Rigid group-containing high-temperature-resistant clay stabilizer and preparation method thereof

Abstract

According to the rigid group-containing high-temperature-resistant clay stabilizer and the preparation method thereof provided by the invention, the structure of the rigid group-containing high-temperature-resistant clay stabilizer contains rigid benzene rings, polyether chain segments, multi-amide groups and ammonium ions, and the rigid group-containing high-temperature-resistant clay stabilizer has the advantages of good temperature resistance, excellent anti-swelling effect, strong adsorbability, good washing resistance and the like. The anti-swelling rate of the high-temperature-resistant clay stabilizer containing the rigid groups reaches 90% or above, the shrinkage-swelling rate reaches 50% or above, the temperature resistance reaches 300 DEG C, the washing resistance reaches 100%, the core permeability retention value reaches 90% or above, and the high-temperature-resistant clay stabilizer can be used for water injection swelling prevention, acid fracturing swelling prevention and heavy oil thermal recovery swelling prevention of oil fields.

Description

Technical Field

[0001] The invention relates to a high temperature resistant clay stabilizer and a preparation method thereof, belonging to the technical field of petroleum engineering. Background Art

[0002] Clay minerals are widely present in oil layers. 97% of the oil layers in the world contain clay minerals to varying degrees. Generally, when the oil reservoir contains 5% to 20% clay, it is considered to be an oil layer with a high clay content. In the process of oil field development (water injection, acidification, fracturing), if the measures are inappropriate, these clays will swell, disperse, and migrate when they encounter external water or water-based substances. During the expansion process, the clay absorbs water into the crystal structure, resulting in an increase in the volume of the clay, thereby blocking the pores of the formation; during the migration process, the clay material is dispersed by external liquids or carried by the produced fluid, forming a bridge or throttling point at the pore throat of the capillary, blocking the pore roar, causing the formation permeability to decrease, and the damage to low-permeability oil reservoirs is more serious. Therefore, for reservoirs with high clay content and strong water sensitivity, any process measures such as drilling, cementing, water injection, fracturing, acidizing, well repair and well pressure, as long as there is intrusion of water-based working fluid, it is possible to cause water-sensitive damage. The most common method to solve water-sensitive damage is to add clay stabilizer to the injected water. Therefore, the research and development and use of high-quality and efficient anti-swelling agents are important measures to ensure stable production of oil fields.

[0003] With the continuous deepening of oil resource exploration, the burial depth of oil reservoirs continues to increase, the temperature of oil reservoirs continues to rise, and the temperature resistance of chemical treatment agents used in oil and gas well operations continues to improve. At present, commonly used clay stabilizers are widely used to protect the permeability of formations in shallow areas, and the temperature resistance is generally below 200℃. Analysis shows that there are two main possibilities for their insufficient temperature resistance. One is that the thermal stability of the treatment agent itself is insufficient, and it decomposes at high temperatures and cannot play an anti-swelling role; the other is that the adsorption of the treatment agent with clay is weakened at high temperatures, and it cannot form effective adsorption inside the clay, resulting in poor effect. Summary of the invention

[0004] The present invention provides a high temperature resistant clay stabilizer containing a rigid group and a preparation method thereof. Firstly, by introducing a benzene ring into the molecular main chain structure of the clay stabilizer, due to the ring structure and π bond characteristics of the benzene ring (carbon-carbon double bond strength>carbon-carbon single bond strength), the chemical bond strength of the polymer main chain is increased, and the thermal stability of the clay stabilizer itself can be further improved; secondly, the molecular structure of the high temperature resistant clay stabilizer containing a rigid group contains multiple amide groups and ammonium ions, and the adsorption force with the formation is strong, so that the stabilizer can still be used under high temperature conditions. It is adsorbed inside the clay to play an anti-swelling role; thirdly, its molecular main chain structure contains polyether chains and benzene ring structures. After it is adsorbed inside the clay, the hydrophobicity of the polyether chains and benzene ring structures can not only drive away the water molecules that have entered the clay flakes, but also prevent external water molecules from entering the clay again, which is beneficial to improving the anti-swelling performance; fourthly, because its structure contains multiple amide groups and ammonium ions, it can be adsorbed on the hydrated and dispersed clay flakes, and can pull the hydrated and dispersed flakes closer and tighten them, which has a shrinking and swelling effect.

