Plugging agent as well as preparation method and application thereof

Abstract

The invention discloses a plugging agent as well as a preparation method and application thereof, and belongs to the technical field of chemical materials. The plugging agent is prepared from flaky polyethylene glycol terephthalate and at least one anchor type material compounded in the flaky polyethylene glycol terephthalate. The plugging agent facilitates delivery of a rigid anchor material to a leak passage without plugging a pipeline. Due to the fact that the strength of the sheet-shaped polyethylene glycol terephthalate is far smaller than that of the anchor type material, after the sheet-shaped polyethylene glycol terephthalate is conveyed to the leakage layer channel, the sheet-shaped polyethylene glycol terephthalate can be partially or completely broken due to pressure difference, or the sheet-shaped polyethylene glycol terephthalate is subjected to degradation reaction under the action of high-temperature and strong-alkalinity drilling fluid in the leakage layer channel, and therefore the anchor type material is partially or completely released. And the released anchor-type material is hung on the wall of the channel through an anchor hook in the leakage layer channel, so that the aim of leaking stoppage is fulfilled. The plugging agent can smoothly reach a leakage layer channel, and the anchor type material is released for plugging through physical separation or in-situ degradation.

Description

Technical Field

[0001] The present invention relates to the technical field of chemical materials, and particularly relates to a plugging agent, a preparation method thereof, and an application thereof. Background Art

[0002] During the process of oil drilling operations, due to reasons such as the existence of fractures or pores in the formation and a low formation pressure coefficient, the phenomenon of well leakage often occurs. Well leakage is a worldwide problem, especially the severe leakage in fractured formations, which not only results in the loss of drilling time, consumes a large amount of plugging and drilling fluid materials, damages the oil and gas reservoirs, and affects geological logging, but also causes engineering accidents such as well collapse, stuck pipe, and even leads to the abandonment of the wellbore, and may also cause out-of-control well blowouts, thus triggering safety and environmental protection accidents.

[0003] Currently, the plugging technology mainly focuses on bridging plugging technology. Among them, the bridging plugging materials are mainly prepared by mixing conventional material particles such as walnut shells, fiber materials, and mica in a certain proportion. Due to the insufficient strength of plugging materials such as walnut shells, fiber materials, and mica, it is very difficult for the particle sizes of these materials to match the widths of fractures and holes in the formation. If the particle size of the plugging material is too large, it cannot enter the fracture; if the particle size of the plugging material is too small, it will completely leak with the fluid, and the problem of plugging holes cannot be fundamentally solved. For severe leakage, the width of the fracture is often greater than 3 mm. Due to insufficient strength, the plugging material breaks under the action of the pressure difference between the wellbore fluid column and the formation (usually greater than 1 MPa), which also causes plugging failure.

[0004] How to solve the problem that the plugging material flows out of the hole due to small friction or the plugging material has weak strength and is prone to breakage during severe leakage is an important direction for the research and development of plugging materials.

[0005] CN112940694A discloses an environmentally friendly composite plugging fluid for water-based drilling fluids and a preparation method thereof. By weight, it includes: 20% - 30% of regular tetrahedron rigid materials, 2% - 5% of hydrophobic associating polymers, 10% - 20% of water-absorbing and swelling materials, 10% - 20% of fiber materials, and the balance is water. The regular tetrahedron rigid material is a rigid material with a regular tetrahedron structure formed by pressing limestone powder. The plugging effect of this plugging fluid is good. The regular tetrahedron rigid material can form a plugging layer with very low permeability in the simulated formation fracture under the conditions of short time and less leakage volume, and the formed plugging layer can withstand a pressure of more than 10 MPa. This verifies that the rigid material can achieve plugging and improve the formation pressure-bearing capacity. However, the disadvantage is that the gaps between the regular tetrahedron rigid materials are large, resulting in poor bridging ability.

