High-temperature-resistant material for well cementation cement slurry, well cementation cement slurry and application of high-temperature-resistant material in thermal oil recovery

Abstract

The invention belongs to the technical field of drilling compositions, and particularly relates to a high-temperature-resistant material for well cementation cement slurry, the well cementation cement slurry and application of the high-temperature-resistant material in thermal oil recovery. The high-temperature-resistant material for the well cementation cement slurry, provided by the invention, is prepared from the following components in percentage by mass: 50 to 70 percent of cristobalite and 30 to 50 percent of metakaolin. The cristobalite and the metakaolin are adopted to form the high-temperature-resistant material, the high-temperature-resistant material can react with a hydration product calcium hydroxide of the cement paste at the temperature of 150 DEG C when being used in cooperation with the cement paste, a scolecite product with stable strength at the high temperature is generated, and set cement can have high strength at the high temperature; and the strength is kept not attenuated in the ultrahigh-temperature and normal-temperature alternate curing period of 300-350 DEG C, and the adverse effect that the water content is increased sharply due to the fact that the cement sheath is prone to thermal damage in the thermal recovery process of the thermal recovery well is prevented, so that the service life of the thermal recovery well is prolonged.

Description

Technical Field

[0001] This invention relates to the field of drilling composition technology, specifically to a high-temperature resistant material for cementing slurry, cementing slurry, and its application in thermal oil recovery. Background Technology

[0002] Currently, the application of high-temperature resistant cement slurry is mainly in heavy oil wells. Because the properties of heavy oil are strongly correlated with temperature, heating it can significantly increase its fluidity and reduce its viscosity, thus achieving a more ideal extraction effect. Studies have shown that for every 10°C increase in temperature, the viscosity of heavy oil decreases by half. Therefore, thermal recovery is currently the main method for heavy oil development. However, ordinary cement sheaths have poor heat resistance. During steam injection, the strength of the cement stone decreases significantly in the high-temperature steam environment, leading to sheath cracking and damage, causing annular seal failure, oil-gas-water channeling, and severely shortening the well's lifespan. Therefore, high-temperature resistance has become a rigid requirement for cementing heavy oil wells. Furthermore, the extraction process faces periodic temperature fluctuations, placing high demands on the high-temperature stability and other mechanical properties of the cement sheath.

[0003] Currently, the most commonly used high-temperature resistant cementing slurry system is silicate cement slurry with added silica sand. Its principle relies on the high-temperature resistance of SiO2. Through exploration and practice, it has been found that the reasonable silica sand content is 30%–40%. Depending on the amount added, the upper limit of high-temperature resistance is 160℃–190℃, which can only meet the needs of some low-temperature thermal recovery wells. When the thermal recovery temperature reaches 300℃–350℃, the silica-added cement stone, after long-term curing, will lose most of its strength, and its permeability will increase sharply, seriously affecting the sealing quality of the cement sheath and the life of the oil well. Summary of the Invention

[0004] The purpose of this invention is to provide a high-temperature resistant material for cementing slurry, which solves the problem of poor strength of cement slurry under ultra-high temperature conditions after curing in the prior art.

[0005] The second objective of this invention is to provide a cementing slurry that solves the problem of poor strength of cement slurry under ultra-high temperature conditions after curing in the prior art.

[0006] The third objective of this invention is to provide an application of cement slurry in thermal oil recovery, solving the problem of poor strength of cement slurry under ultra-high temperature conditions after curing in the thermal oil recovery process in the prior art.

[0007] To solve the above-mentioned technical problems, the technical solution of the high-temperature resistant material for cementing slurry of the present invention is as follows:

[0008] A high-temperature resistant material for cementing slurry, wherein the high-temperature resistant material is composed of 50% to 70% cristobalite and 30% to 50% metakaolinite by mass.

