Offshore gas storage old well sealing layer superfine cement paste system and preparation method thereof
By using an ultra-fine cement slurry system in the sealing operation of the old well of offshore gas storage, the problems of low squeeze amount, reduced squeeze pressure and low cement stone strength are solved, and higher sealing and compressive strength are achieved, and operating efficiency and quality are improved.
Patent Information
- Application Number
- CN202311179224.9
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2023-09-13
- Publication Date
- 2025-03-14
AI Technical Summary
In the sealing operation of the old well of the offshore gas storage, there are problems such as low squeeze volume, reduced squeeze pressure, and low cement stone strength. They cannot meet the design requirements and are affected by environmental factors, and cannot be monitored regularly, which has higher requirements.
The ultrafine cement slurry system of sealed old wells in offshore gas storage is adopted, including ultrafine cement of oil wells, suspension agents, nano-enhancing agents, expansion agents, microsilicon, water reduction agents, retarders and defoaming agents. By mixing dry and wet-mixed materials, cement slurry with high penetration ability and compressive strength is prepared.
It significantly improves the penetration and retention ability of cement slurry, enhances the compressive strength and sealing properties of cement stone, solves the problems of low squeeze volume and reduced squeeze pressure, and improves the operating age and quality of sealing operations.
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Abstract
Description
Technical Field
[0001] The present application relates to the field of gas storage production, and in particular to an ultra-fine cement slurry system for sealing an old well of an offshore gas storage and a preparation method thereof. Background Art
[0002] Underground gas storage has irreplaceable advantages in seasonal peak regulation, gas supply guarantee, accident emergency and strategic reserve, and has become one of the infrastructures for storing natural gas in countries around the world. Since the domestic gas storage was put into operation in 2000, it has begun to take shape and is currently in a period of rapid development. Underground gas storage is mainly based on onshore depleted gas reservoirs. After years of production, the old wells in the reservoir area will experience internal and external corrosion of the casing, thinning of the pipe wall, and varying degrees of reduction in the strength of the pipe column. Under the influence of changes in injection and production pressure during the operation of the gas storage, potential channels will be opened, posing a threat to the sealing of the gas storage reservoir closure. Therefore, it is necessary to reliably plug the old wells that affect the safety of the gas storage.
[0003] In 2021, CNPC started the construction of an offshore gas storage facility, which is the first offshore gas storage facility in China. It is necessary to seal the old wells in the storage area according to the gas storage construction standards. In addition to facing the problem of sealing the old wells in onshore gas storage facilities, compared with the sealing of old wells in onshore gas storage facilities, the sealing of old wells in offshore gas storage facilities can retain the wellhead equipment on land and conduct regular pressure monitoring. The wellhead is not retained after abandonment due to environmental factors at sea, and regular monitoring is impossible. Therefore, higher requirements are placed on the sealing of the old wells. Since the development of this block, acidification, fracturing, water injection and other operations have been carried out many times. The internal connectivity of the formation is complex, and the formation physical properties of some old wells vary greatly. There are many stratum sections that need to be blocked or the original blocked sections need to be treated again. The main problems in current sealing operations are: 1. The reservoir permeability is low, and the injection volume of conventional cement slurry system cannot meet the design requirements; 2. The formation energy is exhausted and prone to leakage, and the pressure test after injection fails, and the one-time plugging effect is not good; 3. Affected by the original cementing quality, conventional sealing technology cannot meet the sealing requirements of some old well gas storage reservoirs.
[0004] Compared with the sealing layers of old wells in offshore gas storage facilities, those in onshore gas storage facilities can retain the wellhead devices on land and conduct regular pressure monitoring, while those in offshore gas storage facilities are affected by environmental factors, and the wellheads are not retained after abandonment, making regular monitoring impossible. Therefore, higher quality requirements are placed on the sealing layers of old wells, while taking into account the timeliness of the sealing operations of old wells in offshore gas storage facilities. Summary of the invention
[0005] The present application provides an ultra-fine cement slurry system for sealing old wells in offshore gas storage facilities and a preparation method thereof, which can overcome the technical difficulties in sealing old wells in gas storage facilities, such as small injection volume, reduced injection pressure, and low cement stone strength, which cannot meet the design requirements.
