Self-foaming low-density kill fluid

Abstract

This invention discloses a self-foaming low-density kill fluid, comprising the following components by weight: water: 50-80 parts, suspension stabilizer: 0.2-0.6 parts, pH adjuster: 0.5-1.0 parts, high-temperature stabilizer: 1.0-2.0 parts, wetting agent: 2.0-3.0 parts, self-foaming agent: 15-25 parts, foam binding agent: 5-10 parts, and low-density reducing agent: 10-40 parts. The low-density reducing agent in this kill fluid reduces the fluid's density; the foam binding agent further binds the nitrogen gas generated by the self-foaming agent at the base viscosity of the suspension stabilizer, stabilizing it in the liquid phase system. Furthermore, the product has low viscosity, is simple to operate on-site, requires no specialized foaming equipment, and has a minimum density of 0.4 g / cm³. 3 The permeability recovery rate reaches over 90%, which can meet the requirements for reservoir protection during well workover.

Description

Technical Field

[0001] This invention belongs to the field of downhole operation technology and relates to a self-foaming low-density well control fluid. Background Technology

[0002] In the later stages of oil exploration and development, well workover is crucial for resolving various downhole faults and restoring production. Well workover necessitates the use of kill fluid for circulation and well control to meet well control requirements. In older oilfields, the bottomhole pressure coefficient is extremely low, and using kill fluids such as water can create a significant pressure differential, leading to downhole leakage. Improper handling of leakage can easily result in blowouts and other serious incidents. Therefore, in older or low-pressure oil and gas fields, it is best to select a kill fluid with a density matching the formation pressure during well workover. Traditional methods for reducing kill fluid density include adding surfactants to form microbubbles or foams (as described in Chinese patents (publication number: CN103965844B, patent number ZL201510272342.3)), using oil-in-water or water-in-oil emulsions to reduce water density, and using hollow spheres such as polymer microspheres to reduce kill fluid density.

[0003] In addressing the technical challenges of low-density well control fluids, each of the aforementioned methods has its advantages and disadvantages. The method of forming foam using surfactants requires powerful equipment to generate foam, and the foam stability is relatively poor. Emulsions and hollow spheres offer limited density reduction, failing to meet the requirements for even lower density well control fluids. Therefore, it is necessary to further develop a low-density well control fluid that can effectively reduce density, is easy to apply, and is cost-effective. Summary of the Invention

[0004] The purpose of this invention is to provide a self-foaming, low-density kill fluid, the density of which can be adjusted within a range of 0.4-0.7 g / cm³. 3 It can achieve stable density and viscosity under high temperature and high pressure conditions to meet the purpose of preventing leakage and completing well control during well workover.

[0005] The technical solution adopted in this invention is a self-foaming low-density well control fluid, which, by mass, comprises the following components:

[0006] Water: 50-80 parts

[0007] Suspension stabilizer: 0.2-0.6 parts,

[0008] pH adjuster: 0.5-1.0 parts,

[0009] High-temperature stabilizer: 1.0-2.0 parts,

[0010] Wetting agent: 2.0-3.0 parts,

[0011] Self-foaming agent: 15-25 parts,

[0012] Foam binding agent: 5-10 parts,

[0013] Low-density lightening agent: 10-40 parts;

[0014] The invention is further characterized in that,

[0015] The suspension stabilizer is a compound of xanthan gum, von Willebrand gum, and guar gum; more preferably, it is a compound of 30-50 parts xanthan gum, 30-40 parts guar gum, and 10-40 parts von Willebrand gum. The compound of xanthan gum, von Willebrand gum, and guar gum produces a good synergistic effect, improving suspension capacity, and also improves temperature resistance, demonstrating suspension stability under high temperature conditions.

[0016] The preferred pH adjusters are sodium carbonate and sodium hydroxide, which can be used alone or in combination.

[0017] The preferred high-temperature stabilizers are sodium sulfite and thiourea, which can be used alone or in combination.

[0018] The further wetting agent is a compound of octylphenol polyoxyethylene ether, polyether-modified silicone oil, and fatty alcohol ether phosphate ester; preferably, it is a compound of 30-50 parts octylphenol polyoxyethylene ether, 20-40 parts polyether-modified silicone oil, and 10-30 parts fatty alcohol ether phosphate ester. The wetting agent can improve the hydrophilic properties of the low-density weight-reducing agent, enabling it to disperse well in water, increasing the solid content of the low-density weight-reducing agent in water, and thus allowing for an even lower density reduction.

[0019] The preferred low-density light-reducing agent is polymer expandable microspheres with a hollow internal structure, a density of 45-70 kg / m³, a median particle size of 45-85 μm, and a glass transition temperature ≥100℃.

