Gelled material for repairing casing damage in thermal recovery wells for heavy oil and method of preparation and repairing cement slurry

Abstract

The application discloses a gelling material for repairing casing damage of a heavy oil thermal recovery well, a preparation method and a repairing cement slurry, and relates to the technical field of downhole repairing materials for oil fields.The gelling material is prepared from 50-65 parts of oil well cement, 25-32 parts of siliceous aggregate microfine powder, 8-15 parts of calcareous aggregate microfine powder, 0.5-2 parts of fiber powder and 1-2 parts of carbon black powder.The material forms a more stable and dense microstructure at high temperature through the synergistic effect of superfine active mineral powder and nano carbon black, thereby realizing excellent high-temperature strength stability and volume stability.

Description

Technical Field

[0001] This invention belongs to the field of oilfield downhole repair materials technology, and more specifically relates to a cementitious material for repairing casing damage in heavy oil thermal recovery wells, its preparation method, and repair cement slurry. Background Technology

[0002] my country has a wide distribution of heavy oil resources, and thermal extraction (mainly steam injection and steam drive) is the primary method of heavy oil development both domestically and internationally. However, during long-term, multi-round steam injection and extraction processes, the casing is constantly subjected to high temperature and high pressure, leading to frequent casing damage. Extensive casing damage forces the government to invest heavily each year in drilling new wells and repairing wells with damaged casings, causing significant economic losses to heavy oil fields. While domestic and international experts have done extensive work on casing damage in heavy oil fields, the problem of casing damage in thermal extraction wells remains fundamentally unresolved and has become one of the core technical challenges restricting the efficient development of heavy oil reservoirs.

[0003] The primary factor contributing to casing failure in heavy oil thermal recovery is axial compression deformation caused by thermal stress. In addition, creep and stress relaxation after repeated high and low temperature cycles, geological changes such as sand production in the oil reservoir, water absorption and expansion of mudstone, and slippage at rock interfaces, as well as poor cementing quality, are all significant factors leading to casing damage. Under the combined effect of these multiple factors, casing failure occurs due to necking deformation, breakage, and corrosion. This, coupled with the failure of the cement sheath, results in the loss of casing protection and severe disruption of the heavy oil flow path. When the formation has high water content, a large amount of formation water flows into the casing, leading to reduced oil extraction efficiency and increased costs.

[0004] Currently, the methods for preventing casing damage in heavy oil wells are not yet perfect. Whenever casing damage occurs, it is necessary to repair the casing and simultaneously refill the space between the casing and the formation with cementitious materials to block the flow channels between the casing and formation water. The performance of the repair material is crucial to the quality of the damaged casing repair. Current technical methods mainly involve using high-temperature resistant cementitious materials to refill the space between the casing and the formation. For example, the invention patent with publication number CN105086967A, entitled "An anti-channeling and plugging agent and a construction method for using it for regulating, plugging, and sealing," discloses an anti-channeling and plugging agent comprising a high-temperature resistant pre-plugging agent as a pre-plugging sluice, a reinforced gel plugging agent as an intermediate reinforced sluice, and a high-strength resin plugging agent as a post-sealing sluice. This agent features high temperature resistance, long-term stability, and good sealing performance, and its construction process is simple, effectively solving the gas / gas channeling phenomenon in heavy oil thermal recovery wells.

[0005] However, current solutions all have certain limitations. Organic plugging agents can effectively seal water layers and fill the space in damaged casing, but they suffer from poor durability and high cost. Conventional high-temperature cementing can only fill a limited space around the casing and cannot stabilize the surrounding formation; secondary casing damage will quickly occur during re-steam recovery.

[0006] Therefore, there is an urgent need to develop a new type of cementitious material that can be used simultaneously for repairing casing damage in heavy oil thermal recovery wells and reinforcing the surrounding formations, so as to synergistically solve the problems of high-temperature strength degradation, formation reinforcement, and good construction performance and cost. Summary of the Invention

[0007] To overcome the shortcomings and deficiencies of the existing technology, this invention provides a cementitious material, its preparation method, and a repair slurry for repairing casing damage in heavy oil thermal recovery wells. The purpose of this invention is to overcome the shortcomings of existing heavy oil thermal recovery well materials, such as easy strength degradation at high temperatures, easy volume shrinkage after thermal cycling, and reliance on high-cost special additives or complex formulations. This invention provides a cementitious material with readily available raw materials and balanced performance. Through the synergistic effect of ultrafine active mineral powder and nano-carbon black, this material forms a more stable and dense microstructure at high temperatures, thereby achieving excellent high-temperature strength stability and volume stability.

