High-temperature and high-pressure resistant plugging material for oil-based drilling fluid and preparation method thereof

Abstract

The application relates to the technical field of oil drilling plugging, and particularly discloses an anti-high-temperature and high-pressure plugging material for oil-based drilling fluid and a preparation method thereof, the plugging material comprising 49-60 parts of oil-based bonding plugging agents; 26-39 parts of swelling and toughening particles; and 12-14 parts of fibers; wherein the oil-based bonding plugging agents comprise several kinds of bitumen with different softening points; and the swelling and toughening particles comprise three kinds of rubber particles with different particle sizes. In the application, the bitumen with different softening points forms bonding plugging capacity at high temperature, and then forms rubber bitumen with rubber at high temperature, so that the toughness of a plugging layer is enhanced; finally, the fibers are combined to form a net-shaped plugging layer, which can not only ensure the formation of an initial plugging layer, but also ensure the plugging strength of the plugging layer in a hole and the pressure blocking capacity. The application helps to solve the complex leakage problem of high-temperature and deep-well oil-based drilling fluid, and is suitable for 180 DEG C-200 DEG C well temperature conditions.

Description

Technical Field

[0001] This invention relates to the field of oil well plugging technology, specifically to a high-temperature and high-pressure resistant plugging material for oil-based drilling fluids and its preparation method. Background Technology

[0002] Compared to water-based drilling fluids, oil-based drilling fluids possess advantages such as high-temperature resistance, salt resistance, good lubricity, and strong inhibition, and have been widely used in high-temperature wells, deep wells, and challenging wells. In recent years, frequent leakage has occurred during drilling operations in Jimsar and shale gas fields, particularly due to significant losses of oil-based drilling fluids. In the high-temperature sections of deep wells in the southern margin of Xinjiang, the use of oil-based drilling fluids has led to frequent leakage due to the development of pores and fractures during drilling. Furthermore, the window between formation pressure and leakage pressure is narrow within the same open-hole section, resulting in simultaneous overflow and leakage.

[0003] Currently, most methods for plugging oil-based drilling fluid losses still rely on water-based plugging agents. These agents have poor sealing properties; while they can effectively seal pore throats, their poor sealing density and weak adhesion between materials, especially between the plugging layer and the wellbore, make them prone to backflow when positive or negative pressure is released, leading to plugging failure or secondary losses. Existing oil-based plugging materials are mostly based on oil-based micro-expansion, which can effectively seal fractures and cavities under low-temperature conditions, but their resistance to high temperatures and backflow is weak. Oil-based drilling fluids are commonly used in high-temperature deep wells and complex formations with multiple pressure systems, resulting in persistently high leakage rates. Therefore, it is necessary to develop an oil-based plugging material that minimizes the impact on oil-based drilling fluids while effectively addressing positive and negative pressure differences within fractures and cavities, effectively isolating pressure transmission, and improving the plugging success rate of oil-based drilling fluids in high-temperature deep wells. Summary of the Invention

[0004] Based on this, the present invention proposes a plugging formulation for oil-based drilling fluids suitable for complex formations in high-temperature deep wells, which is applicable to well temperature conditions of 180℃-200℃.

[0005] According to a first aspect of the present invention, a high-temperature and high-pressure resistant plugging material for oil-based drilling fluids is provided, comprising, by weight percentage:

[0006] Oil-based adhesive sealant: 49-60 parts;

[0007] Swelling and toughening granules: 26-39 parts;

[0008] Fiber: 12-14 parts;

[0009] Among them, oil-based adhesive sealants include several types of asphalt with different softening points;

[0010] The swelling and toughening particles comprise three different sizes of rubber particles.

[0011] According to embodiments of the present invention, the oil-based adhesive sealant comprises: asphalt with a softening point of 150°C, asphalt with a softening point of 180°C, asphalt with a softening point of 200°C, and asphalt with a softening point of 220°C.

[0012] The 150℃ softening point asphalt, the 180℃ softening point asphalt, the 200℃ softening point asphalt, and the 220℃ softening point asphalt are all natural modified asphalt or coal tar pitch.

