FR2557198A1 - Agent for recovering oil from underground formations by means of vapour - Google Patents

Abstract

Improved process for recovering the oil from underground formations by means of vapour. It involves injecting into the vapour an effective quantity of a composition comprising an anionic surface-active agent of the type of alkylaryl sulphonate, petroleum sulphonate or alpha -olefin sulphonate, and a hydrotropic agent of the type of alkylaryl sulphonate or alkyl sulphonate. Not only are much better results obtained by the use of this composition than with vapour alone, but the increase in the recovery percentage is far higher than the sum of the increases in recovery percentage obtained with its two constituents used individually.

Description

 The present invention relates to an improved process for recovering oil from underground formations; it also includes a novel surfactant composition to be injected together with vapor into oil-bearing subsurface formations to enhance recovery thereof.

 The use of secondary and tertiary oil recovery techniques, with or without addition of different reagents such as surfactants, water thickening agents, and the like, for the recovery of crude oil, left in formations after extraction of the "primary" oil is well known to those skilled in the art. These displacement methods have been improved by the addition of surfactant compositions in both the secondary and tertiary procedures, for example where formation has already been submerged with water at least once.

 Representative compositions and methods of this prior art are mentioned in the U.S.

 No. 3,348,611 to Reisburg, No. 3,885,626 to Gale et al., No. 3,901,317 to Plummer et al., No. 3,994,342 to Healy et al., and No. 4,295,980 to Motz, all of which describe aqueous flooding techniques with at least one surfactant, and in some cases with viscosity modifiers, co-surfactants, or the like.

Finally, in a field unrelated to this recovery, U.S. Patent No. 3,501,409 discloses a washing liquid detergent composition which comprises the combined detergent with a hydrotrope.

 In addition to these aqueous flooding techniques, mentioned above, steam was also used for secondary and tertiary oil recovery, using the heat effect to obtain heavy oil from the formations in which it is (see for example US Pat. Nos. 3,357,487 and 3,994,345). However, the mechanisms and effects of surfactants at these temperatures and under the various conditions of melatonin, are obscure, and therefore it is impossible to predict, from knowledge of the effects of aqueous surfactant systems. which surfactant, it exists, can be advantageously used in these conditions of recovery by steam.Cela is even more true for the choice of a modifying agent that can increase the effectiveness of the surfactant .

 The present invention overcomes this disadvantage of the prior art, and improve the process of recovery, by steam, secondary or tertiary oil from underground formations. It also relates to a composition that can be used in this process.

 The novel process according to the invention is characterized in that in addition to an anionic surfactant a hydrotrope product is introduced into the formation.

 According to the invention, the anionic surfactant is preferably a long-chain alkyl aryl sulphonate, a petroleum sulphonate, an olefin sulphonate including its derivatives such as ether sulphonate, ethoxylated sulphonate or propoxylated sulphonate. Hydrotropes, as described in detail below, are also sulfonated compounds, but they differ from the surfactants defined above by their considerably lower molecular weight, their high solubility in water, their very short side chains, and their low surfactant properties.

 As is apparent from the examples and description below, the novel composition and methods of the invention, when used in a vapor recovery process, have unexpected advantages over what could be expected from the combined effects of each constituent, that is to say that there is synergy with the results of the vapor alone. For example, in Example 9, the percentage increase in recovery, relative to the steam alone, is 55%, whereas the addition of the percent increase in recovery of the constituents taken individually, only totals 26%. As noted hereinafter, a hydrotrope being by definition a compound that increases the solubility of a surfactant in water, the reinforcing effect found according to the invention is particularly surprising, as one would normally assume that this hydrotrope increases the solubility of the surfactant in the aqueous portion of the vapor, and decreases its solubility in the oily phase, thus making it less effective for the recovery of the oil.

