A composite foaming agent, foam drilling fluid, its preparation method and application

Abstract

This invention proposes a composite foaming agent, a foam drilling fluid, its preparation method, and its application. The composite foaming agent of this invention comprises a first foaming agent of zinc dialkyl thiophosphate (ZDDP) and a second foaming agent of alkyl sulfate, and water. The foam drilling fluid of this invention contains 0.3wt% to 0.8wt% composite foaming agent, 0.2wt% to 0.5wt% foam stabilizer, 1.5wt% to 3.0wt% filtration loss reducer, and the balance being water. The foam drilling fluid has a foam half-life of up to 240 min, a temperature resistance of up to 150℃, and an API filtration loss of ≤12 mL, which is significantly higher than the performance of foam drilling fluids prepared with conventional foaming agents.

Description

Technical Field

[0001] This invention relates to the field of drilling fluid technology, and in particular to a composite foaming agent, foam drilling fluid, its preparation method and application. Background Technology

[0002] Drilling fluid is an essential fluid system in the drilling process. It carries drill cuttings to the surface, supports the wellbore for stability, and cools and lubricates the drill bit. When drilling into formations with pressure exhaustion, the density of the drilling fluid needs to be reduced to prevent formation leakage. Therefore, a lighter medium is required. Injecting gas into the drilling fluid is a simple and effective method. However, this method can cause uneven density in the drilling fluid. As a result, foam drilling fluid was developed. This system produces stable and uniform foam that can be circulated in the wellbore and annulus.

[0003] Existing foam drilling fluid technologies, such as CN201410448547.8, 201610765406.8, and 201610821642.7, report on the preparation and use of foam drilling fluids. In the published literature, the foaming agents are mainly sulfonates, carboxylates, sulfates, alkyl ammonium bromide, betaine, and other conventional surfactants. The optimization of commonly used foam drilling fluid foaming agents mainly focuses on the optimization of currently used foaming agents and their compounding with other treatment agents. However, the poor compatibility between treatment agents results in poor foam stability and high cost, which restricts the application of foam drilling fluids.

[0004] Patent CN201610821642.7 discloses a foam drilling fluid, including a first foaming agent and a second foaming agent, both of which are conventional foaming materials. The system has a relatively low half-life of up to 80 minutes, and the amount of foaming agent used is relatively high, resulting in high cost. Patent CN 201210310014.4 discloses a foam drilling fluid with a foaming agent content of 0.5%~2.0%, and a maximum half-life of only 8.3 minutes. Patent CN 201410448547.8 discloses a solid-free, strongly inhibiting foam drilling fluid, whose foaming agent is dodecyl sulfonate or sodium α-olefin sulfonate. Patent CN 201610753824.5 discloses a high-lubricity microfoam drilling fluid and its preparation method, whose foaming agent is one of sodium sulfonate, potassium sulfonate, or calcium sulfonate. Patent CN 201310078767.1 discloses a high oil content micro foam drilling fluid, in which the foaming agent is an oil-water compatible foaming agent DRfoam-Ⅱ3-4. The micro foam drilling fluid improves the lubricity of the drilling fluid by adding light crude oil.

[0005] In summary, commonly used foaming agents are mainly sulfonates, carboxylates, sulfates, alkyl ammonium bromide, betaine, and other conventional surfactants, which have poor foaming performance and low stability. Summary of the Invention

[0006] To address the aforementioned problems in the prior art, this invention proposes a composite foaming agent, foam drilling fluid, its preparation method, and its application.

[0007] In a first aspect, the present invention provides a composite foaming agent, the components of which include: a first foaming agent, a second foaming agent, and water.

[0008] The first foaming agent is zinc dialkyl dithiophosphate as shown in Formula I.

[0009] Formula I

[0010] Wherein, R is a C1-C12 straight-chain or branched alkyl group, preferably a C1-C8 straight-chain or branched alkyl group, more preferably CH3, C2H5, C3H7, C4H9, or C5H 11 C6H 13 C7H 15 C8H 17 At least one of them.

[0011] The second foaming agent is a C10-C20 alkyl sulfate, preferably a C12-C16 alkyl sulfate alkali metal salt.

[0012] As a specific embodiment of the present invention, the mass ratio of the first foaming agent, the second foaming agent and water is (30~40):(8~15):(1~5).

[0013] As a specific embodiment of the present invention, the preparation method of the first foaming agent, zinc dialkyl dithiophosphate, includes:

[0014] S1: In an inert atmosphere, phosphorus pentasulfide and 2-ethylhexanol are added to toluene, heated to react, cooled, precipitated, and filtered to obtain thiophosphoric acid;

[0015] S2: In an inert atmosphere, the sulfuric acid obtained in step S1 is mixed with zinc oxide and catalyst and heated to react. After filtration and drying, zinc dialkyl dithiophosphate is obtained.

