Cement strength stabilizing material, oil well cementing slurry system and application thereof

Abstract

The present application relates to the field of oil and gas well cementing engineering, and discloses a cement strength stabilizing material, an oil well cementing cement slurry system and application thereof.The cement strength stabilizing material comprises 30-80 parts by weight of a first strength stabilizing material and 20-70 parts by weight of a second strength stabilizing material; wherein the first strength stabilizing material is a mixture of quartz sand and glass powder; and the second strength stabilizing material is a mixture of at least two selected from spodumene, andalusite, olivine, leucite, garnet, pyrope, almandine, grossular, epidote, nepheline, staurolite, spinel and graphite.The cement slurry system containing the cement strength stabilizing material of the present application is suitable for both high-temperature direct forming working conditions of deep wells and super-deep wells and low-temperature forming and high-temperature service working conditions of heavy oil steam production, has good comprehensive performance, and has a broad market application prospect.

Description

Technical Field

[0001] This invention relates to the field of oil and gas well cementing engineering, specifically to a cement strength stabilizing material, an oil well cementing slurry system, and their applications. Background Technology

[0002] As oil and gas exploration continues to advance into deeper and ultra-deep formations, oil and gas drilling is encountering increasingly complex formations with rising formation temperatures and pressures. Scholars both domestically and internationally have recognized that high temperatures are a major factor affecting the strength degradation of cement stone. There exists a temperature threshold; exceeding this threshold causes a significant decrease in cement stone strength, which is extremely detrimental to cementing high-temperature wells. Strength reduction occurs when temperatures reach 110℃, and at 230℃, the cement stone may completely lose its strength.

[0003] my country has abundant heavy oil resources and uses steam injection development technology. The steam injection temperature can reach 350℃. Conventional cement sheath strength deteriorates, and after 1-2 injection cycles, it loses its interlayer sealing ability, causing water flow outside the pipe and forcing it to be scrapped. In some cases, steam "ground leakage" occurs, which seriously affects safety.

[0004] Therefore, there is an urgent need for a material that can maintain the strength and porosity parameters of cement stone under ultra-high temperature (200-350℃) conditions for a long time, so that the cement stone can adapt to the high temperature cementing requirements of deep or heavy oil steam injection. Summary of the Invention

[0005] The purpose of this invention is to overcome the problems of reduced cement stone strength and increased permeability caused by the transformation of hydration products under high temperature conditions in existing sand-added oil well cement, and to provide a cement strength stabilizing material, an oil well cementing slurry system and its application.

[0006] To achieve the above objectives, a first aspect of the present invention provides a cement strength stabilizing material, the cement strength stabilizing material comprising: 30-80 parts by weight of a first strength stabilizing material and 20-70 parts by weight of a second strength stabilizing material; wherein...

[0007] The first strength-stabilizing material is a mixture of quartz sand and glass powder;

[0008] The second strength-stabilizing material is a mixture of at least two selected from spodumene, andalusite, olivine, leucite, garnet, pyrope, almandine, garnet, beryl, nepheline, staurolite, spinel, and graphite.

[0009] A second aspect of the present invention provides an oil well cement slurry system, wherein the cement slurry system includes the cement strength stabilizing material provided by the present invention.

[0010] A third aspect of the present invention provides an application of the cement slurry system provided by the present invention in cementing of high-temperature deep wells or heavy oil steam thermal recovery wells.

[0011] The beneficial effects of the present invention through the above technical solution are as follows:

[0012] The cement strength stabilizing material of this invention, on the one hand, provides sufficient silicon source for the early and mid-to-long-term hydration of cement through the synergistic effect of crystalline and amorphous silicon, inhibiting the formation of dicalcium silicate hydrate and promoting the formation of calcareous silicate; on the other hand, it uses a second high-temperature strength stabilizing material to inhibit the coarsening and deterioration of calcareous silicate, promoting its transformation into a dense, long-term stable magnesium-aluminum-iron-calcium silicate mineral, thereby maintaining the long-term stability of cement stone strength and porosity parameters. Whether in low-temperature molding and high-temperature curing environments (molding at 40-80℃ and curing at 300-350℃), or in high-temperature direct molding environments (molding and curing at 200-240℃), the cement stone formed after molding by the cement slurry system provided by this invention exhibits high compressive strength, which continues to increase steadily with curing time.

