Disclosure of Invention
Aiming at the defects of the prior art, the invention provides a salt-resistant and temperature-resistant starch microsphere as well as a preparation method and application thereof.
The first aspect of the invention provides a starch microsphere, which comprises the following raw materials in parts by weight: 100 parts of deionized water, 1-20 parts of starch, 10-55 parts of triethanolamine, 0.105-14.6 parts of epoxy chloropropane, 0.1-20 parts of zwitterionic monomer, 0.001-0.2 part of initiator, 0.05-10 parts of zwitterionic surfactant, 200-750 parts of alkane compound, 10-250 parts of emulsifier and 0.5-200 parts of inorganic salt solution, wherein the inorganic salt solute accounts for 0.025-50 parts and the organic solvent accounts for 200-750 parts.
In the starch microspheres, the zwitterionic starch microspheres comprise the following raw materials in parts by weight: 100 parts of deionized water, 5-15 parts of starch, 20-35 parts of triethanolamine, 1.04-7.8 parts of epoxy chloropropane, 5-15 parts of zwitterionic monomer, 0.02-0.1 part of initiator, 1-5 parts of zwitterionic surfactant, 250-450 parts of alkane compound, 30-100 parts of emulsifier and 50-150 parts of inorganic salt solution, wherein the inorganic salt solute accounts for 0.5-30 parts and the organic solvent accounts for 250-450 parts.
In the starch microspheres, the controllable range of the particle size of the starch microspheres is 0.1-500 μm, the particle size of the starch microspheres is uniformly distributed in a particle size concentrated distribution interval (wherein the particle size concentrated distribution interval is defined as a continuous interval in which the proportion of the particle size distribution is greater than or equal to 90% except for the particle size boundaries at two ends, and the particle size concentrated distribution interval is an area in which the particle size distribution is approximately linearly distributed and does not include areas with obvious inflection points at two ends), and the particle size distribution in the particle size concentrated distribution interval has the following characteristics: evenly dividing the particle size concentrated distribution interval into n intervals, wherein the ratio of the microspheres in each interval is as follows:
wherein n is an integer greater than 1.
In the starch microspheres, the starch is one or more of mung bean starch, cassava starch, sweet potato starch, wheat starch, water caltrop starch, lotus root starch and corn starch, and preferably corn starch and/or potato starch.
In the starch microspheres, the starch is one or more of mung bean starch, cassava starch, sweet potato starch, wheat starch, water caltrop starch, lotus root starch and corn starch, and preferably corn starch and/or potato starch.
In the starch microsphere, the zwitterionic monomer can be one or more of DMAPS (methacryloyloxyethyl-N, N-dimethyl propane sulfonate), DAPS (N, N-dimethyl allyl amine propane sulfonate), VPPS (4-vinylpyridine propane sulfonate), MAPS (N-methyl diallyl propane sulfonate) and MABS (N-methyl diallyl butane sulfonate).
In the starch microsphere, the initiator can be one or more of potassium persulfate, sodium persulfate and ammonium persulfate.
In the starch microsphere, the structure of the zwitterionic surfactant is as follows:
wherein: n is an integer between 2 and 6, preferably n is 3 or 4; r is a carbon chain having 1 to 18 carbon atoms, preferably 12 to 18 carbon atoms. The carbon chain is a saturated carbon chain and can be a straight chain or a branched chain. The carbon chain (excluding the terminal carbon) may contain substituted hydroxyl, amino or carboxyl groups, and the same carbon may be monosubstituted. The zwitterionic surfactant can be one or more of dimethyl dodecyl sulfopropyl ammonium salt, dimethyl hexadecyl sulfoethyl ammonium salt, dimethyl octadecyl sulfobutyl ammonium salt, dimethyl (3-hydroxyl dodecyl) sulfopropyl ammonium salt and dimethyl (6-amino tetradecyl) sulfoethyl ammonium salt.
In the starch microspheres, the alkane compound is saturated alkane, and may be alkane and/or cycloalkane, and the alkane and cycloalkane may be halogenated alkane, and specifically may be one or more of n-hexane, n-heptane, n-octane, n-decane, n-dodecane, isohexane, isoheptane, isooctane, isodecane, isododecane, cyclopentane, cyclohexane, cycloheptane, cyclooctane, trichloromethane, chloropentane, chlorohexane, chlorooctane, and chlorododecane.
In the starch microspheres, the emulsifier can be an anionic surfactant, specifically one or more of sodium dodecyl benzene sulfonate, sodium hexadecylbenzene sulfonate, sodium dodecyl benzene sulfate and sodium hexadecylbenzene sulfate; the surfactant can also be nonionic surfactant, and specifically comprises one or more of Span20, Span40, Span60, Span80, Tween20, Tween40, Tween60 and Tween 80.