[0009] This invention improves upon existing technology by providing a high-temperature resistant material for cementing slurry. This material, composed of cristobalite and metakaolin, reacts with the hydration product calcium hydroxide of the cement slurry at 150°C to generate a calcium zeolite product with stable strength at high temperatures. This allows the cement slurry to maintain high strength at ultra-high temperatures of 300–350°C after curing, and its strength remains consistent during alternating high-temperature and normal-temperature curing. This prevents thermal damage to the cement sheath during thermal recovery, which can lead to a surge in water content and thus extend the lifespan of the thermal recovery well. More preferably, the high-temperature resistant material consists of 55%–65% cristobalite and 35%–45% metakaolin by mass.

[0010] To further improve the crystal structure of cristobalite and metakaolinite in high-temperature resistant materials, preferably, the cristobalite is obtained by calcining quartz at 1450℃~1600℃ for 1.5~3.5h, and the metakaolinite is obtained by calcining kaolinite at 600℃~700℃ for 1.5~3.5h. More preferably, the cristobalite is obtained by calcining quartz at 1500~1600℃ for 1.5~3h, and the metakaolinite is obtained by calcining kaolinite at 650℃~700℃ for 1.5~3h.

[0011] To further improve the high-temperature resistance of the high-temperature resistant material, preferably, the particle size of the high-temperature resistant material is 180-250 mesh.

[0012] The technical solution of the cementing slurry of the present invention is as follows:

[0013] A cementing slurry comprising 100-120 parts by weight of cement, 60-100 parts by weight of the aforementioned high-temperature resistant material, and 80-92 parts by weight of water.

[0014] The cement slurry provided by this invention, by adding the aforementioned high-temperature resistant material to the cement, can react with the hydration product calcium hydroxide of the cement slurry at 150°C to generate a calcium zeolite product with stable strength at high temperatures. This allows the cement slurry to have high strength at ultra-high temperatures of 300-350°C after curing, and to maintain its strength without decay during alternating high-temperature and normal-temperature curing. This prevents the cement sheath from being easily damaged by heat during the thermal extraction process of thermal wells, which can cause a surge in water content and thus extend the life of the thermal well.

[0015] To further improve the elasticity and toughness of cement slurry under periodic temperature changes after curing, preferably, the cement slurry includes 2.8 to 4 parts of composite fiber, which is composed of inorganic fiber and polyester fiber in a mass ratio of (1 to 1.3): (1.8 to 3).

[0016] To further improve the viscosity and flowability of the cement slurry, preferably, the inorganic fiber has a particle size of 15-16 mesh and the polyester fiber has a particle size of 5-20 mesh.

[0017] To further improve the overall performance of the cement slurry, preferably, the cement slurry is composed of 100-120 parts by weight of cement, 60-100 parts by weight of the aforementioned high-temperature resistant material, 80-92 parts by weight of water, 2.8-4 parts by weight of composite fiber, 2-3 parts by weight of expanding agent, 2-4 parts by weight of fluid loss reducing agent, 2-4 parts by weight of setting accelerator, and 1-2 parts by weight of drag reducing agent. The expanding agent, used in the cement slurry, can prevent micro-shrinkage after curing, reduce permeability, and seal flow channels. Micro-expansion can improve interfacial bonding ability, and micro-thixotropy can reduce free water, among other combined effects. The drag reducing agent can significantly improve the initial fluidity of the cement slurry, improve its rheological properties, and has a good dispersing and drag-reducing effect.

[0018] Application of a cementing slurry in thermal oil recovery.

[0019] To further adapt to thermal oil recovery at different temperatures, preferably, the temperature during the thermal oil recovery process is 300–350°C.