[0006] This application adopts the following technical solutions:
[0007] The present application provides an ultrafine cement slurry system for sealing old wells of offshore gas storage facilities, comprising the following components in parts by weight: 100 parts of oil well ultrafine cement, 1-3 parts of suspending agent, 1-3 parts of nano-enhancer, 1-3 parts of expansion agent, 3-5 parts of microsilica, 6-7 parts of fluid loss reducer, 0-0.35 parts of retarder, 0.05-0.06 parts of defoamer, and 54-63 parts of water.
[0008] Furthermore, the particle size of the oil well ultrafine cement is 8-15 μm.
[0009] Further, the suspending agent comprises a hydrophobically associating water-soluble polymer.
[0010] Further, the nano-enhancer includes nano-sized oxides or nano-sized organic compounds.
[0011] Furthermore, the particle size of the micro silicon is 0.1-0.5 μm.
[0012] Further, the expansion agent includes a metal oxide.
[0013] Furthermore, the fluid loss additive includes a nonionic polymer or an anionic liquid polymer.
[0014] Furthermore, the retarder includes at least one of an organic acid retarder, a zinc salt retarder, a phosphate retarder and a wood sulfonate.
[0015] Furthermore, the defoaming agent includes tributyl phosphate or a silicone defoaming agent.
[0016] The present application provides a method for preparing the above-mentioned ultrafine cement slurry system for sealing the old wells of offshore gas storage, comprising the following steps: dry-mixing the formulated amount of oil well ultrafine cement, suspending agent, nano-enhancer, expansion agent, and micro-silicon to obtain a dry-mixed material. Dissolving the formulated amount of fluid loss reducer, retarder, and defoamer in water, stirring, and obtaining a wet-mixed material. Adding the dry-mixed material to the wet-mixed material, stirring and defoaming, and obtaining the ultrafine cement slurry system for sealing the old wells of the gas storage.
[0017] Furthermore, the formulated amount of fluid loss reducer, retarder and defoamer is dissolved in water.
[0018] Further, the dry mixed material was added to the wet mixed material at a stirring speed of 4000 rpm.
[0019] Furthermore, after adding the dry mixed material into the wet mixed material, the stirring speed was maintained at 4000 rpm for 35 seconds.
[0020] Compared with the prior art, this application has the following beneficial effects:
[0021] The ultrafine cement slurry for sealing the old wells of the gas storage reservoir of the present application improves the strength of the cement stone while ensuring the penetration ability of the cement slurry by selecting ultrafine cement with suitable particle size, introducing suspending agents and nano-enhancers, and solving the problem of small squeezed amount. By adding suspending agents, fluid loss reducers, and expansion agents, the retention capacity of the cement slurry in the pores of the formation is increased, and the gas permeability of the cement stone is reduced, which solves the problems of reduced squeezing pressure, low strength of the cement stone, and other problems that cannot meet the design requirements, and improves the timeliness and quality of the sealing operation. In general, compared with the existing sealing cement slurry system, the ultrafine cement slurry system for sealing the old wells of the gas storage reservoir of the present application improves the penetration ability of the cement slurry, increases the retention capacity of the cement slurry in the pores of the formation, improves the compressive strength of the cement stone, and reduces the gas permeability of the cement stone, thereby improving the timeliness and quality of the sealing operation.
[0022] The main technical indicators of the ultra-fine cement slurry for sealing the old well of the gas storage reservoir in this application are as follows: Adaptable temperature: 60-100°C; Cement slurry density: 1.70-1.80g / cm 3 ; Initial consistency <30Bc; Free liquid in cement slurry is 0; Density difference between upper and lower cement stone columns in the settlement stability test <0.02g / cm 3 ; Water loss of cement paste <50ml; 24-hour compressive strength of cement paste ≥14MPa; Gas permeability of cement paste <0.05×10 -3 μm 2 , meeting the technical requirements of ultra-fine cement slurry for sealing the old wells of the gas storage reservoir. The field application results show that the results meet the engineering requirements. DETAILED DESCRIPTION
[0023] The technical methods in the embodiments of the present application are described clearly and completely below. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present application.