[0013] The method for preparing the cement strength stabilizing material of the present invention is simple and does not require high-temperature calcination, hydrothermal treatment, acid-base modification and other operations; it can be prepared by direct mixing and stirring.

[0014] The cement slurry system of this invention is suitable for both high-temperature direct molding environments such as deep wells and ultra-deep wells, and low-temperature molding and high-temperature service environments such as heavy oil steam extraction. The cement slurry density and thickening time are adjustable, with good flow properties, low water loss, high strength, and no long-term degradation, fully meeting the technical requirements of on-site cementing construction. Detailed Implementation

[0015] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0016] The first aspect of this invention provides a cement strength stabilizing material, the cement strength stabilizing material comprising: 30-80 parts by weight of a first strength stabilizing material and 20-70 parts by weight of a second strength stabilizing material; wherein,

[0017] The first strength-stabilizing material is a mixture of quartz sand and glass powder;

[0018] The second strength-stabilizing material is a mixture of at least two selected from spodumene, andalusite, olivine, leucite, garnet, pyrope, almandine, garnet, beryl, nepheline, staurolite, spinel, and graphite.

[0019] On the one hand, the first strength stabilizing material in the cement strength stabilizing material of the present invention is a mixture of quartz sand and glass powder, wherein the quartz sand is crystalline silicon and the glass powder is amorphous silicon. Through the synergistic effect of crystalline and amorphous silicon, the first strength stabilizing material provides sufficient silicon source for the early and mid-to-long-term hydration of cement, inhibiting the formation of dicalcium silicate hydrate and promoting the transformation of hydration products from hydrated calcium silicate to calcium silicate silicate, thereby suppressing the phenomenon of decreased strength and increased permeability in cement stone. On the other hand, the use of the second strength stabilizing material can inhibit the coarsening and deterioration of calcium silicate silicate, promoting its transformation into a dense, long-term stable magnesium-aluminum-iron-calcium silicate mineral, thereby maintaining the long-term stability of cement stone strength and porosity / permeability parameters. The first and second strength stabilizing materials play a good synergistic role in maintaining the strength and permeability of cement stone.

[0020] According to the present invention, preferably, the average particle size of the quartz sand is 3-198 μm, and the average particle size of the glass powder is 3-198 μm.

[0021] Furthermore, the average particle size of the quartz sand is 90-110 μm, and the average particle size of the glass powder is 30-60 μm.

[0022] According to the present invention, preferably, the weight ratio of the quartz sand and the glass powder is (0.2-5):1, more preferably (1-2):1.

[0023] According to the present invention, preferably, the average particle size of the second strength stabilizing material is 10-165 μm, more preferably 20-80 μm. If the average particle size of the second strength stabilizing material is too small, the resulting slurry will be too viscous; if the average particle size is too large, the slurry will settle.

[0024] According to the present invention, preferably, the second strength stabilizing material is a mixture of spodumene, leucite and graphite, or a mixture of andalusite and garnet, or a mixture of nepheline, spinel and graphite.

[0025] According to the present invention, preferably, the second strength stabilizing material is a mixture of spodumene with an average particle size of 30-60 μm, leucite with an average particle size of 50-80 μm, and graphite with an average particle size of 20-50 μm; or a mixture of andalusite with an average particle size of 30-60 μm and garnet with an average particle size of 30-60 μm; or a mixture of nepheline with an average particle size of 30-60 μm, spinel with an average particle size of 50-80 μm, and graphite with an average particle size of 20-50 μm.

[0026] According to the present invention, preferably, when the second strength stabilizing material is a mixture of spodumene, leucite and graphite, the weight ratio of spodumene, leucite and graphite is (7-14):(7-14):1;

[0027] When the second strength-stabilizing material is a mixture of andalusite and garnet, the weight ratio of andalusite to garnet is (0.5-2):1;

[0028] When the second strength-stabilizing material is a mixture of nepheline, spinel and graphite, the weight ratio of nepheline, spinel and graphite is (7-14):(7-14):1.

[0029] According to the present invention, preferably, the cement strength stabilizing material further includes 10 parts by weight or less of reinforcing and toughening materials.

[0030] According to the present invention, preferably, the reinforcing and toughening material is selected from carbon nanotubes and / or fibers.

[0031] According to the present invention, preferably, the reinforcing and toughening material is selected from carbon nanotubes with an average diameter of 20-30 nm and an average length of 0.5-30 μm; and / or, selected from fibers with an average diameter of 5-10 μm and an average length of 1-15 mm.

