High-temperature early-strength low-density cement slurry with large temperature difference and preparation method thereof

Abstract

The application discloses a high-temperature large-temperature-difference early-strength low-density cementing slurry and a preparation method thereof, and relates to the technical field of oil and gas well cementing. The cementing slurry comprises the following components in parts by mass: 100 parts of oil well cement, 15-35 parts of a high-temperature strength stabilizer, 10-30 parts of a lightening agent, 0.2-0.6 parts of an early-strength agent, 0.3-0.7 parts of a high-temperature suspending stabilizer, 1-5 parts of a high-temperature fluid loss additive, 0.3-0.7 parts of a high-temperature retarding agent and 50-70 parts of water. The application solves the problems of poor rheological property, excessive fluid loss, poor high-temperature stability and slow strength development of the large-temperature-difference low-density cementing slurry in the prior art, realizes safe cementing construction of long cementing section easy-to-leak formations, and thus guarantees efficient and safe exploitation of oil and gas resources in deep formations.

Description

Technical Field

[0001] This invention relates to the technical field of oil and gas well cementing, specifically to a high-temperature, large-temperature-difference, early-strength, low-density cement slurry and its preparation method. Background Technology

[0002] With the steady growth of my country's economy, the demand for oil and gas resources has been continuously rising. Shallow and easily exploitable oil and gas resources are gradually being depleted, causing the focus of oilfield exploration and development to gradually shift to deep formations. Deep formations contain abundant oil and gas resources. my country's deep oil resources exceed 20 billion tons, and deep natural gas resources exceed 100 trillion cubic meters, providing ample space for the sustainable development of my country's petroleum industry.

[0003] The geological conditions of deep oil and gas reservoirs are complex, with most burial depths exceeding 5000m. The number of wells undergoing cementing in long sealing sections is increasing, and this process primarily employs one-time cementing technology. Currently, the bottom-hole temperature in easily leaky formations within long sealing sections generally exceeds 150℃, placing stringent requirements on the high-temperature resistance of the cement slurry. Furthermore, to prevent formation leakage and improve cementing efficiency and quality, low-density cement slurry is typically used for cementing long sealing sections. Low-density cement slurry has a low solid content and poor stability under high temperature conditions, making it prone to problems such as cement slurry stratification and high-temperature sedimentation. At the same time, due to the long cementing section of the well cement slurry being returned to the well at one time, the temperature difference between the top and bottom of the cement slurry column is large, with the bottom temperature exceeding 150°C and the top temperature around 60°C, a temperature difference of up to 90°C. Under the action of high-temperature retarder, the strength development of the top cement slurry is slow, and even slow or super-slow setting phenomena occur, which seriously affect the subsequent construction progress and cannot guarantee the cementing quality of the long cementing section. Therefore, the high temperature and large temperature difference performance of low-density cement slurry poses a severe challenge.

[0004] As well depth increases, the length of the long cementing section also increases, and the temperature difference between the bottom and top of the well also increases. However, existing high-temperature, high-temperature-difference, low-density cementing slurry is difficult to use. The existing high-temperature, high-temperature-difference, low-density cementing slurry has the following problems: (1) Poor high-temperature thickening performance: The solid phase composition of low-density cementing slurry is complex and low in content, with a high water-cement ratio and a variety of high-temperature admixtures, which makes it difficult to adjust the thickening time of low-density cementing slurry and easily leads to abnormal high-temperature gelation. Specifically, the high-temperature thickening curve of the cementing slurry shows phenomena such as "bulging" and "stepping", which leads to poor cementing quality; (2) High-temperature strength decay and slow strength development of cementing slurry in the top low-temperature zone: High-density cement slurry is prone to high-temperature strength decay in high-temperature environments above 110℃. In addition, due to the high water-cement ratio of existing low-density cement slurry and the lack of solid materials, the strength development of low-density cement slurry in the low-temperature zone at the top of the well is slow under the action of high-temperature retarder, and even the phenomenon of slow setting and super slow setting occurs; (3) poor high-temperature stability: low-density cement slurry has a high water-cement ratio and less solid materials. Under the action of high temperature, the lightening agent in the cement slurry floats up and the remaining solid materials sink down, which does not lead to a decrease in high-temperature settling stability. Summary of the Invention

[0005] In order to overcome the defects and deficiencies in the existing technology, the present invention aims to provide a high-temperature, large-temperature-difference, early-strength, low-density cement slurry and its preparation method, so as to solve the problems of poor rheological properties, excessive water loss, poor high-temperature stability, and slow strength development of the existing large-temperature-difference, low-density cement slurry, and realize safe cementing construction in easily leaking formations in long cementing sections, thereby ensuring the efficient and safe exploitation of oil and gas resources in deep formations.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0007] This invention provides a high-temperature, high-temperature-difference, early-strength, low-density cement slurry, comprising the following components by weight:

[0008]

[0009] In some embodiments of the present invention, the oil well cement is a mixture of Grade G cement and Grade D cement, and the main mineral composition of the oil well cement is as follows: C3S: 60-68 wt%, C2S: 20-25 wt%, C3A: 0-1 wt%, C4AF: 12-14 wt%; the physical properties of the oil well cement meet the following requirements: specific surface area ≥ 400 m² / g. 2 / kg, SO3 content ≤3wt%.

