Early strength agent for large temperature difference well cementing slurry and preparation method thereof

Abstract

The application discloses an early strength agent for a large-temperature-difference well cementing slurry and a preparation method thereof. The early strength agent comprises the following components in parts by weight: 40-60 parts of nano quartz powder; 32-45 parts of nano calcined kaolin; 5-10 parts of a dispersing agent; and 3-5 parts of a silane coupling agent. In the preparation of the early strength agent, the nano quartz powder and the nano calcined kaolin are subjected to surface modification by using the dispersing agent and the silane coupling agent, so that the problem that the strength development of the large-temperature-difference well cementing slurry is slow in a low-temperature area is reduced, the well cementing quality of a long cementing section is ensured, and efficient and safe exploitation of deep oil and gas resources is ensured.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of oil and gas well cementing, in particular to an early strength agent for cementing slurry with large temperature difference and a preparation method thereof. BACKGROUND

[0002] With the continuous development of domestic economy, the demand for oil and gas resources is increasing, and the shallow easy-to-produce oil and gas resources are decreasing, and the oilfield exploration and development has moved to deep formations.

[0003] With the increase in the number of deep and ultra-deep wells, the number of long cementing sections is increasing. At present, long cementing sections mainly use one-time cementing technology, which faces the problems of long one-time return cementing section, large temperature difference (> 90℃) at the top and bottom of the cementing section, and easy super-retardation of the top cement slurry, which not only seriously affects the cementing quality and delays the drilling operation process, but also increases the safety risk of subsequent drilling operation. In the long cementing section of deep and ultra-deep wells, the bottom hole static temperature can reach above 150℃, and the temperature difference with the top of the well can reach above 90℃. Due to the large temperature difference between the top and bottom, the cement slurry pumping will experience the process from low temperature to high temperature and then to low temperature. In order to ensure the safe construction time of long cementing section, high-temperature retarder is usually added to prolong the pumping time of cement slurry. However, under the action of high-temperature retarder, the top of the cement slurry column is prone to retardation or super-retardation in the low-temperature section, and the cement slurry strength develops slowly or even does not develop, thereby affecting the construction progress, efficiency and cementing quality. Improving the cementing process cannot fundamentally solve the problem of long cementing with large temperature difference, therefore, developing excellent additive suitable for large temperature difference cementing is an effective measure to solve the problem of long cementing with large temperature difference.

[0004] At present, the main solution to the problem of super-retardation of the top cement slurry during long cementing is to develop high-temperature and large-temperature-difference retarder, however, the existing high-temperature and large-temperature-difference retarder still has many problems that are difficult to solve, such as: dosage sensitivity, unstable retardation effect, serious high-temperature cement slurry settlement, poor compatibility with high-temperature additive, and easy to cause abnormal gelation, which is specifically manifested as the high-temperature thickening curve is prone to "bulging" and "stepping" and other adverse phenomena. For the problem of slow strength development of large temperature difference cementing slurry in low temperature area, oil well cement early strength agent can also be added to solve it. The early strength agent used in oil well cement at present mainly includes the following types: (1) inorganic salt: mainly including chloride, sulfate, carbonate, nitrate, nitrite and other inorganic substances; (2) organic: mainly including calcium formate, formamide, alcohol amine and other organic substances; (3) nanometer material: mainly including nanometer silicon dioxide, nanometer calcium carbonate and other materials; (3) composite early strength agent: the above early strength agents are compounded in proportion.

[0005] However, the existing oil well cement early strength agent is not applicable to the large temperature difference well cementing slurry, and has the following problems: (1) the existing inorganic salt early strength agent has a great influence on the high temperature thickening time of the cement slurry, the high temperature promotes the coagulation obviously, and the high temperature thickening time of the cement slurry is shortened, and it is difficult to adjust by increasing the amount of the retarder. In addition, it may cause abnormal cementing of the cement slurry, causing the cement thickening process to appear "core" and other phenomena, which is manifested as the appearance of "drum" or "step" in the thickening curve, and further leading to poor well cementing quality; (2) the existing organic early strength agent is sensitive to the amount, and when the amount is small, the early strength effect is not obvious, and when the amount is too large, the cement slurry may appear transition retardation, and the matching with the high temperature additive is poor; (3) the existing nano material early strength agent has high surface energy and a large number of polar hydroxyl groups on the surface due to the nano size, which easily agglomerate together in water, thereby forming a large agglomerate, which cannot be uniformly dispersed in the cement slurry, and the crystal nucleus effect cannot be effectively exerted, resulting in poor early strength effect; (4) the compounding of the composite early strength agent is difficult, and it is difficult to be applied to the large temperature difference well cementing slurry system.

