Cement paste system with high strength, elasticity and toughness and application of cement paste system in deep coal bed gas horizontal well cementation

Abstract

The invention provides a cement paste system with high strength, elasticity and toughness and application of the cement paste system in deep coal bed gas horizontal well cementation, and the cement paste system is prepared from the following raw materials in parts by mass: 40-70 parts of oil well cement, 13-40 parts of fly ash, 15-45 parts of slag, 5.0-20.0 parts of water-based organic silicon resin, 0.1-0.5 part of ultra-high performance polyethylene fiber, 3.0-8.0 parts of calcium oxide and 2.0-5.0 parts of calcium sulfate whisker. 1.0-8.0 parts of nano silicon dioxide, 1.0-6.0 parts of a fluid loss agent, 0.5-2.0 parts of a drag reducer, 0.2-1 part of a defoaming agent and 50-80 parts of water. The cement paste system disclosed by the invention has the characteristics of remarkable low-temperature quick setting and high early strength, also has the advantages of low water loss, controllable thickening, simple preparation operation and the like, and set cement is high in compressive strength, high in breaking strength and very excellent in elastic and tough mechanical properties.

Description

Technical Field

[0001] The present invention relates to the technical field of oil and gas well drilling and cementing, and particularly relates to a high-strength elastic and tough cement slurry system and its application in cementing deep coalbed methane horizontal wells. Background Technique

[0002] The coal reservoir of a coalbed methane well has low permeability and low pore pressure, and it is usually difficult to build production naturally. Fracturing operations are required, especially for deep coal seams. Large-scale volume fracturing is a key technical means to increase production. Cementing is an important link in the construction of coalbed methane wells, and its quality will affect the later fracturing and gas production operation effects as well as the life of the coalbed methane well.

[0003] Deep coal seams are characterized by low permeability, and generally the permeability decreases with the increase of burial depth. Since the coal seam fracture system does not have strong connectivity and the permeability is low, it is necessary to effectively transform the coal reservoir through large-scale volume fracturing technology, which is an important measure for the economic development of deep coalbed methane. However, due to the natural properties of cement stone itself, such as low compressive strength, high brittleness, and weak impact resistance, large-scale volume fracturing technology usually destroys the integrity of the cement sheath, resulting in the failure of wellbore integrity and seriously affecting the life and normal production of deep coalbed methane wells.

[0004] CN 112456873A discloses a cement slurry for cementing suitable for coalbed methane. This technology forms a plugging-type cement slurry system by adding multi-grade plugging materials and active fillers to the cement slurry. The multi-grade plugging materials bridge and are filled and bridged with cement particles at multiple levels to improve the compactness of the plugging structure. At the same time, the addition amounts of the modified multi-grade plugging materials and active fillers are adjusted, and their combined action has a significant synergistic effect on the plugging performance of the cement slurry. This cement slurry system has good compatibility with water, good fluidity, and excellent plugging performance. However, this technology does not consider the development of low-temperature strength, and the elastic toughness of the cement stone has not been further improved, and its application in deep coalbed methane cementing has certain limitations.

[0005] The existing cement slurry systems applied to deep coalbed methane wells have obvious deficiencies: they have not scientifically and reasonably designed the cement slurry formula according to the characteristics of deep coalbed methane reservoirs and the needs of large-scale fracturing, and have not strictly controlled the mechanical properties of the cement stone, especially the elastic and tough mechanical properties of the cement stone, to ensure that the cement sheath does not fail under hydraulic stress, or even under multiple alternating hydraulic stress loads, effectively guarantee the wellbore integrity of deep coalbed methane wells, and provide support for the safe, efficient, and economic exploitation of deep coalbed methane.

[0006] Different from the development of medium and shallow coalbed methane wells, deep coal seams are buried deeper, have lower permeability, and poorer connectivity of the coal seam fracture system. Therefore, large-scale volume fracturing technology is required to effectively transform the coal reservoir. At present, the conventional cement slurry for cementing coalbed methane wells can no longer effectively meet the requirements of large-scale fracturing in deep coal seams due to its low compressive strength and poor toughness of the cement stone. Therefore, it is very necessary to develop a cement slurry system suitable for cementing deep coalbed methane wells. Summary of the Invention

[0007] To solve the above technical problems, the purpose of the present invention is to provide a high-strength elastic and tough cement slurry system and its application in cementing horizontal wells of deep coalbed methane.

[0008] To achieve the above object, the present invention provides a high-strength elastic and tough cement slurry system. In terms of parts by mass, its raw materials include:

[0009]

[0010] According to the specific embodiment of the present invention, preferably, the mass fraction of the oil well cement is 50 parts.