[0013] According to an embodiment of the present invention, the particle size of the 150°C softening point asphalt is 120 mesh;

[0014] The particle size of the 180℃ softening point asphalt is 10-40 mesh;

[0015] The particle size of the 200℃ softening point asphalt is 10-40 mesh.

[0016] The particle size of the 220℃ softening point asphalt is 10-40 mesh.

[0017] According to an embodiment of the present invention, the 150°C softening point asphalt, the 180°C softening point asphalt, the 200°C softening point asphalt, and the 220°C softening point asphalt are uniformly mixed in a mass ratio of 1:1:1:1.

[0018] According to an embodiment of the present invention, the swelling and toughening particles comprise:

[0019] First rubber particles with a particle size of 80-120 mesh, second rubber particles with a particle size of 40-80 mesh, and third rubber particles with a particle size of 10-40 mesh.

[0020] According to an embodiment of the present invention, the first rubber particles, the second rubber particles, and the third rubber particles are uniformly mixed in a mass ratio of 2:3:2.

[0021] According to an embodiment of the present invention, the first rubber particle, the second rubber particle, and the third rubber particle are all one or more of butadiene rubber, styrene-butadiene rubber, nitrile rubber, or ethylene propylene diene monomer (EPDM) rubber.

[0022] According to an embodiment of the present invention, the fiber is one of rock wool fiber, asbestos fiber or sepiolite fiber with a length of 1-3 mm.

[0023] According to a second aspect of the present invention, a method for preparing the above-mentioned sealing material is provided, comprising the following steps:

[0024] The leak-sealing material is obtained by mixing 49-60 parts of oil-based adhesive sealant, 26-39 parts of swelling toughening particles, and 12-14 parts of fiber evenly.

[0025] As can be seen from the above technical solution, the high-temperature and high-pressure resistant plugging material for oil-based drilling fluid and its preparation method provided by the present invention have the following beneficial effects:

[0026] This invention utilizes asphalt with different softening points to form adhesive sealing capabilities at high temperatures, then combines it with rubber at high temperatures to form rubberized asphalt, enhancing the toughness of the sealing layer. Finally, it is combined with fibers to form a mesh-like sealing layer. This ensures both the formation of the initial sealing layer and the sealing strength and pressure barrier capabilities within the pores. It helps solve the complex leakage problem of oil-based drilling fluids in high-temperature deep wells. Detailed Implementation

[0027] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments.

[0028] According to a first aspect of the present invention, a high-temperature and high-pressure resistant plugging material for oil-based drilling fluids is provided, comprising, by weight percentage:

[0029] Oil-based adhesive sealant: 49-60 parts;

[0030] Swelling and toughening granules: 26-39 parts;

[0031] Fiber: 12-14 parts;

[0032] Among them, oil-based adhesive sealants include several types of asphalt with different softening points;

[0033] The swelling and toughening particles consist of rubber particles of three different sizes.

[0034] This invention provides a high-temperature, high-pressure plugging material for oil-based drilling fluids. This material is suitable for well temperatures of 180℃-200℃, and its main raw materials are an oil-based binder / plugging agent, swelling and toughening particles, and high-temperature resistant fibers. The oil-based binder / plugging agent uses asphalt with different softening points to achieve three states and corresponding functions at different well temperatures: First, softened asphalt can penetrate the oil-based mud cake, making the plugging layer tightly connected to the well wall and mud cake, and can encapsulate all materials, increasing the overall integrity of the plugging layer; second, near-softening-point asphalt is in a colloidal state, binding the various materials in the plugging layer together, enhancing the overall bonding strength; third, unsoftened asphalt can act as a bridging material to achieve initial plugging. Swellable toughening particles are rubber particles of varying sizes that undergo a swelling reaction in asphalt at high temperatures, forming a tough rubber asphalt. This rubber asphalt possesses properties such as high-temperature stability, low-temperature flexibility, anti-aging properties, and fatigue resistance, effectively absorbing stress and blocking pressure transmission. Furthermore, particles of different sizes can be combined with different asphalt particles to form particle mixes, facilitating initial sealing and promoting the initial formation of the sealing layer. High-temperature resistant fibers are used to form a mesh-like sealing layer, enhancing the overall toughness of the sealing layer.

