Hydrophobic leakproof spacer fluid for well cementation as well as preparation method and application of hydrophobic leakproof spacer fluid

Abstract

The invention provides hydrophobic leakproof spacer fluid for well cementation as well as a preparation method and application of the hydrophobic leakproof spacer fluid. The hydrophobic leakproof spacer fluid for well cementation comprises water, a weighting agent, walnut shells, fibers, a retarder, a hydrophobic macromonomer, a cross-linking agent and the like. A hydrophilic sulfonic acid group in the hydrophobic macromonomer has a complexing effect on calcium ions in mudstone, and an ester group as a hydrophobic group has a hydrophobic effect, so that a fixed arrangement that the hydrophilic sulfonic acid group faces the calcium ions and the hydrophobic group faces outwards is formed in a spacer fluid system. Wherein the hydrophobic groups are arranged to form a barrier layer for water, so that the invasion of water can be prevented, the effect of preventing water erosion is achieved, and the sedimentation of molecules such as a weighting agent can also be prevented. Tests show that the hydrophobic leakproof spacer fluid for well cementation has the pressure bearing capacity of 3.5-8 MPa when being tested by a hole type leakage stoppage instrument for seams of 1-3 mm, the pressure bearing capacity of a stratum is correspondingly improved by 3.5 MPa, and leakage in the well cementation process can be effectively avoided or reduced.

Description

Technical Field

[0001] The present invention belongs to the technical field of oil well cementing, and particularly relates to a hydrophobic leak - proof isolation fluid for well cementing, a preparation method thereof, and an application thereof. Background Technique

[0002] The problem of low return and leakage during the well cementing process is a common technical problem in oil and gas exploration and development at home and abroad. In the case of serious low return and leakage problems, the oil - gas - water layers may be missed and sealed, resulting in the failure of wellbore integrity and sealing, bringing adverse effects to the exploitation and long - term isolation of oil and gas wells, and causing huge losses to the development of oil and gas fields.

[0003] The Shunbei Block is a new discovery in the carbonate marine oil exploration of Sinopec. It is located in the Gobi desert area on the northern edge of the Taklimakan Desert, with an area of about 2,000 square kilometers and rich resources. The bearing capacity of the Permian and Silurian strata in this block is relatively low, bringing great difficulties and risks to the well cementing construction. Leakage often occurs during the well cementing construction, seriously affecting the well cementing quality and completion cycle. According to statistics, the well cementing leakage rate in this block is > 70%, and the casing damage rate is > 15%. The main reason is that the low - pressure and easy - leakage layers in the Permian and Silurian are severely leaking during well cementing, resulting in no cement sheath in the annulus and large sections of free casing, leading to situations such as casing bending, corrosion, and eccentric wear, greatly increasing the production - building cycle and the later exploitation cost, and restricting the progress of production increase.

[0004] In related technologies, the leak - proof isolation fluid for well cementing of Baker Hughes Company abroad is prepared by mixing materials such as nano - polar leak - proof polymer SealBond, SealBond Ultra Plus additive, organic fiber, and weighting agent, and has a good leak - proof effect. It is well - applied in easily - leaking wells and well cementing in foreign markets, greatly reducing the leakage during the well cementing process. However, the polymer material SealBond is expensive, limited by the domestic well cementing cost, with low cost performance and is not conducive to popularization and application.

[0005] Moreover, most of the existing leak - proof fluids are generally used in the drilling process, and relatively few drilling fluids are developed for the well cementing process. Summary of the Invention

[0006] In view of this, the purpose of the present invention is to provide a hydrophobic leak - proof isolation fluid for well cementing, a preparation method thereof, and an application thereof. The leak - proof isolation fluid has low cost and high bearing capacity, and can effectively avoid or reduce the leakage during the well cementing process.

[0007] To achieve this purpose, the present invention adopts the following technical solutions:

[0008] In a first aspect, the present invention provides a hydrophobic leak-proof spacer fluid for well cementing, which comprises, by weight: 100 parts of water, 30 - 50 parts of weighting agent, 10 - 15 parts of walnut shell, 0.5 - 1 part of fiber, 5 - 10 parts of retarder, 1 - 4 parts of hydrophobic macromonomer, and 1 - 4 parts of high-temperature crosslinking agent;

[0009] The hydrophobic macromonomer is obtained by polymerizing sodium methallylsulfonate, sodium 2-(hexylcarbamoyl)methyl-2-sulfoacrylate, allyl polyoxyethylene acetate, and an optional inorganic reinforcing agent.

[0010] Preferably, the mass ratio of sodium methallylsulfonate, sodium 2-(hexylcarbamoyl)methyl-2-sulfoacrylate, allyl polyoxyethylene acetate, and the optional inorganic reinforcing agent is (32 - 36):(4 - 10):(0.2 - 1.0):(0 - 19).

[0011] Preferably, the hydrophobic macromonomer is prepared by the following method:

[0012] Mix sodium methallylsulfonate, sodium 2-(hexylcarbamoyl)methyl-2-sulfoacrylate, allyl polyoxyethylene acetate with water, adjust the pH to 6.0 - 7.0, and react in the presence of an initiator, a crosslinking agent, and an optional reinforcing agent to obtain the hydrophobic macromonomer.

