High temperature resistant cement for deep and ultra-deep well cementing

Abstract

This invention relates to the field of oil and gas well cementing materials, specifically to a high-temperature resistant cement for cementing deep and ultra-deep wells. The cement comprises the following components by weight: 40-50 parts oil well cement, 10-20 parts quartz powder, 30-45 parts lattice distortion inducing material, and 0.3-1 parts steric hindrance material. This invention solves the problems of strength degradation and increased permeability in current cement systems, improving the strength stability of cement stone in ultra-high temperature formation environments.

Description

Technical Field

[0001] This invention relates to the field of cementing materials for oil and gas wells, specifically to a high-temperature resistant cement for cementing deep and ultra-deep wells. Background Technology

[0002] In recent years, 60% of the world's newly added oil and gas reserves have come from deep formations. my country's deep and ultra-deep oil and gas resources have reached 67.1 billion tons of oil equivalent. In the Tarim Basin, oil and natural gas resources buried at depths of 6,000 to 10,000 meters account for 83.2% and 63.9% of the country's total, respectively. In 2020, my country drilled 302 ultra-deep wells exceeding 6,000 meters, making ultra-deep oil and gas a crucial area for increasing my country's oil and gas production.

[0003] As depth increases, the temperature and pressure at the bottom of the well also increase dramatically. The "Shendi Chuanke 1 Well" will exceed 10,000 meters in depth, and the static temperature at the bottom of the well will exceed 260°C. The deteriorating geological conditions significantly increase the difficulty of cementing oil and gas wells. Cementing is a crucial step in the construction of oil and gas wells and an indispensable component of oil and gas resource development. The complex well conditions of deep and ultra-deep wells pose severe challenges to ultra-high temperature cementing technology and place higher demands on the development and application of cementing slurry technology and cementing materials.

[0004] Under high-temperature curing conditions, the significant strength degradation and increased permeability of cement stone in oil wells pose substantial challenges to improving cementing quality and ensuring the integrity of cement sheath seals. Currently, the most commonly used high-temperature resistant cementing system is the sand-added cementing system, which involves adding a certain proportion of quartz sand to the oil well cement to adjust the calcium-silica molar ratio of the cement slurry to approximately 1.0. When the temperature exceeds 110℃, the main chemical component of quartz sand, SiO2, participates in the hydration reaction, inhibiting the formation of non-cementing high-calcium hydrated calcium silicate (C2SH). Instead, it reacts to generate calcium silicate (C5S6H5), which has good mechanical properties, giving the cement stone a certain degree of high-temperature strength stability. As the curing temperature further increases, the hydration products and internal structure of the cement stone will change again. When the temperature exceeds 160℃, calcium silicate (C5S6H5) gradually transforms into calcium silicate (C5S6H), during which strength degradation will occur again. The higher the temperature, the faster the transformation rate, and the more pronounced the strength degradation.

[0005] The mechanism of secondary strength degradation in sand-added cementitious cement is not yet clear. Current solutions mainly involve two approaches: one is to add smaller siliceous materials (quartz powder, nano-silica, etc.) to the quartz sand, utilizing the close-packing theory to fill the pores of the cement stone and increase the reactivity of the siliceous materials, thereby preventing strength degradation of the cement stone. For example, CN106833567A discloses a high-strength, high-toughness, high-temperature resistant cement slurry system, whose components are: oil well cement, coarse quartz sand, fine quartz sand, nano-silica, fluid loss reducing agent, dispersant, and water. The oil well cement, coarse quartz sand, fine quartz sand, nano-silica, fluid loss reducing agent, and dispersant are mixed evenly, and then water is added and stirred evenly to obtain the high-strength, high-toughness, high-temperature resistant cement slurry system. For example, CN112979221A discloses a high-temperature resistant, elastic, toughness-resistant, and anti-channeling cement slurry system, which includes the following components by weight: 100 parts oil well cement; 30-40 parts silica sand; 3-8 parts polytetrafluoroethylene powder; 0.3-0.7 parts mixed fiber; 1-3 parts nano-liquid silica; and 0.2-1 parts defoamer. The second approach involves adding silicate minerals to the cement slurry system. By influencing the transformation process of siliceous calcium silicate to hard calcium silicate, the high-temperature strength and stability of the cement stone are improved. For instance, CN111072350A discloses a high-temperature resistant cement slurry system in which zirconium silicate and magnesium silicate are added as crystal stabilizers. Metal ions enter the structure of hydrated calcium silicate, preventing the transformation of siliceous calcium silicate in the hydration products to hard calcium silicate, thus exhibiting good high-temperature stability. For example, Zhou Chongfeng et al., in their paper "A Novel Ultra-High Temperature Cement Stone Resistance Material for Strength Degradation," presented a novel ultra-high temperature cement stone resistance material for strength degradation. This material is primarily synthesized from a composite of kaolin, wollastonite, sepiolite, and nanotubes. The aluminum in the resistance material participates in high-temperature hydration, reacting with calcareous silica and diaspore, transforming entirely into aluminum-containing calcareous silica and other stable hydration products at ultra-high temperatures. Simultaneously, the nucleation and bridging effects of nanotubes further enhance the ultra-high temperature strength of the cement stone.

