Damaging mud cake type oil displacement flushing agent

Abstract

The present invention belongs to the technical field of cementing engineering and relates to a mud cake-destroying oil displacement flush fluid. In terms of mass percentage, the flush fluid is composed of the following substances: sodium dodecyl sulfate 8-12%, emulsifier 4-6%, emulsification aid 0.375-2.5%, dissolution aid 7.5-12.5%, mud cake destroyer 6.5-8.5%, glass fiber 0.5-1.0%, and the balance is water; the emulsifier is a mixture of Tween 80 and OP-20; the emulsification aid is polyether L62; the dissolution aid is an alcohol; the mud cake destroyer is a mixture of sodium hydroxide, ammonium persulfate, and EDTA-2Na. Compared with the prior art, the mud cake-destroying oil displacement flush fluid of the present invention has a good flushing efficiency, a high corrosion efficiency, and a flush fluid formulation with easily available raw materials and a moderate price, achieving the destruction effect on the mud cake of white oil-based drilling fluid and capable of improving the cementing efficiency in the environment of white oil-based drilling fluid.

Description

Technical Field

[0001] The present invention relates to the technical field of cementing engineering, and particularly relates to a mud cake-breaking type oil displacement flushing agent. Background Art

[0002] Surfactant-based oil displacement flushing agents are widely used in oil fields, especially having good effects when cleaning oil stains, lubricating oil and equipment surfaces. However, in complex reservoirs or environments containing macromolecular substances, their oil displacement effects are not satisfactory. Especially in oil field environments with high viscosity, high salinity, or containing a large amount of impurities, the oil displacement effects of surfactants are limited, and they are likely to have a certain impact on the environment and water quality.

[0003] With the increasing degree of exploitation and utilization of unconventional oil and gas resources, white oil-based drilling fluids are increasingly widely used in the field of oil drilling due to their better lubricity, thermal stability and rheology. However, during drilling, the white oil-based drilling fluid stays on the wellbore wall, making it difficult to clean the wellbore wall and casing, and forming a dense, highly oily and hydrophobic oil-based mud cake. Conventional water-based cleaning agents cannot directly play a role, and it is extremely difficult to remove during the cementing process, thus reducing the cementing quality of the cement sheath and affecting the engineering quality. Summary of the Invention

[0004] Aiming at the problems in the prior art, the present invention proposes a mud cake-breaking type oil displacement flushing agent, and the flushing agent of the present invention has good flushing efficiency, high dissolution efficiency, easily available raw materials and moderate prices.

[0005] The mud cake-breaking type oil displacement flushing agent of the present invention, in terms of mass percentage, is composed of the following substances: sodium dodecyl sulfate 8-12%; emulsifier 4-6%; emulsification aid 0.375-2.5%; dissolution aid 7.5-12.5%; mud cake breaker 6.5-8.5%; glass fiber 0.5-1.0%; the balance is water.

[0006] The emulsifier is a mixture of Tween 80 and OP-20, and in terms of mass ratio, Tween 80:OP-20 = 1:1.

[0007] The emulsification aid is polyether L62.

[0008] The dissolution aid is an alcohol, such as methanol or isopropanol.

[0009] The mud cake breaker is a mixture of sodium hydroxide, ammonium persulfate and EDTA-2Na, and in terms of mass ratio, sodium hydroxide:ammonium persulfate:EDTA-2Na = 1:2:1. Sodium hydroxide consumes asphaltene, ammonium persulfate oxidatively decomposes polymers, and EDTA-2Na chelates and removes insoluble solid weighting materials.

[0010] The length of the glass fiber used is 3 mm, and the flushing effect is improved by enhancing the mechanical cleaning ability of the flushing agent, improving its fluidity, enhancing its high-temperature resistance performance, and increasing its structural stability.

[0011] The preparation method of the described mud cake-breaking oil displacement flushing agent is simple, and the steps are as follows: Add water into the reaction kettle, and then add the surfactant, emulsifier, emulsification aid, dissolution aid, mud cake breaker, mud cake breaking aid, and glass fiber weighed in proportion into the reaction kettle, and stir well to obtain the mud cake flushing agent.

[0012] Compared with the prior art, the mud cake-breaking oil displacement flushing agent described in the present invention has a good flushing efficiency, a high dissolution efficiency, easily available raw materials and a moderate price, realizes the destruction effect on the white oil-based drilling fluid mud cake, and can improve the cementing efficiency in the white oil-based drilling fluid environment. Description of the Drawings

[0013] Figure 1 It is the appearance diagram of the surface of the rotary drum before flushing;

[0014] Figure 2 It is the appearance diagram of the surface of the rotary drum after flushing. Detailed Description of the Invention

[0015] Example 1

[0016] Add 73.125 parts by weight of clear water into the reaction kettle, and then add 8 parts by weight of sodium dodecyl sulfate, 4 parts by weight of emulsifier, 0.375 part by weight of polyether L62; 7.5 parts by weight of isopropanol, 6.5 parts by weight of mud cake breaker, and 0.5 part by weight of 3 mm glass fiber in sequence, and stir well to obtain the mud cake flushing agent of the present invention, and clean the prepared mud cake.