[0016] As a specific embodiment of the present invention, in step S1, the inert atmosphere includes a nitrogen atmosphere, an argon atmosphere, and a helium atmosphere, preferably a nitrogen atmosphere;

[0017] As a specific embodiment of the present invention, the molar ratio of phosphorus pentasulfide and 2-ethylhexanol is (4~5):1, preferably 4.2:1;

[0018] In a specific embodiment of the present invention, the heating reaction temperature is 100~110℃.

[0019] As a specific embodiment of the present invention, in step S2, the inert atmosphere includes a nitrogen atmosphere, an argon atmosphere, and a helium atmosphere, preferably a nitrogen atmosphere;

[0020] In a specific embodiment of the present invention, the mass ratio of thiophosphoric acid, zinc oxide and catalyst is (0.8~1.2):(0.6~1):(0.0001~0.02), preferably 1:0.8:0.01;

[0021] As a specific embodiment of the present invention, the catalyst is an activated carbon-supported zinc acetate catalyst;

[0022] As a specific embodiment of the present invention, the heating reaction temperature is 75~95℃;

[0023] As a specific embodiment of the present invention, the drying is preferably vacuum drying; the vacuum degree is -0.99 to -0.94 MPa; the drying temperature is 92 to 98°C; and the drying time is 3 to 8 hours.

[0024] As a specific embodiment of the present invention, the second foaming agent is at least one of sodium dodecyl sulfate, sodium tetradecyl sulfate, and sodium hexadecyl sulfate.

[0025] This invention utilizes zinc dialkyl dithiophosphate (ZDDP) from the lubricating oil industry as the first foaming agent. ZDDP products are metal soaps that readily decompose into water-soluble thiophosphates upon contact with water, resulting in excellent foaming properties. The second foaming agent is an alkyl sulfate. Under high-temperature, oxygen-free conditions, ZDDP partially decomposes into thiophosphates in a small amount of water and interacts with the alkyl sulfates, enhancing mutual polarization and thus improving its foaming ability.

[0026] The preparation of catalysts using zinc acetate supported on activated carbon greatly improves the activity of traditional catalysts (acetic acid, zinc acetate, ammonia), increases the surface area of ​​the catalyst, and reduces the amount of catalyst used. At the same time, since the saponification reaction is an exothermic reaction, the use of this catalyst ensures a balanced reaction, avoids intense local reactions and exothermic overheating, and effectively reduces the rapid increase of by-products and secondary reactants.

[0027] Secondly, the present invention provides a method for preparing a composite foaming agent, comprising: mixing a first foaming agent, a second foaming agent and water evenly to obtain the foaming agent.

[0028] As a specific embodiment of the present invention, the mass ratio of the first foaming agent, the second foaming agent and water is (30~40):(8~15):(1~5);

[0029] As a specific embodiment of the present invention, the mixing environment is under sealed oxygen-free conditions;

[0030] As a specific embodiment of the present invention, the mixing temperature is 250~350℃;

[0031] As a specific embodiment of the present invention, the mixing method involves stirring at a stirring speed of 1000~2000 rpm.

[0032] Thirdly, the present invention provides the application of the composite foaming agent in the field of drilling fluids.

[0033] As a specific embodiment of the present invention, the mass fraction of the composite foaming agent in the drilling fluid is 0.3wt%~0.8wt%.

[0034] Fourthly, the present invention provides a foam drilling fluid, the components of which include: 0.3wt% to 0.8wt% of a composite foaming agent, 0.2wt% to 0.5wt% of a foam stabilizer, 1.5wt% to 3.0wt% of a filtration loss reducer, and the balance being water.

[0035] As a specific embodiment of the present invention, the pH value of the foam drilling fluid is 8-10.

[0036] In a specific embodiment of the present invention, the foam stabilizer is polyvinyl alcohol with the molecular formula [C2H4O]n and the degree of polymerization n is preferably 22000~30000.

[0037] In a specific embodiment of the present invention, the filtration loss reducing agent is sulfonated phenolic resin SMP-1.

[0038] As a specific embodiment of the present invention, the foam drilling fluid further includes a pH adjuster; the pH adjuster includes NaOH and KOH.

[0039] This invention provides a foam drilling fluid and its preparation method, which has a foam half-life of up to 240 min, a temperature resistance of up to 150℃, and an API filtration loss of ≤12 mL, which is significantly higher than the performance of foam drilling fluids prepared with conventional foaming agents.