[0010] In some embodiments of the present invention, the high-temperature strength stabilizer is composed of a mixture of quartz sand, kyanite powder, maifanite, and metakaolin; the physical properties of the quartz sand satisfy the following: specific surface area ≥ 500 kg / m². 3 The physical properties of the kyanite powder meet the following requirements: specific surface area ≥ 500 kg / m² 3 The physical properties of the maifanite described meet the following requirements: specific surface area ≥ 500 kg / m² 3 The physical properties of the metakaolin meet the following requirements: specific surface area ≥ 1000 kg / m³ 3 .

[0011] In some embodiments of the present invention, the weight-reducing agent is one or a mixture of poplar wood powder, rubber powder, and plastic powder; the physical properties of the poplar wood powder satisfy the following: density ≤ 0.40 g / cm³. 3 Specific surface area ≥300kg / m² 3 The physical properties of the rubber powder meet the following requirements: density ≤ 1.3 g / cm³. 3 Specific surface area ≥ 500 kg / m² 3 The physical properties of the plastic powder meet the following requirements: density ≤ 1.5 g / cm³. 3 Specific surface area ≥ 500 kg / m² 3 .

[0012] In some embodiments of the present invention, the early strength agent is a nucleation-type early strength agent, including one or more of nano-hydrated calcium silicate particles, nano-calcium silicate, nano-silica, and nano-calcium carbonate, wherein the particle size range of nano-hydrated calcium silicate particles, nano-calcium silicate, nano-silica, and nano-calcium carbonate is between 50 and 100 nm.

[0013] In some embodiments of the present invention, the high-temperature suspension stabilizer is a mixture of polyvinyl alcohol 1788, lithium saponite powder, and dolomite powder; the physical properties of the polyvinyl alcohol 1788 meet the following requirements: purity ≥ 93.5%, specific surface area ≥ 200 kg / m². 3 The physical properties of the lithium saponite powder meet the following requirements: specific surface area ≥ 350 kg / m² 3 The physical properties of the dolomite powder meet the following requirements: specific surface area ≥ 1000 kg / m² 3 .

[0014] In some embodiments of the present invention, the high-temperature water loss reducing agent is a G33S water loss reducing agent, which is obtained by polymerization modification of AMPS, low molecular weight amides, polyhydroxycarboxylic acids, etc.

[0015] In some embodiments of the present invention, the high-temperature retarder is a random copolymer with a molecular weight between 20,000 and 40,000. It is prepared by free radical aqueous solution polymerization using 30-45 parts by weight of acrylamide, 30-40 parts by weight of maleic anhydride, 10-20 parts by weight of 3-allyloxy-2-hydroxy-1-propanesulfonate and 5-10 parts by weight of dimethyldiallyl ammonium chloride as monomers and 2-4 parts by weight of sodium bisulfite-ammonium persulfate as a composite initiator.

[0016] In some embodiments of the present invention, the preparation method of the high-temperature retarder is as follows:

[0017] S1. At room temperature, take 30-45 parts by weight of acrylamide, 30-40 parts by weight of maleic anhydride, 10-20 parts by weight of 3-allyloxy-2-hydroxy-1-propanesulfonate, and 5-10 parts by weight of dimethyldiallylammonium chloride and add them to 100 parts by weight of water. After fully dissolving and mixing, the first mixture is obtained.

[0018] S2. At room temperature, the pH of the first mixture is adjusted to 7-8 using a 20% sodium hydroxide solution to obtain the second mixture.

[0019] S3. At room temperature, add 1-2 parts by weight of sodium bisulfite to 23-24 parts by weight of water, and after fully dissolving and mixing, obtain a third mixture; add 1-2 parts by weight of ammonium persulfate to 23-24 parts by weight of water, and after fully dissolving and mixing, obtain a fourth mixture.

[0020] S4. Transfer the second mixture to a reactor equipped with a stirrer, introduce nitrogen gas to remove oxygen from the reactor and maintain a nitrogen atmosphere, stir and heat the second mixture to 60°C, then add the third mixture dropwise to the second mixture using a constant pressure funnel. After the addition is complete, add the fourth mixture dropwise to the second mixture using the same constant pressure funnel. After the addition is complete, a fifth mixture is obtained. Preferably, the stirring speed during stirring and heating is 200 r / min, and the dropping speed of the third and fourth mixtures is 10 drops / min.

[0021] S5. The fifth mixture is kept at 60°C for 3 hours, then naturally cooled to 45°C and kept at 45°C for 1-2 hours. Then it is taken out to obtain the ninth mixture, which is the high-temperature retarder.