[0024] The following problems exist in the related technologies: (1) The plugging agent consolidation body itself and the bonding strength between the plugging agent consolidation body and the formation or pipe wall interface are low, and the pressure bearing capacity is insufficient. (2) The plugging material is fine, and there is a contradiction between injection and leakage. (3) The comprehensive performance of cement slurry is not good. Some cement slurries have poor rheology, large water loss, insufficient density of cement stone, and complex on-site operation, which limit its scope of application. The embodiment of the present application provides an ultra-fine cement slurry system for sealing old wells in an offshore gas storage reservoir, comprising the following components by weight: 100 parts of oil well ultra-fine cement, 1-3 parts of suspending agent, 1-3 parts of nano-enhancer, 1-3 parts of expansion agent, 3-5 parts of microsilicon, 6-7 parts of water loss reducer, 0-0.35 parts of retarder, 0.05-0.06 parts of defoaming agent, and 54-63 parts of water.
[0025] The particle size of oil well ultrafine cement can be 8-15μm. Oil well ultrafine cement meets the chemical composition and mineral composition requirements of oil well G-grade high sulfur resistance cement, ensuring the long-term performance requirements of the sealing layer.
[0026] The nano-enhancer can be a nano-oxide or a nano-organic compound. The particle size of the nano-enhancer can be 50 to 100 nm. The dosage of the nano-enhancer is determined by experiments according to the performance requirements of the cement paste. The nano-enhancer improves the compressive strength of the cement paste.
[0027] The particle size of microsilicon is 0.1-0.5μm. The amount of microsilicon added is determined through experiments based on the performance requirements of cement slurry.
[0028] Among them, nano-enhancers and micro-silicon improve the penetration ability of cement slurry while increasing the compressive strength of cement stone. The 24-hour compressive strength of cement stone is ≥14MPa, which improves the operation time efficiency and shortens the sealing operation period.
[0029] Suspending agent is a hydrophobic associating water-soluble polymer that can be dissolved in the slurry water. The dosage of suspending agent is determined by experiments according to the performance requirements of cement slurry. Suspending agent plays a stabilizing role in cement slurry and also plays a retention role in cement slurry injected into the pores of the formation.
[0030] The expansion agent can be a metal oxide, such as calcium oxide, magnesium oxide, and iron oxide. The particle size of the metal oxide is 20 to 30 μm. The amount of the expansion agent is determined by experiments based on the performance requirements of the cement slurry. The expansion agent produces a lattice expansion effect in the cement paste, reducing the gas permeability of the cement paste.
[0031] The fluid loss agent can be a nonionic polymer or anionic liquid polymer. Preferably, the fluid loss agent is a liquid fluid loss agent. The dosage of the fluid loss agent is determined by experiment according to the performance requirements of the cement slurry. In addition to the water loss reduction effect of the cement slurry, the fluid loss agent plays an auxiliary retention role in the cement slurry injected into the pores of the formation.
[0032] The retarder can be at least one of an organic acid retarder, a zinc salt retarder, a phosphate retarder and a wood sulfonate, such as an organic acid retarder, or a mixture of a phosphate retarder and a wood sulfonate. The dosage of the retarder is adjusted according to the construction requirements to meet the needs of safe construction of the project.
[0033] The defoamer can be tributyl phosphate or an organosilicon defoamer, and is added during the preparation of cement slurry.
[0034] Among them, the suspending agent ensures the stability of cement slurry, and the uniform slurry improves the injection capacity of cement slurry. At the same time, the suspending agent is composed of high molecular polymers to improve the retention capacity of cement slurry in the formation. The expansion agent reduces the gas permeability of cement stone and provides guarantee for the sealing of gas storage reservoir. The fluid loss agent and retarder ensure the safe construction of the sealing operation.
[0035] The amount of water can be 54, 60, 63 parts, etc. The amount of water is adjusted according to the density requirements of the cement slurry.
[0036] Optionally, the superfine cement slurry for sealing the old well of the gas storage reservoir is composed of the following components in parts by weight: 100 parts of oil well G grade superfine cement + 3 parts of suspending agent + 3 parts of reinforcing agent + 3 parts of expanding agent + 5 parts of microsilica + 6 parts of fluid loss reducer + 63 parts of water + 0.2 parts of retarder + 0.05 parts of defoaming agent; the density is 1.70 g / cm 3 Ultra-fine cement slurry for sealing old wells.
