RU2798190C2 - Method for gas extraction from underground reservoir - Google Patents

Abstract

FIELD: treatment of gas reservoirs.

SUBSTANCE: in a method for extracting gas from an underground gas reservoir, which includes displacing gas from zones of an underground gas reservoir characterized by low water and gas permeability, and extracting gas from an underground gas reservoir, to increase the degree of gas displacement, an aqueous solution of a non-ionic surfactant - ethoxylated alcohol of the general formula where n is a number from 82 to 87; R1 is a hydrocarbon group containing 12 to 14 carbon atoms, is pumped into the underground gas reservoir. The hydrophilic-lipophilic balance of said ethoxylated alcohol is greater than 18.8. At the same time, water in an aqueous solution has a total amount of dissolved salts up to 250,000 mg/l. The content of said ethoxylated alcohol in aqueous solution ranges from 0.01 to 40.00%.

EFFECT: increased degree of gas recovery from gas reservoirs, preferably carbonate gas reservoirs with low permeability, by improving rock wettability in water.

5 cl, 4 tbl, 31 ex

Description

More than half of the world's gas reserves are contained in deposits of the carbonate type. The formation characteristics of these fields include fracturing, low permeability, hydrophobicity, and make it difficult to extract gas. This is due to the fact that gas located in high-permeability zones of the reservoir is involved in the displacement process, while the gas contained within the low-permeability matrix of the rock is retained due to negative capillary pressure due to the fact that the porous matrix is characterized by hydrophobicity.

The present invention is gas reservoir treatment compositions and methods for improving gas recovery from gas reservoirs, preferably low permeability carbonate gas reservoirs. More precisely, the invention relates to the use of substances that improve the wettability of the rock in water (increased hydrophilicity). When using substances of this kind, conditions arise for increasing the degree of gas displacement from the zones of the gas reservoir, which are characterized by low water and gas permeability.

Due to the increase in the number of carbonate deposits involved in development, many laboratories have directed research to find compositions of substances that, when added to injected water, can increase the degree of gas recovery from carbonate reservoirs. At present, a large number of surfactants have been developed that have the properties of increasing the wettability of the rock (in the direction of wetted water). However, in some cases, the geological and physical characteristics of gas reservoirs include factors that affect the effectiveness of the use of such surfactants. These factors include an increased formation temperature and an increased content of salts dissolved in the formation water. Under these conditions, the solubility of a number of surfactants decreases, which entails a deterioration in the functional properties of the compositions of substances. The task of selecting highly effective compositions of surfactants that are resistant to elevated temperatures and a high content of dissolved salts is relevant and needs to be addressed as part of work to improve the efficiency of gas production technologies.

Various methods of using non-ionic surfactants in extracting gas from underground formations are disclosed, for example, in WO/2013/110774, EN 2709261, US 9296942, US 3799264 and US 4276933. The references suggest the use of ethoxylated alcohols, the number of ethylene oxide groups in which does not exceed 70. It should be noted that depending on the conditions for obtaining ethoxylated alcohols, the number of ethylene oxide groups can vary and determine the physicochemical properties of the data substances.

Currently, a group of substances has been identified that increase the stability of the functional properties of surfactant compositions at temperatures above 70°C and the content of dissolved salts up to 250,000 mg/L. In this regard, within the framework of the use of these compositions, conditions arise for maintaining low values of interfacial tension (water - hydrocarbon liquid), ensuring spontaneous absorption of water containing compositions of surfactants (into a rock matrix of low permeability), which leads to more high displacement ratios and reduced risks of gas and condensate jamming in low-permeability reservoir zones. The use of these substances under these conditions is significant for the gas industry and allows achieving higher gas and condensate recovery rates.

In view of the above, the object of the present invention is achieved by a method for extracting gas from an underground gas reservoir, including the displacement of gas from zones of the underground gas reservoir characterized by low water and gas permeability, and extracting gas from the underground gas reservoir, in which to increase the degree of gas displacement in an underground gas reservoir is pumped with an aqueous solution of a nonionic surfactant - ethoxylated alcohol of general formula (I)

where n is a number from 82 to 87;

R ₁ represents a hydrocarbon group containing from 12 to 14 carbon atoms;

the hydrophilic-lipophilic HLB balance of said ethoxylated alcohol is greater than 18.8;

while water in an aqueous solution has a total amount of dissolved salts up to 250,000 mg/l;

and the content of the ethoxylated alcohol of formula (I) in the aqueous solution is from 0.01 to 40.00%.

The aqueous solution may additionally contain an amphoteric surfactant of the general formula

where R ₂ represents a hydrocarbon group containing from 12 to 14 carbon atoms;

wherein the ratio of ethoxylated alcohol of formula (I) and surfactant of formula (II) is from 1:12 to 1:1.5.