[0040] Fifthly, the present invention provides a method for preparing foam drilling fluid, comprising the following steps:

[0041] Step 1: Add the composite foaming agent to water and stir to fully dissolve and foam;

[0042] Step 2: Add foam stabilizer and filtration reducer to the composite foaming agent solution obtained in Step 1, and continue stirring to fully dissolve it to obtain the foam drilling fluid.

[0043] In a specific embodiment of the present invention, in steps 1 and 2, the stirring speed is independently 8000~12000 rpm and the stirring time is 5~40 min.

[0044] Sixthly, the present invention provides the application of the foam drilling fluid in the field of oil and gas well exploration and development.

[0045] All of the above-mentioned raw materials used in this invention can be prepared in-house or purchased commercially; this invention does not impose any particular limitations on them.

[0046] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0047] 1. The composite foaming agent of the present invention contains zinc dialkyl dithiophosphate, which has a unique structure with four ether oxygen bonds and four branched hydrophobic chains, thus improving its foaming ability. The presence of sulfur and phosphorus atoms improves its anchoring ability at the gas-liquid interface. The second foaming agent, sodium alkyl sulfate, has a strong foaming ability. The two are combined through sulfur bond affinity, thus having a synergistic effect to enhance foaming.

[0048] 2. The composite foaming agent of the present invention has strong temperature resistance, which can be increased from 120°C to 150°C of conventional foaming agents.

[0049] 2. The foam drilling fluid formed by this invention has high foam stability and a half-life of up to 240 minutes, which is nearly three times longer than that of conventional foam systems.

[0050] 3. The foam drilling fluid formed by this invention solves the problem of large filtration loss in existing foam drilling fluids, which may lead to poor wellbore stability.

[0051] 4. The foam drilling fluid formed by this invention has high stability, requires no frequent maintenance during drilling, does not require excessive treatment agents, and results in a low amount of waste foam. Furthermore, the defoaming time in the natural environment is less than 12 hours. The treatment agents contained are environmentally friendly and readily biodegradable. Detailed Implementation

[0052] The present invention will be further described below with reference to specific embodiments, but this does not constitute any limitation on the present invention.

[0053] The specific information of the reagents used in the various embodiments of the present invention is as follows:

[0054] Sodium dodecyl sulfate, purchased from Sinopharm Group, molecular formula C 12 H 25 SO4Na, molecular weight 288.

[0055] Sodium tetradecyl sulfate, purchased from Sinopharm Group, molecular formula C 14 H 29 SO4Na, molecular weight 316.

[0056] Sodium hexadecyl sulfate, purchased from Sinopharm Group, molecular formula C 16 H 33SO4Na, molecular weight 344.

[0057] Sulfonated phenolic resin SMP-1, purchased from Renqiu Yibang Environmental Protection Technology Co., Ltd., with a molecular weight of 1200.

[0058] The activated carbon-supported zinc acetate catalyst was manufactured by Sinopec Sichuan Vinylon Plant.

[0059] Phosphoric acid, purchased from Jinzhou Shengda Chemicals Co., Ltd., with the molecular formula C. 12 H 27 O2PS2, molecular weight 298.

[0060] Zinc oxide, purchased from Wuxi Guangcan Changyu New Material Technology Co., Ltd., has the molecular formula ZnO and a molecular weight of 65.

[0061] Toluene, purchased from Lude Chemical Co., Ltd. in Wupu Town, Yunmeng County, has the molecular formula C7H8.

[0062] Phosphorus pentasulfide, purchased from Hubei Xinrunde Chemical Co., Ltd., has the molecular formula P2O5 and a molecular weight of 191.

[0063] 2-Ethylhexanol, purchased from Shandong Xincheng Chemical Co., Ltd., molecular formula C8H 18 O, with a molecular weight of 130.

[0064] Example 1

[0065] This embodiment provides a method for preparing zinc dialkyl dithiophosphate, the details of which are as follows:

[0066] S1: Phosphoric acid sulfide reaction: In a three-necked flask equipped with a thermometer, electric stirrer, reflux condenser and tail gas treatment device, add phosphorus pentasulfide dissolved in toluene, and add 2-ethylhexanol at a molar ratio of 4.2:1 to phosphorus pentasulfide. Heat the mixture in an automatically temperature-controlled water bath to 110°C, ensuring that the temperature fluctuation during the reaction does not exceed ±5°C. Under N2 protection, stir the reaction for 5 hours, cool at room temperature, filter by sedimentation, and collect the filtrate to obtain phosphoric acid sulfide.