[0005] The present invention achieves the above-mentioned purpose through the following technical solutions.

[0006] The present invention provides a high temperature resistant clay stabilizer containing a rigid group, which is characterized in that the main chain of the high temperature resistant clay stabilizer molecule contains a polyether segment, a rigid benzene ring group, and an amide group and an ammonium ion that can be strongly adsorbed in the formation, and the general structural formula is one of the following three: Wherein, R1 and R2 are hydrogen or methyl; R3 is hydrogen, methyl, ethyl, propyl, phenyl or benzyl; and n is 2-8.

[0007] The present invention also provides a method for preparing a high temperature resistant clay stabilizer containing a rigid group, characterized in that the preparation steps are: (1) A dibasic acid containing a rigid group and a diamine containing a polyether segment are used as raw materials to react to generate an intermediate product with the following general structural formula: Wherein, R1 and R2 are hydrogen or methyl; n is 2-8; (2) Adding an organic acid to the intermediate product generated in step (1) and adjusting the pH value to obtain a high temperature resistant clay stabilizer containing a rigid group.

[0008] The dibasic acid containing a rigid group is phthalic acid, isophthalic acid or terephthalic acid.

[0009] The general structural formula of the diamine containing polyether chain segment is: Wherein, R1 and R2 are hydrogen or methyl; n is 2-8.

[0010] The organic acid is formic acid, acetic acid, propionic acid, butyric acid, benzoic acid or phenylacetic acid.

[0011] The molar ratio of the dibasic acid containing a rigid group to the diamine containing a polyether segment is 1:2.05-1:5.

[0012] The reaction step (1) is specifically as follows: adding the diamine containing a polyether segment into a reactor, starting stirring, and introducing nitrogen for protection throughout the process, then starting heating, and maintaining a constant temperature when the temperature rises to 160° C.; dissolving the dibasic acid containing a rigid group with a dispersant, and then starting to dropwise add a dispersant solution containing the dibasic acid containing a rigid group, and after the dropwise addition is complete, continuing to heat to 180° C., maintaining this temperature until no more water is removed, continuing the reaction for 30 min, then stopping the reaction, and cooling.

[0013] The dispersant is methanol, ethanol or acetone.

[0014] In the reaction step (2), the pH value is adjusted to 7-9.

[0015] The high temperature resistant clay stabilizer containing rigid groups can be used for water injection and anti-swelling in oil fields, acid fracturing and anti-swelling in heavy oil thermal recovery.

[0016] The heat-resistant clay stabilizer provided by the present invention has enhanced thermal stability by introducing a rigid group of a benzene ring, and the treating agent has a significant heat-resistant effect, and the heat-resistant capacity reaches 300°C; the hydrophobic properties of the benzene ring and the polyether chain are utilized to better inhibit the hydration expansion of the clay, and the treating agent has good anti-swelling and shrinkage properties, with an anti-swelling rate of more than 90% and a shrinkage rate of more than 50%; and the structure contains multiple amide groups and ammonium ions, so that the adsorption performance at high temperature is enhanced, the water wash resistance of the treating agent reaches 100%, and the core permeability retention value reaches more than 90%. Implementation

[0017] The present invention is described in detail below with reference to embodiments and comparative examples. Example

[0018] Reaction step (1): The structure of the diamine containing a polyether segment is selected as follows:

[0019] Wherein R1 and R2 are both methyl groups; n is 3.

[0020] Weigh 0.3 mol of a diamine containing a polyether segment into a flask, start stirring, introduce nitrogen gas for protection throughout the process, and then start heating; when the temperature rises to 160°C, keep the temperature constant.

[0021] Weigh 0.1 mol of terephthalic acid and dissolve it in methanol, then transfer it to the dropping funnel, and then begin to drop the methanol solution containing terephthalic acid into the flask. After the dropwise addition is complete, continue to heat up to 180°C and react until no more water is removed. Then react for 30 minutes, then stop the reaction and cool down.

[0022] Reaction step (2): add 0.4 mol of formic acid to the reaction product obtained in step (1) and control the pH value to 7. Example

[0023] Reaction step (1): The structure of the diamine containing a polyether segment is selected as follows:

[0024] Wherein R1 and R2 are both methyl groups; n is 5.

