A low thermal conductivity cementing slurry system and a preparation method thereof

Abstract

The application provides a low-thermal-conductivity cementing slurry system and a preparation method thereof. The low-thermal-conductivity cementing slurry system comprises the following components in parts by weight: 100 parts of oil well cement, 0-125 parts of a density regulator, 2-20 parts of a low-thermal-conductivity material, 5-35 parts of a reinforcing material, 0-5 parts of an early strength agent, 1-3 parts of a suspending agent, 0-10 parts of an elastic material, 0-6 parts of a channeling-preventing toughening material, 0.5-1.5 parts of a dispersing agent, 1.5-6 parts of a fluid loss additive, 0-2 parts of a retarding agent, 0.2-0.5 parts of a defoaming agent and 44-110 parts of water. The preparation method of the low-thermal-conductivity cementing slurry system comprises the following steps: dry mixing and wet mixing the components respectively, mixing the dry mixed material with the wet mixed material, and obtaining the low-thermal-conductivity cementing slurry system. The low-thermal-conductivity cementing slurry system has a low thermal conductivity, and the thickening time and the flowability of the cementing slurry system are adjustable, so the application range is wide.

Description

Technical Field

[0001] This invention relates to a low thermal conductivity cementing slurry system and its preparation method, belonging to the field of cementing technology. Background Technology

[0002] With the continuous advancement of oil and gas and geothermal resource exploration and development technologies, the long-term safe and efficient production of oil and gas wells and geothermal wells places higher demands on wellbore integrity, among which cement sheath seal integrity is the core of wellbore integrity. Cement sheath seal integrity is generally reflected macroscopically through cementing quality and wellhead annular pressure conditions, and is a key manifestation of cementing technology ensuring good interlayer sealing.

[0003] Because well cementing is a one-time, concealed project, it requires comprehensive technical considerations from multiple disciplines, including materials science, mechanics, thermodynamics, and chemistry. Currently, with the continuous advancement of cementing technologies such as cementing additives, cement slurry systems, cementing tools, and cementing processes, cementing quality and prevention of annular pressure have been significantly improved to a certain extent. However, for deep and ultra-deep well cementing, it remains a technology that is "methodical but not guaranteed," because although cementing additives, cement slurry systems, cementing tools, and cementing processes are relatively mature, there are still problems where cementing technology cannot be matched with geological and engineering conditions. Currently, the problems of wellhead gas leakage and annular pressure in high-temperature, high-pressure natural gas wells and deep shale gas wells are becoming increasingly prominent during development, with poor casing-cement interface bonding quality and micro-annular gaps being the main causes. Geothermal wells using conventional cement cementing suffer from high thermal conductivity cement, poor insulation, and significant losses when geothermal energy is transported to the surface. Therefore, there is an urgent need to develop a low-thermal-conductivity cement slurry system to solve these cementing problems in the exploration, development, and production processes. Summary of the Invention

[0004] To address the aforementioned technical problems, the present invention aims to provide a low thermal conductivity cementing slurry system and its preparation method. By adding a low thermal conductivity material to the cementing slurry system, the present invention can reduce the thermal conductivity of the cementing slurry system. Furthermore, the low thermal conductivity cementing slurry system of the present invention exhibits strong adjustability in thickening time and fluidity, and has a wide range of applications.

[0005] To achieve the above objectives, the first aspect of the present invention provides a low thermal conductivity cementing slurry system, which, by weight, comprises the following components: 100 parts oil well cement, 0-125 parts density regulator, 2-20 parts low thermal conductivity material, 5-35 parts reinforcing material, 0-5 parts early strength agent, 1-3 parts suspending agent, 0-10 parts elastic material, 0-6 parts anti-channeling and toughening material, 0.5-1.5 parts dispersant, 1.5-6 parts fluid loss reducing agent, 0-2 parts retarder, 0.2-0.5 parts defoamer, and 44-110 parts water.

[0006] According to a specific embodiment of the present invention, preferably, the low thermal conductivity cementing slurry system comprises, by weight, the following components: 100 parts oil well cement, 2-20 parts low thermal conductivity material, 5-20 parts reinforcing material, 1-3 parts suspending agent, 0-10 parts elastic material, 0.5-1.5 parts dispersant, 1.5-6 parts fluid loss reducing agent, 0.2-0.5 parts defoamer, and 44-110 parts water. More preferably, the low thermal conductivity cementing slurry system comprises, by weight, the following components: 100 parts oil well cement, 2-10 parts low thermal conductivity material, 5-10 parts reinforcing material, 1-3 parts suspending agent, 0.5-1.5 parts dispersant, 3-6 parts fluid loss reducing agent, 0.2-0.5 parts defoamer, and 44-110 parts water.

[0007] According to a specific embodiment of the present invention, preferably, the low thermal conductivity cement slurry system comprises the following components by weight: 100 parts oil well cement, 10-125 parts density regulator, 2-13 parts low thermal conductivity material, 5-20 parts reinforcing material, 2-4 parts early strength agent, 1-3 parts suspending agent, 0-10 parts elastic material, 2-4 parts anti-channeling and toughening material, 0.5-1.5 parts dispersant, 1.5-6 parts fluid loss reducing agent, 0.2-2 parts retarder, 0.2-0.5 parts defoamer, and 44-110 parts water. More preferably, the low thermal conductivity cement slurry system comprises, by weight, the following components: 100 parts oil well cement, 10-80 parts density regulator, 5-13 parts low thermal conductivity material, 5-15 parts reinforcing material, 2-4 parts early strength agent, 1-3 parts suspending agent, 2-4 parts anti-channeling and toughening material, 0.5-1.5 parts dispersant, 3-6 parts fluid loss reducing agent, 0.2-1 part retarder, 0.2-0.5 parts defoamer, and 44-110 parts water.

[0008] In the aforementioned low thermal conductivity cementing slurry system, preferably, the low thermal conductivity material comprises a combination of three or more of the following: hollow glass microspheres, cenospheres, plastic particles, porous ceramic powder, and diatomaceous earth. More preferably, the low thermal conductivity material comprises a mixture of hollow glass microspheres, porous ceramic powder, and diatomaceous earth in a mass ratio of (1.5-2.5):(0.5-1.5):(0.5-1.5) (preferably 2:1:1). Particularly preferably, the hollow glass microspheres have a density of 0.44-0.65 g / cm³. 3 The average particle size is 10-200 μm. Particularly preferred is that the density of the cenospheres is 0.8-1.1 g / cm³. 3 The average particle size is 20-250 μm. More preferably, the plastic particles comprise polypropylene (PP) plastic particles with a particle size of 0.5-2 mm. More preferably, the porous ceramic powder has a particle size of 10-300 μm and a porosity of 40%-80%. More preferably, the diatomaceous earth has a particle size of 150-250 mesh.

[0009] In the aforementioned low thermal conductivity cementing slurry system, preferably, the density adjuster includes a weighting agent and / or a weighting agent. More preferably, the weighting agent includes hollow glass microspheres; particularly preferably, the density of the hollow glass microspheres is 0.44-0.65 g / cm³. 3 The average particle size is 10-200 μm. More preferably, the weighting agent comprises refined iron ore powder; particularly preferably, the density of the refined iron ore powder is 5.05-7.20 g / cm³. 3 The average particle size is 100-200 mesh.