[0006] The above solutions can improve the strength and stability of cement stone within a certain temperature range. However, when the formation temperature rises further to over 240℃, the hydration products of high-temperature cement will be mainly hard calcium silicate. As the high-temperature curing period extends, the interlocking network structure of needle-like hard calcium silicate crystals disappears, and a parallel needle-like structure appears. Grain coarsening occurs, and the density between crystals decreases significantly, resulting in a severe reduction in the high-temperature mechanical properties of cement stone in sand-added oil wells and an increase in permeability. Summary of the Invention

[0007] To address the aforementioned problems in existing technologies, this invention provides a high-temperature resistant cement for cementing deep and ultra-deep wells, which improves the strength stability of cement stone in ultra-high temperature formation environments and solves the problems of strength degradation and increased permeability in current cement systems.

[0008] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0009] A high-temperature resistant cement for cementing deep and ultra-deep wells, comprising the following components in parts by weight:

[0010]

[0011] Furthermore, the lattice distortion inducing material is a mixture of ferrosilicon slag and barite, with a weight ratio of ferrosilicon slag to barite of 4:1.

[0012] Furthermore, the ferrosilicon manganese slag has an amorphous structure, with a MnO content >5% and a powder particle size of 300-500 mesh.

[0013] Furthermore, the barite contains >90% BaSO4, and the barite powder has a particle size of 800-1200 mesh.

[0014] Furthermore, the steric hindrance material is one of nano-titanium dioxide, ultrafine calcium carbonate, or ultrafine graphite powder.

[0015] Furthermore, the nano-titanium dioxide has a rutile structure and a specific surface area > 20 m². 2 / g.

[0016] Furthermore, the particle size of the ultrafine calcium carbonate is >1200 mesh.

[0017] Furthermore, the particle size of the ultrafine graphite powder is >1200 mesh.

[0018] Furthermore, the oil well cement is one of G-grade oil well cement, H-grade oil well cement, or D-grade oil well cement.

[0019] Furthermore, the quartz powder contains >97% SiO2 and has a particle size of 300-500 mesh.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] This invention effectively refines the crystal size of hard silica-calcium silicate by adding lattice distortion-inducing materials and steric hindrance materials, thus preventing the formation of a flower-like structure after the grains grow and coarse, thereby achieving better high-temperature strength and stability.

[0022] When the curing temperature exceeds 240℃, the hydration products of sand-added cement are mainly calcium silicate, and the structure of calcium silicate directly determines the performance of the cement paste. With prolonged curing time, the calcium silicate grains in the sand-added cement gradually grow, evolving from needle-like to leaf-like structures. This grain coarsening leads to an increase in the pore size of the cement paste, creating microscopic defects in the mechanical structure, ultimately resulting in decreased compressive strength and increased permeability. This invention, by incorporating lattice distortion-inducing materials and steric hindrance materials, aims to prevent the growth of calcium silicate from the microstructural level.

[0023] There are two main mechanisms to prevent the growth of hard silicate crystals: one is to dope the hard silicate lattice with large-sized ions to destroy the lattice order and prevent the orderly growth of its grains; the other is to add inert particles to form steric hindrance.

[0024] The lattice distortion inducing material used in this invention is composed of ferrosilicon slag and barite. Besides containing conventional chemical components such as calcium oxide, silicon oxide, and aluminum oxide, it also contains manganese monoxide (MnO) and barium oxide (BaO). Under a high-temperature hydrothermal environment, the ferrosilicon slag gradually hydrolyzes, and Mn enters the aqueous solution in the form of oxide ions, eventually entering the structure of hard calcium silicate and replacing silicon atoms (Si atoms) in the molecular structure. Because Mn... 2+ atomic radius Almost Si 4+ atomic radius Twice the amount of calcium silicate will disrupt the ordered structure of the hard silicate, thus preventing its ordered crystal growth. Similarly, Ba in barite... 2+ Ions will enter the hard silicate crystal structure and replace Ca. 2+ Lattice distortion disrupts the structural order, thereby preventing the crystal from continuing to grow and coarsen.

