Oil well cement flexible agent based on modified rubber powder and preparation method thereof

Abstract

The invention discloses an oil well cement flexible agent based on modified rubber powder and a preparation method thereof. The oil well cement flexible agent is prepared from the following raw materials in parts by weight: 30-50 parts of acrylate rubber powder and 10-15 parts of expanded vermiculite powder. 3 to 10 parts of maleic anhydride and 0.3 to 0.6 part of an emulsifier; 0.3 to 0.6 part of an initiator; 5 to 10 parts of treated oxidized-etherified starch; the treated oxidized-etherified starch is prepared by the following steps: performing softening treatment on starch, performing treatment through an oxidizing agent under the action of a basic catalyst, and then performing etherification through an etherifying agent. The invention has the beneficial effect of good flowability and compatibility.

Description

Technical Field

[0001] The invention relates to the technical field of cement slurry cementing in oil and gas production, and in particular to an oil well cement flexibility agent based on modified rubber powder and a preparation method thereof. Background Art

[0002] In the cementing stage of oil and gas development, the casing needs to be extended into the oil and gas well, and then cement is injected through the casing. The cement flows into the gap between the casing and the well wall to fill it, and then cementing is performed after solidification. Therefore, in the cementing stage, it is very important to ensure the fluidity of the cement slurry. The flexibilizer is the key to ensuring the fluidity of the cement slurry.

[0003] At present, there are many types of flexible agents on the market, but most of them have poor compatibility with cement slurry, that is, when mixed with cement slurry, they are easy to precipitate in the cement slurry. Therefore, some companies choose to modify some flexible agent polymers by grafting some groups to allow the flexible agent to reasonably adsorb calcium ions and cement, but this method will lead to poor fluidity. Therefore, how to balance fluidity and compatibility is a current problem. Summary of the invention

[0004] In order to solve the above problems, the present invention provides an oil well cement flexibilizer based on modified rubber powder, which can significantly improve the crack resistance, flexural resistance and bonding strength of concrete and improve the toughness of concrete.

[0005] The object of the present invention is achieved through the following technical solutions: In the first aspect, an oil well cement flexibilizer based on modified rubber powder is provided, which is prepared from the following raw materials in parts by weight:

[0006] 30-50 parts of acrylic rubber powder, 10-15 parts of expanded vermiculite powder;

[0007] 3-10 parts of maleic anhydride, 0.3-0.6 parts of emulsifier;

[0008] 0.3-0.6 parts of initiator;

[0009] 5 to 10 parts of treated oxidized-etherified starch; the treated oxidized-etherified starch is obtained by softening starch, subjecting it to an oxidizing agent under the action of an alkaline catalyst, and then subjecting it to etherification by an etherifying agent.

[0010] In some preferred embodiments, the treated oxidized-etherified starch refers to: the starch is softened by polyvinyl alcohol, then oxidized in anhydrous ethanol under the action of an alkaline catalyst using sodium hypochlorite as an oxidant, and then etherified by a solvent method in anhydrous ethanol in an alkaline environment using ethylene oxide as an etherifying agent.

[0011] In a second aspect, a method for preparing an oil well cement flexibilizer based on modified rubber powder is provided, comprising the following steps:

[0012] S1. Measure maleic anhydride and emulsifier, mix them, and fully emulsify them under the action of ultrasound to obtain a modified emulsifier;

[0013] S2. Measure acrylate rubber powder and expanded vermiculite powder; then stir and heat to 60 ℃ ~ 80 ℃, add initiator after 0.5h, maintain the temperature at 60 ℃ ~ 80 ℃ and stir to obtain a preliminary reaction polymer;

[0014] S3. Then the modified emulsifier is poured into S2 to carry out a preliminary graft polymerization reaction for 0.5h;

[0015] S4. Prepare the treated oxidized-etherified starch, pour it into the polymer after cooling in S3, and then stir it thoroughly.

[0016] In some preferred embodiments, after S4 is prepared, it can be directly used to prepare cementing slurry; it can also be dried and prepared into powder.

[0017] In a third aspect, a cementing slurry is provided, which uses the above-mentioned oil well cement flexible agent as a preparation raw material; in the cementing slurry, the cementing cement flexible agent powder accounts for 0.3% to 0.5% of the cement dosage by weight.

