Carbon dioxide drive well killing operation rubber plug temporary plugging agent and preparation method thereof

Abstract

This disclosure relates to a temporary plugging agent for carbon dioxide-driven well control operations and its preparation method. The temporary plugging agent comprises, by mass percentage: 5%–10% temporary plugging agent, 0.1%–0.5% gelling stabilizer, 0.5%–1.0% gelling crosslinking agent, 0.2%–0.4% gelling initiator, 0.1%–0.2% gel breaker, and the balance being water. The temporary plugging agent is simple to prepare, has low initial viscosity, low cost, and high gel strength. The gelation time at 108℃ is controllable at 6–8 hours, and the stability time after gelation is 3–10 days. It exhibits good gel stability and low viscosity after degradation, minimizing formation damage. This meets the requirements for solids-free well control operations in oil and water wells in the carbon dioxide test area at 108℃, achieving safe, environmentally friendly, and low-cost operation of injection and production wells.

Description

Technical Field

[0001] This disclosure relates to the field of tertiary oil recovery engineering technology, specifically to a temporary plugging agent for carbon dioxide displacement well operations and its preparation method. Background Technology

[0002] The statements in this section provide only background information in connection with this disclosure and do not constitute prior art.

[0003] Carbon dioxide flooding has become an effective way to improve development and increase recovery rates in ultra-low permeability reservoirs. However, carbon dioxide flooding requires high injection and production pressures, and the kill fluid density required during operation is also high. Carbon dioxide gas can damage the properties of the kill fluid, making kill operations difficult. Solid-phase kill fluids severely pollute the ultra-low permeability reservoirs in the carbon dioxide test area, making them unsuitable for field application. Therefore, a temporary plugging agent was used to seal the formation, and after balancing the formation pressure, conventional operations could begin. The agent could self-destruct after the operation, leaving no contamination to the reservoir.

[0004] Due to the limitations of the low-permeability or ultra-low-permeability reservoirs and poor fluid absorption capacity in the carbon dioxide test area, a temporary plugging agent with low initial viscosity and a gelation time of 6-8 hours is required. Furthermore, due to the depth of the well in the carbon dioxide test area and the underground temperature reaching 108℃, the agent needs to be gelled and stabilized at 108℃ for 3-10 days.

[0005] The invention patent with publication number CN116948082B provides a liquid plugging agent with controllable gelation rate and its synthesis method. The gelation time of the liquid plugging agent is between 62-260 min. For low-permeability or ultra-low-permeability reservoirs in carbon dioxide flooding, a gelation time of 260 min is insufficient to inject a sufficient amount of plugging agent into the formation and complete the subsequent replacement process. In addition, hollow ceramic microspheres are first added to the liquid plugging agent. The carbon dioxide test area is a low-permeability or ultra-low-permeability reservoir with a permeability of only 1% or even 0.1%, so hollow ceramic microspheres cannot be injected. Moreover, the maximum operating temperature of the liquid plugging agent is only 85-90℃.

[0006] The invention patent with publication number CN104531115B provides a temporary plugging agent for water control in horizontal wells. The gelation time of the temporary plugging agent is between 1 and 3 hours. For low-permeability or ultra-low-permeability reservoirs flooded by carbon dioxide, a gelation time of 3 hours is insufficient to inject a sufficient amount of temporary plugging agent into the formation and complete the subsequent replacement process. In addition, the experimental temperature of the temporary plugging agent is only 60°C.

[0007] It should be noted that the information disclosed in the background section above is only used to enhance the understanding of the background of this disclosure, and therefore may include information that does not constitute prior art. Summary of the Invention

[0008] In view of this, this disclosure provides a temporary plugging agent for carbon dioxide flooding well control operations and its preparation method, which solves the problem that conventional temporary plugging agents cannot meet the requirements of low initial viscosity, gelation time of 6-8 hours, and gelation stability of 3-10 days at 108℃ for low-permeability or ultra-low-permeability reservoirs in carbon dioxide flooding.

[0009] To achieve the above-mentioned objective, in a first aspect, the temporary plugging agent for carbon dioxide displacement well operations comprises, by mass percentage:

[0010] The composition includes 5%–10% temporary plugging agent, 0.1%–0.5% gelling stabilizer, 0.5%–1.0% gelling crosslinking agent, 0.2%–0.4% gelling initiator, 0.1%–0.2% gelling agent, and the remainder is water.

