High-density salt-resistant tough cement paste and preparation method thereof

Abstract

The invention discloses high-density salt-resistant tough cement paste and a preparation method thereof. The cement paste is prepared from the following raw materials in parts by mass: 100 parts of cement, 60-260 parts of iron powder, 10-50 parts of micro manganese, 30-40 parts of a reinforcing material, 5-10 parts of a toughening material, 30-50 parts of micro silicon, 3-5 parts of a fluid loss agent, 3-5 parts of a suspending agent, 5-15 parts of a stabilizer, 5-10 parts of a dispersing agent, 5-10 parts of a salt pollution resisting agent, 10-15 parts of a retarder, 2.5-5 parts of a defoaming agent and 40-60 parts of saline water. Compared with a conventional system, the cement paste system has the advantages that the average pore size of the cement paste is reduced, the total porosity is reduced, the 2.1-2.8 g / cm < 3 > high-temperature-resistant high-density cement paste system is finally formed, and the problems that the cement paste system is poor in high-temperature stability, and set cement strength development is slow are solved. According to the prepared cement paste system, the density difference of the system is smaller than 0.05 g / cm < 3 > under the condition of 200 DEG C, the 48-hour compressive strength is larger than 40 MPa, the 7-day compressive strength is 45 MPa, and the cement paste system does not decline.

Description

Technical Field

[0001] The invention relates to high-density salt-resistant toughness cement slurry and a preparation method thereof. Background Art

[0002] With the continuous deepening of exploration and development, oil and gas drilling is constantly moving towards deep reservoirs with high temperature and pressure. To ensure the safe cementing of deep wells, a good high-temperature and high-density cement slurry system must be used as a guarantee. The pressure coefficient of deep formations is greater than 2.0, the temperature is greater than 180°C, the tectonic stress is large, and there are special formations such as salt rock, gypsum salt, and mirabilite. Therefore, the oil field will have problems such as high temperature, high pressure, and narrow safety density window. In order to ensure the stability of the high-pressure layer during safe cementing, high-density cement slurry is required to withstand the long-term alternating load of deep wells. Due to the high solid content of the ultra-high-density cement slurry system, a series of problems may arise during field application, such as difficulty in increasing density, difficulty in adjusting performance, poor fluidity, etc. Such problems will further increase the difficulty of field operations of the high-density cement slurry system. Summary of the invention

[0003] In order to at least partially solve the above-mentioned technical problems existing in the prior art, an embodiment of the present invention provides a high-density salt-resistant and tough cement slurry and a preparation method thereof to solve the problem of safe cementing in reservoir blocks with high formation pressure coefficient, high bottom hole temperature, long sealing section, and complex gypsum-salt layers.

[0004] As one aspect of the present invention, a high-density, salt-resistant and tough cement slurry is provided. The cement slurry comprises the following raw materials, by mass percentage: 100 parts of cement, 60-260 parts of iron powder, 10-50 parts of micro manganese, 30-40 parts of reinforcing material, 5-10 parts of toughening material, 30-50 parts of micro silicon, 3-5 parts of fluid loss reducer, 3-5 parts of suspending agent, 5-15 parts of stabilizer, 5-10 parts of dispersant, 5-10 parts of salt pollution resistance agent, 10-15 parts of retarder, 2.5-5 parts of defoaming agent and 40-60 parts of brine.

[0005] In one or some possible embodiments, the iron powder is spherical iron powder; the purity of the spherical iron powder is not less than 96%, and the density is not less than 7.0 g / cm 3 , the average particle size is 5μm and the sphericity is >90%.

[0006] In one or some possible embodiments, the purity of the micro manganese is not less than 96%, and the density is not less than 4.8 g / cm 3 , the average particle size is 2μm.

[0007] In one or some possible embodiments, the reinforcing material is a mixture of basalt fiber, polypropylene fiber and nano-silicon dioxide in any mass ratio.

[0008] In one or some possible embodiments, the diameter of the basalt fiber is 4-6 mm, the diameter of the polypropylene fiber is 2-3 mm, and the diameter of the nano-silicon dioxide is 20-30 nm.