[0013] Preferably, the initiator includes ammonium persulfate and / or sodium bisulfite.

[0014] Preferably, the crosslinking agent includes azobis(2-amidinopropane) dihydrochloride.

[0015] Preferably, the mass ratio of sodium methallylsulfonate, sodium 2-(hexylcarbamoyl)methyl-2-sulfoacrylate, allyl polyoxyethylene acetate, the initiator, the crosslinking agent, and the optional reinforcing agent is (32 - 36):(4 - 10):(0.2 - 1.0):(0.1 - 0.5):(0.2 - 1.7):(0 - 19).

[0016] Preferably, the inorganic reinforcing agent is any one or more of nano-silica, precipitated silica, or ultrafine silica.

[0017] Preferably, the high-temperature crosslinking agent is lactic acid / glycerol zirconium organic or zirconium salt.

[0018] Preferably, the weighting agent is selected from any one or more of barite powder, silica powder, or calcium carbonate.

[0019] Preferably, the fiber is polypropylene fiber.

[0020] In a second aspect, the present invention provides a preparation method of the above-mentioned hydrophobic leak-proof spacer fluid for well cementing, comprising the following steps:

[0021] Mix water, weighting agent, walnut shell, fiber, retarder, hydrophobic macromonomer, and high-temperature crosslinking agent evenly in proportion to obtain a hydrophobic leak-proof isolation fluid for well cementing;

[0022] The hydrophobic macromonomer is obtained by polymerizing sodium methallyl sulfonate, sodium 2-(hexyl acrylate)-2-methyl propane sulfonate, allyl polyoxyethylene acetate, and an optional inorganic reinforcing agent.

[0023] In a third aspect, the present invention provides an application of the above-mentioned hydrophobic leak-proof isolation fluid for well cementing in the process of well cementing, and the environmental temperature of the application is 120 - 180°C.

[0024] Preferably, when the environmental temperature of the application is 120 - 150°C, the high-temperature crosslinking agent in the hydrophobic leak-proof isolation fluid for well cementing is 1 - 3 parts.

[0025] Preferably, when the environmental temperature of the application is 150 - 180°C, the high-temperature crosslinking agent in the hydrophobic leak-proof isolation fluid for well cementing is 3 - 4 parts.

[0026] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0027] The present invention provides a hydrophobic leak-proof isolation fluid for well cementing, which includes components such as water, weighting agent, walnut shell, fiber, retarder, hydrophobic macromonomer, and crosslinking agent. Among them, the walnut shell and fiber serve as bridging support materials, cooperate with the network gel formed by the hydrophobic macromonomer and crosslinking agent, and are extruded to form a soft plug under high differential pressure, which is embedded at the crack to prevent leakage. Moreover, even if the crack expands and shifts due to the continuous expansion of the liquid column differential pressure, the plug can still continue to generate a deformation amount to prevent the occurrence of expansion-type malignant leakage. The hydrophobic macromonomer is obtained by polymerizing sodium methallyl sulfonate, sodium 2-(hexyl acrylate)-2-methyl propane sulfonate, and allyl polyoxyethylene acetate. The hydrophilic sulfonic acid group therein has a complexing effect on calcium ions in the mudstone, while the ester group, as a hydrophobic group, has a hydrophobic effect, and a fixed arrangement will be formed in the isolation fluid system with the hydrophilic sulfonic acid group facing the calcium ions and the hydrophobic group facing outward. Among them, the arrangement of the hydrophobic groups forms a barrier layer against water, which can prevent the intrusion of moisture and play a role in preventing water erosion. At the same time, the presence of the hydrophobic macromonomer can prevent the settlement of molecules such as the weighting agent. Further, the addition of the inorganic reinforcing agent can generate a magnetic field, form a strong electrostatic interaction with the anionic sulfonic acid group, and at the same time, due to the huge specific surface area of the nano-reinforcing agent, a very dense network structure will be formed, enhancing the stability of the molecular structure at high temperatures, thereby improving the temperature resistance performance. In the present invention, the retarder is used to prevent contact between the leak-proof isolation fluid and the traditional cement slurry after entering the well, considering compatibility and adaptability to avoid mixing pollution.

[0028] The density of the hydrophobic leak-proof isolation fluid for well cementing provided by the present invention is 1.3 - 1.4 g / cm3 It has the characteristic of being resistant to high temperatures of 120 to 180 °C. After testing, the hydrophobic leak-proof isolation fluid for well cementing has a pressure-bearing capacity of 3.5 to 8 MPa when tested with a 1 to 3 mm slit-hole type leak plugging instrument, corresponding to an increase in the formation pressure-bearing capacity of 3.5 MPa, which can effectively avoid or reduce leakage during well cementing and can meet the requirements of well cementing construction in easily leaky wells. Specific embodiments

[0029] Next, in combination with the embodiments of the present invention, the technical solutions of the present invention will be clearly and completely described. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative efforts belong to the scope of protection of the present invention.

