Pretreatment chemical reagent and method for low-permeability oilfield viscosity-reducing pollution-driving pollution-distribution diluted injection system

Abstract

The invention belongs to the field of chemical flooding recovery efficiency improvement in oilfield development, and discloses a pretreatment chemical reagent and method for a low-permeability oilfield viscosity-reducing pollution-driving pollution-distribution diluted injection system, and the chemical reagent comprises a corrosion inhibition bactericide imidazole quaternary ammonium salt, an acid-base equilibrium agent Na2CO3 and an iron removal agent Na2S2O3. The pretreatment method comprises the following steps: injecting the sewage of the combination station into the water storage tank, adding Na2CO3 and Na2S2O3, stirring for 10 minutes, adding the bactericide, continuously stirring for more than 5 minutes, and finally adding the polymer or the viscosity reduction system. According to the method, the viscosity and the interface performance of an injection system are effectively guaranteed, the test requirements are met, and the cost is low through measurement and calculation.

Description

Technical Field

[0001] The present invention relates to the field of oilfield development chemical flooding to enhance oil recovery, the field of formation water pretreatment before injection, and injection water treatment, so as to ensure the effect of enhancing oil recovery after the injection agent is injected into the formation, and specifically relates to a pretreatment chemical reagent and method for a low permeability oilfield viscosity reduction and pollution drive dilution injection system. Background Art

[0002] Jilin Oilfield has developed medium and low permeability oilfields, which are suitable for viscosity reduction drive test with a potential of 2.0×10 8 t, according to the recovery rate of 10%, the recoverable reserves can be increased by 2000×10 4 t, with great potential for improving oil recovery. The sewage-dilution method is generally used in the implementation of viscosity reduction and flooding projects. The compatibility of sewage from the joint station with the viscosity reduction system directly affects the implementation effect of viscosity reduction and flooding. During the years of development, various measures have been taken in oil and water wells. Although the produced sewage has been sterilized and filtered, there are still problems such as excessive sulfate-reducing bacteria, iron content, and changes in the pH value of the original Na2CO3 type formation water. These problems seriously affect the performance of the injection system during the on-site injection process, especially the viscosity index of the system.

[0003] During the on-site implementation, the polymer system was directly prepared using sewage from the joint station. After 10 days, the viscosity of the polymer system dropped from 72.5 mPa.s to below 17.1 mPa.s, which could not meet the viscosity requirements for on-site injection (see Figure 1 ). After indoor experimental analysis, the wastewater used contained sulfate-reducing bacteria. The corrosion inhibitor and fungicide imidazole quaternary ammonium salt XY-618 (Jilin Petroleum Group Xingye Petrochemical Technology Service Co., Ltd. Enterprise Standard Q / SYJL16018-2019) was used for injection water treatment to remove bacteria and improve the viscosity index. After treatment, the performance of the system was improved, but after 25 days, the viscosity was only 17-19.3 mPa.s, which was still not up to standard (see Figure 2 ).

[0004] Therefore, it is imperative to study a low-cost and efficient pretreatment system and adjust it to meet the needs of viscosity reduction drive tests based on the characteristics of produced water in different regions. Summary of the invention

[0005] In response to the problems that occurred in the field test, such as excessive sulfate-reducing bacteria, hydrogen sulfide, and iron ions in the sewage output from the joint station affecting the performance of the injection system, the present invention conducts research on the injection water pretreatment agent system to ensure that the sewage viscosity reduction system meets the viscosity and interface performance indicators required by the test.

[0006] The technical solution adopted by the present invention to solve its technical problem is:

[0007] A pretreatment chemical reagent for a low-permeability oil field viscosity reduction and pollution drive dilution injection system, comprising corrosion inhibitors and bactericides imidazole quaternary ammonium salts, acid-base balance agent Na2CO3, and iron removal agent Na2S2O3.

[0008] Furthermore, the model of the imidazole quaternary ammonium salt is XY-618.

[0009] Furthermore, the dosage of the imidazole quaternary ammonium salt is 50 to 200 ppm.

[0010] Furthermore, the dosage of Na2CO3 is 350-300 ppm.