[0032] According to the present invention, preferably, the fiber is selected from carbon fiber and / or basalt fiber.

[0033] According to the present invention, preferably, the fiber is selected from carbon fiber with an average diameter of 5-8 μm and an average length of 1-15 mm; and / or, from basalt fiber with an average diameter of 5-10 μm and an average length of 3-15 mm.

[0034] According to the present invention, preferably, the cement strength stabilizing material comprises: 40-70 parts by weight of a first strength stabilizing material, 30-60 parts by weight of a second strength stabilizing material, and 0.2-1 parts by weight of a reinforcing and toughening material.

[0035] According to the present invention, preferably, in the cement strength stabilizing material, the weight ratio of the first strength stabilizing material to the second strength stabilizing material is (1-2.3):1.

[0036] According to the present invention, preferably, the method for preparing the cement strength stabilizing material includes the following steps: mixing the first strength stabilizing material and the second strength stabilizing material to obtain a first mixed material; and then mixing the first mixed material with the reinforcing and toughening material to obtain the cement strength stabilizing material.

[0037] A second aspect of the present invention provides an oil well cement slurry system, wherein the cement slurry system includes the cement strength stabilizing material provided by the present invention.

[0038] According to the present invention, preferably, the cement slurry system comprises the following components in parts by weight: 100 parts of oil well cement, 35-100 parts of the cement strength stabilizing material, 4-10 parts of a water loss reducing agent, 1-12 parts of a retarder, 0.1-2 parts of a defoamer, and 30-100 parts of water.

[0039] Furthermore, the cement slurry system comprises the following components in parts by weight: 100 parts of oil well cement, 55-95 parts of the cement strength stabilizing material, 7-10 parts of a water loss reducing agent, 2-11 parts of a retarder, 0.4-0.6 parts of a defoamer, and 40-90 parts of water.

[0040] According to the present invention, preferably, the oil well cement is Grade G oil well cement.

[0041] According to the present invention, preferably, the water loss reducing agent is a polymer.

[0042] According to the present invention, preferably, the polymer is a copolymer comprising structural units derived from 2-acrylamido-2-methylpropanesulfonic acid and structural units derived from acrylamide.

[0043] This invention does not impose any particular restrictions on the weight-average molecular weight of the polymer, or on the weight ratio of structural units derived from 2-acrylamido-2-methylpropanesulfonic acid to structural units derived from acrylamide in the polymer, as long as the performance as a water loss reducing agent is met. For example, a copolymer of AMPS and acrylamide, purchased from the Texas Continental Shelf and brand name SCF-J, can be used.

[0044] According to the present invention, preferably, the retarder is selected from 2-acrylamido-2-methylpropanesulfonic acid copolymer (AMPS copolymer) and / or inorganic acid, and more preferably AMPS copolymer. The present invention does not impose any particular restrictions on the weight-average molecular weight of the AMPS copolymer or the proportion of structural units contained in the AMPS copolymer, as long as it meets the performance requirements for use as a retarder. For example, AMPS copolymer with the brand name SCR, purchased from the Texas Continental Shelf, can be used.

[0045] According to the present invention, preferably, the defoamer is selected from silicone defoamers and / or tributyl phosphate defoamers, and more preferably from silicone defoamers.

[0046] According to the present invention, preferably, the cement slurry system further includes: less than 2 parts by weight of dispersant, preferably 0.4-0.6 parts by weight.

[0047] Preferably, the dispersant is selected from polycarboxylic acid dispersants and / or ketaldehyde condensates, and more preferably from polycarboxylic acid dispersants. This invention does not impose particular limitations on the weight-average molecular weight of the polycarboxylic acid dispersant, as long as it meets the performance requirements for use as a dispersant. For example, a polycarboxylic acid dispersant with the brand name SCD, purchased from the Texas Continental Shelf, can be used.

[0048] According to the present invention, preferably, the cement slurry system further includes: less than 3 parts by weight of a suspension stabilizer. The amount of suspension stabilizer added is adjusted according to the density of the cement slurry system.

[0049] According to the present invention, preferably, the suspension stabilizer is selected from attapulgite and / or nano-silica, and more preferably a mixture of attapulgite and nano-silica.

[0050] According to the present invention, preferably, the weight ratio of the attapulgite clay and nano-silica is (2-4):1.

