Reinforcing agent for oil-based drilling fluid leaking stoppage cement paste and application of reinforcing agent

Abstract

The invention relates to the technical field of oil and gas wells, in particular to a reinforcing agent for oil-based drilling fluid leaking stoppage cement paste and application of the reinforcing agent, and aims to overcome the defects in the prior art. The reinforcing agent is prepared from the following components in parts by weight: 65 to 80 parts of a micro demulsifier, 7.5 to 15 parts of a hydrophilic emulsifier, 7.5 to 15 parts of an anionic hydrophilic emulsification reinforcing agent and 5 to 10 parts of a nonionic hydrophilic emulsification reinforcing agent. According to the invention, the compatibility of the cement paste and the oil-based drilling fluid can be effectively improved, and the success rate of cementing plugging of the oil-based drilling fluid is improved.

Description

Technical Field

[0001] The invention relates to the technical field of oil and gas wells, and in particular to an enhancer for oil-based drilling fluid plugging cement slurry and application thereof. Background Art

[0002] Well leakage often occurs during drilling with oil-based drilling fluid, such as horizontal drilling in the shale gas market. Traditional plugging technology is difficult to quickly and efficiently deal with well leakage, especially malignant leakage, and the risk of re-leakage after treatment is high. Cement plugging is a reliable means to treat oil-based drilling fluid leakage, but the success rate of plugging oil-based drilling fluid with traditional cement slurry is low and difficult to meet the requirements of on-site operations.

[0003] The main reasons for the low success rate of plugging leaks with cement using oil-based drilling fluid are as follows: (1) After the oil-based drilling fluid leaks, the oil-based drilling fluid will contaminate the wall of the formation fracture into an oil-wet wall during the process of flowing into the formation fracture, resulting in the deterioration of the bonding properties between the fracture wall and the cement slurry, affecting the plugging effect; (2) There are a large number of emulsifiers and oil in the oil-based drilling fluid, which will form an emulsion after mixing with the cement slurry, causing the viscosity of the mixture of cement slurry and oil-based drilling fluid to increase abnormally, affecting the safety of the plugging operation; (3) The emulsion formed by the oil-based drilling fluid and the cement slurry will cause the mixed fluid of the oil-based drilling fluid and the cement slurry to have no strength, affecting the plugging effect. Therefore, it is of great significance to develop a cement slurry enhancer that can effectively improve the compatibility of oil-based drilling fluid and cement slurry and enhance the bonding properties of cement slurry and oil-wet fracture wall. Summary of the invention

[0004] The purpose of the present invention is to address the deficiencies of the prior art and to propose an enhancer for oil-based drilling fluid plugging cement slurry and its application. The present invention improves the compatibility of cement slurry with oil-based drilling fluid by improving the distribution of emulsifier at the oil-water interface, and improves the bonding properties of cement stone and crack wall by improving the wettability of crack wall.

[0005] In order to solve the above technical problems, the technical solution provided by the present invention is:

[0006] In a first aspect, the present invention provides an enhancer for oil-based drilling fluid plugging cement slurry, the enhancer comprising the following components in parts by weight: 65-80 parts of micro-emulsifier, 7.5-15 parts of hydrophilic emulsifier, 7.5-15 parts of anionic hydrophilic emulsifier enhancer, and 5-10 parts of nonionic hydrophilic emulsifier enhancer.

[0007] Furthermore, the micro-emulsifier is sodium sulfate.

[0008] Furthermore, the hydrophilic emulsifier is sodium lauryl sulfate.

[0009] Furthermore, the anionic hydrophilic emulsifier enhancer is sodium α-olefin sulfonate.

[0010] Furthermore, the nonionic hydrophilic emulsifier is lauroyl diethanolamide.

[0011] Furthermore, the mesh size of the sodium sulfate is 300-400 meshes.

[0012] Furthermore, the components of the enhancer need to be uniformly mixed to obtain the enhancer.

[0013] Furthermore, the components of the reinforcing agent are mixed in a powder mixer to obtain the reinforcing agent.

[0014] Furthermore, the components of the enhancer need to be mixed in a powder mixer for more than 20 minutes to obtain the enhancer.

[0015] In a second aspect, the present invention provides an application of the enhancer for oil-based drilling fluid plugging cement slurry in oil-based drilling fluid plugging cement slurry.

[0016] Based on the above technical solutions, the technical effects that can be achieved by the present invention are:

[0017] 1. In the present invention, sodium sulfate can ensure that the water-in-oil emulsion formed by mixing the oil-based drilling fluid and cement slurry is slightly demulsified. The synergistic effect of sodium dodecyl sulfate, sodium α-olefin sulfonate, and lauroyl diethanolamine can transform the slightly demulsified mixed fluid into an oil-in-water emulsion, and prevent the demulsification of the water-in-oil emulsion formed by sodium sulfate, which causes the oil to completely precipitate from the mixed fluid, thereby ensuring the uniformity of the mixed fluid. Sodium dodecyl sulfate, sodium α-olefin sulfonate, and lauroyl diethanolamine can also improve the interface bonding properties between the oily fracture wall and the cement slurry.

