Bed development mud shale corrosion agent as well as preparation method and application thereof

Abstract

The invention discloses a bedding development mud shale corrosion agent as well as a preparation method and application thereof, pentasodium diethylenetriamine pentaacetate and ethylene glycol are mixed according to a mass ratio and uniformly stirred, and the bedding development mud shale corrosion agent is prepared. In the stratification development mud shale corrosion agent, the mass ratio of the pentasodium diethylenetriamine pentaacetate to the ethylene glycol is (1-9): 0.16. According to the stratification development mud shale corrosion agent and the preparation method thereof, through the synergistic effect between the main corrosion agent and the auxiliary corrosion agent, the obvious corrosion effect is shown, the mass of a shale sample can be reduced, and meanwhile the obvious destructive effect on the structural strength of shale is achieved.

Description

Technical Field

[0001] The present invention relates to the field of mud shale exploration, in particular to a dissolving agent for mud shale with developed bedding, a preparation method of the dissolving agent for mud shale with developed bedding, and an application of the dissolving agent for mud shale with developed bedding, belonging to the technical field of drilling dissolving agents. Background Art

[0002] Currently, drilling horizontal shale gas wells in China (for example, the Longmaxi shale gas well) is plagued by frequent incidents such as wellbore instability, blockage, stuck pipe, and pipe jamming. Statistics show that since 2014, 45 rotary steerable tools have been deployed in the Sichuan and Chongqing regions, resulting in significant economic losses. Since the widespread use of oil-based mud in 2016, 41 of these tools have been deployed, resulting in a 7.75% deployment rate. These tools are located in the Changning-Zhaotong, Weiyuan, and Zigong blocks. In complex rotary steerable wells, stuck pipe incidents typically occur in the horizontal section, primarily due to shale blockage. Currently, shale blockage and stuck pipe incidents are difficult to address, with limited options. Mechanical methods such as jarring and undercutting are time-consuming, costly, and have a low success rate. Conventional de-stuck agents, conventional hydrochloric acid, earth acid, and oil soaking are ineffective in removing stuck pipe incidents. In particular, these tools are not suitable for shale formations characterized by high quartz content, well-developed bedding, and high brittleness.

[0003] There are several types of stuck-drilling fluids: oil-soaked, oil-in-water, inorganic salt, and acid-soaked. These methods, collectively known as the stuck-drilling fluid method, are simple and effective ways to address various types of stuck drill bits. Specifically, the fluid is pumped into the well, allowing it to soak at the stuck point, reducing the friction coefficient of the filter cake. The fluid then moves the drill string while soaking, releasing the stuck drill bit.

[0004] Each of the above stuck-well fluids has its own advantages and disadvantages, but also has certain limitations. Soaking oil, because it is relatively light and easily rises, cannot effectively soak the stuck point, resulting in relatively poor sticking-well removal. Oil can also damage the mud cake, destabilizing the wellbore, and improper handling can cause complex casing. Oil-in-water stuck-well fluids are low-cost and less polluting, but their effectiveness is much worse than soaking oil. Inorganic salt stuck-well fluids are only suitable for use in brine drilling fluid systems. Soaking acid can only be used for stuck drill bits in carbonate formations, and acid is corrosive to the drill bit.

[0005] In summary, the field urgently needs a new type of de-stuck fluid suitable for shale gas development, especially for shale formations with high quartz content, well-developed bedding, and high brittleness. Summary of the Invention

[0006] The purpose of this section is to summarize some aspects of the embodiments of the present invention and briefly introduce some preferred embodiments. Some simplifications or omissions may be made in this section and the abstract and title of this application to avoid obscuring the purpose of this section, the abstract and the title of the invention, and such simplifications or omissions should not be used to limit the scope of the present invention.

[0007] In view of the above problems and / or the problems existing in the prior art, the present invention is proposed.

[0008] The primary purpose of the present invention is to overcome the problems existing in the prior art and provide a shale dissolving agent with developed bedding, which can be used to unblock shale formations with high quartz content, developed bedding, and high brittleness.

