Low-density foam well-killing fluid composition and low-density foam well-killing fluid, preparation method thereof and application thereof

Abstract

The present invention relates to the field of oil and gas reservoir development technology, and discloses a low-density foam well-killing fluid composition and a low-density foam well-killing fluid, a preparation method thereof, and an application thereof. The composition comprises a foaming agent, a foaming agent auxiliary agent, a foam stabilizer, a nano foam stabilizer, a fluid loss reducer, and water. Based on the total weight of the composition, the foaming agent is 0.02-0.3 weight percent, the foaming agent auxiliary agent is 0.02-0.3 weight percent, the foam stabilizer is 0.8-1.6 weight percent, the nano foam stabilizer is 0.01-0.1 weight percent, the fluid loss reducer is 0.8-1 weight percent, and the water is 96.7-98.35 weight percent. The foam density of the low-density foam well-killing fluid can be as low as 0.25 g / cm 3 The foam volume is up to 400mL and the foam stability time is up to 44h, with good foaming and stability.

Description

Technical Field

[0001] The present invention relates to the technical field of oil and gas reservoir development, and in particular to a low-density foam well-killing fluid composition and a low-density foam well-killing fluid, as well as a preparation method and application thereof. Background Art

[0002] During gas well repair, killing fluid is typically applied and circulation is established, using the killing fluid's column pressure to balance reservoir pressure. As oilfield development continues, reservoir pressure gradually decreases in some gas wells during mid-to-late production, with some reservoir pressure coefficients dropping as low as around 0.25. This leads to severe killing fluid loss during the killing process, making circulation virtually impossible. This, coupled with increased reservoir contamination, has led to a decline in reservoir production or even the inability to resume production in many gas wells after repair, significantly reducing individual well recovery rates. To meet these requirements, ensure efficient gas well development, and protect reservoirs, low-density killing fluids must be used during various operations when the reservoir pressure coefficient is low.

[0003] Currently used high-performance killing fluids are mostly made of resin-based materials that are difficult to degrade, which is not environmentally friendly. Ordinary inorganic salt-based killing fluids also suffer from high fluid loss. While currently used low-temperature, solid-free, low-damage killing fluid systems offer excellent performance and are environmentally friendly, they are not suitable for operations under high-temperature conditions. There is no suitable high-temperature, low-density killing fluid system suitable for highly water-sensitive and complex reservoirs.

[0004] Therefore, developing a multifunctional low-density well-killing fluid with excellent high-temperature resistance, good oil and gas layer protection and corrosion inhibition effects, and excellent filtration loss is the current research hotspot and focus in this field. This has very important industrial value and scientific research significance for the advancement of oil exploration and production technology. Summary of the Invention

[0005] The purpose of the present invention is to overcome the problems of low-density well-killing fluid in the prior art, such as being environmentally unfriendly, having a large amount of leakage, and being unsuitable for operation under high temperature conditions. The present invention provides a low-density foam well-killing fluid composition and a low-density foam well-killing fluid, as well as a preparation method and application thereof. The foam density of the low-density foam well-killing fluid can be as low as 0.25 g / cm 3 The foam volume is up to 400mL and the foam stability time is up to 44h, with good foaming and stability.

[0006] To achieve the above-mentioned object, the first aspect of the present invention provides a low-density foam well-killing fluid composition, wherein the low-density foam well-killing fluid composition comprises a foaming agent, a foaming agent auxiliary agent, a foam stabilizer, a nano foam stabilizer, a fluid loss reducer and water. Based on the total weight of the low-density foam well-killing fluid composition, the content of the foaming agent is 0.02-0.3 weight%, the content of the foaming agent auxiliary agent is 0.02-0.3 weight%, the content of the foam stabilizer is 0.8-1.6 weight%, the content of the nano foam stabilizer is 0.01-0.1 weight%, the content of the fluid loss reducer is 0.8-1 weight%, and the content of the water is 96.7-98.35 weight%.

[0007] The second aspect of the present invention provides a low-density foam well-killing fluid prepared from the aforementioned low-density foam well-killing fluid composition.