[0020] The application of the cementing slurry provided by this invention in thermal oil recovery involves using the cementing slurry during the thermal oil recovery process. It reacts with calcium hydroxide, a hydration product of the cement slurry, at 150°C to generate calcium zeolite products with stable strength at high temperatures. This allows the cementing slurry to maintain high strength at ultra-high temperatures of 300–350°C after injection and curing in the oil well, and its strength remains unchanged during alternating high-temperature and normal-temperature curing. This prevents thermal damage to the cement sheath during thermal recovery, which can lead to a surge in water content and thus extend the lifespan of the thermal recovery well. Furthermore, this cementing slurry exhibits excellent engineering properties and can meet the cementing construction requirements during thermal oil recovery. Detailed Implementation

[0021] The technical concept of the high-temperature resistant material for cementing slurry of the present invention is as follows:

[0022] A high-temperature resistant material for cementing slurry is disclosed, comprising 50%–70% cristobalite and 30%–50% metakaolinite by mass. This high-temperature resistant material, composed of cristobalite and metakaolinite, reacts with the hydration product calcium hydroxide (CH) of the cement slurry at 150°C to generate a calcium zeolite product with stable strength at high temperatures. Furthermore, cristobalite and metakaolinite themselves possess good high-temperature resistance, and their synergistic effect with the formed calcium zeolite enables the cement stone to maintain high strength after ultra-high temperature curing at 300–350°C. This strength is also maintained during alternating high-temperature and normal-temperature curing, preventing thermal damage to the cement sheath during thermal extraction and thus extending the lifespan of the thermal extraction well.

[0023] A cementing slurry comprising 100-120 parts by weight of cement, 60-100 parts by weight of the aforementioned high-temperature resistant material, and 80-92 parts by weight of water.

[0024] In a specific implementation, the cement is Grade G oil well cement.

[0025] In a specific embodiment, the expanding agent is composed of sulfate-based materials and acrylamide polymers, the water loss reducing agent is polymerized from sulfonate and acrylamide, the setting accelerator is composed of chloride and nitrate, and the drag reducing agent is polymerized from formaldehyde and acetone. The water loss reducing agent utilizes polymer materials to adsorb onto the surface of cement particles in the cement slurry, forming a cross-linked network within the cement slurry system after cross-linking, which further improves the overall performance of the cement slurry.

[0026] In a specific embodiment, the inorganic fiber is XJDL-002 inorganic fiber purchased from Henan Xinxing New Material Technology Co., Ltd., and the particle size of XJDL-002 inorganic fiber is 15-16 mesh; the polyester fiber is polysilicon fiber sealant purchased from Henan Longxiang Petroleum Additives Co., Ltd., and the particle size is 5-20 mesh. The polysilicon fiber sealant is composed of polyester fiber and terephthalic acid, wherein the content of polyester fiber is 92-94%.

[0027] In a specific implementation, the expanding agent is XJP-1 purchased from Henan Xinxing New Material Technology Co., Ltd., the water loss reducing agent is XJL-2S purchased from Henan Xinxing New Material Technology Co., Ltd., the coagulant accelerator is XJQ-66S purchased from Henan Xinxing New Material Technology Co., Ltd., and the drag reducing agent is XJZ-1 purchased from Henan Xinxing New Material Technology Co., Ltd.

[0028] The embodiments of the present invention will be further described below with reference to specific examples. Unless otherwise specified, the chemical reagents involved in the following examples are all commercially available conventional products.

[0029] I. Specific Embodiments of the High-Temperature Resistant Material for Cementing Slurry of the Present Invention

[0030] Example 1

[0031] The high-temperature resistant material for cementing slurry provided in this embodiment is composed of 50% cristobalite and 50% metakaolinite by mass. The cristobalite is obtained by calcining quartz at 1450°C for 3.5 hours, and the metakaolinite is obtained by calcining kaolinite at 600°C for 3.5 hours. The particle size of the high-temperature resistant material is 180 mesh.

[0032] Example 2

[0033] The high-temperature resistant material for cementing slurry provided in this embodiment is composed of 55% cristobalite and 45% metakaolinite by mass. The cristobalite is obtained by calcining quartz at 1600℃ for 1.5h, and the metakaolinite is obtained by calcining kaolinite at 700℃ for 1.5h. The particle size of the high-temperature resistant material is 250 mesh.

