Self-foaming low-density well killing fluid

Abstract

The self-foaming low-density well killing fluid is prepared from the following components in parts by mass: 50 to 80 parts of water, 0.2 to 0.6 part of a suspension stabilizer, 0.5 to 1.0 part of a pH (Potential of Hydrogen) regulator, 1.0 to 2.0 parts of a high-temperature stabilizer, 2.0 to 3.0 parts of a wetting agent, 15 to 25 parts of a self-foaming agent, 5 to 10 parts of a foam binding agent and 10 to 40 parts of a low-density lightening agent. The low-density lightening agent in the well killing fluid can reduce the density of the well killing fluid; the foam binding agent can further bind nitrogen generated by the foaming agent under the condition of the basic viscosity of the suspension stabilizer, so that the nitrogen is stabilized in a liquid phase system. And the product has the advantages of low viscosity, simple field operation, no need of special foaming equipment, lowest density of 0.4 g / cm < 3 > and permeability recovery rate of more than 90%, and can meet the requirements of reservoir protection during well repair.

Description

Technical Field

[0001] The invention belongs to the technical field of downhole operations and relates to a self-foaming low-density well-killing fluid. Background Art

[0002] After oil exploration and development enters the middle and late stages of production, well repair is used to solve various downhole faults and resume production. Well repair must use well killing fluid for circulating well killing to meet well control requirements. When old oil fields enter the middle and late stages of production, the bottom hole pressure coefficient is extremely low. The use of well killing fluids such as clean water will cause a huge liquid column pressure difference, resulting in downhole leakage. After leakage occurs, if improper measures are taken, it is very easy to cause malignant events such as blowouts. Therefore, in the well repair process of old oil and gas fields or low-pressure oil and gas fields, it is best to use well killing fluids with a density that matches the formation pressure. Traditional methods for reducing the density of well killing fluids include adding surfactants to form microbubbles or foams, such as Chinese patents (Announcement No.: CN103965844B, Patent No. ZL201510272342.3), and also reducing the density of water in the form of oil-in-water or water-in-oil emulsions, and even using hollow balls such as polymer microspheres to reduce the density of well killing fluids.

[0003] In the technical difficulties encountered in low-density well-killing fluid, the above-mentioned methods all have advantages and disadvantages. The method of forming foam with surfactants requires powerful equipment to produce foam and the foam stability is poor; while the density that can be reduced by emulsions and hollow balls is limited and cannot meet the requirements of lower density well-killing fluid. Therefore, it is necessary to further develop a low-density well-killing fluid that can effectively reduce density, is simple to construct, and has low cost. Summary of the invention

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

[0005] The technical solution adopted by the present invention is that the self-foaming low-density well killing fluid comprises the following components in parts by mass:

[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 lightener: 10-40 parts;

[0014] The present invention is also characterized in that:

[0015] The suspension stabilizer is a compound of xanthan gum, guar gum and 30-50 parts of xanthan gum, 30-40 parts of guar gum and 10-40 parts of guar gum. The compound of xanthan gum, guar gum and guar gum can produce a good synergistic effect and improve the suspension ability on the one hand, and improve the temperature resistance effect on the other hand, reflecting the suspension stability under high temperature conditions.

[0016] Further, the pH adjuster is preferably sodium carbonate or sodium hydroxide, which can be used alone or in combination.

[0017] Further, the high temperature stabilizer is preferably sodium sulfite or thiourea, which can be used alone or in combination.

[0018] The wetting agent is further compounded from octylphenol polyoxyethylene ether, polyether modified silicone oil, and fatty alcohol ether phosphate; preferably, 30-50 parts of octylphenol polyoxyethylene ether, 20-40 parts of polyether modified silicone oil, and 10-30 parts of fatty alcohol ether phosphate. The wetting agent can improve the hydrophilicity of the low-density reducing agent, so that it can be well dispersed in water, increase the solid content of the low-density reducing agent in water, and reduce the density even further.