[0011] The present invention aims at cementing deep coalbed methane and provides a cement slurry system suitable for cementing deep coalbed methane. Based on low-cost fly ash cement, the present invention innovatively utilizes the hydration synergistic effect and close packing effect of oil well cement, fly ash, slag, nano-silica and calcium oxide to solve the problems of slow low-temperature strength development and poor stability in the conventional cement slurry system, effectively improving the low-temperature quick setting and density of the cement slurry system, and helping to reduce the dosage of oil well cement. It can not only reduce the cost of the cement slurry, but also help to reduce carbon dioxide emissions. In addition, the present invention innovatively utilizes the toughening mechanics theory of different scales and mutual bonding and networking of ultra-high performance polyethylene fibers, calcium sulfate whiskers and water-based silicone resins to significantly improve the elasticity and toughness of the cement stone, reduce the elastic modulus, and effectively solve the problem of poor overall toughness of traditional cement stones, and can meet the requirements of large-scale fracturing in the current development of deep coalbed methane.

[0012] The cement slurry system of the present invention has good rheological properties, good thixotropy of the cement slurry, the density can be adjusted within the range of 1.60 - 1.90 g / cm 3 The water loss of the cement slurry body is controlled within 50 mL. The cement slurry system has properties such as low water loss, low-temperature quick setting, and high early strength. The cement stone has excellent mechanical properties such as high compressive strength, high flexural strength, and low elastic modulus, and can replace the existing cement slurry system for cementing operations in deep coalbed methane wells.

[0013] Through a large number of studies on the development of coalbed methane and the current application status of low-temperature early-strength cement slurries, the present invention specifically introduces ultra-high performance polyethylene fibers, waterborne silicone resins, and nano-silica. Among them, the waterborne silicone resin has the characteristics of both organic and inorganic materials, which can improve the wettability between the coal seam and the cement, enhance the interface sealing quality. At the same time, the waterborne silicone resin has good mechanical properties. During the curing process, it forms a network structure with high cross-linking density with fibers and whiskers, which can improve the mechanical properties of the cement stone, increase the early strength of the cement stone, make the cement stone have a high compressive strength, and at the same time have good toughness.

[0014] In addition, the present invention innovatively utilizes the synergistic effect of the hydration of oil well cement, fly ash, slag, nano-silica, and calcium oxide. First, under the synergistic hydration promotion of nano-silica and calcium oxide, the oil well cement continuously hydrates and generates a large amount of calcium hydroxide. Then, under the action of the nano-silica crystal nucleus and hydration induction, the calcium hydroxide generated by hydration continuously activates the reaction activity of slag and fly ash, causing them to react with the calcium hydroxide generated by hydration to form hydrated gels. The continuous consumption of calcium hydroxide will further promote the hydration of the oil well cement, generating a large amount of calcium hydroxide, which further activates the reaction between slag, fly ash, and calcium hydroxide. In this way, the oil well cement, slag, and fly ash will continuously undergo a hydration synergistic reaction, generating a large number of hydrated gels with different types, structures, and scales, forming a dense structure body, achieving low temperature and early strength. In addition, the oil well cement, fly ash, and slag can form an effective close packing effect with each other, improving the density of the cement stone, reducing the permeability of the cement stone, and enhancing the strength of the cement stone. Finally, the nano-silica particles can act as the aggregate of the silicone resin. The nano-silica particles fill the cracks and pore structures of the cement stone. Through the filling and curing bonding effect of the resin and nano-silica, the two synergistically enhance the structure of the cement stone to be more dense and the mechanical properties to be more excellent, further accelerating the development of early strength and improving the mechanical properties of the cement stone. At the same time, nano-silica can be used as an early-strength agent and stabilizer for the cement slurry, accelerating the hydration process of the oil well cement and achieving the effect of early strength and coagulation promotion.

[0015] The cement slurry system of the present invention can preferably solve the problems of low compressive strength and poor toughness of the existing conventional cement slurries in deep coalbed methane well cementing, which are difficult to meet the requirements of large-scale volume fracturing in deep coal seams. It has excellent properties of low water loss and high early strength in deep coalbed methane well cementing, and effectively improves the elastic and tough mechanical properties and density of the cement stone, effectively preventing the damage of large-scale volume fracturing to the cement sheath and preventing the occurrence of annulus pressure phenomena, providing technical support for the efficient development of deep coalbed methane.

[0016] According to the specific embodiments of the present invention, preferably, the density of the high-strength elastic and tough cement slurry system is 1.60 - 1.90 g / cm 3 。

[0017] According to a specific embodiment of the present invention, preferably, based on the weight of the oxide, the chemical composition of the fly ash includes: 45-48% SiO2, 31-35% Al2O3, 7-10% CaO, 2.5-3.2% Fe2O3, 1.2-1.8% K2O, 1.3-2.8% MgO.

