Foam reinforcing agent for high-temperature-resistant microfoam drilling fluid as well as preparation method and application of foam reinforcing agent

Abstract

The invention belongs to the field of treating agents for oil field drilling fluids, and particularly relates to a foam reinforcing agent for a high-temperature-resistant microfoam drilling fluid as well as a preparation method and application of the foam reinforcing agent. The foam reinforcing agent provided by the invention contains a compound with a structure as shown in a formula (I), in the formula (I), R1 is-COONa or-CONH2, R2 is-C6H4SO3Na, R3 is-CONHC (CH3) 2CH2SO3Na or-COOCH (CH2CH3) CH2SO3Na, and n is an integer between 5 and 20, and n is an integer between 5 and 20. The number-average molecular weight of the compound with the structure as shown in the formula (I) is 50,000-100,000. The foam reinforcing agent provided by the invention can obviously increase the arrangement density of a foaming agent on a micro-bubble wall and the thickness of the micro-bubble wall, improve the sealing performance of air nuclei in micro-bubbles, enhance the stability and compression resistance of the micro-bubbles under high-temperature and high-pressure conditions, and improve the leakage-proof performance of the micro-bubble drilling fluid. # imgabs0 #

Description

Technical Field

[0001] The invention belongs to the field of treating agents for oilfield drilling fluids, and in particular relates to a foam enhancer for high-temperature resistant microbubble drilling fluids, and a preparation method and application thereof. Background Art

[0002] At present, during the drilling process of low-pressure reservoirs at home and abroad, due to the low formation pressure coefficient (less than 1.0), the use of conventional drilling fluid is very likely to cause well leakage, affecting the safety of underground construction. For this type of formation, low-density drilling fluid is often used for drilling to reduce drilling fluid leakage. At present, a micro-bubble drilling fluid has been developed in China, which has the advantages of low density and no need to add injection gas equipment on site. It can effectively prevent low-pressure crushing, high permeability sandstone and fracture leakage formation leakage, protect oil and gas layers, and reduce drilling costs.

[0003] The Chinese patent with application number 200710113558.0 discloses a high temperature resistant recyclable micro-foam drilling fluid or completion fluid, wherein the foaming agent is fatty alcohol glyceryl ether sulfonate AGES, polyol, coconut oil amide sulfosuccinic acid monoester sodium salt F873, and the foam stabilizer is a mixture of LV-CMC and HV-PAC. The biggest advantage of the micro-foam drilling fluid is that the micro-foam therein can gather at the bottom of the well to block the micro-cracks in the well wall, thereby achieving the purpose of preventing (or reducing) the loss of the drilling fluid. Therefore, the micro-foam must maintain a certain compression resistance under the high pressure condition at the bottom of the well to prevent the foam wall from breaking and affecting the leakage-proof performance of the micro-foam drilling fluid. However, although the mixture of LV-CMC and HV-PAC can increase the viscosity of the drilling fluid and improve the half-life of microbubbles, due to its large relative molecular mass (generally 500,000 to 2 million), the large steric hindrance effect makes it difficult for it to play a synergistic role with the foaming agent to improve the sealing of the hollow nucleus in the microbubbles, resulting in insufficient compression resistance of the microbubbles under high pressure at the bottom of the well, rupture of the foam wall, resulting in an increase in the density of the microbubble drilling fluid and a decrease in the anti-leakage performance.

[0004] The Chinese patent application number 201811166966.7 discloses a foam enhancer for microbubble drilling fluid, which is prepared by copolymerization of vinyl monomers and utilizes the synergistic effect with the foaming agent to enhance the stability and compression resistance of microbubbles under high pressure conditions at the bottom of the well, thereby improving the leakage-proof performance of microbubble drilling fluid. However, its temperature resistance is insufficient and it is difficult to meet the requirements for improving the compression resistance of microbubbles under high temperature conditions of 150°C.