[0022] The present invention also provides a method for preparing high-temperature, large-temperature-difference, early-strength, low-density cement slurry, comprising the following operations: weighing 100 parts by weight of oil well cement, 10-35 parts by weight of high-temperature strength stabilizer, 10-30 parts by weight of weight-reducing agent, 0.2-0.6 parts by weight of early-strength agent, 0.3-0.7 parts by weight of high-temperature suspension stabilizer, 1-5 parts by weight of high-temperature fluid loss reducing agent, 0.3-0.7 parts by weight of high-temperature retarder and 50-70 parts by weight of water, and preparing the high-temperature, large-temperature-difference, early-strength, low-density cement slurry according to GB / T19139—2012 Test Methods for Oil Well Cement.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] 1. Compared with existing technologies, the high-temperature, large-temperature-difference, low-density cement slurry provided by this invention has better rheological properties, no free liquid, low water loss, superior high-temperature settling stability, excellent high-temperature thickening performance, adjustable thickening time, and no abnormal gelling phenomenon during the cement slurry thickening process. Furthermore, the high-temperature strength of the cement stone in the high-temperature zone of this invention does not decline, and the early strength of the cement mud stone in the low-temperature zone is high, effectively ensuring the cementing quality of easily leaking layers in long sealing sections and guaranteeing the efficient and safe exploitation of deep formation oil and gas resources.

[0025] 2. Compared with the prior art, the light-reducing agent used in the high-temperature, large-temperature-difference, low-density cement slurry provided by the present invention is mainly one or more of wood flour, rubber powder, and plastic powder. The above-mentioned light-reducing agents are all inert materials, which play a good role in lightening the cement slurry. They are inexpensive, widely available, and fully realize the utilization of waste, effectively reduce the cost of cementing materials, and achieve the advantages of cost reduction and efficiency improvement.

[0026] 3. Compared with the prior art, the early strength agent used in the high-temperature, large-temperature-difference, low-density cement slurry provided by this invention is a nucleation-type early strength agent. It has no significant promoting effect on the hydration reaction rate in the initial stage of cement hydration reaction, and the induction period of cement slurry remains basically unchanged. It mainly acts in the later stage of hydration acceleration period, promoting the formation of hydrated calcium silicate gel and increasing the growth rate of calcium vanadate. Therefore, this early strength agent has little effect on the high-temperature thickening time of high-temperature, large-temperature, low-density cement slurry, and can effectively promote the strength development of low-density cement slurry in the low-temperature region.

[0027] 4. Compared with the prior art, the retarder used in the high-temperature, large-temperature-difference, low-density cement slurry provided by this invention is an amphoteric retarder, which contains two oppositely charged sulfonic acid groups (-SO3) on its molecular chain. - ) and quaternary ammonium group (R 4 N +This unique structure allows it to effectively adsorb onto the surface of cement particles during hydration, forming a stable double electric layer that prevents further aggregation and hardening of the cement particles, thus delaying the setting time of oil well cement. When the ambient temperature changes, the charge state of the zwitterions adjusts, altering their adsorption capacity for cement particles. At higher temperatures, their adsorption capacity increases, more effectively preventing the hardening of cement slurry with large temperature differences; conversely, at lower temperatures, their adsorption capacity decreases, allowing the cement slurry with large temperature differences to harden normally. This resolves the contradiction between the long high-temperature thickening time and slow low-temperature strength development of cement slurry with large temperature differences, achieving the characteristics of high-temperature slow setting and low-temperature early strength. Attached Figure Description

[0028] Figure 1 The high-temperature thickening curve of the high-temperature, large-temperature-difference, early-strength, low-density cement slurry prepared in Example 1.

[0029] Figure 2 The high-temperature thickening curve of the high-temperature, large-temperature-difference, early-strength, low-density cement slurry prepared in Example 3 is shown.

[0030] Figure 3 The high-temperature thickening curve of the high-temperature, large-temperature-difference, early-strength, low-density cement slurry prepared in Example 5 is shown.

[0031] Figure 4 The high-temperature thickening curve of the high-temperature cement slurry with large temperature difference and low density prepared for Comparative Example 1.

[0032] Figure 5 The high-temperature thickening curve of the high-temperature cement slurry with large temperature difference and low density prepared for Comparative Example 2.

[0033] Figure 6 The high-temperature thickening curve of the high-temperature cement slurry with large temperature difference and low density prepared for Comparative Example 3. Detailed Implementation

[0034] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. Obviously, the described embodiments are merely some embodiments of this invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention. The terms "first," "second," etc., used in this invention are used to distinguish different objects, not to describe a specific order.

[0035] In this embodiment of the invention, the oil well cement is a mixture of Grade G cement and Grade D cement. The main mineral composition of the oil well cement is as follows: C3S: 60-68 wt%, C2S: 20-25 wt%, C3A: 0-1 wt%, C4AF: 12-14 wt%. The physical properties of the oil well cement meet the following requirements: specific surface area ≥ 400 m². 2 / kg, SO3 content ≤3wt%.

[0036] In this embodiment of the invention, the high-temperature strength stabilizer is composed of a mixture of quartz sand, kyanite powder, maifanite, and metakaolin; the physical properties of the quartz sand meet the following requirement: specific surface area ≥ 500 kg / m². 3 The physical properties of the kyanite powder meet the following requirements: specific surface area ≥ 500 kg / m² 3 The physical properties of the maifanite described meet the following requirements: specific surface area ≥ 500 kg / m² 3 The physical properties of the metakaolin meet the following requirements: specific surface area ≥ 1000 kg / m³ 3 .

