JPS6362636B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a micellar solution used in the micellar attack method for recovering oil from underground reservoirs, and more specifically, to a micellar solution that can form microemulsions at high salt concentrations and whose viscosity can be easily adjusted over a wide range. This invention relates to a micelle solution for recovery. Only a portion of the oil contained in underground oil reservoirs can be recovered using primary recovery methods such as pumping, and the majority remains in the underground reservoirs. In order to recover oil that cannot be recovered by this primary recovery method,
Water or gas is injected into underground reservoirs to increase pressure.
Oil can be recovered by making it more fluid, or by heating underground reservoirs by injecting steam or partially burning the oil in the reservoir to reduce the viscosity of the oil and make it more fluid. A variety of tertiary recovery methods have been proposed, including secondary recovery methods in which wastewater is recovered using water, and improved secondary recovery methods that combine these secondary recovery methods or use surfactants or aqueous polymers. , these are commonly referred to as Enhanced Oil Recovery (EOR). In order to transport oil stored in such underground reservoirs toward oil extraction wells, it is necessary to have a viscosity equal to or higher than that of oil and a low interfacial tension between the injection fluid and the oil. is said to be necessary. A method has been proposed in which a micellar solution in the form of a microemulsion is used as an injection fluid with a low oil-water interfacial tension, and is generally called the micellar attack method. There are many prior arts related to this micellar attack method, such as U.S. Patent No. 3506070 and U.S. Pat.
No. 3613786, No. 3740343, No. 3983940, No. 4017405 and No. 4059154, and Special Publication No. 1974
Examples include Japanese Patent Publication No. 42005 and Japanese Patent Publication No. 56-2597. Among these prior art, surfactants that can be used for producing micellar solutions include:
Various anionic, nonionic, and cationic surfactants are exemplified, and it is disclosed that each can be used alone or in combination. Examples of such surfactants include petroleum sulfonates, alkylaryl sulfonates, dialkyl sulfosuccinates, alkanesulfonates, polyoxyethylene alkyl ether sulfates, polyoxyethylene alkyl ethers,
polyoxyethylene alkyl phenyl ether,
Examples include polyhydric alcohol fatty acid esters, alkyltrimethylammonium salts, and dialkyldimethylammonium salts. The surfactant used in such a micelle solution is required to be inexpensive and easily available since the amount of the micelle solution used is large, but at the same time it must be one that satisfies the above-mentioned required performance. There must be. Moreover, the number of oil fields is very large;
Therefore, since the properties of underground reservoirs are diverse, the available water ranges from soft water containing almost no inorganic salts to brine containing large amounts of inorganic salts and polyvalent metal ions. Therefore, the surfactant used in the micelle solution must have good heat resistance, salt resistance, and hard water resistance. Furthermore, the viscosity of petroleum contained in underground reservoirs varies, and as mentioned above, the viscosity of the injected fluid needs to be equal to or higher than that of petroleum, and the lower the viscosity of the injected fluid, the better the oil recovery operation. It is preferable that the micelle solution has a viscosity comparable to that of petroleum contained in underground reservoirs, and therefore it is desirable that the viscosity of the micelle solution can be easily adjusted according to the properties of the oil field. In particular, since oil fields that are subject to forced oil recovery methods often contain highly viscous oil, micellar solutions with high viscosity are suitable for use in forced oil recovery methods. Since the injection fluid injected into underground reservoirs in the forced oil recovery method is used in extremely large quantities, low cost is essential, and petroleum sulfonates are currently the most suitable injection fluid for use in the micellar attack method. It is said that However, petroleum sulfonates are unsatisfactory in terms of salt resistance, hard water resistance, and viscosity control, and have the problem of being applicable only to special oil fields. Therefore, attempts have been made to improve the performance of petroleum sulfonates by using them in combination with other surfactants or water-soluble polymer thickeners, but no results have been obtained that satisfy both performance and cost. . Therefore, an object of the present invention is to provide a micelle solution for oil recovery that has excellent salt resistance, hard water resistance, and viscosity control properties. That is, according to the invention, in a micellar solution used as an injection fluid for forced petroleum recovery consisting essentially of a hydrocarbon, water which may contain inorganic salts, a surfactant and a surfactant auxiliary, the surfactant Provided is a micellar solution using an α-olefin sulfonate having 15 to 30 carbon atoms as an essential component. Since the micelle solution of the present invention uses high-grade α-olefin sulfonate as an essential component of the surfactant, it has improved hard water resistance and markedly improved salt resistance, and the presence of inorganic salts further reduces the oil-water interfacial tension. It has the effect of further reducing the Furthermore, since this micelle solution forms a microemulsion even in the presence of a large amount of inorganic salt, the viscosity of the micelle solution can be easily adjusted over a wide range by changing the concentration of the inorganic salt. Micellar solutions of the present invention suitable for use as injection fluids for forced oil recovery contain hydrocarbons of from about 4 to about 90