[0067] S2: Zinc saponification reaction: Phosphoric acid, zinc oxide and activated carbon-supported zinc acetate catalyst were added to a three-necked flask in a mass ratio of 1:0.8:0.01. The mixture was heated in an alcohol bath with automatic temperature control and protected with N2. The temperature was raised to 95°C, and the temperature fluctuation during the reaction was kept within ±3°C. The mixture was stirred for 6 hours.

[0068] S3: Vacuum drying filter: After the zinc soap reaction is completed, excess ZnO and catalyst are filtered out, and the product is dried for 4 hours under a vacuum of -0.99±0.05MPa and a temperature of 95±3℃ to obtain dioctyl dithiophosphate zinc.

[0069] The dialkyl dithiophosphate zinc obtained in Example 1 is dioctyl dithiophosphate zinc, and its molecular formula is: C 28 H 60 O4P2S4Zn.

[0070] Example 2

[0071] This embodiment provides a method for preparing zinc dialkyl dithiophosphate, the details of which are as follows:

[0072] S1: Phosphoric acid sulfide reaction: In a three-necked flask equipped with a thermometer, electric stirrer, reflux condenser and tail gas treatment device, add phosphorus pentasulfide dissolved in toluene, and add 2-ethylhexanol at a molar ratio of 4.2:1 to phosphorus pentasulfide. Heat the mixture in an automatically temperature-controlled water bath to 110°C, ensuring that the temperature fluctuation during the reaction does not exceed ±5°C. Under N2 protection, stir the reaction for 5 hours, cool at room temperature, filter by sedimentation, and collect the filtrate to obtain phosphoric acid sulfide.

[0073] S2: Zinc saponification reaction: Phosphoric acid, zinc oxide and activated carbon-supported zinc acetate catalyst were added to a three-necked flask in a mass ratio of 1:0.8:0.01. The mixture was heated in an alcohol bath with automatic temperature control and protected with N2. The temperature was raised to 95°C, and the temperature fluctuation during the reaction was kept within ±3°C. The mixture was stirred for 6 hours.

[0074] S3: Vacuum drying filter: After the zinc soap reaction is completed, excess ZnO and catalyst are filtered out, and the product is dried for 4 hours under a vacuum of -0.99±0.05MPa and a temperature of 95±3℃ to obtain zinc dipentyloctyl dithiophosphate.

[0075] The dialkyl dithiophosphate zinc obtained in Example 2 is dipentyloctyl dithiophosphate zinc, and its molecular formula is: C 20 H 44 O2P2S4Zn.

[0076] Example 3

[0077] This embodiment provides a method for preparing zinc dialkyl dithiophosphate, the details of which are as follows:

[0078] S1: Phosphoric acid sulfide reaction: In a three-necked flask equipped with a thermometer, electric stirrer, reflux condenser and tail gas treatment device, phosphorus pentasulfide dissolved in toluene was added. 2-Ethylhexanol was added at a molar ratio of 4.2:1 to phosphorus pentasulfide. The mixture was heated to 110°C using an automatically temperature-controlled water bath, ensuring that the temperature fluctuation during the reaction did not exceed ±5°C. N2 protection was applied, and the mixture was stirred for 5 hours. After cooling at room temperature, the mixture was filtered to collect the filtrate, which yielded phosphoric acid sulfide.

[0079] S2: Zinc saponification reaction: Phosphoric acid, zinc oxide and activated carbon-supported zinc acetate catalyst were added to a three-necked flask in a mass ratio of 1:0.8:0.01. The mixture was heated in an alcohol bath with automatic temperature control and protected with N2. The temperature was raised to 95°C, and the temperature fluctuation during the reaction was kept within ±3°C. The mixture was stirred for 6 hours.

[0080] S3: Vacuum drying filter: After the zinc soap reaction is completed, excess ZnO and catalyst are filtered out, and the product is dried for 4 hours under vacuum of -0.99±0.05MPa and temperature of 95±3℃ to obtain zinc di-n-butyl dithiophosphate.

[0081] The dialkyl dithiophosphate zinc obtained in Example 3 is di-n-butyl dithiophosphate zinc, and its molecular formula is: C 16 H 36 O4P2S4Zn.

[0082] Example 4

[0083] This embodiment provides a composite foaming agent and its preparation method, with specific details as follows:

[0084] The first foaming agent, zinc dioctyl dithiophosphate, the second foaming agent, sodium hexadecyl polyoxyethylene ether sulfate, and water prepared in Example 1 were mixed in a mass ratio of 35:12:2. The mixture was stirred at 1500 rpm for 3 hours under sealed and oxygen-free conditions at 300°C.

