EP0905350A1 - Process for conveying hydrates dispersed in production effluents - Google Patents

Abstract

The addition of an amphiphilic non-ionic product, formed by the reaction between a polymerized unsaturated oil and an aminoalcohol enables the transport of suspended hydrates in fluids comprising water, gas and liquid hydrocarbons and inhibits agglomeration of the hydrates. The concentration of the incorporated additive is 0.1-5%, preferably 0.1-2%, relative to the water present. The fluid may comprise the hydrocarbons methane, ethane, ethylene, propane, propene and n-butane, possibly H2S and/or CO2, natural gas, petroleum gas and at least one liquid hydrocarbon. An Independent claim is also included for the preparation of the additive, by the reaction between a polymerized flax oil of viscosity (20 degrees C.) 5-60Pa.s. and diethanolamine. After the reaction, the product is conditioned in an aromatic solvent or one derived from an oil , vegetable or animal grease (preferably a methyl ester of colza oil) to give a mixture containing 20-80%, preferably 30-0%, of solvent.

Description

The invention relates to a method for transporting gas hydrates. natural, petroleum gas or other gases suspended in a fluid comprising water, one of said gases and a liquid hydrocarbon.

It relates more particularly to a process in which we bring into play a nonionic amphiphilic composition obtained by reaction at least one polymerized unsaturated vegetable oil and at least one amino alcohol.

The gases which form hydrates can in particular comprise at least one hydrocarbon chosen from methane, ethane, ethylene, propane, propene, n-butane and isobutane, and optionally H ₂ S and / or CO ₂ .

These hydrates are formed when water is in the presence of gas, i.e. in the free state, or in the dissolved state in a liquid phase, such as liquid hydrocarbon, and when the temperature reached by the mixture in particular water, gas and possibly liquid hydrocarbons, such that oil, becomes lower than the thermodynamic temperature of formation of hydrates, this temperature being given for a known gas composition and when their pressure is fixed.

Hydrate formation can be feared, especially in industry oil and gas, for which hydrate formation conditions can be brought together. Indeed, to decrease the cost of production of crude oil and gas, both in terms of investment and in terms of in terms of operation, a planned route, particularly in production in sea, is to reduce, or even eliminate, the rates applied to crude or gas to transport from the deposit to the coast and in particular to leave any or part of the water in the fluid to be transported. These treatments at sea are generally carried out on a surface platform near the deposit, so that the effluent, initially hot, can be treated before the thermodynamic hydrate formation conditions are affected by the cooling of the effluent with seawater.

However, as happens practically when the conditions thermodynamics required to form hydrates are met, the agglomeration of hydrates leads to blockage of the transport pipes by creating plugs which prevent any passage of crude oil or gas.

The formation of hydrate plugs can cause a stop of the production and thus cause significant financial losses. In addition, the return to service of the installation, especially in the case of production or transport at sea, can be long, because the decomposition of hydrates trained is very difficult to achieve. When the production of a submarine deposit of natural gas or oil and gas comprising the water reaches the surface of the sea floor and is then transported to the bottom of the sea, it happens, by lowering the temperature of the effluent produced, that the thermodynamic conditions are met for hydrates to form form, agglomerate and block the transfer lines. The temperature at the bottom of the sea can be, for example, 3 or 4 ° C.

Favorable conditions for the formation of hydrates can also be similarly assembled on the ground, for pipes not (or not enough deeply) buried in the earth, when for example the ambient air temperature is cold.

To avoid these drawbacks, attempts have been made in the prior art to use products which, added to the fluid, could act as inhibitors in lowering the thermodynamic temperature of hydrate formation. This are in particular alcohols, such as methanol, or glycols, such as mono-, di- or triethylene glycol. This solution is very expensive because the amount of inhibitors to add can reach 10 to 40% of the water content and these inhibitors are difficult to recover completely.

It was also recommended to insulate the transport lines, so as to prevent the temperature of the transported fluid from reaching the hydrate formation temperature under the operating conditions. A such a technique is also very expensive.

In addition, various nonionic or anionic surfactant compounds have been tested for their effect of delaying the formation of hydrates within a fluid containing a gas, in particular a hydrocarbon, and water. We may for example cite the article by Kuliev et al: “Surfactants Studied as Hydrate Formation lnhibitors. »Gazovoe Delo n ° 10 1972, 17-19, reported in Chemical Abstracts 80, 1974, 98122r.

