Thixotropic agent and strong retention consolidation plugging method suitable for severe leakage

Abstract

The application belongs to the technical field of plugging in oil drilling, and particularly relates to a thixotropic agent and a strong retention and consolidation plugging method suitable for serious leakage. The thixotropic agent comprises 4-5 parts of organic polymer and 4-5 parts of inorganic substance by weight fraction; the organic polymer comprises 2-3 parts of bisphenol A glyceride monomer, 0.5-0.6 parts of acrylamide monomer, 2-3 parts of sulfonic acid monomer and 0.5-1 part of sodium hydroxide. The application realizes the application of the strong retention and consolidation plugging agent to serious leakage of large cracks and large solution cavities by optimizing the formula of the thixotropic agent and designing and optimizing the formula, preparation method and construction method of the plugging slurry prepared by using the thixotropic agent, so that the plugging slurry can be effectively retained in the leakage layer, the plugging effect is achieved, and the success rate of one-time plugging is improved.

Description

Technical Field

[0001] This invention belongs to the field of plugging technology for oil drilling, specifically relating to a thixotropic agent and a strong retention and consolidation plugging method suitable for severe leakage. Background Technology

[0002] Loss due to leakage during drilling accounts for 70-80% of total complex loss time, making it a bottleneck restricting drilling speed and efficiency. Natural fractures in carbonate rocks, karst cavernous leakage, and malignant leakage caused by artificially induced drainage are currently the main challenges in plugging leaks. During drilling, prevention of leakage caused by natural fractures should be a key focus. Statistics show that fracture and karst cavernous leakage account for 78.4% of the total leakage volume and 60.8% of the total leakage time. Leakage velocity is the simplest and most intuitive classification method, and based on the rate of leakage, it can be divided into the following five categories: micro-leakage (≤5m... 3 / h), small leaks (5~15m) 3 / h), medium leakage (15~30m) 3 / h), large leak (30~60m) 3 / h), serious leakage (≥60m) 3 / h).

[0003] Permeable leakage mainly refers to leakage that occurs under pressure differential. The leakage amount is very small and the velocity is slow, with a leakage rate of around 5 m / s. 3 For leak velocities below 5 m / h, plugging while drilling is generally used. When the leakage velocity is between 5 and 30 m / h... 3 Leakage velocities between 30 and 60 m / h are considered small to medium-sized leaks and can be sealed using bridging techniques. 3 For leaks at a rate of / h, cement-based sealing techniques are currently widely used, with a high success rate. However, when the leakage rate is ≥60m / h... 3 Large cracks and severe leakage from karst caves mean that existing consolidation and sealing technologies cannot effectively retain the leakage in large spaces, resulting in a low success rate.

[0004] In view of this, the present invention is hereby proposed. Summary of the Invention

[0005] The purpose of this invention is to provide a thixotropic agent suitable for severe leakage and a strong retention and consolidation sealing method. By designing and optimizing the thixotropic agent and the formulation, preparation method, and construction method of the sealing slurry prepared with it, the strong retention and consolidation sealing agent can be applied to severe leakage in large cracks and large karst caves, ensuring that the sealing slurry is effectively retained in the leaking layer, achieving a sealing effect, and improving the success rate of sealing leakage in one attempt.

[0006] To overcome the shortcomings of the prior art, the present invention provides the following technical solution:

[0007] A thixotropic agent suitable for severe leakage, comprising, by weight, 4-5 parts of an organic polymer and 4-5 parts of an inorganic substance; said organic polymer comprises 2-3 parts of bisphenol A glyceryl ester monomer, 0.5-0.6 parts of acrylamide monomer, 2-3 parts of sulfonic acid monomer, and 0.5-1 part of sodium hydroxide.

[0008] Furthermore, the acrylamide monomer is selected from acrylamide or N,N-dimethylacrylamide;

[0009] And / or, the sulfonic acid monomer is selected from at least one or a combination of 2-acrylamide-2-methylpropanesulfonic acid, sodium styrene sulfonate, or potassium 3-sulfopropyl methacrylate.

[0010] Furthermore, the inorganic material is nano-silica.

[0011] In addition, the present invention also provides a method for preparing the thixotropic agent as described above, comprising the following steps:

[0012] S1. Mix 2-3 parts of bisphenol A glyceride monomer, 0.5-0.6 parts of acrylamide monomer, 2-3 parts of sulfonic acid monomer, 0.5-1 part of sodium hydroxide with 100 parts of water, and stir to dissolve to obtain a monomer mixture.

[0013] S2. Heat the monomer mixture obtained in step S1 to 50°C and add 0.01~0.05 parts of initiator; then continue to heat to 80°C and carry out copolymerization reaction at a constant temperature of 80°C for 5 hours to obtain polymer mixture.

[0014] S3. Disperse 4-5 parts of inorganic matter in 100 parts of water, stir thoroughly for 30 minutes, then add the polymer mixture obtained in step S2 and stir thoroughly for 1 hour to obtain the thixotropic agent.

[0015] Further, in step S2, the initiator is azobisisobutyramidine hydrochloride.

