A high-temperature resistant plugging and sealing agent for formation leakage oil wells, and its preparation method and plugging method

Abstract

The present invention belongs to the field of oilfield chemistry, and discloses a high-temperature resistant plugging and sealing agent for formation leakage oil wells, a preparation method thereof, and a plugging method. The high-temperature resistant plugging and sealing agent consists of two segment plugs, the first segment is a plugging agent, and the second segment is a high-temperature resistant sealing agent. The plugging agent is made by mixing G-grade oil well cement, quicklime, and plant fiber particles in a weight ratio of 7:1:2. The high-temperature resistant sealing agent is prepared by adding an accelerator and a curing agent to a phenolic resin. The high-temperature resistant plugging and sealing agent is used for plugging and sealing on-site, and the leakage well section is plugged by a secondary squeezing and displacement method. After the plugging agent to be squeezed in is in an initial setting state and the pressure is diffused, a pipe is lowered and flushed to a reserved gray surface position to accurately control the position of the gray surface. The one-time plugging and secondary plugging process of the present invention can achieve effective plugging of the target layer, ensure the construction effect, accurately control the position of the reserved gray surface, ensure safe and reliable construction, and meet geological requirements.

Description

Technical Field

[0001] The invention belongs to the field of oilfield chemistry and relates to a high-temperature resistant plugging and sealing agent for formation leakage oil wells and a preparation method and a plugging method thereof, and is particularly suitable for plugging steam-huffling formation leakage oil wells. Background Art

[0002] In the mid-to-late stages of oilfield development, water production from oil wells has become a major challenge. Repeated cycles of steam stimulation have severely damaged the reservoir casing and the cement sheath surrounding it. Casing leakage and pipe crossflow have led to a sharp increase in the water cut in the wells, resulting in the shutdown of many wells in the block due to high water cuts. Conventional plugging agents, solid-phase mud, and even temporary plugging balls have proven ineffective in treating these wells with water production and severe formation leakage.

[0003] Invention patent CN 103509534 A provides a plugging agent for oil drilling, comprising the following components: Component A: 60-80 parts by weight of calcium carbonate and / or barium carbonate; Component B: 15-25 parts by weight of lime powder and / or Grade G cement; and Component C: 5-15 parts by weight of a fibrous material. This application omits the "calcium carbonate and / or barium carbonate" designation. The plugging agent exhibits an expansion effect and can form a network structure, effectively retaining the material in severely leaking formations. Summary of the Invention

[0004] In view of the shortcomings of the existing technology, the purpose of the present invention is to invent a method for preparing a high-temperature resistant plugging sealing agent for formation leakage oil wells and a sealing process. This process can not only effectively seal the water in the water-containing leakage oil layer of the steam stimulation well, ensuring the sealing effect of the steam stimulation well leakage well, but also accurately control the reserved ash surface, thereby effectively solving the water leakage problem of the steam stimulation well leakage well.

[0005] In order to achieve the above objectives, the technical solutions of the present invention are as follows:

[0006] A high-temperature resistant plugging and sealing agent for formation leakage oil wells is composed of two plug segments. The first segment is a plugging agent that has a plugging and sealing effect, and the second segment is a high-temperature resistant sealing agent that has a plugging and sealing effect. The plugging agent is composed of G-grade oil well cement, quicklime and plant fiber particles.

[0007] Furthermore, the plugging agent is prepared by mixing G-grade oil well cement, quicklime and plant fiber particles in a weight ratio of 7:1:2.

[0008] Furthermore, the plugging agent is prepared by mixing clean water and oil well G grade cement into a cement slurry in advance, with a water-cement ratio of 1:1.25 and a density of 1.65 g / cm 3 ~1.75g / cm 3Then add quicklime and plant fiber particles to the cement slurry, add 0.5% to 1.5% mass fraction of accelerator and 1% to 1.5% mass fraction of fluid loss additive, and control the density at 1.75g / cm 3 ~1.85g / cm 3 , ensuring good pumpability.