[0025] 0.205 mol of a diamine containing a polyether segment was weighed and added into a flask. Stirring was started and nitrogen was introduced throughout the process for protection. Then heating was started. When the temperature reached 160° C., the temperature was kept constant.

[0026] Weigh 0.1 mol of isophthalic acid and dissolve it in methanol, then transfer it to the dropping funnel, and then start adding the methanol solution containing isophthalic acid to the flask. After the addition is complete, continue to heat up to 180°C and react until no more water is removed. Then react for 30 minutes, then stop the reaction and cool down.

[0027] Reaction step (2): add 0.21 mol of benzoic acid to the reaction product obtained in step (1) and control the pH value to 7. Example

[0028] Reaction step (1): The structure of the diamine containing a polyether segment is selected as follows:

[0029] Wherein R1 and R2 are both methyl groups; n is 8.

[0030] Weigh 0.5 mol of a diamine containing a polyether segment into a flask, start stirring, introduce nitrogen gas for protection throughout the process, and then start heating; when the temperature rises to 160°C, keep the temperature constant.

[0031] Weigh 0.1 mol of phthalic acid and dissolve it in methanol, then transfer it to the dropping funnel, and then begin to drop the methanol solution containing phthalic acid into the flask. After the dropwise addition is complete, continue to heat up to 180°C and react until no more water is removed. Then react for 30 min, then stop the reaction and cool down.

[0032] Reaction step (2): add 0.8 mol of acetic acid to the reaction product obtained in step (1) and control the pH value to 7. Example

[0033] Reaction step (1): The structure of the diamine containing a polyether segment is selected as follows:

[0034] Wherein R1 and R2 are both methyl groups; n is 5.

[0035] 0.205 mol of a diamine containing a polyether segment was weighed and added into a flask. Stirring was started and nitrogen was introduced throughout the process for protection. Then heating was started. When the temperature reached 160° C., the temperature was kept constant.

[0036] Weigh 0.1 mol of terephthalic acid and dissolve it in methanol, then transfer it to the dropping funnel, and then begin to drop the methanol solution containing terephthalic acid into the flask. After the dropwise addition is complete, continue to heat up to 180°C and react until no more water is removed. Then react for 30 minutes, then stop the reaction and cool down.

[0037] Reaction step (2): add 0.205 mol of benzoic acid to the reaction product obtained in step (1) and control the pH value to 9.

[0038] Example 5 Reaction step (1): The structure of the diamine containing a polyether segment is selected as follows:

[0039] Wherein R1 and R2 are both methyl groups; n is 5.

[0040] 0.205 mol of a diamine containing a polyether segment was weighed and added into a flask. Stirring was started and nitrogen was introduced throughout the process for protection. Then heating was started. When the temperature reached 160° C., the temperature was kept constant.

[0041] Weigh 0.1 mol of isophthalic acid and dissolve it in methanol, then transfer it to the dropping funnel, and then start adding the methanol solution containing isophthalic acid to the flask. After the addition is complete, continue to heat up to 180°C and react until no more water is removed. Then react for 30 minutes, then stop the reaction and cool down.

[0042] Reaction step (2): add 0.208 mol of benzoic acid to the reaction product obtained in step (1) and control the pH value to 8.

[0043] Example 6 Reaction step (1): The structure of the diamine containing a polyether segment is selected as follows:

[0044] Wherein R1 is methyl, R2 is hydrogen; and n is 3.

[0045] Weigh 0.3 mol of a diamine containing a polyether segment into a flask, start stirring, introduce nitrogen gas for protection throughout the process, and then start heating; when the temperature rises to 160°C, keep the temperature constant.

[0046] Weigh 0.1 mol of phthalic acid and dissolve it in methanol, then transfer it to the dropping funnel, and then begin to drop the methanol solution containing phthalic acid into the flask. After the dropwise addition is complete, continue to heat up to 180°C and react until no more water is removed. Then react for 30 min, then stop the reaction and cool down.

[0047] Reaction step (2): add 0.4 mol of formic acid to the reaction product obtained in step (1) and control the pH value to 7.

[0048] Example 7 Reaction step (1): The structure of the diamine containing a polyether segment is selected as follows:

[0049] Among them, R1 is hydrogen, R2 is methyl; and n is 3.