[0030] Aiming at the problems of high cost and low leak plugging rate of the leak-proof isolation fluid for well cementing in the prior art, the present invention provides a hydrophobic leak-proof isolation fluid for well cementing, which includes, by weight: 100 parts of water, 30 - 50 parts of weighting agent, 10 - 15 parts of walnut shell, 0.5 - 1 part of fiber, 5 - 10 parts of retarder, 1 - 4 parts of hydrophobic macromonomer, and 1 - 4 parts of high-temperature crosslinking agent.

[0031] In the present invention, the hydrophobic leak-proof isolation fluid for well cementing includes 100 parts of water by weight, and the water can be daily fresh water or well site water, brine, etc., and the present invention does not make special restrictions.

[0032] In the present invention, the hydrophobic leak-proof isolation fluid for well cementing includes 30 - 50 parts of weighting agent by weight, preferably 35 - 40 parts. The weighting agent is used to increase the density of the leak-proof isolation fluid. The present invention does not have special restrictions on the type of weighting agent, and specifically can be any one or more of barite powder, silicon powder or calcium carbonate, preferably barite powder with a density of 4.0 - 4.6 g / cm 3 and its particle size is preferably 200 - 300 mesh.

[0033] In the present invention, the hydrophobic leak-proof isolation fluid for well cementing includes 10 - 15 parts of walnut shell by weight, preferably 12 - 13 parts. The walnut shell has a relatively high density. At the same time, the lignin and tannin in the walnut shell have excellent water absorption performance. This water absorption performance can be used to form a firm plugging layer with moderate hardness at the leakage point, providing a bridging support effect, and finally achieving the effect of leak plugging. The present invention does not make special restrictions on the source of the walnut shell, and it can be ordinary commercially available products. The present invention preferably uses walnut shells of 1 - 3 mm.

[0034] It should be noted that the weighting agent and walnut shell can be selected according to the needs of cementing. For example, as an inert material, the weighting agent and walnut shell do not participate in the reaction and play an auxiliary role. The weighting agent can be selected from common weighting materials such as barite powder, iron ore powder, silicon powder, calcium carbonate, etc. used in drilling, and these materials are used to meet the designed density required by the on-site leak-proof isolation fluid. The walnut shell commonly used in drilling for plugging can be used. The selection of 1-3mm is mainly related to the diameter of the casing accessories for cementing. Beyond this particle size, it is not applicable to the cementing project.

[0035] In the present invention, the hydrophobic leak-proof isolation fluid for cementing comprises 0.5-1 part by weight of fibers, preferably 0.6-0.8 part by weight. The fibers are used in combination with the walnut shell to provide a bridging and supporting effect. The present invention does not impose special restrictions on the source of the fibers. Specifically, it can be any one or more of polypropylene fibers, PVA fibers or glass fibers. In some embodiments of the present invention, polypropylene fibers of 2-3mm are preferably used.

[0036] In the present invention, the hydrophobic leak-proof isolation fluid for cementing comprises 5-10 parts by weight of a retarder, preferably 7-9 parts by weight. The retarder is used to prevent the contact between the leak-proof isolation fluid and the traditional cement slurry after entering the well, and to avoid mixing pollution considering compatibility. The present invention does not impose special restrictions on the source of the retarder. Generally, a small molecule high-temperature retarder for oil well cement can be used. For example, it can be any one or more of polycarboxylic acid, organic acid or organic phosphate.

[0037] In the present invention, the hydrophobic leak-proof isolation fluid for cementing comprises 1-4 parts by weight of a high-temperature crosslinking agent, preferably 2-3 parts by weight. The high-temperature crosslinking agent forms a network gel with the hydrophobic macromonomer, and cooperates with the bridging and supporting material formed by the walnut shell and fibers to form a soft plug under high pressure difference and embed it at the crack, which can prevent leakage. In the present invention, the high-temperature crosslinking agent can specifically be selected from lactic acid / glycerol zirconium organic.

[0038] In the present invention, the hydrophobic leak-proof isolation fluid for cementing comprises 1-4 parts by weight of a hydrophobic macromonomer, preferably 2-3 parts by weight. The hydrophobic macromonomer is obtained by polymerizing sodium methallylsulfonate, sodium 6-hexyl itaconate propylsulfonate, allyl polyoxyethylene acetate and an optional inorganic reinforcing agent. Among them, the inorganic reinforcing agent can specifically be selected from any one or more of nano-silica, white carbon black or ultrafine silicon.

[0039] In some embodiments of the present invention, the hydrophobic macromonomer can be prepared by the following method: Mix sodium methallylsulfonate, sodium 6-hexyl itaconate propylsulfonate, allyl polyoxyethylene acetate with water, adjust the pH to 6.0-7.0, and react in the presence of an initiator, a crosslinking agent and an optional reinforcing agent to obtain the hydrophobic macromonomer.

