High-temperature cement reinforcing agent, high-temperature-resistant cement paste for oil well and application of high-temperature-resistant cement paste

Abstract

The invention relates to a cement high-temperature reinforcing agent, high-temperature-resistant cement paste for an oil well and application of the cement paste. The cement high-temperature reinforcing agent comprises hydrophobic silicon dioxide, ethyl sulfate, silazane and epoxy resin. The high-temperature-resistant cement paste for the oil well comprises G-grade oil well cement, calcium carbonate powder, alumina powder, ferric oxide, a cement high-temperature reinforcing agent, auxiliary materials and water, the mud high-temperature reinforcing agent / high-temperature-resistant cement paste for the oil well is applied to the oil well with the temperature of 150-250 DEG C. The cement paste has the beneficial effects that when the cement paste is introduced into a high-temperature stratum with the temperature of 150-230 DEG C, the initial hydration degree of the cement paste is low, and the cement paste is gradually hydrated and solidified as time goes by; the solidification mechanical property after hydration is good; the hydration speed of the cement paste when the cement paste is introduced into a high-temperature stratum at 150-230 DEG C can be controlled to a certain extent, and the control effect is good.

Description

Technical Field

[0001] The invention relates to the technical field of oil well cement, in particular to a cement high temperature enhancer, a high temperature resistant cement slurry for oil wells and applications thereof. Background Art

[0002] Oil well cement is often used for cementing oil wells. Since the main component of cement is silicate cement clinker, when it is mixed with water, it will react with water (hydration reaction); as the temperature rises, the hydration reaction will become more and more intense. Studies have found that the hydration reaction rate of cement increases almost geometrically for every 10°C increase in temperature.

[0003] In formation oil wells, the temperature is mostly between 50 and 120°C, and some even reach 120 to 225°C. When used (such as cementing), the cement hydration speed is too fast, which affects the fluidity of the cement. At present, for cement used in high-temperature formation oil wells, quartz sand is usually added to reduce the silicon-calcium ratio of the cement slurry system, thereby delaying hydration and achieving high temperature resistance (relatively difficult to hydrate at high temperatures). However, this will affect the mechanical properties of the cement after hydration.

[0004] There are many types of cement at present, such as silica cement, alumina cement, and alumina-ferric oxide cement with different proportions. When hydrating, CaO-SiO2-H2O colloid / CaO-Fe2O3-H2O colloid and Ca(OH)2 crystal / CaO-Al2O3-H2O crystal are produced. From the principle of cement hydration, it can be known that cement hydration is inseparable from water. If the combination of H2O and CaO·SiO2, or the combination of H2O and 2CaO·SiO2, or the combination of H2O and CaO·Al2O3, or the combination of H2O and CaO·Al2O3·Fe2O3 can be slowed down, can the hydration reaction be delayed?

[0005] Based on the above ideas, our company has conducted corresponding research and development and designed a cement high-temperature enhancer and a high-temperature resistant cement slurry system (hydrophobic silica is used to replace the normal silica in cement, and the hydrophobic silica is proportioned with certain auxiliary agents - so that it has the function of "being able to mix with water to a certain extent without floating on the water surface", and it can gradually destroy its hydrophobicity under high-temperature strata and become hydrophilic / turn into normal silica, thereby achieving hydration). Summary of the invention

[0006] The purpose of the present invention is to overcome the shortcomings of the prior art and provide a cement high temperature enhancer, a high temperature resistant cement slurry for oil wells and their applications, which solves the problem that when cement slurry for oil wells delays cement hydration by adding silica, it cannot have the strength of cement after solidification, and the problem of delaying hydration difference.

[0007] It should be noted that when cement slurry is introduced into an oil well in a high-temperature formation, the cement slurry is very easy to hydrate and solidify, resulting in poor fluidity of the cement in the high-temperature formation, thus affecting the effect of cement use. A common method is to add a retarder to the cement; however, retarders are generally suitable for formations with a lower temperature of 50℃-90℃, and the effect of general retarders is extremely limited for formations above 150℃. Therefore, for high-temperature formations above 150℃: some companies choose to change the ratio of CaO to the corresponding SiO2 / Al2O3 to achieve this, such as reducing the amount of CaO and increasing the amount of SiO2 / Al2O3 - this hydration effect is delayed to a certain extent, but the mechanical properties of the cement in the well after solidification do not meet the requirements (so some materials to improve the mechanical properties are added, but no matter how they are added, the amount of solidified cement produced is small due to the reduction in the amount of CaO - making the cementing or plugging effect not particularly ideal).