[0009] To solve the above technical problems, the present invention provides the following technical solution: a bedding-developed mud shale dissolution agent, comprising: pentasodium diethylenetriamine pentaacetate and ethylene glycol; wherein, in terms of mass ratio, the mass ratio of pentasodium diethylenetriamine pentaacetate and ethylene glycol is (1-9):0.16.

[0010] As a preferred embodiment of the present invention, the mass ratio of pentasodium diethylenetriamine pentaacetate to ethylene glycol is (3-6):0.16.

[0011] As a preferred embodiment of the present invention, the mass ratio of pentasodium diethylenetriamine pentaacetate to ethylene glycol is 3:0.16.

[0012] As a preferred embodiment of the present invention, the mass ratio of pentasodium diethylenetriamine pentaacetate to ethylene glycol is 4:0.16.

[0013] As a preferred embodiment of the present invention, the mass ratio of pentasodium diethylenetriamine pentaacetate to ethylene glycol is 6:0.16.

[0014] Another object of the present invention is to overcome the problems existing in the prior art and provide a method for preparing a shale dissolving agent with developed bedding. The prepared dissolving agent can be used to release stuck shale formations with high quartz content, developed bedding, and high brittleness.

[0015] To solve the above technical problems, the present invention provides a method for preparing a dissolving agent for shale with developed bedding, comprising: mixing pentasodium diethylenetriamine pentaacetate and ethylene glycol according to a mass ratio, stirring uniformly, and preparing the dissolving agent.

[0016] As a preferred embodiment of the present invention, the mass ratio of pentasodium diethylenetriamine pentaacetate to ethylene glycol is (1-9):0.16.

[0017] As a preferred embodiment of the present invention, the mass ratio of pentasodium diethylenetriamine pentaacetate to ethylene glycol is (3-6):0.16.

[0018] As a preferred embodiment of the present invention, the mass ratio of pentasodium diethylenetriamine pentaacetate to ethylene glycol is 3:0.16.

[0019] As a preferred embodiment of the present invention, the mass ratio of pentasodium diethylenetriamine pentaacetate to ethylene glycol is 4:0.16.

[0020] As a preferred embodiment of the present invention, the mass ratio of pentasodium diethylenetriamine pentaacetate to ethylene glycol is 6:0.16.

[0021] Another object of the present invention is to overcome the problems existing in the prior art and provide an application of a shale dissolver with developed bedding, which is used to unblock shale formations with the characteristics of high quartz content, developed bedding, and high brittleness.

[0022] In order to solve the above technical problems, the application of the bedding-developed mud shale dissolver of the present invention includes: using the bedding-developed mud shale dissolver in the unstuck fluid for shale gas development.

[0023] Compared with the prior art, the present invention has achieved the following beneficial effects: through the synergistic effect between the main and auxiliary dissolving agents, it exhibits a more superior dissolving effect, which not only reduces the weight of the shale sample, but also has a significant destructive effect on the structural strength of the shale, and has a good unblocking effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for describing the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. Those skilled in the art can also derive other drawings based on these drawings without inventive effort. Among them:

[0025] Figure 1 This is a diagram showing the compression test results of dissolved shale in Example 1 of the present invention;

[0026] Figure 2 This is a diagram showing the compression test results of the dissolved shale in Comparative Example 1 of the present invention;

[0027] Figure 3 This is a diagram showing the compression test results of the dissolved shale in Comparative Example 2 of the present invention;

[0028] Figure 4 This is a graph showing the compression test results of shale dissolved by auxiliary dispersant under KOH in the present invention;

[0029] Figure 5 This is a graph showing the compressive strength test results of shale dissolution with the auxiliary dispersant DTPA 5Na of the present invention. DETAILED DESCRIPTION

[0030] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are described in detail below in conjunction with the embodiments of the specification.

[0031] In the following description, many specific details are set forth to facilitate a full understanding of the present invention. However, the present invention may also be implemented in other ways different from those described herein. Those skilled in the art may make similar generalizations without violating the connotation of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0032] Secondly, the term "one embodiment" or "embodiment" herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The phrase "in one embodiment" appearing in various places throughout this specification does not necessarily refer to the same embodiment, nor does it refer to a separate or selective embodiment that is mutually exclusive of other embodiments.