[0006] In view of the above problems, the present application provides an early strength agent for large temperature difference well cementing slurry to solve the problem that the existing large temperature difference well cementing slurry has slow development of strength at the top of the well, which affects the construction progress and well cementing quality. SUMMARY

[0007] The purpose of the present application is to provide an early strength agent for large temperature difference well cementing slurry and a preparation method thereof, to reduce the problem of slow development of strength of the temperature difference well cementing slurry in the low temperature area, so as to ensure the well cementing quality of the long cementing section and ensure the efficient and safe exploitation of deep oil and gas resources.

[0008] To achieve the above-mentioned purpose, the technical scheme adopted by the present application is as follows:

[0009] The early strength agent for large temperature difference well cementing slurry provided by the present application comprises the following components by weight fraction:

[0010] Nanometer quartz powder 40-60 parts;

[0011] Nanometer calcined kaolin 32-45 parts;

[0012] Dispersing agent 5-10 parts;

[0013] Silane coupling agent 3-5 parts.

[0014] In some embodiments of the present application, the SiO2 content in the nanometer quartz powder is ≥99.9wt%.

[0015] In some embodiments of the present application, the particle size of the nanometer quartz powder is in the range of 300-400nm.

[0016] In some embodiments of the present application, the nano-calcined kaolin has a SiO2 content of ≥54wt%, an Al2O3 content of ≥32wt%, and an Fe2O3 content of <3wt%.

[0017] In some embodiments of the present application, the nano-calcined kaolin has a particle size ranging from 200 to 300 nm.

[0018] In some embodiments of the present application, the dispersant is a polycarboxylic acid series superplasticizer, and the chemical composition is modified polycarboxylic acid salt; the active ingredient in the modified polycarboxylic acid salt is ≥90%, and the molecular weight is between 10,000 and 30,000.

[0019] In some embodiments of the present application, the silane coupling agent is one or more of KH550, KH560, KH570, and KH172.

[0020] In some embodiments of the present application, the effective ingredient in the silane coupling agent is ≥98%.

[0021] The present application also provides a preparation method of the early strength agent for large temperature difference well cementing slurry, comprising the following steps:

[0022] Step 1: 400-800 parts of anhydrous ethanol and 100-300 parts of deionized water are weighed according to the mass fraction and fully mixed to obtain a first mixed solution; 3-5 parts of a silane coupling agent is weighed and added to the first mixed solution, and after ultrasonic dispersion for 1 h, a second mixed solution is obtained; the pH value of the second mixed solution is adjusted to 4-5 by using anhydrous oxalic acid to obtain a third mixed solution, the third mixed solution is a modified solution of nano-quartz powder and nano-calcined kaolin, and the third mixed solution is transferred to a reaction kettle with heating, stirring and condensation reflux device; preferably, the anhydrous ethanol is 600 parts, and the deionized water is 200 parts;

[0023] Step 2: 40-60 parts of nano-quartz powder, 32-45 parts of nano-calcined kaolin, and 5-10 parts of a dispersant are weighed according to the mass fraction and fully mixed to obtain a mixture; and the mixture is slowly added to the third mixed solution to obtain a fourth mixed solution; the reflux device in the reaction kettle is opened, the temperature is raised to 60℃, and the stirring speed is controlled at 400-500 r / min, so that the fourth mixed solution is reacted for 3 h, the reaction liquid is removed, and a fifth mixed solution is obtained;

[0024] Step 3: The fifth mixed solution is vacuum filtered, the filtered product is washed with anhydrous ethanol, and then the filtered product is vacuum dried to obtain an early strength agent for large temperature difference well cementing slurry; preferably, the drying temperature of the vacuum drying is 50℃, and the drying time is 6 h.