[0008] However, this solution does not keep CaO and silica (it is easy to think of Al2O3 as a replacement in this field), but modifies silica and adds auxiliary agents, so that silica does not react with CaO during the flow of cement slurry in the oil well formation. As time goes by, the properties of silica gradually change - so that it can react with CaO. Since the amount of CaO and silica is consistent with that of normal cement slurry, it can perform good cementing / plugging of the oil well after solidification.

[0009] The purpose of the present invention is achieved through the following technical solutions: In the first aspect, a cement high-temperature enhancer is provided, comprising the following components: hydrophobic silica, ethyl sulfate, monosilazane, and epoxy resin.

[0010] Furthermore, when preparing the cement high-temperature enhancer, monosilazane is mixed with a portion of epoxy resin of equal weight, and then hydrophobic silica, ethyl sulfate, and the remaining epoxy resin are added and mixed.

[0011] Furthermore, the cement high temperature enhancer includes, by weight, 15-20 parts of hydrophobic silica, 5-7 parts of ethyl sulfate, 5-7 parts of monosilazane, and 10-15 parts of epoxy resin.

[0012] In a second aspect, a high temperature resistant cement slurry for oil wells is provided, characterized in that it comprises the following components: G-grade oil well cement, calcium carbonate powder, aluminum oxide powder, iron oxide, the above-mentioned mud high temperature enhancer, auxiliary materials, filtration loss reducer, and water.

[0013] Furthermore, in the high temperature resistant cement slurry used for oil wells, calculated by weight, it includes: 50-70 parts of G-grade oil well cement, 5-10 parts of calcium carbonate powder, 15-20 parts of aluminum oxide powder, 5-10 parts of iron oxide powder, 35-49 parts of the above-mentioned cement high temperature enhancer, 5.1-11 parts of auxiliary materials, and water; wherein, in the high temperature resistant cement slurry system, the water-to-solid ratio is 0.32-0.4.

[0014] Furthermore, the auxiliary materials include 1.5-5 parts of dispersant, 3-5 parts of fluid loss reducer, 0.3-0.5 parts of retarder, and 0.3-0.5 parts of defoamer.

[0015] Furthermore, when preparing high temperature resistant cement slurry for oil wells:

[0016] Fully mix the G-grade oil well cement, calcium carbonate powder, aluminum oxide powder and iron oxide to obtain a dry mixture;

[0017] Preparation of cement high temperature enhancer: mixing monosilazane with a portion of epoxy resin of equal weight, and then adding hydrophobic silica, ethyl sulfate, and the remaining epoxy resin to mix;

[0018] Mixing the cement high temperature enhancer with the dry mix to obtain a primary mix;

[0019] Then, the auxiliary material and water are mixed to obtain stirring water;

[0020] The primary mixture is added into stirring water and stirred evenly at high speed to obtain high temperature resistant cement slurry for oil wells.

[0021] In a third aspect, the above-mentioned high temperature resistant cement slurry for oil wells is used in high temperature oil well formations of 150°C-230°C.

[0022] The principles in this scheme are:

[0023] a. When the cement slurry prepared by hydrophobic silica, cement and other substances is introduced into a high-temperature formation oil well at 150℃-230℃, in the initial stage, due to the hydrophobicity of silica, the hydrophobic silica-CaO-H2O cannot undergo a good hydration reaction. As time goes by, ethyl sulfate gradually hydrolyzes to release acid, and the hydrophobic silica reacts with silazane in an acidic environment at 150℃-250℃, thus turning the hydrophobic silica into conventional silica (even hydrophilic silica); since it is difficult to undergo a hydration reaction under the hydrophobic effect of the hydrophobic silica in the initial stage of the cement slurry, the curing control effect of the cement is very excellent. b. In addition, the hydrophobicity of the hydrophobic silica itself will gradually be lost in an environment of 150℃-230℃, but the process will be relatively slow; therefore, this scheme controls the speed at which the hydrophobic silica loses its hydrophobicity through ethyl sulfate and silazane. c. The addition of epoxy resin can prevent hydrophobic silica from floating up when it is mixed with other substances to prepare cement slurry (it is very likely to float on the water surface and cannot be mixed well). d. Epoxy resin also has the function of improving the mechanical properties of cement after curing. In addition, iron oxide powder can also improve the mechanical properties of cement after curing. e. In addition to the hydrophobic silica that can react with CaO and water to hydrate, this solution also adds alumina powder (to avoid the complete failure of hydration reaction when cement is initially introduced; of course, the alumina here can be replaced with conventional silica).