[0016] In addition, the present invention also provides a method for strong retention and consolidation to plug leaks, comprising the following steps:

[0017] (1) Prepare a strong retention and consolidation plugging grout that matches the leakage rate of the formation in the leakage section; the strong retention and consolidation plugging grout includes the thixotropic agent as described in any one of claims 1-3;

[0018] (2) When the drill rod is lowered to a depth of 50-100m above the leaking layer, 10-20m³ of drip support slurry is injected using a drilling fluid pump. The drip support slurry is made by mixing polyacrylamide and xanthan gum in a weight ratio of 1:1 and then adding water and stirring. The amount of water added is 100 times the total weight of polyacrylamide and xanthan gum.

[0019] (3) Stop the drilling fluid pump and inject 2m of pre-fluid using a cement truck. 3 Then inject 20-30 m³ of strong retention and consolidation plugging slurry, and replace it until the plugging slurry is 1-2 m³ in front of the water outlet. Then shut in the well and replace it. After all the cement slurry has come out of the water outlet, perform reverse squeezing. Move the drilling tools before shutting in the well, and after pulling out the drill bit and waiting for it to solidify for 24 hours, test for plugging. After drilling the plug, circulate and test for leaks.

[0020] Furthermore, in step (1), when the leakage velocity is ≥60 m 3 / h and leakage rate ≤100m 3 When the leakage rate is >100 m / h, the formula of the strong retention consolidation plugging slurry includes the following components by weight: 100 parts of G-grade oil well cement, 25-40 parts of weight-reducing material, 1-2 parts of fiber material, 2-4 parts of fluid loss control agent, 0.1-0.5 parts of retarder, 1.4-1.6 parts of thixotropic agent, and 80-100 parts of water; when the leakage rate is >100 m / h. 3 / h until wellhead loss of return, the formula of the strong retention consolidation plugging slurry includes the following components by weight: 100 parts of G-grade oil well cement, 40-50 parts of weight-reducing material, 1-2 parts of fiber material, 2-4 parts of fluid loss reducing agent, 0.1-0.5 parts of retarder, 1.6-2.0 parts of thixotropic agent, and 80-100 parts of water.

[0021] Furthermore, when the leakage velocity is ≥60 m 3 / h and leakage rate ≤100m 3 When the leakage rate is >100 m / h, inject 25 m³ of strong retention consolidation plugging grout; when the leakage rate is >100 m / h 3 / h until wellhead loss of return, inject 30m³ of strong retention consolidation plugging slurry.

[0022] Furthermore, when the leakage velocity is ≥60 m 3 / h and leakage rate ≤100m 3 When the leakage rate is 1 / h, inject 15m³ of drip support grout; when the leakage rate is >100m / h, inject 15m³ of drip support grout. 3 / h until the wellhead loses its return flow, inject 20m³ of drip support grout.

[0023] Furthermore, the light-reducing material is selected from at least one of hollow glass microspheres and fly ash;

[0024] And / or, the fiber material is selected from at least one of polypropylene fiber, polyester fiber, and glass fiber.

[0025] Compared with the prior art, the technical solution of the present invention has at least the following technical effects:

[0026] This invention optimizes the thixotropic agent formulation and designs and optimizes the formulation, preparation method, and construction method of the sealing slurry prepared using it. This enables the application of this strong retention and consolidation sealing agent to prevent severe leakage in large cracks and large karst caves, ensuring that the sealing slurry is effectively retained in the leaking layer, achieving a sealing effect, and improving the success rate of sealing leaks in one attempt. Attached Figure Description

[0027] The accompanying drawings, which form part of this application, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. Wherein:

[0028] Figure 1 Performance curves of the plugging grout prepared for Example 1 and Comparative Example 1;

[0029] Figure 2 Performance curves of the plugging grout prepared for Example 2 and Comparative Example 2;

[0030] Figure 3 Performance curves of the plugging grout prepared for Example 3 and Comparative Example 3;

[0031] Figure 4 The infrared spectrum is a structural characterization of the thixotropic agent of this invention. Detailed Implementation

[0032] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions in the embodiments of this invention will be clearly and completely described below in conjunction with the embodiments of this invention. Those skilled in the art should understand that the embodiments described are merely illustrative of the invention and should not be considered as specific limitations thereof. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention. Process parameters not specifically specified in the following embodiments are generally performed under conventional conditions.

[0033] The endpoints and any values ​​of the ranges disclosed in this invention are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this invention.

[0034] This invention develops a highly retention and consolidation plugging slurry system for severe leakage, which, while possessing consolidation properties, also exhibits high thixotropy and low density. Thixotropy is achieved by adding a thixotropic agent to a common curable material, manifesting as good fluidity during mixing and displacement, followed by rapid thickening after pumping stops, forming a gelled structure with some support, and this process is reversible. The unique properties of thixotropic cement slurry give it excellent retention properties when sealing karst caves and large fractures; however, current thixotropic agents suffer from insufficient temperature resistance and insignificant thixotropic effects, requiring further improvement. Since the thixotropic effect increases only slightly after adding a certain amount of thixotropic agent, and the cement slurry becomes very viscous, affecting its pumpability, this invention will develop a novel thixotropic agent while adding lightweight and fiber materials to the cement slurry system to further enhance the retention effect. The retention effect will be tested using the slurry's starting pressure and pressure loss. Furthermore, this invention also specifies a drilling plugging method for this plugging system.

[0035] According to a first aspect of the invention, a thixotropic agent suitable for severe leakage is provided, comprising, by weight, 4 to 5 parts of an organic polymer and 4 to 5 parts of an inorganic substance; said organic polymer comprises 2 to 3 parts of bisphenol A glyceryl ester monomer, 0.5 to 0.6 parts of acrylamide monomer, 2 to 3 parts of sulfonic acid monomer, and 0.5 to 1 part of sodium hydroxide.