[0011] Furthermore, the dosage of Na2S2O3 is 100 to 300 ppm.

[0012] A pretreatment method for a low permeability oil field viscosity reduction and pollution drive with a sewage dilution injection system, wherein sewage from a joint station is injected into a water storage tank, Na2CO3 and Na2S2O3 are added and stirred for 10 minutes, then a fungicide is added and stirred for more than 5 minutes, and finally a polymer or a viscosity reduction system is added.

[0013] Specifically, after adding 200 ppm of Na2CO3 and 200 ppm of Na2S2O3 and stirring for 10 minutes, the imidazole quaternary ammonium salt XY-618 is added and stirring is continued for more than 5 minutes. The best effect is achieved.

[0014] The pH value of sewage is greater than 7, which is conducive to the effectiveness of the above-mentioned pretreatment chemical reagents.

[0015] Compared with the prior art, the present invention has the following beneficial effects:

[0016] (1) Effect of polymer system pretreatment in sewage

[0017] Sewage was injected into a certain area. After the sewage was treated by adding bactericide and alkali, the original viscosity was 78.9mPa.s. After nitrogen sealing treatment, the viscosity remained at 52.3mPa.s after 60 days, which can meet the viscosity index requirements of the polymer system injected on site (see Figure 3 The block injected sewage, after the sewage was treated by adding bactericide and iron remover, the original viscosity was 74.7mPa.s. After nitrogen sealing treatment, the viscosity remained at 71.5mPa.s after 88 days, which can meet the viscosity index requirements of the on-site injection polymer system (see Figure 4 ), and the performance is better than adding alkali alone.

[0018] (2) Effect of pre-treatment in the preparation of a viscosity reduction system for wastewater

[0019] Sewage was injected into a certain block. After the sewage was treated by adding bactericide and iron remover (the viscosity reduction system contained sodium carbonate), the original viscosity was 50.1 mPa.s. After nitrogen sealing treatment, the viscosity remained at 42.7 mPa.s after 31 days. The interfacial tension of the viscosity reduction system was 0.00528 mN / m, which was ultra-low and met the test requirements. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is the viscosity stability evaluation curve of sewage preparation polymer;

[0021] Figure 2 It is the viscosity stability evaluation curve of polymer prepared by adding bactericide to sewage;

[0022] Figure 3 It is the viscosity stability evaluation curve of polymer prepared by sewage, bactericide and alkali;

[0023] Figure 4 It is the viscosity stability evaluation curve of the polymer prepared by sewage, bactericide and iron remover;

[0024] Figure 5 It is the viscosity stability evaluation curve of the viscosity reduction system prepared by adding bactericide and iron remover to sewage;

[0025] Figure 6 It is an evaluation curve of the interfacial tension stability of a viscosity reduction system prepared by adding bactericide and iron remover to sewage. DETAILED DESCRIPTION

[0026] The present invention is described in detail below in conjunction with specific drawings and examples. The examples described below are only preferred embodiments of the present invention. It should be noted that the following description is only for the purpose of explaining the present invention and is not intended to limit the present invention in any form. Any simple modification, equivalent changes and modifications made to the embodiments according to the technical essence of the present invention are within the scope of the technical solution of the present invention. In the following examples, the materials, reagents, etc. used are obtained from commercial sources unless otherwise specified.

[0027] Example 1

[0028] The present invention adopts 50-200 ppm of imidazole quaternary ammonium salt XY-618 (enterprise standard Q / SYJL16018-2019 of Jilin Petroleum Group Xingye Petrochemical Technology Service Co., Ltd.) for water injection treatment as a basic fungicide, and according to the results of indoor experimental analysis, adds acid-base balance agent Na2CO350-300 ppm, iron remover Na2S2O3100-300 ppm (which can remove hydrogen sulfide at the same time), etc.

[0029] In the field implementation, the effect of adding various agents in sequence is better: the sewage from the joint station is injected into the water storage tank, Na2CO3 and Na2S2O3 are added and stirred for 10 minutes, then the fungicide is added and stirred for more than 5 minutes, and finally the polymer or viscosity reduction system is added. According to the above treatment method, the viscosity of the polymer system and the viscosity reduction system is effectively maintained, laying the foundation for the smooth implementation of the chemical flooding project.