[0009] In one or some possible embodiments, the toughening material is selected from latex with a diameter of 100 to 150 meshes.

[0010] In one or some possible embodiments, the fluid loss agent is a polyacrylamide compound.

[0011] In one or some possible embodiments, the suspending agent is selected from a mixture of wollastonite and sepiolite in any mass ratio.

[0012] In one or some possible embodiments, the anti-salt pollution agent is selected from a potassium chloride aqueous solution with a concentration of 30% to 40%.

[0013] In one or some possible embodiments, the retarder is 2-acrylamide-2-methylpropane sulfonic acid.

[0014] In one or some possible embodiments, the defoaming agent is selected from organic ester compounds.

[0015] In one or some possible embodiments, the dispersant is an aldehyde-ketone condensation polymer compound.

[0016] In one or some possible embodiments, in the brine, the concentration of sodium chloride is 8%.

[0017] In one or some possible embodiments, the density of the cement slurry is 2.1-2.8 g / cm 3 , the compressive strength after 48h is not less than 40MPa.

[0018] As another aspect of the present invention, it relates to a method for preparing the above-mentioned high-density salt-resistant and tough cement slurry, characterized in that the method comprises the following steps:

[0019] S1. Weigh cement, iron powder and micro manganese according to their mass fractions and stir to mix;

[0020] S2, adding the mixture of the previous step into the saline solution and stirring to mix;

[0021] S3, adding the reinforcing material, micro-silicon, toughening material and dispersant in the previous step by weight, and stirring and mixing;

[0022] S4, adding the suspending agent by mass to the mixture in the previous step, stirring and mixing;

[0023] S5. Add stabilizer, fluid loss reducer, retarder and defoamer in appropriate mass fractions to the mixture in the previous step, stir and mix, and obtain high-density salt-resistant and tough cement slurry.

[0024] The beneficial effects of the above technical solution provided by the embodiment of the present application include at least:

[0025] The present invention takes close packing, micro expansion, toughness modification and other aspects as the basis for optimizing the formula, combines the high-density cement slurry with high consistency, slow strength development of cement stone, low strength and many other problems, as well as the particle size characteristics of G-grade cement, comprehensively considers the close packing design and material characteristics and other issues, determines the iron powder and micro manganese ratio, thereby improving the comprehensive performance of high-density cement slurry (stone). Nano-silicon dioxide and fiber are also added to the cement slurry prepared by the present invention, and the reinforcing material for preventing the high-temperature strength of cement stone from declining is determined. Based on the close packing and crystal phase structure optimization design, the continuous particle size distribution of ultra-high density cement slurry is realized, so that the stacking rate reaches more than 0.80, and the water demand of the system is reduced.

[0026] Compared with the conventional system, the cement slurry system of the present invention has a smaller average pore size and a smaller total porosity, and finally forms a 2.1-2.8 g / cm 3 The high-temperature resistant and high-density cement slurry system solves the problems of poor high-temperature stability of the cement slurry system and slow strength development of cement stone.

[0027] The cement slurry system prepared by the present invention has a density difference of less than 0.05 g / cm at about 200°C. 3 The 48h compressive strength is greater than 40MPa, and the 7d compressive strength is 45MPa and does not decay.

[0028] Other features and advantages of the present invention will be set forth in the description which follows, and in part will be apparent from the description, or may be learned by practicing the present invention. DETAILED DESCRIPTION

[0029] The exemplary embodiments of the present disclosure will be described in more detail below. The following are exemplary embodiments of the present disclosure, but it should be understood that the present disclosure can be implemented in various forms and should not be limited by the embodiments set forth herein. On the contrary, these embodiments are provided to enable a more thorough understanding of the present disclosure and to fully convey the scope of the present disclosure to those skilled in the art.

[0030] It should be understood that the terms described in the present invention are only for describing special embodiments and are not intended to limit the present invention. In addition, for the numerical range in the present invention, it should be understood that each intermediate value between the upper and lower limits of the scope is also specifically disclosed. Each smaller range between the intermediate value in any stated value or stated range and any other stated value or intermediate value in the described range is also included in the present invention. The upper and lower limits of these smaller ranges can be independently included or excluded in the scope.

