Plugging wall-fixing well cementation weighted spacer fluid and preparation method thereof

Abstract

The invention provides a plugging wall-fixing type well cementation weighted spacer fluid and a preparation method thereof. The spacer fluid comprises the following raw materials: an active curing reinforcing material, an active filling plugging material, an expansion plugging material and water. The spacer fluid has good compatibility with well cementation cement slurry and common water-based drilling fluid, has good construction performance, carries an expansion plugging material and can effectively plug micro-crack and high-permeability leakage, so that the risk of well cementation leakage is greatly reduced; the high-activity curing reinforcing material contained in the high-activity curing reinforcing material has a curing and healing function in a crack, and the retained high-activity curing reinforcing material can participate in interface curing and cementation at a first interface and a second interface of well cementation, so that the interface cementation strength is improved, the wall cementation effect is achieved, and the long-term sealing integrity of the well cementation interface is favorably improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of oil and gas well drilling and completion engineering, and relates to a spacer fluid and a preparation method thereof, in particular to a plugging and wall-strengthening type cementing weighted spacer fluid and a preparation method thereof. Background Art

[0002] In the cementing operation of oil and gas wells, the compatibility between drilling fluid and cement slurry is generally poor. If the drilling fluid comes into direct contact with the cement slurry, flocculation and thickening will occur, which will cause the following serious consequences: ① The flow resistance of the contaminated slurry is greatly increased, and the construction pressure is additionally increased; ② The viscous slurry has a large viscous force in the well, especially at the cementing interface, and it is very difficult to be flushed clean, affecting the cement slurry interface bonding; ③ The performance of the cement slurry will get out of control after being contaminated. If the thickening time is shortened or even "flash setting" occurs, it will lead to the occurrence of "sausage filling" accidents. In summary, by injecting a section of spacer fluid before injecting the cement slurry, it can effectively isolate and prevent the drilling fluid from contacting and contaminating the cement slurry.

[0003] With the gradual exploration and development of oil and gas resources towards deep and ultra-deep layers and unconventional reservoirs, the geological conditions faced are more complex, and the difficulty of drilling and completion is gradually increasing. The complex geological conditions have put forward higher requirements for drilling and completion technologies and engineering fluids. During the drilling process of some unconventional oil and gas reservoirs, well leakage complex situations caused by drilling through fault fracture zones and formations with developed natural microfractures often occur. Well leakage refers to a downhole complex situation in which drilling fluid leaks into the formation under the action of pressure difference during the drilling operation of oil and gas wells. Well leakage will not only cause a large loss of drilling fluid and lost circulation materials, but also may cause other downhole complex situations and major accidents such as well collapse, pipe sticking, and blowout, seriously affecting drilling safety and cost. Well leakage is a technical problem that has long existed in the drilling and completion operations of oil and gas wells, and lost circulation control technology is also an important content that drilling and completion researchers have long been working on. In recent years, researchers have developed a variety of lost circulation control materials and conducted tests and applications in the field, and the success rate of the first lost circulation control has been significantly improved, and the lost circulation control technology has developed by leaps and bounds. Nevertheless, in some formations with developed microfractures and high-permeability formations, the well leakage problem during the process from running the casing to injecting and displacing the cement slurry is still difficult to handle well, because different from the lost circulation control string, due to the special structure of the casing string itself, it is more difficult to implement conventional lost circulation control measures at this time.

[0004] The quality of cementing directly affects whether a well can be successfully completed and handed over, and has a long-term impact on the subsequent safe production, oil and gas production, and service life of oil and gas wells. Poor bonding quality at the second cementing interface is one of the main reasons for interlayer channeling and annulus pressure buildup. Affected by wellbore quality, formation conditions, drilling fluid performance, especially mud cake performance, improving the bonding quality at the second cementing interface is a complex system engineering. Traditional weighted spacer fluids generally consist of components such as thickeners, suspension stabilizers, flushing agents, and weighting materials, and generally do not have the functions of shielding and plugging and improving the bonding quality at the cementing interface.