[0035] The oil-based drilling fluid high-temperature and high-pressure plugging material provided by this invention is based on the principle of using asphalt with different softening points to form a bonding and plugging ability at high temperature, and then forming rubber asphalt with rubber at high temperature to enhance the toughness of the plugging layer. Finally, it is combined with fibers to form a mesh plugging layer, which can not only ensure the formation of the initial plugging layer, but also ensure the plugging strength and pressure barrier ability of the plugging layer in the hole.

[0036] The bonding and plugging principle of oil-based adhesives is as follows: Different softening point asphalts are used to achieve three states and corresponding functions at different well temperatures. First, asphalt with a softening point below the well temperature softens at the well temperature, allowing it to penetrate the oil-based mud cake, ensuring a tight bond between the plugging layer and the wellbore and the mud cake, and encapsulating all materials, increasing the overall integrity of the plugging layer. Second, asphalt with a softening point close to the well temperature is in a gel-like state, binding the various materials in the plugging layer together and enhancing overall bonding strength. Third, asphalt with a softening point above the well temperature can act as a bridging material, achieving initial plugging.

[0037] The toughening principle of swelling toughening particles is that rubber particles of different sizes undergo a swelling reaction in high-temperature asphalt to form rubber asphalt with strong toughness. Rubber asphalt has properties such as high-temperature stability, low-temperature flexibility, anti-aging, and fatigue resistance, and can effectively absorb stress and block pressure transmission.

[0038] According to embodiments of the present invention, the oil-based adhesive sealant comprises: asphalt with a softening point of 150°C, asphalt with a softening point of 180°C, asphalt with a softening point of 200°C, and asphalt with a softening point of 220°C.

[0039] Asphalt with a softening point of 150℃, 180℃, 200℃, and 220℃ is all natural modified asphalt or coal tar pitch.

[0040] According to an embodiment of the present invention, the particle size of the asphalt with a softening point of 150°C is 120 mesh;

[0041] The particle size of asphalt with a softening point of 180℃ is 10-40 mesh.

[0042] The particle size of asphalt with a softening point of 200℃ is 10-40 mesh.

[0043] The particle size of asphalt with a softening point of 220℃ is 10-40 mesh.

[0044] According to an embodiment of the present invention, asphalt with a softening point of 150°C, asphalt with a softening point of 180°C, asphalt with a softening point of 200°C, and asphalt with a softening point of 220°C are uniformly mixed in a mass ratio of 1:1:1:1.

[0045] According to an embodiment of the present invention, the swelling and toughening particles comprise:

[0046] First rubber particles with a particle size of 80-120 mesh, second rubber particles with a particle size of 40-80 mesh, and third rubber particles with a particle size of 10-40 mesh.

[0047] According to an embodiment of the present invention, the first rubber particles, the second rubber particles, and the third rubber particles are uniformly mixed in a mass ratio of 2:3:2.

[0048] According to an embodiment of the present invention, the first rubber particle, the second rubber particle, and the third rubber particle are all one or more of butadiene rubber, styrene-butadiene rubber, nitrile rubber, or ethylene propylene diene monomer (EPDM) rubber.

[0049] According to an embodiment of the present invention, the fiber is either rock wool fiber or sepiolite fiber with a length of 1-3 mm.

[0050] According to a second aspect of the present invention, a method for preparing the above-mentioned sealing material is provided, comprising the following steps:

[0051] Mix 49-60 parts of oil-based adhesive sealant, 26-39 parts of swelling toughening granules, and 12-14 parts of fiber evenly to obtain the leak-sealing material.

[0052] The technical solution of the present invention will be described in detail below through preferred embodiments. It should be noted that the specific embodiments in the following text are for illustrative purposes only and are not intended to limit the present invention.

[0053] Example 1

[0054] A leak-stopping formula for oil-based drilling fluid with anti-backflow properties is obtained by mixing 49 parts of oil-based binder and plugging agent, 39 parts of swelling toughening particles, and 12 parts of fiber evenly.