[0036] The mechanism of this novel thixotropic agent is based on the introduction of polar groups such as hydroxyl, amide, and sulfonic acid groups into monomers. After polymerization, these monomers form intramolecular or intermolecular hydrogen bonds, enabling the polymer to form a network structure. (Bisphenol A glycerol ester monomers contain multiple hydroxyl groups, and the amide groups of acrylamide monomers and the sulfonic acid groups of sulfonic acid monomers also possess the ability to form hydrogen bonds. Hydroxyl groups can form multiple hydrogen bonds with these groups (such as the NH bond of the amide group and the OH bond of the sulfonic acid group) and the hydroxyl groups on the surface of inorganic materials (nano-silica), causing the polymer molecules to cross-link and construct a three-dimensional network structure.) The strength of this structural force is determined by the ability of the molecule to form hydrogen bonds. Therefore, this invention introduces bisphenol A glycerol ester and N,N-dimethylacrylamide with multiple hydroxyl and amide groups. The introduction of a high-temperature resistant monomer containing sulfonic acid groups and the rigid benzene ring group of bisphenol A glycerol ester enhances its high-temperature stability, giving the thixotropic agent excellent temperature resistance, exhibiting good thixotropic ability even at 120°C. On the other hand, the polymer backbone and side chains are linked by electrostatic forces, and a network structure can be generated in the slurry through the action of cations. In the initial stage of cement hydration, tricalcium silicate and dicalcium silicate, upon contact with water, will generate CaO in the cement slurry. 2+ Simultaneously, a layer of CSH gel forms on the surface of its particles, and the Ca around its particles... 2+The concentration of Mg2+ shows a radial decreasing trend. Furthermore, during cement hydration, Mg2+ will also be present in the solution. 2+ Al 3+ Cation formation occurs. Divalent and trivalent cations in cement paste can form bonds between polymer molecules. Some of these cations, such as Ca... 2+ Al 3 + The polymer adsorbs onto the surface of cement particles. Therefore, the polymer and cement slurry particles are interconnected through electrostatic interactions, forming a spatial network structure within the cement slurry. The added nano-silica further facilitates hydrogen bonding between organic materials. These hydrogen bonds are disrupted during agitation and re-formed when the mixture is still, as shown in the structural formula below, thus creating a certain degree of thixotropy within the cement slurry.

[0037]

[0038] The structural characterization of the thixotropic agent of the present invention is as follows: Figure 4 As shown in the graph, ~3400-3200 cm -1 This is a characteristic peak resulting from the superposition of NH and OH. ~3188 cm⁻¹ -1 The peak at ~2919 cm⁻¹ is a characteristic peak of the aromatic ring CH in bisphenol A glycerides. -1 and 2964 cm -1 The peak at ~1723 cm⁻¹ is a characteristic peak for aliphatic CH₄. -1 The sharp peak is the characteristic C=O peak of bisphenol A glyceride. ~1650cm -1 1550 cm -1 The sharp peak is a characteristic peak of amide C=O. ~1511cm -1 and ~1601cm -1 There are two moderately intense sharp peaks at this point, which are characteristic peaks of the aromatic ring C=C. ~1289-1110cm -1 The peaks are characteristic of sulfonic acid group S=O, ester group COC, and amide (CN). The medium-intensity peak at ~830 cm⁻¹ is a characteristic peak of the out-of-plane bending vibration of CH in para-disubstituted benzene.

[0039] Based on the above technical solutions, as a preferred embodiment, the acrylamide monomers include, but are not limited to, acrylamide or N,N-dimethylacrylamide; optionally, the sulfonic acid monomers include, but are not limited to, at least one or a combination of 2-acrylamido-2-methylpropanesulfonic acid, sodium styrene sulfonate, or potassium 3-sulfonate propyl methacrylate. Optionally, the inorganic material includes, but is not limited to, nano-silica.

[0040] According to a second aspect of the present invention, a method for preparing the thixotropic agent as described above is provided, comprising the following steps:

[0041] (1) Add 100 parts of distilled water to a container, and add 2-3 parts of bisphenol A glyceride monomer, 0.5-0.6 parts of acrylamide monomer, 2-3 parts of sulfonic acid monomer and 0.5-1 parts of sodium hydroxide to the container by weight, and stir to dissolve to obtain a mixture.

[0042] (2) Heat the container to slowly raise the temperature of the mixture to 50°C, add 0.01-0.05 parts of initiator to the mixture by weight, continue to raise the temperature to 80°C, and keep the mixture reacting at a constant temperature of 80°C for 5 hours to obtain a polymer mixture.

[0043] (3) Disperse 4-5 parts of inorganic matter in 100 parts of distilled water by weight ratio, stir thoroughly for 30 minutes, and then add 4-5 parts of the polymer mixture and stir thoroughly for 1 hour to obtain thixotropic agent.

[0044] The equation logic for the synthesis steps of this invention is as follows:

[0045]

[0046] In the above preparation method, as a preferred embodiment, in step (2), the initiator is azobisisobutyramidine hydrochloride.