[0008] A third aspect of the present invention provides a method for preparing the aforementioned low-density foam well-killing fluid, wherein, under nitrogen protection and under stirring conditions, a foaming agent, a foaming agent auxiliary agent, a foam stabilizer, a nano foam stabilizer, and a fluid loss reducer are contacted and mixed with water to obtain a low-density foam well-killing fluid.

[0009] A fourth aspect of the present invention provides an application of the aforementioned low-density foam well-killing fluid in workover operations in natural gas deep wells and / or natural gas ultra-deep wells.

[0010] Through the above technical solution, the technical solution of the present invention has the following advantages:

[0011] (1) The density of the low-density foam well-killing fluid of the present invention is as low as 0.25 g / cm 3 It can solve the problem of low-density killing fluid and reduce the loss of killing fluid. At the same time, it has strong resistance to temperature, salt and oil, and can meet the requirements of deep or ultra-deep well repair operations.

[0012] (2) The preparation process of the low-density foam well-killing fluid of the present invention is simple and time-saving, and does not require a long temperature-raising and dissolving process. Most reagents are easily soluble in water, which greatly reduces the requirements for equipment.

[0013] (3) The density of the low-density foam well-killing fluid system of the present invention is 0.25g / cm 3 -0.9g / cm 3 It can be used in lower pressure gas layers, with a foam stability time of up to 44 hours, a NaCl resistance of up to 25%, and excellent CaCl2 and temperature resistance, and can meet the requirements of well repair operations under high temperature and high mineralization conditions in deep wells. DETAILED DESCRIPTION

[0014] The endpoints of the ranges and any values ​​disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoints of each range, the endpoints of each range and individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered to be specifically disclosed herein.

[0015] A first aspect of the present invention provides a low-density foam well-killing fluid composition, wherein the low-density foam well-killing fluid composition includes a foaming agent, a foaming agent auxiliary agent, a foam stabilizer, a nano foam stabilizer, a fluid loss reducer and water. Based on the total weight of the low-density foam well-killing fluid composition, the content of the foaming agent is 0.02-0.3 weight%, the content of the foaming agent auxiliary agent is 0.02-0.3 weight%, the content of the foam stabilizer is 0.8-1.6 weight%, the content of the nano foam stabilizer is 0.01-0.1 weight%, the content of the fluid loss reducer is 0.8-1 weight%, and the content of water is 96.7-98.35 weight%.

[0016] The inventors of the present invention have discovered that the foaming agent of the present invention is a surfactant, which can improve the stability of the foam at a specific content and after being compounded in a specific weight ratio; the surface tension of the liquid can be significantly reduced by adding a small amount of surfactant, and one end of the surfactant is a non-polar hydrocarbon chain with very little affinity for water, often called a hydrophobic group; the other end is a polar group with a great affinity for water, so it is called a hydrophilic group, collectively known as an "amphiphilic molecule". For stability, when the surfactant is dissolved in water, two methods can be adopted: 1. Forming a monomolecular film on the liquid surface; 2. Forming "micelles". In addition, the foam stabilizer is a viscosity-increasing stabilizer and has strong salt resistance; the compounding of the two can play a bonding and thickening role, thereby increasing the stability of the foam;

[0017] According to the present invention, preferably, based on the total weight of the low-density foam well-killing fluid composition, the content of the foaming agent is 0.1-0.3 weight%, the content of the foaming agent auxiliary is 0.1-0.3 weight%, the content of the foam stabilizer is 0.95-1.6 weight%, the content of the nano foam stabilizer is 0.03-0.1 weight%, the content of the fluid loss reducer is 0.8-1 weight%, and the content of water is 96.7-98.02 weight%.

[0018] According to the present invention, preferably, based on the total weight of the low-density foam well-killing fluid composition, the content of the foaming agent is 0.15-0.3 weight%, the content of the foaming agent auxiliary is 0.15-0.3 weight%, the content of the foam stabilizer is 1.1-1.6 weight%, the content of the nano foam stabilizer is 0.05-0.1 weight%, the content of the fluid loss reducer is 0.9-1 weight%, and the content of water is 96.7-97.2 weight%.