[0005] In recent years, for different geological conditions, well depths, and well types, researchers have developed some new types of spacer fluid systems with multiple functions. CN116285917A discloses a high-temperature-resistant plugging spacer fluid and its preparation method. The spacer fluid includes the following components in parts by mass: 500 parts of clear water, 200 - 500 parts of weighting agent, 5 - 30 parts of suspension stabilizer, 21 - 49 parts of plugging agent, 1 - 15 parts of flushing agent, and 1 - 10 parts of defoaming agent. Although this spacer fluid can resist high temperature up to 160°C, its density can be adjusted within the range of 1.30 g / cm 3 - 1.60 g / cm 3 , and its plugging pressure-bearing capacity is not less than 3 MPa, but it belongs to a non-curable type of spacer fluid and does not have an obvious wall stabilizing effect.

[0006] CN112625663A discloses a cementing composite plugging spacer fluid system and its application. This spacer fluid system provides a cementing composite plugging spacer fluid system based on thermosensitive swelling polymers. On the premise of ensuring the pumpability of the fluid, it improves the bridging and deformation filling ability of the spacer fluid, enhances the plugging effect, and provides technical support for cementing in severely lost circulation formations. Although the thermosensitive points of the deformed fine particles and the deformed fibers can be adjusted according to the on-site use conditions, it has limitations in use for wells with long open-hole sections, many easily lost layers with large spacing and large temperature differences.

[0007] CN113583640A discloses a curable multi-functional cementing spacer fluid and its preparation method and device. This spacer fluid system is composed of 10 - 15% of basic material, 15 - 20% of curing fluid material, 50 - 55% of reinforcing material, and 15 - 20% of lightening material; the density adjustment range and applicable temperature range of this spacer fluid system are not clearly defined.

[0008] At present, although a batch of spacer fluid systems with a wide range of applicable temperature ranges and density ranges have been developed and applied in large-scale on-site cementing, most of them only have basic isolation functions. In view of the problems of leakage in micro-fractured formations and highly permeable formations before cementing, there is an urgent need to develop a cementing weighted spacer fluid system with a certain plugging ability and a wall stabilizing effect to reduce the leakage risk during cementing construction, improve the one-time cementing success rate, improve the cementing interface bonding quality, and meet the requirements of wellbore sealing integrity throughout the life cycle. Summary of the Invention

[0009] To solve the above technical problems, the present application provides a plugging and wall-strengthening type cementing weighted spacer fluid and a preparation method thereof. The spacer fluid has good compatibility with cement slurry and common water-based drilling fluids, has good construction performance, and carries its own expansion plugging material, which can effectively plug micro-fracture and high-permeability losses, greatly reducing the risk of cementing losses. The highly active curing and strengthening material it contains, in addition to having its own curing and healing function in cracks, at the first and second cementing interfaces, the retained highly active curing and strengthening material can participate in interface curing and cementing, thereby improving the interface cementing strength, achieving the wall-strengthening effect, and being beneficial to improving the long-term sealing integrity of the cementing interface.

[0010] To achieve the above technical effects, the present invention adopts the following technical solutions:

[0011] One of the objectives of the present invention is to provide a plugging and wall-strengthening type cementing weighted spacer fluid, and the raw materials of the spacer fluid include a reactive curing and strengthening material, a reactive filling and plugging material, an expansion plugging material, and water.

[0012] In the present invention, a compound expansion plugging material is adopted, taking into account the bridging and expansion effects, and the plugging effect is better (the plugging pressure resistance > 3.2 MPa); a reactive curable material and a reactive filling material are adopted, which have the ability to cure and heal micro-cracks to a certain extent; a reactive curing and strengthening material is contained, which can participate in interface curing and cementing at the cementing interface, improving the interface cementing strength.