[0009] Furthermore, the setting accelerator is RK-51S oil well cement setting accelerator and early strength agent.

[0010] Furthermore, the fluid loss agent is SL-2 high temperature and salt resistance fluid loss agent.

[0011] Furthermore, the high temperature resistant sealing agent is prepared by adding an accelerator and a curing agent to the phenolic resin, and the curing time is controlled by the amount of the curing agent and the accelerator added.

[0012] Furthermore, the accelerator is 0.35 mol / L sodium sulfate solution.

[0013] Furthermore, the curing agent is a 12 mol / L hydrochloric acid solution.

[0014] Furthermore, the preparation method of the high temperature resistant sealant is as follows: 1% by mass of 0.35 mol / L sodium sulfate accelerator and 0.5% by mass of 12 mol / L hydrochloric acid curing agent are added to the phenolic resin and mixed evenly to form the high temperature resistant sealant.

[0015] A method for plugging a formation leaking oil well comprises the following steps: using the high-temperature resistant leak-proof sealing agent prepared by the present invention to perform leak-proof sealing on-site; plugging the leaking well section by a secondary squeezing and displacement method; and after the squeezed-in leak-proof sealing agent is in an initial setting state and the pressure has been diffused, flushing to a reserved gray surface position by a lower pipe string is carried out to accurately control the position of the gray surface.

[0016] Furthermore, the method includes the following steps: lowering the oil pipe into the casing, configuring a high-temperature resistant plugging and sealing agent, which is composed of a plugging agent and a high-temperature resistant sealing agent. During construction, the plugging agent is first injected from the oil pipe into the high-permeability oil-loss layer with a pump truck, and pumped into place with clean water. Then, the high-temperature resistant sealing agent is injected from the oil pipe into the low-permeability oil layer and the high-permeability oil layer with a pump truck, and the plugging slurry is replaced with clean water. Generally, the upper plane of the sealing agent is 30 meters above the upper boundary of the oil layer, and the displacement pressure does not exceed 21Mpa.

[0017] The beneficial effects of the present invention compared with the prior art are:

[0018] (1) When the plugging agent is hydrated, it forms a cohesive structure with bulky properties, which plays a role of bridging and temporary plugging, preventing the loss of injected slurry and blocking large pores. It can effectively block the large pores in the leaking well section and achieve the purpose of plugging.

[0019] (2) The high-temperature resistant sealing agent can withstand temperatures above 350°C. After sealing, it can form an effective heat-resistant barrier outside the formation or leakage point, effectively blocking the leakage point of the steam well casing and water leakage outside the pipe.

[0020] (3) The one-time plugging and two-time plugging process of the present invention can effectively plug the target layer and ensure the construction effect.

[0021] (4) After the pressure of the high-temperature resistant leak-proof sealing agent diffuses, the down-pipe flushing method is adopted to accurately control the position of the reserved gray surface, ensure safe and reliable construction, and meet geological requirements. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The present invention will be further described below with reference to the accompanying drawings and examples.

[0023] Figure 1 Schematic diagram of the method for plugging formation leakage oil wells.

[0024] Among them: 1. Casing; 2. Oil pipe; 3. Low permeability oil layer; 4. High permeability oil loss layer; 5. Sealing agent; 6. Clean water; 7. High temperature resistant sealing agent. DETAILED DESCRIPTION

[0025] To provide a clearer understanding of the technical features, objectives, and beneficial effects of the present invention, the technical solutions of the present invention are described in detail below with reference to the following specific examples. However, these examples are not to be construed as limiting the scope of the present invention. Unless otherwise specified, the experimental methods employed in the present invention are conventional methods, and the experimental equipment, materials, and reagents used are all commercially available.

[0026] Example 1

[0027] The high-temperature resistant plugging and sealing agent for formation leakage oil wells of the present invention is composed of two segments. The first segment is a plugging agent with a plugging and sealing effect, and the second segment is a high-temperature resistant sealing agent with a plugging and sealing effect.