[0018] In the present invention: a. the acrylate rubber powder monomer itself can undergo a preliminary polymerization reaction, and some groups of the preliminary reaction polymer are adsorbed on the expanded vermiculite powder; then a part of the modified emulsifier is preliminarily grafted, that is, grafted on the preliminary reaction polymer; then the post-treated oxidized-etherified starch is added, and another part of the modified emulsifier will be grafted on the preliminary reaction polymer with the help of a part of the treated oxidized-etherified starch, and the other part of the treated oxidized-etherified starch does not participate in the reaction as a mixture; b. In this way, since the starch is softened by polyvinyl alcohol, the starch can be easily dispersed and soluble in the obtained rubber polymer; and the treated oxidized-etherified starch is adsorbed on the cement particles, which can promote the fluidity of the cement; c. In layman's terms, the polymer with acrylate rubber improves its fluidity through the modified emulsifier, the polymer of acrylate rubber and the treated oxidized-etherified starch, and the treated oxidized-etherified starch can be adsorbed on the cement particles, which indirectly achieves the compatibility of the polymer of acrylate rubber and cement slurry without affecting the fluidity.

[0019] Beneficial effects of the present invention:

[0020] 1. The flexible agent has good compatibility with cement and can ensure good fluidity of cement slurry;

[0021] Specifically, the polymer of acrylic rubber is indirectly mediated on cement particles through treated oxidized-etherified starch, thereby preventing the softener from precipitating out of the cement slurry; in addition, the polymer of acrylic rubber has good fluidity through the modified emulsifier, and the cement has good fluidity through the treated oxidized-etherified starch.

[0022] Instruction Manual

[0023] Figure 1 This is a precipitation experiment photo of Comparative Example 2;

[0024] Figure 2 This is a photo of the precipitation experiment of Example 2. DETAILED DESCRIPTION

[0025] The embodiments of the present invention are described in detail below, but the present invention can be implemented in a variety of different ways as defined and covered by the claims. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0026] In the first aspect, the specific embodiment of the present invention discloses an oil well cement flexible agent based on modified rubber powder, which is prepared from the following raw materials in parts by weight: 30-50 parts of acrylate rubber powder, 10-15 parts of expanded vermiculite powder; 3-10 parts of maleic anhydride, 0.3-0.6 parts of sodium dodecyl sulfate emulsifier; 0.3-0.6 parts of ammonium persulfate initiator; 5-10 parts of treated oxidized-etherified starch;

[0027] The treated oxidized-etherified starch refers to starch that is softened by polyvinyl alcohol, then oxidized by sodium hypochlorite as an oxidant in anhydrous ethanol under the action of an alkaline catalyst, and then etherified by a solvent method in anhydrous ethanol in an alkaline environment using ethylene oxide as an etherifying agent, and the treated starch is dried.

[0028] In a second aspect, a specific embodiment of the present invention further discloses a method for preparing an oil well cement flexibility agent based on modified rubber powder, which is characterized by comprising the following steps:

[0029] S1. Measure maleic anhydride and emulsifier, mix them, and fully emulsify them under the action of ultrasound to obtain a modified emulsifier;

[0030] S2. Measure acrylate rubber powder and expanded vermiculite powder; then stir and heat to 60 ℃ ~ 80 ℃, add initiator after 0.5h, add sodium hydroxide, maintain the temperature at 60 ℃ ~ 80 ℃ and stir to obtain a preliminary reaction polymer;

[0031] S3. Then the modified emulsifier is poured into S2 to carry out a preliminary graft polymerization reaction for 0.5h;

[0032] S4. Prepare the treated oxidized - etherified starch, pour it into the polymer after cooling in S3, and then stir it thoroughly;

[0033] After S4 treatment, it can be directly used to prepare cementing slurry; it can also be dried and prepared into powder.

[0034] In a third aspect, the specific embodiment of the present invention also discloses a cementing slurry, which uses an oil well cement flexible agent as a preparation raw material; in the cementing slurry, the cementing cement flexible agent powder is 0.3% to 0.5% of the cement dosage by weight.