[0024] Technical explanation: Hydrophobic silica refers to silica that has been treated to have hydrophobic methyl groups on its surface.

[0025] It should be noted that the hydrophobic silica in this embodiment can be replaced by hydrophobic fumed silica, hydrophobic alumina, or hydrophobic fumed alumina.

[0026] The present invention has the following advantages:

[0027] (1) When the cement slurry is introduced into a high-temperature formation of 150°C-230°C, the initial hydration degree of the cement slurry is low, and as time goes by, it gradually hydrates and solidifies; and the solidification mechanical properties after hydration are good;

[0028] (2) The hydration rate of cement slurry when it is introduced into a high-temperature formation of 150°C-230°C can be controlled to a certain extent, and the control effect is good. DETAILED DESCRIPTION

[0029] The present invention is further described below, but the protection scope of the present invention is not limited to the following description.

[0030] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0031] Example 1

[0032] This embodiment discloses a cement high-temperature enhancer, which includes, by weight, 20 parts of hydrophobic silica, 5 parts of ethyl sulfate, 5 parts of monosilazane, and 10 parts of epoxy resin.

[0033] Also disclosed is a high temperature resistant cement slurry for oil wells, the specific preparation steps of which are as follows:

[0034] Prepare dry mix, cement high temperature enhancer and mixing water separately:

[0035] When preparing the dry mix, 50 parts of G-grade oil well cement, 5 parts of calcium carbonate powder, 15 parts of aluminum oxide powder, and 5 parts of iron oxide powder are fully and evenly mixed to finally obtain the dry mix.

[0036] When preparing the cement high temperature enhancer, 5-silazane is mixed with 5 parts of epoxy resin, and then 20 parts of hydrophobic silica, 5 parts of ethyl sulfate, and the remaining 5 parts of epoxy resin are added and mixed.

[0037] Then the prepared cement high temperature enhancer is mixed with the dry mix to obtain a primary mix.

[0038] When preparing stirring water, 5.1 parts of auxiliary materials (including 1.5 parts of dispersant, 3 parts of fluid loss agent, 0.3 parts of retarder, and 0.3 parts of defoamer) and water are mixed to obtain stirring water, wherein the amount of water used is 0.32×(20+5+5+10+50+5+15+5+35+5.1) parts.

[0039] The primary mixture is then added into stirring water and stirred evenly at high speed to obtain high temperature resistant cement slurry for oil wells.

[0040] Example 2

[0041] This embodiment discloses a cement high-temperature enhancer, which includes, by weight, 17 parts of hydrophobic silica, 6 parts of ethyl sulfate, 6 parts of monosilazane, and 12 parts of epoxy resin.

[0042] Also disclosed is a high temperature resistant cement slurry for oil wells, the specific preparation steps of which are as follows:

[0043] Prepare dry mix, cement high temperature enhancer and mixing water separately:

[0044] When preparing the dry mix, 60 parts of G-grade oil well cement, 7 parts of calcium carbonate powder, 17 parts of aluminum oxide powder, and 8 parts of iron oxide powder are fully and evenly mixed to obtain the dry mix.

[0045] When preparing the cement high temperature enhancer, 6-silazane is mixed with 6 parts of epoxy resin, and then 17 parts of hydrophobic silica, 6 parts of ethyl sulfate, and the remaining 6 parts of epoxy resin are added and mixed.

[0046] Then the prepared cement high temperature enhancer is mixed with the dry mix to obtain a primary mix.

[0047] When preparing stirring water, 7.8 parts of auxiliary materials (including 3 parts of dispersant, 4 parts of fluid loss reducer, 0.4 parts of retarder, and 0.4 parts of defoamer) and water are mixed to obtain stirring water, wherein the amount of water used is 0.36×(17+6+6+12+60+7+17+8+43+7.8) parts.

[0048] The primary mixture is then added into stirring water and stirred evenly at high speed to obtain high temperature resistant cement slurry for oil wells.

[0049] The high temperature resistant cement slurry for oil wells in this embodiment is prepared in the manner of Example 1 (the only difference is that the corresponding weight components in this embodiment are used).

[0050] Example 3

[0051] This embodiment discloses a cement high-temperature enhancer, which includes, by weight, 20 parts of hydrophobic silica, 7 parts of ethyl sulfate, 7 parts of monosilazane, and 15 parts of epoxy resin.

