Continuous grading low-density oil well cement, low-density cement paste and preparation method
By crushing, grinding and screening materials such as cement clinker, continuous graded low-density oil well cement is prepared, which solves the problems of insufficient uniformity and strength of low-density cement and improves the cementing effect of deep wells.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- DAQING PETROLEUM ADMINISTRATION
- Filing Date
- 2024-10-28
- Publication Date
- 2026-04-28
AI Technical Summary
While existing low-density cement meets the low-density requirement, its uniformity and cement stone strength decrease, making it difficult to meet the sealing requirements of complex wells such as deep wells.
By crushing, grinding, and screening cement clinker, natural gypsum, fly ash, slag powder, and silica fume, a continuously graded cement with a more reasonable particle distribution is obtained. This cement is then mixed with light-reducing materials and chemical admixtures to optimize particle size distribution, thereby improving tensile strength and reducing porosity, thus preparing continuously graded low-density oil well cement.
This approach achieves the goal of improving the cement sheath's resistance to fluid intrusion and enhancing early strength while adjusting cement density, ensuring thickening time and fluidity during construction, and improving cementing performance.
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Figure CN121929951A_ABST
Abstract
Description
Technical Field
[0001] This disclosure relates to the field of oil and gas well cementing technology, specifically a low-density oil well cement. Background Technology
[0002] With the continuous expansion of oilfield exploration and the improvement of drilling technology, especially with the deepening of exploration, the number of deep wells, ultra-deep wells, complex wells, wells with long cemented sections, and wells prone to leakage is constantly increasing. Conventional cement slurry systems can no longer meet the cementing requirements of such wells. Low-density cement is of great significance for the protection of oil and gas reservoirs and the improvement of cementing quality.
[0003] Existing low-density cement consists of cement, various weight-reducing materials, and various chemical admixtures. It is prepared by mixing using pneumatic or mechanical mixing devices over a specific time. For example, CN109517589 discloses a low-density cement slurry for dry cementing of oil and gas wells, which comprises: 100 parts cement; weight-reducing materials: 0.1-10 parts fiber, 0.1-10 parts nut shell, 1-60 parts weight-reducing agent, 1-50 parts filler; chemical admixtures: 1-40 parts fluid loss reducer, 0.01-20 parts retarder, and 0.1-10 parts defoamer. Publication No. CN109943305 discloses a low-density cement slurry with bioash, the composition of which is: 250-600 parts of cement; lightweighting materials: 25-100 parts of ultrafine mineral powder, 3-20 parts of cenospheres, 5-12 parts of microsilica, 20-100 parts of bioash; chemical admixtures: 10-80 parts of reinforcing agent, 3-60 parts of water loss reducing agent, 1-8 parts of retarder, 0.5-8 parts of defoamer, and 0-5 parts of dispersant. Publication No. CN108395154 discloses a low-density cement for cementing, the composition of which is: 55% to 70% of oil well grade G cement; weight-reducing materials: 5% to 8% high-strength microspheres, 2% to 7% cenospheres, 2% to 3% perlite, 8% to 12% silica fume, 3% to 9% fly ash; chemical admixtures: 2% fluid loss reducer, 2% to 3% stabilizer, 1% expansion agent, 0.6% to 0.75% early-strength agent, and 0.25% to 4% drag-reducing agent.
[0004] The density of the aforementioned low-density cement is controlled by changing the amount of lightening materials added. However, this control method has certain drawbacks. Because a large amount of lightening materials cannot be fully mixed during the mixing process, the uniformity of the cement is reduced, the hydration reaction process is affected, and the cement performance deteriorates, especially the strength of the cement stone is greatly reduced. Sometimes it is difficult to meet the requirements for sealing the formation. Moreover, the lower the density of the cement, the more prominent this contradiction becomes. Summary of the Invention
[0005] In view of this, this disclosure provides a continuously graded low-density oil well cement, a low-density cement slurry, and a preparation method thereof, which solves the problem that while current low-density cement slurries meet the requirement of low density, their uniformity and cement stone strength are reduced, sometimes making it difficult to meet the requirements for sealing formations.