[0047] According to a third aspect of the present invention, a method for strong retention consolidation and plugging leaks is provided, comprising the following steps:

[0048] Step 1: Prepare a strong retention and consolidation plugging grout formula that matches the leakage rate of the formation in the leakage section;

[0049] i. When the leakage velocity is ≥60 m 3 / h and leakage rate ≤100m 3 When the flow rate is / h, the formula of the strong retention consolidation plugging grout consists of the following components by weight: 100 parts of G-grade oil well cement, 25-40 parts of weight-reducing material, 1-2 parts of fiber material, 2-4 parts of water loss reducing agent, 0.1-0.5 parts of retarder, 1.4-1.6 parts of thixotropic agent, and 80-100 parts of water.

[0050] ii. When the leakage velocity is >100m 3 The formula for the strong retention and consolidation plugging slurry, which is applied to wellheads and prevents return, consists of the following components by weight: 100 parts of G-grade oil well cement, 40-50 parts of weight-reducing material, 1-2 parts of fiber material, 2-4 parts of fluid loss reducing agent, 0.1-0.5 parts of retarder, 1.6-2.0 parts of thixotropic agent, and 80-100 parts of water.

[0051] The strong-retention consolidation plugging grout is prepared by mixing and stirring G-grade oil well cement, lightweighting materials, fiber materials, fluid loss reducing agent, retarder, thixotropic agent, and water. The thixotropic agent is the thixotropic agent described in the first aspect. The lightweighting materials include, but are not limited to, at least one of hollow glass microspheres, micro / nano silica, and fly ash; optionally, the fiber materials include, but are not limited to, one of polypropylene fiber, polyester fiber, and glass fiber.

[0052] Step 2: Lower the drill pipe to a depth of 50-100m above the leaking layer, and inject 10-20m³ of drip support slurry using a drilling fluid pump. The drip support slurry is prepared by mixing polyacrylamide and xanthan gum in a 1:1 weight ratio, with water added at a ratio of 100 times the total weight of the polyacrylamide and xanthan gum. Optionally, when the leaking velocity is ≥60 m / s... 3 / h and leakage rate ≤100m 3 When the leakage rate is 1 / h, inject 15m³ of drip support grout; when the leakage rate is >100m / h, inject 15m³ of drip support grout. 3 / h until the wellhead loses its return flow, inject 20m³ of drip support grout.

[0053] Step 3: Stop the drilling fluid pump and inject 2m of pre-fluid using a cement truck. 3 (Discharge rate 0.8-1 m³ / min), then inject 20-30 m³ of strong retention and consolidation plugging slurry (discharge rate 0.8-1 m³ / min, average density 1.30-1.50), displacing to 1-2 m³ before the plugging slurry emerges from the water hole. Shut down the well and continue displacing, using the displacement rate determined during the trial squeeze. Observe the standpipe pressure changes throughout the squeezing process. After all the cement slurry has emerged from the water hole, perform a reverse squeezing operation to prevent slurry from entering the annulus above the drill string during the squeezing process. The reverse squeezing volume is 50-100 m³ of annulus volume. If the pressure is too high and squeezing fails, immediately open the well to establish circulation, circulating all remaining cement slurry out of the wellbore. Leave a 50-100 m³ plug in the wellbore. Calculate the cement loss after the water hole emerges and the tripping loss, and reverse-calculate the amount of cement slurry that has leaked into the formation, as well as the height and length of the cement plug. Before shutting in the well and replacing the filler, the drill string needs to be moved up and down and rotated. The drill string should be moved at least once per single section, with the rotation speed controlled at 40-50 rpm. After pulling out the drill string and waiting 24 hours for the filler to solidify, run the drill string plug. After plugging, perform a leak test by circulation. Optionally, when the leakage velocity is ≥60 m / s... 3 / h and leakage rate ≤100m 3 When the leakage rate is >100 m / h, inject 25 m³ of strong retention consolidation plugging grout; when the leakage rate is >100 m / h 3 / h until wellhead loss of return, inject 30m³ of strong retention consolidation plugging slurry. The pre-flush fluid described in this invention is prepared by mixing 2-4 parts of water loss reducing agent, 0.1-0.5 parts of retarder, 1.4-1.6 parts of thixotropic agent and 80-100 parts of water, stirring for 2-4 hours, and then letting it stand for 12 hours. The 12-hour standing time is to allow the thixotropic agent to be well dispersed in the water and enhance its thixotropic ability.

[0054] Based on the above scheme, as a preferred embodiment, the weight-reducing material includes, but is not limited to, at least one of hollow glass microspheres and fly ash; the fiber material includes, but is not limited to, at least one of polypropylene fiber, polyester fiber, and glass fiber.

[0055] The mechanism of strong retention of the plugging slurry in severe leakage of this invention: Whether the consolidated plugging slurry can be retained in the crack depends on whether it can form a continuous phase in the leaking layer. The force of the network structure formed by the newly developed thixotropic agent is the key to the effective retention of the cement slurry in the leaking layer. When facing a leaking layer with severe leakage, reducing the density of the plugging slurry is equally important. Reducing the hydrostatic pressure of the slurry can reduce the pressure difference and thus reduce leakage. Adding fiber materials to the plugging slurry can provide reinforcement and entanglement, further enhancing the retention capacity of the cement slurry. Therefore, this invention, through the combined effect of "developing a new thixotropic agent + lightweighting materials + fibers", enables the plugging slurry to form a continuous phase in the leaking layer. It specifies the injection location of the plugging slurry and the method of horizontally pushing the plugging slurry to close the well after the water outlet, so that the plugging slurry can be smoothly, integrally, and continuously introduced into the leaking layer, improving the retention capacity of the slurry.