 Moreover, irrespective of the mechanism of action of the hydrotrope, the steam recovery systems themselves differ in many ways from the water recovery systems. Thus, for example, the vapor is present in a gaseous phase, whose mechanisms of recovery of the oil differ from those of water. As it operates in the gas phase, the steam has considerably faster flow speeds, allowing the manifestation of physical effects such as suction. In addition, the condensation of the steam allows a much larger and more efficient heat transfer to the formation and the oil, so that the whole system can be heated to a higher temperature and faster than with water .

Since steam is hotter and less viscous than water, it can reach parts of the reserve that are inaccessible to water. Steam can also distil lighter crude oil fractions, producing unpredictable effects. Finally, steam can move heavy oils, with different compositions from those of light oils displaced by water, also with different effects. It can thus be seen that, since there are marked differences between water and steam recovery systems, the results are unpredictable from one system to another.

 In a preferred embodiment of the invention, the surfactant anionic agent is a long-chain alkyl aryl sulfonate, preferably a benzene or toluene sulfonate, because of its stability at high temperatures of the surrounding vapor in which they must be used. On the other hand, the alkyl xylene sulfonates are much less heat stable, and are therefore not as effective in the context of the present invention.

 By the term "long alkyl" it is meant that the alkyl radical of the aromatic alkyl sulphonate (which may be branched or straight chain) has from 12 to 30 carbon atoms, and preferably an average of about From 16 to 20 carbon atoms, the term "average" means that the alkyl radical can come from hydrocarbon mixtures having on average from 16 to 20 carbon atoms, even though in this mixture lower chain lengths may be present. or higher, pure olefins can also be used as the source of the alkyl group having exactly the desired number of carbon atoms in this range.Thus, in one embodiment of the invention, the alyl radical can come from a source mixture of C14-C20 d-olefin, wherein the molecular weight distribution is such that the side chain of the resulting alkylated product has an average of 16 carbon atoms, even if lower amounts of somewhat shorter or longer chain lengths may be present in the alkylated product.

One of the preferred alkylation products, having an average number of carbon atoms of the order of 16.2 in the side chain, can come from a C14 to C18 α-olefin of cracked wax, and presents the following weight distribution
Carbon atoms Weight distribution
in the chain (%)
lateral ~
C14 2
C15 30
Carbon atoms Weight distribution
in the chain (%)
lateral
C16 30
C17 28
C18 10
Alternatively, the alkylation product can be prepared from a C14-18 mixture from the ethylene polymerization in a known manner, wherein the average alkyl group is 16, and which is further characterized by alkyl groups having only an even number of carbon atoms. A typical weight distribution of such a mixture is shown below
Carbon Atoms Weight Distribution
in the chain (%)
lateral ~~~~~~~~~~~~~~~~~~~~
C14 25
C16 50
C18 25
The alkylation product may also have a side chain derived from the oligomerization of propylene according to known processes, such as for example using as catalyst phosphoric acid, or the like, this side chain which can be of the simple type with carbon number , multiple of 3, that is to say C12, C15 C18 or C21, or being a mixture of these branched oligomers, such that the average molecular weight of the side chain is in the range of C15 to C18.

 Instead of these alkyl aryl sulphonates, it is possible to use petroleum sulphonates as surface-active anionic agents in the compositions according to the invention.

These products include a wide range of compounds that are well known to those skilled in the art, and are generally obtained by sulfonation of natural, liquid hydrocarbons from crude oil. Typical of this broad range are the petroleum sulfonates disclosed in U.S. Patent Nos. 3,302,713, 3,508,612, 3,548,772, and 3,901,317.

 Thus, the term "natural petroleum sulfonates" is a commercial designation for petroleum sulfonates which are obtained by treating petroleum fractions, especially solvent-treated aromatic fractions, with for example fuming sulfuric acid or sulfuric anhydride. During the sulphonation, two types of products are formed which are known to those skilled in the art under the respective names of mahogany acid sulphonates and green acid sulphonates, according to their color and their solubility in the oil or water. water.