[0033] (1) Dissolution rate test

[0034] The residual shale sample after dissolution was dried at 150 °C for more than 4 h to constant weight, weighed, and the dissolution rate was calculated.

[0035] (2) Dissolution shale compression strength test

[0036] Tested by high, low temperature and high pressure triaxial rock mechanics testing device.

[0037] Experimental steps: In order to simulate the load required for breaking a block after it falls into the wellbore and gets stuck, it is planned to load it in the direction perpendicular to the bedding of the shale to test its crushing strength.

[0038] The uniaxial compressive strength and softening coefficient of rock should be calculated according to the following formulas:

[0039] R=P / A

[0040] Where: R—uniaxial compressive strength of rock, MPa;

[0041] P—destruction load, N;

[0042] A—cross-sectional area of ​​specimen, mm 2 .

[0043] Preparation of the medicine of the present invention:

[0044] Pentasodium diethylenetriamine pentaacetate, also known as DTPA 5Na, was obtained from Kunshan Jincheng Reagent; potassium hydroxide was obtained from Shanghai Lingfeng Chemical Reagent; tetramethylammonium hydroxide, also known as TMAH, was obtained from Shanghai Macklin; ethylenediamine, also known as EDP; polyethyleneimine, was obtained from Aladdin Reagent; triethanolamine, was obtained from Shanghai Sinopharm Group; sodium allyl sulfonate, was obtained from Aladdin Reagent; hydrogen peroxide, was obtained from Shanghai Sinopharm Group; aminotriacetic acid, also known as NTA, was obtained from Shanghai Macklin; ethylene glycol, was obtained from Aladdin Reagent.

[0045] Sample collection and rock sample processing:

[0046] The collected dark brown mud shale core was cut into a length and width of 2.3 to 2.5 cm by a core end cutting machine, and then polished into a rectangular block with a thickness of about 1.0 cm by sandpaper.

[0047] Example 1

[0048] (1) Specific ratio of main and auxiliary etching agents: diethylenetriamine pentaacetic acid pentasodium DTPA 5Na and ethylene glycol EG are mixed in a mass ratio of 6:0.16 and stirred evenly to prepare an etching agent;

[0049] (2) The processed shale core was immersed in a dissolving agent at 110°C for 72 h, and the strength and compression tests and dissolution rate tests were performed on the dissolved shale.

[0050] (3) When the main dissolving agent is DTPA 5Na and the auxiliary dissolving agent is ethylene glycol, the compressive strength of the shale after dissolution is 60% when the deformation is 6.45 MPa, and the dissolution rate is 61.01%. The compressive strength results are shown in Figure 1 .

[0051] Example 2

[0052] (1) Specific ratio of main and auxiliary etching agents: diethylenetriamine pentaacetic acid pentasodium DTPA 5Na and ethylene glycol EG are mixed in a mass ratio of 3:0.16 and stirred evenly to prepare an etching agent;

[0053] (2) The processed shale core was immersed in a dissolving agent at 110°C for 72 h, and the strength and compression tests and dissolution rate tests were performed on the dissolved shale.

[0054] (3) When the main dissolving agent is DTPA 5Na and the auxiliary dissolving agent is ethylene glycol, the compressive strength of the shale after dissolution is 17.21 MPa when the deformation is 60%, and the dissolution rate is 36.42%.

[0055] Example 3

[0056] (1) Specific ratio of main and auxiliary etching agents: diethylenetriamine pentaacetic acid pentasodium DTPA 5Na and ethylene glycol EG are mixed in a mass ratio of 1:0.16 and stirred evenly to prepare an etching agent;

[0057] (2) The processed shale core was immersed in a dissolving agent at 110°C for 72 h, and the strength and compression tests and dissolution rate tests were performed on the dissolved shale.

[0058] (3) When the main dissolving agent is DTPA 5Na and the auxiliary dissolving agent is ethylene glycol, the compressive strength of the shale after dissolution is 26.21 MPa when the deformation is 60%, and the dissolution rate is 14.62%.