[0055] Example 2

[0056] A leak-stopping formulation for oil-based drilling fluid with anti-backflow properties is obtained by mixing 60 parts of oil-based binder and plugging agent, 26 parts of swelling and toughening particles, and 14 parts of fiber evenly.

[0057] Example 3

[0058] A leak-stopping formulation for oil-based drilling fluid with anti-backflow properties is obtained by mixing 56 parts of oil-based binder and plugging agent, 31 parts of swelling toughening particles, and 13 parts of fiber evenly.

[0059] Comparative Example 1

[0060] BZ-SDL type leak sealing material is mainly composed of nut shell materials and plant fibers.

[0061] Comparative Example 2

[0062] BH-SRC Type I sealing material is mainly composed of limestone and mineral fibers.

[0063] The selection of the proportion is mainly based on the two major categories of bridging and sealing agents commonly used at present: one is plant-based materials, and the other is mineral-based materials.

[0064] Experimental Example 1: Impact Test on Oil-Based Drilling Fluids

[0065] Test method for the impact on oil-based drilling fluid: After hot rolling the field base slurry and the field slurry with added plugging material at 180℃-200℃ for 16h, test the six-speed, demulsification voltage and high-temperature high-pressure filtration loss. Compare the data and calculate the data growth rate according to formula (1). The data growth rate includes the growth rate of apparent viscosity, the growth rate of demulsification voltage and the growth rate of filtration loss. The corresponding data are apparent viscosity, demulsification voltage and filtration loss.

[0066] The data growth rate W is calculated as shown in equation (1):

[0067]

[0068] In the formula:

[0069] W – Data growth rate, expressed as a percentage (%);

[0070] D1—Field grout test data;

[0071] D2 – On-site grout test data with added sealing material.

[0072] The following tests were conducted using the respective formulations:

[0073] 1#: Field base mud: Oil-based mud from Tianwan 2 well in the southern edge of the well. 2#: Field base mud + 5% oil-based drilling fluid high-temperature and high-pressure resistant plugging material (Example 1). 3#: Field base mud + 5% oil-based drilling fluid high-temperature and high-pressure resistant plugging material (Example 2). 4#: Field base mud + 5% oil-based drilling fluid high-temperature and high-pressure resistant plugging material (Example 3). 5#: Field base mud + 5% BZ-SDL (Comparative Example 1).

[0074] 6#: On-site base grout + 5% BH-SRC Type I (Comparative Example 2)

[0075] The test results are shown in Tables 1 to 3.

[0076] Table 1: Effect of Examples 1-3 and Comparative Examples on Oil-Based Drilling Fluid After Rolling at 180℃

[0077]

[0078] Table 2: Effect of Examples 1-3 and Comparative Examples on Oil-Based Drilling Fluid After Rolling at 190℃

[0079]

[0080] Table 3: Effect of Examples 1-3 and Comparative Examples on Oil-Based Drilling Fluid After Rolling at 200℃

[0081]

[0082]

[0083] Data from Tables 1-3 show that: Examples 1-3, at 180℃-200℃, with an addition of 5%, have a slight effect on the viscosity of oil-based drilling fluids, but this effect is negligible (less than 20%). It significantly reduces filtration loss, increases demulsification voltage, and improves the filtration performance and stability of the drilling fluid. Comparative examples BZ-SDL and BH-SRC Type I have a smaller effect on apparent viscosity, but they reduce demulsification voltage, increase high-temperature filtration loss, and have a slightly greater impact on the filtration performance and stability of oil-based drilling mud.

[0084] Experiment Example 2: Forward High Temperature Pressure Bearing Capacity Test

[0085] The CDL-Ⅱ type high-temperature and high-pressure dynamic and static leak-stopping test device and 1-3mm wedge plates were used for testing. The wedge plates were self-made wedge-shaped cement cores, with the 3mm end facing the vessel containing the test slurry and the 1mm end facing the outlet. The test formulas were the base slurry and formulas 7# to 11#. First, the outlet was closed, and the #1# field base slurry was pressure filtered at 2MPa for 30 minutes to allow the slurry to seep into the wedge plate. Then, the pressure was released and the #1# field base slurry was drained. Next, the test leak-stopping slurry (i.e., #7#-11# slurry) was added and pressurized. The highest pressure during the process of reaching a leakage of 800mL was recorded as the positive high-temperature pressure-bearing capacity. If the leakage was still less than 800mL when the pressure was increased to 20MPa, the positive high-temperature pressure-bearing capacity was recorded as ≥20MPa. The test results are shown in Table 4.

