Large-temperature-difference quick-drying cement paste suitable for deep well long-sealing one-time upward-returning well cementation and well cementation method

Abstract

The invention belongs to the technical field of oil and gas well drilling and completion engineering, and particularly relates to large-temperature-difference quick-drying cement paste suitable for deep well long-sealing one-time upward-returning well cementation and a well cementation method. The cement paste comprises 100 parts of oil well cement, 10-40 parts of superfine oil well cement, 4-10 parts of a superfine active reinforcing material, 3-6 parts of a lightening material, 4-10 parts of a low-temperature coagulation-accelerating early-strength material, 1-2 parts of a dispersing agent, 2-5 parts of a large-temperature-difference fluid loss agent, 2-4 parts of a large-temperature-difference retarder, 0.1-0.5 part of a defoaming agent and 38-65 parts of clear water. Under the conditions that the top normal temperature is 20 DEG C and the temperature difference reaches up to 110 DEG C, the 84h compressive strength of the set cement top is larger than 3.5 MPa, the well cementation quality is improved, the well drilling and completion period is shortened, and the well building cost is reduced.

Description

Technical Field

[0001] This invention belongs to the field of oil and gas well drilling and completion engineering technology, specifically relating to a large temperature difference fast-drying cement slurry and cementing method suitable for deep well long-sealing one-time back-flow cementing. Background Technology

[0002] As the exploration and development of shallow and medium-depth onshore oil and gas resources in China continues to improve, the difficulty of discovering new oil and gas resources is increasing. Due to the characteristics of deep burial, ultra-high temperature, and ultra-high pressure, the field of efficient drilling and completion engineering for ultra-deep oil and gas resources still faces many challenges.

[0003] For ultra-deep wellbore cementing with casing and production line reconnection, there are often extremely long cementing sections (>6000m) with large temperature differences between the top and bottom (80-110℃). It is difficult to balance the cement slurry performance with safe construction time and the strength development requirements of the cement slurry in the low-temperature environment at the top, especially in open-hole sections with low formation fracture pressure coefficients. Currently, staged cementing and forward injection / reverse squeeze cementing processes are mainly adopted. Staged cementing is a special cementing process. By adding staged cement injectors (staged collars) to the casing string, cementing operations can be completed in two or more stages. This achieves leakage prevention in low-pressure zones of the cemented section and reduces the temperature difference between the top and bottom of a single cementing operation, improving the cementing success rate. However, multi-stage cementing also has significant drawbacks: firstly, it increases the cementing operation procedures and costs, extending the drilling and completion cycle; secondly, due to complex wellbore conditions and high downhole temperature and pressure, the staged collars may not be able to open or close properly, easily causing cementing complexity and, in severe cases, cementing failure, resulting in the casing string and cement sheath system losing their complete seal. The biggest drawback of the forward injection and reverse squeeze cementing process is that the location of the leaking layer that is squeezed out is uncertain in practice. It is easy for the forward injection and reverse squeeze cement to fail to connect, forming a local free casing section. The cementing quality is difficult to guarantee, which affects the integrity and sealing of the wellbore.

[0004] To improve the success rate of cementing in ultra-long cemented sections (>6000m) and ensure the sealing integrity of the casing string and cement sheath system, conventional cementing processes remain the preferred option when formation pressure tests confirm the conditions for single-pass cement slurry return. These processes are characterized by simplicity, high success rate, and ease of ensuring cement sheath integrity and sealing. This has spurred continuous research and development of cement slurry technology for long cemented sections with large temperature differences. The aim is to develop cement slurry systems with a wide applicable temperature range, broad cement slurry density range, stable slurry properties, and faster top strength development to improve cementing quality, shorten drilling and completion cycles, and reduce well construction costs. Summary of the Invention

[0005] To address the technical challenges of the existing deep well cementing process involving a single-pass return of cement slurry for ultra-long sealing sections (>6000m), where the top is at room temperature (20℃) and there is a large temperature difference between the top and bottom (80-110℃), resulting in slow strength development or even excessively slow setting of the cement slurry, this invention provides a high-temperature-drying cement slurry and cementing method suitable for single-pass return cementing of deep wells with long sealing sections.