[0008] To address the problems existing in the prior art, the present invention is achieved through the following technical solution.

[0009] The first aspect of the present invention provides a cementitious material for repairing casing damage in heavy oil thermal recovery wells, the cementitious material being made of the following materials in parts by weight: 50 to 65 parts of oil well cement; 25-32 parts of siliceous aggregate fine powder, with a particle size D90 < 0.85 mm and a silica content > 60%; 8 to 15 parts of fine calcareous aggregate powder, with a particle size D90 < 0.85 mm and a calcium oxide content > 45%; 0.5 to 2 parts of fiber powder, the length of the fiber powder is <60μm, and the diameter of the fiber powder is 5-10μm; 1 to 2 parts of carbon black powder, with a particle size range of 20 nm to 50 nm.

[0010] More preferably, the oil well cement is Grade A oil well cement or Grade G high-resistance oil well cement that meets API standards.

[0011] More preferably, the siliceous aggregate fine powder is fine powder collected during the production of granite, basalt or quartzite concrete aggregate.

[0012] More preferably, the calcareous aggregate fine powder is fine powder collected during the production of limestone or calcite rock concrete aggregate.

[0013] More preferably, the fiber powder is carbon fiber powder.

[0014] More preferably, the carbon black powder is carbon black for rubber or pigments.

[0015] A second aspect of the present invention provides a method for preparing a cementitious material for repairing casing damage in heavy oil thermal recovery wells, comprising the following steps: S1. The oil well cement, siliceous aggregate fine powder and calcareous aggregate fine powder are respectively subjected to ultrafine grinding until the particle size D90 < 20μm to obtain ultrafine materials. S2. Add fiber powder and carbon black powder to the ultrafine material according to the weight parts, and mix them evenly to obtain the gelling material.

[0016] The third aspect of the present invention provides a repair cement slurry for repairing casing damage in heavy oil thermal recovery wells. The repair cement slurry comprises the cementing material described in the first aspect above, 60% water by mass of the cementing material, 0.2% to 0.5% drag-reducing agent by mass of the cementing material, 0.4% to 1.0% retarder by mass of the cementing material, and 1.5% to 2.5% fluid loss reducing agent by mass of the cementing material.

[0017] More preferably, the retarder is an organophosphonic acid retarder; the water loss reducing agent is an AMPS polymer water loss reducing agent; and the drag reducing agent is a ketaldehyde condensate drag reducing agent or a polycarboxylic acid drag reducing agent.

[0018] Compared with the prior art, the beneficial technical effects of the present invention are as follows: 1. The cementitious material of the present invention has excellent repair capabilities for damaged casing in heavy oil wells. This material has a small particle size distribution, allowing it to penetrate into the surrounding area of ​​the damaged casing and the formation. By solidifying the surrounding formation, it achieves the ability to repair and reinforce the casing, improving its resistance to damage caused by formation changes, formation water corrosion, and other factors.

[0019] 2. The cementitious material of the present invention has excellent high-temperature strength and stability: by adding siliceous aggregate fine powder, after steam injection is started, the formation is heated to a high temperature. The silica in the siliceous aggregate fine powder reacts with the hydration products of silicate cement to generate hydration products (hard silicate calcium stone, snow silicate calcium stone) with high-temperature resistance, ensuring that the cement stone has good high-temperature strength and stability after being heated to a high temperature. In addition, carbon fiber powder is added to the cementitious material, which helps to improve the ability of the hydration products to resist thermal stress damage caused by high and low temperature cycles, and avoids the cement stone from cracking and losing the function of the protective sleeve.

[0020] 3. The cementitious material of this invention has good water intrusion resistance. A large amount of nano-carbon black is added to the cementitious material. Carbon black is a hydrophobic material that fills the gaps in the cement stone. By utilizing the incompatibility mechanism between carbon black and cement, it resists or slows down the intrusion of formation water into the cement stone, thereby avoiding corrosion damage caused by formation water contacting the casing.

[0021] 4. The cementitious material of this invention has good economic and environmental benefits. Siliceous aggregate fine powder and calcareous aggregate fine powder are large amounts of waste generated during the production of concrete aggregates. Using siliceous aggregate fine powder and calcareous aggregate fine powder as the main components of the repair material can effectively reduce environmental pollution during the production of concrete aggregates, while significantly reducing the material cost of the cementitious material, thus achieving effective comprehensive utilization of waste. Attached Figure Description

[0022] Figure 1 This is a SEM image of the carbon fiber powder used in the cementitious material of this invention. Figure 2 This is a 70°C thickening curve of the cementitious material used for repairing damaged casing in a heavy oil thermal recovery well, as shown in Example 1 of the present invention. Detailed Implementation

[0023] The present invention will be further described in detail below with reference to specific embodiments, but the scope of protection of the present invention is not limited to the following embodiments.