[0037] In this embodiment of the invention, the weight-reducing agent is one or a mixture of poplar wood powder, rubber powder, and plastic powder; the physical properties of the poplar wood powder satisfy the following: density ≤ 0.40 g / cm³. 3 Specific surface area ≥300kg / m² 3 The physical properties of the rubber powder meet the following requirements: density ≤ 1.3 g / cm³. 3 Specific surface area ≥ 500 kg / m² 3 The physical properties of the plastic powder meet the following requirements: density ≤ 1.5 g / cm³. 3 Specific surface area ≥ 500 kg / m² 3 .

[0038] In this embodiment of the invention, the early strength agent is a nucleation-type early strength agent, including one or more of nano-hydrated calcium silicate particles, nano-calcium silicate, nano-silica, and nano-calcium carbonate, wherein the particle size range of nano-hydrated calcium silicate particles, nano-calcium silicate, nano-silica, and nano-calcium carbonate is between 50 and 100 nm.

[0039] In this embodiment of the invention, the high-temperature suspension stabilizer is a mixture of polyvinyl alcohol 1788, lithium saponite powder, and dolomite powder; the physical properties of the polyvinyl alcohol 1788 meet the following requirements: purity ≥ 93.5%, specific surface area ≥ 200 kg / m². 3 The physical properties of the lithium saponite powder meet the following requirements: specific surface area ≥ 350 kg / m² 3 The physical properties of the dolomite powder meet the following requirements: specific surface area ≥ 1000 kg / m² 3 .

[0040] In this embodiment of the invention, the high-temperature water loss reducing agent is G33S water loss reducing agent.

[0041] In this embodiment of the invention, the high-temperature retarder is a random copolymer with a molecular weight between 20,000 and 40,000. It is prepared by free radical aqueous solution polymerization using 30-45 parts by weight of acrylamide, 30-40 parts by weight of maleic anhydride, 10-20 parts by weight of 3-allyloxy-2-hydroxy-1-propanesulfonate and 5-10 parts by weight of dimethyldiallyl ammonium chloride as monomers and 2-4 parts by weight of sodium bisulfite-ammonium persulfate as a composite initiator.

[0042] In this embodiment of the invention, the preparation method of the high-temperature retarder is as follows:

[0043] S1. At room temperature, take 30-45 parts by weight of acrylamide, 30-40 parts by weight of maleic anhydride, 10-20 parts by weight of 3-allyloxy-2-hydroxy-1-propanesulfonate, and 5-10 parts by weight of dimethyldiallylammonium chloride and add them to 100 parts by weight of water. After fully dissolving and mixing, the first mixture is obtained.

[0044] S2. At room temperature, the pH of the first mixture is adjusted to 7-8 using a 20% sodium hydroxide solution to obtain the second mixture.

[0045] S3. At room temperature, add 1-2 parts by weight of sodium bisulfite to 23-24 parts by weight of water, and after fully dissolving and mixing, obtain a third mixture; add 1-2 parts by weight of ammonium persulfate to 23-24 parts by weight of water, and after fully dissolving and mixing, obtain a fourth mixture.

[0046] S4. Transfer the second mixture to a reactor equipped with a stirrer, introduce nitrogen gas to remove oxygen from the reactor and maintain a nitrogen atmosphere, stir and heat the second mixture to 60°C at 200 r / min, and then add the third mixture to the second mixture at 10 drops / min using a constant pressure funnel. After the addition is complete, add the fourth mixture to the second mixture at 10 drops / min using the same constant pressure funnel. After the addition is complete, the fifth mixture is obtained.

[0047] S5. The fifth mixture is kept at 60°C for 3 hours, then naturally cooled to 45°C and kept at 45°C for 1-2 hours. Then it is taken out to obtain the ninth mixture, which is the high-temperature retarder.

[0048] Example 1

[0049] As a preferred embodiment of the present invention, the high-temperature, large-temperature-difference, early-strength, low-density cement slurry disclosed in this embodiment has the specific composition shown in Table 1.

[0050] Table 1. Composition of Cement Slurry in Example 1

[0051]

[0052]

[0053] According to Table 1, weigh 100 parts of oil well cement, 35 parts of high-temperature strength stabilizer, 10 parts of weight-reducing agent, 0.2 parts of early-strength agent, 0.3 parts of high-temperature suspension stabilizer, 1 part of high-temperature fluid loss reducing agent, 0.7 parts of high-temperature retarder and 50 parts of water, and prepare high-temperature large temperature difference early-strength low-density cement slurry No. 1 according to "GB / T19139—2012 Oil Well Cement Test Method".

[0054] Example 2

[0055] As a preferred embodiment of the present invention, the high-temperature, large-temperature-difference, early-strength, low-density cement slurry disclosed in this embodiment has the specific composition shown in Table 2.