[0051] According to the present invention, preferably, the cement slurry system further includes: 300 parts by weight or less of a density regulator. The amount of density regulator added is adjusted according to the density of the cement slurry system.

[0052] According to the present invention, preferably, the density regulator is selected from at least one of iron ore powder, iron powder, manganese powder, barite, fly ash, slag and glass microspheres, and preferably iron ore powder.

[0053] In this invention, the role of the suspension stabilizer is to maintain the solid particles in the cement slurry system in a suspended state and prevent sedimentation; the role of the density adjuster is to adjust the density of the cement slurry system, when the density of the cement slurry system is lower than 1.85 g / cm³. 3 or higher than 1.95 g / cm 3 Density regulators need to be added, and optionally suspension stabilizers, to achieve a density below 1.85 g / cm³. 3 or higher than 1.95 g / cm 3 The cement slurry system.

[0054] According to one specific embodiment of the present invention, the cement slurry system comprises the following components in parts by weight: 100 parts of oil well cement, 55-95 parts of the cement strength stabilizing material, less than 300 parts by weight of density regulator, less than 3 parts by weight of suspension stabilizer, 7-10 parts of water loss reducing agent, 2-11 parts of retarder, 0.4-0.6 parts of dispersant, 0.4-0.6 parts of defoamer, and 40-90 parts of water.

[0055] According to the present invention, preferably, when the cement slurry system has a density of 1.88-1.9 g / cm³, 3When the cement slurry system is solidified and cured at 200-350℃ for 28 days, the compressive strength is greater than or equal to 25MPa.

[0056] According to a preferred embodiment of the present invention, when the cement slurry system has a density of 1.88-1.9 g / cm³, 3 When the cement slurry system is solidified and cured at 200-350℃ for 28 days, the compressive strength is greater than or equal to 40MPa.

[0057] A third aspect of this invention provides an application of the cement slurry system provided by this invention in high-temperature deep well cementing. Whether in a low-temperature molding and high-temperature curing environment (molding at 40-80℃ and curing at 300-350℃), or a high-temperature direct molding environment (molding and curing at 200-240℃), the cement stone formed by the cement slurry system provided by this invention exhibits high compressive strength, which continues to increase steadily with curing time.

[0058] The present invention will be described in detail below through examples. Unless otherwise specified, all methods used in the following examples are conventional; the reagents and materials used are commercially available unless otherwise specified. The reagents and assay methods involved in the following examples and comparative examples are as follows:

[0059] The oil well cement was Grade G cement purchased from Jia Hua Company;

[0060] Prepared according to GB / T 19139-2012 standard, with a density of 1.9-2.25 g / cm³. 3 Cement grout system;

[0061] The density of the cement paste system was determined according to the method specified in GB / T 19139-2012;

[0062] The fluidity of the cement slurry system was determined according to the method specified in GB / T 8077-2012;

[0063] The API water loss of the cement slurry system was determined according to the method specified in GB / T 19139-2012;

[0064] The thickening time of the cement slurry system was determined according to the method specified in GB / T 19139-2012;

[0065] The compressive strength of the cement grout system was determined according to the method specified in GB / T 19139-2012.

[0066] The following preparation examples illustrate the preparation of cement strength-stabilized materials.

[0067] Preparation Example 1

[0068] 60 parts by weight of a first high-temperature strength stabilizing material (a mixture of quartz sand with an average particle size of 100 μm and glass powder with an average particle size of 47 μm in a 1:1 weight ratio) and 40 parts by weight of a second high-temperature strength stabilizing material (a mixture of spodumene with an average particle size of 47 μm, leucite with an average particle size of 74 μm, and graphite with an average particle size of 25 μm in a 10:10:1 weight ratio) with an average particle size of 59 μm were mixed in a mixer and stirred until homogeneous and no false particles were observed to the naked eye. Then, the resulting mixture was mixed with 0.2 parts by weight of a reinforcing and toughening material (multi-walled carbon nanotubes with an average diameter of 25 nm and an average length of 15 μm) and stirred in a mixer until homogeneous and no agglomerated particles were observed to the naked eye. This yielded the cement strength stabilizing material, denoted as S1.