[0006] The technical solution provided by this invention is as follows:

[0007] The first aspect of this invention provides an ultrafine active reinforcing material suitable for cement slurry with large temperature difference, which is composed of fly ash, slag powder and microsilica.

[0008] The weight ratio of fly ash, slag powder, and silica fume is 1-3:1-2:1-3.

[0009] This ultrafine active reinforcing material can be used for cementing the top or bottom of wells.

[0010] The fly ash is fine fly ash and slag obtained from the flue gas of boilers in coal-fired power plants and power plants that comprehensively utilize coal gangue and coal slime resources after being collected by a dust collector. It is commercially available.

[0011] The slag powder is commercially available blast furnace slag powder produced in accordance with GB / T18046-2017 "Granulated blast furnace slag powder for use in cement, mortar and concrete".

[0012] The microsilica powder is amorphous, powdery silica (S₂O₃) obtained by oxidizing silicon vapor discharged through the flue during the smelting of ferrosilicon alloys or industrial silicon and then collecting it through a dust collector. i O2). The average particle size of the microsilica powder is 0.15–0.20 μm, and the specific surface area is 15,000–20,000 m². 2 / kg, with extremely strong surface activity, can improve the early strength and structural density of cement stone, and is commercially available.

[0013] The second aspect of this invention provides a low-temperature accelerating and early-strength material suitable for rapid bonding of cement slurry at the top of cementing wells with large temperature differences. The material comprises triethanolamine, triisopropanolamine, calcium nitrite, sodium sulfate, and a high-efficiency polycarboxylate superplasticizer.

[0014] The weight ratio of triethanolamine, triisopropanolamine, calcium nitrite, sodium sulfate, and high-efficiency polycarboxylate superplasticizer is 1-3:1-3:1-2:0.5-2:1-2, and the high-efficiency polycarboxylate superplasticizer is commercially available.

[0015] The third aspect of this invention provides a high-temperature-drying cement slurry suitable for deep well long-term sealing and one-time backfilling cementing. The cement slurry comprises the following raw materials in parts by weight: 100 parts oil well cement, 10-40 parts ultrafine oil well cement, 4-10 parts ultrafine active reinforcing material, 3-6 parts weight-reducing material, 4-10 parts low-temperature setting and early-strength material, 1-2 parts dispersant, 2-5 parts high-temperature-diffusion-reducing agent, 2-4 parts high-temperature-diffusion-retarding agent, 0.1-0.5 parts defoamer, and 38-65 parts clean water.

[0016] The oil well cement mentioned is commercially available Grade G oil well cement produced in accordance with GB / T 10238-2015 "Oil Well Cement". Grade G oil well cement is one of the most commonly used cement materials in oil and gas well cementing operations, and its main component is tricalcium silicate (3CaO·S). i O2), dicalcium silicate (2CaO·S) i O2), tricalcium aluminate (3CaO·Al2O3) and tetracalcium aluminoferrite (4CaO·Al2O3·Fe2O3). As the main component of cementing cement, under the high temperature and hydrothermal environment in the well, G-grade oil well cement can be uniformly mixed with other admixtures, additives and water to form cement slurry, which is then injected into the casing annulus. Under the temperature and pressure conditions downhole, it undergoes a hydration reaction to generate hydration products, namely cement stone.

[0017] The ultrafine oil well cement is a fast-hardening, early-strength hydraulic cementitious material formed by re-grinding Grade G oil well cement, and is commercially available. Ultrafine cement particles are fine, have a large specific surface area, a fast hydration rate, and a short time to gel and develop strength.

[0018] The ultrafine active reinforcing material is the composite material provided in the first aspect;

[0019] The weight-reducing material is high-strength glass microspheres, and the true density of the high-strength glass microspheres is 0.60 ± 0.03 g / cm³. 3 The median particle size Dv(50) is 45 μm. The high-strength glass microspheres used in this invention are preferably Y12000 type high-strength glass microspheres produced by Maanshan Mining Institute New Materials Technology Co., Ltd. of China Steel Group, with a compressive strength of 82 MPa.