[0025] The early strength agent for the large temperature difference well cementing slurry provided in the present application comprises four components of nano quartz powder, nano calcined kaolin, dispersant and silane coupling agent. In order to avoid the agglomeration of the nano quartz powder and the nano calcined kaolin and affect the early strength effect, the dispersant and the silane coupling agent are used to modify the surface of the nano quartz powder and the nano calcined kaolin. The nano quartz powder and the nano calcined kaolin are basically not reacted with the cement hydration product at normal temperature, and can be reacted with CH (calcium hydroxide) generated by the cement hydration at high temperature (> 110 DEG C) to generate nano hydrated calcium silicate and nano hydrated calcium aluminate. The above-mentioned hydration product can act as a crystal seed in the cement slurry, form a large number of nucleation sites, promote the formation of crystal nucleus, effectively stimulate the cement hydration reaction, and basically have no effect on the hydration induction period and the initial stage of the hydration acceleration period, but can significantly improve the hydration rate in the later stage of the cement acceleration period, and the acceleration process has a self-catalytic effect, so that the cement hydration product is more dense and has better cementation, thereby improving the early strength of the cement, and basically having no effect on the high temperature thickening time. In addition, since the components of the nano hydrated calcium silicate and the nano hydrated calcium aluminate, which are the hydration products of the nano quartz powder and the nano calcined kaolin, are similar to the cement hydration product, they have good matching with the high temperature additive of the large temperature difference well cementing slurry.

[0026] Compared with the prior art, the present application has the following beneficial effects:

[0027] (1) The early strength agent provided by the present application has no obvious promoting effect on the hydration rate in the initial stage of the hydration reaction of the large temperature difference well cementing slurry, basically has no change in the hydration induction period, mainly acts on the later stage of the cement hydration acceleration period, promotes the strength development in the later stage of the cement hydration acceleration period, and therefore has little effect on the high temperature thickening time.

[0028] The early strength agent of the present application is reacted with CH (calcium hydroxide) generated by the cement hydration at high temperature to generate nano hydrated calcium silicate and nano hydrated calcium aluminate. The above-mentioned nano hydrated product can play a good crystal nucleus effect in the cement slurry, accelerate the hydration rate in the later stage of the cement hydration acceleration period, promote the generation of hydrated calcium silicate and the growth of calcium vanadate, and enhance the density and cementation ability of the hydration product, thereby effectively promoting the strength development of the large temperature difference well cementing slurry in the low temperature region, and ensuring the early strength of the top low temperature section of the long cementing section large temperature difference well cementing slurry.

[0029] (2) The effective components and hydration products of the early strength agent of the present application are similar to the main mineral components and hydration products of the large temperature difference well cementing slurry, and therefore the early strength agent has good adaptability in the large temperature difference well cementing slurry, has good matching with the high temperature retarder, the high temperature fluid loss reducer and other additives, the cement slurry has excellent high temperature thickening performance, and the thickening time can be adjusted. In addition, the large temperature difference well cementing slurry does not have abnormal gelation, which is specifically manifested as that the high temperature thickening curve does not appear "bulge" and "step" and other phenomena.

[0030] (3) The preparation method of the early strength agent for large-temperature-difference cementing slurry is simple, raw materials are widely sourced, and when used in combination with high-temperature fluid loss additives, large-temperature-difference retarders and other additives, a large-temperature-difference cementing slurry system with good comprehensive working performance, such as good rheological performance, no free fluid, low fluid loss, good high-temperature sedimentation stability, high early strength and the like, can be prepared, the cementing quality of a long cementing section is ensured, and efficient and safe exploitation of deep oil and gas resources is promoted. BRIEF DESCRIPTION OF DRAWINGS

[0031] Figure 1 is a high-temperature thickening curve of a large-temperature-difference cementing slurry mixed with the early strength agent of the present application

[0032] Figure 2 is a high-temperature thickening curve of a large-temperature-difference cementing slurry mixed with the early strength agent of the prior art

[0033] Figure 3 is a high-temperature thickening curve of a large-temperature-difference cementing slurry without mixing any early strength agent. DETAILED DESCRIPTION

[0034] In order to make the objectives, technical solutions and advantages of the present application clearer and more comprehensible, the present application is further described in detail below in combination with embodiments and drawings. Obviously, the described embodiments are only some of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without making any creative effort fall within the scope of protection of the present application. The terms "first", "second", "third", "fourth" and the like in the present application are used to distinguish different objects, rather than to describe a specific order.