[0031] Unless otherwise indicated, all technical and scientific terms used herein have the same meanings as commonly understood by those skilled in the art to which the invention belongs. Although the present invention describes only preferred methods and materials, any methods and materials similar or equivalent to those described herein may also be used in the implementation or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials related to the documents. In the event of a conflict with any incorporated document, the content of this specification shall prevail.

[0032] In the description of the present invention, it should be noted that the terms "include", "including", "have", "contain" and the like are open terms, meaning including but not limited to.

[0033] The present invention is further described below in conjunction with specific examples, and the protection scope of the present invention is not limited by the following examples. The sources of materials mainly involved in the examples are all conventional commercial products.

[0034] Example 1

[0035] The high-density salt-resistant and tough cement slurry provided in this embodiment includes: 100g of oil well G-grade cement, 60g of iron powder, 10g of micro manganese, 40g of reinforcing material, 5g of toughening material, 50g of micro silicon, 5g of fluid loss reducer, 5g of suspending agent, 15g of stabilizer, 5g of dispersant, 5g of salt pollution resistance agent, 10g of retarder, 3g of defoaming agent, and 60g of brine;

[0036] The high-density salt-resistant and tough cement slurry provided in this embodiment is prepared by the following steps:

[0037] (1) 100 g of oil well G grade cement, 50 g of iron powder and 10 g of micro manganese were dry mixed and stirred for 10 minutes at a stirring rate of 2000 rpm;

[0038] (2) Prepare 60 g of brine, add the dry-mixed mixture from the previous step into the brine and stir for 5 minutes at a stirring rate of 2000 rpm;

[0039] (3) Add 40 g of reinforcing material, 50 g of microsilicon, 5 g of toughening material, and 5 g of dispersant to the mixture in the previous step and stir for 5 minutes at a stirring rate of 11,000 rpm;

[0040] (4) Add 10 g of the suspending agent to the mixture in the previous step and stir at 11,000 rpm for 5 min;

[0041] (5) Add 15 g of stabilizer, 3 g of fluid loss reducer, 5 g of salt pollution inhibitor, 10 g of retarder, and 0.5 g of defoamer to the liquid in the previous step, and stir for 20 minutes at a stirring rate of 11,000 rpm;

[0042] That is 2.1g / cm 3 High-density, salt-resistant and tough cement slurry; under the conditions of 180°C and 145MPa pressure, the cement slurry has a thickening time of 207 minutes, which can meet the requirement of 126 minutes for the safe construction time of tail pipe cementing.

[0043] Example 2

[0044] The high-density salt-resistant and tough cement slurry provided in this embodiment includes: 100g of oil well G-grade cement, 260g of iron powder, 50g of micro manganese, 30g of reinforcing material, 10g of toughening material, 30g of micro silicon, 3g of fluid loss reducer, 3g of suspending agent, 5g of stabilizer, 10g of dispersant, 10g of salt pollution resistance agent, 15g of retarder, 2.5g of defoaming agent, and 40g of brine;

[0045] According to the above ratio, configure as follows:

[0046] (1) 100 g of oil well G grade cement, 260 g of iron powder and 50 g of micro manganese were dry mixed and stirred for 10 minutes at a stirring rate of 2000 rpm;

[0047] (2) Prepare 40 g of brine, add the dry-mixed mixture from the previous step into the brine and stir for 5 minutes at a stirring rate of 2000 rpm;

[0048] (3) Add 30 g of reinforcing material, 30 g of microsilicon, 10 g of toughening material, and 10 g of dispersant to the mixture in the previous step and stir for 5 minutes at a stirring rate of 11,000 rpm;

[0049] (4) Add 10 g of the suspending agent to the mixture in the previous step and stir at 11,000 rpm for 5 min;

[0050] (5) Add 5 g of stabilizer, 3 g of fluid loss reducer, 10 g of salt pollution inhibitor, 15 g of retarder, and 2.5 g of defoamer to the liquid in the previous step, and stir for 20 minutes at a stirring rate of 11,000 rpm;

[0051] You can get 2.80g / cm 3 A salt-resistant, high-density and tough cement slurry system; under the conditions of 180°C and a pressure of 145MPa, the cement slurry has a thickening time of 183 minutes, which can meet the requirement of 126 minutes for the safe construction time of tail pipe cementing.