[0019] Further, the low-density reducing agent is preferably a polymer expanded microsphere, which has a hollow structure inside, a density of 45-70 Kg / m3, a median particle size of 45-85 um, and a glass transition temperature ≥100°C.

[0020] Furthermore, the self-foaming agent is azobisisobutyronitrile, which decomposes at a certain temperature to generate nitrogen. The gas reduces the density of the liquid phase system, thereby reducing the density.

[0021] Furthermore, the foam binding agent is a compound of octadecyl dimethylamine oxide, isomeric alcohol ethers, and fatty alcohols; preferably, it is a compound of 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 generated by the self-foaming agent under the condition of the basic viscosity of the suspension stabilizer, so that it is stabilized in the liquid phase system.

[0022] The key technical innovation of this application is that

[0023] Low-density lighteners can reduce the density of well-killing fluid, but to a limited extent, so self-foaming agents are used. Self-foaming agents decompose into gas at a certain temperature, reducing the density.

[0024] The foam binding agent can further bind the nitrogen generated by the self-foaming agent under the condition of the basic viscosity of the suspension stabilizer, so as to stabilize it in the liquid phase system.

[0025] The wetting agent can improve the hydrophilicity of the low-density lightener, so that it can be well dispersed in water, increase the solid content of the low-density lightener in water, and reduce the density further.

[0026] The beneficial effects of the present invention are:

[0027] 1. The low-density well-killing fluid used for well repair in low-pressure oil and gas fields of the present invention has a minimum density of 0.4 g / cm 3 , density range is adjustable;

[0028] 2. The low-density well-killing fluid used for low-pressure oil and gas field well repair of the present invention has low viscosity, simple on-site operation, and does not require special foaming equipment.

[0029] 3. The low-density well-killing fluid used for well repair in low-pressure oil and gas fields of the present invention has good reservoir protection effect, and the permeability recovery rate reaches more than 90%, which can meet the requirements of reservoir protection during well repair;

[0030] 4. The applicable temperature range of the low-density well-killing fluid used for low-pressure oil and gas field well repair of the present invention is 60-140°C. DETAILED DESCRIPTION

[0031] The following is a detailed description in conjunction with an embodiment of the present invention. This embodiment is implemented on the premise of the technical solution of the present invention, and a detailed implementation method and a specific operation process are given, but the protection scope of the present invention is not limited to the following embodiments.

[0032] Embodiment 1:

[0033] A self-foaming low-density well-killing fluid for low-pressure oil and gas field well repair:

[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 binder: 10 parts

[0041] Low density lightener: 10 parts

[0042] Among them, the suspension stabilizer is a compound of 30 parts of xanthan gum, 40 parts of unlun gum and 30 parts of guar gum in parts by mass; the compound of xanthan gum, unlun gum and guar gum will produce a good synergistic effect and improve the suspension ability on the one hand, and on the other hand, it will improve the temperature resistance effect and reflect the suspension stability under high temperature conditions.

[0043] The pH regulator is sodium carbonate or sodium hydroxide, which can be used alone or in combination;

[0044] The high temperature stabilizer is sodium sulfite or thiourea, which can be used alone or in combination;

[0045] Among them, the wetting agent is compounded according to the mass proportion: 30 parts of octylphenol polyoxyethylene ether, 40 parts of polyether modified silicone oil, and 30 parts of fatty alcohol ether phosphate; the wetting agent can improve the hydrophilic properties of the low-density lightener, so that it can be well dispersed in water, increase the solid phase content of the low-density lightener in water, and reduce the density further.

[0046] The low-density lightener is a polymer expanded microsphere, which has a hollow structure inside, a density of 45-70 kg / m3, a median particle size of 45-85 um, and a glass transition temperature of ≥100°C.