[0013] As a preferred technical solution of the present invention, the raw materials of the spacer fluid further include an activating material, a suspension stabilizing material, a dispersing and diluting material, a fluid loss reducer, an antifoaming agent, and a foam inhibitor.

[0014] As a preferred technical solution of the present invention, the raw materials are as follows by weight:

[0015]

[0016] Among them, the weight parts of the active filling and plugging material can be 10 parts, 11 parts, 12 parts, 13 parts, 14 parts, 15 parts, 16 parts, 17 parts, 18 parts, 19 parts or 20 parts, etc.; the weight parts of the expansion plugging material can be 10 parts, 12 parts, 15 parts, 18 parts, 20 parts, 22 parts, 25 parts, 28 parts or 30 parts, etc.; the weight parts of the activation material can be 6 parts, 6.5 parts, 7 parts, 7.5 parts, 8 parts, 8.5 parts, 9 parts, 9.5 parts or 10 parts, etc.; the weight parts of the suspension stabilizing material can be 0.25 parts, 0.5 parts, 0.75 parts or 1 part, etc.; the weight parts of the dispersion and dilution material can be 2 parts, 3 parts, 4 parts, 5 parts, 6 parts, 7 parts or 8 parts, etc.; the weight parts of the fluid loss reducer can be 1 part, 1.5 parts, 2 parts, 2.5 parts, 3 parts, 3.5 parts or 4 parts, etc.; the weight parts of the defoamer can be 1 part, 1.1 parts, 1.2 parts, 1.3 parts, 1.4 parts, 1.5 parts, 1.6 parts, 1.7 parts, 1.8 parts, 1.9 parts or 2 parts, etc.; the weight parts of the foam inhibitor can be 1 part, 1.2 parts, 1.5 parts, 1.8 parts, 2 parts, 2.2 parts, 2.5 parts, 2.8 parts or 3 parts, etc.; the weight parts of water can be 100 parts, 150 parts, 200 parts, 250 parts, 300 parts, 350 parts, 400 parts or 450 parts, etc. However, it is not limited to the listed values, and other unlisted values within the above numerical ranges are equally applicable.

[0017] As a preferred technical solution of the present invention, the active curing and strengthening material is blast furnace slag powder.

[0018] In the present invention, the blast furnace slag powder is a commercially available blast furnace slag powder produced in accordance with GB / T 18046-2017 "Ground Granulated Blast Furnace Slag for Cement, Mortar and Concrete".

[0019] As a preferred technical solution of the present invention, the active filling and plugging material is fly ash.

[0020] Preferably, the particle size of the fly ash is 0.5 - 400 μm.

[0021] As a preferred technical solution of the present invention, the expansion plugging material includes any one or a combination of at least two of basalt hard fibers, expanded graphite or vermiculite.

[0022] Preferably, the length of the basalt hard fibers is 5 - 15 mm, such as 5 mm, 6 mm, 7 mm, 8 mm, 9 mm, 10 mm, 11 mm, 12 mm, 13 mm, 14 mm or 15 mm, etc. However, it is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0023] As a preferred technical solution of the present invention, the activation material includes any one or a combination of at least two of sodium metasilicate pentahydrate, sodium hydroxide, sodium carbonate or water glass. Typical but non-limiting examples of the combination include: the combination of sodium metasilicate pentahydrate and sodium hydroxide, the combination of sodium hydroxide and sodium carbonate, the combination of sodium carbonate and water glass, the combination of water glass and sodium metasilicate pentahydrate, or the combination of sodium metasilicate pentahydrate, sodium hydroxide and sodium carbonate, etc.

[0024] Preferably, the suspension stabilizing material includes xanthan gum.

[0025] Preferably, the dispersion and dilution material is sodium tripolyphosphate and / or disodium ethylenediaminetetraacetate.

[0026] Preferably, the fluid loss control agent includes an AMPS copolymer fluid loss control agent.