[0005] It can be seen that it is very necessary to develop a foam enhancer for drilling fluid that can work well with the foaming agent and significantly enhance the stability and compression resistance of microbubbles under high temperature and high pressure conditions. Summary of the invention

[0006] In view of this, the object of the present invention is to provide a foam enhancer for high-temperature resistant microbubble drilling fluid and a preparation method and application thereof. The foam enhancer provided by the present invention contains a polymer that can improve the compression resistance of microbubbles under high temperature and high pressure conditions. The polymer has good surface activity and low steric hindrance, can have a good synergistic effect with the foaming agent, can significantly increase the arrangement density of the foaming agent in the microbubble wall and the thickness of the microbubble wall, improve the sealing of the air nucleus in the microbubble, enhance the stability and compression resistance of the microbubble under high temperature and high pressure conditions, prevent air from escaping from the microbubble under high pressure conditions at the bottom of the well, and improve the leakage prevention performance of the microbubble drilling fluid.

[0007] The present invention provides a foam enhancer for high temperature resistant microbubble drilling fluid, wherein the foam enhancer for high temperature resistant microbubble drilling fluid contains a compound of formula (I):

[0008]

[0009] In formula (I), R 1 -COONa or -CONH 2 , R 2 For -C 6 H 4 SO 3 Na, R 3 -CONHC(CH 3 ) 2 CH 2 SO 3 Na or -COOCH(CH 2 CH 3 )CH 2 SO 3 Na, n is an integer between 5 and 20, a:b:c:d=(0.1-0.5):(1-10):(0.1-0.5):(0.1-1);

[0010] The number average molecular weight of the compound of formula (I) is 5,000 to 100,000.

[0011] Preferably, n is an integer between 9 and 15.

[0012] Preferably, the number average molecular weight of the compound of formula (I) is 5,000 to 50,000.

[0013] Preferably, the foam enhancer for high temperature resistant microbubble drilling fluid further contains a liquid phase medium; the solid content of the foam enhancer for high temperature resistant microbubble drilling fluid is 10 to 30 wt%.

[0014] The present invention provides a method for preparing a foam enhancer for high temperature resistant microbubble drilling fluid as described in the above technical solution, comprising the following steps:

[0015] In the presence of an initiator and a relative molecular mass regulator, vinyl monomer A, vinyl monomer B, vinyl monomer C and vinyl monomer D are polymerized in a liquid medium; after a period of reaction, NaOH is added to adjust the pH value of the reaction system to above 7 to obtain a foam enhancer for high temperature resistant microbubble drilling fluid;

[0016] The vinyl monomer A has a structure of formula (i):

[0017]

[0018] The vinyl monomer B has the structure of formula (ii):

[0019]

[0020] The vinyl monomer C has the structure of formula (iii):

[0021]

[0022] The vinyl monomer D has the structure of formula (IV):

[0023]

[0024] In formulas (i) to (iv), R' 1 -COOH or -CONH 2 , R 2 For -C 6 H 4 SO 3 Na, R' 3 -CONHC(CH 3 ) 2 CH 2 SO 3 H or -COOCH(CH 2 CH 3 )CH 2 SO 3 H, n is an integer between 5 and 20;

[0025] The molar ratio of the vinyl monomer A, the vinyl monomer B, the vinyl monomer C and the vinyl monomer D is (0.1-0.5):(1-10):(0.1-0.5):(0.1-1).

[0026] Preferably, the initiator is ammonium persulfate and / or potassium persulfate; the amount of the initiator is 0.5 to 3% of the total mass of vinyl monomer A, vinyl monomer B, vinyl monomer C and vinyl monomer D;

[0027] The relative molecular mass regulator is one or more of hydroquinone, thioglycolic acid, isopropanol, copper sulfate, ferric chloride, dodecyl mercaptan and sodium phosphite; the amount of the relative molecular mass regulator is 0.1-1% of the total mass of vinyl monomer A, vinyl monomer B, vinyl monomer C and vinyl monomer D.

[0028] Preferably, the polymerization reaction temperature is 90-100° C.; the polymerization reaction time is 0.5-1 h.