[0086] #1: On-site mud: Oil-based mud from well Tianwan 2 in the southern edge of the well.

[0087] 7#: High-temperature and high-pressure resistant plugging material for field-based slurry + 5% oil-based drilling fluid (Example 1)

[0088] #8: High-temperature and high-pressure resistant plugging material for field-based slurry + 5% oil-based drilling fluid (Example 2)

[0089] 9#: High-temperature and high-pressure resistant plugging material for field-based slurry + 5% oil-based drilling fluid (Example 3)

[0090] 10#: On-site base grout + 5% BZ-SDL (Comparative Example 1)

[0091] 11#: On-site base grout + 5% BH-SRC Type I (Comparative Example 2)

[0092] Table 4: Positive High-Temperature Pressure Bearing Capacity Tests of Examples 1-3 and Comparative Examples

[0093]

[0094]

[0095] As shown in Table 4, the positive pressure bearing capacity of the embodiments is greater than 15MPa under conditions of 180℃-200℃, exhibiting very high positive pressure bearing capacity. The comparative example BZ-SDL has poor temperature resistance and relatively poor positive pressure bearing capacity; the BH-SRC I type has good positive pressure bearing capacity, but it is slightly lower than that of the embodiments of the present invention.

[0096] Experiment Example 3: Reverse High Temperature Pressure Bearing Capacity Test

[0097] Reverse high-temperature pressure bearing capacity test method: The forward pressure bearing capacity test method is adopted. After the test slurry is pressurized to 10MPa at the corresponding temperature (Note: 4MPa is used in this step because the forward pressure bearing capacity of No. 10 cannot reach 10MPa), the core containing the sealing layer is completely removed, and the core is placed in the holder in the reverse direction, that is, the placement direction is: 1mm port facing the vessel containing the test slurry, and 3mm port facing the liquid outlet. Then, No. 1 base slurry is added for pressure testing, and the highest pressure during the pressure drop is recorded as its reverse high-temperature pressure bearing capacity. The test results are shown in Table 5.

[0098] Table 5: Reverse High-Temperature Pressure Bearing Capacity Tests of Examples 1-3 and Comparative Examples

[0099]

[0100] The data in Table 5 show that the reverse pressure resistance of the examples is greater than 7 MPa under the conditions of 180℃-200℃, which can effectively cope with the complex leakage of oil-based mud. The comparative examples BZ-SDL and BH-SRC I leaked under the initial pressure of 2 MPa, and had poor reverse pressure resistance.

[0101] The above experimental examples demonstrate that the high-temperature and high-pressure plugging material for oil-based drilling fluid of the present invention has high positive and reverse pressure bearing capacity in high-temperature wells at 180℃-200℃.

[0102] Experiment Example 4: High-Temperature Pressure Bearing Capacity Test of 3mm-8mm Joint Board

[0103] The high-temperature and high-pressure sealing material for oil-based drilling fluid of the present invention can also be mixed with large-particle limestone particles to seal larger cracks and cavities.

[0104] The forward and reverse bearing capacity of the following formulations were tested using the methods of Experimental Example 2 and Experimental Example 3. For formulations 12# and 13#, 3mm-5mm wedge plates were used, and for formulations 14# and 15#, 5mm-8mm wedge plates were used.

[0105] 12#: On-site base slurry + 5% oil-based drilling fluid high-temperature and high-pressure sealing material (Example 1) + 5% limestone particles (3mm-5mm) + 3% limestone particles (1mm-3mm)

[0106] #13: On-site base grout + 5% BH-SRC Type I + 5% limestone particles (3mm-5mm) + 3% limestone particles (1mm-3mm)

[0107] 14#: On-site base slurry + 5% oil-based drilling fluid high-temperature and high-pressure sealing material (Example 1) + 5% limestone particles (5mm-8mm) + 8% limestone particles (3mm-5mm) + 3% limestone particles (1mm-3mm)

[0108] 15#: On-site base grout + 5% BH-SRC Type I + 5% limestone particles (5mm-8mm) + 8% limestone particles (3mm-5mm) + 3% limestone particles (1mm-3mm)

[0109] The test results are shown in Tables 6 and 7.