[0037] Optionally, the superfine cement slurry for sealing the old well of the gas storage reservoir is composed of the following components in parts by weight: 100 parts of oil well G grade superfine cement + 2 parts of suspending agent + 3 parts of reinforcing agent + 3 parts of expanding agent + 5 parts of microsilica + 6 parts of fluid loss reducer + 60 parts of water + 0.2 parts of retarder + 0.05 parts of defoaming agent; the density is 1.75g / cm 3 Ultra-fine cement slurry for sealing old wells.
[0038] Optionally, the superfine cement slurry for sealing the old well of the gas storage reservoir is composed of the following components in parts by weight: 100 parts of oil well G grade superfine cement + 1 part of suspending agent + 3 parts of reinforcing agent + 3 parts of expanding agent + 5 parts of microsilica + 6 parts of fluid loss reducer + 54 parts of water + 0.2 parts of retarder + 0.05 parts of defoaming agent; the density is 1.80 g / cm 3 Ultra-fine cement slurry for sealing old wells.
[0039] The ultrafine cement slurry for sealing the old wells of the gas storage reservoir of the present application improves the strength of the cement stone while ensuring the penetration ability of the cement slurry by selecting ultrafine cement with suitable particle size, introducing suspending agents and nano-enhancers, and solving the problem of small squeezed amount. By adding suspending agents, fluid loss reducers, and expansion agents, the retention capacity of the cement slurry in the pores of the formation is increased, and the gas permeability of the cement stone is reduced, which solves the problems of reduced squeezing pressure, low strength of the cement stone, and other problems that cannot meet the design requirements, and improves the timeliness and quality of the sealing operation. In general, compared with the existing sealing cement slurry system, the ultrafine cement slurry system for sealing the old wells of the gas storage reservoir of the present application improves the penetration ability of the cement slurry, increases the retention capacity of the cement slurry in the pores of the formation, improves the compressive strength of the cement stone, and reduces the gas permeability of the cement stone, thereby improving the timeliness and quality of the sealing operation.
[0040] The performance requirements of ultra-fine cement slurry for sealing layer of old wells in gas storage are shown in Table 1:
[0041] Table 1 Performance requirements of ultra-fine cement slurry for sealing layer of old wells in gas storage
[0042]
[0043] The embodiment of the present application also provides a method for preparing an ultra-fine cement slurry system for sealing an old well of an offshore gas storage, comprising the following steps:
[0044] Step 1) dry-mixing the formulated amount of oil well ultrafine cement, suspending agent, nano-enhancing agent, expansion agent and micro-silicon in a blender to obtain a dry-mixed material.
[0045] Step 2) dissolving the formulated amount of fluid loss reducer, retarder and defoamer in water, stirring to obtain a wet mixed material.
[0046] In the above steps, the formulated amount of fluid loss reducer, retarder and defoamer is dissolved in water.
[0047] Step 3) While keeping the wet mixed material in a stirring state, the dry mixed material is uniformly added to the wet mixed material, stirred and defoamed to obtain an ultra-fine cement slurry system for sealing the old well of the gas storage reservoir.
[0048] In the above steps, the dry mixed material is added to the wet mixed material at a stirring speed of 4000 rpm.
[0049] After adding the dry mixed material to the wet mixed material, stir at a stirring speed of 4000 rpm for 35 seconds.
[0050] The following is a detailed description with reference to specific embodiments:
[0051] Example 1
[0052] 1) According to 1 g per portion, 100 parts of oil well ultrafine cement, 3 parts of suspending agent, 3 parts of nano-enhancer, 3 parts of expansion agent, and 5 parts of micro-silicon are dry-mixed in a blender to obtain a dry-mixed material.
[0053] 2) Dissolve 6 parts of fluid loss additive, 0.2 parts of retarder and 0.05 parts of defoamer in 63 parts of water and stir to obtain a wet mix.
[0054] 3) Add the dry mixed material into the wet mixed material at a stirring speed of 4000 rpm (15 seconds), then stir at a stirring speed of 4000 rpm for 35 seconds to make it uniform and defoam. The prepared cement slurry is the ultra-fine cement slurry system for sealing the old well of the gas storage reservoir (density 1.70 g / cm 3 ).