[0035] Exemplarily, the specific dosage is further described below.

[0036] Example 1

[0037] The oil well cement flexible agent based on modified rubber powder comprises, by weight, 30 parts of acrylate rubber powder, 15 parts of expanded vermiculite powder, 3 parts of maleic anhydride, 0.3 parts of ammonium persulfate, and 0.3 parts of sodium dodecyl sulfate; and 5 parts of treated oxidized-etherified starch. The oxidized-etherified starch is prepared according to the method in the first aspect, and the oil well cement flexible agent is prepared according to the method in the second aspect.

[0038] The oil well cement flexible agent prepared as above is used to prepare cementing cement slurry, specifically, according to some conventional proportions, 100 parts of cement, 45 parts of magnetite powder, 35 parts of quartz sand, 1.0 part of microsilicon, 2.5 parts of expansion agent, 1.5 parts of reinforcing agent, 0.2 part of dispersant, 4.0 parts of fluid loss reducer, 0.5 part of retarder, and then (100+45+35+1.0+2.5+1.5+0.2+4.0+0.5)×0.3% of the oil well cement flexible agent of the present invention is added, and the cement slurry is prepared according to the conventional cement slurry preparation method.

[0039] Example 2

[0040] The oil well cement flexible agent based on modified rubber powder comprises, by weight, 40 parts of acrylate rubber powder, 15 parts of expanded vermiculite powder, 8 parts of maleic anhydride, 0.6 parts of ammonium persulfate, and 0.6 parts of sodium dodecyl sulfate; and 10 parts of treated oxidized-etherified starch. The oxidized-etherified starch is prepared according to the method in the first aspect, and the oil well cement flexible agent is prepared according to the method in the second aspect.

[0041] The oil well cement flexible agent prepared above is used to prepare cementing cement slurry, specifically, some conventional proportions, 100 parts of cement, 45 parts of magnetite powder, 35 parts of quartz sand, 1.0 part of microsilicon, 2.5 parts of expansion agent, 1.5 parts of reinforcing agent, 0.2 parts of dispersant, 4.0 parts of fluid loss reducer, 0.5 parts of retarder, and then (100+45+35+1.0+2.5+1.5+0.2+4.0+0.5)×0.4% of the oil well cement flexible agent of the present invention is added, 0.3% of the total weight is water, and the cement slurry is prepared according to the conventional cement slurry preparation method.

[0042] Example 3

[0043] The oil well cement flexible agent based on modified rubber powder comprises, by weight, 50 parts of acrylate rubber powder, 12 parts of expanded vermiculite powder, 10 parts of maleic anhydride, 0.5 parts of ammonium persulfate, and 0.5 parts of sodium dodecyl sulfate; and 8 parts of treated oxidized-etherified starch. The oxidized-etherified starch is prepared according to the method in the first aspect, and the oil well cement flexible agent is prepared according to the method in the second aspect.

[0044] The oil well cement flexible agent prepared as above is used to prepare cementing cement slurry, specifically, according to some conventional proportions, 100 parts of cement, 45 parts of magnetite powder, 35 parts of quartz sand, 1.0 part of microsilicon, 2.5 parts of expansion agent, 1.5 parts of reinforcing agent, 0.2 part of dispersant, 4.0 parts of fluid loss reducer, 0.5 part of retarder, and then (100+45+35+1.0+2.5+1.5+0.2+4.0+0.5)×0.5% of the oil well cement flexible agent of the present invention is added, and the cement slurry is prepared according to the conventional cement slurry preparation method.

[0045] Performance Test 1

[0046] Weigh the cement slurries prepared in the above-mentioned Example 1, Example 2, and Example 3 to obtain equal weights as test examples;

[0047] The other components are the same as those in Example 1, but "treated oxidized-etherified starch" is not added as Comparative Example 1 (the same weight of "modified emulsifier" is used to replace "treated oxidized-etherified starch");

[0048] The other components are the same as those in Example 2, but "treated oxidized-etherified starch" is not added as Comparative Example 2 (the same weight of "modified emulsifier" is used to replace "treated oxidized-etherified starch");

[0049] The other components are the same as those in Example 3, but "treated oxidized-etherified starch" is not added as Comparative Example 3 (the same weight of "modified emulsifier" is used to replace "treated oxidized-etherified starch");

[0050] According to the provisions of GB / T 8007-2000 "Test method for homogeneous performance of concrete admixtures", the fluidity of the obtained cement paste was measured. The H tube with an inner diameter of 4±0.1mm was used to record the time taken for the paste to flow down to a volume of 100mL to determine the fluidity of the cement. The measurement results are shown in Table 1.