[0006] "Research Progress of Modified Thermosetting Resin and Its Application Prospect in the Field of Drilling Fluids", "Journal of China University of Petroleum: Edition of Natural Science" published in the second issue of 2022 disclosed a plugging agent composed of unsaturated polyester modified by nitrile rubber and rigid aggregates mixed in a certain proportion. Under the action of formation pressure difference, the UPC of the plugging agent enters the cracks. The cured unsaturated polyester plays a "hanging and blocking" role under the action of formation temperature, making it easier for rigid aggregates to be retained to form a bridge. The nitrile rubber-modified unsaturated polyester is then squeezed into the small pores between the crack space and the rigid aggregate bridge through "heating deformation + extrusion filling". After a period of time, a whole concrete structure is formed to block the leakage channel, improving the pressure-bearing capacity of fractured formations. However, the friction between the rigid aggregate and the crack is small, resulting in easy large-scale loss of the plugging agent.

[0007] Therefore, it is of great significance for oil drilling operations to research and develop a new type of plugging agent with less loss and not easily broken. Summary of the Invention

[0008] In view of this, the technical problem to be solved by the present invention is to provide a plugging agent and its preparation method and application. The plugging agent transports rigid anchor-shaped materials to the leakage layer channel to achieve plugging.

[0009] To achieve the above object, the technical solution adopted by the present invention is as follows:

[0010] The present invention provides a plugging agent, which is composed of sheet-shaped polyethylene terephthalate and at least one anchor-shaped material compounded in the sheet-shaped polyethylene terephthalate.

[0011] The above compounding includes but is not limited to at least one anchor-shaped material being completely embedded in the sheet-shaped polyethylene terephthalate, at least one anchor-shaped material being semi-embedded in the sheet-shaped polyethylene terephthalate, at least one anchor-shaped material being wrapped in the sheet-shaped polyethylene terephthalate, etc.

[0012] The sheet-shaped polyethylene terephthalate is obtained by heating and melting amorphous polyethylene terephthalate and then re-shaping it.

[0013] During the use of the above plugging agent, the anchor-shaped material is released, and its anchor hooks hang on the wall of the leakage layer channel to achieve the plugging effect.

[0014] The sheet-shaped polyethylene terephthalate and the anchor-shaped material can be physically separated by pressure difference, or chemically degraded and separated under high temperature and strong alkali environment in the leakage layer, such as adding strong alkali drilling fluid during drilling.

[0015] Preferably, the anchor-shaped material of the present invention is selected from materials with an anchor hook at one end or anchor hooks at both ends.

[0016] The above anchor-shaped materials can be specifically divided into:

[0017] There are n anchor hooks at only one end;

[0018] Where n≥1 and is an integer;

[0019] There are m anchor hooks at both ends;

[0020] Where m≥1 and is an integer.

[0021] The anchor-shaped material in the plugging agent of the present invention is at least one of the above specific situations.

[0022] The length of the anchor-shaped material in the plugging agent of the present invention is adjusted according to the diameter of the hole channels in different leakage layers.

[0023] Preferably in the present invention, the length of the anchor-shaped material is greater than 3 mm. In some specific embodiments of the present invention, the length is 10 mm.

[0024] Preferably, the thickness of the sheet-shaped polyethylene terephthalate is 0.3 - 10 mm; more preferably 0.5 - 6 mm; further preferably 0.5 - 2 mm. In some specific embodiments of the present invention, the thickness of the sheet-shaped polyethylene terephthalate is 1 mm.

[0025] Preferably in the present invention, the volume ratio of the anchor-shaped material to the sheet-shaped polyethylene terephthalate is 5% - 30%.

[0026] Preferably, the thickness of the above anchor-shaped material is 0.3 - 2 mm.

[0027] The thickness refers to the vertical height when the anchor-shaped material is placed flat. Preferably in the present invention, the anchor-shaped material is selected from one or more of iron wire, carbon steel, and ceramics; more preferably, the anchor-shaped material is selected from iron wire.