[0025] The steric hindrance material used in this invention is inert in high-temperature cement slurry, consistently filling the pores of the cement stone as ultrafine particles. This refines the pore size, blocks interconnected pores, effectively improves the density of the cement stone, and reduces its permeability. The steric hindrance material prevents the growth of hard silica-calcium silicate grains at the mesoscopic level. Nano-titanium dioxide, ultrafine calcium carbonate, and ultrafine graphite powder exhibit good thermodynamic stability in high-temperature cement slurry and do not participate in the chemical reactions occurring within the cement hydration products, remaining as an inert filler material within the cement stone. When the steric hindrance material is aligned with the preferred growth direction of the hard silica-calcium silicate grains, it forces them to deflect or cease growth, thereby achieving the goal of grain refinement.

[0026] Meanwhile, the chemical stability of ultrafine materials in high-temperature cementing is crucial to their ability to function as fillers. When ultrafine silica, nano-silica, or nano-alumina are added to high-temperature cement, these materials will ultimately react chemically with Ca ions in the solution to form hydrated calcium silicate and hydrated calcium aluminosilicate, thus eliminating their original ultrafine structure and rendering them ineffective at filling pores. Ultrafine calcium carbonate and ultrafine graphite powder are thermodynamically inert and will not participate in any chemical reactions within the cement. Nano-titanium dioxide can react with calcium oxide to form calcium titanate, but due to the very low solubility of rutile titanium dioxide and its slow reaction rate with calcium oxide, calcium oxide will preferentially react with silicates, thus remaining inert in the cement slurry system. The three ultrafine powders used in this invention all possess excellent chemical stability and will not participate in any chemical reactions occurring within the cementing hydration products. Attached Figure Description

[0027] Figure 1 The image shows the microstructure of the hydration products of the cement slurry prepared in Example 2 after curing at 280°C for 14 days.

[0028] Figure 2 Microstructure of the hydration products of the cement slurry prepared for Comparative Example 1 after curing at 280℃ for 14 days.

[0029] Figure 3 The image shows the XRD diffraction pattern of ferrosilicon manganese slag. Detailed Implementation

[0030] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail. Obviously, the described embodiments are merely some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0031] The oil well cement used in this embodiment of the invention is a product of Jiahua Special Cement Co., Ltd., which meets the performance requirements of the national standard GB / T10238.

[0032] The embodiments of this invention use one of the following: Grade G oil well cement, Grade H oil well cement, or Grade D oil well cement.

[0033] The quartz powder used in this embodiment of the invention was provided by Leshan Fulin Environmental Protection Technology Co., Ltd., with a SiO2 content of 98.4% and a fineness of 375 mesh.

[0034] The lattice distortion inducing material used in this embodiment of the invention is a mixture of ferrosilicon slag and barite, with a weight ratio of ferrosilicon slag to barite of 4:1.

[0035] The ferrosilicon slag used in this embodiment of the invention was provided by Ninghui Building Materials Co., Ltd. of Leshan City, Sichuan Province. The MnO content was 8.68% and the fineness was 325 mesh.

[0036] The barite used in the embodiments of the present invention is a commercially available product with a BaSO4 content of 98.1% and a powder particle size of 1000 mesh.

[0037] The steric hindrance material used in the embodiments of the present invention is one of nano-titanium dioxide, ultrafine calcium carbonate, and ultrafine graphite powder.

[0038] The nano-titanium dioxide used in the embodiments of this invention is a commercially available product with a rutile crystal form, hydrophilic surface properties, and a specific surface area of ​​60 m². 2 / g.

[0039] The ultrafine calcium carbonate used in the embodiments of this invention is a commercially available product with a particle size of 1250 mesh.

[0040] The ultrafine graphite powder used in the embodiments of the present invention is a commercially available product with a particle size of 3000 mesh.

[0041] Example 1

[0042] As a preferred embodiment of the present invention, the specific composition of the high-temperature resistant cement used in this embodiment for cementing deep and ultra-deep wells is shown in Table 1:

[0043] Table 1

[0044] Components weight Grade G oil well cement 40 Quartz powder 20 Lattice distortion-induced materials 39 Ultrafine calcium carbonate 1

[0045] In this embodiment, the steric hindrance material is ultrafine calcium carbonate.