[0069] Preparation Example 2

[0070] 60 parts by weight of the first high-temperature strength stabilizing material (a 1:1 mixture of quartz sand with an average particle size of 100 μm and glass powder with an average particle size of 47 μm) and 40 parts by weight of the second high-temperature strength stabilizing material (a 1:1 mixture of andalusite with an average particle size of 47 μm and garnet with an average particle size of 47 μm) were mixed in a mixer and stirred until homogeneous and no false particles were observed to the naked eye. Then, the resulting mixture was mixed with 1 part by weight of the reinforcing and toughening material (carbon fiber with an average diameter of 6 μm and an average length of 8 mm) and stirred in a mixer until homogeneous and no agglomerated particles were observed to the naked eye. The resulting cement strength stabilizing material was thus obtained and denoted as S2.

[0071] Preparation Example 3

[0072] 60 parts by weight of the first high-temperature strength stabilizing material (a mixture of quartz sand with an average particle size of 100 μm and glass powder with an average particle size of 47 μm in a weight ratio of 2:1) and 40 parts by weight of the second high-temperature strength stabilizing material (a mixture of nepheline with an average particle size of 47 μm, spinel with an average particle size of 74 μm, and graphite with an average particle size of 25 μm in a weight ratio of 10:10:1) with an average particle size of 59 μm are mixed in a mixer and stirred until homogeneous and no false particles are observed by the naked eye. Then, the resulting mixture is mixed with 1 part by weight of the reinforcing and toughening material (basalt fiber with an average diameter of 7 μm and an average length of 8 mm) in a mixer and stirred until homogeneous and no agglomerated particles are observed by the naked eye. The resulting cement strength stabilizing material is designated as S3.

[0073] Preparation Example 4

[0074] Cement strength stabilizing material was prepared according to the method of Preparation Example 2, except that the weight parts of the first high-temperature strength stabilizing material and the second high-temperature strength stabilizing material were different. Specifically, the weight parts of the first strength stabilizing material and the second strength stabilizing material in the cement strength stabilizing material were 30 parts and 70 parts, respectively. The resulting cement strength stabilizing material was denoted as S4.

[0075] Preparation Example 5

[0076] Cement strength stabilizing material was prepared according to the method of Preparation Example 2, except that the average particle size of the quartz sand and glass powder was different. Specifically, the average particle size of the quartz sand was 47 μm, and the average particle size of the glass powder was 100 μm. The resulting cement strength stabilizing material was denoted as S5.

[0077] Preparation Example 6

[0078] Cement strength stabilizing material was prepared according to the method of Preparation Example 2, except that the weight ratio of quartz sand to glass powder was 3:1. The resulting cement strength stabilizing material was denoted as S6.

[0079] Preparation Example 7

[0080] Cement strength stabilizing material was prepared according to the method of Preparation Example 2, except that the weight ratio of quartz sand to glass powder was 6:1. The resulting cement strength stabilizing material was denoted as S7.

[0081] Preparation Example 8

[0082] The cement strength stabilizing material was prepared according to the method of Preparation Example 2, except that the second strength stabilizing material was a mixture of spodumene with an average particle size of 47 μm, andalusite with an average particle size of 47 μm, and graphite with an average particle size of 25 μm in a weight ratio of 10:10:1, resulting in a second high-temperature strength stabilizing material with an average particle size of 46 μm. The cement strength stabilizing material obtained was denoted as S8.

[0083] Preparation Example 9

[0084] Cement strength stabilizing materials were prepared according to the method of Preparation Example 2, except that the weight ratio of andalusite to garnet in the second high-temperature strength stabilizing material was 3:1, resulting in a second high-temperature strength stabilizing material with an average particle size of 47 μm. The obtained cement strength stabilizing material is denoted as S9.

[0085] Preparation Example 10

[0086] The cement strength stabilizing material was prepared according to the method of Preparation Example 2, except that the average particle size of andalusite and garnet in the second high-temperature strength stabilizing material was different. Specifically, andalusite with an average particle size of 75 μm and garnet with an average particle size of 100 μm were selected to obtain a second high-temperature strength stabilizing material with an average particle size of 88 μm. The cement strength stabilizing material obtained was denoted as S10.

[0087] Preparation Example 11

[0088] Cement strength stabilizing material was prepared according to the method of Preparation Example 2, except that the second strength stabilizing material was andalusite with an average particle size of 47 μm. The obtained cement strength stabilizing material is denoted as S11.

[0089] Preparation Example 12

[0090] Cement strength stabilizing material was prepared according to the method of Preparation Example 2, except that the weight parts of the first strength stabilizing material, the second strength stabilizing material, and the reinforcing and toughening material were different. Specifically, the weight parts of the first strength stabilizing material, the second strength stabilizing material, and the reinforcing and toughening material in the cement strength stabilizing material were 80 parts, 20 parts, and 0.2 parts, respectively. The resulting cement strength stabilizing material was denoted as S12.