The aqueous solution may further contain an anionic sulfonate-type surfactant of the general formula

where R ₃ represents a hydrocarbon group containing from 12 to 14 carbon atoms;

wherein the ratio of ethoxylated alcohol of formula (I) and surfactant of formula (III) is from 1:10 to 1:1.5.

The aqueous solution may further contain an anionic sulfonate-type surfactant of the general formula

where R ₄ represents a hydrocarbon group containing from 10 to 12 carbon atoms;

wherein the ratio of ethoxylated alcohol of formula (I) and surfactant of formula (IV) is from 1:10 to 1:1.5.

The aqueous solution may additionally contain a mixture of anionic surfactants of formulas (III) and (IV), while the ratio of the content in this case, the ratio of ethoxylated alcohol of formula (I) and the total content of anionic surfactants of formulas (III) and (IV) is equal to from 1:10 to 1:1.5.

The proposed nonionic surfactants according to claim 1 are ethoxylated alcohols, soluble in water and saline solutions.

Structure (I) is an ethoxylated alcohol,obtained by ethoxylation of alcohols under various conditions.

The proposed ethoxylated alcohols have improved properties in terms of gyrophilicity and cloud point. An increase in the number of ethylene oxide groups contributes to an increase in the solubility of ethoxylated alcohols, thereby expanding the scope of these substances towards higher temperatures.

Another object of the present invention is also a method for increasing the degree of gas recovery from reservoirs, which includes the preparation of an aqueous or saline solution containing a nonionic surfactant of formula (I) in concentrations from 0.01 to 40.00 wt%.

The presented ethoxylated alcohols contribute to the formation of stable microemulsions capable of absorbing large volumes of hydrocarbon liquid and solubilizing additional surfactants in microdroplets.

In particular, the best results have been obtained with ethoxylated alcohols having an HLB greater than 18.8. These substances were used in the examples below.

The alcohols according to the invention have surface-active properties and change the interfacial tension at the water-hydrocarbon liquid interface. It is noted that when using this series of alcohols, the value of surface tension decreases as alcohols with a higher degree of ethoxylation are used. In particular, a number of alcohols contribute to the reduction of interfacial tension to values of 1.0 - 3.5 mN/m. This property can also improve the filtration of a water-hydrocarbon liquid emulsion (in particular, gas condensate) and gas displacement in water-jammed formation zones. Also, the long-term accumulation of water and, in particular, the absence of its filtration in stagnant zones of the reservoir, can contribute to the swelling of clays (which entails an additional deterioration in the porosity and permeability properties of the reservoir).

Another object of the present invention is also a method for increasing the degree of gas recovery from reservoirs, including the preparation of an aqueous or saline solution containing a nonionic surfactant specified in formula (I) and subsequent injection into the reservoir, provided that the water in the solution has a total amount of dissolved salts up to 250000 mg/l. In this case, within the framework of the use of a nonionic surfactant, a liquid hydrocarbon containing from 6 to 30 carbon atoms can act as a co-solvent in these solutions.

The use of microemulsions based on the use of the proposed non-ionic surfactants indicated in formula (I) as additives in the process of extracting gas captured by the skeleton of the rock constituent formations preferably carbonate, leads to an increase in wetting rate and subsequent transport of anionic surfactants or amphoteric surfactants into the rock matrix.

The additives according to the invention were selected using two tests.

The first test is based on the ability of additives to increase the solubility of additional surfactants in water with a high content of dissolved salts, and the second test includes an assessment of interfacial tension at the water-hydrocarbon liquid interface at elevated temperature.

These methods are simple and effective for evaluating the effectiveness of applied nonionic surfactants (ethoxylated alcohols).

The first method is based on the properties of ethoxylated alcohols to create miroemulsion, solubilize anionic surfactants of the sulfonate type or amphoteric surfactants, and maintain the properties of these substances under various conditions (increased content of dissolved salts and elevated temperature). This method allows a preliminary assessment and selection of effective ethoxylated alcohols. In particular, this method includes the preparation of aqueous solutions containing dissolved salts, compositions of surfactants and subsequent thermostating of these solutions at an elevated temperature. The content of compositions of surfactants (including ethoxylated alcohols and additional surfactants) in the solution is 0.1% of the mass. After thermostatting, the stability of the solutions is evaluated (assessment of the presence of sediment or stratification). The test conditions imply the use of aqueous solutions containing dissolved salts from 100,000 to 250,000 mg/l at a temperature of 74°C, while the duration of thermostating is from 10 to 30 days. It should be noted that it is preferable to carry out the evaluation using an aqueous solution with a dissolved salt content of 250,000 mg/l.