[0056] Table 2. Composition of Cement Slurry in Example 2

[0057] Component Name weight parts / portion Oil well cement 100 High temperature strength stabilizer 30 Relief agent 15 Early strength agent 0.3 High temperature suspension stabilizer 0.4 High-temperature dehydration agent 2 High temperature retarder 0.6 water 55

[0058] According to Table 2, weigh 100 parts of oil well cement, 30 parts of high-temperature strength stabilizer, 15 parts of weight-reducing agent, 0.3 parts of early-strength agent, 0.4 parts of high-temperature suspension stabilizer, 2 parts of high-temperature fluid loss reducing agent, 0.6 parts of high-temperature retarder and 55 parts of water, and prepare high-temperature large temperature difference early-strength low-density cement slurry No. 2 according to "GB / T19139—2012 Oil Well Cement Test Method".

[0059] Example 3

[0060] As a preferred embodiment of the present invention, the high-temperature, large-temperature-difference, early-strength, low-density cement slurry disclosed in this embodiment has the specific composition shown in Table 3.

[0061] Table 3. Composition of Cement Slurry in Example 3

[0062] Component Name weight parts / portion Oil well cement 100 High temperature strength stabilizer 25 Relief agent 20 Early strength agent 0.4 High temperature suspension stabilizer 0.5 High-temperature dehydration agent 3 High temperature retarder 0.5 water 60

[0063] According to Table 3, weigh 100 parts of oil well cement, 25 parts of high-temperature strength stabilizer, 20 parts of weight-reducing agent, 0.4 parts of early-strength agent, 0.5 parts of high-temperature suspension stabilizer, 3 parts of high-temperature fluid loss reducing agent, 0.5 parts of high-temperature retarder and 60 parts of water, and prepare high-temperature large temperature difference early-strength low-density cement slurry No. 3 according to "GB / T19139—2012 Oil Well Cement Test Method".

[0064] Example 4

[0065] As a preferred embodiment of the present invention, the high-temperature, large-temperature-difference, early-strength, low-density cement slurry disclosed in this embodiment has the specific composition shown in Table 4.

[0066] Table 4. Composition of Cement Slurry in Example 4

[0067] Component Name weight parts / portion Oil well cement 100 High temperature strength stabilizer 20 Relief agent 25 Early strength agent 0.5 High-temperature suspension stabilizer 0.6 High-temperature dehydration agent 4 High temperature retarder 0.4 water 65

[0068] According to Table 4, weigh 100 parts of oil well cement, 20 parts of high-temperature strength stabilizer, 25 parts of weight-reducing agent, 0.5 parts of early-strength agent, 0.6 parts of high-temperature suspension stabilizer, 4 parts of high-temperature fluid loss reducing agent, 0.4 parts of high-temperature retarder and 65 parts of water, and prepare high-temperature large temperature difference early-strength low-density cement slurry No. 4 according to "GB / T19139—2012 Oil Well Cement Test Method".

[0069] Example 5

[0070] As a preferred embodiment of the present invention, the high-temperature, large-temperature-difference, early-strength, low-density cement slurry disclosed in this embodiment has the specific composition shown in Table 5.

[0071] Table 5. Composition of Cement Slurry in Example 5

[0072] Component Name weight parts / portion Oil well cement 100 High temperature strength stabilizer 15 Relief agent 30 Early strength agent 0.6 High-temperature suspension stabilizer 0.7 High-temperature dehydration agent 5 High temperature retarder 0.3 water 70

[0073] According to Table 5, weigh 100 parts of oil well cement, 15 parts of high-temperature strength stabilizer, 30 parts of weight-reducing agent, 0.6 parts of early-strength agent, 0.7 parts of high-temperature suspension stabilizer, 5 parts of high-temperature fluid loss reducing agent, 0.3 parts of high-temperature retarder and 70 parts of water, and prepare high-temperature large temperature difference early-strength low-density cement slurry No. 5 according to "GB / T19139—2012 Oil Well Cement Test Method".

[0074] Comparative Example 1

[0075] The specific composition of the high-temperature, large-temperature-difference, low-density cement slurry used in this comparative example is shown in Table 6.

[0076] Table 6. Composition of Cement Slurry in Comparative Example 1

[0077]

[0078]

[0079] In this comparative example, the oil well cement is Grade G oil well cement, whose chemical requirements and physical properties meet the API specifications and the national standard GB / T 10238—2015 Oil Well Cement.

[0080] In this comparative example, the high-temperature strength stabilizer is quartz sand, whose chemical composition meets the following requirements: SiO2 ≥ 98wt%, and whose physical properties meet the following requirements: specific surface area ≥ 250kg / m². 2 .

[0081] In this comparative example, the weight-reducing agent is hollow microspheres for oil well cement, whose physical properties meet the following requirements: purity ≥ 97%, density 0.3 g / cm³.3 The particle size is between 10-120μm, the mesh size is 300 mesh, and the floatability is >90%.

[0082] In this comparative example, the early strength agent is a common early strength agent for oil well cement on the market. The main components of this type of early strength agent are nanomaterials, inorganic salts and other materials.

[0083] In this comparative example, the high-temperature suspension stabilizer is a common oil well cement suspension stabilizer on the market. The main components of this type of high-temperature suspension stabilizer are polymer and clay.

[0084] In this comparative example, the high-temperature fluid loss reducing agent is a common high-temperature fluid loss reducing agent for oil well cement on the market. This type of fluid loss reducing agent is polymerized and modified from AMPS (2-acrylamide-2-methylpropanesulfonic acid), acrylamide, polyhydroxycarboxylic acid, etc.

