WO2022055398A1

WO2022055398A1 - Compositions and methods for processing oil reservoirs

Info

Publication number: WO2022055398A1
Application number: PCT/RU2021/050290
Authority: WO
Inventors: Михаил Викторович ЧЕРНОВ
Original assignee: Общество С Ограниченной Ответственностью "Сансорс Минералс"
Priority date: 2020-09-10
Filing date: 2021-09-08
Publication date: 2022-03-17
Also published as: RU2764968C1

Abstract

The invention relates to the oil-producing industry. A method for extracting oil from an underground reservoir comprises injecting into the reservoir an aqueous composition comprising a non-ionic surfactant and an additional surfactant selected from anionic surfactants of the sulphonate type or amphoteric surfactants. Moreover, the non-ionic surfactant content is between 0.01 and 40.00 wt%, the mass ratio of non-ionic surfactant to additional surfactant is between 1:12 and 1:1.5, and the water in the above-mentioned aqueous composition has up to 250000 mg/l of dissolved salts in total. The technical result is a more efficient effect on a carbonate or terrigenous reservoir in conditions of increased temperature and salinity.

Description

COMPOSITIONS AND METHODS FOR TREATMENT OF OIL RESERVOIRS

More than half of the world's oil reserves are contained in deposits of the carbonate type. The formation characteristics of these fields include fracturedness, low permeability, oil wetness and make oil difficult to recover. This is due to the fact that oil located in the fractures is involved in the displacement process, while the oil contained inside the rock matrix is retained due to negative capillary pressure due to the fact that the porous matrix is wetted with oil (characterized by hydrophobicity).

The present invention relates to the use of substances that improve the degree of recovery of oil from oil reservoirs, preferably carbonate oil reservoirs with low permeability. More precisely, the invention relates to the use of substances that help change the wettability of rocks from oil-wetted to water-wetted and reduce interfacial tension (at the water-oil interface). When using substances of this kind, conditions arise for increasing the degree of oil displacement from the narrowing of the pores of the oil reservoir.

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 oil recovery from carbonate reservoirs. At present, a large number of surfactants have been developed that have the properties of reducing interfacial tension and increasing the wettability of the rock (in the direction of wetted water). However, in some cases, the geological and physical characteristics of oil reservoirs include ¹ factors that affect the effectiveness of the use of such surfactants. These factors include increased reservoir temperature and increased content of salts dissolved in 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 within the framework of enhanced oil recovery.

Various methods of using nonionic surfactants in the recovery of oil from subterranean formations are disclosed, for example, in WO/20 13/110774, RU 2709261, US 9296942, US 3799264 and US 4276933. The references suggest the use of ethoxylated alcohols, the number of ethylene oxide groups in which is not exceeds 70. It should be noted that, depending on the conditions for obtaining ethoxylated alcohols, the number of ethylene oxide groups can change and determine the physicochemical properties of these 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-oil) and ensuring spontaneous imbibition (into the rock matrix), which leads to higher degrees of displacement. The use of these substances under these conditions is significant for the oil and gas industry and makes it possible to achieve higher oil recovery rates.

In connection with the foregoing, the object of the present invention is the use of non-ionic surfactants of formula (I) for the recovery of oil from reservoirs

where n is a number from 82 to 87,

Ri is a hydrocarbon group containing 12 to 14 carbon atoms.

At the same time, the HLB (Griffin hydrophilic-lipophilic balance) of the specified nonionic surfactant has a value of more than 18.8.

The proposed non-ionic surfactants are eth'oxylated 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 hydrophilicity 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 oil 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%.

It is known in the art to describe the ability of ethoxylated alcohols to stabilize oil-in-water emulsions by using the HLB index. HLB value for ethoxylated alcohols in this application is usually a number from 5.0 to 18.8. High HLB surfactants are dominated by hydrophilic parts of the molecules, which characterizes these substances as good emulsifiers for oil-in-water emulsions.

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-oil 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.