[0010] In the aforementioned low thermal conductivity cementing slurry system, preferably, the reinforcing material comprises one or a combination of several of SiC whiskers, halloysite, and mullite. More preferably, the reinforcing material comprises a mixture of SiC whiskers, halloysite, and mullite in a mass ratio of (2.5-3.5):(0.5-1.5):(0.5-1.5) (preferably 3:1:1).

[0011] In the aforementioned low thermal conductivity cementing slurry system, preferably, the early-strength agent includes one or a combination of several of chloride-based, sulfate-based, nitrate-based, nitrite-based, aluminate-based, and silicate-based early-strength agents. More preferably, the early-strength agent includes a combination of four or more of sodium sulfate, sodium thiosulfate, sodium aluminate, calcium chloride, sodium silicate, and basic aluminum chloride. Particularly preferably, the early-strength agent includes a mixture of sodium sulfate, sodium thiosulfate, sodium aluminate, and calcium chloride in a mass ratio of (0.5-1.5):(0.5-1.5):(0.5-1.5):(0.5-1.5) (preferably 1:1:1:1).

[0012] In the aforementioned low thermal conductivity cementing slurry system, preferably, the suspending agent comprises a combination of three or more of xanthan gum, styrax, polyvinyl alcohol, and sodium bentonite. More preferably, the suspending agent comprises a mixture of xanthan gum, styrax, polyvinyl alcohol, and sodium bentonite in a mass ratio of (0.5-1.5):(0.5-1.5):(0.5-1.5):(1.5-2.5) (preferably 1:1:1:2).

[0013] In the aforementioned low thermal conductivity cementing slurry system, preferably, the elastic material includes rubber-based elastic materials, such as, but not limited to, DRE-1S rubber-based elastic material produced by CNPC Engineering Technology Research Institute Co., Ltd.

[0014] In the aforementioned low thermal conductivity cementing slurry system, preferably, the anti-channeling and toughening material includes polymer-based anti-channeling and toughening materials, such as, but not limited to, the polymer-based anti-channeling and toughening material DRT-1S produced by CNPC Engineering Technology Research Institute Co., Ltd.

[0015] In the aforementioned low thermal conductivity cementing slurry system, preferably, the dispersant includes aldehyde-ketone condensate dispersants and / or polystyrene sulfonate dispersants. More preferably, the aldehyde-ketone condensate dispersant may include one or a combination of several of dispersants such as DRS-1S, SAF, SXY, USZ, and SDJZ-1. More preferably, the polystyrene sulfonate dispersant may include sodium polystyrene sulfonate. Particularly preferably, the dispersant includes DRS-1S produced by CNPC Engineering Technology Research Institute Co., Ltd.

[0016] In the aforementioned low thermal conductivity cementing slurry system, preferably, the fluid loss reducing agent includes acrylamide polymer fluid loss reducing agents, etc. More preferably, the fluid loss reducing agent includes one or a combination of several of the following: DRF-1S, DRF-1L, DRF-2L, PC-G83L, PC-G80L, and LX-1. Particularly preferably, the fluid loss reducing agent includes DRF-1S, a solid acrylamide polymer fluid loss reducing agent, and / or DRF-2L, a liquid acrylamide polymer fluid loss reducing agent, produced by CNPC Engineering Technology Research Institute Co., Ltd.

[0017] In the aforementioned low thermal conductivity cementing slurry system, preferably, the retarder includes one or a combination of several selected from organic acid retarders, acrylamide polymer retarders, and 2-acrylamide-2-methylpropanesulfonic acid polymer retarders. More preferably, the retarder includes one or a combination of several selected from retarder DRH-1L, retarder DRH-2L, retarder JXH-2L, and retarder HX-36L. Particularly preferably, the retarder includes organic acid retarder DRH-1L and / or acrylamide polymer retarder DRH-2L produced by CNPC Engineering Technology Research Institute Co., Ltd.

[0018] In the aforementioned low thermal conductivity cementing slurry system, preferably, the defoamer comprises one or a combination of several of organic ester compounds, polyoxypropylene glycerol ethers, and polydimethylsiloxane. More preferably, the defoamer is polydimethylsiloxane.

[0019] In the aforementioned low thermal conductivity cementing slurry system, preferably, the oil well cement includes Grade G oil well cement. For example, one or a combination of several of the following: Jiahua Grade G, Huayou Grade G, Shengwei Grade G, and Mengcheng Grade G.

[0020] According to a specific embodiment of the present invention, preferably, the density of the low thermal conductivity cementing slurry system is 1.25-2.50 g / cm³. 3The applicable circulating temperature for oil wells is 60-150℃.

[0021] According to a specific embodiment of the present invention, preferably, the thermal conductivity of the low thermal conductivity cement slurry system is 0.18-0.42 W / mK.

[0022] On the other hand, the present invention also provides a method for preparing the above-mentioned low thermal conductivity cementing slurry system, which includes the following steps:

[0023] (1) According to the weight parts of each component mentioned above, the oil well cement, density regulator, low thermal conductivity material, reinforcing material, early strength agent, suspending agent, elastic material, anti-channeling toughening material and dispersant are mixed evenly. When the water loss reducing agent used is solid, it is mixed evenly with other components in this step to obtain dry mixture.

[0024] (2) According to the weight parts of each component mentioned above, mix the retarder, defoamer and water evenly, and when the water loss reducing agent used is liquid, mix it evenly with other components in this step to obtain a wet mixture;

[0025] (3) Mix the dry mixture and the wet mixture evenly to obtain the low thermal conductivity cement slurry system.

[0026] In the above preparation method, those skilled in the art should understand that when the low thermal conductivity cementing slurry system of the present invention does not include one or more of the above components, then in steps (1) and (2), this or these components need not be added.

[0027] In the above preparation method, preferably, the mixing in step (1) is carried out under stirring, and the stirring speed is 100-150 r / min.

[0028] In the above preparation method, preferably, the mixing in step (2) is carried out under stirring, and the stirring speed is 1000-1200 r / min.

[0029] In the above preparation method, preferably, step (3) is as follows: at a stirring speed of 4000±200r / min, the dry mixture is added to the wet mixture, and after the dry mixture is completely wetted, stirring is continued for 30-50s to obtain the low thermal conductivity cementing slurry system.

[0030] The inventors of this invention discovered that during cementing, conventional cementing methods, particularly the casing section, have high thermal conductivity due to the high thermal conductivity of both the cement stone and the casing. This makes them highly susceptible to formation and production temperatures. The cement heats up and cools down rapidly. Because of the casing's thermal expansion and contraction, the cement, in its liquid state, deforms along with the casing. However, this deformation is difficult to reverse after the cement solidifies, leading to micro-annular gaps at the casing interface and making it difficult to control the bonding quality. For geothermal wells, the high thermal conductivity of conventional cement stone also results in poor insulation and significant energy loss during geothermal energy delivery to the surface. The rate of temperature change in the cement slurry sealing section is directly related to the quality of the interface bonding, i.e., the overall cementing quality. Currently, the cementing industry has not paid sufficient attention to this, which to some extent hinders the advancement of cementing technology.