[0055] The properties of the cement slurry in Example 1 were measured and the results are shown in Tables 2 and 3.
[0056] Example 2
[0057] 1) According to 1 g per portion, 100 parts of oil well ultrafine cement, 3 parts of suspending agent, 3 parts of nano-enhancer, 3 parts of expansion agent, and 5 parts of micro-silicon are dry-mixed in a blender to obtain a dry-mixed material.
[0058] 2) Dissolve 6 parts of fluid loss additive, 0.35 parts of retarder and 0.05 parts of defoamer in 63 parts of water and stir to obtain a wet mix.
[0059] 3) Add the dry mixed material into the wet mixed material at a stirring speed of 4000 rpm (15 seconds), then stir at a stirring speed of 4000 rpm for 35 seconds to make it uniform and defoam. The prepared cement slurry is the ultra-fine cement slurry system for sealing the old well of the gas storage reservoir (density 1.70 g / cm 3 ).
[0060] The properties of the cement slurry in Example 2 were measured and the results are shown in Tables 2 and 3.
[0061] Example 3
[0062] 1) According to 1 g per portion, 100 parts of oil well ultrafine cement, 2 parts of suspending agent, 3 parts of nano-enhancer, 3 parts of expansion agent, and 5 parts of micro-silicon are dry-mixed in a blender to obtain a dry-mixed material.
[0063] 2) Dissolve 6 parts of fluid loss additive, 0.2 parts of retarder and 0.05 parts of defoamer in 60 parts of water and stir to obtain a wet mix.
[0064] 3) Add the dry mixed material to the wet mixed material at a stirring speed of 4000 rpm (15 seconds), then stir at a stirring speed of 4000 rpm for 35 seconds to make it uniform and defoam. The prepared cement slurry is the ultra-fine cement slurry system (density 1.75 g / cm 3 ).
[0065] 4) The properties of the cement slurry in Example 3 were measured. The results are shown in Tables 2 and 3.
[0066] Example 4
[0067] 1) According to 1 g per portion, 100 parts of oil well ultrafine cement, 2 parts of suspending agent, 3 parts of nano-enhancer, 3 parts of expansion agent, and 5 parts of micro-silicon are dry-mixed in a blender to obtain a dry-mixed material.
[0068] 2) Dissolve 6 parts of fluid loss additive, 0.3 parts of retarder and 0.05 parts of defoamer in 60 parts of water and stir to obtain a wet mix.
[0069] 3) Add the dry mixed material to the wet mixed material at a stirring speed of 4000 rpm (15 seconds), then stir at a stirring speed of 4000 rpm for 35 seconds to make it uniform and defoam. The prepared cement slurry is the ultra-fine cement slurry system (density 1.75 g / cm 3 ).
[0070] The properties of the cement slurry in Example 4 were measured and the results are shown in Tables 2 and 3.
[0071] Example 5
[0072] 1) According to 1 g per portion, 100 parts of oil well ultrafine cement, 1 part of suspending agent, 3 parts of nano-enhancer, 3 parts of expansion agent, and 5 parts of micro-silicon are dry-mixed in a blender to obtain a dry-mixed material.
[0073] 2) Dissolve 6 parts of fluid loss additive, 0.2 parts of retarder and 0.05 parts of defoamer in 54 parts of water and stir to obtain a wet mix.
[0074] 3) Add the dry mixed material to the wet mixed material at a stirring speed of 4000 rpm (15 seconds), then stir at a stirring speed of 4000 rpm for 35 seconds to make it uniform and defoam. The prepared cement slurry is the ultra-fine cement slurry system for sealing the old well of the gas storage reservoir (density 1.80 g / cm 3 ).
[0075] The properties of the cement slurry in Example 5 were measured and the results are shown in Tables 2 and 3.
[0076] Example 6
[0077] 1) According to 1 g per portion, 100 parts of oil well ultrafine cement, 1 part of suspending agent, 3 parts of nano-enhancer, 3 parts of expansion agent, and 5 parts of micro-silicon are dry-mixed in a blender to obtain a dry-mixed material.