[0019] According to the present invention, preferably, based on the total weight of the low-density foam well-killing fluid composition, the content of the foaming agent is 0.25-0.3 weight%, the content of the foaming agent auxiliary is 0.2-0.3 weight%, the content of the foam stabilizer is 1.4-1.6 weight%, the content of the nano foam stabilizer is 0.08-0.1 weight%, the content of the fluid loss reducer is 0.9-1 weight%, and the content of water is 96.7-97.0 weight%.

[0020] In the present invention, under the above-mentioned specific components and specific content ratios, the low-density foam well-killing fluid prepared from the prepared low-density foam well-killing fluid composition has low foam density and good foamability and stability.

[0021] According to the present invention, the foaming agent is an anionic surfactant; preferably, the foaming agent is sodium dodecyl sulfate (SDS); in the present invention, the foaming agent components are limited to the aforementioned specific components, and the weight ratio of the sodium dodecyl sulfate is limited to the aforementioned specific range, which has good foaming properties and stability.

[0022] According to the present invention, the foaming agent auxiliary agent is an anionic surfactant; preferably, the foaming agent auxiliary agent is lauryl betaine and / or sodium secondary alkyl sulfonate (ZL-2); more preferably, the foaming agent auxiliary agent is sodium secondary alkyl sulfonate; in the present invention, the foaming agent auxiliary agent ZL-2 is purchased from Shandong Yousuo Chemical Technology Co., Ltd.

[0023] According to the present invention, the weight ratio of the foaming agent to the foaming agent auxiliary is (1-2):1. Preferably, the weight ratio of the foaming agent to the foaming agent auxiliary is (1-1.5):1; more preferably, the weight ratio of the foaming agent to the foaming agent auxiliary is (1-1.25):1; and further preferably, the weight ratio of the foaming agent to the foaming agent auxiliary is 1:1.

[0024] According to the present invention, the foam stabilizer is selected from carboxymethyl guar gum and polyacrylamide (PAM). Carboxymethyl guar gum is typically a pale yellow powder, soluble in water, and its aqueous solution has high viscosity, high temperature resistance, good salt tolerance, and strong stability. The carboxymethyl guar gum was purchased from Sinopec Kunlun Branch and has a high viscosity parameter. Polyacrylamide (PAM) was purchased from Shanghai Aladdin Biotechnology Co., Ltd.

[0025] According to the present invention, the nano foam stabilizer is an important water-soluble polymer with flocculation, shear resistance, drag reduction, dispersibility, etc.; in the present invention, the Chinese name of the nano foam stabilizer is neutral silicon solution, purchased from Shandong Better New Materials Co., Ltd., model N3010, wherein the silicon dioxide content is 30%.

[0026] According to the present invention, the weight ratio of the carboxymethyl guar gum, the polyacrylamide, and the nanofoam stabilizer is (1-2):1:(0.01-0.3); preferably, the weight ratio of the carboxymethyl guar gum, the polyacrylamide, and the nanofoam stabilizer is (1-1.5):1:(0.02-0.2); more preferably, the weight ratio of the carboxymethyl guar gum, the polyacrylamide, and the nanofoam stabilizer is 1:1:(0.025-0.167). In the present invention, limiting the components of the foam stabilizer and the nanofoam stabilizer to the aforementioned specific components, and limiting the weight ratio of the foam stabilizer to the nanofoam stabilizer to the aforementioned specific range, has good foaming properties and stability.

[0027] According to the present invention, the fluid loss reducer is one or more of sodium carboxymethyl cellulose (CMC) and hydroxyethyl cellulose (HEC).

[0028] In the present invention, the sodium carboxymethyl cellulose (CMC) is a white or milky white fibrous powder or granules with a density of 0.5-0.7 g / cm 3 It is virtually odorless, tasteless, and hygroscopic. It easily disperses in water to form a transparent colloidal solution and is insoluble in organic solvents such as ethanol. The pH of a 1% aqueous solution is 6.5-8.5. When the pH is > 10 or < 5, the viscosity of the mortar decreases significantly, with optimal performance at pH = 7. In the present invention, the fluid loss additive is purchased from Aladdin, model C104986, with a viscosity of 1000-1400 mPa.s, USP grade, and a molecular weight of 264.204 g / mol.