[0027] Preferably, the defoaming agent includes glycerol polyether or tributyl phosphate.

[0028] Preferably, the foam suppressant includes silicone and / or silicone ether oil.

[0029] The second object of the present invention is to provide a preparation method of the plugging and wall stabilizing type cementing weighted spacer provided by the first object. The preparation method includes:

[0030] Mix the active curing and strengthening material, the active filling and plugging material and the swelling plugging material to obtain a solid mixture;

[0031] Add the solid mixture to water and stir to obtain the plugging and wall stabilizing type cementing weighted spacer.

[0032] As a preferred technical solution of the present invention, the activation material, the suspension stabilizing material, the dispersion and dilution material and the fluid loss control agent are mixed with the active curing and strengthening material, the active filling and plugging material and the swelling plugging material together to obtain a solid mixture.

[0033] As a preferred technical solution of the present invention, before adding the solid mixture to water, first mix water with the defoaming agent and the foam suppressant.

[0034] In the present invention, the way of dry mixing the solid raw materials can be: using a dry mixing device, according to the volume of the mixing tank, batch by batch, put the dry mixing raw materials used in each batch into the mixing tank in sequence for pneumatic mixing to obtain a uniform solid mixture, and transport the solid mixture to the well site by a powder and granular material transport vehicle before on-site construction.

[0035] In the present invention, an antifoaming agent and an anti-foaming agent are added to water at a rotation speed of 1000 - 1500 rpm. Among them, the rotation speed can be 1000 rpm, 1100 rpm, 1200 rpm, 1300 rpm, 1400 rpm, 1500 rpm, etc., but is not limited to the listed values, and other unlisted values within this value range are equally applicable.

[0036] In the present invention, the solid mixture is added to water within 30 - 60 s, and then stirred at a rotation speed of 2000 ± 100 rpm for 2 - 5 min. Among them, the time for adding the solid mixture to water can be 30 s, 35 s, 40 s, 45 s, 50 s, 55 s, 60 s, etc.; the stirring rotation speed can be 1900 rpm, 1950 rpm, 2000 rpm, 2050 rpm, 2100 rpm, etc.; the stirring time can be 2 min, 2.5 min, 3 min, 3.5 min, 4 min, 4.5 min, 5 min, etc., but is not limited to the listed values, and other unlisted values within the above value ranges are equally applicable.

[0037] Compared with the prior art, the present invention has at least the following beneficial effects:

[0038] (1) The present invention discloses a plugging and wall-strengthening type cementing weighted spacer fluid, and the spacer fluid has excellent plugging effect, ability to cure and heal microcracks, and high interfacial bonding strength;

[0039] (2) The present invention discloses a plugging and wall-strengthening type cementing weighted spacer fluid, and the density of the spacer fluid can be controlled at 1.20 g / cm 3 ~1.60 g / cm 3 by adjusting the liquid-solid ratio, without the need to add additional weighting materials, and it is applicable to the bottom-hole circulating temperature of 40 - 120 °C;

[0040] (3) The present invention discloses a preparation method of a plugging and wall-strengthening type cementing weighted spacer fluid. The preparation method adopts a fully dry mixing method, can be packaged in 25 kg / bags, or can be packaged in ton bags, which is convenient for long-distance transportation; on-site construction can adopt the method of mixing and injecting while using a cementing truck, or can use a batch mixing truck for secondary stirring to ensure more uniform density, and the preparation is convenient. Specific Embodiments

[0041] To facilitate the understanding of the present invention, the following examples are listed for the present invention. Those skilled in the art should understand that the examples are only for helping to understand the present invention and should not be regarded as specific limitations on the present invention.