[0034] Example 3

[0035] The high-temperature resistant material for cementing slurry provided in this embodiment is composed of 65% cristobalite and 35% metakaolinite by mass. The cristobalite is obtained by calcining quartz at 1500℃ for 3 hours, and the metakaolinite is obtained by calcining kaolinite at 650℃ for 3 hours. The particle size of the high-temperature resistant material is 200 mesh.

[0036] Example 4

[0037] The high-temperature resistant material for cementing slurry provided in this embodiment is composed of 70% cristobalite and 30% metakaolinite by mass. The cristobalite is obtained by calcining quartz at 1550°C for 2 hours, and the metakaolinite is obtained by calcining kaolinite at 700°C for 2 hours. The particle size of the high-temperature resistant material is 200 mesh.

[0038] II. Specific Embodiments of the Cementing Slurry of the Present Invention

[0039] The formulation of the cement slurry of the present invention is shown in Table 1.

[0040] Table 1. Formulation composition of cement slurry

[0041]

[0042]

[0043] The cement slurry provided in Example 5 is composed of the following components in parts by weight: 100 parts of Grade G oil well cement, 60 parts of the high-temperature resistant material of Example 1, 4 parts of composite fiber, 2 parts of expansion agent, 3 parts of fluid loss reducing agent, 4 parts of setting accelerator, 1 part of drag reducing agent, and 80 parts of water. The composite fiber is composed of 1.3 parts of inorganic fiber and 2.7 parts of polysilicon fiber plugging agent (2.484-2.538 parts of polyester fiber).

[0044] The cement slurry provided in Example 6 is composed of the following components in parts by weight: 100 parts of Grade G oil well cement, 80 parts of the high-temperature resistant material of Example 2, 4 parts of composite fiber, 2 parts of expansion agent, 2 parts of fluid loss reducing agent, 2 parts of setting accelerator, 1 part of drag reducing agent, and 85 parts of water. The composite fiber is composed of 1 part of inorganic fiber and 3 parts of polysilicon fiber plugging agent (2.76-2.82 parts of polyester fiber).

[0045] The cement slurry provided in Example 7 is composed of the following components in parts by weight: 100 parts of Grade G oil well cement, 100 parts of the high-temperature resistant material of Example 3, 3 parts of composite fiber, 2 parts of expansion agent, 4 parts of fluid loss reducing agent, 2 parts of setting accelerator, 2 parts of drag reducing agent, and 92 parts of water. The composite fiber is composed of 1 part of inorganic fiber and 2 parts of polysilicon fiber plugging agent (1.84-1.88 parts of polyester fiber).

[0046] The cement slurry provided in Example 8 consists of the following components in parts by weight: 100 parts of Grade G oil well cement, 60 parts of the high-temperature resistant material from Example 4, 4 parts of composite fiber, 2 parts of expansion agent, 3 parts of fluid loss reducing agent, 4 parts of setting accelerator, 1 part of drag reducing agent, and 80 parts of water. The composite fiber consists of 1.3 parts of inorganic fiber and 2.7 parts of polysilicon fiber plugging agent (2.484-2.538 parts of polyester fiber).

[0047] III. Specific Embodiments of the Application of the Cementing Slurry of the Present Invention in Thermal Oil Recovery

[0048] Example 9

[0049] The application of cement slurry in thermal oil recovery provided in this embodiment involves injecting the cement slurry from Example 5 into an oil well for thermal oil recovery, where the temperature reaches as high as 350°C.

[0050] IV. Comparative Example

[0051] Comparative Example 1

[0052] 100 parts of Grade G oil well cement, 60 parts of quartz sand, 4 parts of composite fiber, 2 parts of expansion agent, 3 parts of fluid loss reducer, 4 parts of coagulation accelerator, 1 part of drag reducer, and 80 parts of water. The composite fiber is composed of 1.3 parts of inorganic fiber and 2.7 parts of polysilicon fiber plugging agent.