[0029] Preferably, the pH value is adjusted to 8-10.

[0030] The present invention provides a foaming composition for drilling fluid, comprising a foaming agent and a foam enhancer, wherein the foam enhancer is the foam enhancer for high temperature resistant microbubble drilling fluid described in the above technical scheme or the foam enhancer for high temperature resistant microbubble drilling fluid prepared by the preparation method described in the above technical scheme.

[0031] The present invention provides a drilling fluid, wherein the drilling fluid contains the foam enhancer for high temperature resistant microbubble drilling fluid described in the above technical solution or the foam enhancer for high temperature resistant microbubble drilling fluid prepared by the preparation method described in the above technical solution.

[0032] Compared with the prior art, the present invention provides a foam enhancer for high temperature resistant microbubble drilling fluid and a preparation method and application thereof. The foam enhancer for high temperature resistant microbubble drilling fluid provided by the present invention contains a compound of formula (I); in formula (I), R 1 -COONa or -CONH 2 , R 2 For -C 6 H 4 SO 3 Na, R 3 -CONHC(CH 3 ) 2 CH 2 SO 3 Na or -COOCH(CH 2 CH 3 )CH 2 SO 3Na, n is an integer between 5 and 20, a:b:c:d=(0.1-0.5):(1-10):(0.1-0.5):(0.1-1); the number average molecular weight of the compound of formula (I) is 5,000-100,000. The foam enhancer provided by the present invention contains a polymer that can improve the compression resistance of microbubbles under high temperature and high pressure conditions. The polymer contains rigid groups such as benzene rings and long-chain alkyl sulfonic acids, which can significantly improve the temperature resistance of the foam enhancer; at the same time, the lower relative molecular mass makes the polymer have good surface activity and lower steric hindrance, so that it can have a good synergistic effect with the foaming agent. The foam enhancer provided by the present invention can significantly increase the arrangement density of the foaming agent in the microbubble wall and the thickness of the microbubble wall, improve the sealing of the air nucleus in the microbubble, enhance the stability and compression resistance of the microbubble under high temperature and high pressure conditions, prevent air from escaping from the microbubble under high pressure conditions at the bottom of the well, and improve the leakage prevention performance of the microbubble drilling fluid. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying creative work.

[0034] Figure 1 This is a graph showing the test results of the anti-compression performance of microbubbles provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0035] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0036] The present invention provides a foam enhancer for high temperature resistant micro-bubble drilling fluid, wherein the foam enhancer contains a compound of formula (I):

[0037]

[0038] In formula (I), R 1 -COONa or -CONH 2 , R 2 For -C 6 H 4 SO 3 Na, R 3 -CONHC(CH 3 ) 2CH 2 SO 3 Na or -COOCH(CH 2 CH 3 )CH 2 SO 3 Na, n is an integer between 5 and 20, a:b:c:d=(0.1~0.5):(1~10):(0.1~0.5):(0.1~1).

[0039] In the foam enhancer for high temperature resistant microbubble drilling fluid provided by the present invention, in the compound of formula (I), n can be 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19 or 20, preferably an integer between 9 and 15.

[0040] In the foam enhancer for high temperature resistant microbubble drilling fluid provided by the present invention, in the compound of formula (I), a:b:c:d can be specifically 0.2:4:0.2:0.6, 0.1:8.5:0.3:0.1, 0.5:1:0.1:0.4, 0.5:4:0.2:0.7, 0.4:1:0.1:1, 0.1:10:0.4:0.4 or 0.3:8:0.5:0.1.

[0041] In the foam enhancer for high-temperature resistant microbubble drilling fluid provided by the present invention, the number average molecular weight of the compound of formula (I) is 5,000 to 100,000, specifically 5,000, 10,000, 15,000, 20,000, 25,000, 30,000, 35,000, 40,000, 45,000, 50,000, 55,000, 60,000, 65,000, 70,000, 75,000, 80,000, 85,000, 90,000, 95,000 or 100,000, preferably 5,000 to 50,000.