[0042] Example 1

[0043] This example provides a preparation method of a plugging and wall-strengthening type cementing weighted spacer fluid, and the preparation method includes:

[0044] S1: Weigh the following materials in parts by weight as required: 100 parts of slag powder, 20 parts of fly ash, 8 parts of sodium metasilicate pentahydrate, 30 parts of basalt hard fiber (length 5 mm - 15 mm), 1 part of xanthan gum, 2 parts of disodium ethylenediaminetetraacetate (EDTA), 4 parts of AMPS copolymer fluid loss reducer. Dry-mix the above materials evenly to form a solid mixture;

[0045] S2: Add 0.5 part of tributyl phosphate and 0.5 part of silicone to 450 parts by weight of clear water, and stir at a speed of 1500 ± 50 rpm for 30 s to form a mixed liquid.

[0046] S3: At a speed of 1500 ± 50 rpm, uniformly add the solid mixture to the mixed liquid within 15 s, adjust the speed to 2000 ± 50 rpm, and continue to stir for 2 min to obtain the plugging and wall-building type cementing weighting spacer A with a density of 1.20 g / cm 3 as described above.

[0047] The plugging and wall-building type cementing weighting spacer A has a density of 1.20 g / cm 3 , a liquid-solid ratio of 2.73. After pressure-boosted thickening and curing (72 °C × 47 MPa × 40 min), it is placed in a 250 mL measuring cylinder and placed in a 90 °C water bath for 2 h to measure the stability: the density difference is 0.01 g / cm 3 , the pressure-bearing capacity for plugging a 1 mm crack > 3.2 MPa, and the strength of the cured body at 70 °C × 2 d is 0.6 MPa.

[0048] Example 2

[0049] This example provides a preparation method for a plugging and wall-building type cementing weighting spacer. The preparation method includes:

[0050] S1: Weigh the following materials in parts by weight as required: 100 parts of slag powder, 18 parts of fly ash, 7 parts of sodium metasilicate pentahydrate, 27 parts of basalt hard fiber (length 5 mm - 15 mm), 1 part of xanthan gum, 2 parts of disodium ethylenediaminetetraacetate (EDTA), 4 parts of AMPS copolymer fluid loss reducer. Dry-mix the above materials evenly to form a solid mixture;

[0051] S2: Add 0.5 part of tributyl phosphate and 0.5 part of silicone to 270 parts by weight of clear water, and stir at a speed of 1500 ± 50 rpm for 50 s to form a mixed liquid;

[0052] S3: At a speed of 1500 ± 50 rpm, uniformly add the solid mixture to the mixed liquid within 15 s, adjust the speed to 2000 ± 50 rpm, and continue to stir for 2 min to obtain the plugging and wall-building type cementing weighting spacer B with a density of 1.30 g / cm 3 as described above;

[0053] The plugging and wall - fixing type cementing weighted spacer fluid B has a density of 1.30 g / cm 3 , a liquid - solid ratio of 1.70. After pressurized thickening and curing (72℃×47MPa×40min), it is placed in a 250 mL graduated cylinder and left standing in a 90℃ water bath for 2 h to measure its stability: the density difference is 0.01 g / cm 3 , the pressure - bearing capacity for plugging a 1 - mm crack is > 3.2 MPa, and the strength of the cured body at 70℃×2d is 1.0 MPa.

[0054] Example 3

[0055] This example provides a preparation method of a plugging and wall - fixing type cementing weighted spacer fluid. The preparation method includes:

[0056] S1: Weigh the following materials by weight as required: 100 parts of slag powder, 16 parts of fly ash, 7 parts of sodium metasilicate pentahydrate, 25 parts of basalt hard fiber (length 5 mm - 15 mm), 1 part of xanthan gum, 3 parts of disodium ethylenediaminetetraacetate (EDTA), 4 parts of AMPS copolymer fluid loss reducer. Dry - mix the above materials evenly to form a solid mixture;

[0057] S2: Add 0.5 part of tributyl phosphate and 0.5 part of silicone to 186 parts by weight of clear water, and stir at a speed of 1500 ± 50 rpm for 50 s to form a mixed liquid;

[0058] S3: At a speed of 1500 ± 50 rpm, uniformly add the solid mixture to the mixed liquid within 15 s, adjust the speed to 2000 ± 50 rpm, and continue stirring for 2 min to obtain the plugging and wall - fixing type cementing weighted spacer fluid C with a density of 1.40 g / cm 3 .

