Cement paste system as well as preparation method and application thereof

Abstract

The invention provides a cement paste system as well as a preparation method and application thereof. The cement paste system comprises 10-50% of graphite slag, 1-2% of a fluid loss agent, 0.1-1% of a dispersing agent and 30-70% of water. The cement paste system disclosed by the invention has the advantages of good heat conduction performance, low water loss, easiness in pump injection, simplicity in preparation operation and the like, all performance indexes of the cement paste completely meet field well cementation requirements, and the adopted graphite slag is an industrial waste material, is low in price and has the characteristics of environment friendliness and low cost.

Description

Technical Field

[0001] The invention belongs to the technical field of drilling fluid, and in particular relates to a cement slurry system and a preparation method and application thereof. Background Art

[0002] With the gradual deepening of oil and gas exploration and development, the development of unconventional and complex oil and gas resources has been increasingly strengthened. The geological conditions of oil and gas reservoirs faced by cementing operations have become more complex. Abnormally high-pressure gas, high-pressure salt water layers, low-pressure leaky formations, abnormally low-pressure oil and gas layers, and high-temperature and high-pressure formations are often encountered during cementing. Therefore, it is necessary to use corresponding cement varieties and select appropriate admixtures to ensure safe construction and project quality. Faced with the severe situation of continued low oil prices, the research and development of low-cost high-strength cement slurry systems is an effective way to reduce cementing costs and achieve energy conservation and efficiency improvement.

[0003] The application of graphite slag cement-based materials can effectively solve the above problems. Graphite slag is an industrial waste material with low price. It can be used to prepare oil well cement slurry, which can save cement raw materials and reduce cementing costs. At present, domestic and foreign researchers have evaluated the applicability of graphite slag in building materials, mechanical property improvement or microstructural changes, but the research on changing the performance of cement-based materials with graphite slag is still in its infancy, and the research on adding graphite slag to cement for oil and gas well cementing has not been reported. There is a lack of relevant experience and information for reference in cementing engineering design and construction.

[0004] There is no shortage of patent records for cementing cement, for example: the patent with the invention name "A thermal conductivity cementing cement system for hot dry rock production wells" (application number 202011432234.5, application publication number CN 112321219 A), the thermal conductivity cementing cement system belongs to the technical field of cement slurry system, and is composed of the following raw materials by weight percentage: low hydration thermal cement or low calcium-silicon ratio cement 70-88%; high temperature strength stabilizer 10.5-25%; thermal conductivity material 1-8%; high temperature toughening agent 0.5-4%, effectively improving the high temperature strength stability, high toughness and low thermal conductivity of the cementing cement ring. The cementing cement system obtained in the present invention can meet the performance requirements of hot dry rock production wells for cementing cement at high temperature stability, high toughness and low thermal conductivity.

[0005] The invention name is "A thermal conductivity cement system for hot dry rock production wells" (application number 201710344089.7, application publication number CN 107216071 A). The present invention specifically relates to a thermal conductivity cement slurry for cementing the low-temperature section of a deep geothermal well and a preparation method thereof. The thermal conductivity cement slurry for cementing the low-temperature section of a deep geothermal well is prepared from the following raw materials in weight percentage: 15-25% oil well cement, 15-25% oil well ultrafine cement, 4-7% tungsten diselenide, 2-5% nano-silicon dioxide, 4-7% hollow glass microspheres, 1-4% early strength agent, 1-2% fluid loss reducer, 0.2-0.6% dispersant, 1-3% glass wool fiber, 5-10% silicate, and the balance is water. The preparation method thereof is as follows: oil well cement, oil well ultrafine cement, tungsten diselenide, nano silicon dioxide, hollow glass microspheres, early strength agent, fluid loss agent, dispersant and water are added in sequence, stirred until uniformly mixed, and then glass wool fiber and silicate are added in sequence, stirred until uniformly mixed. The thermal conductivity cement slurry for cementing low temperature section of deep geothermal well of the present invention has good thermal conductivity, and has the advantages of low density, early strength, low water loss, easy pumping, etc., and its various performance indicators fully meet the requirements of on-site cementing.

[0006] Introducing graphite slag into the research and development of cement can not only reduce the occupation of farmland and pollution to the surrounding environment, but also prevent soil erosion of graphite slag and avoid the pollution of air environment by dust generated during storage, which has huge social and economic benefits. The reuse of graphite slag instead of river sand can alleviate the urgent need for natural sand and gravel resources, reduce the cost of oil well cement, and conform to the development policy of "resource conservation and environmental friendliness". Therefore, it is of great significance to explore the application of graphite slag in cementing cement materials. Summary of the invention

[0007] In order to solve the above problems in the prior art, the present invention provides a cement slurry system and a preparation method and application thereof.

[0008] In a first aspect, the present invention provides a cement slurry system, which, based on the mass of cement, further comprises 10-50% of graphite slag, 1-2% of fluid loss additive, 0.1-1% of dispersant and 30-70% of water.

[0009] As a specific embodiment of the present invention, based on the mass of cement, the cement slurry system further comprises 20-30% of graphite slag, 1-2% of fluid loss reducer, 0.1-1% of dispersant and 30-50% of water.