[0040] Among them, the initiator preferably includes ammonium persulfate and / or sodium bisulfite, more preferably includes ammonium persulfate and sodium bisulfite; the crosslinking agent preferably includes azodiisobutyramidine hydrochloride. Preferably, in the present invention, the mass ratio of sodium methallylsulfonate, sodium hexyl itaconate propylsulfonate, allyl polyoxyethylene acetate, initiator, crosslinking agent and optional inorganic reinforcing agent is (32 - 36):(4 - 10):(0.2 - 1.0):(0.1 - 0.5):(0.2 - 1.7):(0 - 19).

[0041] In the present invention, on the one hand, the hydrophilic sulfonic acid group in the hydrophobic macromonomer has a complexing effect on calcium ions in the mudstone, while the ester group has a hydrophobic effect. In the spacer fluid system, a fixed arrangement will be formed with the hydrophilic sulfonic acid group facing the calcium ions and the hydrophobic group facing outwards. The hydrophobic groups are arranged to form a barrier layer against water, thereby preventing the intrusion of moisture and playing a role in preventing water erosion. At the same time, the sulfonic acid group and ether bond in the molecular structure have a complexing effect with the high-temperature crosslinking agent, and a certain network structure can be formed, having an anti-settling effect. On the other hand, the anionic sulfonic acid group can form a strong electrostatic interaction, forming a very dense network structure and playing a role in reducing fluid loss. The addition of the inorganic reinforcing agent can enhance the water resistance of the plugging plug. At the same time, since the inorganic reinforcing agent is nanoscale, it has a huge specific surface area, will form a very dense network structure, and enhance the stability of the molecular structure at high temperature, thereby improving the temperature resistance performance.

[0042] The present invention also provides a preparation method of the above-mentioned hydrophobic leak-proof spacer fluid for cementing, including the following steps:

[0043] Mix water, weighting agent, walnut shell, fiber, retarder, hydrophobic macromonomer, and high-temperature crosslinking agent evenly in proportion to obtain the hydrophobic leak-proof spacer fluid for cementing;

[0044] The hydrophobic macromonomer is obtained by polymerizing sodium methallylsulfonate, sodium hexyl itaconate propylsulfonate, allyl polyoxyethylene acetate and optional inorganic reinforcing agent.

[0045] According to the present invention, by mixing water, weighting agent, walnut shell, fiber, retarder, hydrophobic macromonomer, and high-temperature crosslinking agent evenly in proportion, the hydrophobic leak-proof spacer fluid for cementing can be obtained. Among them, the proportions of the above components are as described in the relevant content of the above technical solution, and will not be elaborated here. The mixing is preferably carried out under stirring conditions, and the stirring speed is preferably 1500 - 5000 r / min, more preferably 2000 - 4000 r / min.

[0046] The present invention also provides an application of the above-mentioned hydrophobic leak-proof spacer fluid for cementing in the cementing process, and the environmental temperature of the application is 120 - 180 °C.

[0047] In some embodiments of the present invention, it is preferred to raise the temperature and increase the pressure of the hydrophobic leak-proof isolation fluid for well cementing obtained on a slotted-hole plugging instrument. The experimental conditions are as follows: in the first stage, the temperature-raising time is 60 min and the target temperature is 120 °C; in the second stage, after reaching the target temperature, keep the temperature constant and increase the pressure to 0 - 8 MPa; in the third stage, keep the pressure stable for 5 min and observe whether leakage occurs in the slotted plates of 1 mm, 2 mm, and 3 mm. If leakage occurs, record the test pressure at the time of leakage to determine its pressure-bearing capacity.

[0048] After testing, the hydrophobic leak-proof isolation fluid for well cementing provided by the present invention has a pressure-bearing capacity of 3.5 - 8 MPa when tested on a 1 - 3 mm slotted-hole plugging instrument, corresponding to an increase in the formation pressure-bearing capacity of 3.5 MPa, which can effectively avoid or reduce leakage during well cementing and can meet the requirements of well cementing construction in easily leaky wells.

[0049] It should be noted that in the present invention, when the ambient temperature at which the hydrophobic leak-proof isolation fluid for well cementing is applied is 120 - 150 °C, the high-temperature crosslinking agent in the hydrophobic leak-proof isolation fluid for well cementing is 1 - 3 parts; when the ambient temperature at which it is applied is 150 - 180 °C, the high-temperature crosslinking agent in the hydrophobic leak-proof isolation fluid for well cementing is 3 - 4 parts. This is because the crosslinking effect is damaged at the high-temperature stage and more crosslinking agent needs to be consumed.

[0050] It should be emphasized particularly that the hydrophobic leak-proof isolation fluid provided by the present invention is specifically used for the well cementing process. Different from well drilling, during well drilling for plugging leaks, the safety risk is small, and different plugging schemes can be repeatedly tried until the leakage channel is plugged and the drilling fluid can establish normal circulation to maintain normal drilling. However, for well cementing, after the well drilling stage is completed, special-sized casing, casing accessories, and tools are run into the wellbore. The inner diameter of the tools and accessories becomes smaller, and the outer annulus becomes narrow. Traditional drilling plugging slurries cannot be used for well cementing projects, which will directly block the well cementing casing or annulus and lead to the failure of the entire well cementing. The hydrophobic leak-proof isolation fluid referred to in the present invention can be safely used in well cementing projects. The leak-proof isolation fluid can flow in the small inner diameter of the well cementing casing and narrow places without forming blockages. During the process of leaking into small cracks, under high-pressure difference conditions, small molecules begin to aggregate into bundles and crosslink into a network to form a plugging plug. The formation process is rapid and can quickly lock in moisture, ensuring the safety of the entire well cementing construction.