[0018] According to a specific embodiment of the present invention, preferably, the particle size distribution range of the fly ash is 0.2-12.5 μm, and the median particle size (D 50 ) is 2-3 μm. The fine particle size of the fly ash can effectively fill the pores in the cement stone, reduce the porosity of the cement stone, make the cement stone form a dense structure, improve the compressive strength of the cement stone, and reduce the permeability of the cement stone.

[0019] According to a specific embodiment of the present invention, preferably, the specific surface area of the fly ash is 900-1000 m 2 / kg, and the density is 2.45-2.65 g / cm 3 .

[0020] In the fly ash preferably used in the present invention, the contents of the active components SiO2 and MgO are higher than those of ordinary fly ash, and the particle size is finer, having higher pozzolanic activity. It can undergo a pozzolanic reaction with the calcium hydroxide in the hydration products of the oil well cement to generate calcium silicate hydrate gel, thereby promoting the hydration of the oil well cement and further filling the pores to improve the strength of the oil well cement stone.

[0021] According to a specific embodiment of the present invention, preferably, based on the weight of the oxide, the chemical composition of the slag includes: 26-31% SiO2, 40-45% CaO, 13-15% Al2O3, 6.5-8.5% MgO, 0.3-0.5% K2O, 0.3-0.5% Na2O.

[0022] According to a specific embodiment of the present invention, preferably, the particle size distribution range of the slag is 0.5-30 μm, and the median particle size (D 50 ) is 12-15 μm.

[0023] According to a specific embodiment of the present invention, preferably, the specific surface area of the slag is 600-700 m 2 / kg, and the density is 2.75-2.85 g / cm 3 .

[0024] In the present invention, the contents of active components CaO and MgO in the slag are preferably higher than those in ordinary slag, and the particle size is finer, with higher alkalinity and reactivity. It can effectively promote the pozzolanic reaction of SiO2, Al2O3, etc. in fly ash and slag with calcium hydroxide, the hydration product of oil well cement, enabling the mutual synergistic hydration promotion of oil well cement, fly ash, and slag, generating more fine hydrated calcium silicate gels, and improving the strength and compactness of the oil well cement stone.

[0025] In the present invention, fly ash and slag, which are cementitious materials with low heat of hydration, are used as weight reducers for oil well cement-based materials to regulate the density of the coalbed methane cement slurry system, and enable the particle packing of the cement slurry system to form a more closely packed structure. It can effectively increase the compressive strength of the cement stone, especially the early compressive strength. At the same time, fly ash and slag particles can form a close packing with cement particles, improving the density and compressive strength of the cement stone, and can also serve as a skeleton support structure in the cement stone, replacing part of the oil well cement, reducing the cost of the cement slurry for well cementing, and reducing the carbon dioxide emissions during the well cementing operation.

[0026] According to a specific embodiment of the present invention, preferably, the water-based organosilicon resin is an oil-in-water type γ-aminopropyltriethoxysilane modified epoxy resin emulsion. More preferably, the average particle size of the oil-in-water type γ-aminopropyltriethoxysilane modified epoxy resin emulsion is 1.5 - 3.8 μm, and the solid content is 48 - 51%.

[0027] The water-based organosilicon resin used in the present invention can be evenly dispersed in water, crosslink and cure after dehydration, and has good mechanical properties and high crosslink density.

[0028] In the present invention, the water-based organosilicon resin has high crosslink density and excellent mechanical properties after curing, can improve the wettability between the coal seam and the cement, improve the interface sealing quality, reduce the water loss and volume shrinkage of the cement slurry, and can improve the mechanical properties of the cement stone, increase the early strength of the cement stone, and enable the cement stone to have high compressive strength while also having good toughness.

[0029] According to a specific embodiment of the present invention, preferably, the tensile strength of the polyethylene fiber is 2.5 - 3.0 GPa, the tensile modulus is 110 - 120 GPa, and the melting temperature is 140 - 155 °C.

[0030] According to a specific embodiment of the present invention, preferably, the density of the polyethylene fiber is 0.97 - 0.99 g / cm 3 , and the length is 4 - 6 mm.

[0031] The polyethylene fiber described in the present invention has a tensile strength and a tensile modulus that are 2 - 4 times higher than those of the polyethylene fiber in the current prior art, which is more conducive to improving the elasticity and toughness and impact resistance of the cement stone.