[0046] Weigh each component according to the weight parts in Table 1 and mix them evenly to obtain cementing cement #1.

[0047] Example 2

[0048] As a preferred embodiment of the present invention, the specific composition of a high-temperature resistant cement for cementing deep and ultra-deep wells used in this embodiment is shown in Table 2:

[0049] Table 2

[0050] Components weight Grade G oil well cement 40 Quartz powder 14.5 Lattice distortion-induced materials 45 Ultrafine graphite powder 0.5

[0051] In this embodiment, the steric hindrance material is ultrafine graphite powder.

[0052] Weigh each component according to the weight parts in Table 2 and mix them evenly to obtain cementing cement #2.

[0053] Example 3

[0054] As a preferred embodiment of the present invention, the specific composition of the high-temperature resistant cement used in this embodiment for cementing deep and ultra-deep wells is shown in Table 3:

[0055] Table 3

[0056] Components weight H-grade oil well cement 45 Quartz powder 15 Lattice distortion-induced materials 39.5 Ultrafine graphite powder 0.5

[0057] In this embodiment, the steric hindrance material is ultrafine graphite powder.

[0058] Weigh each component according to the weight parts in Table 3 and mix them evenly to obtain cementing cement #3.

[0059] Example 4

[0060] As a preferred embodiment of the present invention, the specific composition of a high-temperature resistant cement for cementing deep and ultra-deep wells used in this embodiment is shown in Table 4:

[0061] Table 4

[0062] Components weight Grade D oil well cement 50 Quartz powder 19.7 Lattice distortion-induced materials 30 Nano titanium dioxide 0.3

[0063] In this embodiment, the steric hindrance material is nano-titanium dioxide.

[0064] Weigh each component according to the weight parts in Table 4 and mix them evenly to obtain cementing cement #4.

[0065] Example 5

[0066] As a preferred embodiment of the present invention, the specific composition of the high-temperature resistant cement used in this embodiment for cementing deep and ultra-deep wells is shown in Table 5:

[0067] Table 5

[0068]

[0069]

[0070] In this embodiment, the steric hindrance material is nano-titanium dioxide.

[0071] Weigh each component according to the weight parts in Table 5 and mix them evenly to obtain cementing cement #5.

[0072] Comparative Example 1

[0073] The specific composition of the cement in this comparative example is shown in Table 6:

[0074] Table 6

[0075] Components weight Grade G oil well cement 80 Quartz sand 20

[0076] In this comparative example, quartz sand was used instead of quartz powder. The quartz sand had a SiO2 content of 95.4% and a fineness of 300 mesh.

[0077] Weigh each component according to the weight parts in Table 6 and mix them evenly to obtain cementing cement #6.

[0078] Comparative Example 2

[0079] The specific composition of the cement in this comparative example is shown in Table 7:

[0080] Table 7

[0081] Components weight Grade G oil well cement 65 Quartz sand 35

[0082] In this comparative example, quartz sand was used instead of quartz powder. The quartz sand had a SiO2 content of 95.4% and a fineness of 300 mesh.

[0083] Weigh each component according to the weight parts in Table 7 and mix them evenly to obtain cementing cement #7.

[0084] Comparative Example 3

[0085] The specific composition of the cement in this comparative example is shown in Table 8:

[0086] Table 8

[0087]

[0088] In this comparative example, quartz sand was used instead of quartz powder. The SiO2 content of the quartz sand was 95.4%, and the fineness was 300 mesh.

[0089] Weigh each component according to the weight parts in Table 8 and mix them evenly to obtain cementing cement #8.

[0090] Comparative Example 4

[0091] The specific composition of the cement in this comparative example is shown in Table 9:

[0092] Table 9

[0093] Components weight Grade G oil well cement 41 Quartz sand 20 Lattice distortion-induced materials 39

[0094] In this comparative example, quartz sand was used instead of quartz powder. The SiO2 content of the quartz sand was 95.4%, and the fineness was 300 mesh.

[0095] In this comparative example, the lattice distortion-inducing material has the same composition as in the above embodiments.

[0096] Weigh each component according to the weight parts in Table 9 and mix them evenly to obtain cementing cement #9.