[0059] The plugging and wall - fixing type cementing weighted spacer fluid C has a density of 1.40 g / cm 3 , a liquid - solid ratio of 1.20. After pressurized thickening and curing (72℃×47MPa×40min), it is placed in a 250 mL graduated cylinder and left standing in a 90℃ water bath for 2 h to measure its stability: the density difference is 0.01 g / cm 3 , the pressure - bearing capacity for plugging a 1 - mm crack is > 3.2 MPa, and the strength of the cured body at 70℃×2d is 2.1 MPa.

[0060] Example 4

[0061] This example provides a preparation method of a plugging and wall - fixing type cementing weighted spacer fluid. The preparation method includes:

[0062] S1: Weigh the following materials in parts by weight as required: 100 parts of slag powder, 14 parts of fly ash, 7 parts of sodium metasilicate pentahydrate, 22 parts of basalt hard fiber (length 5 mm - 15 mm), 1 part of xanthan gum, 4 parts of disodium ethylenediaminetetraacetate (EDTA), and 3 parts of AMPS copolymer fluid loss reducer. Dry-mix the above materials evenly to form a solid mixture;

[0063] S2: Add 0.5 part of tributyl phosphate and 0.5 part of silicone to 132 parts by weight of clear water, and stir at a speed of 1500 ± 50 rpm for 50 s to form a mixed liquid;

[0064] S3: At a speed of 1500 ± 50 rpm, uniformly add the solid mixture to the mixed liquid within 15 s, adjust the speed to 2000 ± 50 rpm, and continue stirring for 2 min to obtain the plugging and wall-building type cementing weighting spacer fluid D with a density of 1.50 g / cm 3 of the above.

[0065] This plugging and wall-building type cementing weighting spacer fluid D has a density of 1.50 g / cm 3 , a liquid-solid ratio of 0.88. After pressure-boosted thickening and curing (72 °C × 47 MPa × 40 min), place it in a 250 mL graduated cylinder and put it in a 90 °C water bath to stand for 2 h to measure the stability: the density difference is 0.02 g / cm 3 , the pressure-bearing capacity for plugging a 1 mm crack > 3.2 MPa, and the strength of the cured body at 70 °C × 2 d is 2.9 MPa.

[0066] Example 5

[0067] This example provides a preparation method for a plugging and wall-building type cementing weighting spacer fluid. The preparation method includes:

[0068] S1: Weigh the following materials in parts by weight as required: 100 parts of slag powder, 12 parts of fly ash, 7 parts of sodium metasilicate pentahydrate, 20 parts of basalt hard fiber (length 5 mm - 15 mm), 0.8 part of xanthan gum, 7 parts of disodium ethylenediaminetetraacetate (EDTA), and 2 parts of AMPS copolymer fluid loss reducer. Dry-mix the above materials evenly to form a solid mixture.

[0069] S2: Add 0.5 part of tributyl phosphate and 0.5 part of silicone to 100 parts by weight of clear water, and stir at a speed of 1500 ± 50 rpm for 50 s to form a mixed liquid.

[0070] S3: At a speed of 1500 ± 50 rpm, uniformly add the solid mixture to the mixed liquid within 15 s, adjust the speed to 2000 ± 50 rpm, and continue stirring for 2 min to obtain the plugging and wall-building type cementing weighting spacer fluid E with a density of 1.60 g / cm 3 of the above.