The present ethoxylated alcohols have improved solubilization properties of anionic surfactants and amphoteric surfactants compared to those of ethoxylated alcohols with a low ethoxy group count (ethoxy group count less than 82).

Another object of the present invention is also a method for increasing the degree of oil recovery from reservoirs, including the preparation of an aqueous or saline solution containing a nonionic surfactant indicated 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. At the same time, within the framework of the use of a nonionic surfactant as a co-solvent in in these solutions, a liquid hydrocarbon containing from 6 to 30 carbon atoms can act.

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 oil captured by the skeleton of the rock constituting preferably carbonate formations leads to an increase in the 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-oil interface at elevated temperature.

These methods are simple and effective for evaluating the effectiveness of applied non-ionic surface active substances (ethoxylated alcohols).

The first method is based on the properties of ethoxylated alcohols to create m: and roe mulsie, 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. At the same time: the content of compositions of surfactants (including ethoxylated alcohols and additional surfactants) in solution is 0.1% wt. 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 with a content of 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 honeydew using an aqueous solution with a dissolved salt content of 250,000 mg/l.

The second test measures the interfacial tension. Measurements are taken to evaluate the surface properties of solutions, using solutions that have shown a positive result in test No. 1. The test uses a series of thermostated solutions (in test no. 1) and crude oil with a density of 0.820 kg/l (paraffin content 14%). 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. Teslas 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 in the framework of test No. 2, since the solutions that did not pass the Y test; 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. I Evaluation of the stability of compositions at an increased content of dissolved salts and elevated temperature. The test was carried out in two stages. but. 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 number of ethoxylated alcohols) and additional surfactants. When preparing these solutions, water with a content of dissolved salts of 100,000 mg/l was used. Temperature control 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. In the preparation of these solutions, water with a content of dissolved salts of 250,000 mg/l was used. Temperature control of these solutions was carried out at a temperature of -- 74 °C.

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

The measurements were carried out for compositions that showed good results, within the framework of stages a and b of test No. 1. A 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. I.

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.

Examples 23-27 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

Claims

CLAIM

1. A method for extracting oil from an underground reservoir, including injection into the reservoir of an aqueous solution of a nonionic surfactant - ethoxylated snirg, and extracting oil from an underground reservoir, characterized in that ethoxylated alcohol of general formula (I) is used

(I) where n is: a number from 82 to 87;

Ri is a hydrocarbon group containing 12 to 14 carbon atoms; the hydrophilic-lipophilic HLB balance of said ethoxylated alcohol is greater than 18.8; while water in aqueous solution has a total amount of dissolved salts up to 250,000 mg/l; and the content of ethoxylated alcohol of formula (I) in solution is from 0.01 to 40.00 wt%.

2. Method according to and. 1, characterized in that the aqueous solution additionally contains an amphoteric surfactant of general formula (II) SN ₃

R ₂ - N ⁺ -CH ₂ -CH - CH ₂ - SO ₃ - CH ₃ he

(II) where R2 is a hydrocarbon group containing from 12 to 14 carbon atoms; while the mass ratio of the ethoxylated alcohol of formula (I) and the substance of formula (11) is from 1:12 to 1

3. The method according to p. 1, characterized in that the aqueous solution additionally contains an anionic surfactant of the sulfonate type of general formula (III)

(III) where R3 represents a hydrocarbon group containing from 12 to 14 carbon atoms; the mass ratio of the ethoxylated alcohol of formula (D) and the substance 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 R4 represents a hydrocarbon group containing from 10 to 12 carbon atoms; while the mass ratio of ethoxylated alcohol of formula (I) and the substance 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 the general formula

where R.3 represents: a hydrocarbon group containing from 12 to 14 carbon atoms; and the general formula

(IV) where ID is a hydrocarbon group containing from 10 to 12 carbon atoms; at the same time: the mass ratio of the content of ethoxylated alcohol of formula (I) and the total content of anionic surfactants of formula (III) and (IV) is from 1:10 to 1: 1.5.