[0029] In the present invention, hydroxyethyl cellulose (HEC) is a white or light yellow, odorless, non-toxic, fibrous or powdered solid prepared by etherification of alkaline cellulose and ethylene oxide (or chloroethanol). It belongs to the class of non-ionic soluble cellulose ethers. HEC has excellent properties such as thickening, suspending, dispersing, emulsifying, bonding, film-forming, moisture-retaining, and providing protective colloids.

[0030] According to the present invention, the weight ratio of the sodium carboxymethyl cellulose to the sodium hydroxyethyl cellulose is (1-2):1; preferably, the weight ratio of the sodium carboxymethyl cellulose to the sodium hydroxyethyl cellulose is (1-1.5):1; more preferably, the weight ratio of the sodium carboxymethyl cellulose to the sodium hydroxyethyl cellulose is 1:1. In the present invention, the components of the fluid loss additive are limited to the aforementioned specific components, and the weight ratio of the sodium carboxymethyl cellulose to the sodium hydroxyethyl cellulose is limited to the aforementioned specific range, thereby achieving good foaming properties and stability.

[0031] According to the present invention, the water is tap water.

[0032] The second aspect of the present invention provides a low-density foam well-killing fluid prepared from the aforementioned low-density foam well-killing fluid composition.

[0033] According to the present invention, the density of the low-density foam well killing fluid is 0.25-0.9 g / cm 3 , preferably 0.25-0.8g / cm 3 , preferably 0.25-0.5g / cm 3 , preferably 0.25-0.4g / cm 3 , preferably 0.25-0.33 g / cm 3 , preferably 0.25-0.29 g / cm 3 .

[0034] According to the present invention, the foam volume of the low-density foam well killing fluid is 125-400 mL, preferably 200-400 mL, preferably 250-400 mL, preferably 300-400 mL, preferably 350-400 mL; the foam stability time is 34-44 h, preferably 38-44 h, preferably 40-44 h, preferably 41-44 h, preferably 43-44 h; and the high temperature resistance temperature is 100-120 ° C, preferably 100-110 ° C.

[0035] A third aspect of the present invention provides a method for preparing the aforementioned low-density foam well-killing fluid, wherein, under nitrogen protection and under stirring conditions, a foaming agent, a foaming agent auxiliary agent, a foam stabilizer, a nano foam stabilizer, and a fluid loss reducer are contacted and mixed with water to obtain a low-density foam well-killing fluid.

[0036] According to the present invention, the mixing conditions include: at a temperature of 25°C, a stirring rate of 8000-9000 r / min, and a stirring time of 2-5 min; preferably, at a temperature of 25°C, a stirring rate of 8000 r / min, and a stirring time of 2 min.

[0037] The present invention uses sodium dodecyl sulfate (SDS) as a foaming agent, ZL-2 as a foaming agent auxiliary, sodium carboxymethyl cellulose (CMC) and hydroxyethyl cellulose (HEC) as fluid loss reducers, and carboxymethyl guar gum, polyacrylamide, and a nano-foam stabilizer as foam stabilizers. These are mixed and dissolved in clean water. The prepared well-killing fluid base fluid is poured into a mixing cup and produced using the Waning-Blender method to obtain an adjustable foamed well-killing fluid. This preparation process is simple and easy to perform, with minimal pollution.

[0038] According to a preferred embodiment of the present invention, a method for preparing a low-density foam well killing fluid comprises:

[0039] (1) Accurately weigh the foaming agent, foaming agent adjuvant, foam stabilizer, nano foam stabilizer, fluid loss reducer and tap water according to the ratio of the aforementioned low-density foam well killing fluid;

[0040] (2) At room temperature, add the foaming agent, foaming agent auxiliary, foam stabilizer, nano foam stabilizer and fluid loss reducer into tap water respectively, stir and mix thoroughly, then pour into the stirring cup, introduce appropriate amount of nitrogen into the stirring cup, stir at 8000-9000r / min for 2-5min, and obtain a density of 0.25g / cm 3 -0.9g / cm 3 Adjustable low-density foam killing fluid.