[0071] The plugging and wall - fixing type cementing weighted spacer fluid E has a density of 1.60 g / cm 3 , a liquid - solid ratio of 0.68. After pressurized thickening and curing (72℃×47MPa×40min), it is placed in a 250 mL graduated cylinder and left to stand in a 90℃ water bath for 2 h to measure its stability: the density difference is 0.02 g / cm 3 , the pressure - bearing capacity for plugging a 1 - mm crack is > 3.2 MPa, and the strength of the cured body at 70℃×2d is 4.2 MPa.

[0072] Comparative Example 1

[0073] In this comparative example, except that fly ash is replaced with an equal mass of slag powder, the other conditions are the same as those in Example 1.

[0074] Comparative Example 2

[0075] In this comparative example, except that basalt hard fibers are replaced with an equal mass of slag powder, the other conditions are the same as those in Example 1.

[0076] According to the indoor test method for bridging plugging materials for drilling SY / T5840 - 93 of the petroleum and natural gas industry standard of the People's Republic of China, using a self - developed plugging instrument and placing a 1 - mm stainless - steel slotted plate, the plugging performance of the spacer fluid systems provided in Examples 1 - 5 and Comparative Examples 1 and 2 is tested. The experimental results are shown in Table 1:

[0077] Table 1

[0078]

[0079] As can be seen from Table 1, the density differences of the above - mentioned examples are all ≤ 0.02 g / cm 3 , indicating that the stability of the spacer fluid is good; the pressure - bearing capacity of the 1 - mm slotted plate is all greater than 3.2 MPa, having the ability to stably plug micro - cracks; a cured body can be formed after curing at 70℃ for 2 d, and the strength of the cured body with a density of 1.60 g / cm 3 reaches 4.2 MPa, indicating that it has the ability to heal micro - cracks itself.

[0080] Use a self - developed interfacial strength test mold to conduct a comparative experiment on the interfacial bonding strength of the spacer fluid E and the water - based drilling fluid attached to the second interface of cementing. The test data are shown in Table 2:

[0081] Table 2

[0082] Two-interface adhesion medium <![CDATA[Density (g / cm 3 )]]> Two-interface cementation strength (70°C × atmospheric pressure × 2d), MPa Water-based drilling fluid 1.50 0.2 Isolation fluid E 1.60 1.8

[0083] Note: The drilling fluid used is a potassium - calcium - based organic salt drilling fluid system taken from a drilling site in Xinjiang Oilfield, with a density of 1.50 g / cm 3 , a viscosity of 60 s, a dynamic shear force of 8 Pa, a mud cake of 0.3 mm, and a pH value of 9.5.

[0084] As can be seen from Table 2, when drilling fluid adheres to the second cementing interface, the bond strength of the 2d interface is 0.2 MPa. Under the same conditions, the bond strength value of the interface with spacer fluid E adhering is 1.8 MPa, and the interface strengthening effect is significant, indicating that this spacer fluid system participates in the solidification and cementation of the cementing interface and has excellent wall-building function.

[0085] The compressive strength of the mixed slurry with cement slurry (1.90 g / cm 3 ), water-based drilling fluid (1.50 g / cm 3 ), and spacer fluid (1.60 g / cm 3 ) blended evenly in a ratio of 1:1:1 was evaluated, and the experimental data are shown in Table 3:

[0086] Table 3

[0087] Curing age Compressive strength (70°C × atmospheric pressure), MPa 2d 7.2 7d 10.6

[0088] As can be seen from Table 3, the compressive strength of the mixed slurry with cement slurry, water-based drilling fluid, and spacer fluid blended in a ratio of 1:1:1 is 7.2 MPa after curing for 2 days under the condition of a 70°C water bath, and the compressive strength reaches 10.6 MPa after curing for 7 days. With the extension of time, the interface strength is further developed.