dans lesquelles R et R1 peuvent être hydrogène, ou groupes alkyle ayant de 8 à 28 atomes de carbone, et peuvent être semblables ou différents. Les préférés sont les groupes alkyle ayant un total de 10 à 16 atomes de carbone.Bien que
les procédés de préparation de ces oléfines soient généralement bien connus, les sulfonates d'oléfine peuvent être décrits au mieux comme les produits de sulfonation d'hydrocarbures de cire craquée, ayant de l'ordre de 12 à 30 atomes de carbone, ou bien d'oligomères d'éthylène, par exemple ceux qui sont obtenus par des polymérisations du type de Ziegler, et ayant environ de 12 à 30 atomes de carbone.A third type of surfactant anionic agent, which can be used in the compositions described hereinafter, is constituted, as indicated above, by olefin sulfonates, which are substances that are generally commercially available, such as, for example, those which are obtained from olefins manufactured by the "STOP" process of Shell Oil Co. Typically, these olefins can have the following structures

wherein R and R 1 may be hydrogen, or alkyl groups having 8 to 28 carbon atoms, and may be the same or different. Preferred are alkyl groups having a total of 10 to 16 carbon atoms.
the processes for the preparation of these olefins are generally well known, the olefin sulfonates can best be described as cracked wax hydrocarbon sulfonates of the order of 12 to 30 carbon atoms, or ethylene oligomers, for example those obtained by Ziegler-type polymerizations, and having from about 12 to 30 carbon atoms.

Also within the scope of the invention are known derivatives of these olefin sulfonates such as ether sulfonates; ethoxylated sulfonates or propoxy sulfonates. In general, these compounds can be prepared by well-known procedures.

 The preparation of the anionic surfactants, that is to say the alkylation and the sulfonation of the aromatic radical, or the preparation of the olefin or petroleum sulfonates, is carried out according to conventional techniques, which are well known in the art. skilled in the art, and that do not require description here. It is preferred, but not necessary according to the invention, for these sulfonates to be in the form of their alkali metal salts.

The second component of the process or composition according to the invention, to be used in combination with anionic surfactants, is a hydrotrope, that is to say one of the compounds characterized by their ability to increase the solubility of surfactants in aqueous systems. (See for example the description in 2'Synthetic Detergents', Davidsohn et al., 6th Edition,
Wiley and Sons, pages 79 and 80). These compounds include both aryl and non-aryl products. The aryl compounds are generally aryl sulfonates or alkyl (short chain) aryl sulfonates, in the form of their alkali metal salts, in which there may be 1 to 3 alkyl groups containing 1 to 3 carbon atoms, and whose aryl component may be benzene, toluene, xylene, cumene or naphthalene. Preferred aryl hydrotropes are sodium xylene sulfonate, sodium toluene sulfonate, sodium benzene sulfonate, and the like. Also suitable are non-aryl hydrotropes such as sodium isethionate, sodium butane sulphonate, sodium hexane sulphonate, and the like, that is to say sulphonates whose alkyl radical contains from 1 to 8 carbon atoms.

 The mechanism by which these hydrotropes act to increase the potency of the vapor-driven surfactant systems in a liquid, oily, substantially non-aqueous environment is not known. Thus, as hydrotropes increase the solubility of surfactants in water, they should make them less effective, when recovering the oil, for the reasons explained above. However, as can be seen from the examples below, when a hydrotrope is combined with, for example, C₁-C₁ ar alkylsulfonate alkyl, there is a marked increase in oil recovery by compared to the added effects of the two constituents acting in isolation.

 The molar ratio of the anionic surfactant to the hydrotrope in the composition according to the invention is between 1 / 0.1 and 0.1 / 1, and preferably between 1 / 0.5 and 1 / 1.5, although this value can vary greatly depending on the properties of the oil deposit to be treated, as well as depending on the nature of the hydrotrope chosen and that of the resulting composition. It is desirable to add to this mixture a solvent, in order to prepare an easily manipulated solution, to be added to the steam to be injected into the subterranean formation. Water is particularly suitable as a solvent, although light hydrocarbon solvents such as kerosene, toluene, naphtha, petroleum ether, lubricating oil, or similar inert hydrocarbons may be used in its place. Thus, for example, a preparation of a preferred composition ready for addition to steam comprises 35% by weight hexadecyltoluene sulfonate, 17% sodium xylene sulfonate, the balance being water.