[0018] 2. After the present invention is added to cement slurry, the compatibility of cement slurry and oil-based drilling fluid can be effectively improved, ensuring the rheological properties, sufficient strength and bonding properties of the mixed fluid of cement slurry and oil-based drilling fluid with the crack wall. DETAILED DESCRIPTION

[0019] In order to make the purpose, technical scheme and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention, that is, the embodiments described are only part of the embodiments of the present invention, rather than all the embodiments.

[0020] Therefore, the following detailed description of the embodiments of the present invention is not intended to limit the scope of the invention claimed for protection, but merely represents selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without making creative work are within the scope of protection of the present invention.

[0021] Unless otherwise specified, the experimental methods used in the following examples are all conventional methods; the reagents, materials, etc. used in the following examples, unless otherwise specified, can be obtained from commercial channels.

[0022] Example 1

[0023] This embodiment provides an enhancer for oil-based drilling fluid plugging cement slurry. The enhancer includes the following components in parts by weight: 80 parts of sodium sulfate, 7.5 parts of sodium dodecyl sulfate, 7.5 parts of sodium α-olefin sulfonate, and 5 parts of lauroyl diethanolamine. The components are sequentially added into a powder mixer and mixed for more than 20 minutes to obtain the enhancer.

[0024] Example 2

[0025] This embodiment provides an enhancer for oil-based drilling fluid plugging cement slurry. The enhancer includes the following components in parts by weight: 65 parts of sodium sulfate, 15 parts of sodium dodecyl sulfate, 15 parts of sodium α-olefin sulfonate, and 10 parts of lauroyl diethanolamine. The components are sequentially added into a powder mixer and mixed for more than 20 minutes to obtain the enhancer.

[0026] Example 3

[0027] This embodiment provides an enhancer for oil-based drilling fluid plugging cement slurry. The enhancer includes the following components in parts by weight: 75 parts of sodium sulfate, 10 parts of sodium dodecyl sulfate, 10 parts of sodium α-olefin sulfonate, and 5 parts of lauroyl diethanolamine. The components are sequentially added into a powder mixer and mixed for more than 20 minutes to obtain the enhancer.

[0028] Comparative Example 1

[0029] Enhancers do not contain any substances.

[0030] Comparative Example 2

[0031] The reinforcing agent includes the following components in parts by weight: 100 parts of sodium α-olefin sulfonate.

[0032] Comparative Example 3

[0033] The enhancer includes the following components in parts by weight: 100 parts of sodium lauryl sulfate.

[0034] Comparative Example 4

[0035] The reinforcing agent includes the following components in parts by weight: 100 parts of sodium sulfate.

[0036] Comparative Example 5

[0037] The reinforcing agent includes the following components in parts by weight: 85 parts of sodium sulfate and 15 parts of sodium α-olefin sulfonate.

[0038] Comparative Example 6

[0039] The enhancer includes the following components in parts by weight: 85 parts of sodium sulfate and 15 parts of sodium dodecyl sulfate.

[0040] Comparative Example 7

[0041] The enhancer comprises the following components in parts by weight: 85 parts of sodium sulfate and 15 parts of lauroyl diethanolamine.

[0042] Comparative Example 8

[0043] The enhancer includes the following components in parts by weight: 70 parts of sodium sulfate, 15 parts of sodium dodecyl sulfate, and 15 parts of sodium α-olefin sulfonate.

[0044] Comparative Example 9

[0045] The enhancer includes the following components in parts by weight: 70 parts of sodium sulfate, 15 parts of sodium dodecyl sulfate, and 15 parts of lauroyl diethanolamine.

[0046] Comparative Example 10

[0047] The enhancer comprises the following components in parts by weight: 70 parts of sodium sulfate, 15 parts of sodium α-olefin sulfonate, and 15 parts of lauroyl diethanolamine.

[0048] Test Example 1

[0049] In order to complete the testing of the embodiments and comparative examples, the basic cement slurry formula selected includes the following components in parts by weight: 100 parts of oil well G grade cement, 44 parts of water, 1 part of fluid loss reducer, and several parts of reinforcing agent.

[0050] In parts by weight, 100 parts of white oil, 3 parts of organic soil, 15 parts of water, 6 parts of calcium chloride, 4 parts of emulsifier 1, 3 parts of emulsifier 2, 7 parts of calcium oxide, and 3.5 parts of oxidized asphalt are mixed to obtain an oil-based drilling fluid.

[0051] The test method is in accordance with the national standard GBT19139-2003 "Test method for oil well cement" to carry out the preparation of cement slurry and the mixing experiment of oil-based drilling fluid and cement slurry. The results are shown in Table 1.