[0047] The self-foaming agent is azobisisobutyronitrile, which decomposes at a certain temperature to generate nitrogen, and the gas reduces the density of the liquid phase system, thereby reducing the density;

[0048] The foam binding agent is a compound of octadecyl dimethylamine oxide, isomeric alcohol ethers, and fatty alcohols; preferably, 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 generated by the self-foaming agent under the condition of the basic viscosity of the suspension stabilizer, so that it is stabilized in the liquid phase system.

[0049] Embodiment 2:

[0050] A self-foaming low-density well-killing fluid for low-pressure oil and gas field well repair:

[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 binder: 5 parts

[0058] Low density lightener: 40 parts

[0059] Among them, the suspension stabilizer is a compound of 40 parts of xanthan gum, 20 parts of unlun gum and 40 parts of guar gum in parts by mass; the compound of xanthan gum, unlun gum and guar gum will produce a good synergistic effect and improve the suspension ability on the one hand, and on the other hand, it will improve the temperature resistance effect and reflect the suspension stability under high temperature conditions.

[0060] The pH regulator is sodium carbonate or sodium hydroxide, which can be used alone or in combination;

[0061] The high temperature stabilizer is sodium sulfite or thiourea, which can be used alone or in combination;

[0062] The wetting agent is compounded by weight: 50 parts of octylphenol polyoxyethylene ether, 20 parts of polyether modified silicone oil, and 30 parts of fatty alcohol ether phosphate. The wetting agent can improve the hydrophilicity of the low-density reducing agent, so that it can be well dispersed in water, increase the solid content of the low-density reducing agent in water, and reduce the density even further.

[0063] The low-density lightener is a polymer expanded microsphere, which has a hollow structure inside, a density of 45-70 kg / m3, a median particle size of 45-85 um, and a glass transition temperature of ≥100°C.

[0064] The self-foaming agent is azobisisobutyronitrile, which decomposes at a certain temperature to generate nitrogen, and the gas reduces the density of the liquid phase system, thereby reducing the density;

[0065] The foam binding agent is a compound of octadecyl dimethylamine oxide, isomeric alcohol ethers, and fatty alcohols; preferably, 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 generated by the self-foaming agent under the condition of the basic viscosity of the suspension stabilizer, so that it is stabilized in the liquid phase system.

[0066] Embodiment 3:

[0067] A self-foaming low-density well-killing fluid for low-pressure oil and gas field well repair:

[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 binder: 8 parts

[0075] Low density lightener: 30 parts

[0076] The suspension stabilizer is prepared by compounding 50 parts of xanthan gum, 10 parts of vinasse gum and 40 parts of guar gum according to mass proportion. The compounding of xanthan gum, vinasse gum and guar gum can produce a good synergistic effect and improve the suspension capacity on the one hand, and can also improve the temperature resistance effect and reflect the suspension stability under high temperature conditions on the other hand.

[0077] The pH regulator is sodium carbonate or sodium hydroxide, which can be used alone or in combination;

[0078] The high temperature stabilizer is sodium sulfite or thiourea, which can be used alone or in combination;

[0079] The wetting agent is compounded by weight: 50 parts of octylphenol polyoxyethylene ether, 40 parts of polyether modified silicone oil, and 10 parts of fatty alcohol ether phosphate. The wetting agent can improve the hydrophilicity of the low-density reducing agent, so that it can be well dispersed in water, increase the solid content of the low-density reducing agent in water, and reduce the density even further.

[0080] The low-density lightener is a polymer expanded microsphere, which has a hollow structure inside, a density of 45-70 kg / m3, a median particle size of 45-85 um, and a glass transition temperature of ≥100°C.

[0081] The self-foaming agent is azobisisobutyronitrile, which decomposes at a certain temperature to generate nitrogen, and the gas reduces the density of the liquid phase system, thereby reducing the density;

[0082] The foam binding agent is a compound of octadecyl dimethylamine oxide, isomeric alcohol ethers, and fatty alcohols; preferably, 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 generated by the self-foaming agent under the condition of the basic viscosity of the suspension stabilizer, so that it is stabilized in the liquid phase system.