[0031] Therefore, this invention provides a low thermal conductivity cement slurry system and its preparation method. This invention reduces the thermal conductivity of the cement slurry system by adding a specific proportion of low thermal conductivity materials, thereby mitigating the impact of downhole temperature changes (such as formation or production temperatures) on the harmful stress and strain deformation of the casing in the return section. This slows down the shrinkage and expansion rate of the casing, reducing the probability of micro-annulus formation. It effectively improves the bonding quality of the interface between the cement stone and the return casing (i.e., the interface formed by the cement slurry and the return casing), improving the cementing quality of the return casing in oil and gas wells, reducing geothermal energy loss to the surface, improving the insulation effect of geothermal wells, and reducing the risk of wellhead gas leakage and annular pressure. The density range of the low thermal conductivity cement slurry system of this invention is 1.25-2.50 g / cm³. 3 With an applicable circulation temperature of 60-150℃, highly adjustable thickening time and fluidity, and a wide range of applications, this low thermal conductivity cementing slurry system can effectively promote technological progress in the cementing industry, providing strong technical support for large-scale exploration and development of deep natural gas and geothermal wells, and preventing wellhead gas leakage and annular pressure risks. Attached Figure Description

[0032] Figure 1 The density provided by the increased dosage of plastic granules compared to Comparative Examples 1-4 was 1.90 g / cm³. 3 The influence curve of thermal conductivity of cement slurry system.

[0033] Figure 2 The density provided by the addition of porous ceramic powder compared to comparative examples 5-9 was 2.20 g / cm³. 3 The influence curve of thermal conductivity of cement slurry system.

[0034] Figure 3 The density versus thermal conductivity curves of the low-density cement slurry systems provided in Comparative Examples 10-14 and Examples 5-9.

[0035] Figure 4 The density provided in Examples 1-4 was 1.90 g / cm³, which was achieved by increasing the amount of low thermal conductivity material added to the compound. 3 The influence curve of thermal conductivity of cement slurry system. Detailed Implementation

[0036] In order to provide a clearer understanding of the technical features, objectives and beneficial effects of the present invention, the technical solution of the present invention will now be described in detail below, but it should not be construed as limiting the scope of implementation of the present invention.

[0037] In the following examples and comparative examples, the experimental materials included: high sulfate-resistant (HSR) G-grade oil well cement, produced by Jiahua Special Cement Co., Ltd.; and T60 type hollow glass microspheres (density 0.60 g / cm³) produced by China Steel Group Maanshan Mining Research Institute Co., Ltd. 3 The following materials were used: PP plastic granules (average particle size 45 μm); porous ceramic powder (particle size 150 μm, porosity 65%) produced by Yiwu Qingxuan Plastic Products Co., Ltd.; diatomaceous earth (200 mesh) produced by Lingshou County Jiayu Mineral Products Processing Plant; and refined iron ore powder (6.05 g / cm³) produced by Emeishan Tuoyang Oilfield Engineering Technology Co., Ltd. 3 The following materials were used: 150-mesh refined iron ore powder; DRB-2S reinforcing material, manufactured by CNPC Engineering Technology Research Institute Co., Ltd.; DRA-1S inorganic salt early-strength agent, manufactured by CNPC Engineering Technology Research Institute Co., Ltd.; DRK-3S biopolymer suspending agent, manufactured by CNPC Engineering Technology Research Institute Co., Ltd.; DRT-1S polymer anti-channeling and toughening material, manufactured by CNPC Engineering Technology Research Institute Co., Ltd.; DRS-1S dispersant, manufactured by CNPC Engineering Technology Research Institute Co., Ltd.; DRF-1S acrylamide polymer solid water loss reducing agent, manufactured by CNPC Engineering Technology Research Institute Co., Ltd.; DRH-2L acrylamide polymer retarder, manufactured by CNPC Engineering Technology Research Institute Co., Ltd.; and distilled water for the experiment.

[0038] By measuring the temperature change of cement slurry per unit time under the same experimental conditions, the slower the temperature increases or decreases, the smaller the thermal conductivity, the better the insulation effect of the cement slurry, the weaker the damage to the cement sheath caused by the casing deformation caused by the formation temperature and production temperature, and the more beneficial it is to improving the insulation effect of the geothermal well.

[0039] Sample preparation and thermal conductivity determination were carried out in accordance with standards such as GB / T 19139-2012 "Test Methods for Cement in Oil Wells" and GB / T 10297-2015 "Determination of Thermal Conductivity of Non-metallic Solid Materials by Hot Wire Method".

[0040] Experimental instruments: KDRX-Ⅱ type transient rapid hot wire method thermal conductivity tester, Xiangtan Xiangyi Instrument Co., Ltd.; OWC-9360 type constant speed stirrer, Shenyang Aerospace University Applied Technology Research Institute; HH-420 type constant temperature digital display water tank, Changzhou Yineng Experimental Instrument Factory.

[0041] Comparative Example 1

[0042] This comparative example provides a cement slurry system comprising, by weight, the following components: 100 parts oil well cement, 0.5 parts dispersant DRS-1S, 3 parts water loss reducer DRF-1S, 0.3 parts defoamer polydimethylsiloxane, and 44 parts water. The density of this cement slurry system is 1.90 g / cm³. 3 The experimental results are shown in Figure 1 See Table 1.

[0043] Comparative Example 2

[0044] This comparative example provides a cement slurry system comprising, by weight, the following components: 100 parts oil well cement, 2 parts plastic granules, 0.5 parts dispersant DRS-1S, 3 parts water loss reducing agent DRF-1S, 0.3 parts defoamer polydimethylsiloxane, and 44 parts water. The density of this cement slurry system is 1.90 g / cm³. 3 The experimental results are shown in Figure 1 See Table 1.

[0045] Comparative Example 3

[0046] This comparative example provides a cement slurry system comprising, by weight, the following components: 100 parts oil well cement, 4 parts plastic granules, 0.5 parts dispersant DRS-1S, 3 parts water loss reducing agent DRF-1S, 0.3 parts defoamer polydimethylsiloxane, and 44.5 parts water. The density of this cement slurry system is 1.90 g / cm³. 3 The experimental results are shown in Figure 1 See Table 1.

[0047] Comparative Example 4

[0048] This comparative example provides a cement slurry system comprising, by weight, the following components: 100 parts oil well cement, 6 parts plastic granules, 0.5 parts dispersant DRS-1S, 3 parts water loss reducing agent DRF-1S, 0.3 parts defoamer polydimethylsiloxane, and 45 parts water. The density of this cement slurry system is 1.90 g / cm³. 3 The experimental results are shown in Figure 1 See Table 1.

[0049] Comparative Example 5

[0050] This comparative example provides a cement slurry system comprising, by weight, the following components: 100 parts oil well cement, 60 parts density regulator (iron ore powder), 10 parts reinforcing material (DRB-2S), 2 parts early-strength agent (DRA-1S), 0.5 parts suspending agent (DRK-3S), 3 parts anti-channeling and toughening material (DRT-1S), 0.8 parts dispersant (DRS-1S), 3 parts water loss reducing agent (DRF-1S), 0.5 parts retarder (DRH-2L), 0.3 parts defoamer (polydimethylsiloxane), and 53 parts water. The density of this cement slurry system is 2.20 g / cm³. 3 The experimental results are shown in Figure 2 See Table 1.

