High-temperature resistant invisible acid completion fluid, preparation method and application thereof

Abstract

The application discloses a high-temperature resistant invisible acid completion fluid and a preparation method and application thereof. The high-temperature resistant invisible acid completion fluid comprises high-temperature invisible acid, high-temperature anti-swelling agent and high-temperature corrosion inhibitor. The high-temperature resistant invisible acid completion fluid has a rock debris corrosion rate greater than 5% at 140 DEG C, a corrosion rate less than 0.06 mm / a, an anti-swelling rate greater than 89%, and a core permeability recovery value greater than 115%. The preparation method comprises sequentially adding the high-temperature invisible acid, the high-temperature anti-swelling agent and the high-temperature corrosion inhibitor in a formula amount into fresh water, stirring and dissolving, and adjusting the density to obtain the high-temperature resistant invisible acid completion fluid. The high-temperature resistant invisible acid completion fluid has excellent effects of dissolving inorganic scale and organic matters and appropriately dissolving stratum minerals at high temperature, can effectively dredge the near-wellbore channel, and plays a role in improving the oil layer permeability. In addition, the completion fluid has the advantages of strong inhibition, low corrosion rate, good compatibility and reservoir protection effect.

Description

Technical Field

[0001] This invention relates to the field of oil reservoir development technology, specifically to a high-temperature resistant, stealthy acid completion fluid, its preparation method, and its application. Background Technology

[0002] The clastic and carbonate reservoirs in the Tarim Oilfield are characterized by deep burial (greater than 5000 meters), high temperature (120-140℃), and high formation water salinity (210-240 g / L). Commonly used completion fluids in field completion operations, such as solid-free clean brine completion fluids and low-solids temporary plugging completion fluids, are poorly suited to the Tarim clastic and carbonate rocks, easily leading to severe reservoir damage. Therefore, researching high-performance completion fluids suitable for the high-temperature, high-salinity reservoirs of the Tarim is of paramount importance for the efficient development of these reservoirs.

[0003] Compared to conventional completion fluids, stealth acid completion fluids offer advantages such as dissolving organic matter, inorganic scale, and mud cake, and clearing oil reservoir channels near the wellbore, thus improving reservoir permeability to a certain extent. The research and application of this technology is of great significance for reservoir protection during well completion operations. However, the high-temperature and high-salinity characteristics of the Tarim Basin clastic and carbonate reservoirs reduce the effectiveness of stealth acid completion fluids in field applications.

[0004] CN1660957A discloses a stealthy acid chelating completion fluid, composed of clay stabilizer, inorganic salt, stealthy acid, bactericide, and aqueous solution. This completion fluid can alter the environment in which high-valence metal ions exist, preventing the formation of various organic scale and inorganic precipitates. It can also remove organic scale and inorganic precipitates formed in the previous working fluid, and dissolve macromolecules, solid particles, and acid-soluble reservoir minerals near the wellbore, thereby protecting and improving the reservoir and increasing production efficiency. However, the invention does not specify the operating temperature of the stealthy acid completion fluid. Furthermore, the stealthy acid used in this completion fluid is hydrofluoric acid, which is highly acidic and can cause severe corrosion to downhole tools at high temperatures.

[0005] Reference 1 (Wang Qingyu, Xu Jingsheng, Lü Kaihe, et al. Offensive stealth acid completion fluid technology for improving reservoirs [J]. Offshore Oil, 2009, 29(2):55-59) developed an offensive stealth acid completion fluid for improving reservoirs. This completion fluid has advantages such as lowering pH value, eliminating inorganic and organic precipitation, providing temporary shielding and plugging, dissolving cores, and improving reservoirs. Field test results in the QK17-2 oilfield of Bohai Sea show that this stealth acid completion fluid can improve reservoir permeability and increase oilfield productivity. However, the operating temperature of this stealth acid completion fluid is 80℃, making it difficult to apply to high-temperature formations.

[0006] Reference 2 (Xia Yulong, Zhou Sihong. Research and application of stealth acid completion fluid system in Chengdao Oilfield [J]. Oilfield Chemistry, 2010(1):7-11) developed a stealth acid carrier containing H+ release and various functional additives, and further constructed a stealth acid completion fluid system. This stealth acid completion fluid was field-tested in the perforation completion of four new wells in the Chengdao Oilfield. After production, the oil yield was significantly higher than that of four control wells that used waterproof and damaging completion fluid for perforation completion. However, the operating temperature of this stealth acid completion fluid is 60℃, making it difficult to apply to high-temperature formations.