[0085] Example 5

[0086] This embodiment provides a foam drilling fluid and its preparation method. The composite foaming agent in the foam drilling fluid contains water. Since the balance of the foam drilling fluid is also water, only the first foaming agent and the second foaming agent are calculated in the composite foaming agent calculation. The specific details are as follows:

[0087] 0.5wt% composite foaming agent (the mass ratio of the first foaming agent, zinc butyloctyl dithiophosphate (T202), to the second foaming agent, sodium dodecyl sulfate, is 30:8), 0.2wt% polyvinyl alcohol ([C2H4O]). 22000 ), 1.5wt% sulfonated phenolic resin SMP-1, with the balance being water. The mass percentage of each component is based on water, and the pH of the foam drilling fluid system is adjusted to 8 using NaOH.

[0088] The method for preparing foam drilling fluid described in this embodiment includes the following steps:

[0089] Step 1: Add 0.5wt% composite foaming agent, continue stirring to fully dissolve it, increase the stirring speed to 10000rpm, stir for 30min, and foaming will occur;

[0090] Step 2: Add 0.2wt% polyvinyl alcohol ([C2H4O]). 22000 Continue stirring until fully dissolved, then add 1.5 wt% sulfonated phenolic resin SMP-1 and continue stirring until fully dissolved; increase the stirring speed to 10000 rpm and continue stirring for 5 min to 8 min to prepare the foam drilling fluid.

[0091] Example 6

[0092] This embodiment provides a foam drilling fluid and its preparation method. The composite foaming agent in the foam drilling fluid contains water. Since the balance of the foam drilling fluid is also water, only the first foaming agent and the second foaming agent are calculated in the composite foaming agent calculation. The specific details are as follows:

[0093] 0.5 wt% composite foaming agent (wherein the mass ratio of the first foaming agent, zinc di-n-butyl dithiophosphate, to the second foaming agent, sodium tetradecyl polyoxyethylene ether sulfate, is 32:10), 0.2 wt% polyvinyl alcohol ([C2H4O]). 24000 ), 1.5wt% sulfonated phenolic resin SMP-1, the balance being water, and the pH of the foam drilling fluid system was adjusted to 8 with KOH.

[0094] The method for preparing foam drilling fluid described in this embodiment includes the following steps:

[0095] Step 1: Add 0.5wt% composite foaming agent, continue stirring to fully dissolve it, increase the stirring speed to 10000rpm, stir for 30min, and foaming will occur;

[0096] Step 2: Add 0.2wt% polyvinyl alcohol ([C2H4O]). 24000 Continue stirring until fully dissolved, then add 1.5 wt% sulfonated phenolic resin SMP-1 and continue stirring until fully dissolved; increase the stirring speed to 10000 rpm and continue stirring for 5 min to 8 min to prepare the foam drilling fluid.

[0097] Example 7

[0098] This embodiment provides a foam drilling fluid and its preparation method. The composite foaming agent in the foam drilling fluid contains water. Since the balance of the foam drilling fluid is also water, only the first foaming agent and the second foaming agent are calculated in the composite foaming agent calculation. The specific details are as follows:

[0099] 0.5 wt% composite foaming agent (wherein the mass ratio of the first foaming agent, zinc dioctyl dithiophosphate, to the second foaming agent, sodium hexadecyl polyoxyethylene ether sulfate, is 38:15), 0.2 wt% polyvinyl alcohol ([C2H4O]). 26000), 1.5wt% sulfonated phenolic resin SMP-1, with the balance being water. The mass percentage of each component is based on water, and the pH of the foam drilling fluid system is adjusted to 8 using KOH.

[0100] The method for preparing foam drilling fluid described in this embodiment includes the following steps:

[0101] Step 1: Add 0.5wt% composite foaming agent, continue stirring to fully dissolve it, increase the stirring speed to 10000rpm, stir for 30min, and foaming will occur;

[0102] Step 2: Add 0.2wt% polyvinyl alcohol ([C2H4O]). 26000 Continue stirring until fully dissolved, then add 1.5 wt% sulfonated phenolic resin SMP-1 and continue stirring until fully dissolved; increase the stirring speed to 10000 rpm and continue stirring for 5 min to 8 min to prepare the foam drilling fluid.