[0051] Comparative Example 6

[0052] This comparative example provides a cement slurry system comprising, by weight, the following components: 100 parts oil well cement, 60 parts density regulator (iron ore powder), 5 parts porous ceramic powder, 10 parts reinforcing material (DRB-2S), 2 parts early-strength agent (DRA-1S), 0.5 parts suspending agent (DRK-3S), 3 parts anti-channeling and toughening material (DRT-1S), 0.8 parts dispersant (DRS-1S), 3 parts water loss reducing agent (DRF-1S), 0.5 parts retarder (DRH-2L), 0.3 parts defoamer (polydimethylsiloxane), and 54 parts water. The density of this cement slurry system is 2.20 g / cm³. 3 The experimental results are shown in Figure 2 See Table 1.

[0053] Comparative Example 7

[0054] This comparative example provides a cement slurry system comprising, by weight, the following components: 100 parts oil well cement, 60 parts density regulator (iron ore powder), 10 parts porous ceramic powder, 10 parts reinforcing material (DRB-2S), 2 parts early-strength agent (DRA-1S), 0.5 parts suspending agent (DRK-3S), 3 parts anti-channeling and toughening material (DRT-1S), 0.8 parts dispersant (DRS-1S), 3 parts water loss reducing agent (DRF-1S), 0.5 parts retarder (DRH-2L), 0.3 parts defoamer (polydimethylsiloxane), and 55 parts water. The density of this cement slurry system is 2.20 g / cm³. 3 The experimental results are shown in Figure 2 See Table 1.

[0055] Comparative Example 8

[0056] This comparative example provides a cement slurry system comprising, by weight, the following components: 100 parts oil well cement, 60 parts density regulator (iron ore powder), 15 parts porous ceramic powder, 10 parts reinforcing material (DRB-2S), 2 parts early-strength agent (DRA-1S), 0.5 parts suspending agent (DRK-3S), 3 parts anti-channeling and toughening material (DRT-1S), 0.8 parts dispersant (DRS-1S), 3 parts water loss reducing agent (DRF-1S), 0.5 parts retarder (DRH-2L), 0.3 parts defoamer (polydimethylsiloxane), and 56 parts water. The density of this cement slurry system is 2.20 g / cm³. 3 The experimental results are shown in Figure 2 See Table 1.

[0057] Comparative Example 9

[0058] This comparative example provides a cement slurry system comprising, by weight, the following components: 100 parts oil well cement, 60 parts density regulator (iron ore powder), 20 parts porous ceramic powder, 10 parts reinforcing material (DRB-2S), 2 parts early-strength agent (DRA-1S), 0.5 parts suspending agent (DRK-3S), 3 parts anti-channeling and toughening material (DRT-1S), 0.8 parts dispersant (DRS-1S), 3 parts water loss reducing agent (DRF-1S), 0.5 parts retarder (DRH-2L), 0.3 parts defoamer (polydimethylsiloxane), and 57 parts water. The density of this cement slurry system is 2.20 g / cm³. 3 The experimental results are shown in Figure 2 See Table 1.

[0059] Comparative Example 10

[0060] This comparative example provides a cement slurry system comprising, by weight, the following components: 100 parts oil well cement, 60 parts density modifier (hollow glass microspheres), 3 parts early-strength agent (DRA-1S), 1.0 part suspending agent (DRK-3S), 3 parts anti-channeling and toughening material (DRT-1S), 0.8 parts dispersant (DRS-1S), 5 parts water loss reducer (DRF-1S), 0.3 parts retarder (DRH-2L), 0.3 parts defoamer (polydimethylsiloxane), and 108 parts water. The density of this cement slurry system is 1.20 g / cm³. 3 The experimental results are shown in Figure 3 See Table 1.

[0061] Comparative Example 11

[0062] This comparative example provides a cement slurry system comprising, by weight, the following components: 100 parts oil well cement, 40 parts density modifier (hollow glass microspheres), 3 parts early-strength agent (DRA-1S), 1.0 part suspending agent (DRK-3S), 3 parts anti-channeling and toughening material (DRT-1S), 0.8 parts dispersant (DRS-1S), 5 parts water loss reducer (DRF-1S), 0.3 parts retarder (DRH-2L), 0.3 parts defoamer (polydimethylsiloxane), and 83 parts water. The density of this cement slurry system is 1.30 g / cm³. 3 The experimental results are shown in Figure 3 See Table 1.

[0063] Comparative Example 12

[0064] This comparative example provides a cement slurry system comprising, by weight, the following components: 100 parts oil well cement, 27 parts density modifier (hollow glass microspheres), 3 parts early-strength agent (DRA-1S), 1.0 part suspending agent (DRK-3S), 3 parts anti-channeling and toughening material (DRT-1S), 0.8 parts dispersant (DRS-1S), 5 parts water loss reducer (DRF-1S), 0.3 parts retarder (DRH-2L), 0.3 parts defoamer (polydimethylsiloxane), and 80 parts water. The density of this cement slurry system is 1.40 g / cm³. 3 The experimental results are shown in Figure 3 See Table 1.

[0065] Comparative Example 13

[0066] This comparative example provides a cement slurry system comprising, by weight, the following components: 100 parts oil well cement, 19 parts density modifier (hollow glass microspheres), 3 parts early-strength agent (DRA-1S), 1.0 part suspending agent (DRK-3S), 3 parts anti-channeling and toughening material (DRT-1S), 0.8 parts dispersant (DRS-1S), 5 parts water loss reducer (DRF-1S), 0.3 parts retarder (DRH-2L), 0.3 parts defoamer (polydimethylsiloxane), and 67 parts water. The density of this cement slurry system is 1.50 g / cm³. 3 The experimental results are shown in Appendix 3 and Table 1.

[0067] Comparative Example 14

[0068] This comparative example provides a cement slurry system comprising, by weight, the following components: 100 parts oil well cement, 12 parts density modifier (hollow glass microspheres), 3 parts early-strength agent (DRA-1S), 1.0 part suspending agent (DRK-3S), 3 parts anti-channeling and toughening material (DRT-1S), 0.8 parts dispersant (DRS-1S), 5 parts water loss reducer (DRF-1S), 0.3 parts retarder (DRH-2L), 0.3 parts defoamer (polydimethylsiloxane), and 61 parts water. The density of this cement slurry system is 1.60 g / cm³. 3The experimental results are shown in Figure 3 See Table 1.

[0069] Comparative Example 15

[0070] This comparative example provides a cement slurry system comprising, by weight, the following components: 100 parts oil well cement, 0.5 parts dispersant DRS-1S, 3 parts water loss reducer DRF-1S, 5 parts reinforcing material SiC whiskers, 0.3 parts defoamer polydimethylsiloxane, and 44 parts water. The density of this cement slurry system is 1.90 g / cm³. 3 The experimental results are shown in Table 1.