[0050] Weigh 0.3 mol of a diamine containing a polyether segment into a flask, start stirring, introduce nitrogen gas for protection throughout the process, and then start heating; when the temperature rises to 160°C, keep the temperature constant.

[0051] Weigh 0.1 mol of terephthalic acid and dissolve it in methanol, then transfer it to the dropping funnel, and then begin to drop the methanol solution containing terephthalic acid into the flask. After the dropwise addition is complete, continue to heat up to 180°C and react until no more water is removed. Then react for 30 minutes, then stop the reaction and cool down.

[0052] Reaction step (2): add 0.4 mol of formic acid to the reaction product obtained in step (1) and control the pH value to 7.

[0053] Example 8 Reaction step (1): The structure of the diamine containing a polyether segment is selected as follows:

[0054] Wherein R1 is methyl, R2 is hydrogen; and n is 2.

[0055] Weigh 0.25 mol of a diamine containing a polyether segment into a flask, start stirring, introduce nitrogen gas for protection throughout the process, and then start heating; when the temperature rises to 160°C, maintain a constant temperature.

[0056] Weigh 0.1 mol of isophthalic acid and dissolve it in ethanol, then transfer it to the dropping funnel, and then begin to drop the ethanol solution containing isophthalic acid into the flask. After the addition is complete, continue to heat up to 180°C and react until no more water is removed. Then react for 30 minutes, then stop the reaction and cool down.

[0057] Reaction step (2): add 0.3 mol of butyric acid to the reaction product obtained in step (1) and control the pH value to 7.

[0058] Example 9 Reaction step (1): The structure of the diamine containing a polyether segment is selected as follows:

[0059] Wherein R1 and R2 are both hydrogen; n is 7.

[0060] Weigh 0.4 mol of a diamine containing a polyether segment into a flask, start stirring, introduce nitrogen gas for protection throughout the process, and then start heating; when the temperature rises to 160°C, keep the temperature constant.

[0061] Weigh 0.1 mol of phthalic acid and dissolve it in acetone, then transfer it to the dropping funnel, and then begin to drop the acetone solution containing phthalic acid into the flask. After the dropwise addition is complete, continue to heat up to 180°C and react until no more water is removed. Then react for 30 min, then stop the reaction and cool down.

[0062] Reaction step (2): add 0.6 mol of phenylacetic acid to the reaction product obtained in step (1) and control the pH value to 7.

[0063] Comparative Example 1 Reaction step (1): The structure of the diamine containing a polyether segment is selected as follows:

[0064] Wherein R1 and R2 are both methyl groups; n is 5.

[0065] Weigh 0.15 mol of a diamine containing a polyether segment into a flask, start stirring, introduce nitrogen gas for protection throughout the process, and then start heating; when the temperature rises to 160°C, keep the temperature constant.

[0066] Weigh 0.1 mol of isophthalic acid and dissolve it in methanol, then transfer it to the dropping funnel, and then start adding the methanol solution containing isophthalic acid to the flask. After the addition is complete, continue to heat up to 180°C and react until no more water is removed. Then react for 30 minutes, then stop the reaction and cool down.

[0067] Reaction step (2): add 0.1 mol of benzoic acid to the reaction product obtained in step (1) and control the pH value to 7.

[0068] Comparative Example 2 Isophthalic acid is not introduced in Example 2. 0.15 mol of a diamine containing a polyether segment is weighed and added to a flask, and then 0.3 mol of benzoic acid is added, and the pH value is controlled to be 7.

[0069] Comparative Example 3 Reaction step (1): Weigh 0.5 mol of 1,2-propylenediamine and add it into a flask, start stirring, and introduce nitrogen gas for protection throughout the process, then start heating; when the temperature rises to 160°C, keep the temperature constant.

[0070] Weigh 0.1 mol of phthalic acid and dissolve it in methanol, then transfer it to the dropping funnel, and then begin to drop the methanol solution containing phthalic acid into the flask. After the dropwise addition is complete, continue to heat up to 180°C and react until no more water is removed. Then react for 30 min, then stop the reaction and cool down.

[0071] Reaction step (2): add 0.8 mol of acetic acid to the reaction product obtained in step (1) and control the pH value to 7.

[0072] Comparative Example 4 Reaction step (1): The structure of the diamine containing a polyether segment is selected as follows:

[0073] Wherein R1 and R2 are both methyl groups; n is 5.