Weight%, water about 4 to about 92% by weight, α with carbon number 15 to 30
- from about 3 to about 30% by weight of a surfactant consisting essentially of olefin sulfonate and about a surfactant auxiliary;
It is a clear microemulsion containing from 0.1 to about 20% by weight. Water that can be used in the micellar solution of the present invention may be soft water, brackish water, or brine, such as rainwater, river water,
Lake water, groundwater, oil layer water and seawater can all be used freely. The micellar solution of the present invention uses α-olefin sulfonate, which has good hard water resistance, as an essential component of the surfactant, so it has excellent hard water resistance, and especially for Mg ions, it has a resistance of about 5000 PPM.
(approximately 2.6% as _MgSO4 ) is allowed.
The micellar solution of the present invention also has surprising resistance to alkali metal salts, and regardless of the type of alkali metal salt, it can be tolerated even at a concentration of about 10% in the water used. Depending on the combination of surfactants and the selection of surfactant auxiliaries, it is possible to use up to a brine concentration of about 15%. Furthermore, surprisingly, it was found that in the micelle solution of the present invention, the oil-water interfacial tension was further reduced when the concentration of the inorganic salt was increased. Therefore, the concentration of inorganic salts in the water that can be used to prepare the micellar solutions of the present invention is from 0 to about 15% by weight, especially from about 0.5 to about 12% by weight, especially from about 1 to about 1% by weight.
10% by weight is preferred. Examples of alkali metal salts contained in water (brine) containing inorganic salts are NaCl,
KCl, _{Na2SO4 and K2SO4} are representative _. For example, seawater has an inorganic salt concentration of about 3.5% and contains about 1600 PPM of divalent metal ions in terms of Mg ions, and such salt concentrations are within the preferred range of the present invention. The higher α-olefin sulfonate that the micelle solution of the present invention contains as an essential component of the surfactant is obtained by sulfonating an α-olefin having 15 to 30 carbon atoms, neutralizing it with appropriate chlorine, and hydrolyzing it as necessary. Manufactured by The α-olefin used in the production of the α-olefin sulfonate of the present invention can be linear or branched.
Preferred α-olefins are linear and vinylidene-branched. α-olefin sulfonates derived from linear α-olefins are mixtures containing alkenyl sulfonates, hydroxyalkanesulfonates, and disulfonates as main components, and vinylidene-type α-olefin sulfonates contain alkenyl sulfonates as main components with minor components. This includes hydroxyalkanesulfonates and disulfonates. In the micelle solution of the present invention, when the lipophilicity of α-olefin sulfonate is high, the ability to lower the oil-water interfacial tension is large, so the types and blending ratios of usable hydrocarbons and surfactants should be selected within a wide range. As a result, there are fewer restrictions on the oil fields to which the micellar solution of the present invention can be applied. Therefore, preferable α-olefin sulfonates are those having 18 to 30 carbon atoms, and particularly preferably 50% by weight or more of the α-olefin sulfonates are those having 0 to 28 carbon atoms. The α-olefin sulfonate used in the present invention is selected from alkali metal salts, alkaline earth metal salts, ammonium salts and organic amine salts of α-olefin sulfonic acid. Preferred countercations are Na, K, Mg, _NH4 and alkanolammonium. Examples of α-olefin sulfonates suitable for the present invention are: α-olefin sulfonate having 18 carbon atoms α-olefin sulfonate having 20 carbon atoms α-olefin sulfonate having 21 carbon atoms α-olefin sulfonate having 22 carbon atoms 23 carbon atoms α-olefin sulfonate with 24 carbon atoms α-olefin sulfonate with 26 carbon atoms α-olefin sulfonate with 18 to 20 carbon atoms α-olefin sulfonate with 20 to 24 carbon atoms α-olefin with 20 to 28 carbon atoms Such as sulfonates. The micelle solution of the present invention contains a surfactant of about 3 to
However, considering the low oil-water interfacial tension and cost, the surfactant content is preferably about 5 to about 25% by weight. Since α-olefin sulfonate is an essential component, the proportion of higher α-olefin sulfonate in the surfactant is at least 50% by weight, preferably 70% by weight.
The above is desired. The hydrocarbon used as the oil phase component of the present invention can be petroleum, liquefied petroleum gas, crude gasoline (naphtha), kerosene, light oil, heavy oil, etc. It is preferable to use recovered petroleum, considering that it is similar in crude oil to the petroleum contained therein. The proportion of hydrocarbons in the micelle solution of the present invention is about 4 to about 90% by weight, but since it is economically disadvantageous to use a large amount of hydrocarbons, oil-in-water (O/W) type injection is preferred. Therefore, the proportion of hydrocarbons is preferably from about 5 to about 40% by weight. In the micellar solution of the present invention, the surfactant auxiliary is an essential component that cooperates with the surfactant to form a microemulsion. The surfactant used in the present invention is a compound having an alcoholic hydroxyl group, and preferably has the general formula RO(CH ₂ CH ₂ O) _o H (where n is a number from 0 to about 4 and R is , n=0