[0052] Also disclosed is a high temperature resistant cement slurry for oil wells, the specific preparation steps of which are as follows:

[0053] Prepare dry mix, cement high temperature enhancer and mixing water separately:

[0054] When preparing the dry mix, 70 parts of G-grade oil well cement, 10 parts of calcium carbonate powder, 20 parts of aluminum oxide powder, and 10 parts of iron oxide powder are fully and evenly mixed to finally obtain the dry mix.

[0055] When preparing the cement high temperature enhancer, 7-silazane is mixed with 7 parts of epoxy resin, and then 20 parts of hydrophobic silica, 7 parts of ethyl sulfate, and the remaining 8 parts of epoxy resin are added and mixed.

[0056] Then the prepared cement high temperature enhancer is mixed with the dry mix to obtain a primary mix.

[0057] When preparing stirring water, 11 parts of auxiliary materials (including 5 parts of dispersant, 5 parts of fluid loss agent, 0.5 parts of retarder, and 0.5 parts of defoamer) and water are mixed to obtain stirring water, wherein the amount of water used is 0.4×(20+7+7+15+70+10+20+10+49+11) parts.

[0058] The primary mixture is then added into stirring water and stirred evenly at high speed to obtain high temperature resistant cement slurry for oil wells.

[0059] The high temperature resistant cement slurry for oil wells in this embodiment is prepared in the manner of Example 1 (the only difference is that the corresponding weight components in this embodiment are used).

[0060] Test Example 1

[0061] The high temperature resistant cement slurries prepared in Example 1, Example 2 and Example 3 are respectively taken as Group A, Group B and Group C;

[0062] Group e1: The ethyl sulfate and monosilazane in Example 1 were not added, conventional silica (the same amount as the hydrophobic silica in Example 1) was used, and the rest was the same as Example 1.

[0063] Group e2: Ethyl sulfate and monosilazane in Example 1 were added, conventional silica (the same amount as the hydrophobic silica in Example 1) was used, and the rest was the same as Example 1.

[0064] Group f1: The ethyl sulfate and monosilazane in Example 2 were not added, conventional silica (the same amount as the hydrophobic silica in Example 2) was used, and the rest was the same as Example 2.

[0065] Group f2: ethyl sulfate and monosilazane in Example 2 were added, conventional silica (the same amount as the hydrophobic silica in Example 2) was used, and the rest was the same as Example 2.

[0066] Group g1: The ethyl sulfate and monosilazane in Example 2 were not added, conventional silica (the same amount as the hydrophobic silica in Example 2) was used, and the rest was the same as Example 2.

[0067] Group g2: ethyl sulfate and monosilazane in Example 2 were added, conventional silica (the same amount as the hydrophobic silica in Example 2) was used, and the rest was the same as Example 2.

[0068] The cement slurries prepared from group a, group b, group c, group e1, group e2, group f1, group f2, group g1, and group g2 were subjected to hydration at 150°C and 230°C. The hydration process of the cement slurry was measured using a pressure permeameter or an initial setting time tester in accordance with API RP10B (American Petroleum Institute Recommended Practice). This equipment can monitor the time points of cement slurry thickening and hardening, and the measurement results are shown in Table 1.

[0069] Table 1 Cement slurry thickening and hardening experimental data

[0070]

[0071] It can be seen from Table 1 that, whether measured by the standard method or the temperature measurement method, the initial setting and waiting setting times of a, b, and c are much longer than those of e1, e2, f1, f2, g1, and g2, indicating that hydrophobic silica does play a role in delaying cement hydration.

[0072] It can be seen from Table 1 that the coagulation time at the same temperature between e1 and e2, between f1 and f2, and between g1 and g2 does not vary much. This indicates that when ethyl sulfate and monosilazane are added alone (without combining with hydrophobic silica), it does not play a role in delaying coagulation. This indicates that ethyl sulfate and monosilazane do modify hydrophobic silica at 150°C and 230°C.

[0073] It should be noted that in Table 1, e1, e2, f1, f2, g1, and g2 also show good extended setting effects, which may be affected by other additives (generally pure cement is around 150 minutes).

[0074] Test Example 2

[0075] After the solidification time measurement in Test Example 1 is completed, the compressive strength of the cement slurries of group a1, group b1, group c1, group e1, group e2, group f1, group f2, group g1, and group g2 are tested after solidification at 150°C and 230°C respectively. The test results are shown in the compressive strength data in Table 1.

[0076] It can be seen from Table 1 that compared with Groups E1, E2, F1, F2, G1 and G2, Group A, Group B and Group C have higher compressive strength, and the difference between the two is very small. This shows that in this solution, the substrate uses hydrophobic silica instead of conventional silica, which can still ensure a relatively good mechanical effect. Through data comparison, it can be seen that basically the hydrophobic silica is subsequently modified - that is, the hydrophobicity is removed (it becomes hydrophilic or conventional silica).