[0024] Example 1 As a preferred embodiment of the present invention, this embodiment provides a cementitious material for repairing casing damage in heavy oil thermal recovery wells, which is prepared from the following basic raw materials by weight through pretreatment: The composition includes 50 parts oil well cement, 32 parts siliceous aggregate fine powder, 15 parts calcareous aggregate fine powder, 1 part fiber powder, and 2 parts carbon black powder. The oil well cement is API Grade A oil well cement; the siliceous aggregate fine powder is produced during the production of granite concrete aggregate, with a particle size D90 < 0.85 mm and a silica content greater than 60%; the calcareous aggregate fine powder is produced during the production of calcite rock concrete aggregate, with a particle size D90 < 0.85 mm and a calcium oxide content greater than 45%; the fiber powder has a length < 60 μm and a diameter of 5-10 μm; and the carbon black powder is rubber-grade carbon black with a particle size range of 20-50 nm.

[0025] The preparation method of the above-mentioned cementitious material is as follows: Grade A oil well cement, siliceous aggregate fine powder, and calcareous aggregate fine powder are put into a ball mill for ball milling according to the weight ratio of the components. After ball milling, the mixture is separated by an airflow separation device to make the D90 of the mixed powder 15.5μm. The ultrafine material obtained by grinding and separation is mixed with fiber powder and carbon black powder according to the weight ratio to obtain the cementitious material.

[0026] The cement slurry for repairing heavy oil thermal recovery wells was prepared according to the following proportions: 100% cementitious material + 60% water (by weight of cementitious material) + 0.5% drag-reducing agent (by weight of cementitious material) + 1.0% retarder (by weight of cementitious material) + 2.5% fluid loss reducing agent (by weight of cementitious material). Thickening time at 70℃, compressive strength and tensile strength at 70℃, and compressive strength at 315℃ were tested. The results are attached. Figure 2 As shown. The drag-reducing agent is a ketaldehyde condensate drag-reducing agent, the water loss reducing agent is an AMPS polymer water loss reducing agent, and the retarder is an organophosphonic acid retarder.

[0027] Example 2 As another preferred embodiment of the present invention, this embodiment provides a cementitious material for repairing casing damage in heavy oil thermal recovery wells, which is prepared from the following basic raw materials by weight through pretreatment: The composition includes 55 parts oil well cement, 28 parts siliceous aggregate fine powder, 13 parts calcareous aggregate fine powder, 2 parts fiber powder, and 2 parts carbon black powder. The oil well cement is API standard Grade G high-resistance oil well cement; the siliceous aggregate fine powder is produced during the production of quartzite concrete aggregate, with a particle size D90 < 0.85 mm and a silica content greater than 60%; the calcareous aggregate fine powder is produced during the production of calcite rock concrete aggregate, with a particle size D90 < 0.85 mm and a calcium oxide content greater than 45%; the fiber powder has a length < 60 μm and a diameter of 5-10 μm; and the carbon black powder is rubber-grade carbon black with a particle size range of 20-50 nm.

[0028] The preparation method of the above-mentioned cementitious material is as follows: G-grade high-resistance oil well cement, siliceous aggregate fine powder, and calcareous aggregate fine powder are put into a ball mill for ball milling according to the weight ratio of the components. After ball milling, the mixture is separated by an airflow separation device to make the D90 of the mixed powder 18.2μm. The ultrafine material obtained by grinding and separation is mixed with fiber powder and carbon black powder according to the weight ratio to obtain the cementitious material.

[0029] The cement slurry for repairing heavy oil thermal recovery wells was prepared according to the following proportions: 100% cementitious material + 60% water (by weight of cementitious material) + 0.2% drag-reducing agent (by weight of cementitious material) + 0.4% retarder (by weight of cementitious material) + 1.5% fluid loss reducing agent (by weight of cementitious material). Thickening time at 70℃, compressive strength and tensile strength at 70℃, and compressive strength at 315℃ were tested. The drag-reducing agent was a polycarboxylate drag-reducing agent, the fluid loss reducing agent was an AMPS polymer fluid loss reducing agent, and the retarder was an organophosphonic acid retarder.