[0035] In the embodiments of the present application, the SiO2 content in the nano-quartz powder is ≥99.9wt%.

[0036] In the embodiments of the present application, the particle size range of the nano-quartz powder is between 300-400nm.

[0037] In the embodiments of the present application, the SiO2 content in the nano-calcined kaolin is ≥54wt%, the Al2O3 content is ≥32wt%, and the Fe2O3 content is <3wt%.

[0038] In the embodiments of the present application, the particle size range of the nano-calcined kaolin is between 200-300nm.

[0039] In the embodiments of the present application, the dispersant is a polycarboxylic acid series superplasticizer, and the chemical composition is modified polycarboxylic acid salt; the active ingredient in the modified polycarboxylic acid salt is ≥90%, and the molecular weight is between 10000-30000.

[0040] In the embodiment of the present application, the silane coupling agent is one or more of KH550, KH560, KH570 and KH172.

[0041] In the embodiment of the present application, the effective component in the silane coupling agent is ≥98%.

[0042] Example 1

[0043] As a preferred embodiment of the present application, the specific composition of the early strength agent for large temperature difference well cementing slurry disclosed in the embodiment is shown in Table 1.

[0044] Table 1 Component table of early strength agent in Example 1

[0045] Component name Parts by weight Nanometric quartz powder 40 Nanometric calcinated kaolin 45 Dispersing agent 10 Silane coupling agent 5

[0046] The preparation method of the early strength agent for large temperature difference well cementing slurry disclosed in the embodiment is as follows:

[0047] Step 1, 600 parts of anhydrous ethanol and 200 parts of deionized water are weighed according to the mass fraction and fully mixed to obtain a first mixed solution; 5 parts of a silane coupling agent is weighed and added to the first mixed solution, and after ultrasonic dispersion for 1 h, a second mixed solution is obtained; the pH value of the second mixed solution is adjusted to 4-5 by using anhydrous oxalic acid to obtain a third mixed solution, the third mixed solution is a modified solution of nano quartz powder and nano calcined kaolin, and the third mixed solution is transferred to a reaction kettle with heating, stirring and condensation reflux device;

[0048] Step 2, 40 parts of nano quartz powder, 45 parts of nano calcined kaolin and 10 parts of a dispersing agent are weighed according to the mass fraction and fully and uniformly mixed to obtain a mixture; and the mixture is slowly added to the third mixed solution to obtain a fourth mixed solution; the reflux device in the reaction kettle is opened, the temperature is raised to 60°C, and the stirring speed is controlled at 400-500 r / min, so that the fourth mixed solution is reacted for 3 h, the reaction liquid is removed, and a fifth mixed solution is obtained;

[0049] Step 3, the fifth mixed solution is vacuum filtered, and the filtered product is washed with anhydrous ethanol, and then the filtered product is vacuum dried, the drying temperature of the vacuum drying is 50°C, and the drying time is 6 h, to obtain the early strength agent for large temperature difference well cementing slurry.

[0050] Example 2

[0051] As a preferred embodiment of the present application, the specific composition of the early strength agent for large temperature difference well cementing slurry disclosed in the embodiment is shown in Table 2.

[0052] Table 2 Component table of early strength agent in Example 2

[0053]

[0054]

[0055] The preparation method of the early strength agent for large temperature difference well cementing slurry disclosed in the embodiment is as follows:

[0056] Step 1, 600 parts of anhydrous ethanol and 200 parts of deionized water are weighed and mixed fully to obtain a first mixed solution; 4 parts of a silane coupling agent is added into the first mixed solution, and after ultrasonic dispersion for 1 h, a second mixed solution is obtained; the pH value of the second mixed solution is adjusted to 4-5 by using anhydrous oxalic acid to obtain a third mixed solution, the third mixed solution is a modified solution of nano quartz powder and nano calcined kaolin, and the third mixed solution is transferred to a reaction kettle with heating, stirring and condensation reflux devices;