 In addition to these two major constituents, the composition may optionally comprise minor amounts of substances known as stabilizers, bacteriostatic, antioxidants. These substances, alone or in combination, may be added up to 10-15% by weight of the total surfactant composition.

 As described above, the surfactant system according to the invention is advantageously injected into the underground formations in a mixture with steam; the steam recovery process is carried out cyclically or by steam entrainment, and the crude heavy oil is recovered in a generally well-known manner. Thus, in a typical steam cyclic process, the oil is produced from the very well through which the steam was previously introduced, while in a typical steam entrainment process, the well oil production is distinct from that of steam injection.

 The amount of hydrotropic surfactant composition according to the invention, mixed with the vapor, can vary widely with the characteristics of the formation, but is preferably in the range of about 0.1 to 10E by weight, relative to the surfactant, an aqueous solution of the composition, and more preferably a concentration of the order of 0.5 to 5%. This concentration, in turn, is achieved by its distribution in steam at these levels from a more concentrated aqueous solution, as described above, prepared in advance.

 In practice, the process of the invention can be applied to both multi-well steam entrainment and a single well cyclic process.

 The composition and the process according to the invention are illustrated with reference to the following nonlimiting examples.

EXAMPLES
In the examples, some of which are given for comparison, while the others illustrate the invention itself, the same basic method is used to determine the interest of the composition; it is the process in which a 50.8 mm diameter and 457.2 mm long tube is loaded with Ottowa sand having a grain size of 0.105 mm saturated with oil. The sand impregnated with water is covered with Midway Sunset crude oil whose residual oil saturation is 60 to 65%. The top 15% of the tube is filled with clean sand, to simulate a high permeability zone, often found in the steam tanks. This tube is insulated to reduce heat loss, and then sand is passed through the sand. steam only, of 40-50t quality, or a vapor of the same quality combined with different surfactant systems, at concentrations of 1% by weight of surfactant based on the total water equivalent of the vapor, and at appropriate speeds , until it becomes obvious that no oil is coming out of the machine. The amount of oil recovered is measured in one or both of the following ways: (1) total oil, liquid, obtained from the filling; (2) the oil remaining in the sand at the end of the experiment is dosed and the quantity recovered is calculated by the difference between the determined value, being in the sand at the start of the experiment and which remains there The percentage of oil recovered for each system, based on the amount of oil originally in the filling, is reported in Table 1 below.

 In the following, Examples 1 to 7 are given for comparison, while Examples 8 to 13 illustrate the composition and method according to the invention.

 the results of these examples show that there is a very clear increase, by almost 55%, in the recovery of the oil with the surfactant system of the invention (Examples 8 to 13) compared to the use steam alone (Example 1), and oil recovery up to 46% higher than that obtained in the prior art with surfactants alone, having average alkyl chain lengths less than 16 ( examples 2, 3 and 4). In addition, there is also a marked improvement, when the effects of the individual constituents of the composition (Examples 5, 6 and 7) are compared with the results explained in the above-mentioned examples 8-13.

EXAMPLE 1
Using the general procedures described above / and passing steam alone through the sand filling of Midway Sunset oil, in a series of operations, an average of 44.5 is recovered. % of this oil.

EXAMPLE 2
The procedures of Example 1 are repeated, but 9.24 ml (counted as 100% surfactant) of the diluted α-olefin sulphonate is added to the vapor, so that its final concentration in the steam is obtained. 1% by weight (relative to the water equivalent), and 48.4% of the original oil is recovered, that is to say that with respect to the recovery obtained with steam alone, there is an increase of 9%.

 The α-α-olefin sulfonate used is a sulfonated C12 olefin olefin prepared from a mixture of α-olefins whose carbon chain lengths are C12, C14 and C161 and wherein The olefin has an average of 14 carbon atoms.