[0007] In summary, existing stealth acid completion fluids have the following main shortcomings: poor temperature resistance and strong corrosiveness. Their applicability to the high-temperature, high-salinity reservoirs of the Tarim River needs further improvement, and there is still considerable room for improvement in both technology and performance. Therefore, developing a stealth acid completion fluid suitable for the characteristics of deep clastic and carbonate high-temperature, high-salinity reservoirs in the Tarim River is of great significance for efficient reservoir protection during well completion operations, and this is a key problem that urgently needs to be solved in this field. Summary of the Invention

[0008] To address the aforementioned technical problems, this invention proposes a high-temperature resistant, stealthy acid completion fluid, its preparation method, and its application.

[0009] To achieve the above objectives, the present invention adopts the following technical solution:

[0010] A high-temperature resistant stealth acid completion fluid includes high-temperature stealth acid, high-temperature anti-swelling agent, and high-temperature corrosion inhibitor.

[0011] The high-temperature resistant, stealthy acid completion fluid of this invention exhibits a cuttings dissolution rate of greater than 5% and a corrosion rate of less than 0.06 mm / a at 140℃, an anti-swelling rate of greater than 89%, and a core permeability recovery value of greater than 115%.

[0012] The high-temperature hidden acid in this invention is at least one of citric acid, sodium citrate, oxalic acid, phosphoric acid, and hydrofluoric acid.

[0013] The high-temperature anti-swelling agent in this invention is at least one of cationic polyacrylamide, polyquaternary ammonium salt compound, choline chloride clay inhibitor, potassium chloride and small cationic clay inhibitor.

[0014] The high-temperature corrosion inhibitor in this invention is at least one or two of the following: imidazoline quaternary ammonium salts, imidazoline compounds, phosphonates, thiourea, sodium thiosulfate, and ascorbic acid.

[0015] In some preferred embodiments, the high-temperature stealth acid-resistant completion fluid comprises, by weight, 2.2-2.5 parts of high-temperature stealth acid, 4-6 parts of high-temperature anti-swelling agent, and 3-6 parts of high-temperature corrosion inhibitor.

[0016] The density of the high-temperature resistant, stealthy acid completion fluid in this invention is 1.10-1.80 g / cm³. 3 In some embodiments, a weighting agent may be selectively added to adjust the density of the completion fluid. The weighting agent is one or both of inorganic and organic salts, wherein the inorganic salts include sodium chloride, potassium chloride, calcium chloride, and calcium bromide, and the organic salts include sodium formate, cesium formate, and potassium formate.

[0017] The high-temperature resistant, stealthy acid completion fluid of this invention can also be supplemented with bactericides.

[0018] The present invention also provides a method for preparing the above-mentioned high-temperature resistant stealth acid completion fluid, comprising the following steps: adding the formulated amounts of high-temperature stealth acid, high-temperature anti-swelling agent and high-temperature corrosion inhibitor to fresh water in sequence, stirring to dissolve, adjusting the density, and obtaining the high-temperature resistant stealth acid completion fluid.

[0019] Preferably, the stirring speed is 300-1000 rpm.

[0020] This invention provides the application of the above-mentioned high-temperature resistant and stealthy acid completion fluid in the completion of deep clastic and carbonate reservoirs in the Tarim Basin.

[0021] The beneficial effects of this invention are as follows:

[0022] (1) This invention improves the temperature resistance of the stealth acid by optimizing its components and further develops a high-temperature resistant stealth acid completion fluid by selecting high-temperature anti-swelling agents, high-temperature corrosion inhibitors, and other key treatment agents. This high-temperature resistant stealth acid completion fluid exhibits excellent dissolution of inorganic scale and organic matter at high temperatures (≤140℃), as well as appropriate dissolution of formation minerals, effectively clearing near-wellbore channels and improving reservoir permeability. In addition, this completion fluid also has advantages such as strong inhibition, low corrosion rate, good compatibility, and good reservoir protection effect.

[0023] (2) The preparation method of the high temperature-resistant stealth acid completion fluid of the present invention is simple to operate and easy to prepare on site. It has good application prospects in the completion operation of deep clastic rock and carbonate rock oil reservoirs in the Tarim Basin with a temperature ≤140℃. Detailed Implementation

[0024] The following description of the embodiments is merely to aid in understanding the method and core ideas of the present invention. It should be noted that those skilled in the art can make various improvements and modifications to the present invention without departing from its principles, and these improvements and modifications also fall within the scope of the claims. The following description of the disclosed embodiments enables those skilled in the art to implement or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the present invention is not limited to the embodiments shown herein, but can be applied to a wider scope consistent with the principles and novel features disclosed herein. While any methods and materials similar to or equivalent to those described herein may be used in the implementation or testing of the present invention, preferred methods and materials are listed herein.