[0051] To further illustrate the present invention, the following comparative examples and examples are described in detail below. The experimental raw materials used in the following examples of the present invention are all commercially available products.

[0052] Preparation Example 1

[0053] A hydrophobic macromonomer provided in this preparation example is prepared as follows:

[0054] 30 parts of sodium methallylsulfonate, 4 parts of sodium 2-(hexylcarbamoyl)methyl-2-sulfoethyl acrylate, and 0.4 part of allyl polyoxyethylene acetate are dissolved in 200 parts of deionized water. The pH of the system is adjusted to 6.5. 0.25 part of azodiisobutyramidine hydrochloride is added and stirred evenly. Then it is transferred to a 250 ml three-necked flask. Under the stirring condition of 100 r / min, the temperature is raised to 60 °C. 0.2 part of ammonium persulfate is dissolved in 50 parts of deionized water and added dropwise into the three-necked flask within 2 h. After the addition is completed, the reaction continues at 60 °C for 4 h. Then 0.45 part of sodium bisulfite is dissolved in 50 parts of deionized water, added to the three-necked flask and stirred for 5 min. After reacting for another 30 minutes, the temperature is lowered to room temperature to obtain a polymer viscous liquid. Then an enhancer is added, the stirring speed is adjusted to 600 r / min and stirred for 1 h. After cooling, a hydrophobic macromonomer polymer is finally obtained. Then the polymer is transferred to a microwave dryer and formed into a sheet solid after microwave drying, with a water content of less than 6%. Then the sheet solid is put into an air classifier mill and an 80-mesh hydrophobic macromonomer powder is obtained through air classification and grinding.

[0055] Comparative Preparation Example 1

[0056] Compared with Preparation Example 1, the difference is only that 30 parts of sodium methallylsulfonate, 4 parts of sodium 2-(hexylcarbamoyl)methyl-2-sulfoethyl acrylate, and 0.4 part of allyl polyoxyethylene acetate for synthesizing the macromonomer are equally replaced with a cationic polyacrylamide flocculant for plugging, and the cationic polyacrylamide is polymerized from acrylamide and methylacryloyloxyethyltrimethylammonium chloride by aqueous solution polymerization, with a molecular weight of 4 million, and the remaining parameters and steps are the same as those in Preparation Example 1.

[0057] Comparative Preparation Example 2

[0058] Compared with Preparation Example 1, the difference is only that 30 parts of sodium methallylsulfonate, 4 parts of sodium 2-(hexylcarbamoyl)methyl-2-sulfoethyl acrylate, and 0.4 part of allyl polyoxyethylene acetate for synthesizing the macromonomer are equally replaced with a sulfomethylated phenolic resin high-viscosity plugging agent for drilling, and the remaining parameters and steps are the same as those in Preparation Example 1.

[0059] Comparative Preparation Example 3

[0060] Compared with Preparation Example 1, the difference is only that 30 parts of sodium methallylsulfonate, 4 parts of sodium 2-(hexylcarbamoyl)methyl-2-sulfoethyl acrylate, and 0.4 part of allyl polyoxyethylene acetate for synthesizing the macromonomer are equally replaced with 34.4 parts of a sulfonated acrylic resin plugging agent, and the remaining parameters and steps are the same as those in Preparation Example 1.

[0061] Comparative Preparation Example 4

[0062] Compared with Preparation Example 1, the difference is only that 30 parts of sodium methallylsulfonate, 4 parts of sodium hexyl itaconate propylsulfonate, and 0.4 parts of allyl polyoxyethylene acetate are synthesized into a macromonomer and are equally replaced with a sulfonated asphalt plugging agent, and the remaining parameters and steps are the same as those in Preparation Example 1.

[0063] Index evaluation

[0064] Taking the hydrophobic macromonomers obtained in Comparative Examples 1-4 and Preparation Example 1 as samples, after high-temperature aging for 2 h, the viscosity change before and after aging was evaluated. The results are shown in Table 1 below (judging from experience, the viscosity retention rate is greater than 50%, and not less than 20 mPa·s is up to the standard, otherwise it is not up to the standard):

[0065] Table 1

[0066]

[0067]

[0068] The hydrophobic macromonomers used in the following Examples and Comparative Examples are all the hydrophobic macromonomers obtained in Preparation Example 1.

[0069] Example 1

[0070] This example provides a hydrophobic leak-proof isolation fluid for well cementing, and its preparation method is as follows:

[0071] Weigh 100 parts of fresh water, 40 parts of weighting agent, 10 parts of walnut shell, 0.5 part of fiber, 5 parts of high-temperature retarder, 1.5 parts of high-temperature crosslinking agent, and 1.5 parts of hydrophobic macromonomer; mix and stir the above materials evenly at a speed of 2000 r / min to obtain a hydrophobic leak-proof isolation fluid system for well cementing.