[0006] The technical principle of the continuously graded low-density oil well cement and low-density cement slurry of the present invention is as follows:
[0007] Because the lightweight materials are too light to be used in grinding, the cement clinker, natural gypsum, fly ash, slag powder, and silica fume are first thoroughly crushed, ground, and screened to obtain cement with a more reasonable particle distribution and good particle size distribution continuity. Then, the cement is further mixed with the lightweight materials and chemical admixtures to obtain continuously graded low-density oil well cement. This continuous gradation performance can optimize the particle size distribution between cement and other materials while adjusting the cement density, maximizing the packing ratio between materials, increasing tensile strength, and reducing porosity and permeability. This prevents the migration of formation fluids along the cement stone matrix, effectively improving the cement sheath's resistance to fluid intrusion and further enhancing the early strength of the low-density cement stone.
[0008] Furthermore, compared with conventional low-density cement slurry, the low-density cement slurry prepared using continuously graded low-density oil well cement has a faster hydration rate during cement hydration, more stable strength development, better control over thickening time and fluidity during construction, and better cementing effect.
[0009] To achieve the aforementioned objectives, in a first aspect, the continuously graded low-density oil well cement disclosed herein comprises:
[0010] Continuously graded cement, weight-reducing materials, and chemical admixtures;
[0011] The continuously graded cement comprises cement clinker, natural gypsum, fly ash, slag powder, and silica fume. The screening index for the continuously graded cement is a specific surface area of 320. + 10m 2 / kg, 45-micron fineness: 9.0 + 2.0%, SO3: 2.0 + 0.2%;
[0012] The mixture of the weight-reducing material, the chemical admixture, and the continuously graded cement is the continuously graded low-density oil well cement.
[0013] In this disclosure and possible embodiments, the light-reducing material is perlite.
[0014] In this disclosure and possible embodiments, the bulk density of the perlite is ≥80 kg / m³. 3 And ≤120kg / m3 Volumetric water absorption rate ≤45%, volumetric buoyancy rate ≥80%.
[0015] In this disclosure and possible embodiments, the chemical additive includes:
[0016] Early strength agents, retarders, rheology modifiers, and water loss reducers.
[0017] In this disclosure and possible embodiments, the early strength agent is composed of potassium carbonate, polyaluminum chloride, sodium silicate and calcium silicate.
[0018] In this disclosure and possible embodiments, the retarder is composed of aluminum sulfate, sodium carbonate, polyaluminum ferric sulfate and active light calcium carbonate.
[0019] In this disclosure and possible embodiments, the rheology modifier is composed of formaldehyde, acetone, and triethanolamine sodium hydroxide.
[0020] In this disclosure and possible embodiments, the water loss reducing agent is composed of 2-acrylamide, 2-methylpropanesulfonic acid, ammonium persulfate, sodium bisulfite, sodium hydroxide, and N-methylenebisacrylamide.
[0021] In this disclosure and possible embodiments, by mass percentage, cement clinker 42%–54%, natural gypsum 5%–7%, fly ash 13%–19%, slag powder 10%–15%, microsilica 7%–10%, and perlite 2%–7%;
[0022] Early-strength agent 3%–5%, retarder 0.7%–2%, rheology modifier 0.06%, and water loss reducer 2%.
[0023] Secondly, the method for preparing continuously graded low-density oil well cement as described in the first aspect includes:
[0024] Cement clinker and natural gypsum are crushed into mixed powder particles with a particle size of <3mm;
[0025] Continuously graded cement is obtained by grinding and screening a mixture of fly ash, slag powder, silica fume, and the aforementioned mixed powder particles. The control index for screening is: specific surface area: 320. + 10m 2 / kg, 45-micron fineness: 9.0 + 2.0%, SO3: 2.0 + 0.2%;
[0026] After the lightening material is mixed with the continuously graded cement for the first time, it is mixed with the chemical admixture for the second time to obtain the continuously graded low-density oil well cement.
[0027] In this disclosure and possible embodiments, the mixing time for the first mixing is >5 minutes, and the homogenization rate is 100%.