[0028] The configuration method of the plugging agent during on-site construction is: first mix clean water and oil well G grade cement into cement slurry, the water-cement ratio of the cement slurry is 1:1.25, and the density is 1.65g / cm 3 ~1.75g / cm 3 Then, quicklime and plant fiber particles are added to the cement slurry. The weight ratio of G-grade oil well cement, quicklime and plant fiber particles is 7:1:2. Then, 0.5% to 1.5% of the total mass of oil well cement accelerator and early strength agent are added, and the mass fraction of SL-2 high temperature and salt resistance rate loss agent is 1% to 1.5%. The density is controlled at 1.75g / cm 3 ~1.85g / cm 3 , ensuring good pumpability.

[0029] The preparation method of the high-temperature resistant sealant is as follows: 1% by mass of a 0.35 mol / L sodium sulfate accelerator and 0.5% by mass of a 12 mol / L hydrochloric acid curing agent are added to the phenolic resin and mixed evenly to form the high-temperature resistant sealant.

[0030] Example 2

[0031] Adding quicklime with larger particles to cement forms a bulky cohesive structure during hydration, which acts as a bridge and temporary plug to prevent the loss of injected mortar; adding plant fiber particles to cement acts to seal large pores.

[0032] The particle size of granular plugging agents significantly influences their water plugging effectiveness. Too large prevents the particles from penetrating the reservoir, while too small prevents them from achieving a plugging effect. Field and laboratory tests have shown that a particle size of 1 / 3 to 1 / 9 of the diameter produces excellent plugging effectiveness. Therefore, a 30-50μm G-grade oil well cement base is selected, along with 28-170μm quicklime and a portion of 56-350μm plant fiber particles to plug large pores.

[0033] Example 3

[0034] like Figure 1 As shown, the oil pipe 2 is lowered into the casing 1, and a high-temperature resistant plugging and sealing agent is configured. The high-temperature resistant plugging and sealing agent consists of a plugging agent 5 and a high-temperature resistant sealing agent 7. During construction, the plugging agent 5 is first pumped from the oil pipe 2 into the high-permeability oil-loss layer 4 using a pump truck, and then pumped into place with clean water 6. Then, the high-temperature resistant sealing agent 7 is pumped from the oil pipe 2 into the low-permeability oil layer 3 and the high-permeability oil layer 4 using a pump truck, and the plugging slurry is replaced into place with clean water 6.

[0035] Example 4

[0036] (1) Connect the surface pipeline, test the oil and casing pressure to 20MPa, and ensure that there is no puncture and no leakage;

[0037] (2) Preparation of plugging agent: First, mix clean water and oil well G grade cement into cement slurry with a water-cement ratio of 1:1.25 and a density of 1.65g / cm 3 ~1.75g / cm 3 Then add 0.5% to 1.5% of coagulant and 1% to 1.5% of fluid loss agent, and then add quicklime and plant fiber particles into the slurry, and control the density at 1.75g / cm 3 ~1.85g / cm 3 , to ensure good pumpability;

[0038] (3) Preparation of high temperature resistant sealant: first add 1% sodium sulfate accelerator to phenolic resin and stir evenly, then add 0.5% hydrochloric acid curing agent and mix evenly to form high temperature resistant sealant;

[0039] (4) Use the prepared plugging agent to pre-plug the leaking formation;

[0040] (5) After the pre-plugging is successful, fill the casing: pump dirty water or clean water from the oil pipe until the casing returns to liquid;

[0041] (6) When the high-temperature resistant sealing agent is squeezed in until the squeezing pressure increases, the final squeezing amount is determined based on the pressure increase rate and the designed squeezing amount of the plugging agent;

[0042] (7) Use clean water to push up to 0.5m above the preset plugging height 3 When the casing is reversed, water is removed and the time from the oil pipe to the casing reversed is controlled between 25 minutes and 40 minutes. It is neither too early nor too late to reverse. This step is not only to maintain construction safety, but more importantly, it can further enhance the curing strength of the plugging agent through secondary displacement, thereby improving the plugging effect.