[0052] Table 1

[0053] According to the results in Table 1, after adding 10% of the reinforcing agent to the cement slurry, Examples 1, 2, and 3 show that the cement slurry has good rheological properties after mixing with the oil-based drilling fluid. After thickening at 90°C for half an hour, the slurry is still uniform and stable and has good rheological properties. It has a certain strength after being cured at 75°C for 24 hours, which is conducive to the success rate of plugging. In Comparative Example 1, no reinforcing agent was added, the rheological properties of the cement slurry and the oil-based drilling fluid were poor, and the fluidity was completely lost after thickening at 90°C. The formed slurry had no strength development after being cured at 75°C for 24 hours. In Comparative Examples 2 and 3, sodium α-olefin sulfonate and sodium dodecyl sulfate were added to the cement slurry respectively, and the rheological properties of the mixed fluid did not improve, but became worse. After thickening at 90°C, the fluidity was lost and there was no strength development after curing at 75°C for 24 hours, indicating that the addition of sodium α-olefin sulfonate or sodium dodecyl sulfate alone cannot achieve the purpose of improving the compatibility of cement slurry and oil-based drilling fluid. In Comparative Example 4, 8% sodium sulfate was added to the cement slurry, and the rheological properties of the mixed fluid were significantly improved. After curing at 75°C for 24 hours, a certain strength was developed. However, after thickening at 90°C for half an hour, obvious demulsification occurred, resulting in oil-water separation, affecting the accurate test of the experiment and the smooth progress of the construction. In Comparative Example 5, sodium sulfate and sodium α-olefin sulfonate were added to the cement slurry. Similar to Comparative Example 4, the rheological properties of the mixed fluid were significantly improved. After curing at 75°C for 24 hours, a certain strength was developed. However, after thickening at 90°C for half an hour, obvious demulsification occurred, resulting in oil-water separation, affecting the accurate test of the experiment and the smooth progress of the construction. Comparative Examples 6, 7, 8, 9, and 10 are similar to Comparative Examples 4 and 5. The rheological properties and strength properties of the cement slurry and the oil-based drilling fluid after mixing are good, but there is still the problem of demulsification. This shows that although the rheological properties of the mixed fluid can be improved and the strength can be guaranteed by adding only sodium sulfate, or sodium sulfate and sodium dodecyl sulfate, or sodium sulfate and sodium α-olefin sulfonate, or sodium sulfate, sodium dodecyl sulfate, sodium α-olefin sulfonate, or sodium sulfate, sodium dodecyl sulfate, and lauroyl diethanolamine, or sodium sulfate, sodium α-olefin sulfonate, and lauroyl diethanolamine to the cement slurry, the problem of demulsification of the mixed fluid still exists. Only when sodium sulfate, sodium dodecyl sulfate, sodium α-olefin sulfonate, and lauroyl diethanolamine are all added to the cement slurry in a certain proportion, can the excellent comprehensive performance of the mixed fluid be obtained.

[0054] Finally, it should be noted that the above 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 embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. An enhancer for oil-based drilling fluid plugging cement slurry, characterized in that: The enhancer comprises the following components in parts by weight: 65-80 parts of micro-emulsifier, 7.5-15 parts of hydrophilic emulsifier, 7.5-15 parts of anionic hydrophilic emulsification enhancer, and 5-10 parts of nonionic hydrophilic emulsification enhancer.

2. The enhancer for oil-based drilling fluid plugging cement slurry according to claim 1, characterized in that: The micro-emulsifier is sodium sulfate.

3. The enhancer for oil-based drilling fluid plugging cement slurry according to claim 1, characterized in that: The hydrophilic emulsifier is sodium lauryl sulfate.

4. The enhancer for oil-based drilling fluid plugging cement slurry according to claim 1, characterized in that: The anionic hydrophilic emulsifier is sodium α-olefin sulfonate.

5. The enhancer for oil-based drilling fluid plugging cement slurry according to claim 1, characterized in that: The nonionic hydrophilic emulsifier is lauroyl diethanolamine.

6. The enhancer for oil-based drilling fluid plugging cement slurry according to claim 2, characterized in that: The mesh number of the sodium sulfate is 300-400 meshes.

7. The enhancer for oil-based drilling fluid plugging cement slurry according to claim 1, characterized in that: The components of the reinforcing agent need to be uniformly mixed to obtain the reinforcing agent.

8. The enhancer for oil-based drilling fluid plugging cement slurry according to claim 1, characterized in that: The components of the reinforcing agent are mixed in a powder mixer to obtain the reinforcing agent.

9. The enhancer for oil-based drilling fluid plugging cement slurry according to claim 1, characterized in that: The components of the reinforcing agent need to be mixed in a powder mixer for more than 20 minutes to obtain the reinforcing agent.

10. Use of the enhancer for oil-based drilling fluid plugging cement slurry according to any one of claims 1 to 9 in oil-based drilling fluid plugging cement slurry.

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