[0052] The inventors conducted the following performance tests on the above-mentioned Examples 1 and 2 under different temperature conditions according to the relevant contents recorded in the standard GB / T 19139-2012 "Test Methods for Oil Well Cement", and recorded the test results in the following Table 1:

[0053] Table 1 Performance test results

[0054]

[0055] The inventors also selected cement slurries in the prior art as comparative examples 1 to 3 of the present invention.

[0056] Comparative Example 1

[0057] The patent number CN106244124A "Salt-resistant high-density early-strength anti-channeling oil well cement slurry" was selected, and the results are recorded in Table 2 below.

[0058] Table 2 Related properties of cement slurry

[0059]

[0060] Comparative Example 2

[0061] The patent number CN101338183A "A salt-resistant high-density cement slurry" was selected, and the results are recorded in Table 3 below.

[0062] Table 3 Related properties of cement slurry

[0063]

[0064]

[0065] Comparative Example 3

[0066] The patent number CN104293331A "High-temperature and high-density cement slurry for cementing high-temperature and high-pressure wells in oil fields and its preparation method" was selected, and the results are recorded in Table 4 below.

[0067] Table 4 Related properties of cement slurry

[0068]

[0069] It can be seen from the performance test results in Table 1 that the density of the cement slurry prepared by the present invention is 2.1-2.8 g / cm 3 Under the condition of 180℃ and higher temperature, the thickening time of cement slurry is not less than 395 minutes, the compressive strength of 48h is not less than 40MPa, the free liquid is almost zero, the water loss is less than 100ml, the cement slurry has good performance, and meets the requirements of SY / T 6544-2017 "Performance Requirements for Oil Well Cement Slurry" standard.

[0070] Combining Tables 2 and 3, it can be seen that the temperature resistance of the cement slurry system of Comparative Example 1 is only 70°C, the compressive strength of the cement slurry system of Comparative Example 2 is up to 24.3MPa at 24h, and the temperature resistance of the cement slurry system of Comparative Example 3 does not exceed 160°C, and the compressive strength at 48h is only 16.4MPa. It can be seen that compared with the cement slurries prepared in Comparative Examples 1 to 3, the cement slurry system of the present invention has higher temperature resistance and better compressive strength.

[0071] The inventors took the cement slurry prepared in Example 1 as an example to determine the compatibility of downhole fluids during cementing, so as to evaluate the effect of the mixture of cement slurry with drilling fluid and spacer fluid on the thickening time of cement slurry, so as to avoid the phenomenon of premature thickening of cement slurry when it is contaminated downhole. The test was carried out according to the downhole fluid compatibility test method recorded in GB / T 19139-2012 "Test Methods for Oil Well Cement" standard as follows:

[0072] Test 1

[0073] When the cement slurry prepared in Example 1 was mixed with the drilling fluid and the spacer fluid in a mass ratio of 7:1:2, a thickening experiment was carried out at a temperature of 180° C. and a pressure of 145 MPa;

[0074] Test 2

[0075] The cement slurry prepared in Example 1 was mixed with the spacer liquid in a mass ratio of 7:3, and a thickening experiment was carried out at a temperature of 180° C. and a pressure of 145 MPa;

[0076] The data results of Tests 1 and 2 are recorded in Table 5 below.

[0077] Table 5 Pollution evaluation results

[0078]

[0079] It can be seen from the pollution evaluation results in Table 5 that when the cement slurry prepared in Example 1 is mixed with the drilling fluid and the spacer fluid in a mass ratio of 7:1:2, at a temperature of 180°C and a pressure of 145 MPa, the thickening time of the cement slurry mixture is still not thickened at 480 minutes, which is much longer than the cementing construction time; when the cement slurry prepared in Example 1 is mixed with the spacer fluid in a mass ratio of 7:3, at a temperature of 180°C and a pressure of 145 MPa, the cement slurry mixture is not thickened at 420 minutes, which is also much longer than the cementing construction time.