In the starch microspheres, the inorganic salt is a soluble inorganic salt, the inorganic salt is one or more of sodium salt, potassium salt, ammonium salt, calcium salt and magnesium salt, and when the inorganic salt is sodium salt, the inorganic salt is specifically one or more of sodium chloride, sodium bromide, sodium sulfate, sodium sulfite, sodium carbonate, sodium bicarbonate, sodium nitrate, sodium phosphate, sodium hydrogen phosphate and sodium silicate; when the inorganic salt is potassium salt, the inorganic salt is one or more of potassium chloride, potassium bromide, potassium sulfate, potassium sulfite, potassium carbonate, potassium bicarbonate, potassium nitrate, potassium phosphate, potassium hydrogen phosphate and potassium silicate; when the inorganic salt is ammonium salt, the inorganic salt is one or more of ammonium chloride, ammonium bromide and ammonium nitrate; when the inorganic salt is a calcium salt, it is specifically calcium chloride or calcium bromide; when the inorganic salt is a magnesium salt, the inorganic salt is specifically one or more of magnesium chloride, magnesium bromide, magnesium sulfate and magnesium nitrate.
In the starch microspheres, the organic solvent is one or more of absolute ethyl alcohol, 1-butanol, ethyl acetate, butyl acetate, acetone, xylene, n-hexane and carbon tetrachloride, and ethyl acetate and/or absolute ethyl alcohol are preferred.
The second aspect of the present invention provides a preparation method of the above starch microsphere, which comprises the following steps:
(1) weighing a certain amount of starch, adding the starch into water, adding a certain amount of triethanolamine, uniformly mixing at 20-80 ℃, and adding epoxy chloropropane for reaction;
(2) adding a zwitterionic monomer into the feed liquid obtained in the step (1), fully dissolving and mixing, and then adding an initiator for reaction;
(3) adding a zwitterionic surfactant into the feed liquid obtained in the step (2), and uniformly mixing to obtain a water phase A;
(4) weighing a certain amount of alkane compounds, adding an emulsifier, and uniformly mixing until the alkane compounds are completely dissolved to obtain an oil phase B;
(5) and (3) uniformly mixing the water phase A obtained in the step (3) and the oil phase B obtained in the step (4) at the temperature of 30-60 ℃, slowly and uniformly adding an inorganic salt solution and epoxy chloropropane into the mixed solution, continuing to react after the inorganic salt solution and the epoxy chloropropane are added, demulsifying and removing the upper oil phase after the reaction is finished, and washing and drying to obtain the microsphere.
In the method, the amounts of the deionized water, the starch, the triethanolamine, the epichlorohydrin, the zwitterionic monomer, the initiator, the zwitterionic surfactant, the alkane compound, the emulsifier, the inorganic salt solution and the organic solvent are respectively as follows: 100 parts of deionized water, 1-20 parts of starch, 10-55 parts of triethanolamine, 0.105-14.6 parts of epoxy chloropropane, 0.1-20 parts of zwitterionic monomer, 0.001-0.2 part of initiator, 200-750 parts of alkane compound, 10-250 parts of emulsifier, 0.05-10 parts of zwitterionic surfactant and 0.5-200 parts of inorganic salt solution, wherein the inorganic salt solute accounts for 0.025-50 parts and the organic solvent accounts for 200-750 parts; preferably 100 parts of deionized water, 5-15 parts of starch, 20-35 parts of triethanolamine, 1.04-7.8 parts of epoxy chloropropane, 5-15 parts of zwitterionic monomer, 0.02-0.1 part of initiator, 250-450 parts of alkane compound, 30-100 parts of emulsifier, 1-5 parts of zwitterionic surfactant and 50-150 parts of inorganic salt solution, wherein the inorganic salt solute accounts for 0.5-30 parts and the solvent accounts for 250-450 parts.
In the method, the starch in the step (1) is one or more of mung bean starch, cassava starch, sweet potato starch, wheat starch, water chestnut starch, lotus root starch and corn starch, and preferably corn starch and/or potato starch.
In the method, the reaction temperature in the step (1) is 30-60 ℃; the reaction time is 0.5-4 h, preferably 1-3 h.
In the method, the reaction temperature in the step (2) is 60-80 ℃, and the reaction time is 3-6 h.
In the method of the present invention, the zwitterionic monomer in step (2) may be one or more of DMAPS (methacryloyloxyethyl-N, N-dimethylpropanesulfonate), DAPS (N, N-dimethylallylamine propanesulfonate), VPPS (4-vinylpyridine propanesulfonate), MAPS (N-methyldiallylpropyl propanesulfonate), and MABS (N-methyldiallylbutylsulfonate).
In the method of the present invention, the initiator in step (2) may be one or more of potassium persulfate, sodium persulfate, and ammonium persulfate.