[0089] In summary, a plugging and wall-building type cementing weighted spacer fluid of the present invention does not require additional weighting materials, and the density can be controlled between 1.20 g / cm 3 and 1.60 g / cm 3 by adjusting the liquid-solid ratio. It has good stability, is applicable to the bottom-hole circulating temperature of 40 - 120°C, and has good compatibility with water-based drilling fluid and cement slurry for cementing. By using a compound expansion plugging material, it takes into account the bridging and expansion effects, and the plugging pressure-bearing capacity > 3.2 MPa; by using an active curable material and a filling material, it can be cured by itself and has the ability to heal cracks; the maximum compressive strength of the cured body after curing for 2 days in a 70°C water bath > 4.2 MPa; the wall-building effect is significant, and the bond strength of the second interface is effectively improved (0.2↑1.8 MPa); and with the extension of time (2d↑7d), the strength of the interface mixed slurry cured body is further developed (7.2↑10.6 MPa). This spacer fluid system is of great significance for improving the pressure-bearing capacity of well sections in formations with developed natural microcracks and highly permeable formations, preventing cementing losses, improving the success rate of primary cementing and the cementing quality, and realizing the long-term integrity and effectiveness of the cementing second interface sealing system.

[0090] The applicant declares that the present invention illustrates the detailed process equipment and process flow of the present invention through the above embodiments, but the present invention is not limited to the above detailed process equipment and process flow, that is, it does not mean that the present invention must rely on the above detailed process equipment and process flow to be implemented. Those skilled in the art should understand that any improvement to the present invention, the equivalent substitution of each raw material of the product of the present invention, the addition of auxiliary components, the selection of specific methods, etc. all fall within the protection scope and the disclosure scope of the present invention.

Claims

1. A plugging and wall-fixing cementing weighting spacer fluid, characterized in that: The raw materials of the isolation fluid include active curing reinforcing material, active filling plugging material, expansion plugging material and water.

2. The isolation liquid according to claim 1, characterized in that: The raw materials of the isolation liquid also include activation materials, suspension stabilization materials, dispersion and dilution materials, fluid loss reducers, defoamers and antifoaming agents.

3. The isolation liquid according to claim 1 or 2, characterized in that: The raw materials described in parts by weight include:

4. The isolation liquid according to any one of claims 1 to 3, characterized in that: The active solidification reinforcing material is blast furnace slag powder.

5. The isolation liquid according to any one of claims 1 to 4, characterized in that: The active filling and plugging material is fly ash; Preferably, the particle size of the fly ash is 0.5-400 μm.

6. The isolation liquid according to any one of claims 1 to 5, characterized in that: The expansion plugging material includes any one of basalt hard fiber, expanded graphite or vermiculite, or a combination of at least two of them; Preferably, the length of the basalt hard fiber is 5 to 15 mm.

7. The isolation liquid according to any one of claims 1 to 6, characterized in that: The activation material includes any one of sodium metasilicate pentahydrate, sodium hydroxide, sodium carbonate or water glass, or a combination of at least two thereof; Preferably, the suspension stabilizing material comprises xanthan gum; Preferably, the dispersing and diluting materials are sodium tripolyphosphate and / or disodium ethylenediaminetetraacetate; Preferably, the fluid loss additive comprises an AMPS copolymer fluid loss additive; Preferably, the defoaming agent comprises glycerol polyether or tributyl phosphate; Preferably, the foam suppressant comprises silicone and / or silicone ether oil.

8. A method for preparing the plugging and wall-fixing cementing weighted spacer fluid according to any one of claims 1 to 7, characterized in that: The preparation method comprises: Mixing the active curing reinforcing material, the active filling plugging material and the expansion plugging material to obtain a solid mixture; The solid mixture is added into water and stirred to obtain the plugging and wall-solidifying cementing weighted spacer fluid.

9. The preparation method according to claim 8, characterized in that: The activation material, suspension stabilization material, dispersion dilution material and fluid loss reducer are mixed with the active solidification reinforcement material, active filling plugging material and expansion plugging material to obtain a solid mixture.

10. The preparation method according to claim 8, characterized in that: Before the solid mixture is added to the water, the water is mixed with the defoamer and the antifoaming agent.

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