[0057] Step 2, 50 parts of nano quartz powder, 39 parts of nano calcined kaolin and 7 parts of a dispersing agent are weighed and mixed fully and uniformly to obtain a mixture; and the mixture is slowly added into the third mixed solution to obtain a fourth mixed solution; the reflux device in the reaction kettle is opened, the temperature is raised to 60℃, and the stirring speed is controlled to be 400-500 r / min, so that the fourth mixed solution is reacted for 3 h, the reaction liquid is removed, and a fifth mixed solution is obtained;

[0058] Step 3, the fifth mixed solution is vacuum filtered, the filtered product is washed with anhydrous ethanol, and then the filtered product is vacuum dried, the drying temperature of the vacuum drying is 50℃, and the drying time is 6 h, so that the early strength agent for large temperature difference well cementing slurry is obtained.

[0059] Example 3

[0060] As a more preferred embodiment of the application, the early strength agent for large temperature difference well cementing slurry disclosed in the embodiment has the specific composition shown in Table 3.

[0061] Table 3 Component table of the early strength agent in Example 3

[0062] Component name Parts by weight Nanometric quartz powder 55 Nanometric calcinated kaolin 35 Dispersing agent 6 Silane coupling agent 4

[0063] The preparation method of the early strength agent for large temperature difference well cementing slurry disclosed in the embodiment is as follows:

[0064] Step 1, 600 parts of anhydrous ethanol and 200 parts of deionized water are weighed and mixed fully to obtain a first mixed solution; 4 parts of a silane coupling agent is added into the first mixed solution, and after ultrasonic dispersion for 1 h, a second mixed solution is obtained; the pH value of the second mixed solution is adjusted to 4-5 by using anhydrous oxalic acid to obtain a third mixed solution, the third mixed solution is a modified solution of nano quartz powder and nano calcined kaolin, and the third mixed solution is transferred to a reaction kettle with heating, stirring and condensation reflux devices;

[0065] Step 2, 55 parts of nano-quartz powder, 35 parts of nano-calcined kaolin and 6 parts of dispersant are weighed according to the mass fraction and uniformly mixed to obtain a mixture; and the mixture is slowly added into the third mixed solution to obtain a fourth mixed solution; the reflux device in the reaction kettle is opened, the temperature is raised to 60℃, the stirring speed is controlled to be 400-500 r / min, and the fourth mixed solution is reacted for 3h, the reaction liquid is removed, and a fifth mixed solution is obtained;

[0066] Step 3, the fifth mixed solution is vacuum filtered, the filtered product is washed with anhydrous ethanol, and then the filtered product is vacuum dried, the drying temperature of vacuum drying is 50℃, and the drying time is 6h, to obtain the early strength agent for large temperature difference cementing slurry.

[0067] Example 4

[0068] As a preferred embodiment of the present application, the specific composition of the early strength agent for large temperature difference cementing slurry disclosed in this embodiment is shown in Table 4.

[0069] Table 4: Early strength agent component table of Example 4

[0070] Component name Parts by weight Nanometric quartz powder 60 Nanometric calcinated kaolin 32 Dispersing agent 5 Silane coupling agent 3

[0071] The preparation method of the early strength agent for large temperature difference cementing slurry disclosed in this embodiment is:

[0072] Step 1, 600 parts of anhydrous ethanol and 200 parts of deionized water are weighed according to the mass fraction and mixed to obtain a first mixed solution; 3 parts of a silane coupling agent is added into the first mixed solution, and after ultrasonic dispersion for 1h, a second mixed solution is obtained; the pH value of the second mixed solution is adjusted to 4-5 by using anhydrous oxalic acid to obtain a third mixed solution, the third mixed solution is a modified solution of nano-quartz powder and nano-calcined kaolin, and the third mixed solution is transferred to a reaction kettle with heating, stirring and condensation reflux device;

[0073] Step 2, 60 parts of nano-quartz powder, 32 parts of nano-calcined kaolin and 5 parts of dispersant are uniformly mixed according to the mass fraction to obtain a mixture; and the mixture is slowly added into the third mixed solution to obtain a fourth mixed solution; the reflux device in the reaction kettle is opened, the temperature is raised to 60℃, the stirring speed is controlled to be 400-500 r / min, and the fourth mixed solution is reacted for 3h, the reaction liquid is removed, and a fifth mixed solution is obtained;

[0074] Step 3, the fifth mixed solution is vacuum filtered, the filtered product is washed with anhydrous ethanol, and then the filtered product is vacuum dried, the drying temperature of vacuum drying is 50℃, and the drying time is 6h, to obtain the early strength agent for large temperature difference cementing slurry.