[0059] Comparative Example 1

[0060] (1) The processed shale core was immersed in DTPA 5Na solution at 110℃ for 72h, and the strength and compression test and dissolution rate test were carried out on the dissolved shale.

[0061] (3) After DTPA 5Na dissolution, the compressive strength of shale is 38.90 MPa when the deformation is 60%, and the dissolution rate is 39.13%. The compressive strength results are shown in Figure 2 .

[0062] Comparative Example 2

[0063] (1) The processed shale core was immersed in ethylene glycol (EG) solution at 110 °C for 72 h, and the strength and compression tests and dissolution rate tests were performed on the dissolved shale.

[0064] (3) After ethylene glycol EG dissolution, the compressive strength of shale when the deformation is 60% is 86.62MPa, and the dissolution rate is 4.50%. The compressive strength results are shown in Figure 3 .

[0065] Comparative Example 3

[0066] The main dissolving agent is DTPA 5Na or KOH, which is compounded with different auxiliary dissolving agents. The mass ratio of the main dissolving agent to the auxiliary dissolving agent is 6:0.16. The compressive strength and dissolution rate tests are carried out. The processed shale core is immersed in the dissolving agent at 110℃ for 72h, and the strength and compressive strength tests and dissolution rate tests are carried out on the dissolved shale.

[0067] Table 1 Shale dissolution rate under different main and auxiliary dissolving agents

[0068]

[0069]

[0070] The shale dissolution rates were calculated for shale with DTPA 5Na or KOH as the primary dissolving agent and ethylene glycol, aminotriacetic acid, polyethyleneimine, triethanolamine, hydrogen peroxide, and sodium allylsulfonate as the auxiliary dissolving agents. The results showed that ethylene glycol and polyethyleneimine had a significant dissolving effect on shale and the effect remained basically consistent.

[0071] The compressive test results of shale dissolved by various auxiliary solvents with KOH as the main solvent are shown in Figure 4 The main solvent is DTPA 5Na. The compressive test results of shale dissolved by various auxiliary solvents are shown in Figure 5 .

[0072] The test results show that when the main dissolving agent is KOH, the auxiliary dissolving agents are ethylene glycol, polyethyleneimine, triethanolamine, sodium allyl sulfonate, aminotriacetic acid and hydrogen peroxide, and the corresponding shale crushing strength after dissolution is 26MPa, 16MPa, 15MPa, 19MPa, 12MPa and 14MPa respectively.

[0073] When the main solvent is DTPA 5Na, the auxiliary solvents are ethylene glycol, polyethyleneimine, triethanolamine, sodium allyl sulfonate, aminotriacetic acid and hydrogen peroxide, and the corresponding shale crushing strength after dissolution is 6MPa, 11MPa, 24MPa, 25MPa, 17MPa and 14MPa, respectively.

[0074] Comparing the crushing compressive strength of shale after dissolution with different primary and secondary solvents, DTPA 5Na showed a stronger dissolution effect when the primary solvent was DTPA 5Na. Meanwhile, when DTPA 5Na was the primary solvent, the compressive strength of shale after dissolution with ethylene glycol and polyethyleneimine was lower, at 6 MPa and 11 MPa, respectively.

[0075] Comparative Example 4

[0076] The pressure at which the deformation reaches 50% is taken as the crushing compressive strength of the shale. The crushing compressive strength of the shale after dissolution at different temperatures is compared. At 50°C, the compressive strength of the shale after dissolution by DTPA 5Na, KOH, TMAH, diethylene, and ethylenediamine are approximately 10MPa, 30MPa, 50MPa, 70MPa, and 80MPa, respectively.

[0077] At 110℃, the compressive strength of shale after dissolution by five dissolving agents, DTPA 5Na, KOH, TMAH, diethylene, and ethylenediamine, are approximately 5MPa, 15MPa, 30MPa, 65MPa, and 75MPa, respectively.

[0078] The results show that the compressive strength of the dissolved shale decreases significantly with increasing temperature, and the dissolution effects of KOH and DTPA 5Na are the most obvious.