In the case of , it is an alkyl group or alkenyl group having 4 to 8 carbon atoms, and when n is not 0, it is an alkyl group, alkenyl group or alkylphenyl group having 6 to 18 carbon atoms, and an aliphatic group is a direct aliphatic group. These are small water-soluble alcohols that can be chain-like or branched-chain. Specific examples of such alcohols include butanols, pentanols, hexanols, 2-ethylhexanol, other octanols, polyoxyethylene hexyl ether (=1), polyoxyethylene decyl ether (=2), Examples include polyoxyethylene tridecyl ether (=4), polyoxyethylene butyl phenyl ether (=2), polyoxyethylene nonyl phenyl ether (=3), polyoxyethine dodecyl phenyl ether (=4), etc. . The surfactant used in the present invention is used in the micelle solution in an amount of about 0.1 to about 20% by weight, but from the viewpoint of stability of the microemulsion and ability to lower the oil-water interfacial tension, the amount is about 1 to about 10% by weight. Preferably, % by weight is used. The micellar solution of the present invention contains α-olefin sulfonate as an essential component of the surfactant. Other surfactants may be used in combination in consideration of the cost and availability of the surfactant. Examples of such surfactants include petroleum sulfonates, alkylbenzene sulfonates, polyoxyethylene alkyl ether sulfates, dialkyl sulfosuccinates, lower alpha-olefin sulfonates, paraffin sulfonates, internal olefin sulfonates, soaps, higher alcohol ethoxylates. , alkylphenol ethoxylate, polyhydric alcohol fatty acid ester, fatty acid alkylolamide, polyoxyethylene fatty acid amide, and other anionic surfactants and nonionic surfactants. The micellar solution of the present invention can form a good microemulsion even when using brine containing a large amount of inorganic salts, so in order to increase the viscosity of the micellar solution, inorganic salts or water-soluble polymers etc. The desired viscosity can be easily achieved by appropriately selecting and adding a thickener. On the other hand, in order to lower the viscosity of the micelle solution, the desired viscosity can be achieved by lowering the concentration of inorganic salts or adding lower alcohols such as methanol, ethanol, and isopropanol. In particular, by adding inorganic salts (alkali metal salts), a highly viscous micellar solution can be obtained, which has the potential to be applied to oil fields with residual high viscosity oil, which was difficult to apply in the past. It has advantages. Known thickeners such as water-soluble polymers can also be used in the micelle solution of the present invention, and examples of such thickeners include heteropolysaccharides produced by microorganisms, formalin naphthalene sulfonate, etc. Examples include condensates, polyacrylamides, polyacrylates, hydroxyethyl cellulose, carboxymethyl cellulose, and the like. The micelle solution of the present invention can be easily produced by a known emulsion production method, and the order of addition of each component, stirring and mixing method, temperature, pressure, etc. can be arbitrarily selected. The method for recovering oil from underground reservoirs using the micellar solution of the present invention is similar to the known micellar attack method, in which the micellar solution is injected from at least one injection well toward an oil-producing well; A seed driving fluid can be introduced to recover the oil. The appropriate amount of micelle solution to be injected at this time is 5 to 15% by volume of the porosity of the underground reservoir. As mentioned above, the micellar solution of the present invention has good hard water resistance, good salt resistance, and can be easily obtained in various viscosities from low to high viscosity, so (1) it can be used freely in both soft water and seawater. (2) The injected micellar solution is hardly affected by the inorganic salts present in the underground reservoir; (3) The micellar attack method can be easily applied to underground reservoirs containing highly viscous oil. It is possible to obtain excellent effects such as: Next, the present invention will be explained in more detail with reference to Examples, but it goes without saying that the present invention is not limited to these Examples. The component proportions in each sample used in the experiment are weight % unless otherwise indicated. Example 1 A composition consisting of an anionic surfactant, a surfactant, a hydrocarbon, and water was prepared as a sample. As the anionic surfactant, C ₁₆ to C ₁₈ α-olefin sulfonate soda salt, C ₂₀ to _{C 24} α-olefin sulfonate soda salt, or petroleum sulfonate (TRS-10, manufactured by Witco) was used.
Amyl alcohol or isopropyl alcohol was used as surfactant auxiliary. Hydrocarbons are
Kerosene or A heavy oil (ASTM No.2 Oil) was used. Seawater (salt concentration approximately 3.5%, alkaline earth metal ion concentration approximately 1600 PPM) or soft water was used. Micelle solution samples were prepared by mixing aniline surfactant in water, then adding surfactant co-agent and hydrocarbon and stirring. The composition and properties of the sample thus prepared are listed in Table-1. Note that α-olefin sulfonate is abbreviated as AOS. In Table 1, the appearance was evaluated as ○ if a microemulsion was formed, and × if a microemulsion was not formed and was suspended. Sample numbers 1, 5, 7, 9, 11 and 13 are examples of the present invention; sample numbers 2, 3, 6, 8, 10, 12 and 14
is a comparative example. For reference, sample number 4 is an example showing that a microemulsion can be made by using soft water in the case of petroleum sulfonate.