[0011] In this disclosure and possible embodiments, the temporary plugging agent is acrylamide, the gelling stabilizer is organobentonite, the gelling crosslinking agent is ethylene glycol dimethacrylate and / or methylenebisacrylamide, the gelling initiator is ammonium persulfate, and the gelling agent is sodium carbonate or sodium bicarbonate.

[0012] In this disclosure and possible embodiments, the acrylamide is 7% to 10%, the organobentonite is 0.2%, the ethylene glycol dimethacrylate is 0.5% to 0.7%, the ammonium persulfate is 0.1% to 0.4%, and the sodium carbonate is 0.1%.

[0013] In this disclosure and possible embodiments, the acrylamide is 7%, the organobentonite is 0.2%, the ethylene glycol dimethacrylate is 0.5%, the ammonium persulfate is 0.15%, and the sodium carbonate is 0.1%.

[0014] In this disclosure and possible embodiments, the acrylamide is 10%, the organobentonite is 0.2%, the ethylene glycol dimethacrylate is 0.7%, the ammonium persulfate is 0.2%, and the sodium bicarbonate is 0.1%.

[0015] In this disclosure and possible embodiments, the acrylamide is 10%, organobentonite is 0.2%, ethylene glycol dimethacrylate is 0.7%, methylenebisacrylamide is 0.1%, ammonium persulfate is 0.2%, and sodium bicarbonate is 0.1%.

[0016] In this disclosure and possible embodiments, the acrylamide is 10%, the organobentonite is 0.2%, the ethylene glycol dimethacrylate is 0.7%, the ammonium persulfate is 0.2%, and the sodium bicarbonate is 0.1%.

[0017] In this disclosure and possible embodiments, the acrylamide is 7%, the organobentonite is 0.2%, the ethylene glycol dimethacrylate is 0.5%, the ammonium persulfate is 0.15%, and the sodium carbonate is 0.1%.

[0018] Secondly, the method for preparing the temporary plugging agent for carbon dioxide displacement well operations as described in any one of the first aspects includes:

[0019] The temporary plugging agent, gelling stabilizer, gelling crosslinking agent, gelling initiator and breaker are added to water according to the mass percentage, and stirred until all components are dissolved to obtain the temporary plugging agent.

[0020] In this disclosure and possible embodiments, the stirring time is 5-30 minutes.

[0021] The beneficial effects of this invention are as follows:

[0022] The temporary plugging agent for carbon dioxide-driven well control operations of the present invention is simple to prepare, has low initial viscosity, low cost, and high gel strength. The gelation time is controllable at 108℃ for 6-8 hours, and the stability time after gelation is 3-10 days. It has good gel stability and low viscosity after degradation, which causes little damage to the formation. It meets the solids-free well control operation requirements of oil and water wells in the carbon dioxide test area at 108℃, and realizes safe, environmentally friendly, and low-cost operation of injection and production wells. Detailed Implementation

[0023] The present disclosure is described below based on embodiments; however, it is worth noting that the present disclosure is not limited to these embodiments. In the detailed description of the present disclosure below, 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.

[0024] 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."

[0025] The temporary plugging agent for carbon dioxide displacement well operations disclosed herein comprises, by weight percentage:

[0026] The composition includes 5%–10% temporary plugging agent, 0.1%–0.5% gelling stabilizer, 0.5%–1.0% gelling crosslinking agent, 0.2%–0.4% gelling initiator, 0.1%–0.2% gelling agent, and the remainder is water.

[0027] In one specific embodiment, the temporary plugging agent is acrylamide, the gelling stabilizer is organobentonite, the gelling crosslinking agent is ethylene glycol dimethacrylate and / or methylenebisacrylamide, the gelling initiator is ammonium persulfate, and the gelling agent is sodium carbonate or sodium bicarbonate.

[0028] In one specific embodiment, the acrylamide is 7%–10%, the organobentonite is 0.2%, the ethylene glycol dimethacrylate is 0.5%–0.7%, the ammonium persulfate is 0.1%–0.4%, and the sodium carbonate is 0.1%.