EXAMPLE 3
With the procedures of Example 1, but adding 9.24 ml (100% surfactant) of an alkyl
C12-C14 toluenesulphonate, diluted in such a way that its final concentration in the vapor is 1% by weight relative to the water equivalent), 49.6% of the original oil is recovered, c that is, based on the recovery obtained by steam alone, the increase is 12%.

The alkylation product used in the preparation of the surfactant is a C12-C14 olefin of cracked wax having an average of 12.8 carbon atoms.

EXAMPLE 4
The procedures of Example 1 are repeated, but 9.24 ml (100% surfactant) of a C 10-18 alkyl toluene sulfonate is added to the vapor, diluted so that its final concentration by weight in the steam is 1% (based on the water equivalent), and 58.4% of the original oil is recovered, that is, the increase in recovery obtained by steam alone, is 31.2%. The alkylation product used in this surfactant preparation comes from a C 18 olefin obtained by polymerization of ethylene; this mixture, consisting solely of carbon chains with an even number of carbon atoms, has an average of 14 carbon atoms.

EXAMPLE 5
Using the procedures of Example 1, but with the addition to steam of 9.24 ml (expressed as 100% surfactant) of a C14 alkyl toluene sulfonate, diluted so that its weight concentration, final, in the steam is 1% (relative to the equivalent in water), we recover on two operations an average of 57.4% of the oil in place at the origin, which corresponds to an increase of 29 % compared to recovery by steam alone.

The alkylation product used in the surfactant preparation is derived from a cracked wax C1418 olefin having an average of 16.2 carbon atoms.

EXAMPLE 6
Using the procedures of Example 1, but adding 9.24 ml (100% surfactant) of a C14 alkyl toluene sulfonate to the vapor, diluted in such a way that its final concentration in the vapor was 1 % by weight (relative to the water equivalent), 53.5% of the original oil is recovered, which corresponds to an increase of 20% compared with recovery by steam alone.

The alkylation product used in the surfactant preparation comes from a mixture of carbon chains with even carbon number only, a C1418 olefin obtained by polylization of ethylene, and has an average of 16 carbon atoms. .

EXAMPLE 7
Using the procedures of Example 1, but with steam addition of 9.24 ml (expressed as 100% compound) of sodium xylene sulfonate diluted so that its final concentration is 1% by weight in the steam (relative to the water equivalent), 47% of the original oil is recovered, which corresponds to a 6% increase compared to the recovery by steam alone.

EXAMPLE 8
The process is carried out according to the procedures of Example 1, but using the C14 alkyl toluene sulfonate of Example 5, in combination with sodium xylene sulphonate of Example 7, in a molar ratio of 1: 1. 1, that is, 9.24 ml of alkyl toluene sulfonate (100% count) is mixed with an equivalent molar amount of sodium xylene sulfonate, hydrotrope. This mixture is diluted to give a final concentration in steam of 1%, based on the surfactant and the water equivalent. This recovers 67.3% of the original oil in place, which corresponds to an increase of 51% compared to recovery by steam alone.

EXAMPLE 9
The procedure is as in Example 8, but using the alkyl.

 C14 18 toluene sulfonate of Example 6 in combination with the sodium xylene sulphonate of Example 7, in the same molar ratio of 1/1, and 69% of the oil is recovered in place originally which corresponds to an increase of 55% compared to the recovery performed with steam alone.

EXAMPLE 10
The procedures of Example 8 are repeated, but sodium toluene sulphonate is substituted for sodium xylene sulphonate, and 67.5% of the original oil is recovered, which corresponds to 52% increase over recovery by steam alone.

EXAMPLE 11
In accordance with the procedures of Example 8, but substituting sodium cumene sulfonate for sodium xylene sulfonate, 68.4% of the oil in place was recovered in place, which corresponds to an increase in 54% compared with the recovery obtained with steam alone.

EXAMPLE 12
The procedures of Example 8 are repeated, but 4% of ethylene glycol is added to the hydrotropic surfactant system of Example 9, and this combination is introduced into the steam to recover 68.1% of the oil. originally in place, which corresponds to a 52% increase over steam recovery alone.