[0071] Comparative Example 16

[0072] This comparative example provides a cement slurry system comprising, by weight, the following components: 100 parts oil well cement, 0.5 parts dispersant DRS-1S, 3 parts fluid loss reducer DRF-1S, 5 parts halloysite reinforcing material, 0.3 parts defoamer polydimethylsiloxane, and 44 parts water. The density of this cement slurry system is 1.90 g / cm³. 3 The experimental results are shown in Table 1.

[0073] Comparative Example 17

[0074] This comparative example provides a cement slurry system comprising, by weight, the following components: 100 parts oil well cement, 0.5 parts dispersant DRS-1S, 3 parts fluid loss reducer DRF-1S, 5 parts reinforcing material mullite, 0.3 parts defoamer polydimethylsiloxane, and 44 parts water. The density of this cement slurry system is 1.90 g / cm³. 3 The experimental results are shown in Table 1.

[0075] Comparative Example 18

[0076] This comparative example provides a cement slurry system comprising, by weight, the following components: 100 parts oil well cement, 0.5 parts dispersant DRS-1S, 3 parts fluid loss reducing agent DRF-1S, 5 parts reinforcing material (a mixture of SiC whiskers, halloysite, and mullite in a mass ratio of 2.5:1.5:1.5), 0.3 parts defoamer polydimethylsiloxane, and 44 parts water. The density of this cement slurry system is 1.90 g / cm³. 3 The experimental results are shown in Table 1.

[0077] Comparative Example 19

[0078] This comparative example provides a cement slurry system comprising, by weight, the following components: 100 parts oil well cement, 60 parts density regulator (iron ore powder), 10 parts reinforcing material DRB-2S, 2 parts early-strength agent DRA-1S, 1.5 parts suspending agent (a mixture of xanthan gum, styrax, and polyvinyl alcohol in a mass ratio of 1:1:1), 3 parts anti-channeling and toughening material DRT-1S, 0.8 parts dispersant DRS-1S, 3 parts water loss reducer DRF-1S, 0.5 parts retarder DRH-2L, 0.3 parts defoamer (polydimethylsiloxane), and 53 parts water. The density of this cement slurry system is 2.20 g / cm³. 3 The experimental results are shown in Table 1.

[0079] Comparative Example 20

[0080] This comparative example provides a cement slurry system comprising, by weight, the following components: 100 parts oil well cement, 60 parts density regulator (iron ore powder), 10 parts reinforcing material (DRB-2S), 2 parts early-strength agent (DRA-1S), 1.5 parts suspending agent (a mixture of xanthan gum, styrax, and sodium bentonite in a mass ratio of 1:1:2), 3 parts anti-channeling and toughening material (DRT-1S), 0.8 parts dispersant (DRS-1S), 3 parts water loss reducer (DRF-1S), 0.5 parts retarder (DRH-2L), 0.3 parts defoamer (polydimethylsiloxane), and 53 parts water. The density of this cement slurry system is 2.20 g / cm³. 3 The experimental results are shown in Table 1.

[0081] Comparative Example 21

[0082] This comparative example provides a cement slurry system comprising, by weight, the following components: 100 parts oil well cement, 60 parts density regulator (iron ore powder), 10 parts reinforcing material (DRB-2S), 2 parts early-strength agent (DRA-1S), 1.5 parts suspending agent (a mixture of styrene, polyvinyl alcohol, and sodium bentonite in a mass ratio of 1:1:2), 3 parts anti-channeling and toughening material (DRT-1S), 0.8 parts dispersant (DRS-1S), 3 parts water loss reducer (DRF-1S), 0.5 parts retarder (DRH-2L), 0.3 parts defoamer (polydimethylsiloxane), and 53 parts water. The density of this cement slurry system is 2.20 g / cm³. 3 The experimental results are shown in Table 1.

[0083] Comparative Example 22

[0084] This comparative example provides a cement slurry system comprising, by weight, the following components: 100 parts oil well cement, 60 parts density regulator (iron ore powder), 10 parts reinforcing material (DRB-2S), 2 parts early-strength agent (DRA-1S), 1.5 parts suspending agent (a mixture of xanthan gum, styrax, polyvinyl alcohol, and sodium bentonite in a mass ratio of 1:2:2:1.5), 3 parts anti-channeling and toughening material (DRT-1S), 0.8 parts dispersant (DRS-1S), 3 parts water loss reducer (DRF-1S), 0.5 parts retarder (DRH-2L), 0.3 parts defoamer (polydimethylsiloxane), and 53 parts water. The density of this cement slurry system is 2.20 g / cm³. 3 The experimental results are shown in Table 1.

[0085] Example 1

[0086] This embodiment provides a low thermal conductivity cementing slurry system, which comprises the following components by weight: 100 parts oil well cement, 2 parts low thermal conductivity material (a mixture of hollow glass microspheres, porous ceramic powder and diatomaceous earth in a mass ratio of 2:1:1), 5 parts reinforcing material (a mixture of SiC whiskers, halloysite and mullite in a mass ratio of 3:1:1), 1 part suspending agent (a mixture of xanthan gum, styrax, polyvinyl alcohol and sodium bentonite in a mass ratio of 1:1:1:2), 0.5 parts dispersant DRS-1S, 4 parts fluid loss reducing agent DRF-1S, 0.3 parts defoamer polydimethylsiloxane, and 44 parts water.

[0087] This low thermal conductivity cementitious slurry system is prepared through the following steps:

[0088] (1) According to the weight parts of each component mentioned above, the oil well cement, low thermal conductivity material, reinforcing material, suspending agent, dispersant and water loss reducing agent are mixed evenly under stirring at a speed of 100-150 r / min to obtain dry mixture;

[0089] (2) According to the weight parts of each component mentioned above, the defoamer and water are mixed evenly under stirring at a speed of 1000-1200 r / min to obtain a wet mixture;

[0090] (3) At a stirring speed of 4000±200r / min, the dry mixture is added to the wet mixture. After the dry mixture is completely wetted, stirring is continued for 30-50s to obtain the low thermal conductivity cementing slurry system.

[0091] The density of this cement slurry system is 1.90 g / cm³. 3 The experimental results are shown in Figure 4 See Table 1.

[0092] Example 2

[0093] This embodiment provides a low thermal conductivity cementing slurry system, comprising the following components by weight: 100 parts oil well cement, 4 parts low thermal conductivity material (a mixture of hollow glass microspheres, porous ceramic powder, and diatomaceous earth in a mass ratio of 2:1:1), 5 parts reinforcing material (a mixture of SiC whiskers, halloysite, and mullite in a mass ratio of 3:1:1), 1 part suspending agent (a mixture of xanthan gum, styrax, polyvinyl alcohol, and sodium bentonite in a mass ratio of 1:1:1:2), 0.5 parts dispersant DRS-1S, 4 parts fluid loss reducing agent DRF-1S, 0.3 parts defoamer polydimethylsiloxane, and 45 parts water. The preparation method of this low thermal conductivity cementing slurry system is the same as in Example 1. The density of this cementing slurry system is 1.90 g / cm³. 3 The experimental results are shown in Figure 4 See Table 1.