[0042] In the foam enhancer for high temperature resistant microbubble drilling fluid provided by the present invention, in order to facilitate the addition and use of the foam enhancer in the drilling fluid, the foam enhancer for high temperature resistant microbubble drilling fluid preferably also contains a liquid medium, and the liquid medium includes but is not limited to water; the solid content of the amine inhibitor for drilling fluid is preferably 10 to 30wt%, specifically 10wt%, 11wt%, 12wt%, 13wt%, 14wt%, 15wt%, 16wt%, 17wt%, 18wt%, 19wt%, 20wt%, 21wt%, 22wt%, 23wt%, 24wt%, 25wt%, 26wt%, 27wt%, 28wt%, 29wt% or 30wt%.

[0043] The foam enhancer for high temperature resistant microbubble drilling fluid provided by the present invention contains a polymer that can improve the anti-compression performance of microbubbles under high temperature and high pressure conditions, and the polymer contains rigid groups such as benzene rings and long-chain alkyl sulfonic acids, which can significantly improve the temperature resistance of the foam enhancer; at the same time, the low relative molecular mass makes the polymer have good surface activity and low steric hindrance, so that it can have a good synergistic effect with the foaming agent. The foam enhancer provided by the present invention can significantly increase the arrangement density of the foaming agent in the microbubble wall and the thickness of the microbubble wall, improve the sealing of the air nucleus in the microbubble, enhance the stability and anti-compression of the microbubble under high temperature and high pressure conditions, prevent air from escaping from the microbubble under high pressure conditions at the bottom of the well, and improve the anti-leakage performance of the microbubble drilling fluid.

[0044] The present invention also provides a method for preparing the foam enhancer for high temperature resistant microbubble drilling fluid described in the above technical solution, comprising the following steps:

[0045] In the presence of an initiator and a relative molecular mass regulator, vinyl monomer A, vinyl monomer B, vinyl monomer C and vinyl monomer D are polymerized in a liquid medium; after a period of reaction, NaOH is added to adjust the pH value of the reaction system to above 7 to obtain a foam enhancer for high temperature resistant microbubble drilling fluid;

[0046] The vinyl monomer A has a structure of formula (i):

[0047]

[0048] The vinyl monomer B has the structure of formula (ii):

[0049]

[0050] The vinyl monomer C has the structure of formula (iii):

[0051]

[0052] The vinyl monomer D has the structure of formula (IV):

[0053]

[0054] In formulas (i) to (iv), R 1 -COOH or -CONH 2 , R 2 For -C 6 H 4 SO 3 Na, R 3 -CONHC(CH 3 ) 2 CH 2 SO 3H or -COOCH(CH 2 CH 3 )CH 2 SO 3 H, n is an integer between 5 and 20.

[0055] In the preparation method provided by the present invention, the chemical reaction process involved is specifically as follows:

[0056]

[0057] In the preparation method provided by the present invention, in the vinyl monomer A of the structure of formula (i), the n can be specifically 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19 or 20, preferably an integer between 9 and 15; the vinyl monomer A can more specifically be selected from 2-acrylamidododecanesulfonic acid (i.e., a compound of the structure of formula (i) with n=9), 2-acrylamidotetradecanesulfonic acid (i.e., a compound of the structure of formula (i) with n=11), 2-acrylamidohexadecanesulfonic acid (i.e., a compound of the structure of formula (i) with n=13) or 2-acrylamidooctadecanesulfonic acid (i.e., a compound of the structure of formula (i) with n=15).

[0058] In the preparation method provided by the present invention, the vinyl monomer B is acrylic acid (ie, R' 1 is -COOH) or acrylamide (ie, R' 1 for-CONH 2 The compound of formula (ii)).

[0059] In the preparation method provided by the present invention, the vinyl monomer C is sodium styrene sulfonate (ie, R 2 For -C 6 H 4 SO 3 Na compound of formula (iii)).