[0020] The self-foaming agent is azobisisobutyronitrile (AIBN). AIBN decomposes at a certain temperature to generate nitrogen gas, which reduces the density of the liquid phase system, thus achieving a reduction in density.

[0021] The foam binding agent is further formulated from octadecyl dimethylamine oxide, isomeric alcohol ethers, and fatty alcohols; preferably, it is formulated from 30-60 parts of octadecyl dimethylamine oxide, 30-50 parts of isomeric alcohol ethers, and 10-20 parts of fatty alcohols. The foam binding agent can further bind the nitrogen gas generated by the self-foaming agent under the condition of the basic viscosity of the suspension stabilizer, thus stabilizing it in the liquid phase system.

[0022] The key technological innovation of this application lies in,

[0023] Low-density reducers can lower the density of kill fluid, but only to a limited extent, so self-foaming agents are used. Self-foaming agents decompose into gas at a certain temperature, thus reducing density.

[0024] Foam binding agents can further bind the nitrogen gas generated by self-foaming agents under the condition of the basic viscosity of the suspension stabilizer, thus stabilizing it in the liquid phase system.

[0025] Wetting agents can improve the hydrophilic properties of low-density weight-reducing agents, enabling them to disperse well in water, increasing the solid content of low-density weight-reducing agents in water, and thus reducing the density even further.

[0026] The beneficial effects of this invention are:

[0027] 1. The present invention provides a low-density well control fluid for well workover in low-pressure oil and gas fields, with a density as low as 0.4 g / cm³. 3 The density range is adjustable;

[0028] 2. The low-density well control fluid of the present invention for well workover in low-pressure oil and gas fields has a low viscosity, is simple to operate on site, and does not require special foaming equipment.

[0029] 3. The low-density kill fluid of the present invention for well workover in low-pressure oil and gas fields has good reservoir protection effect and a permeability recovery rate of over 90%, which can meet the reservoir protection requirements during well workover.

[0030] 4. The temperature range of the low-density well control fluid for well workover in low-pressure oil and gas fields according to the present invention is 60-140℃. Detailed Implementation

[0031] The following detailed description is based on the embodiments of the present invention. These embodiments are implemented under the premise of the technical solution of the present invention, and provide detailed implementation methods and specific operation processes. However, the scope of protection of the present invention is not limited to the following embodiments.

[0032] Example 1:

[0033] A self-foaming, low-density well control fluid for well workover in low-pressure oil and gas fields:

[0034] Water: 70 parts

[0035] Suspension stabilizer: 0.2 parts

[0036] pH adjuster: 1.0 part

[0037] High temperature stabilizer: 2.0 parts

[0038] Wetting agent: 2.0 parts

[0039] Self-foaming agent: 25 parts

[0040] Foam binding agent: 10 parts

[0041] Low-density lightening agent: 10 parts

[0042] The suspension stabilizer is composed of 30 parts xanthan gum, 40 parts vellum gum, and 30 parts guar gum by weight. The combination of xanthan gum, vellum gum, and guar gum will produce a good synergistic effect, improve the suspension capacity, and improve the temperature resistance, thus demonstrating the suspension stability under high temperature conditions.

[0043] The pH adjuster mentioned is sodium carbonate or sodium hydroxide, which can be used alone or in combination.

[0044] The high-temperature stabilizers mentioned are sodium sulfite and thiourea, which can be used alone or in combination.

[0045] The wetting agent is composed of 30 parts by weight of octylphenol polyoxyethylene ether, 40 parts of polyether-modified silicone oil, and 30 parts of fatty alcohol ether phosphate ester. The wetting agent can improve the hydrophilic properties of the low-density light-reducing agent, enabling it to disperse well in water, increasing the solid content of the low-density light-reducing agent in water, and thus reducing the density even further.

[0046] The low-density light-reducing agent is a polymer expandable microsphere with a hollow internal structure, a density of 45-70 kg / m³, a median particle size of 45-85 μm, and a glass transition temperature ≥100℃.

[0047] The self-foaming agent is azobisisobutyronitrile (AIBN). AIBN decomposes at a certain temperature to generate nitrogen gas, which reduces the density of the liquid system, thus achieving a reduction in density.

[0048] The foam binding agent is a compound of octadecyl dimethylamine oxide, isomeric alcohol ether, and fatty alcohol; preferably, it is a compound of 30-60 parts octadecyl dimethylamine oxide, 30-50 parts isomeric alcohol ether, and 10-20 parts fatty alcohol. The foam binding agent can further bind the nitrogen gas generated by the self-foaming agent under the condition of the basic viscosity of the suspension stabilizer, thus stabilizing it in the liquid phase system.