[0094] Example 3

[0095] This embodiment provides a low thermal conductivity cementing slurry system, comprising the following components by weight: 100 parts oil well cement, 6 parts low thermal conductivity material (a mixture of hollow glass microspheres, porous ceramic powder, and diatomaceous earth in a mass ratio of 2:1:1), 5 parts reinforcing material (a mixture of SiC whiskers, halloysite, and mullite in a mass ratio of 3:1:1), 1 part suspending agent (a mixture of xanthan gum, styrax, polyvinyl alcohol, and sodium bentonite in a mass ratio of 1:1:1:2), 0.5 parts dispersant DRS-1S, 4 parts fluid loss reducing agent DRF-1S, 0.3 parts defoamer polydimethylsiloxane, and 46 parts water. The preparation method of this low thermal conductivity cementing slurry system is the same as in Example 1. The density of this cementing slurry system is 1.90 g / cm³. 3 The experimental results are shown in Figure 4 See Table 1.

[0096] Example 4

[0097] This embodiment provides a low thermal conductivity cementing slurry system, comprising the following components by weight: 100 parts oil well cement, 8 parts low thermal conductivity material (a mixture of hollow glass microspheres, porous ceramic powder, and diatomaceous earth in a mass ratio of 2:1:1), 5 parts reinforcing material (a mixture of SiC whiskers, halloysite, and mullite in a mass ratio of 3:1:1), 1 part suspending agent (a mixture of xanthan gum, styrax, polyvinyl alcohol, and sodium bentonite in a mass ratio of 1:1:1:2), 0.5 parts dispersant DRS-1S, 4 parts fluid loss reducing agent DRF-1S, 0.3 parts defoamer polydimethylsiloxane, and 47 parts water. The preparation method of this low thermal conductivity cementing slurry system is the same as in Example 1. The density of this cementing slurry system is 1.90 g / cm³. 3 The experimental results are shown in Figure 4 See Table 1.

[0098] Example 5

[0099] This embodiment provides a low thermal conductivity cementing slurry system, which, by weight, comprises the following components: 100 parts oil well cement, 60 parts density regulator hollow glass microspheres, 5 parts low thermal conductivity material (a mixture of hollow glass microspheres, porous ceramic powder, and diatomaceous earth in a mass ratio of 2:1:1), 10 parts reinforcing material (a mixture of SiC whiskers, halloysite, and mullite in a mass ratio of 3:1:1), 3 parts early strength agent (a mixture of sodium sulfate, sodium thiosulfate, sodium aluminate, and calcium chloride in a mass ratio of 1:1:1:1), 2 parts suspending agent (a mixture of xanthan gum, styrax, polyvinyl alcohol, and sodium bentonite in a mass ratio of 1:1:1:2), 3 parts anti-channeling and toughening material DRT-1S, 1 part dispersant DRS-1S, 5 parts fluid loss reducing agent DRF-1S, and retarder DRH-2L. 0.4 parts of defoamer (polydimethylsiloxane) and 0.5 parts of water. The preparation method of this low thermal conductivity cementitious slurry system is basically the same as that of Example 1. The additional components in this example are added in the dry mixing and wet mixing steps, respectively. The density of this cementitious slurry system is 1.20 g / cm³. 3 The experimental results are shown in Figure 3 See Table 1.

[0100] Example 6

[0101] This embodiment provides a low thermal conductivity cementing slurry system, which, by weight, comprises the following components: 100 parts oil well cement, 40 parts density regulator hollow glass microspheres, 7 parts low thermal conductivity material (a mixture of hollow glass microspheres, porous ceramic powder, and diatomaceous earth in a mass ratio of 2:1:1), 10 parts reinforcing material (a mixture of SiC whiskers, halloysite, and mullite in a mass ratio of 3:1:1), 3 parts early strength agent (a mixture of sodium sulfate, sodium thiosulfate, sodium aluminate, and calcium chloride in a mass ratio of 1:1:1:1), 2 parts suspending agent (a mixture of xanthan gum, styrax, polyvinyl alcohol, and sodium bentonite in a mass ratio of 1:1:1:2), 3 parts anti-channeling and toughening material DRT-1S, 1 part dispersant DRS-1S, 5 parts fluid loss reducing agent DRF-1S, and 5 parts retarder DRH-2L. 0.4 parts of defoamer, 0.5 parts of polydimethylsiloxane, and 85 parts of water. The preparation method of this low thermal conductivity cementitious slurry system is basically the same as that of Example 1. The additional components in this example compared to Example 1 are added in the dry mixing and wet mixing steps, respectively. The density of this cementitious slurry system is 1.30 g / cm³. 3 The experimental results are shown in Figure 3 See Table 1.

[0102] Example 7

[0103] This embodiment provides a low thermal conductivity cementing slurry system, which, by weight, comprises the following components: 100 parts oil well cement, 27 parts density regulator hollow glass microspheres, 9 parts low thermal conductivity material (a mixture of hollow glass microspheres, porous ceramic powder, and diatomaceous earth in a mass ratio of 2:1:1), 10 parts reinforcing material (a mixture of SiC whiskers, halloysite, and mullite in a mass ratio of 3:1:1), 3 parts early strength agent (a mixture of sodium sulfate, sodium thiosulfate, sodium aluminate, and calcium chloride in a mass ratio of 1:1:1:1), 2 parts suspending agent (a mixture of xanthan gum, styrax, polyvinyl alcohol, and sodium bentonite in a mass ratio of 1:1:1:2), 3 parts anti-channeling and toughening material DRT-1S, 1 part dispersant DRS-1S, 5 parts fluid loss reducing agent DRF-1S, and 5 parts retarder DRH-2L. 0.4 parts of defoamer, 0.5 parts of polydimethylsiloxane, and 82 parts of water. The preparation method of this low thermal conductivity cementitious slurry system is basically the same as that of Example 1. The additional components in this example compared to Example 1 are added in the dry mixing and wet mixing steps, respectively. The density of this cementitious slurry system is 1.40 g / cm³. 3 The experimental results are shown in Figure 3 See Table 1.

[0104] Example 8

[0105] This embodiment provides a low thermal conductivity cementing slurry system, which, by weight, comprises the following components: 100 parts oil well cement, 19 parts density regulator hollow glass microspheres, 11 parts low thermal conductivity material (a mixture of hollow glass microspheres, porous ceramic powder, and diatomaceous earth in a mass ratio of 2:1:1), 10 parts reinforcing material (a mixture of SiC whiskers, halloysite, and mullite in a mass ratio of 3:1:1), 3 parts early strength agent (a mixture of sodium sulfate, sodium thiosulfate, sodium aluminate, and calcium chloride in a mass ratio of 1:1:1:1), 2 parts suspending agent (a mixture of xanthan gum, styrax, polyvinyl alcohol, and sodium bentonite in a mass ratio of 1:1:1:2), 3 parts anti-channeling and toughening material DRT-1S, 1 part dispersant DRS-1S, 5 parts fluid loss reducing agent DRF-1S, and 5 parts retarder DRH-2L. 0.4 parts of defoamer, 0.5 parts of polydimethylsiloxane, and 69 parts of water. The preparation method of this low thermal conductivity cementitious slurry system is basically the same as that of Example 1. The additional components in this example compared to Example 1 are added in the dry mixing and wet mixing steps, respectively. The density of this cementitious slurry system is 1.50 g / cm³. 3 The experimental results are shown in Figure 3 See Table 1.