[0032] The present invention uses ultra-high performance polyethylene fibers that do not agglomerate and have good dispersibility in cement slurry as toughening materials for the cement slurry system to meet the on-site fracturing requirements. When the cement stone is subjected to impact force, the elastic-plastic toughening material particles play a buffering role, absorbing part of the energy and improving the impact resistance of the cement stone. The polyethylene fibers can form a dense network structure in the cement stone, shielding the stress field at the crack tip of the cement stone defects, thereby improving the fracture toughness of the cement stone and preventing the cement sheath from cracking and failing during the fracturing process. According to the specific embodiments of the present invention, preferably, the calcium sulfate whisker is a short-columnar α-calcium hemihydrate crystal, with an average length of 125-145 μm, a length-to-diameter ratio of 50-60, and a density of 2.68-2.72 g / cm 3 , and the Mohs hardness is 3-3.5.

[0033] The present invention combines CaO and calcium sulfate whiskers to improve the strength of the cement stone, and continues to react after the cement hydrates to cause volume expansion, acting as an expansion agent for the cement slurry system to inhibit the shrinkage of the cement stone and ensure the effective sealing of the cement sheath.

[0034] According to the specific embodiments of the present invention, preferably, the particle size of the nano-silica is 20-80 nm. The particle size of the nano-material matches the particle size distributions of oil well cement, fly ash, and slag, realizing the close packing of solid-phase particles, improving the compressive strength and compactness of the cement stone, reducing the permeability of the cement stone, and enhancing the anti-channeling ability of the cement stone.

[0035] According to the specific embodiments of the present invention, preferably, the nano-silica is nano-silica powder and / or nano-silica aqueous solution. Among them, the nano-silica aqueous solution is a transparent to slightly milky white liquid, with a density between 1.19-1.22 g / cm 3 , a particle size between 50-60 nm, and a silica mass content of 35%; the nano-silica powder is an amorphous white solid fluffy powder, with a density between 0.50-1.50 g / cm 3 , a particle size between 20-80 nm, a silica mass content ≥90%, and the particles are spherical.

[0036] In the present invention, nano-silica can be used as an early strength agent and thixotropic agent for the cement slurry system, accelerating the early strength development of the cement stone in low-temperature coal seams and having good thixotropic properties, ensuring the displacement efficiency during the pumping process of the cement slurry and preventing the formation from being fractured, and the viscosity rapidly increases after the pumping is completed, which can reduce the downward transmission of the static liquid column pressure of the cement slurry, effectively preventing the leakage of the cement slurry and annular gas channeling in the cementing of deep coalbed methane. At the same time, the filling and curing bonding effect of the water-based silicone resin and nano-silica further improves the mechanical properties of the resin, and the synergistic effect of the two makes the cement stone more compact, improving the internal pore structure and mechanical properties of the cement stone.

[0037] According to a specific embodiment of the present invention, preferably, the well cement includes one or a combination of two or more of API well G-class cement, well A-class cement, and well C-class cement.

[0038] According to a specific embodiment of the present invention, preferably, the fluid loss reducer includes one or a combination of two or more of 2-acrylamido-2-methylpropanesulfonic acid (AMPS)-acrylamide (AM)-N,N-dimethylacrylamide (DMAA) copolymer, 2-acrylamido-2-methylpropanesulfonic acid (AMPS)-acrylic acid (AA)-N,N-dimethylacrylamide (DMAA) copolymer, 2-acrylamido-2-methylpropanesulfonic acid (AMPS)-itaconic acid (IA)-N,N-dimethylacrylamide (DMAA) copolymer, 2-acrylamido-2-methylpropanesulfonic acid (AMPS)-acrylamide (AM)-acrylic acid (AA)-N,N-dimethylacrylamide (DMAA) copolymer, and 2-acrylamido-2-methylpropanesulfonic acid (AMPS)-acrylamide (AM)-itaconic acid (IA)-N,N-dimethylacrylamide (DMAA) copolymer.

[0039] According to a specific embodiment of the present invention, preferably, the drag reducer includes a sulfonated formaldehyde-acetone condensate drag reducer and / or a polynaphthalenesulfonate drag reducer.

[0040] According to a specific embodiment of the present invention, preferably, the defoamer includes one or a combination of two or more of silicone ether copolymer defoamers, organosiloxane defoamers, and polyether defoamers.

[0041] According to a specific embodiment of the present invention, preferably, the water is at least one of fresh water, seawater, and mineralized water.

[0042] The method for preparing the high-strength elastic and tough cement slurry system of the present invention into a slurry is as follows: Weigh and mix the dry ash components and liquid water components for preparing the slurry, and then prepare the slurry according to the standard GB / T 19139-2012 "Test Methods for Well Cement".