[0017] The described emulsifier is a mixture of Tween 80 and OP-20, and in terms of mass ratio, Tween 80:OP-20 = 1:1.

[0018] The described mud cake breaker is a mixture of sodium hydroxide, ammonium persulfate, and EDTA-2Na; in terms of mass ratio, sodium hydroxide:ammonium persulfate:EDTA-2Na = 1:2:1.

[0019] Example 2

[0020] Add 65.5 parts by weight of clear water into the reaction kettle, and then add 10 parts by weight of sodium dodecyl sulfate, 5 parts by weight of emulsifier, 1.25 parts by weight of polyether L62; 10 parts by weight of isopropanol, 7.5 parts by weight of mud cake breaker, and 0.75 part by weight of 3 mm glass fiber in sequence, and stir well to obtain the mud cake flushing agent of the present invention, and clean the prepared mud cake.

[0021] The emulsifier described is a mixture of Tween 80 and OP-20. By mass ratio, Tween 80:OP-20 = 1:1.

[0022] The filter cake breaker described is a mixture of sodium hydroxide, ammonium persulfate, and EDTA-2Na; by mass ratio, sodium hydroxide:ammonium persulfate:EDTA-2Na = 1:2:1.

[0023] Example 3

[0024] Add 57.5 parts by weight of clear water to the reaction kettle, and then successively add 12 parts by weight of sodium dodecyl sulfate, 6 parts by weight of emulsifier, 2.5 parts by weight of polyether L62; 12.5 parts by weight of isopropanol, 8.5 parts by weight of filter cake breaker, and 1 part by weight of 3mm glass fiber, and stir well to obtain the filter cake rinsing agent of the present invention, and clean the prepared filter cake.

[0025] The emulsifier described is a mixture of Tween 80 and OP-20. By mass ratio, Tween 80:OP-20 = 1:1.

[0026] The filter cake breaker described is a mixture of sodium hydroxide, ammonium persulfate, and EDTA-2Na; by mass ratio, sodium hydroxide:ammonium persulfate:EDTA-2Na = 1:2:1.

[0027] Example 4

[0028] Add 66 parts by weight of clear water to the reaction kettle, and then successively add 10 parts by weight of sodium dodecyl sulfate, 6 parts by weight of emulsifier, 1.25 parts by weight of polyether L62; 7.5 parts by weight of isopropanol, 8.5 parts by weight of filter cake breaker, and 0.75 part by weight of 3mm glass fiber, and stir well to obtain the filter cake rinsing agent of the present invention, and clean the prepared filter cake.

[0029] The emulsifier described is a mixture of Tween 80 and OP-20. By mass ratio, Tween 80:OP-20 = 1:1.

[0030] The filter cake breaker described is a mixture of sodium hydroxide, ammonium persulfate, and EDTA-2Na; by mass ratio, sodium hydroxide:ammonium persulfate:EDTA-2Na = 1:2:1.

[0031] Example 5

[0032] Add 65.25 parts by weight of clear water to the reaction kettle, and then successively add 10 parts by weight of sodium dodecyl sulfate, 5 parts by weight of emulsifier, 1.25 parts by weight of polyether L62; 10 parts by weight of isopropanol, 7.5 parts by weight of filter cake breaker, and 1 part by weight of 3mm glass fiber, and stir well to obtain the filter cake rinsing agent of the present invention, and clean the prepared filter cake.

[0033] The emulsifier described is a mixture of Tween 80 and OP-20. By mass ratio, Tween 80:OP-20 = 1:1.

[0034] The filter cake breaker described is a mixture of sodium hydroxide, ammonium persulfate, and EDTA-2Na; by mass ratio, sodium hydroxide:ammonium persulfate:EDTA-2Na = 1:2:1.

[0035] Comparative Example 1

[0036] Add 70.25 parts by weight of clear water to the reaction kettle, and then add 5 parts by weight of sodium dodecyl sulfate, 5 parts by weight of emulsifier, 1.25 parts by weight of polyether L62; 10 parts by weight of isopropanol, 7.5 parts by weight of filter cake breaker, and 1 part by weight of 3mm glass fiber in sequence. Stir well to obtain the filter cake rinsing agent of the present invention, and clean the prepared filter cake.

[0037] The emulsifier described is a mixture of Tween 80 and OP-20. By mass ratio, Tween 80:OP-20 = 1:1.

[0038] The filter cake breaker described is a mixture of sodium hydroxide, ammonium persulfate, and EDTA-2Na; by mass ratio, sodium hydroxide, ammonium persulfate, EDTA-2Na = 1:2:1.