[0010] As a specific embodiment of the present invention, the cement is a high sulfate-resistant oil well cement.

[0011] As a specific embodiment of the present invention, the cement is G-grade HSR cement.

[0012] As a specific embodiment of the present invention, the average particle size of the graphite slag is 20-30 μm.

[0013] As a specific embodiment of the present invention, the average particle size of the graphite slag is 28.78 μm.

[0014] As a specific embodiment of the present invention, the dispersant is a drag reducer USZ.

[0015] As a specific embodiment of the present invention, the fluid loss reducer is an AMPS type fluid loss reducer, which has strong heat and salt resistance and high polymerization activity.

[0016] In a second aspect, the present invention provides a method for preparing the cement slurry system described in the first aspect, comprising: uniformly mixing cement, graphite slag, a fluid loss reducer, a dispersant and water to obtain the cement slurry system.

[0017] Specifically, the mixing method is configured according to GB / T10238-2015 standard.

[0018] In a third aspect, the present invention provides application of the cement slurry system described in the first aspect or the cement slurry system prepared by the preparation method described in the second aspect in the field of well cementing.

[0019] The above raw materials in the present invention can be prepared in-house or commercially available, and the present invention is not particularly limited thereto.

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

[0021] The cement slurry system of the present invention has good thermal conductivity. In addition to meeting the requirements of low density and low-temperature early strength of the cementing heat conduction cement slurry system, its thermal conductivity is outstanding. It also has the advantages of low water loss, easy pumping and simple preparation and operation. Its various performance indicators fully meet the requirements of on-site cementing. The graphite slag used is industrial waste, low in price, and has the characteristics of green environmental protection and low cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 The thermal conductivity test results of Example 1 and Comparative Example 1 of the present invention are shown in FIG. DETAILED DESCRIPTION

[0023] The present invention will be further described below in conjunction with specific embodiments, but they do not constitute any limitation to the present invention.

[0024] The specific information of the reagents used in the embodiments of the present invention is as follows:

[0025] The cement is Zhongchang G-grade HSR cement, manufactured by Zhongchang Cement Plant;

[0026] Graphite slag was from Shandong Obot Petroleum Co., Ltd., with an average particle size of 28.78 μm;

[0027] The fluid loss additive was from Shandong Obot Petroleum Co., Ltd., model SYJ-1;

[0028] The drag reducer USZ was from Shandong Oubote Petroleum Co., Ltd. and its model number was SYJZ-1.

[0029] Example 1

[0030] This embodiment provides a cement slurry system and a preparation method thereof, the specific details of which are as follows:

[0031] 100 parts by weight of cement, 25 parts by weight of graphite slag, 1.2 parts by weight of AMPS fluid loss reducer, 0.5 parts by weight of drag reducer USZ, and 42 parts by weight of water are used to prepare cement slurry according to GB / T10238-2015 standard.

[0032] The thermal conductivity of the cement slurry system obtained in Example 1 was tested, and the thermal conductivity was found to be 2.37 W / m·k. Figure 1 shown.

[0033] Example 2

[0034] This embodiment provides a cement slurry system and a preparation method thereof, the specific details of which are as follows:

[0035] 100 parts by weight of cement, 20 parts by weight of graphite slag, 1.2 parts by weight of AMPS fluid loss reducer, 0.5 parts by weight of drag reducer USZ, and 42 parts by weight of water are used to prepare cement slurry according to GB / T10238-2015 standard.

[0036] The thermal conductivity of the cement slurry system obtained in Example 2 was tested, and the thermal conductivity was measured to be 2.39 W / m·k.

[0037] Example 3

[0038] This embodiment provides a cement slurry system and a preparation method thereof, the specific details of which are as follows:

[0039] 100 parts by weight of cement, 30 parts by weight of graphite slag, 1.2 parts by weight of AMPS fluid loss reducer, 0.5 parts by weight of drag reducer USZ, and 42 parts by weight of water are used to prepare cement slurry according to GB / T10238-2015 standard.

[0040] The thermal conductivity of the cement slurry system obtained in Example 2 was tested, and the thermal conductivity was measured to be 2.40 W / m·k.

[0041] Comparative Example 1

[0042] The comparative example provides Shengwei cement paste, which is composed of cement, 0.8% AMPS fluid loss reducer, and 0.5% drag reducer USZ. The thermal conductivity is 1.13 W / m·k. Figure 1 shown.

[0043] Test Example 1

[0044] The cement slurry system obtained in Example 1 was subjected to density, water loss, strength, and pressurized thickening test tests. The test results are shown in Table 1. The free liquid volume was 0 after 2 hours, and the density difference between the top and bottom of the cement stone was less than 0.01 g / cm 3 The cement slurry system has good sedimentation and suspension stability, which can effectively ensure the uniformity and stability of the cement slurry during the waiting period and prevent the cement slurry from settling and causing oil, gas and water channeling. See Table 1.