[0056] The present invention will now be described in detail with reference to embodiments thereof. These examples are provided by way of explanation and not by way of limitation. In fact, those skilled in the art will recognize that modifications and variations can be made to the present invention without departing from its scope or spirit. For example, a feature shown or described as part of one embodiment may be used in another embodiment to produce yet another embodiment. Therefore, it is desirable that the present invention encompass such modifications and variations that fall within the scope of the appended claims and their equivalents.

[0057] In the embodiments of the present invention, unless otherwise specified, the experimental methods used are conventional methods, and the materials and reagents used are commercially available unless otherwise specified.

[0058] In Examples 1-3 below, the thixotropic agent was prepared using the following method: 100 parts of distilled water were added to a container, along with 2 parts by weight of bisphenol A glyceryl ester monomer, 0.5 parts by weight of N,N-dimethylacrylamide monomer, 3 parts by weight of 2-acrylamide-2-methylpropanesulfonic acid monomer, and 0.5 parts by weight of sodium hydroxide. The mixture was stirred until dissolved to obtain a solution. The container was heated to slowly raise the temperature of the solution to 50°C. 0.02 parts by weight of initiator were added to the solution, and the temperature was further raised to 80°C. The solution was kept at a constant temperature of 80°C for 5 hours to obtain a polymer solution. 5 parts by weight of inorganic matter were dispersed in 100 parts of distilled water and stirred thoroughly for 30 minutes. Then, 5 parts by weight of the polymer solution were added and stirred thoroughly for 1 hour to obtain the thixotropic agent.

[0059] Example 1.1

[0060] Add 100 parts of Grade G oil well cement, 2 parts of water loss reducer, 0.1 parts of retarder, 1.4 parts of the thixotropic agent of this invention, and 46 parts of water to the slurry cup.

[0061] Example 1.2

[0062] Add 100 parts of Grade G oil well cement, 2 parts of water loss reducer, 0.1 parts of retarder, 1.6 parts of the thixotropic agent of this invention, and 46 parts of water to the slurry cup.

[0063] Example 1.3

[0064] Add 100 parts of Grade G oil well cement, 2 parts of water loss reducer, 0.1 parts of retarder, 2.0 parts of the thixotropic agent of this invention, and 46 parts of water to the slurry cup.

[0065] The cement slurries containing the thixotropic agent of the present invention in Examples 1.1-1.3 were cured at 120℃ and then subjected to thixotropic performance tests. The test results are shown in Table 1.

[0066]

[0067] Comparative Example 1.1

[0068] Add 100 parts of G-grade oil well cement, 2 parts of water loss reducer, 0.1 parts of retarder, 1.4 parts of BCJ wet-mixed thixotropic agent (commercially available product), and 46 parts of water to the slurry cup.

[0069] Comparative Example 1.2

[0070] Add 100 parts of G-grade oil well cement, 2 parts of water loss reducer, 0.1 parts of retarder, 1.6 parts of BCJ wet-mixed thixotropic agent (commercially available product), and 46 parts of water to the slurry cup.

[0071] Comparative Example 1.3

[0072] Add 100 parts of Grade G oil well cement, 2 parts of water loss reducer, 0.1 parts of retarder, 2.0 parts of BCJ wet-mixed thixotropic agent (commercially available product), and 46 parts of water to the slurry cup.

[0073] The cement slurries containing commercially available thixotropic agents in Comparative Examples 1.1-1.3 were cured at 120℃ and their thixotropic properties were tested. The test results are shown in Table 2.

[0074]

[0075] As can be seen from Tables 1 and 2, after curing at 120℃, the difference between the initial and final shear values ​​of the high-temperature thixotropic agent of the present invention is above 29.9, while the highest value of the comparative example is only 25.5. This indicates that the thixotropic agent of the present invention still has good thixotropic properties at a high temperature of 120℃.

[0076] Example 1

[0077] Add 100 parts of G-grade oil well cement, 35 parts of light-reducing material (10 parts glass microspheres + 25 parts fly ash), 2 parts of polypropylene fiber material, 2 parts of water loss reducing agent, 0.1-0.5 parts of retarder, 1.4 parts of the thixotropic agent of this invention, and 85 parts of water to the slurry cup.

[0078] The sealing grout prepared in this embodiment was subjected to performance testing: its density was 1.54 g / cm³. 3 The thickening time is 100 min at 50℃, 120 min at 90℃, and 250 min at 120℃; the solidified body strength is 10 MPa.

[0079] The retention effect of the plugging grout was tested indoors. The retention performance was evaluated by measuring the starting pressure and flow pressure loss of the grout as it was brought to a certain flow velocity (0.1 m / s) within a 12 mm diameter straight pipe from a static state. Higher starting pressure and flow pressure loss indicate better grout retention. The test results (e.g., ...) are further analyzed. Figure 1 As shown in the figure, the starting pressure per unit length is 30 kPa and the flow pressure loss per unit length is 20.2 kPa.