[0028] In this disclosure and possible embodiments, the mixing time for the second mixing is >5 minutes, and the homogenization rate is 100%.
[0029] Thirdly, the low-density cement slurry comprises:
[0030] The continuous graded low-density oil well cement described in any of the first aspects.
[0031] The beneficial effects of this invention are as follows:
[0032] The continuously graded low-density oil well cement disclosed herein is produced by crushing, grinding, and screening cement clinker, natural gypsum, fly ash, slag powder, and silica fume to obtain continuously graded cement. This cement is then mixed with lightening material perlite and chemical admixtures. While adjusting the cement density, the particle size distribution between the cement and each material is optimized to maximize the packing ratio between the materials, thereby increasing tensile strength and reducing porosity and permeability. This prevents the migration of formation fluids along the cement stone matrix, effectively improving the cement sheath's resistance to fluid intrusion and further enhancing the early strength of the low-density cement stone. Compared with low-density cement slurry produced by conventional processes, the low-density cement slurry of this disclosure exhibits faster hydration during cement hydration, more stable strength development, better control of thickening time and fluidity during construction, and better cementing effect. Attached Figure Description
[0033] The above and other objects, features, and advantages of this disclosure will become clearer from the following description of embodiments with reference to the accompanying drawings, in which:
[0034] Figure 1 This is a particle size distribution diagram of low-density cement produced using conventional processes.
[0035] Figure 2 This is a particle size distribution diagram of low-density cement particles according to an embodiment of this disclosure. Detailed Implementation
[0036] The present disclosure is described below based on specific embodiments; however, it is worth noting that the present disclosure is not limited to these specific embodiments. In the following detailed description of the present disclosure, certain specific details are described in detail. However, those skilled in the art will fully understand the present disclosure for the parts not described in detail.
[0037] Furthermore, unless the context explicitly requires it, the words "comprising," "including," and similar terms throughout the specification and claims should be interpreted as including rather than exclusive or exhaustive; that is, meaning "including but not limited to."
[0038] The continuously graded low-density oil well cement disclosed herein is composed of continuously graded cement, weight-reducing materials, and chemical admixtures, wherein, by mass percentage:
[0039] Continuously graded cement: 42%–54% cement clinker, 5%–7% natural gypsum, 13%–19% fly ash, 10%–15% slag powder, and 7%–10% silica fume;
[0040] Lightening material: 2%–7% perlite
[0041] Chemical admixtures: 3%–5% accelerator, 0.7%–2% retarder, 0.06% rheology modifier, and 2% water loss reducer.
[0042] In one specific embodiment, the cement clinker is Oil Dragon G-grade oil well cement clinker; the natural gypsum, fly ash, slag powder, and silica fume are all commercially available products; the perlite has a bulk density ≥80kg / m³. 3 And ≤120kg / m 3 Volumetric water absorption rate ≤45%, volumetric buoyancy rate ≥80%.
[0043] In one specific embodiment, the early strength agent is a copolymer of potassium carbonate, polyaluminum chloride, sodium silicate, and calcium silicate; the retarder is aluminum sulfate, sodium carbonate, polyaluminum ferric sulfate, or activated light calcium carbonate; the rheology modifier is a copolymer of formaldehyde, acetone, triethanolamine, or sodium hydroxide; and the water loss reducing agent is a copolymer of 2-acrylamide, 2-methylpropanesulfonic acid, ammonium persulfate, sodium bisulfite, sodium hydroxide, or N-methylenebisacrylamide.
[0044] This disclosure discloses a method for preparing continuously graded low-density oil well cement, comprising the following steps:
[0045] 1. Cement clinker, natural gypsum, fly ash, slag powder, and silica fume are crushed, ground, and screened to obtain continuously graded cement.
[0046] 2. Mix the perlite with the continuously graded cement for the first time;
[0047] 3. The early strength agent, retarder, rheology modifier and fluid loss reducer are mixed with the primary mixture for a second time to obtain continuously graded low-density oil well cement.
[0048] In one specific embodiment, the control index for screening is: specific surface area: 320 + 10m 2 / kg, 45-micron fineness: 9.0 + 2.0%, SO3: 2.0 + 0.2%.