[0020] The low-temperature accelerating and early-strength material is a composite material provided in the second aspect;

[0021] The dispersant is at least one of lignin sulfonates, sulfonated aldehydes and ketones, and polycarboxylic acid polymers;

[0022] The large temperature difference water loss reducing agent is a polymer system based on 2-acrylamido-2-methylpropanesulfonic acid (AMPS), preferably the water loss reducing agent authorized in Chinese patent CN112341576B. This water loss reducing agent has excellent performance, strong adaptability, and can significantly improve the initial rheological properties of cement paste and increase the early compressive strength of cement stone.

[0023] The large temperature difference retarder is a high-temperature oil well cement retarder, preferably a high-temperature resistant copolymer oil well cement retarder authorized by Chinese Patent CN104403056B. This retarder has good high-temperature setting regulation effect, weak high-temperature dispersibility, and minimal impact on the strength development of cement stone at low temperatures;

[0024] The defoamer is an organosilicon or organic ester defoamer.

[0025] The above-mentioned technical solution provides a high-temperature-drying, fast-drying cement slurry suitable for single-stage cementing of deep wells with long sealing operations, used as a top cementing slurry, with a density of 1.45–1.75 g / cm³. 3 With adjustable range and excellent construction performance, it is suitable for well bottom static temperature not exceeding 150℃, circulating temperature not exceeding 130℃, top temperature 20℃, and temperature difference not exceeding 110℃. The compressive strength of the cement stone top is >3.5MPa after 84 hours, which is beneficial to improve cementing quality, shorten drilling and completion cycle, and reduce well construction cost.

[0026] The preparation method of the fast-drying cement slurry with large temperature difference at the top, suitable for one-time back cementing of deep wells with long sealing, is as follows:

[0027] Weigh out 100 parts of oil well cement, 10-40 parts of ultrafine oil well cement, 4-10 parts of ultrafine active reinforcing material, 2-6 parts of light-reducing material, 4-10 parts of low-temperature setting and early-strength material, and 1-2 parts of dispersant as needed. Mix the above materials thoroughly to form a solid mixture.

[0028] Weigh out 38-65 parts of clean water, 2-5 parts of large temperature difference dehydration agent, 2-4 parts of large temperature difference retarder, and 0.1-0.5 parts of defoamer into a mixing cup as needed. Mix thoroughly at a speed of 4000rpm±200rpm to obtain a slurry. Maintain this speed and add the solid mixture evenly into the slurry within 15s. Continue stirring at a speed of 4000rpm±200rpm for 35s±1s. A fast-drying cement slurry with a large temperature difference at the top, suitable for deep well long-term sealing and one-time backfilling cementing, is now ready.

[0029] A fourth aspect of the present invention provides a cementing method, comprising at least the following steps:

[0030] The aforementioned high-temperature-drying cement slurry is used for cementing the top of the drilling and completion well in oil and gas wells;

[0031] Quick-drying cement slurry is used for cementing the bottom of oil and gas wells after drilling and completion.

[0032] The quick-drying cement slurry comprises the following raw materials in parts by weight: 100 parts oil well cement, 10-40 parts ultrafine oil well cement, 4-10 parts ultrafine active reinforcing material, 3-6 parts weight-reducing material, 1-2 parts dispersant, 2-5 parts large temperature difference water loss reducing agent, 2-4 parts large temperature difference retarder, 0.1-0.5 parts defoamer, and 38-65 parts clean water.

[0033] The quick-drying cement slurry with large temperature difference at the top is more suitable for long-term sealing and one-time back cementing of deep wells. The quick-drying cement slurry used at the bottom may or may not contain ultrafine active reinforcing materials, and no low-temperature accelerator or early-strength material is added.

[0034] Specifically, the temperature conditions for well completion are:

[0035] The top temperature is 10–30℃;

[0036] The bottom temperature is 100-130℃.

[0037] The maximum drilling and completion depth of the oil and gas wells is greater than or equal to 6000m, meeting the standard for ultra-long sealing sections in deep wells.

[0038] Compared with the prior art, the present invention has the following advantages:

[0039] 1) The ultrafine active reinforcing material provided by the present invention achieves multi-element particle size distribution of the system by optimizing and adjusting the weight ratio of fly ash, slag powder and microsilica, thereby improving the system density and promoting the improvement of the compressive strength of cement stone.