[0049] Example 2:

[0050] A self-foaming, low-density well control fluid for well workover in low-pressure oil and gas fields:

[0051] Water: 50 parts

[0052] Suspension stabilizer: 0.2 parts

[0053] pH adjuster: 0.5 parts

[0054] High temperature stabilizer: 1.0 part

[0055] Wetting agent: 3.0 parts

[0056] Self-foaming agent: 15 parts

[0057] Foam binding agent: 5 parts

[0058] Low-density lightening agent: 40 parts

[0059] The suspension stabilizer is composed of 40 parts xanthan gum, 20 parts wenlun gum, and 40 parts guar gum by weight. The combination of xanthan gum, wenlun gum, and guar gum will produce a good synergistic effect, improving the suspension capacity, and will also improve the temperature resistance, demonstrating the suspension stability under high temperature conditions.

[0060] The pH adjuster mentioned is sodium carbonate or sodium hydroxide, which can be used alone or in combination.

[0061] The high-temperature stabilizers mentioned are sodium sulfite and thiourea, which can be used alone or in combination.

[0062] The wetting agent is composed of 50 parts by weight of octylphenol polyoxyethylene ether, 20 parts of polyether-modified silicone oil, and 30 parts of fatty alcohol ether phosphate ester. The wetting agent enhances the hydrophilic properties of the low-density weight-reducing agent, enabling it to disperse well in water, increasing the solid content of the low-density weight-reducing agent in water, and thus achieving an even lower density reduction.

[0063] The low-density light-reducing agent is a polymer expandable microsphere with a hollow internal structure, a density of 45-70 kg / m³, a median particle size of 45-85 μm, and a glass transition temperature ≥100℃.

[0064] The self-foaming agent is azobisisobutyronitrile (AIBN). AIBN decomposes at a certain temperature to generate nitrogen gas, which reduces the density of the liquid system, thus achieving a reduction in density.

[0065] The foam binding agent is a compound of octadecyl dimethylamine oxide, isomeric alcohol ether, and fatty alcohol; preferably, it is a compound of 30-60 parts octadecyl dimethylamine oxide, 30-50 parts isomeric alcohol ether, and 10-20 parts fatty alcohol. The foam binding agent can further bind the nitrogen gas generated by the self-foaming agent under the condition of the basic viscosity of the suspension stabilizer, thus stabilizing it in the liquid phase system.

[0066] Example 3:

[0067] A self-foaming, low-density well control fluid for well workover in low-pressure oil and gas fields:

[0068] Water: 80 parts

[0069] Suspension stabilizer: 0.5 parts

[0070] pH adjuster: 0.8 parts

[0071] High temperature stabilizer: 1.5 parts

[0072] Wetting agent: 2.4 parts

[0073] Self-foaming agent: 20 parts

[0074] Foam binding agent: 8 parts

[0075] Low-density lightening agent: 30 parts

[0076] The suspension stabilizer is composed of 50 parts xanthan gum, 10 parts von Willebrand gum, and 40 parts guar gum by weight. This combination of xanthan gum, von Willebrand gum, and guar gum produces a good synergistic effect, improving suspension capacity, and also enhances temperature resistance, demonstrating suspension stability under high-temperature conditions.

[0077] The pH adjuster mentioned is sodium carbonate or sodium hydroxide, which can be used alone or in combination.

[0078] The high-temperature stabilizers mentioned are sodium sulfite and thiourea, which can be used alone or in combination.

[0079] The wetting agent is composed of 50 parts by weight of octylphenol polyoxyethylene ether, 40 parts of polyether-modified silicone oil, and 10 parts of fatty alcohol ether phosphate ester. The wetting agent enhances the hydrophilic properties of the low-density weight-reducing agent, enabling it to disperse well in water, increasing the solid content of the low-density weight-reducing agent in water, and thus allowing for even further density reduction.

[0080] The low-density light-reducing agent is a polymer expandable microsphere with a hollow internal structure, a density of 45-70 kg / m³, a median particle size of 45-85 μm, and a glass transition temperature ≥100℃.

[0081] The self-foaming agent is azobisisobutyronitrile (AIBN). AIBN decomposes at a certain temperature to generate nitrogen gas, which reduces the density of the liquid system, thus achieving a reduction in density.

[0082] The foam binding agent is a compound of octadecyl dimethylamine oxide, isomeric alcohol ether, and fatty alcohol; preferably, it is a compound of 30-60 parts octadecyl dimethylamine oxide, 30-50 parts isomeric alcohol ether, and 10-20 parts fatty alcohol. The foam binding agent can further bind the nitrogen gas generated by the self-foaming agent under the condition of the basic viscosity of the suspension stabilizer, thus stabilizing it in the liquid phase system.

