ML Chirinos et al, Rev. Tec. Intevep 3 (2), 103 (1983). This means an extreme cost for the equipment and the supply of the pipelines and a loss from 15 to 20% of crude oil, since the necessary amount of heat is usually obtained by burning crude oil.

Another method of heavy oil transport consists in pumping the oil through the pipes in the form of a more or less easily liquid emulsion. Since the viscosity of emulsions is largely determined by that of the dispersing agent, this is an oil-in-water emulsion. The oil-in-water Emulsion is obtained by adding water and emulsifier to the oil using shear forces and then pumping this mixture into the pipeline. In a settling tank, e.g. B. prior to entering the refinery, the emulsion is again separated into oil and water and the separated oil, the _R Affinerie supplied. The lowest possible concentration of the emulsifier should lead to a stable, slightly liquid oil-in-water emulsion with a very high oil content, which naturally places high demands on the emulsifiers to be used. High shear forces must also be avoided during emulsification, since there is a risk of inversion to a water-in-oil emulsion that is extremely highly viscous in heavy oils. The emulsions are also said to be stable both to higher salinities such as occur in many deposit systems and to higher temperatures. Despite the stability of the emulsions as they flow through the pipeline, they should be able to be separated again without any problems. Sulfur-containing emulsifiers are undesirable if they fail to be kept in the aqueous phase during the cleavage.

The previously proposed emulsifiers do not yet meet the stated conditions sufficiently. In many cases (e.g. US Pat. Nos. 4,285,356, 4,265,264, 4,249,554) emulsions with oil contents of only 50% are mentioned, which means that half of the pipeline volume has to be dispensed with. In other cases (e.g. CA Patents 1,108,205, 1,113,529, 1,117,568 and US Pat. No. 4,246,919), the viscosity reduction achieved with the emulsifier additive is small despite the relatively low oil content. Finally, undesirable sulfur-based emulsifiers are often used.

It was therefore the task of finding emulsifiers for the emulsification of heavy oil for transporting heavy oil in pipelines which do not have the disadvantages mentioned but essentially correspond to the property catalog described above.

in der R einen linearen oder verzweigten aliphatischen Rest mit 6 bis 20 Kohlenstoffatomen, einen alkyl- oder dialkylaromatischen Rest mit 5 bis 16 Kohlenstoffatomen pro Alkylgruppe, n 1 bis 40 und M ein Alkali- oder Erdalkali-Metallion oder Ammonium bedeuten, einsetzt.This object is achieved in that carboxymethylated oxethylates of the formula are used as emulsifiers

in which R is a linear or branched aliphatic radical having 6 to 20 carbon atoms, an alkyl or dialkyl aromatic radical having 5 to 16 carbon atoms per alkyl group, n is 1 to 40 and M is an alkali metal or alkaline earth metal ion or ammonium.

mit Chloressigsäure oder einem Salz der Chloressigsäure in Gegenwart von Alkalihydroxid oder Erdalkalihydroxid her. Aber auch andere Herstellungsverfahren sind geeignet. _R bedeutet vorzugsweise einen gesättigten oder ungesättigten, geradkettigen oder verzweigten Alkylrest mit E bis 18 _C-Atomen oder einen Alkylarylrest mit 5 bis 16 C-Atomen in der Alkylgruppe oder einen Dialkylrest mit 3 bis 16 _C-Atomen pro Alkylgruppe. Als Alkohole, deren Oxethylate carboxymethyliert werden, lassen sich z. ^B. einsetzen: Hexylalkohol, Octylalkohol, 2-Ethylhexylalkohol, Nonylalkohol, Isononylalkohol, Decyl- und Undecylalkohol, Lauryl-, Tridecyl-, Myristil-, Palmityl- und Stearylalkohol, aber auch ungesättigte, wie z. B. Oleylalkohol.The carboxymethylated oxethylates according to DE-PS 24 18 444 are advantageously prepared by reacting oxethylates of the formula

with chloroacetic acid or a salt of chloroacetic acid in the presence of alkali hydroxide or alkaline earth hydroxide. However, other manufacturing processes are also suitable. _R is preferably a saturated or unsaturated, straight-chain or branched alkyl radical having E to 18 _C atoms or an alkylaryl radical having 5 to 16 C atoms in the alkyl group or a dialkyl radical having 3 to 16 _C atoms per alkyl group. As alcohols whose oxethylates are carboxymethylated, z. ^B. use: hexyl alcohol, octyl alcohol, 2-ethylhexyl alcohol, nonyl alcohol, isononyl alcohol, decyl and undecyl alcohol, lauryl, tridecyl, myristile, palmityl and stearyl alcohol, but also unsaturated, such as B. oleyl alcohol.