[0040] 2) The low-temperature accelerating and early-strength material provided by this invention achieves chemical activation of the system by optimizing and adjusting the weight ratio of triethanolamine, triisopropanolamine, calcium nitrite and sodium sulfate, which promotes rapid hydration of cement slurry in the low-temperature environment at the top, achieving the effect of rapid setting and drying; on the other hand, the addition of high-efficiency polycarboxylate superplasticizer helps to effectively suppress the slurry thickening effect caused by rapid hydration, reduce the flow resistance of cement slurry, and ensure safe construction.

[0041] 3) The high-temperature, large-temperature-difference top-drying cement slurry system provided by this invention features a preferred large-temperature-difference retarder with good high-temperature setting effect. The thickening time is adjustable from 300 to 480 minutes, meeting the requirements for safe cementing operations in deep wells with long-term sealing and single-pass backfilling. It has minimal impact on the strength development of the cement slurry under low-temperature conditions, effectively preventing excessively slowed setting of the top cement slurry under low-temperature conditions and improving the early compressive strength of the cement stone. At a top temperature of 20℃ and a temperature difference as high as 110℃, the compressive strength of the cement stone top after 84 hours is >3.5 MPa, which is beneficial for improving cementing quality, shortening drilling and completion cycles, and reducing well construction costs. Attached Figure Description

[0042] Figure 1 This is the thickening time experimental curve of Example A (364 min / 70 BC).

[0043] Figure 2 This is the thickening time experimental curve of Example B (388 min / 70 Bc).

[0044] Figure 3 This is the thickening time experimental curve for Example C (343 min / 70 Bc).

[0045] Figure 4 This is the thickening time experimental curve of Example D (333 min / 70 Bc).

[0046] Figure 5 This is the thickening time experimental curve of Comparative Example A (375 min / 70 Bc).

[0047] Figure 6 This is the thickening time experimental curve of Comparative Example B (360 min / 70 Bc). Detailed Implementation

[0048] The principles and features of the present invention are described below. The embodiments given are only for explaining the present invention and are not intended to limit the scope of the present invention.

[0049] Unless otherwise specified, the test methods used in the embodiments of this invention are conventional methods; unless otherwise specified, the materials and reagents used are commercially available.

[0050] In the following examples and comparative examples, the performance parameters of the cement slurry were measured according to GB / T 19139-2012 "Test Methods for Oil Well Cement". The oil well cement was Grade G medium sulfate-resistant oil well cement produced by Shawan Tianshan Cement Co., Ltd. The ultrafine oil well cement was obtained by further grinding this oil well cement.

[0051] Preparation Example 1

[0052] Fly ash, slag powder, and microsilica powder were mixed evenly in a weight ratio of 1.5:1:3 to obtain ultrafine active reinforcing material CX1.

[0053] Preparation Example 2

[0054] Fly ash, slag powder, and microsilica powder were mixed evenly in a weight ratio of 2:1.5:2 to obtain the ultrafine active reinforcing material CX2.

[0055] Preparation Example 3

[0056] Triethanolamine, triisopropanolamine, calcium nitrite, sodium sulfate, and high-efficiency polycarboxylate superplasticizer were mixed evenly in a weight ratio of 1:1:1.5:1:1 to obtain low-temperature accelerated setting and early strength material ZQ1.

[0057] Preparation Example 4

[0058] Triethanolamine, triisopropanolamine, calcium nitrite, sodium sulfate, and high-efficiency polycarboxylate superplasticizer were mixed evenly in a weight ratio of 2:1:1.5:1:1.5 to obtain low-temperature accelerated setting and early strength material ZQ2.

[0059] Example A

[0060] S1: Weigh the following materials as needed: 100 parts oil well cement, 15 parts ultrafine oil well cement, 4 parts ultrafine active reinforcing material CX1, 4 parts lightening material, 4 parts low-temperature accelerating and early-strength material ZQ1, and 1.2 parts dispersant. Mix the above materials thoroughly to form a solid mixture.

[0061] S2: Weigh out 55 parts of clean water, 3 parts of large temperature difference dehydration agent, 3 parts of large temperature difference retarder, and 0.2 parts of defoamer from the mixing cup as needed; mix thoroughly at a speed of 4000rpm±200rpm to obtain the slurry.