The use of additives capable of modifying the hydrate formation mechanism, since instead of agglomerating quickly to each other and form plugs, hydrates formed disperse in the fluid without agglomerating and without obstructing the pipes. Mention may be made in this regard of patent application EP-A-323,774 on behalf of the Applicant, who describes the use of compounds nonionic amphiphiles chosen from polyol and acid esters carboxylic, substituted or unsubstituted, and the functional compounds imide; patent application EP-A-323,775, also in the name of the Applicant, which describes in particular the use of compounds belonging to the family of diethanolamides of fatty acids or fatty acid derivatives; US-A-4,856,593 which describes the use of surfactant compounds such as organic phosphonates, phosphate esters, acids phosphonic acids, their salts and esters, inorganic polyphosphates and their esters as well as polyacrylamides and polyacrylates; and the Patent application EP-A-457375, which describes the use of compounds anionic surfactants, such as alkylarylsulfonic acids and their salts of alkali metals.

Amphiphilic compounds obtained by reaction of at least one derivative succinic chosen from the group formed by acids and anhydrides polyalkenyl succinics on at least one polyethylene glycol monoether have also been proposed to reduce the tendency to agglomerate hydrates of natural gas, petroleum gas or other gases (request for EP-A-582507).

We have now discovered that to transport hydrates in suspension in a fluid comprising water, gas and a liquid hydrocarbon, it was particularly advantageous to use as additive one or more nonionic amphiphilic compositions obtained by reaction of at least one polymerized unsaturated vegetable oil, with at minus one amino alcohol.

Thus, the invention provides a method for transporting hydrates in suspension in a fluid comprising at least water, a gas and a liquid hydrocarbon under conditions where hydrates can form from water and gas, characterized in that one incorporates into said fluid additive comprising at least one non-amphiphilic composition ionic obtained by reaction of at least one unsaturated vegetable oil polymerized, with at least one amino alcohol.

Such compositions and their preparation have been described in French patent application filed the same day by the plaintiff, under the national registration number 97/12 049. The content of this request is included in this description by the mention which is made here.

The polymerized unsaturated vegetable oils used to prepare the compositions used in the process of the present invention usually have a viscosity between 5 and 60 Pa.s. These vegetable oils polymerized unsaturated are widely described in the prior art and are for example obtained by heat treatment of highly unsaturated oils such as linseed oil, or safflower oil, seed oil grapes, Chinese wood oil or sunflower oil.

• les monoalcools aminés tels que
• la monoéthanolamine : OH - (CH₂)₂- NH₂,
• la monopropanolamine : OH - (CH₂)₃ -NH₂,
• la monoisopropanolamine : CH₃ -CH (OH) - CH₂ - NH₂,
• le 2-amino-1-butanol : CH₃ -CH₂ - CH (NH₂) -CH₂ - OH,
• le 1-amino-2-butanol : CH₃ - CH₂ - CH(OH) - CH₂ - NH₂,
• la N-méthyl-éthanolamine : CH₂ - NH - (CH₂)₂- OH,
• la N-butyl-éthanolamine: CH₂ - (CH₂)₃ - NH - (CH₂)₂ - OH,
la pentanolamine, l'hexanolamine, la cyclohexanolamine, les polyalcanolamines
ou encore les polyalcoxyglycolamines, de formule : OH - (CH₂ - CH₂ O)_n - CH₂ - CH₂ - NH₂,    où n représente le degré de polymérisation du polyalcoxyglycol ; et les polyols aminés tels que :
• la diéthanolamine : (OH - CH₂ - CH₂)₂- NH,
• la diisopropanolamine: (CH₂ - CH (OH) - CH₂)₂- NH, ou
• le trihydroxyméthylaminométhane : ((HO)H₂C -)₃C - NH₂.

The amino alcohols used to prepare the compositions used in the process of the present invention are chosen, for example, from:

• amino monoalcohols such as
• monoethanolamine: OH - (CH ₂ ) ₂ - NH ₂ ,
• monopropanolamine: OH - (CH ₂ ) ₃ -NH ₂ ,
• monoisopropanolamine: CH ₃ -CH (OH) - CH ₂ - NH ₂ ,
• 2-amino-1-butanol: CH ₃ -CH ₂ - CH (NH ₂ ) -CH ₂ - OH,
• 1-amino-2-butanol: CH ₃ - CH ₂ - CH (OH) - CH ₂ - NH ₂ ,
• N-methyl-ethanolamine: CH ₂ - NH - (CH ₂ ) ₂ - OH,
• N-butyl-ethanolamine: CH ₂ - (CH ₂ ) ₃ - NH - (CH ₂ ) ₂ - OH,
pentanolamine, hexanolamine, cyclohexanolamine, polyalkanolamines
or also the polyalkoxyglycolamines, of formula: OH - (CH ₂ - CH ₂ O) _n - CH ₂ - CH ₂ - NH ₂ , where n represents the degree of polymerization of the polyalkoxyglycol; and amino polyols such as:
• diethanolamine: (OH - CH ₂ - CH ₂ ) ₂ - NH,
• diisopropanolamine: (CH ₂ - CH (OH) - CH ₂ ) ₂ - NH, or
• trihydroxymethylaminomethane: ((HO) H ₂ C -) ₃ C - NH ₂ .