[0077] Test Example 3

[0078] Comparative Example 1 was used as a reference group;

[0079] Group e3: 0.1 part of monosilazane and 0.2 part of epoxy resin were used, and the rest was the same as that of Comparative Example 1;

[0080] Group e4: 1 part of monosilazane and 2 parts of epoxy resin were used, and the rest was the same as that of Comparative Example 1;

[0081] Group e5: 8 parts of monosilazane and 16 parts of epoxy resin were used, and the rest was the same as that of Comparative Example 1;

[0082] Group e6: 10 parts of monosilazane and 20 parts of epoxy resin were used, and the rest was the same as that of Comparative Example 1;

[0083] Group e7: 30 parts of monosilazane and 60 parts of epoxy resin were used, and the rest was the same as that of Comparative Example 1.

[0084] The hydration reaction time was tested respectively. The testing method was consistent with that in Test Example 1. The test results are shown in Table 2.

[0085] Table 2 Setting time of cement paste at different dosages of 1 / 4 silazane and 1 / 4 epoxy resin

[0086]

[0087]

[0088] It can be seen from Table 2 that when e3 is added with a small amount of silazane and epoxy resin, it still has a certain effect. From the comparison between e3 and e4, when the amount is increased, the effect is improved. From e5, e6, and e7, when the amount is further increased, the effect continues to improve, but from e7, it can be seen that when the amount added is too large, the improvement is limited.

[0089] It can be seen from Table 2 that the retarding time can be controlled by adjusting the amount of silazane and epoxy resin added.

[0090] The above embodiments only express preferred implementation modes, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the present invention. It should be pointed out that, for ordinary technicians in this field, several modifications and improvements can be made without departing from the concept of the present invention, and these all belong to the protection scope of the present invention.

Claims

1. A cement high temperature enhancer, characterized in that: The composition includes the following ingredients: hydrophobic silica, ethyl sulfate, monosilazane, epoxy resin.

2. A cement high temperature enhancer according to claim 1, characterized in that: During the preparation, a silazane is mixed with a portion of an epoxy resin of equal weight, and then hydrophobic silica, ethyl sulfate, and the remaining epoxy resin are added and mixed.

3. A cement high temperature enhancer according to claim 1 or 2, characterized in that: Calculated by weight, it includes 15-20 parts of hydrophobic silica, 5-7 parts of ethyl sulfate, 5-7 parts of monosilazane, and 10-15 parts of epoxy resin.

4. A high temperature resistant cement slurry for oil wells, characterized in that: The invention comprises the following components: G-class oil well cement, calcium carbonate powder, aluminum oxide powder, iron oxide, the cement high-temperature enhancer according to any one of claims 1 to 3, auxiliary materials, a fluid loss reducer, and water.

5. The high temperature resistant cement slurry for oil wells according to claim 4, characterized in that: The composition comprises, by weight: 50-70 parts of G-grade oil well cement, 5-10 parts of calcium carbonate powder, 15-20 parts of aluminum oxide powder, 5-10 parts of iron oxide powder, 35-49 parts of the cement high temperature enhancer according to any one of claims 1 to 3, 5.1-11 parts of auxiliary materials, and water; In the high temperature resistant cement slurry system, the water-to-solid ratio is 0.32-0.

4.

6. A high temperature resistant cement slurry for oil wells according to claim 4 or 5, characterized in that: The auxiliary materials include 1.5-5 parts of dispersant, 3-5 parts of fluid loss reducer, 0.3-0.5 parts of retarder, and 0.3-0.5 parts of defoamer.

7. The high temperature resistant cement slurry for oil wells according to claim 5, characterized in that: When preparing: Fully mix the G-grade oil well cement, calcium carbonate powder, aluminum oxide powder and iron oxide to obtain a dry mixture; Preparation of cement high temperature enhancer: mixing monosilazane with a portion of epoxy resin of equal weight, and then adding hydrophobic silica, ethyl sulfate, and the remaining epoxy resin to mix; Mixing the cement high temperature enhancer with the dry mix to obtain a primary mix; Then, the auxiliary material and water are mixed to obtain stirring water; The primary mixture is added into stirring water and stirred evenly at high speed to obtain high temperature resistant cement slurry for oil wells.

8. The use of high temperature resistant cement slurry for oil wells as claimed in claim 7, characterized in that: Used in high temperature oil well formations of 150℃-230℃.

Images