[0043] The present invention also provides an application of the above high-strength elastic and tough cement slurry system in cementing deep coalbed methane horizontal wells.

[0044] The cement slurry system of the present invention has excellent properties such as low-temperature quick setting, low water loss, and high early strength, significantly improves the elastic and tough mechanical properties and density of the cement stone, can effectively prevent the occurrence of cement sheath damage and cement sheath annulus pressure, and all indicators meet the requirements of on-site cementing, providing technical support for deep coalbed methane cementing.

[0045] The technical solution provided by the present invention has the following beneficial effects:

[0046] The cement slurry system of the present invention is a cement slurry system applicable to the cementing of deep coalbed methane wells. This cement slurry system has the remarkable characteristics of rapid setting at low temperature and high early strength. In addition, it also has advantages such as low water loss, controllable thickening, and simple preparation operation. The cement stone has high compressive strength, high flexural strength, and very excellent elastic and ductile mechanical properties, and all performance indicators can meet the requirements of on-site cementing. Specific Embodiments

[0047] For a clearer understanding of the technical features, objectives, and beneficial effects of the present invention, the technical solutions of the present invention will be described in detail below, but it should not be construed as a limitation on the scope of implementation of the present invention.

[0048] The sources and models of the raw materials used in the embodiments of the present invention are specifically as follows:

[0049] Class G oil well cement: Purchased from Jiahua Special Cement Co., Ltd.

[0050] Water-based silicone resin: An oil-in-water type γ-aminopropyltriethoxysilane modified epoxy resin emulsion with an average particle size of 1.5 - 3.8 μm and a solid content of 48 - 51%. Purchased from Hubei Longsheng Sihai New Materials Co., Ltd., and the product model is SH-9607. It is a high-performance transparent emulsion for cement concrete, which dehydrates and crosslinks and cures, and can generate an insoluble polymer network silicone resin film on the surface and inside of the structure, with excellent durability and mechanical properties.

[0051] Fly ash: From Shandong Shiheng Power Plant, the main chemical components and weight component contents are 47.5% SiO2, 32% Al2O3, 9.6% CaO, 2.6% Fe2O3, 1.6% K2O, 1.7% MgO. The particle size distribution range is 0.2 - 12.5 μm, the median particle size D 50 = 2.3 μm, the specific surface area is 960 m 2 / kg, and the density is 2.62 g / cm 3 .

[0052] Slag: From Beijing Shougang, the main chemical components and weight component contents are 29.3% SiO2, 43.6% CaO, 14.1% Al2O3, 6.9% MgO, 0.35% K2O, 0.32% Na2O. The particle size distribution range is 0.5 - 30 μm, the median particle size D 50 = 13.7 μm, the specific surface area is 670 m 2 / kg, and the density is 2.78 g / cm 3 .

[0053] Ultra-high performance polyethylene fiber: Purchased from Beijing Weiya High Performance Fiber Co., Ltd., model 1600D, length 6mm, tensile strength 3.0GPa, tensile modulus 120GPa.

[0054] Calcium sulfate whisker; Purchased from Shanghai Guangyan Chemical Technology Co., Ltd., model LL-1946, short columnar α-calcium sulfate hemihydrate crystals, average length 135μm, aspect ratio 50, density 2.70g / cm 3 , Mohs hardness 3.3.

[0055] Nano-silica: Purchased from Shandong Baite New Materials Co., Ltd., is a transparent to slightly milky white liquid, density between 1.19 - 1.22g / cm3, particle size between 50 - 60nm, silica mass content 35%.

[0056] Fluid loss reducer: Purchased from Chengdu Omek Petroleum Technology Co., Ltd., model HX-12, is a 2-acrylamido-2-methylpropanesulfonic acid (AMPS) multi-component copolymer polymer.

[0057] Drag reducer: Purchased from Henan Weihui Chemical Co., Ltd., model USZ, is a sulfonated formaldehyde-acetone condensate drag reducer.

[0058] Defoamer: Purchased from Chengdu Omek Petroleum Technology Co., Ltd., model DF-E, is a polyether-polysiloxane composite defoamer.

[0059] The present invention will be specifically described below in conjunction with the embodiments.

[0060] Example 1

[0061] This example provides a high-strength elastic and tough cement slurry system, which is prepared from the following raw material components in parts by mass: 62.0 parts of oil well cement; 23.0 parts of slag; 15.0 parts of fly ash; 0.2 parts of ultra-high performance polyethylene fiber; 3.0 parts of calcium oxide; 3.0 parts of calcium sulfate whisker; 5.0 parts of waterborne silicone resin; 2.0 parts of nano-silica; 3.5 parts of fluid loss reducer; 0.6 parts of drag reducer; 0.5 parts of defoamer; 50 parts of water.