Synthesis of the compositions used in the process of the present invention can be carried out by reaction of an excess of amino alcohol, preferably diethanolamine, on a polymerized unsaturated vegetable oil preferably obtained from linseed oil.

The reaction is generally carried out in the absence of solvent at a temperature for example between 100 and 200 ° C.

At the end of the reaction, to obtain a pumpable mixture, a solvent is added. A number of solvents are likely to be used in especially aromatic cuts; however, preference will be given to all solvents derived from oils or fats, vegetable or animal, in order to obtain a biodegradable and non-polluting additive solution for the environment. Advantageously, the esters of monoalcohols of C1 to C4 and fatty acids from C6 to C22 derived from oils or fats plants chosen for example from coconut, babassu, palm kernel, tucum, murumuru, palm, shea, olive, peanut, kapok, bitter date, papaya, coloquint, croton, nutcracker, purge, hemp, beech, hibiscus, pulghere, camelina, safflower, niger, sunflower, oleic sunflower, rubber tree, coconut, purga, nuts, corn, soy, cotton, sorghum, grapeseed, flax, tobacco, common pine, afzellie, cabbage turnip, mustard, brown mustard, Chinese wood, bancoulier, aleurite, amoora, fir, cramble, peril la, erucic rapeseed, new rapeseed, rapeseed oleic, sesame, cocoa butter, tall oil, wheat germ and castor; animal oils such as fish oils as is or partially hydrogenated; and animal fats such as lard, tallow and melted butter. The preferred esters are the methyl esters or ethyl.

The solvent content in the final mixture will be between 20 and 80% by mass and preferably between 30 and 70% by mass.

In their use as additives to reduce the tendency to agglomeration hydrates, these compositions are added to the fluid at treat at concentrations generally ranging from 0.1 to 5% by mass, preferably 0.2 to 2% by mass, based on water.

To test the effectiveness of the products used in the process of the invention, the transport of hydrate-forming fluids, such as petroleum effluents and hydrate formation tests were carried out from gas, condensate and water, using the equipment described below.

The apparatus has a 10-meter loop made up of inner diameter equal to 7.7 mm; a 2 liter reactor comprising a inlet and outlet for gas, suction and discharge for the mixture: condensate, water and additive initially introduced. The reactor allows pressurize the loop.

Tubes of diameter similar to those of the loop ensure circulation fluids from the loop to the reactor, and vice versa, through a gear pump placed in between. A sapphire cell integrated in the circuit allows a visualization of the circulating liquid, and therefore hydrates, if they have formed.

To determine the effectiveness of the additives according to the invention, the following are introduced: fluids (water, oil, additive) in the reactor; the installation is then carried under a pressure of 7 MPa. Homogenization of liquids is ensured by their circulation in the loop and the reactor, then only in the loop. By following the variations in pressure drop and flow rate, we impose a rapid decrease in temperature, from 17 to 4 ° C (temperature below the hydrate formation temperature), this is then maintained at this value.

The duration of the tests can vary from a few minutes to several hours: a high-performance additive helps maintain the circulation of the suspension hydrates with a pressure drop and a stable flow.

The full description of all requests, all patents and publications, cited above and below, and the corresponding French application 97/12 050, filed September 25, 1997, is included by reference in this description.

The following examples illustrate the invention but should in no way way be considered limiting. Example 3 is given as comparative.

EXAMPLE 1

52 kg of polymerized linseed oil are introduced into a 100 liter reactor with a viscosity of 10 Pa.s and 28 kg of diethanolamine. We heat for 1 hour at 160 ° C. After cooling the reaction product is diluted to 50% by mass in a hydrocarbon fraction having a point initial distillation of 181 ° C and an end point of 212 ° C.

EXAMPLE 2

In Example 1, all else being equal, the product of the reaction is diluted to 50% by mass in a castor methyl ester.