[0045] Table 1

[0046] project Graphite slag cement slurry <![CDATA[Density g / cm 3 > 1.89 API water loss ml (60℃*6.9MPa*30min) 36 Free liquid % 0 Pressurization thickening time min (60℃*30MPa*25min) 218 Compressive strength MPa (60℃*20.7MPa*24h) 17.26 Compressive strength MPa (142℃*20.7MPa*168h) 22.29

[0047] As shown in Table 1, the water loss performance of the cement paste system is excellent. The 24h compressive strength of the cement paste is 17.26MPa, and the 7d compressive strength is 22.14MPa / 142℃×21MPa, which can fully meet the needs of the project.

[0048] Test Example 2

[0049] The thermal conductivity of the cement slurry system obtained in Example 1 and the cement slurry system obtained in Comparative Example 1 was tested. The thermal conductivity test results are as follows: Figure 1 As shown, the thermal conductivity coefficient of the conventional density cement paste of Comparative Example 1 at room temperature is 1.13 W / (m·K), and the thermal conductivity coefficient of the graphite cement slurry system of Example 1 is 2.37 W / (m·K). The lower the thermal conductivity coefficient, the worse the heat transfer effect and the better the thermal conduction effect. The thermal conductivity coefficients of graphite cement paste and conventional density cement paste are both less than 5 W / (m·K), indicating that both have good thermal conduction and heat insulation effects.

[0050] Test Example 3

[0051] The mechanical properties of the cement slurry system obtained in Example 1 were tested, and the test results are shown in Table 2:

[0052] Table 2

[0053]

[0054] The elastic modulus and Poisson's ratio of a material can characterize the material's ability to resist deformation within the elastic range. The lower the elastic modulus, the greater the material's ability to recover deformation within the elastic deformation range. The data in Table 2 show that the elastic modulus of the cement slurry system obtained in Example 1 is 8.67 GPa, and the Poisson's ratio is close to 0.20, which means that the cement slurry system has high strength and good mechanical deformation capacity.

[0055] In summary, the cement slurry system of the present invention has good thermal conductivity. In addition to meeting the requirements of low-temperature early strength of cementing heat conduction cement slurry system, its thermal conductivity is outstanding. It also has the advantages of low water loss, easy pumping and simple preparation and operation. Its various performance indicators fully meet the requirements of on-site cementing. The graphite slag used is industrial waste, low in price, and has the characteristics of green environmental protection and low cost.

[0056] Any numerical value mentioned in the present invention, if there is only an interval of two units between any minimum value and any maximum value, includes all values ​​from the minimum value to the maximum value each time increasing by one unit. For example, if the amount of a component, or the value of a process variable such as temperature, pressure, time, etc. is declared to be 50-90, in this specification it means that 51-89, 52-88... and 69-71 and 70-71 are specifically listed. For non-integer values, 0.1, 0.01, 0.001 or 0.0001 can be appropriately considered as a unit. These are just some specially specified examples. In this application, in a similar manner, all possible combinations of numerical values ​​between the listed minimum and maximum values ​​are considered to have been disclosed.

[0057] It should be noted that the embodiments described above are only used to explain the present invention and do not constitute any limitation to the present invention. The present invention has been described with reference to typical embodiments, but it should be understood that the words used therein are descriptive and explanatory words, rather than restrictive words. The present invention may be modified as specified within the scope of the claims of the present invention, and the present invention may be revised without departing from the scope and spirit of the present invention. Although the present invention described therein relates to specific methods, materials and embodiments, it does not mean that the present invention is limited to the specific examples disclosed therein, on the contrary, the present invention can be extended to all other methods and applications with the same functions.

Claims

1. A cement slurry system, characterized in that: Based on the mass of cement, the cement slurry system also includes 10-50% of graphite slag, 1-2% of fluid loss reducer, 0.1-1% of dispersant and 30-70% of water.

2. The cement slurry system according to claim 1, characterized in that: Based on the mass of cement, the cement slurry system also includes 20-30% of graphite slag, 1-2% of fluid loss reducer, 0.1-1% of dispersant and 30-50% of water.

3. The cement slurry system according to claim 1 or 2, characterized in that: The cement is a highly sulfate-resistant oil well cement.

4. The cement slurry system according to any one of claims 1 to 3, characterized in that: The cement is G-grade HSR cement.

5. The cement slurry system according to any one of claims 1 to 4, characterized in that: The average particle size of the graphite slag is 20-30 μm.

6. The cement slurry system according to any one of claims 1 to 5, characterized in that: The average particle size of the graphite slag is 28.78 μm.

7. The cement slurry system according to any one of claims 1 to 6, characterized in that: The dispersant is drag reducer USZ.

8. The cement slurry system according to any one of claims 1 to 7, characterized in that: The fluid loss additive is an AMPS type fluid loss additive.

9. A method for preparing the cement slurry system according to any one of claims 1 to 8, characterized in that: The method comprises: uniformly mixing cement, graphite slag, a fluid loss reducer, a dispersant and water to obtain the cement slurry system.

10. Use of the cement slurry system according to any one of claims 1 to 8 or the cement slurry system prepared by the preparation method according to claim 9 in the field of well cementing.

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