[0029] The method for preparing the temporary plugging agent for carbon dioxide displacement well operations disclosed herein includes:

[0030] The temporary plugging agent, gelling stabilizer, gelling crosslinking agent, gelling initiator and breaker are added to water according to the mass percentage, and stirred until all components are dissolved to obtain the temporary plugging agent.

[0031] In one specific embodiment, the stirring time is 5-30 minutes.

[0032] In this embodiment, the instrument used to test the viscosity of the temporary plugging agent is a Brookfield DV-III rotational viscometer with a No. 64 rotor and a shear rate of 7.34 s⁻¹. -1 Taking tap water as an example, the gel viscosity of the temporary plugging agent used in carbon dioxide flooding solids-free well control operations is 4 × 10⁻⁶. 4 ~6×10 4 The solution has a stabilization time adjustable from 2 to 15 days, and its initial viscosity during preparation is low (less than 10 mPa·s), making it easy to inject and meeting the requirements of the construction process.

[0033] The following are preferred embodiments of this disclosure.

[0034] Example 1

[0035] The temporary plugging agent for rubber stoppers in Example 1 has the following composition by mass percentage:

[0036] Acrylamide 7%, organobentonite 0.2%, ethylene glycol dimethacrylate 0.5%, ammonium persulfate 0.15%, sodium carbonate 0.1%, balance is water.

[0037] The above components were added to a stoppered wide-mouth bottle in proportion and stirred for 10 minutes to completely disperse and dissolve them, thus obtaining a temporary plugging agent for CO2 well control operations.

[0038] Example 2

[0039] The temporary plugging agent for rubber stoppers in Example 2 has the following composition by mass percentage:

[0040] Acrylamide 10%, organobentonite 0.2%, ethylene glycol dimethacrylate 0.7%, ammonium persulfate 0.2%, sodium bicarbonate 0.1%, balance: water.

[0041] The specific preparation method is the same as in Example 1.

[0042] Example 3

[0043] The temporary plugging agent for rubber stoppers in Example 3 has the following composition by mass percentage:

[0044] Acrylamide 10%, organobentonite 0.2%, ethylene glycol dimethacrylate 0.7%, methylenebisacrylamide 0.1%, ammonium persulfate 0.2%, sodium bicarbonate 0.1%, and the balance is water.

[0045] The specific preparation method is the same as in Example 1.

[0046] Determination of gelation time and post-gelation stability time of the temporary plugging agents in Examples 1-3:

[0047] In the laboratory, samples from Examples 1-3 were placed in stoppered wide-mouth bottles, and the gelation process was observed in a 108°C constant temperature oven. The experimental results showed that gelation occurred after 6 hours, and the measured gel viscosity was 4.5 × 10⁻⁶. 4 mPa·s, the results are shown in Table 1.

[0048] Table 1. Gelation time, gelation and breakage viscosity, and post-gelation stabilization time of the temporary plugging agents in Examples 1-3.

[0049]

[0050] Determination of core damage caused by temporary plugging agent in Example 2:

[0051] The temporary plugging agent of Example 2 was injected into a low-permeability core and placed in a constant temperature oven at 108℃ for 6 hours to form a gel. After 6 days of experimentation, CO2 was injected to conduct a displacement experiment to examine the damage to the core after the temporary plugging agent broke the gel. The degree of core damage was less than 5%, and the results are shown in Table 2.

[0052] Table 2 Core damage rate after temporary plugging agent rupture

[0053]

[0054]

[0055] Example 4

[0056] The temporary plugging agent for rubber stoppers in Example 4 has the following composition by mass percentage:

[0057] Acrylamide 10%, organobentonite 0.2%, ethylene glycol dimethacrylate 0.7%, ammonium persulfate 0.2%, sodium bicarbonate 0.1%, balance is water.

[0058] The preparation method is the same as in Example 1.

[0059] This embodiment uses the carbon dioxide-driven well control fluid gas invasion simulation evaluation experimental device provided by patent number 201520963292.9 to conduct a simulated gas invasion evaluation test. The test results show that the pressure balance stability time for a single well control operation is 8 hours, and no gas invasion phenomenon was observed.

[0060] Example 5

[0061] The temporary plugging agent for rubber stoppers in Example 5 has the following composition by mass percentage:

[0062] Acrylamide 7%, organobentonite 0.2%, ethylene glycol dimethacrylate 0.5%, ammonium persulfate 0.15%, sodium carbonate 0.1%, balance is water.