[0062] Example 2

[0063] This example provides a high-strength elastic and tough cement slurry system, which is prepared from the following raw material components in parts by mass: 58.0 parts of oil well cement; 27.0 parts of slag; 15.0 parts of fly ash; 0.3 parts of ultra-high performance polyethylene fiber; 4.0 parts of calcium oxide; 4.0 parts of calcium sulfate whisker; 6.0 parts of waterborne silicone resin; 2.0 parts of nano-silica; 3.5 parts of fluid loss reducer; 0.6 parts of drag reducer; 0.5 parts of defoamer; 50 parts of water.

[0064] Example 3

[0065] This embodiment provides a high-strength, elastic and tough cement slurry system, which is prepared from the following raw material components in parts by mass: 55 parts of oil well cement; 25.0 parts of slag; 20.0 parts of fly ash; 0.4 part of ultra-high performance polyethylene fiber; 5.0 parts of calcium oxide; 5.0 parts of calcium sulfate whisker; 9.0 parts of waterborne silicone resin; 2.0 parts of nano-silica; 2.5 parts of fluid loss reducer; 0.6 part of friction reducer; 0.5 part of defoamer; 50 parts of water.

[0066] Example 4

[0067] This embodiment provides a high-strength, elastic and tough cement slurry system, which is prepared from the following raw material components in parts by mass: 50.0 parts of oil well cement; 28.0 parts of slag; 22.0 parts of fly ash; 0.2 part of ultra-high performance polyethylene fiber; 4.0 parts of calcium oxide; 4.5 parts of calcium sulfate whisker; 5.0 parts of waterborne silicone resin; 2.0 parts of nano-silica; 4.5 parts of fluid loss reducer; 0.6 part of friction reducer; 0.5 part of defoamer; 50 parts of water.

[0068] Example 5

[0069] This embodiment provides a high-strength, elastic and tough cement slurry system, which is prepared from the following raw material components in parts by mass: 50.0 parts of oil well cement; 25.0 parts of slag; 25.0 parts of fly ash; 0.25 part of ultra-high performance polyethylene fiber; 3.0 parts of calcium oxide; 4.0 parts of calcium sulfate whisker; 5.0 parts of waterborne silicone resin; 2.0 parts of nano-silica; 4.5 parts of fluid loss reducer; 0.6 part of friction reducer; 0.5 part of defoamer; 51 parts of water.

[0070] Example 6

[0071] This embodiment provides a high-strength, elastic and tough cement slurry system, which is prepared from the following raw material components in parts by mass: 47.0 parts of oil well cement; 35.0 parts of slag; 18.0 parts of fly ash; 0.25 part of ultra-high performance polyethylene fiber; 6.0 parts of calcium oxide; 3.5 parts of calcium sulfate whisker; 5.0 parts of waterborne silicone resin; 2.0 parts of nano-silica; 4.0 parts of fluid loss reducer; 0.6 part of friction reducer; 0.5 part of defoamer; 52 parts of water.

[0072] Example 7

[0073] This embodiment provides a high-strength, elastic and tough cement slurry system, which is prepared from the following raw material components in parts by mass: 42.0 parts of oil well cement; 30.0 parts of slag; 28.0 parts of fly ash; 0.35 part of ultra-high performance polyethylene fiber; 8.0 parts of calcium oxide; 5.0 parts of calcium sulfate whisker; 15.0 parts of waterborne silicone resin; 7.0 parts of nano-silica; 4.5 parts of fluid loss reducer; 1.2 parts of friction reducer; 0.5 part of defoamer; 55 parts of water.

[0074] Comparative Example 1

[0075] This comparative example provides a cement slurry system, which is prepared from the following raw material components in parts by mass: 100 parts of oil well cement and 44 parts of water.

[0076] Comparative Example 2

[0077] This comparative example provides a cement slurry system, which is the same as Example 1, except that the cement slurry system does not add ultra-high performance polyethylene fibers and calcium sulfate whiskers.

[0078] Comparative Example 3

[0079] This comparative example provides a cement slurry system, which is the same as Example 1, except that the cement slurry system does not add waterborne silicone resin and nano-silica.

[0080] Comparative Example 4

[0081] This comparative example provides a cement slurry system, which is prepared from the following raw material components in parts by mass: 100 parts of oil well cement; 1.5 parts of fluid loss reducer; 0.6 part of dispersant; 2.5 parts of gas channeling prevention agent; 0.1 part of retarder; 0.2 part of defoamer; 44 parts of water.