[0028] Preferably in the present invention, the sheet-shaped polyethylene terephthalate is selected from one or more of circular polyethylene terephthalate, oval polyethylene terephthalate, polygonal polyethylene terephthalate, and irregular-shaped polyethylene terephthalate; more preferably, the sheet-shaped polyethylene terephthalate is selected from oval polyethylene terephthalate.

[0029] The present invention provides a preparation method of a plugging agent, comprising the following steps:

[0030] Mix the amorphous polyethylene terephthalate chips and the anchor-shaped material, and then heat and press the mixture to shape it, so that the anchor-shaped material is compounded in the sheet-shaped amorphous polyethylene terephthalate to prepare the plugging agent. The mixing is preferably to place the amorphous polyethylene terephthalate chips on the surface of the anchor-shaped material.

[0031] The plugging agent described in the present invention is formed by compounding sheet-shaped polyethylene terephthalate and an anchor-shaped material.

[0032] The anchor-shaped material is bonded and fixed by the sheet-shaped thermoplastic polyethylene terephthalate, so it is not easy to loosen under normal temperature and pressure, which is beneficial to the storage and use of the plugging agent.

[0033] The amorphous polyethylene terephthalate chips in the above preparation method refer to the sheet-shaped particles of processed amorphous polyethylene terephthalate.

[0034] The amorphous polyethylene terephthalate chips in the present invention are ordinary commercially available products. The size of the amorphous polyethylene terephthalate chips is 4mm×4mm×2.5mm, purchased from Sinopec Corporation, fiber-grade polyester, and the model of the bright polyester chips is BRN-204.

[0035] Preferably in the present invention, the heating in the preparation method is to place the mixture between two metal plates, and only one metal plate heats the mixture.

[0036] The above heating is carried out by only one metal plate heating the mixture, aiming to prevent the amorphous polyethylene terephthalate chips from adhering to the metal plate after being heated, resulting in the inability to take out the plugging agent.

[0037] Preferably, the heating temperature is 120°C to 200°C; more preferably 140°C to 180°C.

[0038] The heating and pressure shaping method in the above preparation method is preferably:

[0039] Use the upper and lower metal plates to heat and pressure shape the mixture of the above amorphous polyethylene terephthalate chips and the anchor-shaped material.

[0040] Among them, the temperature of the upper metal plate is preferably 120°C to 200°C; more preferably 140°C to 180°C; further preferably 150°C to 170°C. In some specific embodiments of the present invention, it is preferably 170°C.

[0041] The temperature of the lower metal plate is preferably room temperature.

[0042] The room temperature is preferably 10°C to 30°C.

[0043] The mixture of the amorphous polyethylene terephthalate chips and the anchor-shaped material is placed between the upper and lower metal plates.

[0044] The above heating and pressure shaping method makes the polyethylene terephthalate not adhere to the metal plate, which is convenient for taking out after shaping.

[0045] The metal plate is preferably an iron plate.

[0046] The smooth surface of the iron plate is preferably a polished carbon steel surface.

[0047] Through the above shaping method, a plugging agent sheet with a thickness of 0.3-10 mm is obtained under the condition of being lower than the melting point of polyethylene terephthalate, and it can be smoothly taken out without adhesion.

[0048] The present invention also provides the application of the above plugging agent or the plugging agent prepared by the above preparation method in oil drilling, bridge construction, and reservoir dam construction.

[0049] When the plugging agent of the present invention is used in oil drilling, after the plugging material is sent to the bottom hole leakage layer position, under the pressure difference between the wellbore liquid column and the leakage layer, the plugging agent enters the holes or cracks.

[0050] Adjust the size of the anchor-shaped material according to the size of the above holes or cracks, so that the size of the anchor-shaped material matches the size of the holes or cracks.

[0051] Then, under the pressure difference between the wellbore and the leakage layer, the sheet-shaped polyethylene terephthalate in the plugging agent partially or completely breaks due to low strength, and then the anchor-shaped material is released.