[0062] S3: Maintain a rotation speed of 4000rpm±200rpm and uniformly add the solid mixture to the slurry within 15s. Continue stirring at a rotation speed of 4000rpm±200rpm for 35s±1s to obtain the high-temperature, large-temperature-difference top quick-drying cement slurry A.

[0063] The high-temperature, high-temperature-difference top-drying cement slurry A has a density of 1.75 g / cm³. 3 The liquid-to-solid ratio is 0.477. According to the GB-T19139 oil well cement test method, the thickening time at 120℃×102MPa×90min is 364min, the API water loss is 42mL, and the compressive strength of the cement stone after curing at 20℃×0.1MPa for 84h is 7.4MPa.

[0064] Example B

[0065] S1: Weigh the following materials as needed: 100 parts oil well cement, 15 parts ultrafine oil well cement, 4 parts ultrafine active reinforcing material CX1, 4 parts lightening material, 4 parts low-temperature accelerating and early-strength material ZQ1, and 1.2 parts dispersant. Mix the above materials thoroughly to form a solid mixture.

[0066] S2: Weigh out 54.8 parts of clean water, 3 parts of large temperature difference water loss reducer, 3.2 parts of large temperature difference retarder, and 0.2 parts of defoamer from the mixing cup as needed; mix thoroughly at a speed of 4000rpm±200rpm to obtain the slurry.

[0067] S3: Maintain a rotation speed of 4000rpm±200rpm and uniformly add the solid mixture to the slurry within 15s. Continue stirring at a rotation speed of 4000rpm±200rpm for 35s±1s to obtain the high-temperature, large-temperature-difference top quick-drying cement slurry B.

[0068] The high-temperature, high-temperature-difference top-drying cement slurry B has a density of 1.75 g / cm³. 3 The liquid-to-solid ratio is 0.477. According to the GB-T19139 oil well cement test method, the thickening time at 120℃×102MPa×90min is 388min, the API water loss is 38mL, and the compressive strength of the cement stone after curing at 20℃×0.1MPa for 84h is 6.5MPa.

[0069] Example C

[0070] S1: Weigh the following materials as needed: 100 parts oil well cement, 30 parts ultrafine oil well cement, 5 parts low-temperature setting and early strength material CX2, 12 parts weight-reducing material, 6 parts low-temperature setting and early strength material ZQ2, and 1.5 parts dispersant. Mix the above materials thoroughly to form a solid mixture.

[0071] S2: Weigh out 74 parts of clean water, 3 parts of large temperature difference dehydration agent, 3 parts of large temperature difference retarder, and 0.2 parts of defoamer from the mixing cup as needed; mix thoroughly at a speed of 4000rpm±200rpm to obtain the slurry.

[0072] S3: Maintain a rotation speed of 4000rpm±200rpm and uniformly add the solid mixture to the slurry within 15s. Continue stirring at a rotation speed of 4000rpm±200rpm for 35s±1s to obtain the high-temperature, large-temperature-difference top quick-drying cement slurry C.

[0073] The high-temperature, large-temperature-difference top-drying cement slurry C has a density of 1.60 g / cm³. 3 The liquid-to-solid ratio was 0.519. According to the GB-T19139 oil well cement test method, the thickening time at 120℃×102MPa×90min was 343min, the API water loss was 44mL, and the compressive strength of the cement stone after curing at 20℃×0.1MPa for 84h was 5.2MPa.

[0074] Example D

[0075] S1: Weigh the following materials as needed: 100 parts oil well cement, 40 parts ultrafine oil well cement, 6 parts ultrafine active reinforcing material CX2, 28 parts lightweighting material, 9 parts low-temperature accelerating and early-strength material ZQ2, and 2 parts dispersant. Mix the above materials thoroughly to form a solid mixture.

[0076] S2: Weigh out 88 parts of clean water, 3 parts of large temperature difference water loss reducer, 3 parts of large temperature difference retarder, and 0.2 parts of defoamer from the mixing cup as needed; mix thoroughly at a speed of 4000rpm±200rpm to obtain the slurry.