[0085] In this comparative example, the high-temperature retarder is a common high-temperature retarder for oil well cement on the market. This type of retarder is polymerized from AMPS, acrylic acid, high-temperature resistant unsaturated monomers, etc.

[0086] According to Table 6, weigh 100 parts of oil well cement, 35 parts of high-temperature strength stabilizer, 10 parts of weight-reducing agent, 0.2 parts of early-strength agent, 0.3 parts of high-temperature suspension stabilizer, 1 part of high-temperature fluid loss reducing agent, 0.7 parts of high-temperature retarder and 50 parts of water, and prepare high-temperature, large-temperature-difference, low-density cement slurry No. 1 according to "GB / T19139—2012 Oil Well Cement Test Method".

[0087] Comparative Example 2

[0088] The specific composition of the high-temperature, large-temperature-difference, low-density cement slurry used in this comparative example is shown in Table 7.

[0089] Table 7. Composition of Cement Slurry in Comparative Example 2

[0090]

[0091]

[0092] In this comparative example, the oil well cement is Grade G oil well cement, whose chemical requirements and physical properties meet the API specifications and the national standard GB / T 10238—2015 Oil Well Cement.

[0093] In this comparative example, the high-temperature strength stabilizer is quartz sand, whose chemical composition meets the following requirements: SiO2 ≥ 98wt%, and whose physical properties meet the following requirements: specific surface area ≥ 250kg / m². 2 .

[0094] In this comparative example, the weight-reducing agent is hollow microspheres for oil well cement, whose physical properties meet the following requirements: purity ≥ 97%, density 0.3 g / cm³.3 The particle size is between 10-120μm, the mesh size is 300 mesh, and the floatability is >90%.

[0095] In this comparative example, the early strength agent is a common early strength agent for oil well cement on the market. The main components of this type of early strength agent are nanomaterials, inorganic salts and other materials.

[0096] In this comparative example, the high-temperature suspension stabilizer is a common oil well cement suspension stabilizer on the market. The main components of this type of high-temperature suspension stabilizer are polymer and clay.

[0097] In this comparative example, the high-temperature fluid loss reducing agent is a common high-temperature fluid loss reducing agent for oil well cement on the market. This type of fluid loss reducing agent is polymerized and modified from AMPS (2-acrylamide-2-methylpropanesulfonic acid), acrylamide, polyhydroxycarboxylic acid, etc.

[0098] In this comparative example, the high-temperature retarder is a common high-temperature retarder for oil well cement on the market. This type of retarder is polymerized from AMPS, acrylic acid, high-temperature resistant unsaturated monomers, etc.

[0099] According to Table 7, weigh 100 parts of oil well cement, 25 parts of high-temperature strength stabilizer, 20 parts of weight-reducing agent, 0.4 parts of early-strength agent, 0.5 parts of high-temperature suspension stabilizer, 3 parts of high-temperature fluid loss reducer, 0.5 parts of high-temperature retarder and 60 parts of water, and prepare high-temperature, large-temperature-difference, low-density cement slurry No. 2 according to "GB / T19139—2012 Oil Well Cement Test Method".

[0100] Comparative Example 3

[0101] The specific composition of the high-temperature, large-temperature-difference, low-density cement slurry used in this comparative example is shown in Table 8.

[0102] Table 8. Composition of cement slurry in Comparative Example 3

[0103] Component Name weight parts / portion Oil well cement 100 High temperature strength stabilizer 15 Relief agent 30 Early strength agent 0.6 High-temperature suspension stabilizer 0.7 High-temperature dehydration agent 5 High temperature retarder 0.3 water 70

[0104] In this comparative example, the oil well cement is Grade G oil well cement, whose chemical requirements and physical properties meet the API specifications and the national standard GB / T 10238—2015 Oil Well Cement.

[0105] In this comparative example, the high-temperature strength stabilizer is quartz sand, whose chemical composition meets the following requirements: SiO2 ≥ 98wt%, and whose physical properties meet the following requirements: specific surface area ≥ 250kg / m². 2 .

[0106] In this comparative example, the weight-reducing agent is hollow microspheres for oil well cement, whose physical properties meet the following requirements: purity ≥ 97%, density 0.3 g / cm³. 3 The particle size is between 10-120μm, the mesh size is 300 mesh, and the floatability is >90%.

[0107] In this comparative example, the early strength agent is a common early strength agent for oil well cement on the market. The main components of this type of early strength agent are nanomaterials, inorganic salts and other materials.

[0108] In this comparative example, the high-temperature suspension stabilizer is a common oil well cement suspension stabilizer on the market. The main components of this type of high-temperature suspension stabilizer are polymer and clay.

[0109] In this comparative example, the high-temperature fluid loss reducing agent is a common high-temperature fluid loss reducing agent for oil well cement on the market. This type of fluid loss reducing agent is polymerized and modified from AMPS (2-acrylamide-2-methylpropanesulfonic acid), acrylamide, polyhydroxycarboxylic acid, etc.

[0110] In this comparative example, the high-temperature retarder is a common high-temperature retarder for oil well cement on the market. This type of retarder is polymerized from AMPS, acrylic acid, high-temperature resistant unsaturated monomers, etc.