[0041] The detailed process of the above steps is as follows:

[0042] (1) Preparation of low-density foam well-killing fluid composition (base material preparation): weigh a certain proportion of sodium dodecyl sulfate (SDS), sodium secondary alkyl sulfonate (ZL-2), carboxymethyl guar gum, polyacrylamide (PAM), sodium carboxymethyl cellulose (CMC), and hydroxyethyl cellulose (HEC) for use, with each component accurate to one ten-thousandth;

[0043] (2) Preparation method: First, sodium dodecyl sulfate (SDS), sodium secondary alkyl sulfonate (ZL-2), carboxymethyl guar gum, polyacrylamide (PAM), sodium carboxymethyl cellulose (CMC), and hydroxyethyl cellulose (HEC) are dissolved in tap water at 25°C, mixed thoroughly, and poured into a stirring cup. An appropriate amount of nitrogen is introduced into the stirring cup, and stirred at 8000-9000 r / min for 2-5 minutes to obtain a low-density foam well-killing fluid.

[0044] A fourth aspect of the present invention provides an application of the aforementioned low-density foam well-killing fluid in workover operations in natural gas deep wells and / or natural gas ultra-deep wells.

[0045] The present invention will be described in detail below through examples.

[0046] Example 1

[0047] This embodiment is intended to illustrate the low-density foam well-killing fluid prepared by using the low-density foam well-killing fluid composition of the present invention.

[0048] (1) Preparation of low-density foam well-killing fluid composition: Weigh a certain proportion of sodium dodecyl sulfate (SDS), sodium secondary alkyl sulfonate (ZL-2), carboxymethyl guar gum, polyacrylamide (PAM), sodium carboxymethyl cellulose (CMC), and hydroxyethyl cellulose (HEC) to the nearest ten thousandth of each component; the content of each component is shown in Table 1;

[0049] (2) Preparation method: First, sodium dodecyl sulfate (SDS), sodium secondary alkyl sulfonate (ZL-2), carboxymethyl guar gum, polyacrylamide (PAM), sodium carboxymethyl cellulose (CMC), and hydroxyethyl cellulose (HEC) are dissolved in water at 25°C, mixed thoroughly, and poured into a stirring cup. An appropriate amount of nitrogen is introduced into the stirring cup, and stirred at 8000 r / min for 2 minutes to obtain a low-density foam well-killing fluid, which is marked as S1.

[0050] Examples 2-6

[0051] This embodiment is intended to illustrate the low-density foam well-killing fluid prepared by using the low-density foam well-killing fluid composition of the present invention.

[0052] A low-density foam well-killing fluid was prepared in the same manner as in Example 1, except that:

[0053] (1) The contents of each component are shown in Table 1.

[0054] The results were low-density foam killing fluids, which were labeled as S2, S3, S4, S5 and S6 respectively.

[0055] Comparative Examples 1-3

[0056] A low-density foam well-killing fluid was prepared in the same manner as in Example 1, except that:

[0057] (1) The contents of each component are shown in Table 1.

[0058] The results were low-density foam killing fluids, which were labeled as DS1, DS2 and DS3 respectively.

[0059] Test Example 1

[0060] The properties of the low-density foam well killing fluids prepared in Examples 1-6 and Comparative Examples 1-3 were tested.

[0061] Specifically, 100 mL of the low-density foam killing fluid base prepared in Examples 1-6 and Comparative Examples 1-3 was added to a stirring cup and stirred at 8000 r / min for 2 minutes. After stirring stopped, the mixture was quickly poured into a 500 mL graduated cylinder to measure the volume of the foam. The time required for 50 mL of liquid to precipitate was recorded, which was the half-life of the foam.

[0062] Density test: According to the density calculation formula, density is equal to mass divided by volume to obtain the density of the foam fluid.

[0063] Foam volume test: The foam fluid is introduced into a 500 mL graduated cylinder to measure the volume of the foam.

[0064] Stability time test: Start timing when the foam fluid is poured into the measuring cylinder, and record the time required for 50 mL of liquid to precipitate, which is the half-life of the foam.