[0030] Example 3 As another preferred embodiment of the present invention, this embodiment provides a cementitious material for repairing casing damage in heavy oil thermal recovery wells, which is prepared from the following basic raw materials by weight through pretreatment: The composition includes 60 parts oil well cement, 30 parts siliceous aggregate fine powder, 8 parts calcareous aggregate fine powder, 0.5 parts fiber powder, and 1.5 parts carbon black powder. The oil well cement is API standard Grade G high-resistance oil well cement; the siliceous aggregate fine powder is produced during the production of basalt concrete aggregate, with a particle size D90 < 0.85 mm and a silica content greater than 60%; the calcareous aggregate fine powder is produced during the production of limestone concrete aggregate, with a particle size D90 < 0.85 mm and a calcium oxide content greater than 45%; the fiber powder has a length < 60 μm and a diameter of 5-10 μm; the carbon black powder is pigment carbon black with a particle size range of 20-50 nm.

[0031] The preparation method of the above-mentioned cementitious material is as follows: Grade G high-resistance oil well cement, siliceous aggregate fine powder, and calcareous aggregate fine powder are weighed according to the component weight ratio and fed into a ball mill for ball milling. After ball milling, the powder is separated using an airflow separator, and the D90 of the mixed powder is 19.3 μm. The ultrafine material obtained from grinding and separation is then mixed evenly with fiber powder and carbon black powder according to the weight ratio to obtain the cementitious material.

[0032] The cement slurry for repairing heavy oil thermal recovery wells was prepared according to the following proportions: 100% cementitious material + 60% water (by weight of cementitious material) + 0.4% drag-reducing agent (by weight of cementitious material) + 0.6% retarder (by weight of cementitious material) + 2.0% fluid loss reducing agent (by weight of cementitious material). Thickening time at 70℃, compressive strength and tensile strength at 70℃, and compressive strength at 315℃ were tested. The drag-reducing agent was a ketaldehyde condensate drag-reducing agent, the fluid loss reducing agent was an AMPS polymer fluid loss reducing agent, and the retarder was an organophosphonic acid retarder.

[0033] Example 4 As another preferred embodiment of the present invention, this embodiment provides a cementitious material for repairing casing damage in heavy oil thermal recovery wells, which is prepared from the following basic raw materials by weight through pretreatment: The composition includes 65 parts oil well cement, 25 parts siliceous aggregate fine powder, 8 parts calcareous aggregate fine powder, 1 part fiber powder, and 1 part carbon black powder. The oil well cement is API standard Grade G high-resistance oil well cement; the siliceous aggregate fine powder is produced during the production of quartzite concrete aggregate, with a particle size D90 < 0.85 mm and a silica content greater than 60%; the calcareous aggregate fine powder is produced during the production of limestone concrete aggregate, with a particle size D90 < 0.85 mm and a calcium oxide content greater than 45%; the fiber powder has a length < 60 μm and a diameter of 5-10 μm; and the carbon black powder is rubber-grade carbon black with a particle size range of 20-50 nm.

[0034] The preparation method of the above-mentioned cementitious material is as follows: Grade G high-resistance oil well cement, siliceous aggregate fine powder, and calcareous aggregate fine powder are weighed according to the component weight ratio and fed into a ball mill for ball milling. After ball milling, the powder is separated using an airflow separator, and the D90 of the mixed powder is 16.8 μm. The ultrafine material obtained from grinding and separation is then mixed evenly with fiber powder and carbon black powder according to the weight ratio to obtain the cementitious material.

[0035] The cement slurry for repairing heavy oil thermal recovery wells was prepared according to the following proportions: 100% cementitious material + 60% water (by weight of cementitious material) + 0.5% drag-reducing agent (by weight of cementitious material) + 0.6% retarder (by weight of cementitious material) + 2.0% fluid loss reducing agent (by weight of cementitious material). Thickening time at 70℃, compressive strength and tensile strength at 70℃, and compressive strength at 315℃ were tested. The drag-reducing agent was a ketaldehyde condensate drag-reducing agent, the fluid loss reducing agent was an AMPS polymer fluid loss reducing agent, and the retarder was an organophosphonic acid retarder.