[0072] The obtained hydrophobic leak-proof isolation fluid system for well cementing was heated and pressurized on a fracture and pore plugging instrument. The experimental conditions were as follows: the heating time in the first stage was 60 min, and the target temperature was 120 °C; in the second stage, after reaching the target temperature, keep the temperature constant and pressurize from 0 to 8 MPa; in the third stage, keep the pressure stable for 5 min and observe whether there is leakage in the 1-3 mm slit plate. If there is leakage, record the test pressure at the time of leakage to determine its pressure-bearing capacity. The experimental results are shown in Table 1.

[0073] Example 2

[0074] This example provides a hydrophobic leak-proof isolation fluid for well cementing, and its preparation method is as follows:

[0075] Weigh 100 parts of fresh water, 40 parts of weighting agent, 12 parts of walnut shell, 0.5 part of fiber, 5 parts of high-temperature retarder, 1.5 parts of high-temperature crosslinking agent, and 2.0 parts of hydrophobic macromonomer; mix and stir the above materials evenly at a speed of 2000 r / min to obtain a hydrophobic leak-proof isolation fluid system for well cementing.

[0076] Heat up and pressurize the obtained hydrophobic leak-proof isolation fluid system for well cementing on a slit-hole plugging instrument. The experimental conditions are as follows: in the first stage, the heating time is 60 min and the target temperature is 130 °C; in the second stage, after reaching the target temperature, keep the temperature constant and pressurize to 0 - 8 MPa; in the third stage, keep the pressure stable for 5 min and observe whether the 1 - 3 mm slit plate leaks. If leakage occurs, record the test pressure at the time of leakage to determine its pressure-bearing capacity. The experimental results are shown in Table 1.

[0077] Example 3

[0078] This example provides a hydrophobic leak-proof isolation fluid for well cementing, and its preparation method is as follows:

[0079] Weigh 100 parts of fresh water, 40 parts of weighting agent, 12 parts of walnut shell, 0.5 part of fiber, 5 parts of high-temperature retarder, 3.0 parts of high-temperature crosslinking agent, and 3.0 parts of hydrophobic macromonomer; mix and stir the above materials evenly at a speed of 2000 r / min to obtain a hydrophobic leak-proof isolation fluid system for well cementing.

[0080] Heat up and pressurize the obtained hydrophobic leak-proof isolation fluid system for well cementing on a slit-hole plugging instrument. The experimental conditions are as follows: in the first stage, the heating time is 60 min and the target temperature is 150 °C; in the second stage, after reaching the target temperature, keep the temperature constant and pressurize to 0 - 8 MPa; in the third stage, keep the pressure stable for 5 min and observe whether the 1 - 3 mm slit plate leaks. If leakage occurs, record the test pressure at the time of leakage to determine its pressure-bearing capacity. The experimental results are shown in Table 1.

[0081] Example 4

[0082] This example provides a hydrophobic leak-proof isolation fluid for well cementing, and its preparation method is as follows:

[0083] Weigh 100 parts of fresh water, 40 parts of weighting agent, 14 parts of walnut shell, 0.5 part of fiber, 5 parts of high-temperature retarder, 4 parts of high-temperature crosslinking agent, and 3.5 parts of hydrophobic macromonomer; mix and stir the above materials evenly at a speed of 2000 r / min to obtain a hydrophobic leak-proof isolation fluid system for well cementing.

[0084] The obtained hydrophobic leak - proof isolation fluid system for well cementing is heated and pressurized on a slit - hole plugging instrument. The experimental conditions are as follows: In the first stage, the heating time is 60 min and the target temperature is 160 °C; in the second stage, after reaching the target temperature, it is kept at a constant temperature and pressurized to 0 - 8 MPa; in the third stage, it is kept at a stable pressure for 5 min to observe whether the 1 - 3 mm slit plate leaks. If leakage occurs, record the test pressure at the time of leakage to determine its pressure - bearing capacity. The experimental results are shown in Table 1.

[0085] Example 5

[0086] This example provides a hydrophobic leak - proof isolation fluid for well cementing, and its preparation method is as follows:

[0087] Weigh 100 parts of fresh water, 40 parts of weighting agent, 14 parts of walnut shell, 0.5 part of fiber, 5 parts of high - temperature retarder, 4 parts of high - temperature cross - linker, and 4.0 parts of hydrophobic macromonomer; mix and stir the above materials evenly at a speed of 2000 r / min to obtain the hydrophobic leak - proof isolation fluid system for well cementing.

[0088] The obtained hydrophobic leak - proof isolation fluid system for well cementing is heated and pressurized on a slit - hole plugging instrument. The experimental conditions are as follows: In the first stage, the heating time is 60 min and the target temperature is 180 °C; in the second stage, after reaching the target temperature, it is kept at a constant temperature and pressurized to 0 - 8 MPa; in the third stage, it is kept at a stable pressure for 5 min to observe whether the 1 - 3 mm slit plate leaks. If leakage occurs, record the test pressure at the time of leakage to determine its pressure - bearing capacity. The experimental results are shown in Table 1.