[0060] In the preparation method provided by the present invention, the vinyl monomer D is 2-acrylamide-2-methylpropanesulfonic acid (ie, R' 3 -CONHC(CH 3 ) 2 CH 2 SO 3 H of formula (ii)) or 2-acryloyloxybutyl sulfonic acid (ie, R' 3 -COOCH(CH 2 CH 3 )CH 2 SO 3 H of the formula (ii) compound).

[0061] In the preparation method provided by the present invention, the molar ratio of the vinyl monomer A, the vinyl monomer B, the vinyl monomer C and the vinyl monomer D is (0.1-0.5):(1-10):(0.1-0.5):(0.1-1), specifically 0.2:4:0.2:0.6, 0.1:8.5:0.3:0.1, 0.5:1:0.1:0.4, 0.5:4:0.2:0.7, 0.4:1:0.1:1, 0.1:10:0.4:0.4 or 0.3:8:0.5:0.1.

[0062] In the preparation method provided by the present invention, the initiator is preferably ammonium persulfate and / or potassium persulfate; the amount of the initiator is preferably 0.5-3% of the total mass of vinyl monomer A, vinyl monomer B, vinyl monomer C and vinyl monomer D, specifically 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 2%, 2.1%, 2.2%, 2.3%, 2.4%, 2.5%, 2.6%, 2.7%, 2.8%, 2.9% or 3%.

[0063] In the preparation method provided by the present invention, the relative molecular mass regulator is preferably one or more of hydroquinone, thioglycolic acid, isopropanol, copper sulfate, ferric chloride, dodecyl mercaptan and sodium phosphite; the amount of the relative molecular mass regulator is preferably 0.1-1% of the total mass of vinyl monomer A, vinyl monomer B, vinyl monomer C and vinyl monomer D, specifically 0.1%, 0.15%, 0.2%, 0.25%, 0.3%, 0.35%, 0.4%, 0.45%, 0.5%, 0.55%, 0.6%, 0.65%, 0.7%, 0.75%, 0.8%, 0.85%, 0.9%, 0.95% or 1%.

[0064] In the preparation method provided by the present invention, the liquid medium includes but is not limited to water; the amount of the liquid medium is determined according to the solid content of the foam enhancer for the high-temperature resistant microbubble drilling fluid to be prepared, and the solid content is the percentage of the total mass of vinyl monomer A, vinyl monomer B, vinyl monomer C, vinyl monomer D, initiator and relative molecular mass regulator to the total mass of vinyl monomer A, vinyl monomer B, vinyl monomer C, vinyl monomer D, initiator, relative molecular mass regulator and liquid medium.

[0065] In the preparation method provided by the present invention, the temperature of the polymerization reaction is preferably 90-100°C, specifically 90°C, 91°C, 92°C, 93°C, 94°C, 95°C, 96°C, 97°C, 98°C, 99°C or 100°C; the time of the polymerization reaction is preferably 0.5-1h, specifically 0.5h, 0.55h, 0.6h, 0.65h, 0.7h, 0.75h, 0.8h, 0.85h, 0.9h, 0.95h or 1h.

[0066] In the preparation method provided by the present invention, the pH value is preferably adjusted to 8-10, specifically 8, 8.2, 8.5, 8.7, 9, 9.2, 9.5, 9.7 or 10.

[0067] In the preparation method provided by the present invention, the specific process of carrying out the polymerization reaction and pH value adjustment is preferably: first, vinyl monomer A, vinyl monomer B, vinyl monomer C and vinyl monomer D are mixed in a liquid medium to obtain a mixed solution; then the mixed solution and the relative molecular mass regulator are added to the reactor and preheated; then the initiator solution is added to the preheated reactor, and the temperature is raised to the reaction temperature for polymerization reaction; after a period of reaction, NaOH is added to the reaction system for pH adjustment to obtain a foam enhancer for high temperature resistant microbubble drilling fluid with a certain solid content. Wherein, the preheating temperature is preferably 50 to 70°C, specifically 50°C, 52°C, 55°C, 57°C, 60°C, 62°C, 65°C, 67°C or 70°C.