[0053] Comparative Example 2

[0054] 100 parts of Grade G oil well cement, 60 parts of quartz sand, 3 parts of composite fiber, 2 parts of expansion agent, 3 parts of fluid loss reducer, 4 parts of coagulation accelerator, 1 part of drag reducer, and 80 parts of water. The composite fiber consists of 1 part of inorganic fiber and 2 parts of polysilicon fiber plugging agent.

[0055] V. Experimental Examples

[0056] This experimental example tested the performance of cement slurry according to the People's Republic of China Petroleum and Natural Gas Industry Standard GB / T19139-2012. The test results are shown in Table 2. 35℃*48h*0.1MPa refers to testing the compressive strength and elastic modulus of the cement stone after the cement slurry is poured into a mold and cured at 35℃×0.1MPa for 48 hours. 300℃*168h*21MPa refers to testing the compressive strength of the cement stone after the cement slurry is poured into a mold and cured at 300℃×21MPa for 168 hours. 210℃*28d*21MPa is similar to the above methods and will not be described in detail here.

[0057] Table 2 Performance Tests of Cementing Slurry

[0058]

[0059] As shown in Table 2, the cement slurry provided by this invention can maintain high compressive strength under high temperature conditions (300℃, 210℃) without compressive strength degradation during temperature changes, indicating that the cement slurry provided by this invention has good high-temperature strength stability. Furthermore, it still has good elastic modulus under high temperature conditions (300℃), indicating that the cement slurry provided by this invention has good elasticity and toughness after curing. Comparing the cement slurry provided by this invention with the comparative examples using quartz sand, although Comparative Examples 1 and 2 showed good compressive performance and elastic modulus under conditions of 35℃*48h*0.1MPa and 300℃*168h*21MPa, the compressive strength of the cement stone decreased sharply during long-term curing at high temperature (210℃*28d*21MPa), indicating that the cement slurry using quartz sand cannot achieve high-temperature strength stability over a long period.

[0060] Finally, it should be noted that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A high-temperature resistant material for cementing slurry, characterized in that, The high-temperature resistant material is composed of 50% to 70% cristobalite and 30% to 50% metakaolinite by mass.

2. The high-temperature resistant material for cementing slurry as described in claim 1, characterized in that, The cristobalite is obtained by calcining quartz at 1450℃~1600℃ for 1.5~3.5h, and the metakaolin is obtained by calcining kaolin at 600℃~700℃ for 1.5~3.5h.

3. The high-temperature resistant material for cementing slurry as described in claim 1 or 2, characterized in that, The particle size of the high-temperature resistant material is 180-250 mesh.

4. A cementing slurry, characterized in that, The cementing slurry comprises 100-120 parts by weight of cement, 60-100 parts by weight of the high-temperature resistant material as described in any one of claims 1-3, and 80-92 parts by weight of water.

5. The cementing slurry as described in claim 4, characterized in that, The cementing slurry includes 2.8 to 4 parts of composite fiber, which is composed of inorganic fiber and polyester fiber in a mass ratio of (1 to 1.3): (1.8 to 3).

6. The cementing slurry as described in claim 5, characterized in that, The inorganic fiber has a particle size of 15-16 mesh, and the polyester fiber has a particle size of 5-20 mesh.

7. The cementing slurry as described in claim 4, characterized in that, The cement slurry is composed of 100-120 parts by weight of cement, 60-100 parts by weight of the high-temperature resistant material, 80-92 parts by weight of water, 2.8-4 parts by weight of composite fiber, 2-3 parts by weight of expansion agent, 2-4 parts by weight of fluid loss reducing agent, 2-4 parts by weight of setting accelerator and 1-2 parts by weight of drag reducing agent.

8. The application of a cementing slurry as described in any one of claims 4-7 in thermal oil recovery.

9. The application of the cementing slurry as described in claim 8 in thermal oil recovery, characterized in that, The temperature during the thermal oil recovery process is 300–350°C.

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