[0082] Test Example 1: Testing of the slurry properties of the high-strength elastic and tough cement slurry system

[0083] Taking the cement slurry systems of Examples 1-7 as the test objects, first weigh and mix the dry ash components and liquid water components for preparing the slurry, and then prepare the slurry according to the standard GB / T 19139-2012 "Test Methods for Oil Well Cement", and test the properties of the well cementing slurry system with reference to the standard SY / T 6544-2017 "Performance Requirements for Oil Well Cement Slurry".

[0084] The test results are shown in Table 1.

[0085] Table 1 Slurry properties of the cement slurry system

[0086]

[0087] It can be seen from Table 1 that the fluid loss of the cement slurry systems prepared in Examples 1-3 of the present invention for deep coalbed methane is less than 50 mL. With the increase of the addition amounts of ultra-high performance polyethylene fibers and waterborne silicone, the fluid loss continuously decreases, showing the characteristic of low fluid loss. The fluid loss of the well cementing slurry systems for deep coalbed methane prepared in Examples 1-7 of the present invention is controlled within 50 mL, having relatively stable density and good rheological properties, basically no free liquid, and the thickening time can meet the relevant requirements of on-site well cementing construction.

[0088] Test Example 2: Testing of the mechanical properties of the cement stone of the cement slurry system

[0089] Taking the cement slurry systems of Examples 1 - 7, Example 7 and Comparative Examples 1 - 4 as the test objects, first weigh and mix the solid dry ash component and the liquid water component of the prepared slurry system respectively, and then prepare the slurry according to the standard GB / T 19139 - 2012 "Test Methods for Oil Well Cement". After curing for 24 h and 48 h under different temperature conditions respectively, measure the compressive strength, flexural strength and elastic modulus. The results are shown in Tables 2, 3 and 4.

[0090] Table 2 Compressive Strength Performance of Cement Slurry System

[0091]

[0092] Table 3 Elastic Modulus Performance of Cement Slurry System

[0093]

[0094] Table 4 Flexural Strength Performance of Cement Slurry System

[0095]

[0096]

[0097] From the test results shown in Tables 2, 3 and 4, it can be seen that the cement slurry systems prepared in Examples 1 - 7 of the present invention meet the requirements of the cementing strength of SY / T 6544 - 2017 "Performance Requirements for Oil Well Cement Slurry" when cured for 24 hours and 48 hours under different temperature conditions. Comparing the compressive strength, flexural strength and elastic modulus of Examples 1 - 3 under various temperature conditions, it can be known that under the same temperature and pressure conditions, the higher the dosage of ultra - high performance polyethylene fiber and water - based silicone resin, the higher the early strength of the cement stone, the lower the elastic modulus, the greater the flexural strength, and the more excellent the mechanical properties of the cement stone.

[0098] And comparing with the compressive strength, flexural strength and elastic modulus of Comparative Examples 1 - 4, it can be known that the elastic modulus of the cement slurry system applicable to coalbed methane prepared in Examples 1 - 7 of the present invention is less than 6 GPa. Examples 1 - 7 can not only effectively improve the compressive strength and flexural strength of the oil well cement stone, but also significantly reduce the elastic modulus, thereby improving the mechanical properties of the cement sheath, enhancing the sealing performance and impact toughness of the cement sheath. Its performance is significantly better than the cement slurry system for deep coalbed methane horizontal well cementing before optimization (Comparative Example 4) and can meet the requirements of on - site fracturing construction.

[0099] Test Example 3: Testing of Cement Stone Permeability and Porosity of Cement Slurry System

[0100] Taking the examples 1-3 and comparative examples 1-4 as the test objects, first weigh and mix the solid dry ash components and liquid water components of the prepared slurry cement slurry system, and then prepare the slurry according to the standard GB / T 19139-2012 "Test Methods for Oil Well Cement". Referring to the standard GB / T 19139-2012 "Test Methods for Oil Well Cement", after curing the cement at 50 °C for 24 h, test the relative permeability and porosity of the liquid to the cement stone sample. The test results are shown in Table 5.

[0101] Table 5 Permeability Performance of Different Cement Slurry Systems

[0102]

[0103]

[0104] It can be seen from the data in Table 5 that the permeability and porosity of Examples 1-3 are significantly lower than those of Comparative Examples 1-4. This shows that the cement slurry system for deep coalbed methane well cementing of the present invention can effectively improve the pore structure inside the cement stone, making the cement stone structure more dense.

[0105] The well cementing slurry system of the present invention has been applied to the well cementing of more than 10 deep coalbed methane horizontal wells in a certain county in 2023, and the excellent well cementing rate reaches over 92.6%. After large-scale volume segmented fracturing of the deep coalbed methane wells, there is no pressure in the annulus. This fully shows that the deep coalbed methane well cementing slurry system of the present invention has the characteristics of high compressive strength, high flexural strength, low elastic modulus, and strong impact resistance, can effectively improve the well cementing quality of deep coalbed methane horizontal wells, and can meet the requirements of on-site fracturing construction.