[0039] Comparative Example 2

[0040] Add 67.75 parts by weight of clear water to the reaction kettle, and then add 10 parts by weight of sodium dodecyl sulfate, 5 parts by weight of emulsifier, 1.25 parts by weight of polyether L62; 10 parts by weight of isopropanol, 5 parts by weight of filter cake breaker, and 1 part by weight of 3mm glass fiber in sequence. Stir well to obtain the filter cake rinsing agent of the present invention, and clean the prepared filter cake.

[0041] The emulsifier described is a mixture of Tween 80 and OP-20. By mass ratio, Tween 80:OP-20 = 1:1.

[0042] The filter cake breaker described is a mixture of sodium hydroxide, ammonium persulfate, and EDTA-2Na; by mass ratio, sodium hydroxide:ammonium persulfate:EDTA-2Na = 1:2:1.

[0043] Experimental Example

[0044] Performance Test

[0045] Evaluation experiment on filter cake cleaning efficiency:

[0046] Method for making filter cake: Use a high-temperature and high-pressure fluid loss instrument and white oil-based drilling fluid to make an oil-based filter cake. The steps are as follows:

[0047] 1. Assembly: First, place the rubber ring, then the filter paper, and then the filter screen. Tighten the lower cover of the slurry cylinder with a wrench. Then place another rubber ring. Loosen the upper cover slightly for subsequent pouring of drilling fluid.

[0048] 2. Preheating: First, heat to 90 °C, pour in the drilling fluid to about 3 cm from the top, tighten the upper cover, and then heat to 150 °C. 3. Inspection: Conduct an airtightness inspection before ventilation. Install the liquid accumulation cylinder and assemble the ventilation pipeline to ensure that the air release valve is closed.

[0049] 4. After heating is completed, open the main valve of the gas tank and slowly pressurize. The pressure is 4.5 MPa on the upper part and 1 MPa on the lower part. The pressure difference is 3.5 MPa. Then loosen the upper water loss joint, press the air into it, and then loosen the lower water loss joint for filtration loss. Start the timer and time for 10 minutes.

[0050] 5. After the experiment, disassemble the instrument, take out the mud cake, and clean and organize the experimental instrument.

[0051] Experimental method: Cut the prepared mud cake into 4 pieces of similar size; Weigh the rotating cylinder and rubber band of a clean six-speed rotational viscometer, denoted as M 1 ; Bind the mud cake together with the filter paper to the wall of the rotating cylinder of the rotational viscometer with a rubber band, and weigh the rotating cylinder, denoted as W 1 ; Prepare flushing agents with different components and mass fractions; Flush the rotating cylinder at a rotational speed of 300 r / min for 10 minutes at room temperature; After flushing, remove the rotating cylinder, let it air dry naturally for 5 - 10 minutes, and then weigh the rotating cylinder, denoted as W 2 ; After cleaning and drying the filter paper, weigh the filter paper, denoted as M 2 . Calculate the total mass of the clean rotating cylinder, rubber band, and filter paper M 1 + M 2 , denoted as W 0 ;

[0052] Among them, the flushing efficiency η is calculated according to the following formula, and three parallel tests are carried out and the average value is taken. The error of the parallel tests does not exceed 5%;

[0053] ;

[0054] W 1 —The total weight of the rotating cylinder, rubber band, filter paper and mud cake, in grams (g);

[0055] W 2— Weight of the rotating drum and residual mud cake after flushing, in grams (g);

[0056] M 1 — Weight of the rotating drum and rubber band of a clean six-speed rotational viscometer, in grams (g);

[0057] M 2 — Weight of the filter paper, in grams (g).

[0058] Data in the examples and comparative examples are as follows in the table:

[0059] 。

[0060] It can be seen from the table that the dosage of the mud cake breaker has a significant impact on the flushing efficiency; the mud cake flushing agent has a very good overall effect on the mud cake flushing, and the average flushing efficiency exceeds 93%.

Claims

1. A mud cake destroying oil displacement flushing agent, characterized in that: The flushing agent is composed of the following substances in percentage by mass: 8-12% sodium dodecyl sulfate; 4-6% emulsifier; 0.375-2.5% emulsifying aid; 7.5-12.5% ​​dissolving aid; 6.5-8.5% mud cake destroyer; 0.5-1.0% glass fiber; the rest is water; the mud cake is a white oil-based drilling fluid mud cake; The emulsifier is a mixture of Tween 80 and OP-20, with a mass ratio of Tween 80:OP-20 = 1:1; The emulsifying aid is polyether L62; The dissolution aid is alcohol; The mud cake destroyer is a mixture of sodium hydroxide, ammonium persulfate and EDTA-2Na, with a mass ratio of sodium hydroxide: ammonium persulfate: EDTA-2Na = 1:2:1; The length of the glass fiber is 3 mm.

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