[0030] The injected sewage is acidic after testing. The amount of Na2CO3 added is determined by indoor experimental titration. The principle is as follows:

[0031] H + +CO3 2- =CO2+H2O…………………………………………(1)

[0032] After testing, it was found that the sewage contained iron ions, which were removed by adding Na2S2O3. The principle is as follows:

[0033] 2S2O3 2- +2Fe 3+ +H2O=S+2SO4 2- +2Fe 2+ +2H + ……………………(2)

[0034] After gas monitoring, the sewage contains 10-15ppm hydrogen sulfide (H2S), which is removed by adding Na2S2O3. The principle is as follows:

[0035] Na2S2O3+H2S=Na2S+S+SO2+H2O………………………………(3)

[0036] After the above steps, the iron ions Fe in the sewage are removed. 3+ , hydrogen sulfide H2S, so that the pH value of the sewage is greater than 7, which is conducive to the function of the solution.

[0037] Taking a block in Jilin Oilfield as an example, after indoor experimental tests, the block contained sulfate-reducing bacteria, iron, hydrogen sulfide, and acidic sewage in some periods of time. The solution of adding 100ppm of imidazole quaternary ammonium salt XY-618 (Jilin Petroleum Group Xingye Petrochemical Technology Service Co., Ltd. enterprise standard Q / SYJL 16018-2019) for water injection treatment, and adding 200ppm of sodium carbonate Na2CO3 and 200ppm of Na2S2O3 effectively ensured the viscosity and interface performance of the injection system, met the test requirements, and the cost was low after calculation.

[0038] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not limitations on the implementation methods of the present invention. For ordinary technicians in the relevant field, other different forms of changes or modifications can be made based on the above description. It is impossible to list all the implementation methods here. All obvious changes or modifications derived from the technical solution of the present invention are still within the protection scope of the present invention.

Claims

1. A pretreatment chemical reagent for a low permeability oil field viscosity reduction and pollution displacement system, characterized in that: Including corrosion inhibitors and fungicides imidazole quaternary ammonium salts, acid-base balance agent Na2CO3, and iron remover Na2S2O3.

2. The pretreatment chemical reagent for the low permeability oil field viscosity reduction and pollution displacement dilution injection system according to claim 1, characterized in that: The model of the imidazole quaternary ammonium salt is XY-618.

3. The pretreatment chemical reagent for the low permeability oil field viscosity reduction and pollution displacement dilution injection system according to claim 1, characterized in that: The dosage of the imidazole quaternary ammonium salt is 50 to 200 ppm.

4. The pretreatment chemical reagent for the low permeability oil field viscosity reduction and pollution displacement dilution injection system according to claim 1, characterized in that: The dosage of the Na2CO3 is 350-300ppm.

5. The pretreatment chemical reagent for the low permeability oil field viscosity reduction and pollution displacement dilution injection system according to claim 1, characterized in that: The dosage of the Na2S2O3 is 100 to 300 ppm.

6. A pretreatment method for a low permeability oil field viscosity reduction and pollution displacement system, characterized in that: The sewage from the joint station is injected into the water storage tank, and after adding Na2CO3 and Na2S2O3 and stirring for 10 minutes, the fungicide is added and stirring is continued for more than 5 minutes, and finally the polymer or viscosity reduction system is added.

7. The pretreatment method for the low permeability oil field viscosity reduction and pollution displacement dilution injection system according to claim 6, characterized in that: The sewage from the joint station is injected into the water storage tank, and after adding Na2CO3 200ppm and Na2S2O3 200ppm and stirring for 10 minutes, the imidazole quaternary ammonium salt XY-618 is added, and stirring is continued for more than 5 minutes. Finally, the polymer or viscosity reduction system is added.

8. The pretreatment method for the low permeability oil field viscosity reduction and pollution displacement dilution injection system according to claim 6, characterized in that: The pH value of the sewage is adjusted to be greater than 7.

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