[0049] In one specific embodiment, the mixing time for the first mixing is >5 minutes, and the homogeneity of the mixture is 100%.
[0050] In one specific embodiment, the mixing time for the second mixing is >5 minutes, and the homogeneity of the mixture is 100%.
[0051] Example 1
[0052] The method of this invention is used to prepare continuously graded low-density oil well cement and low-density cement slurry, as follows:
[0053] I. Preparation of Continuously Graded Low-Density Oil Well Cement
[0054] 1. Preparation of raw materials for continuously graded low-density oil well cement:
[0055] Continuously graded cement: 54% oil well cement clinker (G grade), 6% natural gypsum, 13% fly ash, 15% slag powder, and 7% silica fume;
[0056] Lightening material: 5% perlite;
[0057] Chemical admixtures: 3% accelerator, 0.7% retarder, 0.06% rheology modifier, and 2% water loss reducer.
[0058] The accelerator consists of the following components by mass fraction: potassium carbonate 21%, polyaluminum chloride 18%, sodium silicate 48%, and calcium silicate 13%; the retarder consists of the following components by mass fraction: aluminum sulfate 22%, sodium carbonate 28%, polyaluminum ferric sulfate 31%, and activated light calcium carbonate 19%; the rheology modifier consists of the following components by mass fraction: formaldehyde 47%, acetone 41%, triethanolamine 5%, and sodium hydroxide 7%; and the water loss reducing agent consists of the following components by mass fraction: 2-acrylamide 27%, 2-methylpropanesulfonic acid 39%, ammonium persulfate 7%, sodium bisulfite 9%, sodium hydroxide 5%, and N,N-methylenebisacrylamide 13%.
[0059] 2. Preparation of continuously graded low-density oil well cement:
[0060] (1) Preparation of continuously graded cement:
[0061] Cement clinker and natural gypsum are crushed into powder particles with a particle size of <3mm using a roller crusher or jaw crusher.
[0062] After crushing cement clinker, natural gypsum, fly ash, slag powder, and silica fume, the mixture is ground in a ball mill and then screened by an air classifier. The controlled parameters are: specific surface area: 320. + 10m 2 / kg, 45-micron fineness: 9.0 + 2.0%, SO3: 2.0 + 0.2% yields continuously graded cement.
[0063] (2) First mixing:
[0064] Continuously graded cement is mixed with perlite for a mixing time of >5 minutes, and the homogeneity of the mixture is 100%.
[0065] (3) Second mixing:
[0066] The cement after the first mixing is mixed with chemical admixtures for a mixing time of >5 minutes, and the homogeneity of the mixture is 100%, thus obtaining the continuous graded low-density oil well cement of this embodiment.
[0067] 3. The effect of cement particle size distribution on
[0068] Particle size distribution tests were conducted on low-density cement produced by conventional processes and the continuously graded low-density oil well cement of this embodiment. The test results are as follows: Figure 1 and Figure 2 As shown.
[0069] from Figure 1 and Figure 2 The comparison results show that the continuously graded low-density oil well cement prepared in this embodiment has a more reasonable particle distribution and better particle gradation continuity.
[0070] II. Preparation of low-density cement slurry:
[0071] Weigh 100 parts of continuously graded low-density oil well cement and 60 parts of fresh water, and mix them evenly according to API 10B RP specifications to obtain low-density cement slurry.
[0072] 1. Performance test results of low-density cement slurry are shown in Table 1 below:
[0073] Table 1. Performance test data of low-density cement paste
[0074]
[0075]
[0076] As can be seen from the test results in Table 1 above, the obtained low-density cement slurry has zero free liquid, stable properties, good thickening time and rheological properties, and rapid strength development at low temperatures, which can meet the needs of on-site construction.