[0080] In a certain well, the second drilling section had a borehole diameter of 215.9 mm and a surface casing depth of 801 m. Loss occurred at a depth of 2306 m with a leakage rate of 60 m / s². 3 / h, lithology is basalt, drilling fluid density is 1.54 g / cm³ 3 The initial four attempts at bridging and plugging failed because the leak layer had good connectivity and no obvious pore throats, making it impossible for the bridging material to effectively form a bridge and resulting in poor plugging effect. Therefore, it was decided to use a strong retention and consolidation plugging slurry for plugging.

[0081] (1) Construction plan:

[0082] a) In this construction, first inject 10m³ of supporting grout. The formula is: water + xanthan gum + polyacrylamide. The viscosity is: dripping.

[0083] b) 2m³ pre-filled liquid + 20m³ strong retention consolidation plugging grout + 1m³ post-filled liquid, of which 1.4 parts of thixotropic agent are added.

[0084] c) Performance requirements for sealing grout: density 1.54 g / cm³ 3 Thickening time: 220-250 min.

[0085] d) Well temperature at the location of the leaking layer: 80℃; Data source: Measurements taken together with the directional well.

[0086] (2) Construction process and results:

[0087] Lower the drill pipe to 2250m at the bottom of the well, inject 10m³ of support grout, continue injecting 2m³ of pre-flush fluid, and then inject 15m³ of strong retention consolidation plugging grout. There is still 1m of plugging grout remaining. 3 The pump was stopped at the water outlet, and the well was shut in while injecting 23 m³ of plugging slurry. The pump pressure was at a maximum of 10 MPa, gradually decreasing to a stable 8 MPa. During the slurry replacement, 8.4 m³ of leakage occurred, and approximately 10 m³ of strongly retained and solidified slurry entered the leaking layer. The drill string was pulled out to the casing foot or a safe section and allowed to stand for 24 hours to set. Drilling was then resumed at 2245 m where a cement plug was encountered. The plug was drilled to 2306 m, and circulation was successful with no leakage. Drilling was then resumed.

[0088] Comparative Example 1

[0089] Add 100 parts of Grade G oil well cement, 35 parts of lightening material (10 parts glass microspheres + 25 parts fly ash), 2 parts of polypropylene fiber material, 2 parts of water loss reducing agent, 0.1-0.5 parts of retarder, and 85 parts of water to the slurry cup.

[0090] The performance of the sealing grout prepared in this comparative example was tested: its density was 1.54 g / cm³. 3 The thickening time at 50℃ is 120 min, at 90℃ it is 150 min, and at 120℃ it is 220 min; the solidified body strength is 16 MPa.

[0091] The retention effect of the plugging grout was tested indoors. The retention performance was evaluated by measuring the starting pressure and flow pressure loss of the grout as it was brought to a certain flow velocity (0.1 m / s) within a 12 mm diameter straight pipe from a static state. Higher starting pressure and flow pressure loss indicate better grout retention. The test results (e.g., ...) are further analyzed. Figure 1 As shown in the figure, the starting pressure per unit length is 8.2 kPa and the flow pressure loss per unit length is 5.1 kPa.

[0092] Example 2

[0093] Add 100 parts of G-grade oil well cement, 50 parts of light-reducing material (30 parts glass microspheres + 20 parts fly ash), 2 parts of polypropylene fiber, 3 parts of water loss reducing agent, 0.1-0.5 parts of retarder, 2 parts of the thixotropic agent of this invention, and 100 parts of water to the slurry cup.

[0094] The sealing grout prepared in this embodiment was subjected to performance testing: its density was 1.33 g / cm³. 3 The thickening time at 50℃ is 180 min, at 90℃ it is 360 min, and at 120℃ it is 252 min; the solidified body strength is 6 MPa.

[0095] The retention effect of the plugging grout was tested indoors. The retention performance was evaluated by measuring the starting pressure and flow pressure loss of the grout as it was brought to a certain flow velocity (0.1 m / s) within a 12 mm diameter straight pipe from a static state. Higher starting pressure and flow pressure loss indicate better grout retention. The test results (e.g., ...) are further analyzed. Figure 2 As shown in the figure, the starting pressure per unit length is 43 kPa and the flow pressure loss per unit length is 30.5 kPa.

[0096] In a certain well, the second drilling section had a borehole diameter of 215.9 mm and a surface casing depth of 805 m. Severe leakage occurred at a depth of 2477 m, resulting in loss of return at the wellhead. The lithology was diabase, and the drilling fluid density was 1.28 g / cm³. 3 Initial attempts to plug the leak using bridging and ordinary G-grade cement failed because the leak layer had good connectivity and a high leakage rate, making it difficult for the solidified plugging grout to remain. The bridging material could not effectively form a bridge, resulting in poor plugging performance. Therefore, a strong retention solidified plugging grout was adopted for plugging.

[0097] (1) Construction plan:

[0098] a) In this construction, first inject 20m³ of supporting grout. The formula is: water + xanthan gum + polyacrylamide. The viscosity is: dripping.

[0099] b) 2m³ pre-filled liquid + 30m³ strong retention consolidation plugging grout + 1m³ post-filled liquid, of which 1.8 parts of thixotropic agent are added.

[0100] c) Performance requirements for plugging grout: density 1.33 g / cm3; thickening time: 180-200 min.

[0101] d) Well temperature at the location of the leaking layer: 66℃; Data source: Measurement during directional drilling.