[0083] Example 4:

[0084] A self-foaming, low-density well control fluid for well workover in low-pressure oil and gas fields:

[0085] Water: 60 parts

[0086] Suspension stabilizer: 0.4 parts

[0087] pH adjuster: 1.0 part

[0088] High temperature stabilizer: 1.6 parts

[0089] Wetting agent: 3.0 parts

[0090] Self-foaming agent: 15 parts

[0091] Foam binding agent: 10 parts

[0092] Low-density lightening agent: 20 parts

[0093] The suspension stabilizer is composed of 40 parts xanthan gum, 30 parts wenlun gum, and 30 parts guar gum by weight. The combination of xanthan gum, wenlun gum, and guar gum will produce a good synergistic effect, improve the suspension capacity, and improve the temperature resistance, thus demonstrating the suspension stability under high temperature conditions.

[0094] The pH adjuster mentioned is sodium carbonate or sodium hydroxide, which can be used alone or in combination.

[0095] The high-temperature stabilizers mentioned are sodium sulfite and thiourea, which can be used alone or in combination.

[0096] The wetting agent is composed of 40 parts by weight of octylphenol polyoxyethylene ether, 40 parts of polyether-modified silicone oil, and 20 parts of fatty alcohol ether phosphate ester. The wetting agent can improve the hydrophilic properties of the low-density light-reducing agent, enabling it to disperse well in water, increasing the solid content of the low-density light-reducing agent in water, and thus reducing the density even further.

[0097] The low-density light-reducing agent is a polymer expandable microsphere with a hollow internal structure, a density of 45-70 kg / m³, a median particle size of 45-85 μm, and a glass transition temperature ≥100℃.

[0098] The self-foaming agent is azobisisobutyronitrile (AIBN). AIBN decomposes at a certain temperature to generate nitrogen gas, which reduces the density of the liquid system, thus achieving a reduction in density.

[0099] The foam binding agent is a compound of octadecyl dimethylamine oxide, isomeric alcohol ether, and fatty alcohol; preferably, it is a compound of 30-60 parts octadecyl dimethylamine oxide, 30-50 parts isomeric alcohol ether, and 10-20 parts fatty alcohol. The foam binding agent can further bind the nitrogen gas generated by the self-foaming agent under the condition of the basic viscosity of the suspension stabilizer, thus stabilizing it in the liquid phase system.

[0100] The basic performance of the above embodiments was evaluated.

[0101] Table 1. Basic Properties of Self-foaming Low-Density Well-Killing Fluid

[0102] Kill fluid <![CDATA[Density (g / cm 3 )]]> Apparent viscosity (mPa·s) <![CDATA[Φ 3 ]]> Permeability recovery rate (%) Example 1 0.4 146 28 87.5 Example 2 0.5 125 24 85.7 Example 3 0.6 103 20 90.8 Example 4 0.7 91 15 92.3

[0103] The evaluation results show that the four embodiments of the low-density well-killing fluid of this invention have good rheological properties, are pumpable, have good inhibition performance, good reservoir protection effect, and a permeability recovery rate of over 85%; among them, Φ 3 It is the reading of the liquid at 300 r / min in a six-speed rotary viscometer, i.e., the viscosity value.

[0104] The high-temperature performance of the above embodiments was further evaluated to determine their high-temperature stability.

[0105] The foregoing describes the basic principles, main features, and advantages of this invention. Those skilled in the art should understand that this invention is not limited to the above embodiments. The embodiments described above are merely the principles of this invention. Various changes and modifications can be made to this invention without departing from its spirit and scope, and all such changes and modifications will fall within the scope of this invention as claimed.

Claims

1. A self-foaming low-density kill fluid, characterized in that, The kill fluid comprises the following components by weight: Water: 50-80 parts Suspension stabilizer: 0.2-0.6 parts, pH adjuster: 0.5-1.0 parts, High-temperature stabilizer: 1.0-2.0 parts, Wetting agent: 2.0-3.0 parts, Self-foaming agent: 15-25 parts, Foam binding agent: 5-10 parts, Low-density lightening agent: 10-40 parts; The suspension stabilizer is composed of 30-50 parts xanthan gum, 30-40 parts guar gum, and 10-40 parts wenlun gum by weight. The low-density light-reducing agent is a polymer expandable microsphere with a hollow internal structure and a density of 45-70 kg / m³. 3 The median particle size is 45-85 μm, and the glass transition temperature is ≥100℃; The self-foaming agent is azobisisobutyronitrile.

2. The self-foaming low-density kill fluid according to claim 1, characterized in that, The pH adjuster is one or both of sodium carbonate and sodium hydroxide.

3. The self-foaming low-density kill fluid according to claim 1, characterized in that, The high-temperature stabilizer is one or both of sodium sulfite and thiourea.

4. The self-foaming low-density kill fluid according to claim 1, characterized in that, The wetting agent is composed of 30-50 parts by weight of octylphenol polyoxyethylene ether, 20-40 parts of polyether-modified silicone oil, and 10-30 parts of fatty alcohol ether phosphate ester.