[0091] Preparation Example 13

[0092] Cement strength stabilizing material was prepared according to the method of Preparation Example 2, except that the weight parts of the first strength stabilizing material and the second strength stabilizing material were 40 parts and 60 parts, respectively. The resulting cement strength stabilizing material is denoted as S13.

[0093] Preparation Example 14

[0094] Cement strength stabilizing material was prepared according to the method of Preparation Example 2, except that the weight parts of the first strength stabilizing material and the second strength stabilizing material were 90 parts and 10 parts, respectively. The resulting cement strength stabilizing material is denoted as S14.

[0095] The following examples illustrate the preparation of oil well cement slurry systems.

[0096] Examples 1-13

[0097] The cement slurry system, manufactured under low-temperature molding and high-temperature curing conditions (molded at 50℃ and cured at 350℃), comprises the following components by weight: 100 parts of Grade G cement, 80 parts of cement strength stabilizers S1-S13, 3 parts of retarder, 8 parts of water loss reducer, 0.5 parts of defoamer, and 52-65 parts of water (the densities of cement strength stabilizers S1-S13 vary, and water is used to adjust the density of the cement slurry system), yielding a density of 1.9 g / cm³. 3 The cement slurry system.

[0098] In a high-temperature direct molding environment (molding and curing at 240℃), the cement slurry system comprises the following components by weight: 100 parts of Grade G cement, 80 parts of cement strength stabilizer S1-S13, 10 parts of retarder, 8 parts of water loss reducer, 0.5 parts of defoamer, and 45-58 parts of clean water, yielding a density of 1.9 g / cm³. 3 The cement slurry system.

[0099] The retarder is an AMPS multi-component copolymer, purchased from the Texas Continental Shelf, and its brand name is SCR.

[0100] The water loss reducer is a copolymer of AMPS and acrylamide, purchased from the Texas Continental Shelf, brand name SCF-J;

[0101] The defoamer is a polysiloxane silicone defoamer, purchased from the Texas Continental Shelf, brand name SCFD-2.

[0102] Examples 14-15

[0103] The cement slurry system, produced under low-temperature molding and high-temperature curing conditions (molded at 50℃ and cured at 350℃), comprises the following components by weight: 100 parts G-grade cement, 80 parts cement strength stabilizer (S2, S4), 80 parts density modifier (iron ore powder), 1 part suspension stabilizer (attapulgite clay and nano-silica mixed in a 3:1 weight ratio), 3 parts retarder, 9 parts water loss reducer, 0.5 parts dispersant, 0.5 parts defoamer, and 51-62 parts clean water, yielding a density of 2.25 g / cm³. 3 The cement slurry system.

[0104] In a high-temperature direct molding environment (molding and curing at 240℃), the cement slurry system comprises the following components by weight: 100 parts of Grade G cement, 80 parts of cement strength stabilizer (S2, S4), 80 parts of density modifier (iron ore powder), 2 parts of suspension stabilizer (attapulgite clay and nano-silica mixed in a 3:1 weight ratio), 10 parts of retarder, 9 parts of water loss reducer, 0.5 parts of dispersant, 0.5 parts of defoamer, and 44-55 parts of water, yielding a density of 2.25 g / cm³. 3 The cement slurry system.

[0105] The dispersant was a polycarboxylic acid dispersant purchased from the Texas Continental Shelf, brand name SCD; the retarder, water loss reducer and defoamer were the same as in Example 1.

[0106] Comparative Example 1

[0107] The cement slurry system was prepared according to the method of Example 2, except that cement strength stabilizing material S14 was used instead of an equal mass of cement strength stabilizing material S2. The cement slurry system was thus obtained.

[0108] Comparative Example 2

[0109] The cement slurry system was prepared according to the method in Example 2, except that quartz sand with an average particle size of 100 μm was used instead of an equal mass of cement strength stabilizing material S2. The cement slurry system was thus obtained.

[0110] Comparative Example 3

[0111] The cement slurry system was prepared according to the method of Example 14, except that cement strength stabilizing material S14 was used instead of an equal mass of cement strength stabilizing material S2. The cement slurry system was thus obtained.