[0074] 0.205 mol of a diamine containing a polyether segment was weighed and added into a flask. Stirring was started and nitrogen was introduced throughout the process for protection. Then heating was started. When the temperature reached 160° C., the temperature was kept constant.

[0075] Weigh 0.1 mol of isophthalic acid and dissolve it in methanol, then transfer it to the dropping funnel, and then start adding the methanol solution containing isophthalic acid to the flask. After the addition is complete, continue to heat up to 180°C and react until no more water is removed. Then react for 30 minutes, then stop the reaction and cool down.

[0076] The reaction step (2) of adjusting the pH value is no longer performed, and the product obtained in the reaction step (1) is directly used as a clay stabilizer sample.

[0077] Test Example 1 The anti-swelling rate test was carried out according to the "SY / T5971-2016 Performance Evaluation Method of Clay Stabilizer for Water Injection", and the steps are as follows: weigh 0.5 g of sodium bentonite, add it to a 10 mL centrifuge tube, add deionized water to the 10 mL mark, shake it thoroughly, let it stand at room temperature for 2 hours, put it into a centrifuge, centrifuge it at a speed of 1500 r / min for 15 minutes, and read the volume V2 of sodium bentonite in water. Use the same steps to replace the clean water with a certain concentration of clay stabilizer aqueous solution, and measure the volume V1 of the soil after centrifugation. Use kerosene instead of water to measure the volume V0 of the soil.

[0078]

[0079] In the formula: η—anti-swelling rate, %; V0—volume of sodium bentonite in kerosene, mL; V1—volume of sodium bentonite in clay stabilizer, mL; V2—volume of sodium bentonite in clean water, mL.

[0080] Test Example 2 The anti-swelling rate test steps after aging at 300°C are as follows: (1) Weigh 3.00 g of bentonite powder, accurate to 0.01 g, and load it into a high temperature and high pressure closed reactor; (2) Add 60 mL of 4% clay stabilizer solution, shake well to mix, place in an oven at 300±2℃ for 24 h, and cool to room temperature; (3) Transfer all the clay mixture in the high-temperature and high-pressure closed reactor into a 100 mL beaker, shake it thoroughly, quickly take out 10 mL and add it to a glass centrifuge tube, put it into a centrifuge with automatic balancing function, centrifuge it at 1500 r / min for 15 min, and read the expansion volume V1 of the bentonite. The anti-swelling rate calculation formula is as follows:

[0081] Where: V0 is the expansion volume of bentonite in kerosene; V1 is the expansion volume of bentonite in clay stabilizer aqueous solution; V2 is the expansion volume of bentonite in clean water; Test Example 3 The steps for testing washability are as follows: Pour out the supernatant in the centrifuge tube after centrifugation in the above test example 2, add deionized water to 10 mL, stir thoroughly, let stand for 2 hours, and then centrifuge at 1500 r / min for 15 minutes in a centrifuge. Finally, read the final volume V1 of the bentonite in the centrifuge tube. ′ .

[0082] Washability calculation formula:

[0083] Where: V1 is the expansion volume of bentonite in clay stabilizer aqueous solution, mL; V1 ′ V is the expansion volume of bentonite after washing, mL; V2 is the expansion volume of bentonite in clean water, mL.

[0084] Test Example 4 The shrinkage and expansion rate test steps are as follows: Weigh 0.5 g of sodium bentonite, add it to a 10 mL centrifuge tube, add deionized water to the 10 mL mark, shake it thoroughly, let it stand at room temperature for 2 h, put it into a centrifuge, centrifuge it at 1500 r / min for 15 min, and read the volume V2 of sodium bentonite in water. Pour out the clean water, add a certain concentration of clay stabilizer aqueous solution to the expanded bentonite instead of the clean water, and measure the volume V1 of the soil after centrifugation. Use kerosene instead of water to measure the volume V0 of the soil.

[0085]

[0086] In the formula: η—anti-swelling rate, %; V0—volume of sodium bentonite in kerosene, mL; V1—volume of sodium bentonite in clay stabilizer after expansion, mL; V2—volume of sodium bentonite in clean water, mL.

[0087] Test Example 5 The core displacement test was used to test the original core permeability K0, and then the core was saturated with simulated formation water. The clay stabilizer solution system was injected into the core tube at 300°C, and then high-temperature steam at 300°C was injected. Finally, the permeability K1 of the core after the experiment was tested. K1 / K0 is the core permeability retention value.