[0075] Comparative Example 1

[0076] The early strength agent of the present comparative example is a commercially available early strength agent, which is mainly a composite of nanomaterials and inorganic salt materials.

[0077] Comparative Example 2

[0078] The present comparative example is a blank group without adding any early strength agent.

[0079] Test Example

[0080] The early strength agents of Examples 1-4 are respectively added to the cement paste (density of 1.89 g / cm 3 ) under the same conditions to obtain the experimental groups corresponding to each example, and experiments are carried out according to the following formulation: Jiahua G-grade oil well cement (based on 100.0 wt% of G-grade oil well cement) + 30.0 wt% of quartz sand-partial kaolin high-temperature strength stabilizer + 0.3-0.7 wt% of early strength agent + 0.30 wt% of aldehyde ketone polycondensate dispersant + 0.5 wt% of AMPS copolymer high-temperature retarder (liquid) + 5 wt% of AMPS-AM high-temperature fluid loss additive (liquid) + 0.2% of dimethyl silicone oil defoaming agent + 70 wt% of tap water.

[0081] Comparative Example 1 and Comparative Example 2 (blank group) are also set up, Comparative Example 1 uses a commercially available ordinary early strength agent to replace the early strength agent for large-temperature-difference well cementing cement slurry of the present application, and Comparative Example 2 (blank group) does not add any early strength agent, and the rest of the formulation and conditions are the same as above.

[0082] The large-temperature-difference well cementing cement slurry is prepared according to GB / T19139-2012 Oil Well Cement Test Methods, and the engineering performance of the large-temperature-difference well cementing cement slurry in Comparative Example 1, Comparative Example 2 (blank group) and each example is tested according to SY / T6544-2017 Oil Well Cement Slurry Performance Requirements, wherein the test method for the top 50℃ strength of the cement slurry is as follows: the large-temperature-difference well cementing cement slurry is heated to 150℃ and kept for 30 min, then stopped and naturally cooled to 50℃, then the thickening experimental slurry cup is taken out, the upper thickening oil is completely removed, the cement slurry is poured into a mold and placed in a 50℃ water bath for curing, and the curing age is 12 h and 24 h, and the experimental results are shown in Table 5.

[0083] Table 1 Experimental results of examples and comparative examples

[0084]

[0085] From the results of Table 1 and Figure 3 , it can be seen that without adding an early strength agent (Comparative Example 2), under the action of a high-temperature retarder, the high-temperature thickening time of the large-temperature-difference well cementing cement slurry is 322 min, the strength development in the top low-temperature region at 50℃ is very slow, and the phenomenon of retardation or super retardation occurs, which seriously affects the subsequent construction progress and is difficult to guarantee the well cementing quality of the large-temperature-difference sealing section.

[0086] From Table 1 and Figure 2 It can be seen that, after adding the early strength agent of the prior art (Comparative Example 1), the strength of the large-temperature-difference cementing slurry at the top low-temperature region segment of 50℃ increases, but the 24h compressive strength is only 5.7MPa, which is still difficult to meet the strength requirement of subsequent construction. In addition, after adding the early strength agent of the prior art, the high-temperature thickening time of the large-temperature-difference cementing slurry is significantly shortened, and abnormal gelation occurs, which shows that the high-temperature curve fluctuates sharply, and the consistency is inverted, which indicates that the early strength agent of the prior art has poor quartz property in the large-temperature-difference cementing slurry, and it is difficult to effectively guarantee the cementing quality of the long cementing segment.

[0087] From Table 1 and Figure 1 It can be seen that, after adding the early strength agent of the prior art (Comparative Example 1), the strength of the large-temperature-difference cementing slurry at the top low-temperature region segment of 50℃ increases, but the 24h compressive strength is only 5.7MPa, which is still difficult to meet the strength requirement of subsequent construction. In addition, after adding the early strength agent of the prior art, the high-temperature thickening time of the large-temperature-difference cementing slurry is significantly shortened, and abnormal gelation occurs, which shows that the high-temperature curve fluctuates sharply, and the consistency is inverted, which indicates that the early strength agent of the prior art has poor quartz property in the large-temperature-difference cementing slurry, and it is difficult to effectively guarantee the cementing quality of the long cementing segment.