[0097] Test case

[0098] The cementing cements prepared in Examples 1-5 and Comparative Examples 1-4 were used to prepare cement slurry according to the method specified in GB / T 19139, wherein the mixing water accounted for 44% of the cementing cement mass. The prepared cement slurry was poured into cement stone compressive strength test molds. The molds were cubes with a side length of 50 mm (or 2 in). After filling the molds and covering them with a cover plate, they were immediately placed in a pressure curing vessel. The vessel was closed, water was added, and the pressure was increased to 20.7 MPa. The temperature was raised to the curing temperature of 280°C after 4 hours. Heating was stopped 4 hours before the setting period. After the temperature inside the pressure curing vessel dropped below 100°C, cooling water was turned on. 45 minutes before the strength test, the pressure was slowly released and the molds were removed from the curing vessel. The molds were then immediately demolded and placed in a water bath at a temperature of 27°C ± 3°C for cooling. The compressive strength of the cement stone was tested on time. Cement stone slurry with dimensions of [missing information] was prepared using the same method. The samples were used to test permeability. Specific test results are shown in Table 10.

[0099] Table 10

[0100]

[0101] According to the data in Table 10, under the same water-cement ratio, the densities of the cement slurries prepared in Examples 1-5 and Comparative Examples 1-4 are not significantly different, but the compressive strength and permeability of the cement stone differ greatly. After adding lattice distortion inducing materials and steric hindrance materials to the cement slurry (Examples 1-5), the cement slurry exhibits high compressive strength after curing at 280℃, and the compressive strength shows good stability with prolonged curing time, while the permeability is low, effectively improving the quality of high-temperature cement sheathing. Without the addition of lattice distortion inducing materials and steric hindrance materials (Comparative Examples 1 and 2), the compressive strength of the cement stone significantly decreases after high-temperature curing, and the permeability increases significantly. Even by increasing the amount of quartz sand (Comparative Example 2), the compressive strength of the cement stone can be improved to some extent, but it cannot prevent the strength decay and the increase in permeability. When steric hindrance material is added alone (Comparative Example 3), the compressive strength of cement stone after high-temperature curing is significantly reduced; when lattice distortion inducing material is added alone (Comparative Example 4), cement stone has good compressive strength, but it still cannot change the trend of strength reduction, and the permeability value is large, which seriously affects the cementing quality.

[0102] Figure 3 The image shows the XRD diffraction pattern of ferrosilicon manganese slag. The pattern indicates that the diffraction curve of ferrosilicon manganese slag is a peak with no obvious diffraction peaks of crystalline minerals, indicating that the material is amorphous, has good pozzolanic activity, can quickly participate in the hydration reaction of cement paste, and optimize the structure and properties of cement stone hydration products.

[0103] The hydration products of the cement slurries prepared in Example 2 and Comparative Example 2, cured at 280°C for 14 days, were scanned using an electron microscope. Figure 1 and Figure 2 As shown. By Figure 2 It can be seen that after curing at 280℃, the hydration products of the sample in Comparative Example 2 underwent significant changes within the cement stone. The hydration products became fibrous, distributed in a flowering pattern, and exhibited a coarsened crystal structure. Figure 1 It can be seen that, under the same curing conditions, the hydration products of the sample in Example 2 are significantly finer, and the internal particles fill the pores of the cement stone, which effectively prevents the coarsening and growth of the hydration product fibers and helps to improve the strength of the cement stone.

[0104] In summary, this invention can improve the high-temperature mechanical properties of oil well cement stone and is suitable for deep and ultra-deep well operations.

[0105] 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 resistant cement for cementing deep and ultra-deep wells, characterized in that, Includes the following components by weight: 40-50 parts of cement for oil wells; 10-20 parts quartz powder; 30-45 parts of lattice distortion-inducing material; 0.3-1 part of steric hindrance material; The lattice distortion inducing material is a mixture of ferrosilicon slag and barite, with a weight ratio of ferrosilicon slag to barite of 4:

1. The ferrosilicon manganese slag has an amorphous structure, with a MnO content >5% and a powder particle size of 300-500 mesh; The barite contains BaSO4 content >90%, and the barite powder has a particle size of 800-1200 mesh. The steric hindrance material is one of nano-titanium dioxide, ultrafine calcium carbonate, and ultrafine graphite powder. The nano-titanium dioxide has a rutile structure and a specific surface area > 20 m². 2 / g; The particle size of the ultrafine calcium carbonate is >1200 mesh; The particle size of the ultrafine graphite powder is >1200 mesh.

2. The high-temperature resistant cement for cementing deep and ultra-deep wells according to claim 1, characterized in that, The oil well cement is one of three types: Grade G, Grade H, or Grade D.

3. The high-temperature resistant cement for cementing deep and ultra-deep wells according to claim 2, characterized in that, The quartz powder has a SiO2 content of >97% and a particle size of 300-500 mesh.

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