[0111] According to Table 7, weigh 100 parts of oil well cement, 15 parts of high-temperature strength stabilizer, 30 parts of weight-reducing agent, 0.6 parts of early-strength agent, 0.7 parts of high-temperature suspension stabilizer, 5 parts of high-temperature fluid loss reducer, 0.3 parts of high-temperature retarder and 70 parts of water, and prepare high-temperature, large-temperature-difference, low-density cement slurry No. 3 according to "GB / T19139—2012 Oil Well Cement Test Method".

[0112] Test case

[0113] The engineering performance of the cement slurry in each comparative example and embodiment was tested according to "SY / T6544—2017 Performance Requirements for Oil Well Cement Slurry". The test method for the 60℃ strength of the cement slurry top was as follows: the cement slurry was heated to 150℃, held for 30 minutes, then the machine was stopped, and the slurry was allowed to cool naturally to 60℃. The thickening test cup was then removed, the thickening oil on top of the cup was completely removed, the cement slurry was poured into a mold, and placed in a 60℃ water bath for curing at 24h and 48h. The test method for high-temperature settling stability was as follows: following the thickening test procedure, the cement slurry was heated to 150℃, held for 30 minutes, stirring was stopped, and the slurry was cooled to 60℃. The thickening cup was then removed, allowed to stand at room temperature for 2h, the thickening oil on top of the cup was removed, and the density of the cement slurry in the upper and lower parts of the cup was measured, and the density difference between the upper and lower parts was calculated. The experimental results are shown in Table 9.

[0114] Table 9. Experimental Results of Examples and Comparative Examples

[0115]

[0116]

[0117] As shown in Table 9, compared with the prior art, the high-temperature, large-temperature-difference, early-strength, low-density cement slurry provided by this invention has superior overall performance. Specifically, the high-temperature, large-temperature-difference, early-strength, low-density cement slurry of this invention exhibits better free liquid and rheological properties, with a maximum API water loss of only 62 mL at 150℃, and a high-temperature settling stability of less than 0.05 g / cm³ at 150℃. 3 The high-temperature settlement stability at 150℃ of the high-temperature cement slurry with large temperature difference and low density prepared using existing technology is greater than 0.05 g / cm³. 3 This indicates that the high-temperature, large-temperature-difference, early-strength, low-density cementing cement of the present invention has excellent high-temperature settlement stability.

[0118] In addition, from Figures 1-6 It can be seen that the high-temperature, large-temperature-difference, low-density cement slurry prepared using existing technologies is prone to abnormal gelation during the high-temperature thickening process, resulting in significant fluctuations in the high-temperature thickening curve. In contrast, the high-temperature, large-temperature-difference, early-strength, low-density cement slurry prepared by this invention exhibits superior high-temperature thickening performance. No abnormal gelation occurs during the high-temperature thickening process, and the high-temperature thickening curve is stable, exhibiting right-angle thickening. Furthermore, in the low-temperature region at the top of the long-sealed section of the well, the strength development of the high-temperature, large-temperature-difference, low-density cement slurry prepared using existing technologies is slow, even exhibiting retarded or ultra-retarded setting phenomena. However, the high-temperature, large-temperature-difference, early-strength, low-density cement slurry provided by this invention develops its strength rapidly, exhibiting higher early strength, and its high-temperature strength does not decline within 14 days.

[0119] Finally, it should be noted that the above embodiments are merely preferred embodiments of the present invention used to illustrate the technical solutions of the present invention, and are not intended to limit the invention, nor are they intended to limit the patent scope of the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. These modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention. That is to say, any changes or refinements made to the main design concept and spirit of the present invention that are not of substantial significance, but whose technical problems are still consistent with the present invention, should be included within the protection scope of the present invention. In addition, the direct or indirect application of the technical solutions of the present invention to other related technical fields are similarly included within the patent protection scope of the present invention.