[0103] Example 8

[0104] This embodiment provides a foam drilling fluid and its preparation method. The composite foaming agent in the foam drilling fluid contains water. Since the balance of the foam drilling fluid is also water, only the first foaming agent and the second foaming agent are calculated in the composite foaming agent calculation. The specific details are as follows:

[0105] 0.5wt% composite foaming agent (wherein the mass ratio of the first foaming agent, zinc dioctyl dithiophosphate, to the second foaming agent, sodium dodecyl polyoxyethylene ether sulfate, is 38:10), 0.2wt% polyvinyl alcohol ([C2H4O]). 28000 ), 1.5wt% sulfonated phenolic resin SMP-1, the balance being water, and the pH of the foam drilling fluid system was adjusted to 8 with KOH.

[0106] The method for preparing foam drilling fluid described in this embodiment includes the following steps:

[0107] Step 1: Add 0.5wt% composite foaming agent, continue stirring to fully dissolve it, increase the stirring speed to 10000rpm, stir for 30min, and foaming will occur;

[0108] Step 2: Add 0.2wt% polyvinyl alcohol ([C2H4O]). 28000 Continue stirring until fully dissolved, then add 1.5 wt% sulfonated phenolic resin SMP-1 and continue stirring until fully dissolved; increase the stirring speed to 10000 rpm and continue stirring for 5 min to 8 min to prepare the foam drilling fluid.

[0109] Example 9

[0110] This embodiment provides a foam drilling fluid and its preparation method. The composite foaming agent in the foam drilling fluid contains water. Since the balance of the foam drilling fluid is also water, only the first foaming agent and the second foaming agent are calculated in the composite foaming agent calculation. The specific details are as follows:

[0111] 0.5 wt% composite foaming agent (wherein the mass ratio of the first foaming agent, zinc dioctyl dithiophosphate, to the second foaming agent, sodium tetradecyl polyoxyethylene ether sulfate, is 40:15), 0.2 wt% polyvinyl alcohol ([C2H4O]). 30000 ), 1.5wt% sulfonated phenolic resin SMP-1, with the balance being water. The mass percentage of each component is based on water, and the pH of the foam drilling fluid system is adjusted to 8 using KOH.

[0112] The method for preparing foam drilling fluid described in this embodiment includes the following steps:

[0113] Step 1: Add 0.5wt% composite foaming agent, continue stirring to fully dissolve it, increase the stirring speed to 10000rpm, stir for 30min, and foaming will occur;

[0114] Step 2: Add 0.2wt% polyvinyl alcohol ([C2H4O]). 30000 Continue stirring until fully dissolved, then add 1.5 wt% sulfonated phenolic resin SMP-1 and continue stirring until fully dissolved; increase the stirring speed to 10000 rpm and continue stirring for 5 min to 8 min to prepare the foam drilling fluid.

[0115] Comparative Example

[0116] This comparative example provides a foam drilling fluid and its preparation method, with specific details as follows:

[0117] 0.5wt% foaming agent, sodium hexadecyl polyoxyethylene ether sulfate; 0.2wt% polyvinyl alcohol ([C2H4O]). 26000 ), 1.5wt% sulfonated phenolic resin SMP-1, with the balance being water. The mass percentage of each component is based on water, and the pH of the foam drilling fluid system is adjusted to 8 using KOH.

[0118] The method for preparing the foam drilling fluid described in this comparative example includes the following steps:

[0119] Step 1: Add 0.5wt% of foaming agent sodium cetyl polyoxyethylene ether sulfate, continue stirring to dissolve it completely, increase the stirring speed to 10000rpm, stir for 30min, and foaming will occur;

[0120] Step 2: Add 0.2wt% polyvinyl alcohol ([C2H4O]). 28000Continue stirring until fully dissolved, then add 1.5 wt% sulfonated phenolic resin SMP-1 and continue stirring until fully dissolved; increase the stirring speed to 10000 rpm and continue stirring for 5 min to 8 min to prepare the foam drilling fluid.

[0121] Test case

[0122] (1) Half-life and basic properties

[0123] The foam drilling fluids prepared in Examples 5-9 were immediately poured into a 1000 mL graduated cylinder, and the foam half-life was recorded. Separately, the foam drilling fluids prepared in Examples 5-9 were used to determine their rheological properties, filtration loss, and extreme pressure lubrication properties. Simultaneously, the composite foaming agent in Example 1 was replaced with sodium dodecylbenzenesulfonate in the same proportion as a comparative example, with other conditions remaining unchanged, and its performance was evaluated to illustrate the effectiveness of the invention. The results show that the foam drilling fluid of the present invention has a foam half-life of over 240 min, an extreme pressure lubrication coefficient ≤0.40, and a filtration loss ≤12 mL, which is significantly better than foam drilling fluids prepared with conventional foaming agents.