[0036] Comparative Experiment 1 Using G-grade oil well cement as the base material, a repair cement slurry was prepared. The experimental formula was: 100% G-grade oil well cement + 35% quartz sand (by weight of G-grade oil well cement) + 0.2% drag reducer (by weight of G-grade oil well cement) + 0.4% retarder (by weight of G-grade oil well cement) + 1.5% fluid loss reducer (by weight of G-grade oil well cement) + 60% water (by weight of G-grade oil well cement). Thickening time at 70℃, compressive strength and tensile strength at 70℃, and compressive strength and tensile strength at 315℃ were tested.

[0037] Comparative Experiment 2 Polymer-based repair materials were used, with the following composition: 100% modified epoxy resin + 8% (by weight) imidazole curing agent (by weight) of modified epoxy resin + 6% (by weight) glycidyl ether toughening agent (by weight) of modified epoxy resin + 6% (by weight) reactive diluent of modified epoxy resin + 10% (by weight) quartz powder (by weight) of modified epoxy resin. Thickening time at 70℃, compressive and tensile strength at 70℃, and compressive and tensile strength at 315℃ were tested. The experimental results are shown in the table below:

[0038] The test results of Examples 1-4 and the comparative experiments show that the thickening time at 70℃ for Examples 1-4 and Comparative Experiments 1-2 is between 189-259 min. The compressive strength at 70℃ and 7 days meets the mechanical performance requirements of the repair material. However, the tensile strength at 70℃ and 7 days varies greatly. The tensile strength of Examples 1-4 is in the range of 1.43-2.21 MPa, which, although much lower than the tensile strength of the resin system, is much better than the tensile strength of Comparative Experiment 1. After curing at 315℃, the compressive and tensile strength of Comparative Experiment 2 shows a severe decline, almost losing its mechanical properties and failing to provide protection for the casing of heavy oil thermal recovery wells.

Claims

1. A cementitious material for repairing damaged casing in heavy oil thermal recovery wells, characterized in that, The cementitious material is made from the following materials in parts by weight: 50 to 65 parts of oil well cement; 25-32 parts of siliceous aggregate fine powder, with a particle size D90 < 0.85 mm and a silica content > 60%; 8 to 15 parts of fine calcareous aggregate powder, with a particle size D90 < 0.85 mm and a calcium oxide content > 45%; 0.5 to 2 parts of fiber powder, the length of the fiber powder is <60μm, and the diameter of the fiber powder is 5-10μm; 1 to 2 parts of carbon black powder, with a particle size range of 20 nm to 50 nm.

2. The cementitious material for repairing casing damage in heavy oil thermal recovery wells as described in claim 1, characterized in that: The oil well cement is either Grade A oil well cement or Grade G high-resistance oil well cement that meets API standards.

3. The cementitious material for repairing casing damage in heavy oil thermal recovery wells as described in claim 1, characterized in that: The siliceous aggregate fine powder is the fine powder collected during the production of granite, basalt or quartzite concrete aggregate.

4. The cementitious material for repairing casing damage in heavy oil thermal recovery wells as described in claim 1, characterized in that: The calcareous aggregate fine powder is the fine powder collected during the production of limestone or calcite rock concrete aggregate.

5. The cementitious material for repairing casing damage in heavy oil thermal recovery wells as described in claim 1, characterized in that: The fiber powder is carbon fiber powder.

6. The cementitious material for repairing casing damage in heavy oil thermal recovery wells as described in claim 1, characterized in that: The carbon black powder is for rubber or pigment use.

7. The method for preparing the cementitious material for repairing casing damage in heavy oil thermal recovery wells as described in any one of claims 1-6, characterized in that, Includes the following steps: S1. The oil well cement, siliceous aggregate fine powder and calcareous aggregate fine powder are respectively subjected to ultrafine grinding until the particle size D90 < 20μm to obtain ultrafine materials. S2. Add fiber powder and carbon black powder to the ultrafine material according to the weight parts, and mix them evenly to obtain the gelling material.

8. A repair cement slurry for repairing casing damage in heavy oil thermal recovery wells, characterized in that: The repair cement grout comprises the cementitious material described in any one of claims 1-6, 60% water by weight of the cementitious material, 0.2% to 0.5% drag-reducing agent by weight of the cementitious material, 0.4% to 1.0% retarder by weight of the cementitious material, and 1.5% to 2.5% water-loss reducing agent by weight of the cementitious material.

9. The repair cement grout for repairing casing damage in heavy oil thermal recovery wells as described in claim 8, characterized in that: The retarder is an organophosphonic acid retarder; the water loss reducing agent is an AMPS polymer water loss reducing agent; and the drag reducing agent is a ketaldehyde condensate drag reducing agent or a polycarboxylic acid drag reducing agent.

Images