[0106] Example 9

[0107] This embodiment provides a low thermal conductivity cementing slurry system, which, by weight, comprises the following components: 100 parts oil well cement, 12 parts density regulator hollow glass microspheres, 13 parts low thermal conductivity material (a mixture of hollow glass microspheres, porous ceramic powder, and diatomaceous earth in a mass ratio of 2:1:1), 10 parts reinforcing material (a mixture of SiC whiskers, halloysite, and mullite in a mass ratio of 3:1:1), 3 parts early strength agent (a mixture of sodium sulfate, sodium thiosulfate, sodium aluminate, and calcium chloride in a mass ratio of 1:1:1:1), 2 parts suspending agent (a mixture of xanthan gum, styrax, polyvinyl alcohol, and sodium bentonite in a mass ratio of 1:1:1:2), 3 parts anti-channeling and toughening material DRT-1S, 1 part dispersant DRS-1S, 5 parts fluid loss reducing agent DRF-1S, and retarder DRH-2L. 0.4 parts of defoamer (polydimethylsiloxane) and 0.5 parts of water. The preparation method of this low thermal conductivity cementitious slurry system is basically the same as that of Example 1. The additional components in this example compared to Example 1 are added in the dry mixing and wet mixing steps, respectively. The density of this cementitious slurry system is 1.60 g / cm³. 3 The experimental results are shown in Figure 3 See Table 1.

[0108] Table 1 Comprehensive performance parameters of cement grout

[0109]

[0110]

[0111] Note: ① The experimental conditions for Comparative Examples 1 to 4, Comparative Examples 15 to 18, and Examples 1 to 4 are as follows: API dehydration test conditions: 60℃×30min, compressive strength test conditions: 60℃×20.7MPa, thickening time test conditions: 60℃×30MPa×30min;

[0112] ② The experimental conditions for Comparative Examples 5 to 9 and Comparative Examples 19 to 22 were as follows: API dehydration test conditions: 110℃×30min, compressive strength test conditions: 80℃×20.7MPa, thickening time test conditions: 110℃×100MPa×50min;

[0113] ③ The experimental conditions for Comparative Examples 10 to 14, and Examples 5 to 9 were as follows: API dehydration test conditions: 150℃×30min, compressive strength test conditions: 150℃×20.7MPa, and thickening time test conditions: 150℃×80MPa×40min.

[0114] Figure 1 The density provided by the increased dosage of plastic granules compared to Comparative Examples 1-4 was 1.90 g / cm³. 3The influence curve of thermal conductivity on the cement slurry system. From Figure 1 It can be seen that the conventional cement paste formulation without plastic particles has the highest thermal conductivity. As the amount of plastic particles increases, the thermal conductivity of the cement paste decreases, indicating that adding plastic particles to conventional cement paste formulations can reduce its thermal conductivity. Analysis suggests that the thermal conductivity of plastic particles themselves is only 0.19–0.26 W / (m·K), possessing excellent heat conduction mitigation capabilities; therefore, introducing this material into cement paste will reduce its thermal conductivity. However, as shown in Table 1, adding plastic particles to the cement paste system has disadvantages such as increased water loss and reduced compressive strength.

[0115] Figure 2 The density provided by the addition of porous ceramic powder compared to comparative examples 5-9 was 2.20 g / cm³. 3 The influence curve of thermal conductivity on the cement slurry system. From Figure 2 It can be seen that, compared with conventional cement paste, adding porous ceramics to the cement formula can reduce the thermal conductivity of the cement paste. Furthermore, the decreasing trend in thermal conductivity becomes more pronounced with increasing amounts of porous ceramics. Analysis suggests that porous ceramics, being porous insulation materials, contain a certain amount of air within their pores, resulting in better thermal insulation performance. Their heat absorption and release rates are slower than conventional cement paste, hence the lower thermal conductivity. However, as shown in Table 1, adding porous ceramics to the cement slurry system has disadvantages such as decreased settling stability and increased free liquid content.

[0116] Figure 3 The density versus thermal conductivity curves are for the low-density cement paste systems provided in Comparative Examples 10-14 and Examples 5-9. From... Figure 3 It can be seen that the thermal conductivity of low-density cement stone decreases with decreasing cement paste density. This is because a large number of hollow glass microspheres are added to the low-density cement stone. These materials are closed-cell hollow spherical materials with excellent heat insulation and heat preservation functions, thus significantly slowing down the heat absorption and release rates of the cement stone. Moreover, the decreasing trend of thermal conductivity is particularly obvious with increasing amounts of these materials. Table 1 shows that adding hollow glass microspheres to the cement paste system, while reducing the density of the cement paste, has a certain impact on the API water loss performance and compressive strength of the cement paste.

[0117] from Figure 3It can be seen that by adding a compound low thermal conductivity material (a mixture of hollow glass microspheres, porous ceramic powder, and diatomaceous earth in a mass ratio of 2:1:1), a reinforcing material (a mixture of SiC whiskers, halloysite, and mullite in a mass ratio of 3:1:1), an early strength agent (a mixture of sodium sulfate, sodium thiosulfate, sodium aluminate, and calcium chloride in a mass ratio of 1:1:1:1), and a suspending agent (a mixture of xanthan gum, styrax, polyvinyl alcohol, and sodium bentonite in a mass ratio of 1:1:1:2), the thermal conductivity of low-density cement slurry of the same density is significantly reduced. Table 1 shows that the settling stability, free liquid content, and compressive strength of the cement slurry are significantly improved, therefore this system possesses good workability.

[0118] Figure 4 The density provided in Examples 1-4 was 1.90 g / cm³, which was achieved by increasing the amount of low thermal conductivity material added to the compound. 3 The influence curve of thermal conductivity on the cement slurry system. From Figure 4 It can be seen that at 1.90 g / cm 3 Adding the composite low thermal conductivity material of this invention to cement slurry can significantly reduce the thermal conductivity of cement stone, and the decreasing trend of the thermal conductivity of cement stone becomes more obvious with the increase of the amount of composite low thermal conductivity material. This invention uses hollow glass microspheres, porous ceramic powder, and diatomaceous earth in a mass ratio of 2:1:1, which has good thermal insulation effect, and the heat absorption and release rates are slower than those of conventional cement stone, thus resulting in a lower thermal conductivity. The amount of composite low thermal conductivity material added is 1.90 g / cm³. 3 Cement grout with added plastic particles at 1.90 g / cm³ 3 Compared to cement slurry, the thermal conductivity is significantly lower. As shown in Table 1, the cement slurry containing the compound low thermal conductivity material, compound suspending stabilizer, and compound reinforcing material of this invention exhibits significantly improved overall performance compared to cement slurry containing plastic particles.

[0119] The above research results show that the compounded low thermal conductivity material used in this invention can effectively reduce the thermal conductivity of cement stone. The lower the thermal conductivity of the cement stone, the less impact the casing deformation caused by bottom hole temperature and production temperature has on the cement sheath. This is beneficial for improving the cement bonding effect and cementing quality of the reconnected casing, and helps prevent annular gas leakage and wellhead pressurization. Simultaneously, the addition of compounded reinforcing materials and compounded suspension stabilizers to the cement slurry system significantly improves and enhances the conventional application performance of the cement slurry.