[0051] Table 1 Comparison of H pipe and net fluidity test

[0052]

[0053] In addition, it should be noted that the cement slurry of this ratio in this scheme is a heavier cement slurry, T100 / s is about 17.4-19.8 (more than 20 means good fluidity), and fluidity / mm is generally about 285-295 (more than 295 means good fluidity). It can be clearly seen from Table 1 that the addition of "treated oxidized-etherified starch" in this scheme significantly improves fluidity.

[0054] Performance Test 2

[0055] Example 2 and Comparative Example 2 used in Performance Test 1 were selected. After standing for 2 days, the precipitation and clarity of the supernatant were checked. The experimental results are as follows: Figure 1 and Figure 2 shown.

[0056] Figure 1 This is comparative example 2, with the left side showing the comparison 2 days ago and the right side showing the comparison 2 days later;

[0057] Figure 2 This is a comparison of Example 2, with the left side showing 2 days before and the right side showing 2 days after.

[0058] It can be seen that Example 2 of the present solution still has good compatibility after 2 days. Comparative Example 2 shows precipitation after 2 days. This shows that the treated oxidized-etherified starch can increase the compatibility between the rubber polymer and the cement slurry.

[0059] At the same time, performance test 1 and performance test 2 show that this solution can take into account good fluidity and compatibility.

[0060] Finally, it should be noted that the above specific embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned specific embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned implementations, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the various implementation modes and specific embodiments of the present invention.

Claims

1. An oil well cement flexibilizer based on modified rubber powder, characterized in that: It is made from the following raw materials in parts by weight: 30-50 parts of acrylic rubber powder, 10-15 parts of expanded vermiculite powder; 3-10 parts of maleic anhydride, 0.3-0.6 parts of emulsifier; 0.3-0.6 parts of initiator; 5 to 10 parts of treated oxidized-etherified starch; the treated oxidized-etherified starch is obtained by softening starch, subjecting it to an oxidizing agent under the action of an alkaline catalyst, and then subjecting it to etherification by an etherifying agent.

2. The oil well cement flexibilizer based on modified rubber powder according to claim 1, characterized in that: The treated oxidized-etherified starch refers to: the starch is softened by polyvinyl alcohol, then oxidized in anhydrous ethanol under the action of an alkaline catalyst using sodium hypochlorite as an oxidant, and then etherified by a solvent method in anhydrous ethanol in an alkaline environment using ethylene oxide as an etherifying agent.

3. The method for preparing an oil well cement flexibilizer based on modified rubber powder according to claim 1 or 2, characterized in that: The following steps are involved: S1. Measure maleic anhydride and emulsifier, mix them, and fully emulsify them under the action of ultrasound to obtain a modified emulsifier; S2. Measure acrylate rubber powder and expanded vermiculite powder; then stir and heat to 60 ℃ ~ 80 ℃, add initiator after 0.5h, add sodium hydroxide, maintain the temperature at 60 ℃ ~ 80 ℃ and stir to obtain a preliminary reaction polymer; S3. Then the modified emulsifier is poured into S2 to carry out a preliminary graft polymerization reaction for 0.5h; S4. Prepare the treated oxidized-etherified starch, pour it into the polymer after cooling in S3, and then stir it thoroughly.

4. The method for preparing the oil well cement flexibilizer based on modified rubber powder according to claim 3, characterized in that: After S4 is prepared, it can be directly used to prepare cementing slurry; it can also be dried and prepared into powder.

5. A cementing slurry, characterized in that: Using the oil well cement flexible agent based on modified rubber powder as described in any one of claims 1 to 4 as a preparation raw material; In cementing slurry, the cementing cement flexible agent powder accounts for 0.3% to 0.5% of the cement dosage by weight.

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