[0043] (8) Once the pressure reaches 20 MPa or above during the displacement process, if the plugging agent does not displace the oil pipe at this time, backwashing should be carried out immediately until clear water is seen in the backwash. After clear water is seen, top flushing should be carried out immediately to gradually flush out the plugging agent that has not been completely solidified, and flush it to the reserved depth. After flushing until the return liquid sees clear water, 10 oil pipes are lifted (about 100m height), the wellhead is installed, and the pressure is re-inflated to 10 MPa. After the well is shut in and solidified for 24 hours, the pressure test is 15 MPa for 30 minutes. If △P ≤ 0.5 MPa, it is qualified;

[0044] (9) When it is necessary to measure the cementing quality, drill the plugging layer, test the pressure at 15 MPa for 30 minutes, and after passing the test with △P≤0.5 MPa, measure the cementing quality of the plugging section to verify whether the plugging meets the predetermined requirements.

[0045] In the existing field construction, G-grade cement with a specific gravity of 1.85 is usually used for plugging. Clean water is used to squeeze it into the oil layer at one time, and a cement plug of corresponding height is left in the wellbore. The well is shut down under pressure and waits for solidification.

[0046] The process of the present invention consists of two plugs. The first section is a plugging agent with a plugging and sealing effect, and the second section is a high-temperature resistant sealing agent with a plugging and sealing effect. The two plugs are squeezed in. At the same time, under the action of an admixture, the initial setting time of the plugging agent is adjusted. After the pressure diffuses, the lower pipe string is used for flushing to accurately control the ash surface height in the wellbore.

[0047] The above-described embodiments are only preferred embodiments of the present invention, and are not intended to be all feasible embodiments of the present invention. Any obvious modifications made by a person skilled in the art without departing from the principles and spirit of the present invention should be considered to be included within the scope of protection of the claims of the present invention.

Claims

1. A method for plugging a formation leaking oil well, characterized by: The oil pipe (2) is lowered into the casing (1), and a high-temperature resistant plugging and sealing agent is prepared. The high-temperature resistant plugging and sealing agent is composed of a plugging agent (5) and a high-temperature resistant sealing agent (7). During construction, the plugging agent (5) is first pumped from the oil pipe (2) into the high-permeability oil-loss layer (4) by a pump truck, and pumped into place with clean water (6). Then, the high-temperature resistant sealing agent (7) is pumped from the oil pipe (2) into the low-permeability oil layer (3) and the high-permeability oil-loss layer (4) by a pump truck, and the plugging slurry is replaced in place with clean water (6); The high-temperature resistant plugging and sealing agent consists of two segments. The first segment is a plugging agent, and the second segment is a high-temperature resistant sealing agent. The plugging agent is composed of G-grade oil well cement, quicklime and plant fiber particles. The plugging agent is made by mixing G-grade oil well cement, quicklime and plant fiber particles in a weight ratio of 7:1:

2. The plugging agent is prepared during on-site construction by first mixing clean water and oil well G-grade cement into a cement slurry with a water-cement ratio of 1:1.25 and a density of 1.65g / cm³~1.75g / cm³. Quicklime and plant fiber particles are then added to the cement slurry, and a setting accelerator with a mass fraction of 0.5% to 1.5% and a fluid loss reducer with a mass fraction of 1% to 1.5% are added; the setting accelerator is RK-51S oil well cement setting and early strength accelerating agent; the fluid loss reducer is SL-2 high temperature and salt resistant rate loss reducing agent; the high temperature resistant sealing agent is prepared by adding 1% by mass of 0.35 mol / L sodium sulfate accelerator and 0.5% by mass of 12 mol / L hydrochloric acid curing agent to the phenolic resin and mixing them evenly.

2. The method for plugging a formation leaking oil well according to claim 1, wherein: The density of the plugging agent is 1.75g / cm³~1.85g / cm³.

3. The method for plugging a formation leaking oil well according to claim 1, wherein: The high-temperature resistant sealing agent is prepared by adding an accelerator and a curing agent to a phenolic resin, and the curing time is controlled by the amount of the curing agent and the accelerator added.

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