[0110] Table 6: Test of the positive high-temperature compressive strength of 12#-15# slurry

[0111]

[0112] Table 7: Reverse High-Temperature Pressure Bearing Capacity Test of 12#-15# Grout

[0113]

[0114] Data from Tables 5 and 6 show that a high-temperature and high-pressure plugging material for oil-based drilling fluid, when mixed with limestone particles, exhibits a positive pressure bearing capacity ≥10MPa and a reverse pressure bearing capacity greater than 5MPa in 3-8mm cracks under 180℃-200℃ conditions. This effectively addresses complex leakage caused by the uptake and discharge of oil-based drilling mud. Compared with the formulation of BH-SRC I mixed with limestone, it also shows significant advantages in both positive and reverse pressure bearing capacity.

[0115] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above descriptions are merely specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A high-temperature and high-pressure resistant leak sealing material for oil-based drilling fluid, characterized by, By weight percentage, including: Oil-based adhesive sealant: 49-60 parts; Swelling and toughening granules: 26-39 parts; Fiber: 12-14 parts.

2. The high-temperature and high-pressure resistant plugging material for oil-based drilling fluid according to claim 1, characterized in that, Oil-based adhesive sealants include: asphalt with a softening point of 150℃, asphalt with a softening point of 180℃, asphalt with a softening point of 200℃, and asphalt with a softening point of 220℃. The 150℃ softening point asphalt, the 180℃ softening point asphalt, the 200℃ softening point asphalt, and the 220℃ softening point asphalt are all natural modified asphalt or coal tar pitch.

3. The high-temperature and high-pressure resistant plugging material for oil-based drilling fluid according to claim 2, characterized in that, The particle size of the 150℃ softening point asphalt is 120 mesh. The particle size of the 180℃ softening point asphalt is 10-40 mesh; The particle size of the 200℃ softening point asphalt is 10-40 mesh. The particle size of the 220℃ softening point asphalt is 10-40 mesh.

4. The high-temperature and high-pressure resistant plugging material for oil-based drilling fluid according to claim 2, characterized in that, The 150℃ softening point asphalt, the 180℃ softening point asphalt, the 200℃ softening point asphalt, and the 220℃ softening point asphalt are uniformly mixed in a mass ratio of 1:1:1:

1.

5. The high-temperature and high-pressure resistant plugging material for oil-based drilling fluid according to claim 1, characterized in that, The swelling and toughening particles include: First rubber particles with a particle size of 80-120 mesh, second rubber particles with a particle size of 40-80 mesh, and third rubber particles with a particle size of 10-40 mesh.

6. The high-temperature and high-pressure resistant plugging material for oil-based drilling fluids according to claim 5, characterized in that, The first rubber particles, the second rubber particles, and the third rubber particles are uniformly mixed in a mass ratio of 2:3:

2.

7. The high-temperature and high-pressure resistant plugging material for oil-based drilling fluids according to claim 5, characterized in that, The first rubber particle, the second rubber particle, and the third rubber particle are all one or more of butadiene rubber, styrene-butadiene rubber, nitrile rubber, or ethylene propylene diene monomer (EPDM) rubber.

8. The high-temperature and high-pressure resistant plugging material for oil-based drilling fluid according to claim 1, characterized in that, The fiber is one of rock wool fiber, asbestos fiber or sepiolite fiber with a length of 1-3 mm.

9. A method for preparing a high-temperature and high-pressure resistant plugging material for oil-based drilling fluids according to any one of claims 1-8, characterized in that, Includes the following steps: The leak-sealing material is obtained by mixing 49-60 parts of oil-based adhesive sealant, 26-39 parts of swelling toughening particles, and 12-14 parts of fiber evenly.

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