[0079] Comparing the dissolution effects of the main solvents before and after shale is soaked in oil-based drilling fluid, at a temperature of 110°C after oil immersion, the compressive strength of the shale after dissolution by the five solvents DTPA5Na, KOH, TMAH, diethylene, and ethylenediamine are approximately 2MPa, 10MPa, 32MPa, 22MPa, and 45MPa, respectively.

[0080] The results show that KOH and DTPA 5Na dissolving agents have a synergistic effect with oil-based drilling fluids. The compressive strength of the shale after oil immersion is further reduced compared with that before oil immersion, indicating that oil immersion can enhance the dissolution effect of the dissolving agents. The dissolution effect of the dissolving agents increases by 30% and 60%, respectively. However, the compressive strength of the shale dissolved by TMAH after oil immersion does not decrease but increases, indicating that the dissolution effect of the dissolving agent is inhibited after oil immersion.

[0081] Table 2 Shale dissolution rate of main solvent at different temperatures and before and after oil immersion

[0082]

[0083] The present invention provides a shale dissolving agent and a preparation method thereof. Through the synergistic effect between the main and auxiliary dissolving agents, the agent exhibits a significant dissolving effect, which can not only reduce the weight of the shale sample but also significantly damage the structural strength of the shale.

[0084] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present invention, and all of these should be included in the scope of the present invention.

Claims

1. A dissolving agent for shale with developed bedding, characterized in that: include: Pentasodium diethylenetriamine pentaacetate and ethylene glycol; wherein, by mass ratio, the mass ratio of pentasodium diethylenetriamine pentaacetate and ethylene glycol is (1-9):0.

16.

2. The bedding-developed shale dissolution agent according to claim 1, characterized in that: In terms of mass ratio, the mass ratio of diethylenetriamine pentaacetic acid pentasodium and ethylene glycol is (3-6):0.

16.

3. The bedding-developed shale dissolution agent according to claim 2, characterized in that: In terms of mass ratio, the mass ratio of pentasodium diethylenetriamine pentaacetate and ethylene glycol is 3:0.

16.

4. The bedding-developed shale dissolution agent according to claim 2, characterized in that: In terms of mass ratio, the mass ratio of pentasodium diethylenetriamine pentaacetate and ethylene glycol is 4:0.

16.

5. The bedding-developed shale dissolution agent according to claim 2, characterized in that: In terms of mass ratio, the mass ratio of pentasodium diethylenetriamine pentaacetate and ethylene glycol is 6:0.

16.

6. A method for preparing a dissolving agent for shale with developed bedding, characterized in that: include: Pentasodium diethylenetriamine pentaacetate and ethylene glycol are mixed according to a mass ratio and stirred evenly to prepare a dissolving agent.

7. The method for preparing a dissolving agent for shale with developed bedding according to claim 1, characterized in that: In terms of mass ratio, the mass ratio of diethylenetriamine pentaacetic acid pentasodium and ethylene glycol is (1-9):0.

16.

8. The method for preparing a dissolving agent for shale with developed bedding according to claim 7, characterized in that: In terms of mass ratio, the mass ratio of diethylenetriamine pentaacetic acid pentasodium and ethylene glycol is (3-6):0.

16.

9. The method for preparing a dissolving agent for shale with developed bedding according to claim 7, characterized in that: In terms of mass ratio, the mass ratio of pentasodium diethylenetriamine pentaacetate and ethylene glycol is 3:0.

16.

10. The method for preparing a dissolving agent for shale with developed bedding according to claim 7, characterized in that: In terms of mass ratio, the mass ratio of pentasodium diethylenetriamine pentaacetate and ethylene glycol is 4:0.

16.

11. The method for preparing a dissolving agent for shale with developed bedding according to claim 7, characterized in that: In terms of mass ratio, the mass ratio of pentasodium diethylenetriamine pentaacetate and ethylene glycol is 6:0.

16.

12. Use of the dissolving agent for shale with developed bedding according to any one of claims 1 to 5, characterized in that: include: The bedding-developed mud shale dissolver is used in the unstuck fluid for shale gas development.

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