[0078] 2) Dissolve 6 parts of fluid loss additive, 0.35 parts of retarder and 0.05 parts of defoamer in 54 parts of water and stir to obtain a wet mix.
[0079] 3) Add the dry mixed material to the wet mixed material at a stirring speed of 4000 rpm (15 seconds), then stir at a stirring speed of 4000 rpm for 35 seconds to make it uniform and defoam. The prepared cement slurry is the ultra-fine cement slurry system for sealing the old well of the gas storage reservoir (density 1.80 g / cm 3 ).
[0080] The properties of the cement slurry in Example 6 were measured and the results are shown in Tables 2 and 3.
[0081] Table 2 Performance results of ultra-fine cement slurry for sealing layer of old wells in gas storage
[0082]
[0083] Table 3 Measurement results of cement stone in the sealing layer of old wells in gas storage
[0084]
[0085] Table 2 lists the performance test results of density, fluidity, sedimentation stability, water loss, free liquid and thickening time of the ultrafine cement slurry for sealing the old wells of the gas storage reservoir at 80℃ and 100℃ (well circulation temperature under actual working conditions); Table 3 lists the permeability test results of the cement stone for sealing the old wells of the gas storage reservoir at 80℃ and 100℃ and the compressive strength test results at different ages.
[0086] By testing the performance of the ultrafine cement slurry for sealing the old well of the gas storage reservoir in Examples 1-6, it can be seen that the cement slurries prepared with different densities have the characteristics of good stability, good fluidity, zero upper and lower density difference and free water, low water loss, adjustable thickening time, and are easy to prepare on site.
[0087] By testing the performance of cement stone for sealing the old wells of the gas storage in Examples 1-6, it can be seen that the permeability of cement stone at 80°C and 100°C is less than 0.015×10 -3 μm 2 , the cement paste is dense; the compressive strength of the cement paste develops rapidly, and the 24h compressive strength is ≥14MPa.
[0088] The ultra-fine cement slurry system for sealing the old wells of the gas storage reservoir of the present application is applied in the sealing operation of the old wells of the offshore gas storage reservoir. Compared with the previous operations, the ultra-fine cement slurry system for sealing the old wells of the gas storage reservoir of the present application avoids the problem that some previous operations failed the pressure test after squeezing and injection, and the sealing effect was not good once and needed to be squeezed twice or even multiple times to meet the engineering requirements. Compared with the strength of the previous cement stone, the ultra-fine cement slurry system for sealing the old wells of the gas storage reservoir of the present application shortens the offshore waiting time, improves the operation timeliness, and saves engineering costs.
[0089] By using the ultra-fine cement slurry system for sealing the old wells of the gas storage reservoir of the present application, the technical problems existing in the sealing operation of the old wells of the gas storage reservoir, such as small squeezing volume, reduced squeezing pressure, low strength of cement stone, etc., which cannot meet the design requirements, are solved. Specifically, the squeezing radius is increased from 0.30-0.71m to 1.96-3.41m by converting the squeezing radius of the actual squeezing cement slurry volume. The use of the ultra-fine cement slurry system for sealing the old wells of the gas storage reservoir of the present application significantly expands the squeezing radius of the cement slurry, ensuring the sealing of the reservoir closure; by testing the cement plug with a pressure of 20MPa and stabilizing the pressure for 30min, the pressure does not drop; the 24-hour compressive strength of the cement stone is ≥14MPa, which meets the subsequent construction requirements and improves the operation time efficiency of the offshore sealing operation.
[0090] In general, the ultra-fine cement slurry for sealing the old well of the offshore gas storage provided in this application has the following beneficial effects:
[0091] The ultra-fine cement slurry for sealing the old well of the offshore gas storage provided in this application uses a suspending agent to ensure the stability of the cement slurry, and the uniform slurry improves the injection capacity of the cement slurry. At the same time, the suspending agent is composed of a high molecular polymer to improve the retention capacity of the cement slurry in the formation;
[0092] The ultra-fine cement slurry for sealing the old well of the offshore gas storage provided in this application uses nano-enhancers and micro-silicon to improve the penetration ability of the cement slurry while improving the compressive strength of the cement stone. The 24-hour compressive strength of the cement stone is ≥14MPa, which improves the operation time efficiency and shortens the offshore sealing operation period;
[0093] The ultra-fine cement slurry for sealing the old well of the offshore gas storage provided in this application uses an expansion agent to reduce the gas permeability of cement stone, thereby providing a guarantee for the sealing of the gas storage reservoir trap;
[0094] The ultra-fine cement slurry for sealing the old well of the offshore gas storage provided in this application adopts a fluid loss reducer and a retarder to ensure the safe construction of the sealing operation.