EXAMPLE 13
Using the α-olefin of Example 2 in combination with the sodium xylene sulfonate, according to the procedures of Example 8, 66.8% of the oil in place at the origin is recovered. which corresponds to an increase of 50% compared to the recovery obtained with steam alone.

The oil yield percentages recovered from the above examples are summarized in Table 1 on the following page.

TABLE 1
**
Example Surfactant Composition Oil * Increased%
recovery of the reality ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~% recovery
1 Steam alone 44.5
2 QC-olefin C12-16 48.4 9
3 C12-14 alkyl toluene sulfo
nate 49.6 12
4 Aikyl C10-18 "" I '58; 4 31
C14-18 Alkyl """57; 4 29
6 Alkyl C14-18 "" 53.5 20
7 Sodium xylene sulfonate 47.0 6
8 Sulfonates of Ex. 5 + Ex. 7 67,3 51
9 Sulfonates of Ex. 6 + Ex. 7 69.0 55
Toluene Sulfonate Na + Ex.6 67.5 52
11 Cumene Sulfonate Na + Ex.6 68.4 54
12 Ethylene Glycol + Ex 9 67.5 52
13 Xylene Sulfonate Na + Ex.2 66.8 50
* Percentage of original oil in place
** Percentage improvement over steam alone.

Claims (11)

claims  1. Improved method for the enhanced recovery of oil from underground formations, by injection of steam and a surfactant, characterized in that there is further introduced a hydrotrope substance.  2. The process according to claim 1, wherein the surfactant is anionic, wherein the hydrotrope is one or more organic sulfonates.  3. A process according to claim 1 or 2, wherein the surfactant is a sulfonate, in particular alkylarylsulphonate whose alkyl is C12 to C30, petroleum sulphonate or C18 to C30 α-olefin sulphonate, characterized in that the hydrotrope substance is also a sulfonate, preferably of alkali metal, but of much lower molecular weight than that of the surfactant, very soluble in water, carrying short chains and low surfactant.  4. Method according to one of the preceding claims, characterized in that the hydrotrope substance is an arylsulfonate bearing 1 to 3 alkyl groups, the alkyl part having 1 to 3 carbon atoms.  5. Process according to claim 4, characterized in that the hydrotrope is an alkali metal xylene-, toluene-, cumene-, butane- or hexane-sulfonate, or the isethionate of such a metal.  6. Method according to one of the preceding claims, characterized in that 0.1 to 10% by weight of surfactant is introduced into the injection vapor, which is accompanied by the hydrotrope substance in the molar ratio of 1: 0.1 to 0.1: 1.  A surfactant composition for improving vapor recovery of oil in subterranean formations, which comprises an anionic surfactant, in particular a C12-C30 alkylsulfonate alkyl, characterized in that it contains a hydrotrope substance. ,  8. A composition according to claim 7 in the surfactant is a sulfonate, in particular alkyl-aryl-sulfonate whose alkyl is C12 to C30, petroleum sulfonate or sulfonate of C8 to C30 d-olefins, characterized in that the hydrotrope substance is also a sulfonate, preferably of alkali metal, but of much lower molecular weight than that of the surfactant, very soluble in water, carrying short chains and low surfactant.  9. Composition according to one of Claims 7 or 8, characterized in that the hydrotrope agent is an alkyl aryl sulfonate, preferably an alkali metal salt thereof, having 1 to 3 C 1 to C 3 alkyl groups, the aryl group being preferably represented by xylene, toluene or cumene.  10. Composition according to one of Claims 7 or 8 ', characterized in that the hydrotrope agent is an alkali metal isethionate, butane sulphonate or hexane sulphonate.  11. Composition according to one of claims 7 to 10, characterized in that the molar ratio surfactant / hydrotrope is in the range of 1 / 0.1 to 0.1 / 1, and preferably between 1 / 0.5 and 1 / 1.5.