[0120] In summary, the low thermal conductivity cement slurry system provided by this invention reduces the impact of casing deformation caused by temperature changes on the cement sheath by lowering the thermal conductivity of the cement slurry system, thereby improving the bonding quality of the cement stone and casing interface. This represents a significant breakthrough in cementing technology, providing a scientific and reasonable theoretical basis for selecting cement slurry systems for casing reconnection cementing and geothermal well cementing. It further enriches cementing technology theory and, to a certain extent, achieves a reliable improvement in the bonding quality of the cement stone and casing reconnection interface, reducing the risk of poor casing reconnection cementing quality and wellhead gas leakage. This promotes the advancement of cementing technology and provides strong technical support for improving cementing quality and reducing annular pressure risk in deep natural gas wells and geothermal wells. It plays an important role in solving wellhead gas leakage and annular pressure problems and improving wellbore sealing integrity, and is of great significance for ensuring the exploration, development, and sustainable development of oil and gas resources.

Claims

1. A low thermal conductivity cementing slurry system, comprising, by weight, the following components: 100 parts oil well cement, 0-125 parts density regulator, 2-20 parts low thermal conductivity material, 5-35 parts reinforcing material, 0-5 parts early strength agent, 1-3 parts suspending agent, 0-10 parts elastic material, 0-6 parts anti-channeling and toughening material, 0.5-1.5 parts dispersant, 1.5-6 parts fluid loss reducing agent, 0-2 parts retarder, 0.2-0.5 parts defoamer, and 44-110 parts water; in, The low thermal conductivity material comprises a mixture of hollow glass microspheres, porous ceramic powder and diatomaceous earth in a mass ratio of (1.5-2.5):(0.5-1.5):(0.5-1.5); The reinforcing material comprises a mixture of SiC whiskers, halloysite, and mullite in a mass ratio of (2.5-3.5):(0.5-1.5):(0.5-1.5); The suspending agent comprises a mixture of xanthan gum, styrax, polyvinyl alcohol, and sodium bentonite in a mass ratio of (0.5-1.5):(0.5-1.5):(0.5-1.5):(1.5-2.5). The early strength agent comprises a mixture of sodium sulfate, sodium thiosulfate, sodium aluminate, and calcium chloride in a mass ratio of (0.5-1.5):(0.5-1.5):(0.5-1.5):(0.5-1.5).

2. The low thermal conductivity cementing slurry system according to claim 1, wherein, By weight, the low thermal conductivity cement slurry system comprises the following components: 100 parts oil well cement, 10-125 parts density regulator, 2-13 parts low thermal conductivity material, 5-20 parts reinforcing material, 2-4 parts early strength agent, 1-3 parts suspending agent, 0-10 parts elastic material, 2-4 parts anti-channeling and toughening material, 0.5-1.5 parts dispersant, 1.5-6 parts fluid loss reducing agent, 0.2-2 parts retarder, 0.2-0.5 parts defoamer, and 44-110 parts water.

3. The low thermal conductivity cementing slurry system according to claim 1, wherein, The density of the hollow glass microspheres in the low thermal conductivity material is 0.44-0.65 g / cm³. 3 The average particle size is 10-200 μm.

4. The low thermal conductivity cementing slurry system according to claim 1, wherein, The porous ceramic powder in the low thermal conductivity material has a particle size of 10-300 μm and a porosity of 40%-80%.

5. The low thermal conductivity cementing slurry system according to claim 1, wherein, The diatomaceous earth in the low thermal conductivity material has a particle size of 150-250 mesh.

6. The low thermal conductivity cementing slurry system according to claim 1, wherein, The density regulator includes a lightening agent and / or a weighting agent; the lightening agent includes hollow glass microspheres; the weighting agent includes refined iron ore powder.

7. The low thermal conductivity cementing slurry system according to claim 6, wherein, The density of the hollow glass microspheres in the density regulator is 0.44-0.65 g / cm³. 3 The average particle size is 10-200 μm.

8. The low thermal conductivity cementing slurry system according to claim 6, wherein, The density of the refined iron ore powder in the density regulator is 5.05-7.20 g / cm³. 3 The average particle size is 100-200 mesh.

9. The low thermal conductivity cementing slurry system according to claim 1, wherein, The elastic material includes rubber-based elastic materials.

10. The low thermal conductivity cementing slurry system according to claim 1, wherein, The anti-migration toughening material includes polymer-based anti-migration toughening materials.

11. The low thermal conductivity cementing slurry system according to claim 1, wherein, The dispersant includes aldehyde-ketone condensate dispersants and / or polystyrene sulfonate dispersants.

12. The low thermal conductivity cementing slurry system according to claim 1, wherein, The water loss reducing agent includes acrylamide polymer-based water loss reducing agents.

13. The low thermal conductivity cementing slurry system according to claim 1, wherein, The retarder includes one or a combination of several of the following: organic acid retarder, acrylamide polymer retarder, and 2-acrylamide-2-methylpropanesulfonic acid polymer retarder.

14. The low thermal conductivity cementing slurry system according to claim 1, wherein, The defoamer includes one or a combination of several of organic ester compounds, polyoxypropylene glycerol ethers, and polydimethylsiloxane.

15. The low thermal conductivity cementing slurry system according to claim 1, wherein, The oil well cement includes Grade G oil well cement.

16. The low thermal conductivity cementing slurry system according to any one of claims 1-15, wherein, The density of the low thermal conductivity cement slurry system is 1.25-2.50 g / cm³. 3 The applicable oil well circulation temperature is 60-150℃, and the thermal conductivity of the low thermal conductivity cement slurry system is 0.18-0.42W / mK.

17. A method for preparing a low thermal conductivity cementing slurry system according to any one of claims 1-16, comprising the following steps: (1) According to the weight parts of each component, the oil well cement, density regulator, low thermal conductivity material, reinforcing material, early strength agent, suspending agent, elastic material, anti-channeling toughening material and dispersant are mixed evenly. When the water loss reducing agent used is solid, it is mixed evenly with other components in this step to obtain dry mixture. (2) Mix the retarder, defoamer and water evenly according to the weight parts of each component. When the water loss reducing agent used is liquid, mix it evenly with other components in this step to obtain a wet mixture. (3) Mix the dry mixture and the wet mixture evenly to obtain the low thermal conductivity cement slurry system.

18. The method for preparing the low thermal conductivity cementing slurry system according to claim 17, wherein, The mixing in step (1) is carried out under stirring at a speed of 100-150 r / min.

19. The method for preparing the low thermal conductivity cementing slurry system according to claim 17, wherein, The mixing in step (2) is carried out under stirring at a speed of 1000-1200 r / min.

20. The method for preparing the low thermal conductivity cementing slurry system according to claim 17, wherein, Step (3) is as follows: at a stirring speed of 4000±200r / min, the dry mixture is added to the wet mixture. After the dry mixture is completely wetted, stirring is continued for 30-50s to obtain the low thermal conductivity cementing slurry system.

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