[0102] (2) Construction process and results:

[0103] Lower the drill rod to 2377m, inject 20m³ of support grout, inject 2m³ of pre-filling fluid, and inject 22m³ of strong retention consolidation plugging grout. There is still 1m of plugging grout remaining. 3 The pump at the water outlet was stopped, and the well was shut in while replacement work continued. When the mud pump was displacing nearly 18 m³ at a rate of 10 L / s, the vertical pressure continued to rise. The pump was then stopped and the well was reopened. At this point, approximately 14.84 m³ of strongly retained and consolidated mud had entered the leaking zone. The drill string was pulled out to the casing foot or a safe section, and the drill pipe was circulated at a rate of 30 L / s, resulting in a loss of approximately 9 m³. After 24 hours of static curing, the drill string was run down to 2045 m and encountered a cement plug. The plug was drilled down to 2477 m, and circulation was successful with no loss of mud. Drilling was then resumed.

[0104] Comparative Example 2

[0105] Add 100 parts of Grade G oil well cement, 2 parts of fiber material (polypropylene fiber), 2 parts of the thixotropic agent of this invention, 2 parts of water loss reducing agent, 0.1-0.5 parts of retarder, and 85 parts of water to the slurry cup.

[0106] The performance of the sealing grout prepared in this comparative example was tested: its density was 1.84 g / cm³. 3 The thickening time is 140 min at 50℃, 200 min at 90℃, and 240 min at 120℃; the solidified body strength is 20 MPa.

[0107] The retention effect of the plugging grout was tested indoors. The retention performance was evaluated by measuring the starting pressure and flow pressure loss of the grout as it was brought to a certain flow velocity (0.1 m / s) within a 12 mm diameter straight pipe from a static state. Higher starting pressure and flow pressure loss indicate better grout retention. The test results (e.g., ...) are further analyzed. Figure 2 As shown in the figure, the starting pressure per unit length is 10.2 kPa and the flow pressure loss per unit length is 8.6 kPa.

[0108] Example 3

[0109] Add 100 parts of Grade G oil well cement, 25 parts of light-reducing material (fly ash), 2 parts of fiber, 4 parts of water loss reducer, 0.1-0.5 parts of retarder, 2 parts of the thixotropic agent of this invention, and 80 parts of water to the slurry cup.

[0110] The sealing grout prepared in this embodiment was subjected to performance testing: its density was 1.63 g / cm³. 3 The thickening time at 50℃ is 160 min, at 90℃ it is 220 min, and at 120℃ it is 272 min; the solidified body strength is 10 MPa.

[0111] The retention effect of the plugging grout was tested indoors. The retention performance was evaluated by measuring the starting pressure and flow pressure loss of the grout as it was brought to a certain flow velocity (0.1 m / s) within a 12 mm diameter straight pipe from a static state. Higher starting pressure and flow pressure loss indicate better grout retention. The test results (e.g., ...) are further analyzed. Figure 3 As shown in the figure, the starting pressure per unit length is 26 kPa and the flow pressure loss per unit length is 18.4 kPa.

[0112] In a certain well, the second drilling borehole diameter was 215.9 mm, and the surface casing was run to a depth of 753 m. Loss occurred at a depth of 2415 m, with a leakage rate of 75 m / s². 3 / h, the lithology is gray mudstone and gravelly sandstone with uneven grain size, and the drilling fluid density is 1.46 g / cm³. 3 The two previous attempts at bridging and plugging failed because of the possible presence of a fault, which prevented the bridging material from effectively forming a bridge and resulting in poor plugging performance. Therefore, it was decided to use a strong retention and consolidation plugging slurry for plugging.

[0113] (1) Construction plan:

[0114] a) In this construction, 15m³ of supporting grout will be injected first. The formula is: water + xanthan gum + polyacrylamide. The viscosity is: dripping.

[0115] b) 2m³ pre-filled liquid + 25m³ thixotropic gel plugging grout + 1m³ post-filled liquid, wherein the amount of thixotropic agent is increased by 1.6 parts.

[0116] c) Performance requirements for sealing grout: density 1.63 g / cm³ 3 Thickening time: 220-250 min.

[0117] d) Well temperature at the location of the leaking layer: 80℃; Data source: based on geothermal gradient.

[0118] (2) Construction process and results:

[0119] Lower the drill rod to 2340m, inject 15m³ of support grout, inject 2m³ of pre-filling fluid, inject 25m³ of strong retention consolidation plugging grout, inject 1m³ of post-filling fluid, and wait for 1m of plugging grout to be injected. 3 Stop the pump at the water outlet, shut off the well and continue injecting 20m³ of plugging slurry at a pressure of 5MPa. If the cement slurry height in the wellbore does not drop, pull out the drill string to the casing foot or a safe section and allow it to stand still for 24 hours. Drill down to 2345m and encounter a cement plug. Drill the plug down to 2415m. There is no leakage during circulation, the plugging is successful, and drilling resumes.

[0120] Comparative Example 3

[0121] Add 100 parts of Grade G oil well cement, 25 parts of light-reducing material (fly ash), 1.4 parts of the thixotropic agent of this invention, 2 parts of water loss reducing agent, 0.1-0.5 parts of retarder, and 85 parts of water to the slurry cup.

[0122] The performance of the sealing grout prepared in this comparative example was tested: its density was 1.60 g / cm³. 3 The thickening time is 150 min at 50℃, 225 min at 90℃, and 260 min at 120℃; the solidified body strength is 21 MPa.