[Table] Example 2 A sample of micelle solution was prepared in the same manner as in Example 1. The water used was brine prepared by dissolving sodium chloride in deionized water and adjusting it to a predetermined salt concentration. The composition and properties of the sample are shown in Table 2. Judgment of appearance is the same as in Example 1.

[Table] As is clear from the results in Table 2, when petroleum sulfonate soda salt is used, a microemulsion cannot be formed when the salt concentration of the brine is 2% by weight, and it is used as a micellar solution for the micellar attack method. Can not. On the other hand, when α-olefin sulfonate soda salt, which is an example of the present invention, is used, a microemulsion is formed when the salt concentration of the brine is in the range of 0.5 to 7.5% by weight, indicating that it can be used as a micelle solution. . Example 3 Samples were prepared in a similar manner to Example 1. The water used is brine prepared by adding sodium chloride to deionized water to a concentration of 1% by weight, and further adding magnesium chloride and/or calcium chloride to a predetermined divalent metal ion concentration. It is. The composition and properties of the sample are shown in Table 3. The appearance was judged in the same manner as in Example 1.

【table】

[Table] As is clear from the results in Table 3, when AOS is used as a surfactant, even when the Mg ion concentration in brine is as high as 4000 PPM, Ca and Ca
It can be seen that even when the total concentration of ions and Ca ions is as high as 3000 PPM, a microemulsion can be made and used for micellar attack. Example 4 Samples were prepared in a similar manner to Example 1. This example shows the use of lower alcohols to reduce viscosity and the use of other surfactant aids. The composition and properties of the sample are shown in Table 4. The appearance was evaluated in the same manner as in Example 1.

【table】

[Table] As is clear from the results in Table 4, it can be seen that lower alcohols such as methanol can be used to produce a micelle solution with low viscosity using seawater. It is also understood that various alcohol compounds can be used as surfactant aids.

Claims (1)

[Scope of Claims] 1. A micellar solution for petroleum recovery consisting essentially of a hydrocarbon, water which may contain an inorganic salt, a surfactant, and a surfactant auxiliary, in which a surfactant having a carbon number of 15 to 30 is used. A micelle solution for oil recovery characterized by using α-olefin sulfonate. 2. The micelle solution according to claim 1, wherein α-olefin sulfonate having 18 to 30 carbon atoms is used as a surfactant. 3. The micellar solution according to claim 1, which contains an inorganic salt as an essential component.