[0068] The present invention also provides a foaming composition for drilling fluid, comprising a foaming agent and a foam enhancer, wherein the foam enhancer is the foam enhancer for high temperature resistant microbubble drilling fluid described in the above technical scheme or the foam enhancer for high temperature resistant microbubble drilling fluid prepared by the preparation method described in the above technical scheme.

[0069] In the foaming composition for drilling fluid provided by the present invention, the foaming agent is preferably sodium fatty alcohol polyoxyethylene ether sulfate (AES) and / or xanthan gum; the mass ratio of the foaming agent to the foam enhancer is preferably 1:(0.1-0.5), specifically 1:0.1, 1:0.15, 1:0.2, 1:0.25, 1:0.3, 1:0.33, 1:0.35, 1:0.4, 1:0.45, 1:0.5.

[0070] The present invention also provides a drilling fluid, which contains the foam enhancer for high temperature resistant microbubble drilling fluid described in the above technical solution or the foam enhancer for high temperature resistant microbubble drilling fluid prepared by the preparation method described in the above technical solution.

[0071] In the drilling fluid provided by the present invention, the drilling fluid also contains a foaming agent; the foaming agent is preferably sodium fatty alcohol polyoxyethylene ether sulfate (AES) and / or xanthan gum; the mass ratio of the foaming agent to the foam enhancer is preferably 1:(0.1-0.5), specifically 1:0.1, 1:0.15, 1:0.2, 1:0.25, 1:0.3, 1:0.33, 1:0.35, 1:0.4, 1:0.45, 1:0.5.

[0072] For the purpose of greater clarity, the present invention is described in detail with reference to the following examples and comparative examples.

[0073] Example 1

[0074] 0.2 mol of 2-acrylamidotetradecanesulfonic acid, 4 mol of acrylic acid, 0.2 mol of sodium styrene sulfonate and 0.6 mol of 2-acrylamido-2-methylpropanesulfonic acid were dissolved in 2020 g of clean water for standby use, 5.23 g of ammonium persulfate was dissolved in 100 g of clean water for standby use, 2.09 g of isopropanol and 2-acrylamidotetradecanesulfonic acid, acrylic acid, sodium styrene sulfonate and 2-acrylamido-2-methylpropanesulfonic acid solution were added to a reaction vessel and heated to 65° C., then the ammonium persulfate solution was added to the reaction system, the system was heated to 95° C. and reacted for 0.5 h, and then the pH value of the solution was adjusted to 9 with NaOH to obtain a foam enhancer for high temperature resistant microbubble drilling fluid with a number average molecular weight of 20,000 and a solid content of 20%, and its structural formula is:

[0075]

[0076] Among them, a:b:c:d=0.2:4:0.2:0.6.

[0077] Example 2

[0078] 0.1 mol of 2-acrylamidooctadecanesulfonic acid, 8.5 mol of acrylic acid, 0.3 mol of sodium styrene sulfonate and 0.1 mol of 2-acryloyloxybutyl sulfonic acid were dissolved in 1668 g of clean water for standby use, 22.05 g of potassium persulfate was dissolved in 100 g of clean water for standby use, 0.73 g of ferric chloride and 2-acrylamidooctadecanesulfonic acid, acrylic acid, sodium styrene sulfonate and 2-acryloyloxybutyl sulfonic acid solution were added to a reaction container and heated to 50° C., then potassium persulfate solution was added to the reaction system, the system was heated to 90° C. for reaction for 1 hour, and then NaOH was used to adjust the pH value of the solution to 8, to obtain a foam enhancer for high temperature resistant microbubble drilling fluid with a number average molecular weight of 50,000 and a solid content of 30%, the structural formula of which is:

[0079]

[0080] Among them, a:b:c:d=0.1:8.5:0.3:0.1.