[0112] Comparative Example 4

[0113] The cement slurry system was prepared according to the method of Example 14, except that quartz sand with an average particle size of 100 μm was used instead of an equal mass of cement strength stabilizing material S2. The cement slurry system was thus obtained.

[0114] Test case

[0115] The density and fluidity of the cement slurry systems prepared in each embodiment and comparative example under high-temperature direct molding environment (molding and curing at 240℃) at room temperature, as well as the API water loss and thickening time at 220℃, were measured respectively. The results are shown in Table 1. The development of compressive strength of the formed cement stone under low-temperature molding, high-temperature curing environment (molding at 50℃ and curing at 350℃), and high-temperature direct molding environment are shown in Table 2.

[0116] Table 1

[0117]

[0118]

[0119] Table 2

[0120]

[0121] Note: In low-temperature molding and high-temperature curing environments, the molding and curing pressures are both 21 MPa; in high-temperature direct molding environments, the molding and curing pressures are both 21 MPa.

[0122] Table 1 shows that the cement slurry system of the present invention exhibits good overall performance, meeting the requirements for cementing operations in ultra-high temperature deep wells or heavy oil wells. Table 2 shows that in Comparative Examples 2 and 4, where quartz sand was used as the cement strength stabilizing material, strength degradation occurred under high-temperature conditions regardless of whether the environment was low-temperature molding, high-temperature curing, or high-temperature direct molding. Using the cement strength stabilizing material of the present invention, the cement stone strength is high and continuously and steadily increases under both service environments.

[0123] Furthermore, Examples 4 and 12 changed the weight proportions of each component in the cement strength stabilizing material; Example 5 changed the average particle size of quartz sand and glass powder; Examples 6 and 7 changed the weight ratio of quartz sand and glass powder; Examples 8 and 11 changed the composition of the second strength stabilizing material; Example 9 changed the weight ratio of andalusite and garnet in the second high-temperature strength stabilizing material; Example 10 changed the average particle size of the second high-temperature strength stabilizing material; and Example 13 changed the ratio of the first and second strength stabilizing materials. Compared with Example 2, the strength of the cement stone decreased regardless of whether it was in a low-temperature molding, high-temperature curing, or high-temperature direct molding environment, but the strength of the cement stone continued to increase after curing. This indicates that the proportions of each component in the cement strength stabilizing material, the average particle size and weight ratio of quartz sand and glass powder, and the composition, component ratio, and average particle size of the second strength stabilizing material all have a certain impact on the strength of the obtained cement stone.

[0124] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A cement strength stabilizing material, characterized in that, The cement strength stabilizing material comprises: 30-80 parts by weight of a first strength stabilizing material and 20-70 parts by weight of a second strength stabilizing material; wherein... The first strength-stabilizing material is a mixture of quartz sand and glass powder; The weight ratio of the quartz sand to the glass powder is (1-2):1; The second strength-stabilizing material is a mixture of spodumene, leucite and graphite, or a mixture of andalusite and garnet, or a mixture of nepheline, spinel and graphite. When the second strength stabilizing material is a mixture of spodumene, leucite and graphite, the weight ratio of spodumene, leucite and graphite is (7-14):(7-14):1; When the second strength-stabilizing material is a mixture of andalusite and garnet, the weight ratio of andalusite to garnet is (0.5-2):1; When the second strength-stabilizing material is a mixture of nepheline, spinel and graphite, the weight ratio of nepheline, spinel and graphite is (7-14):(7-14):

1.

2. The cement strength stabilizing material according to claim 1, characterized in that, The average particle size of the quartz sand is 3-198 μm; the average particle size of the glass powder is 3-198 μm.

3. The cement strength stabilizing material according to claim 2, characterized in that, The average particle size of the quartz sand is 90-110 μm; the average particle size of the glass powder is 30-60 μm.

4. The cement strength stabilizing material according to any one of claims 1-3, characterized in that, The average particle size of the second strength-stabilizing material is 10-165 μm.

5. The cement strength stabilizing material according to claim 4, characterized in that, The average particle size of the second strength-stabilizing material is 20-80 μm.

6. The cement strength stabilizing material according to any one of claims 1-3, characterized in that, The second strength-stabilizing material is a mixture of spodumene with an average particle size of 30-60 μm, leucite with an average particle size of 50-80 μm, and graphite with an average particle size of 20-50 μm; or a mixture of andalusite with an average particle size of 30-60 μm and garnet with an average particle size of 30-60 μm; or a mixture of nepheline with an average particle size of 30-60 μm, spinel with an average particle size of 50-80 μm, and graphite with an average particle size of 20-50 μm.