EXAMPLE 3

Example 2 is repeated, except that the product of the reaction is diluted to 50% by mass in a rapeseed methyl ester.

EXAMPLE 4 (comparative)

In this example, we operate with a fluid composed by volume of 10% water and 90% condensate.

• pour les molécules ayant moins de 11 atomes de carbone :
  • 20% de paraffines et d'isoparaffines, 48% de naphtènes, 10 % d'aromatiques ; et
• pour les molécules ayant au moins 11 atomes de carbone :
  • 22% d'un mélange de paraffines, d'isoparaffines, de naphtènes et d'aromatiques.

The weight composition of the condensate is:

• for molecules with less than 11 carbon atoms:
  • 20% paraffins and isoparaffins, 48% naphthenes, 10% aromatics; and
• for molecules with at least 11 carbon atoms:
  • 22% of a mixture of paraffins, isoparaffins, naphthenes and aromatics.

The gas used comprises 98% methane and 2% ethane by volume. The experiment is carried out under a pressure of 7 MPa, maintained constant by gas supply. Under these conditions, we observe the formation a plug in the coil, a few minutes after the start of the hydrate formation (at a temperature of around 10.8 ° C): hydrates form a block and the circulation of the fluid becomes impossible.

EXAMPLE 5

In this example, the procedure is as in Comparative Example 4, with the same fluid, the same gas, and at the same pressure, but we add to the fluid in circulation 1% by mass relative to water, of the product manufactured in Example 1. Under these conditions, an increase in the loss is observed. load during the formation of hydrates (at a temperature of approximately 10 ° C), followed by its decrease and stabilization for more than 24 hours at a temperature of 4 ° C. A temperature drop to 0 ° C does not affect the circulation of the suspension, the hydrates remaining dispersed in fluids.

EXAMPLE 6

All other things being equal, we repeat Example 5 using 1% by mass relative to the water of the product prepared as described in Example 2. Under these conditions, it is observed that the circulation of the fluid is maintained for more than 4 hours at 4 ° C.

EXAMPLE 7

All other things being equal, we repeat Example 5 using 1% by mass relative to the water of the product prepared as described in Example 3. Under these conditions, it is observed that the circulation of the fluid is kept for more than 24 hours at 4 ° C. A drop in temperature at 0 ° C does not affect the circulation of the suspension, the hydrates remaining dispersed in fluids.

The above examples can be repeated with results analogues by substituting the reagents and / or the general or specific conditions described in the invention to those used in these examples.

In view of the above description, the skilled person can easily determine the essential characteristics of the invention and, without departing spirit and scope, make various changes to it, or modifications to adapt it to various uses and installation conditions artwork.

Claims (13)

Method for transporting hydrates suspended in a fluid comprising water, a gas and a liquid hydrocarbon, in conditions where hydrates can form from water and gas, characterized in that an additive comprising to the said fluid is incorporated minus a composition with a nonionic amphiphilic nature obtained by reaction of at least one polymerized unsaturated vegetable oil on at minus one amino alcohol. Method according to claim 1, characterized in that said oil polymerized unsaturated vegetable oil is polymerized linseed oil. Method according to one of claims 1 and 2, characterized in that said linseed oil polymerized at a viscosity at 20 ° C of between 5 and 60 Pa.s. Method according to one of claims 1 to 3, characterized in that the amino alcohol is diethanolamine. Method according to one of claims 1 to 4 characterized in that the additive is conditioned in a solvent consisting of an aromatic cut. Method according to one of claims 1 to 4 characterized in that the additive is packaged in a solvent derived from an oil or fat vegetable or animal. Method according to one of claims 1 to 6 characterized in that the solvent of the additive is a methyl ester of rapeseed. Method according to one of claims 5 to 7 characterized in that the solvent is added so that the final mixture contains between 20 and 80% and preferably between 30 and 70% by mass of solvent. Method according to one of claims 1 to 8 characterized in that said non-ionic amphiphilic composition is incorporated into said fluid at a concentration of 0.1 to 5% by mass relative to the water present. Method according to claim 9, characterized in that said concentration is 0.2 to 2% by mass relative to the water present. Method according to one of claims 1 to 10, characterized in that, in said fluid, said gas comprises at least one hydrocarbon chosen from methane, ethane, ethylene, propane, propene, n-butane , isobutane, and optionally H ₂ S and / or CO ₂ . Method according to one of claims 1 to 11 characterized in that said fluid comprises natural gas. Method according to one of claims 1 to 12, characterized in that said fluid comprises petroleum gas and at least one hydrocarbon liquid.