Commercially available mixtures of these alcohols can be expedient. As alkylphenols such. B. Insert: _P entylphenol, hexylphenol, octylphenol, nonylphenol, dodecylphenol, hexadecylphenol, and the corresponding _D ialkylphenole. Alkyl cresols and xylenols are also suitable.

kann Natrium, Kalium, Lithium, Ammonium, Calcium, Magnesium oder Wasserstoff sein.The oxethylation can be carried out in the presence of catalytic amounts of alkali metal hydroxide, but it is known that other processes are also possible. The degree of oxyethylation can assume values between 1 and 40, preferably between 3 and 20. The cation in carboxymethylated oxyethylate with the formula

can be sodium, potassium, lithium, ammonium, calcium, magnesium or hydrogen.

The emulsifiers used are predominantly anionic, so that an unproblematic cleavage of the emulsion stabilized by them can be assumed. The compounds are thermally stable and, within extremely wide limits, are compatible with salt water (US Pat. No. 4,457,373). Furthermore, by varying the hydrophobic residue and the degree of oxyethylation, they allow the emulsifier to be optimally adapted to the oil to be transported and the given salinity of the water conveyed from the deposit in most cases, which advantageously forms the aqueous phase of the emulsion to be transported.

According to their production, the carboxymethylated oxethylates can contain unreacted oxethylate. Accordingly, a degree of carboxymethylation can be defined. The formula

therefore refers to a mixture with different amounts of unreacted ethoxylate, provided that the degree of carboxymethylation between 40 and 100%, preferably between 50 and 1 ₀ 0%, is located.

Mixtures with a degree of carboxymethylation between 85 and 100% are particularly effective. Such mixtures accordingly consist of anionic and nonionic surfactant and are considered as carboxymethylated oxethylates according to the invention.

The mixtures of anionic and nonionic surfactant described or the purely anionic compounds (emulsifier) are soluble or at least easily dispersible in conventional reservoir waters.

In preliminary tests, the emulsifier to be used can be optimally adjusted to the existing heavy oil-water system according to its chemical structure.

The surfactants (emulsifiers) of a homologous series (cf.Table A) are dissolved in the water in question and mixed with the heavy oil in question and, after briefly stirring with a paddle stirrer without using high shear forces, they are tested for their emulsifying action and the stability of the emulsion is determined. This assessment of the emulsion is repeated about 24 hours later and then the viscosity is measured as a function of the shear rate, if necessary. Since heavy oil emulsions are somewhat structurally viscous, a range between 1 ₀ and 100 sec ^{1 is} selected for the shear rate, which corresponds approximately to the transport through pipelines. A surfactant is an optimal emulsifier if the amount necessary for emulsification is as small as possible.

The amount is generally from 0.01 to 0.5, in particular from 0.03 to 0.2,% by weight, based on the amount of oil, which corresponds to 100 to 5000, preferably 300 to 2000, ppm. For heavy oil liquefaction, the emulsifier is either metered in as a melt or as an aqueous solution or as a dispersion of the oil-water mixture, or else it is added to the water, which is then mixed with the oil. Water here is understood to mean either a more or less saline water that is produced together with the heavy oil, or it can be a cheaply available surface water or, finally, a mixture of both waters. Since heavy oil fields are often exploited by steam flooding, the salinity of the water produced can fluctuate somewhat, which is not critical for the claimed process.

Instead of dosing the emulsifier into the water, it can also be added to the heavy oil itself, especially since the surfactant class claimed here shows good oil solubility. It may be advantageous to use a small amount of a light hydrocarbon mixture as a solubilizer. The mixing of the three components to form the emulsion, namely oil, water and emulsifier, can take place either directly at the borehole or in or near a collection tank or at any other point in the piping system. The mixture ratio of oil to water can vary within wide limits between 10:90 and 90:10. For economic reasons, high oil contents should be aimed at, although it must be taken into account that very high oil contents usually also lead to relatively highly viscous oil / water emulsions. Depending on the system, the economic optimum is between 70 and 85% oil. As is known, the emulsification is favored by mixing devices such as agitators, centrifugal pumps, static mixers, etc., which are used when necessary. The _E multi- sion thus formed is conveyed through the pipe system, the which can contain intermediate stations and intermediate storage containers. At the pipeline end point, the emulsion is split in a separator, it being advantageous to add one or more desmulsifiers. The crude oil dewatered in this way is drawn off and then either to the refinery or a possible further transport, e.g. B. supplied by ship.