[0077] 2. Performance test data comparison
[0078] Table 2 shows a comparison of the performance data of low-density cement slurry produced by conventional processes with that of the low-density cement slurry in this embodiment:
[0079] Table 2 Comparative Test Data of Low-Density Cement Slurry
[0080]
[0081] As can be seen from the performance comparison test data in Table 2 above, the low-density cement slurry of this embodiment has a faster hydration rate during cement hydration, more stable strength development, better control of thickening time and fluidity during construction, and better cementing effect than the low-density cement slurry of conventional process.
[0082] The embodiments described above are merely illustrative of implementation methods of this disclosure, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of this patent disclosure. It should be noted that those skilled in the art can make various modifications, equivalent substitutions, and improvements without departing from the concept of this disclosure, and these all fall within the protection scope of this disclosure. Therefore, the protection scope of this patent disclosure should be determined by the appended claims.
Claims
1. A continuously graded low-density oil well cement, characterized in that, Its components include: Continuously graded cement, weight-reducing materials, and chemical admixtures; The continuously graded cement comprises cement clinker, natural gypsum, fly ash, slag powder, and silica fume. The screening index for the continuously graded cement is a specific surface area of 320. + 10 m 2 / kg, 45-micron fineness: 9.0 + 2.0%, SO3: 2.0 + 0.2%; The mixture of the weight-reducing material, the chemical admixture, and the continuously graded cement is the continuously graded low-density oil well cement.
2. The continuously graded low-density oil well cement according to claim 1, characterized in that: The lightening material is perlite.
3. The continuously graded low-density oil well cement according to claim 2, characterized in that: The bulk density of the perlite is ≥80 kg / m³. 3 And ≤120 kg / m 3 Volumetric water absorption rate ≤45%, volumetric buoyancy rate ≥80%.
4. The continuously graded low-density oil well cement according to any one of claims 1-3, characterized in that, The chemical admixture includes: Early strength agents, retarders, rheology modifiers, and water loss reducers.
5. The continuously graded low-density oil well cement according to claim 4, characterized in that: The early strength agent is composed of potassium carbonate, polyaluminum chloride, sodium silicate, and calcium silicate.
6. The continuously graded low-density oil well cement according to claim 5, characterized in that: The retarder is composed of aluminum sulfate, sodium carbonate, polyaluminum ferric sulfate and active light calcium carbonate.
7. The continuously graded low-density oil well cement according to claim 6, characterized in that: The rheology modifier is composed of formaldehyde, acetone, triethanolamine, and sodium hydroxide.
8. The continuously graded low-density oil well cement according to claim 7, characterized in that: The water loss reducing agent is composed of 2-acrylamide, 2-methylpropanesulfonic acid, ammonium persulfate, sodium bisulfite, sodium hydroxide, and N-methylenebisacrylamide.
9. The continuously graded low-density oil well cement according to any one of claims 5-8, characterized in that: By mass percentage, the cement clinker is 42%~54%, natural gypsum is 5%~7%, fly ash is 13%~19%, slag powder is 10%~15%, microsilica is 7%~10%, and the perlite is 2%~7%. Early strength agent 3%~5%, retarder 0.7%~2%, rheology modifier 0.06%, and water loss reducer 2%.
10. The method for preparing continuously graded low-density oil well cement according to any one of claims 1-9, characterized in that, include: Cement clinker and natural gypsum are crushed into mixed powder particles with a particle size of <3mm; Continuously graded cement is obtained by grinding and screening a mixture of fly ash, slag powder, silica fume, and the aforementioned mixed powder particles. The control index for screening is: specific surface area:
320. + 10 m 2 / kg, 45-micron fineness: 9.0 + 2.0%, SO3: 2.0 + 0.2%; After the lightening material is mixed with the continuously graded cement for the first time, it is mixed with the chemical admixture for the second time to obtain the continuously graded low-density oil well cement.
11. The method for preparing continuously graded low-density oil well cement according to claim 10, characterized in that: The mixing time for the first mixing step is >5 minutes, and the homogeneity of the mixture is 100%.
12. The method for preparing continuously graded low-density oil well cement according to claim 10, characterized in that: The mixing time for the second mixing is >5 minutes, and the homogenization rate is 100%.
13. A low-density cement slurry, characterized in that, Its components include: The continuously graded low-density oil well cement according to any one of claims 1-9.