[0080] This shows that the cement slurry prepared by the present invention has good compatibility with downhole fluid and will not solidify prematurely, which is conducive to safe construction.

[0081] Although the description of the present invention has been quite detailed and has been described in particular with respect to several described embodiments, it is not intended to be limited to any of these details or embodiments or any particular embodiment, so as to effectively cover the intended scope of the present invention. In addition, the present invention is described above with the embodiments foreseeable by the inventors, and its purpose is to provide a useful description, and those non-substantial changes to the present invention that are not currently foreseen may still represent equivalent changes of the present invention.

[0082] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "illustrative embodiments", "examples", "specific examples", or "some examples" means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner.

[0083] Although the embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the claims and their equivalents.

Claims

1. A high-density salt-resistant tough cement slurry, characterized in that: The cement slurry comprises the following raw materials by mass percentage: 100 parts of cement, 60-260 parts of iron powder, 10-50 parts of micro manganese, 30-40 parts of reinforcing material, 5-10 parts of toughening material, 30-50 parts of micro silicon, 3-5 parts of fluid loss reducer, 3-5 parts of suspending agent, 5-15 parts of stabilizer, 5-10 parts of dispersant, 5-10 parts of salt pollution resistance agent, 10-15 parts of retarder, 2.5-5 parts of defoaming agent and 40-60 parts of brine.

2. The cement slurry according to claim 1, characterized in that The iron powder is spherical iron powder; the purity of the spherical iron powder is not less than 96%, and the density is not less than 7.0g / cm 3 , the average particle size is 5μm and the sphericity is >90%.

3. The cement slurry according to claim 1, characterized in that The purity of the micro manganese is not less than 96%, and the density is not less than 4.8g / cm 3 , the average particle size is 2μm.

4. The cement slurry according to claim 1, characterized in that The reinforcing material is a mixture of basalt fiber, polypropylene fiber and nano silicon dioxide in any mass ratio.

5. The cement slurry according to claim 4, characterized in that The diameter of the basalt fiber is 4-6 mm, the diameter of the polypropylene fiber is 2-3 mm, and the diameter of the nano silicon dioxide is 20-30 nm.

6. The cement slurry according to claim 1, characterized in that The toughening material is selected from latex with a diameter of 100 to 150 meshes.

7. The cement slurry according to claim 1, characterized in that The fluid loss reducer is a polyacrylamide compound.

8. The cement slurry according to claim 1, characterized in that The suspending agent is selected from a mixture of wollastonite and sepiolite in any mass ratio.

9. The cement slurry according to claim 1, characterized in that: The anti-salt pollution agent is selected from a potassium chloride aqueous solution with a concentration of 30% to 40%.

10. The cement slurry according to claim 1, characterized in that The retarder is 2-acrylamide-2-methylpropane sulfonic acid.

11. The cement slurry according to claim 1, characterized in that The defoaming agent is selected from organic ester compounds.

12. The cement slurry according to claim 1, characterized in that The dispersant is an aldehyde-ketone condensation polymer compound.

13. The cement slurry according to claim 1, characterized in that In the brine, the concentration of sodium chloride was 8%.

14. The cement slurry according to any one of claims 1 to 13, characterized in that: The density of the cement slurry is 2.1-2.8 g / cm 3 , the compressive strength after 48h is not less than 40MPa.

15. A method for preparing the high-density salt-resistant and tough cement slurry according to any one of claims 1 to 14, characterized in that: The method comprises the following steps: S1. Weigh cement, iron powder and micro manganese according to their mass fractions and stir to mix; S2, adding the mixture of the previous step into the saline solution and stirring to mix; S3, adding the reinforcing material, micro-silicon, toughening material and dispersant in the previous step by weight, and stirring and mixing; S4, adding the suspending agent by mass to the mixture in the previous step, stirring and mixing; S5. Add stabilizer, fluid loss reducer, retarder and defoamer in appropriate mass fractions to the mixture in the previous step, stir and mix, and obtain high-density salt-resistant and tough cement slurry.

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