[0077] S3: Maintain a rotation speed of 4000rpm±200rpm and uniformly add the solid mixture to the slurry within 15s. Continue stirring at a rotation speed of 4000rpm±200rpm for 35s±1s to obtain the high-temperature, large-temperature-difference top-drying cement slurry D.

[0078] The high-temperature, large-temperature-difference top-drying cement slurry D has a density of 1.45 g / cm³. 3 The liquid-to-solid ratio was 0.509. According to the GB-T19139 oil well cement test method, the thickening time at 120℃×102MPa×90min was 333min, the API water loss was 36mL, and the compressive strength of the cement stone after curing at 20℃×0.1MPa for 84h was 4.0MPa.

[0079] Comparative Example A

[0080] Following the method of Example A, except that 4 parts of low-temperature accelerating and early-strength material ZQ1 were not added to the solid mixture, and the amount of large temperature difference retarder added to the slurry was reduced to 2.6 parts to adjust the thickening time to be within 20 minutes of the thickening time of Example A. The other conditions were the same, and comparative cement slurry A was obtained.

[0081] The comparative example cement slurry A has a density of 1.75 g / cm³. 3 The liquid-to-solid ratio is 0.48. According to the GB-T19139 oil well cement test method, the thickening time at 120℃×102MPa×90min is 375min, the API water loss is 40mL, and the compressive strength of the cement stone after curing at 20℃×0.1MPa for 84h is 3.2MPa.

[0082] Comparative Example B

[0083] Following the method of Example D, except that 9 parts of low-temperature accelerating and early-strength material ZQ2 were not added to the solid mixture, and the amount of large temperature difference retarder added to the slurry was reduced to 2.2 parts to adjust the thickening time to be within 20 minutes of the thickening time in Example D. The other conditions were the same, and comparative cement slurry B was obtained.

[0084] The comparative example cement slurry B has a density of 1.45 g / cm³. 3 The liquid-to-solid ratio was 0.487. According to the GB-T19139 oil well cement test method, the thickening time at 120℃×102MPa×90min was 360min, the API water loss was 46mL, and the cement slurry did not solidify after curing at 20℃×0.1MPa for 84h.

[0085] Table 1 Performance data of fast-drying cement slurry at high temperature and large temperature difference.

[0086]

[0087] As shown in Table 1, the density of the cement slurry in the above embodiments is between 1.45 and 1.75 g / cm³. 3 Adjustable flow range, all with a flowability >20cm, zero free liquid, and density difference ≤0.01g / cm³. 3 This indicates that the slurry has good fluidity and stability; the API water loss is all <50mL, the thickening time is adjustable from 300 to 480 minutes, and the thickening curve is normal (see attached). Figures 1 to 6 (These are the thickening time experimental curves for each example); the compressive strength of the cement stone at 20℃ for 84 hours is all >3.5MPa (temperature difference 100℃);

[0088] Under the same experimental conditions, the free liquid of Comparative Example A without the addition of low-temperature coagulation-promoting and early-strength material ZQ1 was 0.8%, with a density difference of 0.02 g / cm³. 3 This indicates that the stability of the slurry has deteriorated; most importantly, the top compressive strength decreased by 56.76% to 3.2 MPa after 84 hours under large temperature difference conditions.

[0089] Under the same experimental conditions, the free liquid of Comparative Example B without the addition of low-temperature coagulation-promoting and early-strength material ZQ2 was 1.2%, with a density difference of 0.03 g / cm³. 3 This indicates that the stability of the slurry has deteriorated; most importantly, the top did not solidify after 84 hours under large temperature difference conditions.