[0089] Comparative Example 1

[0090] The hydrophobic leak - proof isolation fluid for well cementing provided in this comparative example has no high - temperature cross - linker and hydrophobic macromonomer. The specific preparation method is as follows:

[0091] Weigh 100 parts of fresh water, 40 parts of weighting agent, 10 parts of walnut shell, 0.5 part of fiber, and 5 parts of high - temperature retarder; mix and stir the above materials evenly at a speed of 2000 r / min to obtain the hydrophobic leak - proof isolation fluid system for well cementing.

[0092] The obtained hydrophobic leak - proof isolation fluid system for well cementing is heated and pressurized on a slit - hole plugging instrument. The experimental conditions are as follows: In the first stage, the heating time is 60 min and the target temperature is 120 °C; in the second stage, after reaching the target temperature, it is kept at a constant temperature and pressurized to 0 - 8 MPa; in the third stage, it is kept at a stable pressure for 5 min to observe whether the 1 mm slit plate leaks. If leakage occurs, record the test pressure at the time of leakage to determine its pressure - bearing capacity. The experimental results are shown in Table 1.

[0093] Comparative Example 2

[0094] The hydrophobic leak - proof isolation fluid for well cementing provided in this comparative example has no high - temperature cross - linker. The specific preparation method is as follows:

[0095] Weigh 100 parts of fresh water, 40 parts of weighting agent, 12 parts of walnut shell, 0.5 part of fiber, 5 parts of high-temperature retarder, and 2.0 parts of hydrophobic macromonomer; mix and stir the above materials evenly at a speed of 2000 r / min to obtain a hydrophobic leak-proof isolation fluid system for cementing.

[0096] Heat up and pressurize the obtained hydrophobic leak-proof isolation fluid system for cementing on a slit-hole plugging instrument. The experimental conditions are as follows: in the first stage, the heating time is 60 min and the target temperature is 130 °C; in the second stage, after reaching the target temperature, keep the temperature constant and pressurize to 0 - 8 MPa; in the third stage, keep the pressure stable for 5 min and observe whether the 1 - 3 mm slit plate leaks. If leakage occurs, record the test pressure at the time of leakage to determine its pressure-bearing capacity. The experimental results are shown in Table 1.

[0097] Comparative Example 3

[0098] The hydrophobic leak-proof isolation fluid for cementing provided in this comparative example has a relatively low dosage of high-temperature crosslinking agent. The specific preparation method is as follows:

[0099] Weigh 100 parts of fresh water, 40 parts of weighting agent, 12 parts of walnut shell, 0.5 part of fiber, 5 parts of high-temperature retarder, 0.5 part of high-temperature crosslinking agent, and 3.0 parts of hydrophobic macromonomer; mix and stir the above materials evenly at a speed of 2000 r / min to obtain a hydrophobic leak-proof isolation fluid system for cementing.

[0100] Heat up and pressurize the obtained hydrophobic leak-proof isolation fluid system for cementing on a slit-hole plugging instrument. The experimental conditions are as follows: in the first stage, the heating time is 60 min and the target temperature is 150 °C; in the second stage, after reaching the target temperature, keep the temperature constant and pressurize to 0 - 8 MPa; in the third stage, keep the pressure stable for 5 min and observe whether the 1 - 3 mm slit plate leaks. If leakage occurs, record the test pressure at the time of leakage to determine its pressure-bearing capacity. The experimental results are shown in Table 1.

[0101] Comparative Example 4

[0102] Weigh 100 parts of fresh water, 40 parts of weighting agent, 14 parts of walnut shell, 0.5 part of fiber, 5 parts of high-temperature retarder, 3.0 parts of high-temperature crosslinking agent, and 1.0 part of hydrophobic macromonomer; mix and stir the above materials evenly at a speed of 2000 r / min to obtain a hydrophobic leak-proof isolation fluid system for cementing.

[0103] The obtained hydrophobic leak-proof isolation fluid system for well cementing was heated and pressurized on a slit-hole plugging instrument. The experimental conditions were as follows: in the first stage, the heating time was 60 min and the target temperature was 160 °C; in the second stage, after reaching the target temperature, it was kept at a constant temperature and pressurized to 0 - 8 MPa; in the third stage, it was kept at a stable pressure for 5 min to observe whether leakage occurred in the 1 - 3 mm slit plate. If leakage occurred, the test pressure at the time of leakage was recorded to determine its pressure-bearing capacity. The experimental results are shown in Table 1.

[0104] Comparative Example 5

[0105] Weigh 100 parts of fresh water, 40 parts of weighting agent, 14 parts of walnut shell, 0.5 part of fiber, 5 parts of high-temperature retarder, 4.0 parts of high-temperature crosslinking agent, and 2.0 parts of hydrophobic macromonomer; mix and stir the above materials evenly at a speed of 2000 r / min to prepare a hydrophobic leak-proof isolation fluid system for well cementing.