[0124] Table 1 Comparison of half-life and basic properties of foam drilling fluids

[0125]

[0126] (2) Temperature resistance

[0127] The prepared foam drilling fluids from Examples 5-9 were placed in an aging tank and kept at 120°C for 16 hours. After cooling to room temperature, they were stirred at 11000 rpm for 2 minutes, and then the basic and rheological properties of the foam drilling fluids were measured. The composite foaming agent in Example 1 was replaced with sodium dodecylbenzenesulfonate in the same proportion as a control, with other conditions unchanged. The performance was evaluated to illustrate the effectiveness of the invention. The results showed that after aging at 150°C for 16 hours, the half-life and viscosity of the foam drilling fluid decreased slightly, indicating that the system can withstand 150°C. In contrast, the control showed a greater decrease in half-life and viscosity, and its lubricity deteriorated.

[0128] Table 2 Comparison of Temperature Resistance of Foam Drilling Fluids

[0129]

[0130] In summary, this invention utilizes zinc dialkyl dithiophosphate (ZDDP) from the lubricating oil industry as the first foaming agent. ZDDP products are metal soaps that readily decompose into water-soluble thiophosphates upon contact with water, resulting in excellent foaming properties. The second foaming agent is an alkyl sulfate. Under high-temperature, oxygen-free conditions, ZDDP partially decomposes into thiophosphates in a small amount of water and interacts with the alkyl sulfates, enhancing mutual polarization and thus improving its foaming ability.

[0131] The preparation of catalysts using zinc acetate supported on activated carbon greatly improves the activity of traditional catalysts (acetic acid, zinc acetate, ammonia), increases the surface area of ​​the catalyst, and reduces the amount of catalyst used. At the same time, since the saponification reaction is an exothermic reaction, the use of this catalyst ensures a balanced reaction, avoids intense local reactions and exothermic overheating, and effectively reduces the rapid increase of by-products and secondary reactants.

[0132] This invention provides a foam drilling fluid and its preparation method, which has a foam half-life of up to 240 min, a temperature resistance of up to 150℃, and an API filtration loss of ≤12 mL, which is significantly higher than the performance of foam drilling fluids prepared with conventional foaming agents.

[0133] Any numerical value mentioned in this invention, if there is only a two-unit interval between any minimum and any maximum value, includes all values ​​that increase by one unit each time from the minimum to the maximum value. For example, if the amount of a component, or the value of a process variable such as temperature, pressure, or time, is stated as 50-90, in this specification it means specifically listing values ​​such as 51-89, 52-88… and 69-71 and 70-71, etc. For non-integer values, it may be appropriately considered that a unit is 0.1, 0.01, 0.001, or 0.0001. These are merely some specifically specified examples. In this application, in a similar manner, all possible combinations of numerical values ​​between the listed minimum and maximum values ​​are considered to have been disclosed.

[0134] It should be noted that the embodiments described above are only for explaining the present invention and do not constitute any limitation on the present invention. The present invention has been described with reference to typical embodiments, but it should be understood that the words used therein are descriptive and explanatory terms, not limiting terms. Modifications can be made to the present invention within the scope of the claims, and revisions can be made to the present invention without departing from the scope and spirit of the present invention. Although the present invention described herein relates to specific methods, materials, and embodiments, it does not mean that the present invention is limited to the specific examples disclosed herein; on the contrary, the present invention can be extended to all other methods and applications with the same function.

Claims

1. A composite foaming agent, characterized in that, Its components include: a first foaming agent, a second foaming agent, and water; The first foaming agent is zinc dialkyl dithiophosphate as shown in Formula I. Formula I Wherein, R is a C1-C12 straight-chain or branched alkyl group; The second foaming agent is a C10-C20 alkyl sulfate; The mass ratio of the first foaming agent to the second foaming agent is (30~40):(8~15).

2. The composite foaming agent according to claim 1, characterized in that, The mass ratio of the first foaming agent, the second foaming agent and the water is (30~40):(8~15):(1~5).

3. The composite foaming agent according to claim 1, characterized in that, R is a C1-C8 straight-chain or branched alkyl group.

4. The composite foaming agent according to claim 3, characterized in that, R is CH3, C2H5, C3H7, C4H9, C5H 11 C6H 13 C7H 15 C8H 17 At least one of them.

5. The composite foaming agent according to claim 1, characterized in that, The second foaming agent is a C12-C16 alkyl sulfate alkali metal salt.