[0081] Example 3

[0082] 0.5 mol of 2-acrylamidododecanesulfonic acid, 1 mol of acrylamide, 0.1 mol of sodium styrene sulfonate and 0.4 mol of 2-acryloyloxybutyl sulfonic acid were dissolved in 2984 g of clean water for standby use, 5.01 g of ammonium persulfate was dissolved in 100 g of clean water for standby use, 3.34 g of dodecyl mercaptan and 2-acrylamidododecanesulfonic acid, acrylamide, sodium styrene sulfonate and 2-acryloyloxybutyl sulfonic acid solution were added to a reaction vessel and heated to 70° C., then the ammonium persulfate solution was added to the reaction system, the system was heated to 100° C. and reacted for 0.8 h, and then the pH value of the solution was adjusted to 10 with NaOH to obtain a foam enhancer for high temperature resistant microbubble drilling fluid with a number average molecular weight of 5000 and a solid content of 10%, and its structural formula is:

[0083]

[0084] Among them, a:b:c:d=0.5:1:0.1:0.4.

[0085] Embodiments 4 to 7

[0086] The steps are the same as those in Example 1, and the reaction substances and their amounts are shown in Table 1:

[0087] Table 1 Reaction raw materials and dosage

[0088]

[0089] Comparative Example 1

[0090] 10g of dodecyldimethylallyl ammonium chloride is dissolved in 100g of clean water for standby use, 80g of acrylamide and 10g of 2-acrylamido-2-methylpropanesulfonic acid are dissolved in 250g of clean water for standby use; 1g of ammonium persulfate is dissolved in 50g of clean water for standby use; 0.1g of thioglycolic acid and the dodecyldimethylallyl ammonium chloride solution, acrylamide and 2-acrylamido-2-methylpropanesulfonic acid solution are added to a reactor and the temperature is raised to 60°C, then the ammonium persulfate solution is added to the reaction system, the system is heated to 90°C for reaction for 1 hour, and the pH value of the solution is adjusted to 8 with NaOH to obtain a foam enhancer for microbubble drilling fluid with a solid content of 20%.

[0091] Performance Evaluation

[0092] The performance of the foam enhancers synthesized in Examples 1 to 7 and Comparative Example 1 was evaluated, and the specific evaluation contents are as follows:

[0093] (1) Influence on the foaming ability and foam stability of the foaming agent

[0094] 1.0 g of a foaming agent, sodium fatty alcohol polyoxyethylene ether sulfate (AES) and 0.3 g of a foam enhancer (the foam enhancer samples synthesized in Examples 1 to 7 and Comparative Example 1, respectively) were added to 100 mL of water, and then stirred at high speed for 5 min at a high speed of 10,000 r / min with a high-speed stirrer. The foam slurry was poured into a measuring cylinder, and the volume of the foam was recorded. The time taken for the foam system to precipitate 50 mL of the foaming base liquid was recorded as the foam half-life. The experimental results are shown in Table 2:

[0095] Table 2 Foam enhancer performance evaluation

[0096]

[0097] (2) Evaluation of microbubble anti-compression performance

[0098] Add 2.5g of foam enhancer (the foam enhancer samples synthesized in Example 2, Example 4 and Comparative Example 1, respectively), 5g of foaming agent sodium fatty alcohol polyoxyethylene ether sulfate (AES) and 2.5g of xanthan gum to 500g of clean water, mix the treatment agent evenly with a stirrer, and then roll age at 150°C for 6h. Stir the aged liquid at 600 rpm for 10min to obtain a density of 0.82g / cm 3 The microbubble system was prepared and the effect of pressure change on the density of the system at 150°C was investigated using a PVT fluid tester. In order to better compare the effects, a control group without adding foam enhancer was set up during the experiment.

[0099] The experimental results are as follows Figure 1 As shown, Figure 1 This is a graph showing the test results of the microbubble compression resistance provided by an embodiment of the present invention. Figure 1 It can be seen that the foam enhancer synthesized in the present invention has good temperature resistance and can significantly improve the compression resistance of microbubbles at a high temperature of 150° C., which is beneficial to enhancing the leakage-proof performance of microbubble drilling fluid at high temperatures.