[0065] The performance test results of foam killing fluids with different formulations are shown in Table 1.

[0066] Table 1

[0067]

[0068]

[0069] Test Example 2

[0070] The NaCl resistance of the low-density foam well-killing fluid prepared in Example 2 was tested.

[0071] Specifically, 100 mL of the low-density foam killing fluid base prepared in Example 2 was added to a beaker, followed by the addition of 1 g, 1.5 g, 2 g, and 2.5 g of NaCl, respectively. The mixture was stirred at high speed (8000 rpm) for 2 min. After stopping stirring, the mixture was quickly poured into a 500 mL graduated cylinder to measure the volume of the foam. The foaming volume and half-life were recorded to determine the foaming ability and foam stabilization performance of the system and analyze the salt tolerance. The NaCl tolerance of the low-density foam killing fluid prepared in Example 2 was tested, and the results of the NaCl tolerance test of the foam killing fluid are shown in Table 2.

[0072] Table 2

[0073] Serial number NaCl concentration / (mg / L) Foaming volume / mL Half-life / h Foam appearance 1 0 200 38 Small and uniform 2 100000 190 28 Small and uniform 3 150000 170 19 Small and uniform 4 200000 160 11 Small and uniform 5 250000 150 6 Small and uniform

[0074] As can be seen from Table 2, Example 2 still has good performance when the NaCl addition amount is 200,000 mg / L.

[0075] Test Example 3

[0076] The CaCl2 resistance of the low-density foam well-killing fluid prepared in Example 2 was tested.

[0077] Specifically: add 100mL of the low-density foam killing fluid base fluid prepared in Example 2 into a beaker, then add 0.5g and 1g of CaCl2 respectively, stir at high speed (8000r / min) for 2min, and after stopping stirring, quickly pour the mixture into a 500mL graduated cylinder to measure the volume of foam, record its foaming volume and half-life, thereby measuring the foaming ability and foam stabilization performance of the system, and analyze salt tolerance. Wherein, the CaCl2 resistance of the low-density foam killing fluid prepared in Example 2 was tested, and the CaCl2 resistance of the foam killing fluid performance test results are as shown in Table 3.

[0078] Table 3

[0079] Serial number <![CDATA[CaCl2 concentration / (mg / L)]]> Foaming volume / mL Stabilization time / h Foam appearance 1 0 200 38 Small and uniform 2 50000 190 30 Small and uniform 3 100000 180 21 Small and uniform 4 150000 170 13 Small and uniform 5 200000 150 8 Small and uniform

[0080] As can be seen from Table 3, Example 2 still has good performance when the CaCl2 addition amount is 150000 mg / L.

[0081] Test Example 4

[0082] The temperature resistance of the low-density foam well-killing fluid prepared in Example 2 was tested.

[0083] Specifically, 100 mL of the low-density foam well-killing fluid base prepared in Example 2 was added to a beaker, and then 1 g, 1.5 g, 2, and 2.5 g of NaCl were added, respectively. The mixture was stirred at high speed (8000 rpm) for 2 min. After stopping the stirring, the mixture was quickly poured into a 500 mL graduated cylinder to measure the volume of the foam, and its foaming volume and half-life were recorded to determine the foaming ability and foam stabilization performance of the system and analyze the salt resistance.

[0084] The temperature resistance of the low-density foam killing fluid prepared in Example 2 was tested. The test results of the temperature resistance of the foam killing fluid are shown in Table 4.

[0085] Table 4

[0086] Serial number Experimental conditions Foaming volume / mL Stabilization time / h Foam appearance 1 normal temperature 200 38 Small and uniform 2 100℃ 180 28 Small and uniform 3 120℃ 170 26 Small and uniform

[0087] The results can be seen from Table 4: Example 2 has better temperature resistance.

[0088] Test Example 5

[0089] The NaCl resistance of the low-density foam well-killing fluids prepared in Examples 1-6 and Comparative Examples 1-3 was tested using the same method as in Test Example 2, wherein the NaCl concentration was 100,000 mg / L.