[0083] Embodiment 4:

[0084] A self-foaming low-density well-killing fluid for low-pressure oil and gas field well repair:

[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 binder: 10 parts

[0092] Low density lightener: 20 parts

[0093] Among them, the suspension stabilizer is a compound of 40 parts of xanthan gum, 30 parts of unlun gum and 30 parts of guar gum in parts by mass; the compound of xanthan gum, unlun gum and guar gum will produce a good synergistic effect and improve the suspension ability on the one hand, and on the other hand, it will improve the temperature resistance effect and reflect the suspension stability under high temperature conditions.

[0094] The pH regulator is sodium carbonate or sodium hydroxide, which can be used alone or in combination;

[0095] The high temperature stabilizer is sodium sulfite or thiourea, which can be used alone or in combination;

[0096] Among them, the wetting agent is compounded according to the mass proportion: 40 parts of octylphenol polyoxyethylene ether, 40 parts of polyether modified silicone oil, and 20 parts of fatty alcohol ether phosphate; the wetting agent can improve the hydrophilic properties of the low-density lightener, so that it can be well dispersed in water, increase the solid phase content of the low-density lightener in water, and reduce the density further.

[0097] The low-density lightener is a polymer expanded microsphere, which has a hollow structure inside, a density of 45-70 kg / m3, a median particle size of 45-85 um, and a glass transition temperature of ≥100°C.

[0098] The self-foaming agent is azobisisobutyronitrile, which decomposes at a certain temperature to generate nitrogen, and the gas reduces the density of the liquid phase system, thereby reducing the density;

[0099] The foam binding agent is a compound of octadecyl dimethylamine oxide, isomeric alcohol ethers, and fatty alcohols; preferably, 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 generated by the self-foaming agent under the condition of the basic viscosity of the suspension stabilizer, so that it is stabilized in the liquid phase system.

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

[0101] Table 1 Basic properties of self-foaming low-density well killing fluid

[0102] Killing 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] From the evaluation results, it can be seen that the four embodiments of the low-density well-killing fluid of the present invention have good rheological properties, can be pumped, have good inhibition performance, good reservoir protection effect, and the permeability recovery rate reaches more than 85%; 3 It is the reading of the liquid at 300r / min in a six-speed rotational viscometer, that is, the viscosity value.

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

[0105] The above describes the basic principles, main features and advantages of the present invention. Professionals and technicians in this industry should understand that the present invention is not limited to the above-mentioned embodiments. The above-mentioned embodiments only describe the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, and these changes and improvements will fall within the scope of the present invention to be protected.

Claims

1. Self-foaming low-density well killing fluid, characterized by: The well killing fluid comprises the following components in parts by mass: 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 lightener: 10-40 parts.

2. The self-foaming low-density well killing fluid according to claim 1, characterized in that: The suspension stabilizer is prepared by compounding 30-50 parts of xanthan gum, 30-40 parts of guar gum and 10-40 parts of wenlun gum according to mass parts.

3. The self-foaming low-density well killing fluid according to claim 1, characterized in that: The pH regulator is one or both of sodium carbonate and sodium hydroxide.

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

5. The self-foaming low-density well killing fluid according to claim 1, characterized in that: The wetting agent is prepared by compounding 30-50 parts of octylphenol polyoxyethylene ether, 20-40 parts of polyether modified silicone oil and 10-30 parts of fatty alcohol ether phosphate in parts by mass.

6. The self-foaming low-density well killing fluid according to claim 1, characterized in that: The low-density lightener is a polymer expanded microsphere, which has a hollow structure inside and a density of 45-70 Kg / m 3 , median particle size is 45-85um, glass transition temperature ≥100℃.

7. The self-foaming low-density well killing fluid according to claim 1, characterized in that: The self-foaming agent is azobisisobutyronitrile.