[0088] Finally, it should be noted that: the above embodiments are only the preferred embodiments of the present application for describing the technical solutions of the present application, but not limiting them, and of course, they are not limiting the patent scope of the present application; although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that: it can still modify the technical solutions recorded in the foregoing embodiments, or make equivalent replacement to part or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application; that is to say, any modification or polishing without substantial significance in the main design idea and spirit of the present application, and the technical problems solved are still consistent with the present application, which should be included in the protection scope of the present application; in addition, the technical solutions of the present application are directly or indirectly applied to other related technical fields, which are also included in the patent protection scope of the present application.

Claims

1. An early strength agent for large temperature difference cementing slurry, characterized in that: It comprises the following components in parts by weight: 40-60 parts of nano-quartz powder; 32-45 parts of nano calcined kaolin; 5-10 parts of dispersant; 3~5 parts of silane coupling agent; The method for preparing an early strength agent for large temperature difference cementing slurry comprises the following steps: Step 1, weighing 400-800 parts by mass of anhydrous ethanol and 100-300 parts by mass of deionized water and mixing them thoroughly to obtain a first mixed solution; weighing 3-5 parts of a silane coupling agent, adding the mixture to the first mixed solution, and ultrasonically dispersing the mixture for 1 hour to obtain a second mixed solution; adjusting the pH value of the second mixed solution to 4-5 with anhydrous oxalic acid to obtain a third mixed solution, wherein the third mixed solution is a modified solution of nano-quartz powder and nano-calcined kaolin, and transferring the third mixed solution to a reactor equipped with a heating, stirring, and condensation reflux device; Step 2: Weigh 40-60 parts by mass of nano-quartz powder, 32-45 parts of nano-calcined kaolin, and 5-10 parts of a dispersant and mix them thoroughly and evenly to obtain a mixture; and slowly add the mixture to the third mixed solution to obtain a fourth mixed solution; open the reflux device in the reactor, raise the temperature to 60° C., control the stirring speed to 400-500 r / min, react the fourth mixed solution for 3 hours, remove the reaction solution, and obtain a fifth mixed solution; Step 3: vacuum-filter the fifth mixed liquid, wash the filtered product with anhydrous ethanol, and then vacuum-dry the filtered product to obtain an early strength agent for large temperature difference cementing slurry.

2. The early strength agent for large temperature difference cementing slurry according to claim 1, characterized in that: The SiO2 content in the nano-quartz powder is ≥99.9wt%.

3. The early strength agent for large temperature difference cementing slurry according to claim 1, characterized in that: The particle size of the nano-quartz powder ranges from 300 to 400 nm.

4. The early strength agent for large temperature difference cementing slurry according to claim 1, characterized in that: The nano-calcined kaolin has a SiO2 content of ≥54wt%, an Al2O3 content of ≥32wt%, and a Fe2O3 content of <3wt%.

5. The early strength agent for large temperature difference cementing slurry according to claim 1, characterized in that: The particle size of the nano-calcined kaolin is in the range of 200-300 nm.

6. The early strength agent for large temperature difference cementing slurry according to claim 1, characterized in that: The dispersant is a polycarboxylic acid series high-efficiency water reducer, and its chemical composition is modified polycarboxylate; the active ingredient in the modified polycarboxylate is ≥90%, and the molecular weight is between 10,000 and 30,000.

7. The early strength agent for large temperature difference cementing slurry according to claim 1, characterized in that: The silane coupling agent is one or more of KH550, KH560, KH570 and KH172.

8. The early strength agent for large temperature difference cementing slurry according to claim 1, characterized in that: The effective ingredient in the silane coupling agent is ≥98%.

9. The early strength agent for large temperature difference cementing slurry according to claim 1, characterized in that: In the step 1, the amount of anhydrous ethanol is 600 parts and the amount of deionized water is 200 parts.

10. The early strength agent for large temperature difference cementing slurry according to claim 1, characterized in that: In step 3, the vacuum drying temperature is 50° C. and the drying time is 6 h.

Images