[0025] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0026] Example 1

[0027] At room temperature, add 53g of potassium chloride to 200mL of tap water and stir for 15 minutes at a stirring speed of 200 rpm. After the potassium chloride dissolves, add 1g of citric acid, 1g of sodium citrate and 0.3g of hydrofluoric acid respectively, and stir to dissolve. Then add 4g of HJZ-100 type polyamine clay inhibitor (purchased from Kaifeng Hengju Biotechnology Co., Ltd.) and 3g of JY-811 type imidazoline corrosion inhibitor (purchased from Jinan Jingyu New Material Technology Co., Ltd.) to the solution and stir to disperse evenly at a stirring speed of 200 rpm to obtain high temperature resistant stealth acid completion fluid.

[0028] Example 2

[0029] At room temperature, add 90g of sodium formate to 200mL of tap water and stir for 15 minutes at a stirring speed of 200 rpm. After the potassium chloride dissolves, add 1g of oxalic acid, 1g of citric acid and 0.5g of hydrofluoric acid respectively, stir to dissolve, and then add 5g of NW-1 type cationic clay inhibitor and 5g of DRKJ-12 type imidazoline quaternary ammonium salt corrosion inhibitor (purchased from Zhengzhou Derong Technology Co., Ltd.) to the solution. Stir at a stirring speed of 200 rpm to disperse evenly to obtain high temperature resistant stealth acid completion fluid.

[0030] Example 3

[0031] At room temperature, add 152g of potassium formate to 200mL of tap water and stir for 15 minutes at a stirring speed of 200 rpm. After the potassium chloride dissolves, add 1g of citric acid, 1g of phosphoric acid and 0.2g of hydrofluoric acid respectively, and stir to dissolve. Then add 6g of JN-780 type choline chloride clay inhibitor (purchased from Shandong Jinhao Chemical Technology Co., Ltd.) and 6g of JY-811 type imidazoline corrosion inhibitor (purchased from Jinan Jingyu New Material Technology Co., Ltd.) to the solution and stir to disperse evenly at a stirring speed of 200 rpm to obtain the high temperature resistant stealth acid completion fluid.

[0032] Comparative Example 1

[0033] The only difference between this comparative example and Example 1 is that the amount of HJZ-100 polyamine clay inhibitor is 3g and the amount of JY-811 imidazoline corrosion inhibitor is 7g.

[0034] Comparative Example 2

[0035] The only difference between this comparative example and Example 1 is that the amount of HJZ-100 polyamine clay inhibitor is 8g and the amount of JY-811 imidazoline corrosion inhibitor is 2g.

[0036] The performance evaluation of the embodiments was performed in accordance with the following method:

[0037] (1) Density: The density of the completion fluid in the example was determined at room temperature using a specific gravity bottle;

[0038] (2) Dissolution or corrosion rate of inorganic scale and cuttings: Referring to the petroleum and natural gas industry standard SY / T 5358-2002 "Evaluation Method of Reservoir Sensitivity Flow Test", the dissolution or corrosion rate of inorganic scale and cuttings by the completion fluid of the example was tested at a high temperature of 140℃, and the dissolution or corrosion rate of inorganic scale and cuttings by the completion fluid of the example was calculated. In the experiment, the mass concentrations of inorganic scale (calcium carbonate and magnesium carbonate) and cuttings in the completion fluid of the example were 1% and 5%, respectively.

[0039] (3) Solubility of organic matter: The viscosity of the polyacrylamide solution was measured using a Brookfield viscometer. Polyacrylamide of the same concentration was added to the completion fluid of the example and completely dissolved. The mixture was allowed to react at 140°C for 16 hours. The viscosity of the mixture of polyacrylamide and completion fluid of the example was measured. The solubility of organic matter in the completion fluid of the example was calculated using the viscosity of the polyacrylamide solution before and after the reaction.

[0040] (4) Corrosion rate: Referring to the static strip corrosion method in the petroleum and natural gas industry standard "SY / T0026-1999 Water Corrosion Determination Method", a high temperature and high pressure strip corrosion instrument was used to conduct corrosion experiments on P110S steel strips with the completion fluid of the example at a high temperature of 140℃ and normal pressure. The average corrosion rate of P110S steel strips by the completion fluid of the example was calculated based on the mass loss of the test piece.

[0041] (5) Anti-swelling rate: Referring to the anti-swelling rate determination method in the petroleum and natural gas industry standard "SY / T5971-2016 Performance Evaluation Method of Clay Stabilizer for Fracturing, Acidizing and Water Injection in Oil and Gas Fields", a high temperature and high pressure clay swelling rate tester was used to determine the anti-swelling rate of the completion fluid on clay in the example at a high temperature of 140℃.