[0052] Next, the released anchor-shaped material moves in the leakage layer channel until the anchor hook of the anchor-shaped material hangs on the wall of the leakage layer channel.

[0053] The above anchor hook is similar to the barbed principle of a fishhook, and can firmly block the leakage layer channel.

[0054] The polyethylene terephthalate is easy to hydrolyze in an alkaline environment above 100°C.

[0055] In oil drilling operations, the downhole temperature above 1000 meters is usually above 100°C, which is beneficial to the in-situ degradation and release of the anchor-shaped material of polyethylene terephthalate.

[0056] Finally, the unrestrained anchor-shaped material can effectively block the downhole leak.

[0057] The present invention also provides a composite plugging agent, including the above plugging agent or the plugging agent prepared by the above preparation method.

[0058] The composite plugging agent also includes, but is not limited to, one or more of walnut shell particles, cottonseed particles, sawdust, calcium carbonate particles, rubber particles, and mica.

[0059] The combination of the above materials and the plugging agent of the present invention can significantly improve the plugging effect.

[0060] Compared with the prior art, the plugging agent provided by the present invention is composed of sheet-shaped polyethylene terephthalate and at least one anchor-shaped material compounded in the sheet-shaped polyethylene terephthalate. The plugging agent is beneficial to transporting the rigid anchor-shaped material to the leakage layer channel without blocking the pipeline. Since the strength of the sheet-shaped polyethylene terephthalate is much smaller than that of the anchor-shaped material, after being transported to the leakage layer channel, the sheet-shaped polyethylene terephthalate will be partially or completely broken due to the pressure difference, or undergo a degradation reaction under the action of high-temperature and strongly alkaline drilling fluid in the leakage layer channel, thereby partially or completely releasing the anchor-shaped material. After being released, the anchor-shaped material hooks on the channel wall through the anchor hook in the leakage layer channel to achieve the purpose of plugging. The present invention realizes the purpose that the plugging agent smoothly reaches the leakage layer channel, and through physical separation or in-situ degradation, further releases the anchor-shaped material for plugging. BRIEF DESCRIPTION OF THE DRAWINGS

[0061] Figure 1 It is a process diagram for preparing the plugging agent in Example 1. Among them, 1 is the upper heating iron plate, 2 is the amorphous polyethylene terephthalate slice, 3 is the anchor-shaped material with one anchor hook, and 4 is the lower normal-temperature iron plate;

[0062] Figure 2 It is a top view of the structure of the plugging agent prepared in Example 1. Among them, 5 is the anchor-shaped material with one anchor hook, and 6 is the oval polyethylene terephthalate;

[0063] Figure 3 It is a diagram of the anchor-shaped material with two anchor hooks in Example 2. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0064] In order to further illustrate the present invention, the plugging agent provided by the present invention, its preparation method and application will be described in detail below in conjunction with the embodiments.

[0065] The production method is as Figure 1 shown. The anchor-shaped material and the amorphous polyethylene terephthalate slices are placed together, and the placed slices and anchor-shaped material are flattened and formed by two metal plates at a certain temperature. The selection of a suitable temperature makes the flat plates not stick to the plugging agent, which is convenient to take out the plugging agent from between the two flat plates.

[0066] Example 1

[0067] The anchor-shaped material uses a wire with a length of 10 mm and a diameter of 1 mm. One end of the wire has a protruding hook with a length of 2 mm, similar to the principle of the barbs of a fishhook. The production process is as Figure 1As shown, the amorphous PET slices of 4 mm×4 mm×2.5 mm and the anchor-shaped material are placed together, and then the upper iron plate heated to 170°C is pressed down. The lower iron plate is at room temperature. Press for 1 second to form a flaky, white and translucent plugging bridging agent. After the PET resin is flattened, a sheet with a thickness of about 1 mm is obtained. The anchor-shaped material and the PET resin sheet are compounded together without loosening, and the plugging agent described in the present invention is prepared. The structure is as Figure 2 shown. The structure of the plugging agent is that the anchor-shaped material containing an anchor hook at one end is compounded in the elliptical polyethylene terephthalate (PET). The volume ratio of the anchor-shaped material to the elliptical polyethylene terephthalate is 20:100.