The second test measures the interfacial tension. Measurements are made to evaluate the surface properties of solutions using solutions that have shown a positive result in test no. . The measurements are carried out using a Kruss tensiometer using the hanging drop method.

EXAMPLES

The test results are presented in tables 1, 2, 3 and 4. The tests were carried out in accordance with the procedures described in test No. 1 and test No. 2 and detailed below. In particular, the purpose of Test No. 1 was to conduct a preliminary assessment of the effect of various ethoxylated alcohols on the stability of solutions of surfactants in water with a high content of dissolved salts. The subsequent evaluation of the most effective solutions was carried out by measuring the interfacial tension, carried out as part of test No. 2. Since solutions that did not pass test No. 1 are not suitable for use in the conditions under consideration; in test No. 2, only solutions that showed stability during thermostating were tested.

Test. 1 Evaluation of the stability of the compositions at an increased content of dissolved salts and elevated temperature. The test was carried out in two stages.

A. Thermostating at the content of dissolved salts - 100,000 mg/l for 30 days.

The test included pre-preparation of 16 solutions containing various types of emulsifiers (including a range of ethoxylated alcohols) and additional surfactants. When preparing these solutions, water with a content of dissolved salts of 100,000 mg/l was used. Thermostating of these solutions was carried out at a temperature of – 74°C.

b. Thermostating at the content of dissolved salts - 250,000 mg/l for 10 days.

The test included the preliminary preparation of 6 solutions that passed step a. When preparing these solutions, water with a content of dissolved salts of 250,000 mg/l was used. Thermostating of these solutions was carried out at a temperature of – 74°C.

Test. 2 Measurement of interfacial tension of solutions at the water-hydrocarbon liquid interface.

The measurements were carried out for compositions that showed good results, within the framework of stages a and b of test No. 1. The Kruss tensiometer was used in the measurements. The measurements were carried out using the hanging drop method.

Examples 1-16

In accordance with the procedure described for test No. 1 stage a, the stability of various compounds was evaluated at an increased content of dissolved salts (100,000 mg/l) and an elevated temperature (74°C) for 30 days. Table 1 presents the results associated with studies of the compositions of ethoxylated alcohols within the framework of stage a of test No. 1.

Table 1
The results of the evaluation of the stability of solutions containing ethoxylated alcohols of various types and other compounds Examples Aqueous solution with NaCl content - 100000 ppm, alpha-olefin sodium sulfonate of the following substance Substance HLB range
according to Griffin The range of the degree of ethoxylation of a substance Test results Example 1 Ethoxylated lauryl alcohol 15.0 - 17.0 20 - 25 unstable Example 2 Ethoxylated oleyl alcohol 15.0 - 17.0 33 - 38 stable Example 3 Ethoxylated lauryl alcohol 8.0 - 10.0 3 - 8 stable Example 4 Ethoxylated lauryl alcohol 16.5 - 18.5 47 - 52 stable Example 5 Ethoxylated oleyl alcohol 12.0 - 14.0 12 - 17 unstable Example 6 Ethoxylated alcohol (C12-C14) Over 18.8 82 - 87 stable Example 7 Ethoxylated oleyl alcohol 10.0 - 12.0 5 - 10 unstable Example 8 Ethoxylated oleyl alcohol 8.0 - 10.0 15 unstable Example 9 C9-11 Paret-5 10.0 - 12.0 15 unstable Example 10 PPG-5 Lauret-4 2.0 - 6.0 15 unstable Example 11 Lauret-2 6.0 - 8.0 15 unstable Example 12 Lauret-3 7.0 - 9.0 15 unstable Example 13 PPG-5 Lauret-5 4.0 - 6.0 15 unstable Example 14 Ethoxylated Stearyl Alcohol (Brij S20) 15.0 - 17.0 20 - 25 stable Example 15 PEG-8 Sorbitan monolaurate 14.0 - 16.0 17 - 22 unstable Example 16 PEG-16 Sorbitan monolaurate 15.0 - 17.0 20 - 25 unstable

Examples 17-22

In accordance with the procedure described for test No. 1 stage b, the stability of various compounds was evaluated at an increased content of dissolved salts (250,000 mg/l) and an elevated temperature for 10 days. Table 2 presents the results associated with studies of the compositions of ethoxylated alcohols, within the framework of stage b of test No. 1.