[0100] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A foam enhancer for high temperature resistant micro-bubble drilling fluid, It is characterized in that The foam enhancer for high temperature resistant micro-bubble drilling fluid contains a compound having a structure of formula (I): In formula (I), R 1 -COONa or -CONH 2 , R 2 For -C 6 H 4 SO 3 Na, R 3 -CONHC(CH 3 ) 2 CH 2 SO 3 Na or -COOCH(CH 2 CH 3 )CH 2 SO 3 Na, n is an integer between 5 and 20, a:b:c:d=(0.1-0.5):(1-10):(0.1-0.5):(0.1-1); The number average molecular weight of the compound of formula (I) is 5,000 to 100,000.

2. The foam enhancer for high temperature resistant microbubble drilling fluid according to claim 1, It is characterized in that The n is an integer between 9 and 15.

3. The foam enhancer for high temperature resistant microbubble drilling fluid according to claim 1, It is characterized in that The number average molecular weight of the compound of formula (I) is 5,000 to 50,000.

4. The foam enhancer for high temperature resistant microbubble drilling fluid according to claim 1, It is characterized in that The foam enhancer for high temperature resistant microbubble drilling fluid also contains a liquid phase medium; the solid content of the foam enhancer for high temperature resistant microbubble drilling fluid is 10-30wt%.

5. A method for preparing the foam enhancer for high temperature resistant microbubble drilling fluid according to any one of claims 1 to 4, It is characterized in that The following steps are involved: In the presence of an initiator and a relative molecular mass regulator, vinyl monomer A, vinyl monomer B, vinyl monomer C and vinyl monomer D are polymerized in a liquid medium; after a period of reaction, NaOH is added to adjust the pH value of the reaction system to above 7 to obtain a foam enhancer for high temperature resistant microbubble drilling fluid; The vinyl monomer A has a structure of formula (i): The vinyl monomer B has the structure of formula (ii): The vinyl monomer C has the structure of formula (iii): The vinyl monomer D has the structure of formula (IV): In formulas (i) to (iv), R' 1 -COOH or -CONH 2 , R 2 For -C 6 H 4 SO 3 Na, R' 3 -CONHC(CH 3 ) 2 CH 2 SO 3 H or -COOCH(CH 2 CH 3 )CH 2 SO 3 H, n is an integer between 5 and 20; The molar ratio of the vinyl monomer A, the vinyl monomer B, the vinyl monomer C and the vinyl monomer D is (0.1-0.5):(1-10):(0.1-0.5):(0.1-1).

6. The preparation method according to claim 5, It is characterized in that The initiator is ammonium persulfate and / or potassium persulfate; the amount of the initiator is 0.5-3% of the total mass of vinyl monomer A, vinyl monomer B, vinyl monomer C and vinyl monomer D; The relative molecular mass regulator is one or more of hydroquinone, thioglycolic acid, isopropanol, copper sulfate, ferric chloride, dodecyl mercaptan and sodium phosphite; the amount of the relative molecular mass regulator is 0.1-1% of the total mass of vinyl monomer A, vinyl monomer B, vinyl monomer C and vinyl monomer D.

7. The preparation method according to claim 5, It is characterized in that The polymerization reaction temperature is 90-100° C.; the polymerization reaction time is 0.5-1 h.

8. The preparation method according to claim 5, It is characterized in that The pH value is adjusted to 8-10.

9. A foaming composition for drilling fluid, It is characterized in that The invention comprises a foaming agent and a foam enhancer, wherein the foam enhancer is the foam enhancer for high temperature resistant microbubble drilling fluid as described in any one of claims 1 to 4 or the foam enhancer for high temperature resistant microbubble drilling fluid prepared by the preparation method as described in any one of claims 5 to 8.

10. A drilling fluid, It is characterized in that The drilling fluid contains the foam enhancer for high temperature resistant microbubble drilling fluid according to any one of claims 1 to 4 or the foam enhancer for high temperature resistant microbubble drilling fluid prepared by the preparation method according to any one of claims 5 to 8.

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