[0068] Example 2

[0069] The anchor-shaped material uses a wire with a length of 10 mm and a diameter of 1 mm. Each end of the wire has a protruding hook with a length of 2 mm. The structure is as Figure 3 shown. The manufacturing process of the product of the present invention is as Figure 1 shown. The amorphous PET slices of 4 mm×4 mm×2.5 mm and the anchor-shaped material are placed together, and then the upper iron plate heated to 170°C is pressed down. The lower iron plate is at room temperature. Press once, and it can become flaky, white and translucent in 1 second. After the resin is flattened, a sheet with a thickness of about 1 mm is obtained. The composite sheet will not stick to the iron plate and is very easy to remove. The anchor-shaped material and the resin are compounded together without loosening, and the plugging agent described in the present invention is prepared. The structure of the plugging agent is that the anchor-shaped material containing an anchor hook at each end is compounded in the elliptical polyethylene terephthalate. The volume ratio of the anchor-shaped material to the elliptical polyethylene terephthalate is 15:100. The anchor-shaped structure in the plugging agent is as Figure 3 shown.

[0070] Comparative Example 1

[0071] The amorphous polyethylene terephthalate resin slices and an iron wire anchor-shaped material containing an anchor hook are stacked between two iron plates. The lower iron plate is at 170°C and the upper iron plate is at 170°C. Press once, and it can become flaky, white and translucent in 1 second, but it sticks to the iron plate and is very difficult to physically separate.

[0072] The description of the above embodiments is only used to help understand the method and its core idea of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and modifications can be made to the present invention, and these improvements and modifications also fall within the protection scope of the claims of the present invention.

Claims

1. A leak stopper, characterized in that, It is composed of sheet-shaped polyethylene terephthalate and at least one anchor-type material compounded in the sheet-shaped polyethylene terephthalate.

2. The plugging agent according to claim 1, wherein The anchor-type material is selected from materials with an anchor hook at one end or anchor hooks at both ends.

3. The plugging agent according to claim 1, characterized in that, The length of the anchor-type material is greater than 3 mm; The thickness of the sheet-shaped polyethylene terephthalate is 0.3 - 10 mm.

4. The plugging agent according to claim 1, wherein The volume ratio of the anchor-type material to the sheet-shaped polyethylene terephthalate is 5% - 30%.

5. The plugging agent according to claim 1, characterized in that, The anchor-type material is selected from one or more of iron wire, carbon steel, and ceramics.

6. The plugging agent according to claim 1, characterized in that, The sheet-shaped polyethylene terephthalate is selected from one or more of circular polyethylene terephthalate, oval polyethylene terephthalate, polygonal polyethylene terephthalate, and irregular-shaped polyethylene terephthalate.

7. A preparation method of a plugging agent, characterized in that, It includes the following steps: Mix amorphous polyethylene terephthalate slices and the anchor-type material, and then heat and press the mixture to shape it, so that the anchor-type material is compounded in the sheet-shaped amorphous polyethylene terephthalate to prepare a leak stopper.

8. The preparation method according to claim 7, characterized in that, In the heating in the preparation method, the mixture is placed between two metal plates, and only one metal plate heats the mixture; The heating temperature is 120°C - 200°C.

9. The application of the leak stopper according to any one of claims 1 - 6 or the leak stopper prepared by the preparation method according to any one of claims 7 - 8 in oil drilling, bridge construction, and reservoir dam construction.

10. A composite plugging agent, characterized in that, It includes the leak stopper according to any one of claims 1 - 6 or the leak stopper prepared by the preparation method according to any one of claims 7 - 8.

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