[0106] The obtained hydrophobic leak-proof isolation fluid system for well cementing was heated and pressurized on a slit-hole plugging instrument. The experimental conditions were as follows: in the first stage, the heating time was 60 min and the target temperature was 180 °C; in the second stage, after reaching the target temperature, it was kept at a constant temperature and pressurized to 0 - 8 MPa; in the third stage, it was kept at a stable pressure for 5 min to observe whether leakage occurred in the 1 - 3 mm slit plate. If leakage occurred, the test pressure at the time of leakage was recorded to determine its pressure-bearing capacity. The experimental results are shown in Table 1.

[0107] Table 1

[0108]

[0109] As can be seen from Table 1, as the temperature increases, the hydrophobic macromonomer and crosslinking agent increase in a certain proportion, and the plugging effect is better. However, there is a range of action between the crosslinking agent and the hydrophobic macromonomer. Simply increasing the crosslinking agent does not have a significant effect. As the width of the slit plate of the plugging instrument increases, the pressure-bearing capacity of the same formula decreases as the slit plate gets larger, because the supporting force of the formed plugging plug decreases in the wide slit.

[0110] Compared with the examples, after the monomer ratio and synthesis conditions are changed in the comparative examples, the number of active groups decreases and the molecular structure changes. Adding a crosslinking agent cannot form a good three-dimensional crosslinked network structure, so the plugging effect in the cracks is poor.

[0111] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present invention. Various modifications to these embodiments will be obvious to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to these embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A hydrophobic leak-proof isolation fluid for well cementing, characterized in that, It includes, by weight parts: 100 parts of water, 30 - 50 parts of weighting agent, 10 - 15 parts of walnut shell, 0.5 - 1 part of fiber, 5 - 10 parts of retarder, 1 - 4 parts of hydrophobic macromonomer, 1 - 4 parts of high-temperature crosslinking agent; The hydrophobic macromonomer is obtained by polymerizing sodium methallyl sulfonate, sodium 2-(hexyl acrylate)-1-propanesulfonate, allyl polyoxyethylene acetate and an optional inorganic reinforcing agent.

2. The hydrophobic leak-proof isolation fluid for well cementing according to claim 1, characterized in that, The mass ratio of sodium methallyl sulfonate, sodium 2-(hexyl acrylate)-1-propanesulfonate, allyl polyoxyethylene acetate and the optional inorganic reinforcing agent is (32 - 36):(4 - 10):(0.2 - 1.0):(0 - 19).

3. The hydrophobic leak-proof isolation fluid for well cementing according to claim 1 or 2, characterized in that, The hydrophobic macromonomer is prepared by the following method: Mix sodium methallyl sulfonate, sodium 2-(hexyl acrylate)-1-propanesulfonate and allyl polyoxyethylene acetate with water, adjust the pH to 6.0 - 7.0, and react in the presence of an initiator, a crosslinking agent and an optional reinforcing agent to obtain the hydrophobic macromonomer.

4. The hydrophobic leak-proof isolation fluid for well cementing according to claim 3, wherein, The initiator includes ammonium persulfate and / or sodium bisulfite; The crosslinking agent includes azobis(2-amidinopropane) hydrochloride.

5. The hydrophobic leak-proof isolation fluid for well cementing according to claim 3 or 4, characterized in that, The mass ratio of sodium methallyl sulfonate, sodium 2-(hexyl acrylate)-1-propanesulfonate, allyl polyoxyethylene acetate, the initiator, the crosslinking agent and the optional inorganic reinforcing agent is (32 - 36):(4 - 10):(0.2 - 1.0):(0.1 - 0.5):(0.2 - 1.7):(0 - 19).

6. The hydrophobic leak-proof isolation fluid for well cementing according to claim 1, wherein The inorganic reinforcing agent is any one or more of nano-silica, white carbon black or ultrafine silicon; The high-temperature crosslinking agent is lactic acid / glycerol zirconium organic or zirconium salt.

7. The hydrophobic leak-proof isolation fluid for well cementing according to claim 1, characterized in that, The weighting agent is selected from any one or more of barite powder, silicon powder or calcium carbonate; The fiber is polypropylene fiber.

8. A preparation method of the hydrophobic leak-proof isolation fluid for well cementing according to any one of claims 1 to 7, characterized in that, It includes the following steps: Mix water, weighting agent, walnut shell, fiber, retarder, hydrophobic macromonomer and high-temperature crosslinking agent evenly in proportion to obtain a hydrophobic leak-proof spacer fluid for well cementing; The hydrophobic macromonomer is obtained by polymerizing sodium methallyl sulfonate, sodium 2-(hexyl acrylate)-1-propanesulfonate, allyl polyoxyethylene acetate and an optional inorganic reinforcing agent.

9. Use of the hydrophobic leak-proof isolation fluid for well cementing according to any one of claims 1 to 8 in the well cementing process, characterized in that, The environmental temperature for the application is 120 - 180 °C.

10. The application according to claim 9, characterized in that, When the environmental temperature for the application is 120 - 150 °C, the high-temperature crosslinking agent in the hydrophobic leak-proof spacer fluid for well cementing is 1 - 3 parts; When the environmental temperature for the application is 150 - 180 °C, the high-temperature crosslinking agent in the hydrophobic leak-proof spacer fluid for well cementing is 3 - 4 parts.

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