[0123] The retention effect of the plugging grout was tested indoors. The retention performance was evaluated by measuring the starting pressure and flow pressure loss of the grout as it was brought to a certain flow velocity (0.1 m / s) within a 12 mm diameter straight pipe from a static state. Higher starting pressure and flow pressure loss indicate better grout retention. The test results (e.g., ...) are further analyzed. Figure 3 As shown in the figure, the starting pressure per unit length is 9.2 kPa and the flow pressure loss per unit length is 6 kPa.

[0124] The foregoing has described and evaluated some embodiments of the present invention. It should be understood that the present invention is not limited to the specific embodiments described above. Any person skilled in the art can make many possible variations and modifications to the technical solutions of the present invention, or modify them into equivalent embodiments, without departing from the scope of the present invention. This does not affect the essential content of the present invention. Therefore, any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention, without departing from the content of the present invention, still fall within the protection scope of the present invention.

Claims

1. A method for strong retention and consolidation to stop leaks, characterized in that, Includes the following steps: (1) Prepare a strong retention and consolidation plugging grout that matches the leakage rate of the formation in the leakage section; the strong retention and consolidation plugging grout includes a thixotropic agent suitable for severe leakage; (2) When the drill rod is lowered to a depth of 50-100m above the leaking layer, 10-20m³ of drip support slurry is injected using a drilling fluid pump. The drip support slurry is made by mixing polyacrylamide and xanthan gum in a weight ratio of 1:1 and then adding water and stirring. The amount of water added is 100 times the total weight of polyacrylamide and xanthan gum. (3) Stop the drilling fluid pump and inject 2m of pre-fluid using a cement truck. 3 Then inject 20-30 m³ of strong retention and consolidation plugging slurry, and replace it until the plugging slurry is 1-2 m³ in front of the water outlet. Then shut in the well and replace it. After all the cement slurry has come out of the water outlet, perform reverse squeezing. Move the drill string before shutting in the well, and after pulling out the drill string and waiting for it to solidify for 24 hours, test for plugging. After drilling the plug, circulate and test for leaks. The method for preparing the thixotropic agent includes the following steps: S1. Mix 2-3 parts of bisphenol A glyceride monomer, 0.5-0.6 parts of acrylamide monomer, 2-3 parts of sulfonic acid monomer, 0.5-1 part of sodium hydroxide with 100 parts of water, and stir to dissolve to obtain a monomer mixture. S2. Heat the monomer mixture obtained in step S1 to 50°C and add 0.01~0.05 parts of initiator; then continue to heat to 80°C and carry out copolymerization reaction at a constant temperature of 80°C for 5 hours to obtain polymer mixture. S3. Disperse 4-5 parts of inorganic matter in 100 parts of water, stir thoroughly for 30 minutes, then add the polymer mixture obtained in step S2 and stir thoroughly for 1 hour to obtain the thixotropic agent.

2. The strong retention consolidation and plugging method according to claim 1, characterized in that, The acrylamide monomer is selected from acrylamide or N,N-dimethylacrylamide; And / or, the sulfonic acid monomer is selected from at least one or a combination of 2-acrylamido-2-methylpropanesulfonic acid, sodium styrene sulfonate, or potassium 3-sulfopropyl methacrylate.

3. The strong retention consolidation and plugging method according to claim 1, characterized in that, The inorganic material is nano-silica.

4. The strong retention consolidation and leak-sealing method according to claim 1, characterized in that, In step S2, the initiator is azobisisobutyramidine hydrochloride.

5. The strong retention consolidation and plugging method according to claim 1, characterized in that, In step (1), when the leakage velocity is ≥60m 3 / h and leakage rate ≤100m 3 When the leakage rate is >100 m / h, the formula of the strong retention consolidation plugging slurry includes the following components by weight: 100 parts of G-grade oil well cement, 25-40 parts of weight-reducing material, 1-2 parts of fiber material, 2-4 parts of fluid loss control agent, 0.1-0.5 parts of retarder, 1.4-1.6 parts of thixotropic agent, and 80-100 parts of water; when the leakage rate is >100 m / h. 3 / h until wellhead loss of return, the formula of the strong retention consolidation plugging slurry includes the following components by weight: 100 parts of G-grade oil well cement, 40-50 parts of weight-reducing material, 1-2 parts of fiber material, 2-4 parts of fluid loss reducing agent, 0.1-0.5 parts of retarder, 1.6-2.0 parts of thixotropic agent, and 80-100 parts of water.

6. The strong retention consolidation and plugging method according to claim 5, characterized in that, When the leakage velocity is ≥60m 3 / h and leakage rate ≤100m 3 When the leakage rate is >100 m / h, inject 25 m³ of strong retention consolidation plugging grout; when the leakage rate is >100 m / h 3 / h until wellhead loss of return, inject 30m³ of strong retention consolidation plugging slurry.

7. The strong retention consolidation and plugging method according to claim 5, characterized in that, When the leakage velocity is ≥60m 3 / h and leakage rate ≤100m 3 When the leakage rate is 1 / h, inject 15m³ of drip support grout; when the leakage rate is >100m / h, inject 15m³ of drip support grout. 3 / h until the wellhead loses its return flow, inject 20m³ of drip support grout.

8. The strong retention consolidation and plugging method according to claim 5, characterized in that, The light-reducing material is selected from at least one of hollow glass microspheres and fly ash; And / or, the fiber material is selected from at least one of polypropylene fiber, polyester fiber, and glass fiber.

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