7. The cement strength stabilizing material according to any one of claims 1-3, characterized in that, The cement strength stabilizing material also includes less than 10 parts by weight of reinforcing and toughening materials; And / or, in the cement strength stabilizing material, the weight ratio of the first strength stabilizing material to the second strength stabilizing material is (1-2.3):

1.

8. The cement strength stabilizing material according to claim 7, characterized in that, The reinforcing and toughening material is selected from carbon nanotubes and / or fibers; And / or, the cement strength stabilizing material comprises: 40-70 parts by weight of a first strength stabilizing material, 30-60 parts by weight of a second strength stabilizing material, and 0.2-1 parts by weight of a reinforcing and toughening material.

9. The cement strength stabilizing material according to claim 8, characterized in that, The carbon nanotubes have an average diameter of 20-30 nm and an average length of 0.5-30 μm; the fibers have an average diameter of 5-10 μm and an average length of 1-15 mm. And / or, the fiber is selected from carbon fiber and / or basalt fiber.

10. An oil well cementing slurry system, characterized in that, The cement slurry system includes the cement strength stabilizing material as described in any one of claims 1-9.

11. The cement slurry system according to claim 10, characterized in that, The cement slurry system comprises the following components in parts by weight: 100 parts of oil well cement, 35-100 parts of the cement strength stabilizing material, 4-10 parts of water loss reducing agent, 1-12 parts of retarder, 0.1-2 parts of defoamer, and 30-100 parts of water.

12. The cement slurry system according to claim 11, characterized in that, The water loss reducing agent is a polymer; And / or, the retarder is selected from 2-acrylamido-2-methylpropanesulfonic acid multi-polymer and / or inorganic acids; And / or, the defoamer is selected from silicone defoamers and / or tributyl phosphate defoamers; And / or, the cement slurry system further includes: less than 2 parts by weight of a dispersant.

13. The cement slurry system according to claim 12, characterized in that, The retarder is a 2-acrylamido-2-methylpropanesulfonic acid multi-component copolymer; And / or, the defoamer is an organosilicon defoamer.

14. The cement slurry system according to claim 12, characterized in that, The polymer is a copolymer comprising structural units derived from 2-acrylamido-2-methylpropanesulfonic acid and structural units derived from acrylamide; And / or, the retarder is a 2-acrylamido-2-methylpropanesulfonic acid multi-component copolymer; And / or, the defoamer is an organosilicone defoamer; And / or, the dispersant is selected from polycarboxylic acid dispersants and / or ketaldehyde condensates.

15. The cement slurry system according to claim 14, characterized in that, The dispersant is a polycarboxylic acid dispersant.

16. The cement slurry system according to any one of claims 10-15, characterized in that, The cement slurry system also includes: less than 3 parts by weight of suspension stabilizer.

17. The cement slurry system according to claim 16, characterized in that, The suspension stabilizer is selected from attapulgite and / or nano-silica.

18. The cement slurry system according to claim 17, characterized in that, The suspension stabilizer is a mixture of attapulgite and nano-silica.

19. The cement slurry system according to claim 17, characterized in that, The weight ratio of the attapulgite clay to nano-silica is (2-4):

1.

20. The cement slurry system according to any one of claims 10-15 and 17-19, characterized in that, The cement slurry system also includes: less than 300 parts by weight of density regulator.

21. The cement slurry system according to claim 20, characterized in that, The density regulator is selected from at least one of iron ore powder, iron powder, manganese powder, barite, fly ash, slag and glass microspheres.

22. The cement slurry system according to claim 21, characterized in that, The density regulator is iron ore powder.

23. The cement slurry system according to any one of claims 10-15, 17-19, 21, and 22, characterized in that, When the cement slurry system has a density of 1.88-1.9 g / cm³ 3 When the cement slurry system is solidified and cured at 200-350℃ for 28 days, the compressive strength is greater than or equal to 25MPa.

24. The cement slurry system according to claim 23, characterized in that, When the cement slurry system has a density of 1.88-1.9 g / cm³ 3 When the cement slurry system is solidified and cured at 200-350℃ for 28 days, the compressive strength is greater than or equal to 40MPa.

25. The application of a cement slurry system according to any one of claims 10-24 in cementing high-temperature deep wells or heavy oil steam thermal recovery wells.

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