[0090] In summary, this invention provides a high-temperature-drying, top-mounted cement slurry suitable for deep wells with long-term sealing and single-stage backfilling. Utilizing ultrafine oil well cement, fly ash, slag powder, and microsilica powder as ultrafine active reinforcing materials, it achieves a multi-element particle size distribution, improving the density of the cement stone structure. Simultaneously, with the assistance of low-temperature setting-promoting and early-strength materials, it achieves chemical activation, promoting rapid hydration of the cement slurry in the low-temperature environment at the top, resulting in rapid setting and drying. The preferred high-temperature-drying retarder exhibits good high-temperature setting regulation and has minimal impact on the strength development of the cement slurry under low-temperature conditions, effectively preventing excessively slow setting of the top-mounted cement slurry under low-temperature conditions and improving the early compressive strength of the cement stone. The cement slurry density is 1.45–1.75 g / cm³. 3 The cement stone exhibits adjustable thickness range (300-480 min), excellent workability, and is suitable for wellbore bottom static temperatures not exceeding 150℃ and circulating temperatures not exceeding 130℃. At a top temperature of 20℃ and a temperature difference not exceeding 110℃, the cement stone top has a compressive strength >3.5MPa after 84 hours, which is beneficial for improving cementing quality, shortening drilling and completion cycles, and reducing well construction costs.

[0091] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A large temperature difference fast drying cement slurry suitable for deep well long sealing once up back to well, characterized in that, The raw materials include the following parts by weight: 100 parts oil well cement, 10-40 parts ultrafine oil well cement, 4-10 parts ultrafine active reinforcing material, 3-6 parts lightweighting material, 4-10 parts low-temperature accelerator and early strength material, 1-2 parts dispersant, 2-5 parts large temperature difference water loss reducer, 2-4 parts large temperature difference retarder, 0.1-0.5 parts defoamer, and 38-65 parts clean water.

2. The fast-drying cement slurry with large temperature difference suitable for the long-sealing and one-time up-returning well fixation in deep well of claim 1, characterized in that: The ultrafine active reinforcing material is composed of fly ash, slag powder and microsilica, wherein the weight ratio of fly ash, slag powder and microsilica is 1-3:1-2:1-3.

3. The fast-drying cement slurry with large temperature difference suitable for one-time backfilling cementing of deep wells as described in claim 1, characterized in that: The low-temperature accelerating and early-strength material is composed of triethanolamine, triisopropanolamine, calcium nitrite, sodium sulfate and high-efficiency polycarboxylate superplasticizer, wherein the weight ratio of triethanolamine, triisopropanolamine, calcium nitrite, sodium sulfate and high-efficiency polycarboxylate superplasticizer is 1~3:1~3:1~2:0.5~2:1~2.

4. The fast-drying cement slurry with large temperature difference suitable for one-time backfilling cementing of deep wells with long sealing as described in claim 1, characterized in that: The oil well cement is Grade G oil well cement; The ultrafine oil well cement is G-grade oil well cement that has been ground.

5. The fast-drying cement slurry with large temperature difference suitable for one-time backfilling cementing of deep wells with long sealing as described in claim 1, characterized in that: The weight-reducing material is high-strength glass microspheres; The dispersant is a lignin sulfonate dispersant, a sulfonated aldehyde-ketone dispersant, or a polycarboxylic acid dispersant; The defoamer is a silicone-based defoamer or an organic ester defoamer.

6. The fast-drying cement slurry with large temperature difference suitable for one-time backfilling cementing of deep wells as described in claim 1, characterized in that: The large temperature difference water loss reducing agent is a 2-acrylamido-2-methylpropanesulfonic acid polymer; The large temperature difference retarder is a high-temperature oil well cement retarder.

7. A cementing method, characterized in that, At least the following steps are included: The high temperature difference fast-drying cement slurry as described in any one of claims 1 to 6 is used for cementing the top of the drilling and completion of oil and gas wells; Quick-drying cement slurry is used for cementing the bottom of oil and gas wells after drilling and completion.

8. The cementing method according to claim 7, characterized in that: The quick-drying cement slurry comprises the following raw materials in parts by weight: 100 parts oil well cement, 10-40 parts ultrafine oil well cement, 4-10 parts ultrafine active reinforcing material, 3-6 parts lightweighting material, 1-2 parts dispersant, 2-5 parts large temperature difference water loss reducing agent, 2-4 parts large temperature difference retarder, 0.1-0.5 parts defoamer, and 38-65 parts clean water; The fast-drying cement slurry may or may not contain ultrafine active reinforcing materials.

9. The cementing method according to claim 7, characterized in that: The top temperature is 10–30℃; The bottom temperature is 100-130℃.

10. The cementing method according to claim 7, characterized in that: The maximum drilling and completion depth of the oil and gas well is greater than or equal to 6000m.

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