[0095] In summary, the ultra-fine cement slurry for sealing the old well of the offshore gas storage provided by this application has good stability, small water loss, good fluidity, and strong penetration ability of cement slurry. At the same time, it increases the retention capacity of cement slurry in the pores of the formation, improves the compressive strength of cement stone, and reduces the gas permeability of cement stone, solving the problems of small squeezing volume, reduced squeezing pressure, and low strength of cement stone in the sealing project. It improves the operation timeliness and operation quality of the sealing operation.
[0096] The above shows and describes the basic principles, main features and advantages of the present application. Those skilled in the art should understand that the present application is not limited by the above embodiments, and the above embodiments and descriptions are only for explaining the principles of the present application. Without departing from the spirit and scope of the present application, the present application may have various changes and improvements, and the scope of protection required by the present application is defined by the attached claims, description and their equivalents.
[0097] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present application rather than to limit the scope of protection of the present application. Although the present application has been described in detail with reference to the preferred embodiments, ordinary technicians in this field should understand that the technical solution of the present application can be modified or replaced by equivalents without departing from the essence and scope of the technical solution of the present application.
Claims
1. An ultra-fine cement slurry system for sealing old wells in offshore gas storage, characterized in that: The composition comprises the following components in parts by weight: 100 parts of oil well ultrafine cement, 1-3 parts of suspending agent, 1-3 parts of nano-enhancer, 1-3 parts of expansion agent, 3-5 parts of micro-silicon, 6-7 parts of fluid loss reducer, 0-0.35 parts of retarder, 0.05-0.06 parts of defoamer and 54-63 parts of water.
2. The ultra-fine cement slurry system for sealing old wells of offshore gas storage according to claim 1, characterized in that: The particle size of the oil well ultrafine cement is 8-15 μm.
3. The ultra-fine cement slurry system for sealing old wells of offshore gas storage according to claim 1, characterized in that: The suspending agent comprises a hydrophobically associating water-soluble polymer.
4. The ultra-fine cement slurry system for sealing old wells of offshore gas storage according to claim 3, characterized in that: The nano-enhancer includes nano-sized oxides or nano-sized organic compounds.
5. The ultra-fine cement slurry system for sealing old wells of offshore gas storage according to claim 1, characterized in that: The particle size of the micro silicon is 0.1-0.5 μm.
6. The ultra-fine cement slurry system for sealing old wells of offshore gas storage according to claim 1, characterized in that: The expansion agent includes a metal oxide; The fluid loss additive comprises a nonionic polymer or an anionic liquid polymer: The retarder comprises at least one of an organic acid retarder, a zinc salt retarder, a phosphate retarder and a wood sulfonate; The defoaming agent includes tributyl phosphate or an organosilicon defoaming agent.
7. A method for preparing an ultra-fine cement slurry system for sealing an old well of an offshore gas storage facility according to any one of claims 1 to 6, characterized in that: The following steps are involved: Dry-mixing the formulated amounts of oil well ultrafine cement, suspending agent, nano-enhancing agent, expansion agent and micro-silicon to obtain a dry-mixed material; Dissolve the formulated amount of fluid loss reducer, retarder and defoamer in water and stir to obtain a wet mixed material; The dry mixed material is added to the wet mixed material, stirred and defoamed to obtain an ultra-fine cement slurry system for sealing the old well of the gas storage reservoir.
8. The preparation method according to claim 7, characterized in that: Dissolve the formulated amount of fluid loss reducer, retarder and defoamer in water.
9. The preparation method according to claim 7, characterized in that: The dry mixed material was added to the wet mixed material at a stirring speed of 4000 rpm.
10. The preparation method according to claim 9, characterized in that: After adding the dry mixed material to the wet mixed material, the stirring speed was maintained at 4000 rpm for 35 seconds.