Examples

In a glass jar or polyethylene beaker with a volume of approx. 200 ml, 75 g of Boskan oil (approx. 10 ° API, viscosity at 20 ° C approx. 180 000 mPa.s) and each 25 g of the aqueous surfactant solution mentioned, which also neutral electrolyte contains, stirred at room temperature with a simple paddle stirrer (approx. 100 revolutions per minute). If the added surfactant is effective and its amount is sufficient, a uniform-looking emulsion has been created. Then the mixture is allowed to stand for about 24 hours at room temperature and re-examined the consistency of the mixture, with - if necessary - something is stirred with a _G lasstab. If a smooth, uniform emulsion has formed, the viscosity is measured, as already described. The minimum emulsifier concentration (percent by weight, based on the amount of oil) of the surfactant in question is registered, which is necessary to produce an approximately stable emulsion. "Somewhat stable" here means that even slight stirring with the glass rod is sufficient to restore the original uniformity, if it has been lost at all.

The examples summarized in the following tables demonstrate the generally high effectiveness of the carboxymethylated oxethylates as heavy oil emulsifiers.

As shown in Table A using the example of lower saline water (1,500 ppm NaCl), the effectiveness of the surfactant can be optimized by varying the chemical structure (change in the degree of EO). Carboxymethylated nonylphenol oxethylates with an EO degree of approx. 3.3 have the highest effectiveness here. The viscosity is around 100 mPa. s at 20 ° C - 100 mPa are required. s at 37.7 ° _C - very low.

Table B examines the effect of the same surfactants in the presence of high saline water (50,000 ppm NaCl). The EO grade of the most effective surfactants is between 5.5 and 6.0. The significantly increased effectiveness compared to the lower salinar conditions in Table A is surprising

As shown in Table C compared to Table B, the degree of EO of the most effective carboxymethylated oxethylates changes when the nonylphenol residue is replaced by dodecylphenol.

As Table D demonstrates in comparison to Table A, the substitution of the cation (hydrogen instead of sodium) also has a strong influence on the emulsifying properties of the surfactant, the structural variable here again being the EO degree. For the optimal surfactant, it is much higher here, although the reduction in the salinity of the aqueous phase should actually also result in a reduction in the degree of EO.

Table E shows the dependence of the emulsifying activity in the case of a carboxymethylated nonylphenol oxethylate on the degree of carboxymethylation. The influence of alkaline earth ions is also examined. The effectiveness increases with increasing degree of carboxymethylation. This also applies in the presence of alkaline earth metal ions, which otherwise have a high emulsifying effect Reduce basic salinity more than additional alkali halides in the same concentration.

Since heavy oil is often extracted using steam and hot water flooding, variable salinity must be expected. A corresponding series of dilutions of the salinity is shown in Table _F. It is shown that the carboxymethylated oxethylate tested here, in very low concentrations, is an effective emulsifier over a wide salinity range of 10.2 to 1.2%, which leads to highly fluid emulsions.

It is known that heavy oils differ greatly in their composition. For this reason, tests were carried out with another heavy oil in analogy to Table C. This has a density of 12 ⁰ A _P I and contains 30% aromatic, 20% napthenic and 50% paraffinic hydrocarbons. The viscosity at 20 ° C is 70,000 mPa. s, As Table G shows, light liquid oil-in-water emulsions can be prepared with small additions of carboxymethylated oxethylates. The EO degree of the carboxymethylated nonylphenols, which lead to a minimum of the necessary surfactant concentration, is considerably higher than that of the heavy oil examined in Table C.

Claims (4)

1. A method of transporting viscous crude oils through a pipeline, an oil-in-water emulsion made from crude oil and at least 10 to 15% water, which contains an emulsifier, and passed through the line and then separated again into crude oil and water becomes,
characterized,
that as the emulsifier carboxymethylated oxethylate of the formula R- (O-CH ₂ -CH ₂ ) _n -O-CH ₂ -COOM, in which R is a linear or branched aliphatic radical having 6 to 20 carbon atoms, an alkyl or dialkyl aromatic radical having 5 up to 16 carbon atoms per alkyl group, n is 1 to 40 and M is an alkali or alkaline earth metal ion or ammonium. 2. The method according to claim 1,
characterized,
that the degree of carboxymethylation of the carboxymethylated oxethylate is 50 to 100%. 3. The method according to claim 1,
characterized,
that the degree of carboxymethylation of the carboxymethylated oxethylate is 85 to 100%. 4. The method according to claims 1 to 3,
characterized,
that the emulsifier concentration, based on the amount of oil, is 0.01 to 0.5 percent by weight (100 to 5,000 ppm).