[0042] (6) Turbidity: Based on the formation water data of the Tahe Block, simulated formation water (NaHCO3 1.02g / L, Na2SO4: 1.66g / L, NaCl: 104.3g / L, CaCl2: 27.04g / L, MgCl2: 4.35g / L, KCl: 55.9g / L) was prepared. The simulated formation water was then mixed with the completion fluid provided in Example 1 in different proportions. The completion fluid of Example 1 was mixed with the formation water in different proportions. The mixture was aged at 140℃ and normal pressure for 16h. The turbidity value of the mixture before and after aging was measured at room temperature using a turbidity meter.

[0043] (7) Core permeability recovery value: Referring to the petroleum and natural gas industry standard SY / T5358-2002 "Evaluation method of reservoir sensitivity flow test", artificial cores were used and core displacement equipment was employed. At 140℃ and below the core critical flow rate, a static contamination test was conducted on the reservoir core by the completion fluid of the example. The change in core permeability before and after static contamination was measured with standard brine, and the permeability recovery value of the core by the completion fluid of the example was calculated.

[0044] Table 1 Performance test results of completion fluid

[0045]

[0046]

[0047] Table 2 Compatibility test results of completion fluid and formation water

[0048]

[0049] As can be seen from the experimental data in Tables 1 and 2, at a high temperature of 140℃, the anti-high temperature stealth acid completion fluid of the present invention has a dissolution rate of 100% for inorganic scale, a degradation rate of more than 93% for organic matter, a dissolution rate of more than 5% for rock cuttings, and a core permeability recovery value of more than 115% (less than 110%, which does not meet the requirements). Therefore, the anti-high temperature stealth acid completion fluid of the present invention can effectively unclog the near-wellbore channels and improve the permeability of the oil layer at high temperatures.

[0050] Meanwhile, the high-temperature resistant stealth acid completion fluid of the present invention also has the advantages of strong inhibition (anti-swelling rate greater than 89%, meeting construction requirements, of which, swelling rate less than 85%, does not meet the requirements and cannot meet construction requirements), low corrosivity (corrosion rate less than 0.06mm / a), and good compatibility, and has good prospects for promotion and application.

Claims

1. A high-temperature resistant, stealthy acid completion fluid, characterized in that, By weight, it includes 2.2-2.5 parts of high-temperature stealth acid, 4-6 parts of high-temperature anti-swelling agent, and 3-6 parts of high-temperature corrosion inhibitor. The high-temperature stealth acid-resistant completion fluid has a cuttings dissolution rate of greater than 5% and a corrosion rate of less than 0.06 mm / a at 140℃, an anti-swelling rate of greater than 89%, and a core permeability recovery value of greater than 115%. The high-temperature hidden acid is a combination of citric acid, sodium citrate and hydrofluoric acid, or a combination of oxalic acid, citric acid and hydrofluoric acid; or a combination of citric acid, phosphoric acid and hydrofluoric acid. The high-temperature anti-swelling agent is HJZ-100 type polyamine clay inhibitor, NW-1 type cationic clay inhibitor or JN-780 type choline chloride clay inhibitor. The high-temperature corrosion inhibitor is JY-811 type imidazoline corrosion inhibitor, DRKJ-12 type imidazoline quaternary ammonium salt corrosion inhibitor, or JY-811 type imidazoline corrosion inhibitor.

2. The high-temperature resistant stealth acid completion fluid according to claim 1, characterized in that, It also includes weighting agents and / or bactericides.

3. The high-temperature resistant stealth acid completion fluid according to claim 2, characterized in that, The weighting agent is one or two of inorganic and organic salts, wherein the inorganic salts include sodium chloride, potassium chloride, calcium chloride and calcium bromide, and the organic salts include sodium formate, cesium formate and potassium formate.

4. A method for preparing the high-temperature resistant, stealthy acid completion fluid according to any one of claims 1-3, characterized in that, Includes the following steps: The high-temperature stealth acid, high-temperature anti-swelling agent, and high-temperature corrosion inhibitor were added sequentially to fresh water, stirred and dissolved, and the density was adjusted to obtain the high-temperature stealth acid resistant completion fluid.

5. The preparation method according to claim 4, characterized in that, The stirring speed is 300-1000 rpm.

6. The application of the high-temperature resistant stealth acid completion fluid according to any one of claims 1-3, and / or the high-temperature resistant stealth acid completion fluid prepared by the preparation method according to any one of claims 4-5 in the completion of deep clastic rock and carbonate rock oil reservoirs in the Tarim Basin.

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