[0090] The CaCl2 resistance of the low-density foam killing fluids prepared in Examples 1-6 and Comparative Examples 1-3 was tested using the same method as in Test Example 2, wherein the CaCl2 concentration was 100,000 mg / L.

[0091] The temperature resistance of the low-density foam well killing fluids prepared in Examples 1-6 and Comparative Examples 1-3 was tested in the same manner as in Test Example 2, wherein the temperature in the experimental conditions was 100°C.

[0092] The performance test results of the foam killing fluid are shown in Table 5.

[0093] Table 5

[0094]

[0095] It can be seen from the above results that the low-density foam well killing fluid prepared by Examples 1-6 of the present invention has significantly better effects.

[0096] Compared with Example 6, Comparative Example 1 does not add the nano foam stabilizer; compared with Example 6, Comparative Example 2 does not add 0.3% SDS; compared with Example 6, Comparative Example 3 does not add 0.6% PAM; the results are not as good as Example 6; it shows that by adopting the components, component contents and specific compounding ratios specifically defined by the present invention, better effects can be obtained.

[0097] The preferred embodiments of the present invention have been described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, various simple variations of the technical solution of the present invention may be made, including combining the various technical features in any other appropriate manner. These simple variations and combinations should also be regarded as disclosed in the present invention and fall within the scope of protection of the present invention.

Claims

1. A low-density foam well-killing fluid composition, characterized in that: The low-density foam well-killing fluid composition comprises a foaming agent, a foaming agent auxiliary, a foam stabilizer, a nano foam stabilizer, a fluid loss reducer and water. Based on the total weight of the low-density foam well-killing fluid composition, the content of the foaming agent is 0.02-0.3 weight%, the content of the foaming agent auxiliary is 0.02-0.3 weight%, the content of the foam stabilizer is 0.8-1.6 weight%, the content of the nano foam stabilizer is 0.01-0.1 weight%, the content of the fluid loss reducer is 0.8-1 weight%, and the content of water is 96.7-98.35 weight%. Wherein, the foaming agent is sodium lauryl sulfate; The foaming agent auxiliary agent is lauryl betaine and / or sodium secondary alkyl sulfonate; and the weight ratio of the foaming agent to the foaming agent auxiliary agent is (1-2):1; The foam stabilizers are carboxymethyl guar gum and polyacrylamide; The nano foam stabilizer is a neutral silicon solution; and the weight ratio of the carboxymethyl guar gum, the polyacrylamide and the nano foam stabilizer is (1-2):1:(0.01-0.3); The fluid loss reducer comprises sodium carboxymethyl cellulose and sodium hydroxyethyl cellulose; and the weight ratio of the sodium carboxymethyl cellulose to the sodium hydroxyethyl cellulose is (1-2):

1.

2. The composition according to claim 1, wherein Based on the total weight of the low-density foam well-killing fluid composition, the content of the foaming agent is 0.1-0.3 weight%, the content of the foaming agent auxiliary is 0.1-0.3 weight%, the content of the foam stabilizer is 0.95-1.6 weight%, the content of the nano foam stabilizer is 0.03-0.1 weight%, the content of the fluid loss reducer is 0.8-1 weight%, and the content of water is 96.7-98.02 weight%.

3. A low-density foam well-killing fluid prepared from the low-density foam well-killing fluid composition according to claim 1 or 2.

4. The low-density foam well killing fluid according to claim 3, wherein: The density of the low-density foam well killing fluid is 0.25-0.9 g / cm 3 .

5. The low-density foam well killing fluid according to claim 4, wherein: The density of the low-density foam well-killing fluid is 0.25-0.8 g / cm 3 .

6. A method for preparing the low-density foam well killing fluid according to any one of claims 3 to 5, characterized in that: Under nitrogen protection and stirring conditions, a foaming agent, a foaming agent auxiliary agent, a foam stabilizer, a nano foam stabilizer, a fluid loss reducer and water are contacted and mixed to obtain a low-density foam well-killing fluid.

7. Use of the low-density foam well-killing fluid according to any one of claims 3 to 5 in workover operations of natural gas deep wells and / or natural gas ultra-deep wells.

Images