Claims

1. A high-strength, elastic and tough cement slurry system, by mass fraction, its raw materials include:

2. The high-strength and elastic ductile cement slurry system according to claim 1, wherein, The density of the high-strength elastic and tough cement slurry system is 1.60 - 1.90 g / cm 3 .

3. The high-strength and elastic ductile cement slurry system according to claim 1, wherein By weight of the oxides, the chemical composition of the fly ash includes: 45-48% SiO2, 31-35% Al2O3, 7-10% CaO, 2.5-3.2% Fe2O3, 1.2-1.8% K2O, 1.3-2.8% MgO.

4. The high-strength and elastic ductile cement slurry system according to claim 2, wherein, The particle size distribution range of the fly ash is 0.2-12.5 μm, and the median particle size is 2-3 μm; Preferably, the specific surface area of the fly ash is 900 - 1000 m 2 / kg, and the density is 2.45 - 2.65 g / cm 3 .

5. The high-strength elastic and tough cement slurry system according to claim 1, wherein, By weight of the oxides, the chemical composition of the slag includes: 26-31% SiO2, 40-45% CaO, 13-15% Al2O3, 6.5-8.5% MgO, 0.3-0.5% K2O, 0.3-0.5% Na2O.

6. The high-strength and elastic ductile cement slurry system according to claim 5, wherein The particle size distribution range of the slag is 0.5-30 μm, and the median particle size is 12-15 μm; Preferably, the specific surface area of the slag is 600-700m 2 / kg, and the density is 2.75-2.85g / cm 3 .

7. The high-strength and elastic toughness cement slurry system according to claim 1, wherein, The water-based organosilicon resin is an oil-in-water type γ-aminopropyltriethoxysilane modified epoxy resin emulsion; Preferably, the average particle size of the oil-in-water type γ-aminopropyltriethoxysilane modified epoxy resin emulsion is 1.5-3.8 μm, and the solid content is 48-51%.

8. The high-strength and elastic ductile cement slurry system according to claim 1, wherein, The tensile strength of the polyethylene fiber is 2.5-3.0 GPa, the tensile modulus is 110-120 GPa, and the melting temperature is 140-155 °C; Preferably, the density of the polyethylene fiber is 0.97 - 0.99 g / cm 3 , and the length is 4 - 6 mm.

9. The high-strength and elastic ductile cement slurry system according to claim 1, wherein, The calcium sulfate whisker is a short columnar α-calcium sulfate hemihydrate crystal, with an average length of 125-145 μm, an aspect ratio of 50-60, and a density of 2.68-2.72 g / cm 3 , and the Mohs hardness is 3-3.

5.

10. The high-strength and elastic-brittle cement slurry system according to claim 1, wherein, The particle size of the nano-silica is 20-80 nm.

11. The high-strength and elastic ductility cement slurry system according to claim 1, wherein, The oil well cement includes one or a combination of two or more of API oil well G-class cement, oil well A-class cement, and oil well C-class cement.

12. The high-strength and elastic ductility cement slurry system according to claim 1, wherein, The fluid loss reducer includes one or a combination of two or more of 2-acrylamido-2-methylpropanesulfonic acid-acrylamide-N,N-dimethylacrylamide copolymer, 2-acrylamido-2-methylpropanesulfonic acid-acrylic acid-N,N-dimethylacrylamide copolymer, 2-acrylamido-2-methylpropanesulfonic acid-itaconic acid-N,N-dimethylacrylamide copolymer, 2-acrylamido-2-methylpropanesulfonic acid-acrylamide-acrylic acid-N,N-dimethylacrylamide copolymer, 2-acrylamido-2-methylpropanesulfonic acid-acrylamide-itaconic acid-N,N-dimethylacrylamide copolymer.

13. The high-strength and elastic ductility cement slurry system according to claim 1, wherein, The drag reducer includes a sulfonated formaldehyde-acetone condensate drag reducer and / or a polynaphthalenesulfonate drag reducer.

14. The high-strength and elastic ductility cement slurry system according to claim 1, wherein, The defoamer includes one or a combination of two or more of silicone ether copolymer defoamers, organosiloxane defoamers, and polyether defoamers; Preferably, the water is at least one of fresh water, sea water, and mineralized water.

15. Application of the high-strength, elastic and tough cement slurry system according to any one of claims 1-14 in cementing of deep coalbed methane horizontal wells.

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