table 2
The results of the evaluation of the stability of solutions containing ethoxylated alcohols of various types and other compounds Examples Aqueous solution containing NaCl - 250000 ppm, alpha-olefin sodium sulfonate and the following substance Substance HLB Range
according to Griffin The range of the degree of ethoxylation of a substance Test results Example 17 Ethoxylated lauryl alcohol 15.0 - 17.0 20 - 25 unstable Example 18 Ethoxylated oleyl alcohol 15.0 - 17.0 33 - 38 stable Example 19 Ethoxylated lauryl alcohol 8.0 - 10.0 3 - 8 unstable Example 20 Ethoxylated lauryl alcohol 16.5 - 18.5 47 - 52 stable Example 21 Ethoxylated Stearyl Alcohol (Brij S20) 15.0 - 17.0 20 - 25 stable Example 22 Ethoxylated alcohol (C12-C14) Over 18.8 82 - 87 stable

Examples 23 - 31

In accordance with the procedure described for test No. 2, measurements of interfacial tension were performed.

The test results are presented in tables 3 and 4

Table 3
The results of measurements of interfacial tension in compositions containing various types of ethoxylated alcohols and other compounds Examples Aqueous solution containing NaCl - 100,000 ppm, alpha-olefin sodium sulfonate and the following substance Substance HLB Range
according to Griffin The range of the degree of ethoxylation of a substance The value of the interfacial tension of the composition, mN/m Note Example 23 Ethoxylated lauryl alcohol 16.5 - 18.5 47 - 52 1.4 Measuring temperature +48°C Example 24 Ethoxylated oleyl alcohol 15.0 - 17.0 32 - 37 1.56 Measuring temperature +55°C Example 25 Ethoxylated lauryl alcohol 8.0 - 10.0 3 - 8 1.3 Example 26 Ethoxylated Stearyl Alcohol (Brij S20) 15.3 20 2.52 Example 27 Ethoxylated alcohol (C12-C14) Over 18.8 over 82 1.05

Table 4
The results of measurements of interfacial tension in compositions containing various types of ethoxylated alcohols and other compounds Examples Aqueous solution containing NaCl - 250000 ppm, alpha-olefin sodium sulfonate and the following substance Substance HLB Range
according to Griffin The range of the degree of ethoxylation of a substance The value of the interfacial tension of the composition, mN/m Note Example 28 Ethoxylated lauryl alcohol 16.5 - 18.5 47 - 52 1.42 Measuring temperature +55°C Example 29 Ethoxylated oleyl alcohol 15.0 - 17.0 33 - 38 1.74 Example 30 Ethoxylated Stearyl Alcohol (Brij S20) 15.3 20 3.21 Example 31 Ethoxylated alcohol (C12-C14) Over 18.8 over 82 1.15

Claims (19)

1. A method for extracting gas from an underground gas reservoir, including the displacement of gas from the zones of the underground gas reservoir, characterized by low permeability to water and gas, and the extraction of gas from the underground gas reservoir, characterized in that to increase the degree of gas displacement, water is pumped into the underground gas reservoir. solution of nonionic surfactant surfactant - ethoxylated alcohol of general formula (I)

(I) where n is a number from 82 to 87; R ₁ represents a hydrocarbon group containing from 12 to 14 carbon atoms; the hydrophilic-lipophilic HLB balance of said ethoxylated alcohol is greater than 18.8; while water in an aqueous solution has a total amount of dissolved salts up to 250,000 mg/l; and the content of the ethoxylated alcohol of formula (I) in the aqueous solution is from 0.01 to 40.00%. 2. The method according to p. 1, characterized in that the aqueous solution additionally contains an amphoteric surfactant of the general formula

(II) where R ₂ represents a hydrocarbon group containing from 12 to 14 carbon atoms; the ratio of the content of ethoxylated alcohol of formula (I) and surfactant of formula (II) is from 1:12 to 1:1.5. 3. The method according to p. 1, characterized in that the aqueous solution additionally contains an anionic surfactant of the sulfonate type of the general formula

(III) where R ₃ represents a hydrocarbon group containing from 12 to 14 carbon atoms; the ratio of the content of ethoxylated alcohol of formula (I) and surfactant of formula (III) is from 1:10 to 1:1.5. 4. The method according to p. 1, characterized in that the aqueous solution additionally contains an anionic surfactant of the sulfonate type of the general formula

(IV) where R ₄ represents a hydrocarbon group containing from 10 to 12 carbon atoms; the ratio of the content of ethoxylated alcohol of formula (I) and surfactant of formula (IV) is from 1:10 to 1:1.5. 5. The method according to p. 1, characterized in that the aqueous solution additionally contains a mixture of anionic surfactants of formulas (III) and (IV), while the ratio of the content of ethoxylated alcohol of formula (I) and the total content of anionic surfactants of the formula (III) and (IV) is from 1:10 to 1:1.5.