6. The composite foaming agent according to claim 1, characterized in that, The preparation method of the first foaming agent, zinc dialkyl dithiophosphate, includes: S1: In an inert atmosphere, phosphorus pentasulfide and ROH are added to toluene, heated to react, cooled, precipitated, and filtered to obtain thiophosphoric acid; S2: In an inert atmosphere, the sulfuric acid obtained in step S1 is mixed with zinc oxide and catalyst and heated to react. After filtration and drying, zinc dialkyl dithiophosphate is obtained.

7. The composite foaming agent according to claim 6, characterized in that, In step S1, the inert atmosphere includes a nitrogen atmosphere, an argon atmosphere, and a helium atmosphere; And / or, the molar ratio of phosphorus pentasulfide to ROH is (4~5):1; And / or, the heating reaction temperature is 100~110℃.

8. The composite foaming agent according to claim 7, characterized in that, The inert atmosphere is a nitrogen atmosphere; And / or, the molar ratio of phosphorus pentasulfide to ROH is 4.2:

1.

9. The composite foaming agent according to claim 6, characterized in that, ROH is 2-ethylhexanol.

10. The composite foaming agent according to claim 6, characterized in that, In step S2, the inert atmosphere includes a nitrogen atmosphere, an argon atmosphere, and a helium atmosphere; The mass ratio of thiophosphoric acid, zinc oxide, and catalyst is (0.8~1.2):(0.6~1):(0.0001~0.02). The catalyst is a zinc acetate catalyst supported on activated carbon. And / or, the heating reaction temperature is 75~95℃; And / or, the drying is vacuum drying; the vacuum degree is -0.99 to -0.94 MPa; the drying temperature is 92 to 98°C; and the drying time is 3 to 8 hours.

11. The composite foaming agent according to claim 10, characterized in that, The inert atmosphere is a nitrogen atmosphere; And / or, the mass ratio of the thiophosphoric acid, zinc oxide and catalyst is 1.0: 0.8: 0.

01.

12. The composite foaming agent according to any one of claims 1-11, characterized in that, The second foaming agent is at least one of sodium dodecyl sulfate, sodium tetradecyl sulfate, and sodium hexadecyl sulfate.

13. A method for preparing the composite foaming agent according to any one of claims 1-12, characterized in that, include: The foaming agent is prepared by mixing the first foaming agent, the second foaming agent and water evenly.

14. The preparation method according to claim 13, characterized in that, The mass ratio of the first foaming agent, the second foaming agent, and water is (30~40):(8~15):(1~5); And / or, the mixing environment is under sealed, oxygen-free conditions; And / or, the mixing temperature is 250~350℃; And / or, the mixing method involves stirring at a speed of 1000~2000 rpm.

15. The application of the composite foaming agent according to any one of claims 1-12 or the composite foaming agent prepared by the preparation method according to claim 13 or 14 in the field of drilling fluids.

16. The application according to claim 15, characterized in that, The composite foaming agent has a mass fraction of 0.3wt% to 0.8wt% in the drilling fluid.

17. A foam drilling fluid, characterized in that, Its components include: 0.3wt% to 0.8wt% of the composite foaming agent as described in any one of claims 1-12 or the composite foaming agent prepared by the preparation method described in claim 13 or 14, 0.2wt% to 0.5wt% of the foam stabilizer, 1.5wt% to 3.0wt% of the filtration loss reducer, and the balance being water.

18. The foam drilling fluid according to claim 17, characterized in that, The pH value of the foam drilling fluid is 8-10.

19. The foam drilling fluid according to claim 17, characterized in that, The foam stabilizer is polyvinyl alcohol with the molecular formula [C2H4O]n and a degree of polymerization n of 22000~30000.

20. The foam drilling fluid according to any one of claims 17-19, characterized in that, The filtration loss reducer is sulfonated phenolic resin SMP-1.

21. The foam drilling fluid according to any one of claims 17-19, characterized in that, The foam drilling fluid also includes a pH adjuster.

22. The foam drilling fluid according to claim 21, characterized in that, The pH adjuster includes NaOH and KOH.

23. The method for preparing foam drilling fluid according to any one of claims 17-22, characterized in that, Includes the following steps: Step 1: Add the composite foaming agent to water and stir to fully dissolve and foam; Step 2: Add foam stabilizer and filtration reducer to the composite foaming agent solution obtained in Step 1, and continue stirring to fully dissolve it to obtain the foam drilling fluid.

24. The preparation method according to claim 23, characterized in that, In steps 1 and 2, the stirring speed is independently 8000~12000 rpm, and the stirring time is 5~40 min.

25. The application of the foam drilling fluid according to any one of claims 17-22 or the foam drilling fluid prepared by the preparation method according to claim 23 or 24 in the field of oil and gas well exploration and development.

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