Claims

1. A high temperature, large temperature range, early strength, low density cement slurry for cementing wells, characterized in that it comprises: The oil well cement 100 parts; the high-temperature strength stabilizer 15-35 parts; the lightening agent 10-30 parts; the early strength agent 0.2-0.6 parts; the high-temperature suspension stabilizer 0.3-0.7 parts; the high-temperature fluid loss agent 1-5 parts; the high-temperature retarder 0.3-0.7 parts; and the water 50-70 parts. The early strength agent is a crystal nucleus type early strength agent, and comprises one or more of nano-hydrated calcium silicate particles, nano calcium silicate, nano silicon dioxide, and nano calcium carbonate, and the particle size of the nano-hydrated calcium silicate particles, the nano calcium silicate, the nano silicon dioxide, and the nano calcium carbonate is in the range of 50-100 nm. The high-temperature retarder is a random copolymer with a molecular weight of 20000-40000, which is prepared by free radical aqueous solution polymerization with 30-45 parts of acrylamide, 30-40 parts of maleic anhydride, 10-20 parts of 3-allyloxy-2-hydroxy-1-propanesulfonate, and 5-10 parts of dimethyldiallylammonium chloride as monomers, and 2-4 parts of sodium bisulfite-ammonium persulfate as a composite initiator. The high-temperature fluid loss agent is a G33S fluid loss agent. The preparation method of the high-temperature retarder is as follows: S1, at room temperature, 30-45 parts of acrylamide, 30-40 parts of maleic anhydride, 10-20 parts of 3-allyloxy-2-hydroxy-1-propanesulfonate, and 5-10 parts of dimethyldiallylammonium chloride are added to 100 parts of water, and then fully dissolved and mixed to obtain a first mixed solution; S2, at room temperature, a 20% sodium hydroxide solution is used to adjust the pH of the first mixed solution to 7-8 to obtain a second mixed solution; S3, at room temperature, 1-2 parts of sodium bisulfite is added to 23-24 parts of water, and then fully dissolved and mixed to obtain a third mixed solution; 1-2 parts of ammonium persulfate is added to 23-24 parts of water, and then fully dissolved and mixed to obtain a fourth mixed solution; S4, the second mixed solution is transferred to a reaction kettle with a stirring device, nitrogen is introduced to remove oxygen in the reaction kettle and maintain a nitrogen atmosphere, the second mixed solution is stirred and heated to 60°C, then the third mixed solution is added dropwise into the second mixed solution through a constant-pressure funnel device, after the dropwise addition is completed, the fourth mixed solution is also added dropwise into the second mixed solution through a constant-pressure funnel device, after the dropwise addition is completed, a fifth mixed solution is obtained; S5, the fifth mixed solution is kept at 60°C for 3 h, then naturally cooled to 45°C and kept at 45°C for 1-2 h, and then the ninth mixed solution is obtained, which is the high-temperature retarder. In S4, the stirring speed in the stirring and heating is 200 r / min, and the dropwise addition speed of the third mixed solution and the fourth mixed solution is 10 drops / min.

2. The high-temperature, large-temperature-difference, early-strength, low-density cementing slurry according to claim 1, characterized in that, The oil well cement is mixed by G-grade cement and D-grade cement, and the main mineral composition of the oil well cement is as follows: C3S: 60-68wt%, C2S: 20-25wt%, C3A: 0-1wt%, C4AF: 12-14wt%; the physical properties of the oil well cement meet: specific surface area ≥ 400m 2 / kg, SO3 content ≤ 3wt%.

3. The high-temperature, large-temperature-difference, early-strength, low-density cementing slurry according to claim 1, characterized in that, The high-temperature strength stabilizer is mixed by quartz sand, kyanite powder, medical stone and metakaolin; the physical properties of the quartz sand meet: specific surface area ≥ 500 kg / m 3 ; The physical properties of the kyanite powder satisfy: specific surface area ≥ 500 kg / m 3 ; The physical properties of the medical stone satisfy: specific surface area ≥ 500 kg / m 3 ; The physical properties of the metakaolin satisfy: specific surface area ≥ 1000 kg / m 3 .

4. The high-temperature, large-temperature-difference, early-strength, low-density cementing slurry according to Claim 1, characterized in that, The reducing agent is one or a mixture of several of poplar powder, rubber powder, plastic powder; the physical properties of the poplar powder meet: density ≤ 0.40 g / cm 3 , specific surface area ≥ 300 kg / m 3 ; the physical properties of the rubber powder meet: density ≤ 1.3 g / cm 3 , specific surface area ≥ 500 kg / m 3 ; the physical properties of the plastic powder meet: density ≤ 1.5 g / cm 3 , specific surface area ≥ 500 kg / m 3 .

5. The high-temperature, large-temperature-difference, early-strength, low-density cementing slurry according to Claim 1, characterized in that, The high-temperature suspension stabilizer is a mixture of polyvinyl alcohol 1788, hectorite powder and dolomite powder; the physical properties of the polyvinyl alcohol 1788 meet the following requirements: purity ≥ 93.5%, specific surface area ≥ 200 kg / m 3 ; The physical properties of the hectorite powder satisfy: specific surface area ≥ 350 kg / m 3 ; The physical properties of the dolomite powder satisfy: specific surface area ≥ 1000 kg / m 3 .

6. The high-temperature, large-temperature-difference, early-strength, low-density cementing slurry according to Claim 1, characterized in that, ​ 7. The high-temperature, large-temperature-difference, early-strength, low-density cementing slurry according to Claim 1, characterized in that, ​ ​ ​ ​ ​ ​ 8. The high-temperature, large-temperature-difference, early-strength, low-density cementing slurry according to claim 7, characterized in that, ​ 9. The preparation method of the high-temperature and large-temperature-difference early-strength low-density cementing slurry according to any one of claims 1-8, characterized in that, The method comprises the following steps: taking 100 parts of oil well cement, 10-35 parts of high-temperature strength stabilizer, 10-30 parts of lightening agent, 0.2-0.6 parts of early strength agent, 0.3-0.7 parts of high-temperature suspension stabilizer, 1-5 parts of high-temperature fluid loss additive, 0.3-0.7 parts of high-temperature retarder and 50-70 parts of water by mass fraction, and preparing the high-temperature large-temperature-difference early-strength low-density cementing slurry according to the oil well cement test method (GB / T19139-2012).

Images