[0088] Table 1 Sample evaluation results Anti-expansion rate at room temperature, % Anti-swelling rate after aging at 300℃, % Shrinkage rate, % Washing resistance, % Core permeability retention value, % Remark Example 1 93.9 91.5 51.6 100 91.6 Example 2 94.3 92.2 52.4 100 92.0 Example 3 95.7 92.8 53.9 100 93.5 Example 4 91.7 90.8 50.6 100 90.8 Example 5 92.5 91.2 51.0 100 91.2 Example 6 93.7 91.5 51.5 100 91.8 Example 7 90.7 90.3 50.1 100 90.3 Example 8 93.6 92.0 52.1 100 91.7 Example 9 94.5 92.4 52.7 100 92.5 Comparative Example 1 — — — — — Not water soluble, cannot be tested Comparative Example 2 92.1 78.2 51.6 100 76.1 Comparative Example 3 84.1 82.8 44.9 100 78.5 Comparative Example 4 86.5 85.3 45.7 98.7 86.1 blank 12.3

Claims

1. A high temperature resistant clay stabilizer containing a rigid group, characterized in that The structure is as follows: The main chain of the high temperature resistant clay stabilizer molecule contains polyether segments, rigid benzene ring groups, and amide groups and ammonium ions that can be strongly adsorbed in the formation. Its general structural formula is one of the following three: Wherein, R1 and R2 are hydrogen or methyl; R3 is hydrogen, methyl, ethyl, propyl, phenyl or benzyl; and n is 2-8.

2. A method for preparing a high temperature resistant clay stabilizer containing a rigid group, characterized in that The preparation steps are: (1) A dibasic acid containing a rigid group and a diamine containing a polyether segment are used as raw materials to react to generate an intermediate product with the following general structural formula: Wherein, R1 and R2 are hydrogen or methyl; n is 2-8; (2) Adding an organic acid to the intermediate product produced in step (1) and adjusting the pH value to obtain a high temperature resistant clay stabilizer containing a rigid group.

3. The method for preparing a high temperature resistant clay stabilizer containing a rigid group as claimed in claim 2, characterized in that: The dibasic acid containing a rigid group is phthalic acid, isophthalic acid or terephthalic acid.

4. The method for preparing a high temperature resistant clay stabilizer containing a rigid group as claimed in claim 2, characterized in that: The general structural formula of the diamine containing polyether chain segment is: Wherein, R1 and R2 are hydrogen or methyl; n is 2-8.

5. The method for preparing a high temperature resistant clay stabilizer containing a rigid group as claimed in claim 2, characterized in that: The organic acid is formic acid, acetic acid, propionic acid, butyric acid, benzoic acid or phenylacetic acid.

6. The method for preparing a high temperature resistant clay stabilizer containing a rigid group as claimed in claim 2, characterized in that: The molar ratio of the dibasic acid containing a rigid group to the diamine containing a polyether segment is 1:2.05-1:

5.

7. The method for preparing a high temperature resistant clay stabilizer containing a rigid group as claimed in claim 2, characterized in that: The reaction step (1) is specifically as follows: adding the diamine containing a polyether chain segment into a reactor, starting stirring, and introducing nitrogen for protection throughout the process, then starting heating, and maintaining a constant temperature when the temperature rises to 160° C.; dissolving the dibasic acid containing a rigid group with a dispersant, and then starting to dropwise add a dispersant solution containing the dibasic acid containing a rigid group, and after the dropwise addition is complete, continuing to heat to 180° C., maintaining this temperature until no more water is removed, continuing the reaction for 30 min, then stopping the reaction and cooling.

8. The method for preparing a high temperature resistant clay stabilizer containing a rigid group as claimed in claim 7, characterized in that: The dispersant is methanol, ethanol or acetone.

9. The method for preparing a high temperature resistant clay stabilizer containing a rigid group as claimed in claim 2, characterized in that: In the reaction step (2), the pH value is adjusted to 7-9.

10. The high temperature resistant clay stabilizer containing a rigid group as claimed in claim 1, characterized in that The high temperature resistant clay stabilizer containing rigid groups is used for water injection and anti-swelling in oil fields, acid fracturing and anti-swelling in heavy oil thermal recovery.

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