[0063] The preparation method of this embodiment 5 is as follows: according to the above composition and mass percentage, the above components are prepared on site using a liquid mixing device, and stirred for 30 minutes to completely disperse and dissolve them, so as to obtain a temporary plugging agent for CO2 displacement well operation.

[0064] The temporary plugging agent described in Example 5 was applied in a field test well (Well S61-57) in a high-pressure oil production area. The well's formation depth was 2019.1m, and the wellhead pressure before the operation was 7MPa. The purpose of the operation was pump inspection, with an estimated operation period of 5 days and a designed gel stabilization time of 7 days for the temporary plugging agent. During the operation, there was no overflow or gas leakage, and the bottom hole pressure stabilized within 10 hours, demonstrating resistance to gas intrusion. Furthermore, after the treatment, well flushing replaced the degraded temporary plugging agent, and production returned to pre-operation levels.

[0065] The various embodiments of this disclosure have been described above. These descriptions are exemplary and not exhaustive, and are not limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments. The terminology used herein is chosen to best explain the principles, practical applications, or technical improvements to the technology in the market, or to enable others skilled in the art to understand the embodiments disclosed herein.

Claims

1. A temporary plugging agent for carbon dioxide displacement well operations, characterized in that, Its composition, by weight percentage, includes: The composition includes 5%–10% temporary plugging agent, 0.1%–0.5% gelling stabilizer, 0.5%–1.0% gelling crosslinking agent, 0.2%–0.4% gelling initiator, 0.1%–0.2% gelling agent, and the remainder is water.

2. The temporary plugging agent for carbon dioxide displacement well operations according to claim 1, characterized in that: The temporary plugging agent is acrylamide, the gelling stabilizer is organobentonite, the gelling crosslinking agent is ethylene glycol dimethacrylate and / or methylenebisacrylamide, the gelling initiator is ammonium persulfate, and the gelling agent is sodium carbonate or sodium bicarbonate.

3. The temporary plugging agent for carbon dioxide displacement well operations according to claim 2, characterized in that: The acrylamide is 7%–10%, the organobentonite is 0.2%, the ethylene glycol dimethacrylate is 0.5%–0.7%, the ammonium persulfate is 0.1%–0.4%, and the sodium carbonate is 0.1%.

4. The temporary plugging agent for carbon dioxide displacement well operations according to claim 3, characterized in that: The acrylamide is 7%, the organobentonite is 0.2%, the ethylene glycol dimethacrylate is 0.5%, the ammonium persulfate is 0.15%, and the sodium carbonate is 0.1%.

5. The temporary plugging agent for carbon dioxide displacement well operations according to claim 3, characterized in that: The acrylamide is 10%, the organobentonite is 0.2%, the ethylene glycol dimethacrylate is 0.7%, the ammonium persulfate is 0.2%, and the sodium bicarbonate is 0.1%.

6. The temporary plugging agent for carbon dioxide displacement well operations according to claim 3, characterized in that: The composition includes 10% acrylamide, 0.2% organobentonite, 0.7% ethylene glycol dimethacrylate, 0.1% methylenebisacrylamide, 0.2% ammonium persulfate, and 0.1% sodium bicarbonate.

7. The temporary plugging agent for carbon dioxide displacement well operations according to claim 3, characterized in that: The acrylamide is 10%, the organobentonite is 0.2%, the ethylene glycol dimethacrylate is 0.7%, the ammonium persulfate is 0.2%, and the sodium bicarbonate is 0.1%.

8. The temporary plugging agent for carbon dioxide displacement well operations according to claim 3, characterized in that: The acrylamide is 7%, the organobentonite is 0.2%, the ethylene glycol dimethacrylate is 0.5%, the ammonium persulfate is 0.15%, and the sodium carbonate is 0.1%.

9. A method for preparing the temporary plugging agent for carbon dioxide displacement well operations according to any one of claims 1-8, characterized in that, include: The temporary plugging agent, gelling stabilizer, gelling crosslinking agent, gelling initiator and breaker are added to water according to the mass percentage, and stirred until all components are dissolved to obtain the temporary plugging agent.

10. The method for preparing the temporary plugging agent for carbon dioxide displacement well operations according to claim 9, characterized in that: The stirring time is 5-15 minutes.

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