In the method of the present invention, step (3) isThe structure of the zwitterionic surfactant is as follows:
wherein: n is an integer between 2 and 6, preferably n is 3 or 4; r is a carbon chain having 1 to 18 carbon atoms, preferably 12 to 18 carbon atoms. The carbon chain is a saturated carbon chain and can be a straight chain or a branched chain. The carbon chain (excluding the terminal carbon) may contain substituted hydroxyl, amino or carboxyl groups, and the same carbon may be monosubstituted. The zwitterionic surfactant can be one or more of dimethyl dodecyl sulfopropyl ammonium salt, dimethyl hexadecyl sulfoethyl ammonium salt, dimethyl octadecyl sulfobutyl ammonium salt, dimethyl (3-hydroxyl dodecyl) sulfopropyl ammonium salt and dimethyl (6-amino tetradecyl) sulfoethyl ammonium salt.
In the method of the present invention, the alkane compound in step (4) is a saturated alkane, and may be an alkane and/or a cycloalkane, and the alkane and cycloalkane may be a halogenated alkane, and specifically may be one or more of n-hexane, n-heptane, n-octane, n-decane, n-dodecane, isohexane, isoheptane, isooctane, isodecane, isododecane, cyclopentane, cyclohexane, cycloheptane, cyclooctane, trichloromethane, chloropentane, chlorohexane, chlorooctane, and chlorododecane.
In the method of the invention, the emulsifier in the step (4) can be an anionic surfactant, specifically one or more of sodium dodecyl benzene sulfonate, sodium hexadecylbenzene sulfonate, sodium dodecyl benzene sulfate and sodium hexadecylbenzene sulfate; the surfactant can also be nonionic surfactant, and specifically comprises one or more of Span20, Span40, Span60, Span80, Tween20, Tween40, Tween60 and Tween 80.
In the method, the inorganic salt in the step (5) is soluble inorganic salt, the inorganic salt is one or more of sodium salt, potassium salt, ammonium salt, calcium salt and magnesium salt, and when the inorganic salt is sodium salt, the inorganic salt is specifically one or more of sodium chloride, sodium bromide, sodium sulfate, sodium sulfite, sodium carbonate, sodium bicarbonate, sodium nitrate, sodium phosphate, sodium hydrogen phosphate and sodium silicate; when the inorganic salt is potassium salt, the inorganic salt is one or more of potassium chloride, potassium bromide, potassium sulfate, potassium sulfite, potassium carbonate, potassium bicarbonate, potassium nitrate, potassium phosphate, potassium hydrogen phosphate and potassium silicate; when the inorganic salt is ammonium salt, the inorganic salt is one or more of ammonium chloride, ammonium bromide and ammonium nitrate; when the inorganic salt is a calcium salt, it is specifically calcium chloride or calcium bromide; when the inorganic salt is a magnesium salt, the inorganic salt is specifically one or more of magnesium chloride, magnesium bromide, magnesium sulfate and magnesium nitrate.
In the method of the present invention, the slow and uniform adding in step (5) may be any method capable of realizing uniform solvent adding in the field, such as a dropwise adding method.
In the method of the present invention, the demulsification in step (5) may be performed by any means available in the art, such as mechanical stirring or adding an organic solvent, preferably by adding an organic solvent. The washing described in step (5) is washing with an organic solvent, the washing operation being well known to the person skilled in the art. In the method of the present invention, the demulsification and washing processes in the step (5) are performed by using the same or different organic solvents, and preferably by using the same organic solvent. The organic solvent is one or more of absolute ethyl alcohol, 1-butanol, ethyl acetate, butyl acetate, acetone, xylene, n-hexane and carbon tetrachloride, and ethyl acetate and/or absolute ethyl alcohol are/is preferred.
In the method, the drying in the step (5) is carried out for 12-24 hours at the temperature of 55-95 ℃.
The third aspect of the invention also provides application of the starch microspheres in a temporary plugging agent for protecting an oil-gas reservoir. The starch microspheres are used as a component in a drilling fluid system to play a role in shielding and temporary plugging. The addition amount of 0.5-5 wt% can achieve good effect. The drilling fluid added with the microspheres has good plugging capability, can effectively plug pores or microcracks to form compact mud cakes, prevents a large amount of filtrate from permeating into a stratum, and reduces the filtration loss.
Compared with the prior art, the starch microsphere and the preparation method thereof have the following advantages:
1. the starch microspheres of the invention are polydisperse microspheres with uniformly distributed particle sizes, which are different from monodisperse and polydisperse starch microspheres prepared by the prior art. When the starch microspheres are applied to the field of temporary plugging agents for protecting oil and gas reservoirs, due to the fact that geological structures are different, the porosity span of the reservoirs is large, and if the microspheres with monodisperse particle sizes are used, the requirement on broad spectrum is difficult to meet, and the using effect cannot meet the industrial requirement. In addition, the existing polydisperse microspheres are normally distributed, the effective range of the particle size is narrow, and the effect is obviously limited. The uniformly distributed polydisperse starch microspheres provided by the technology can well solve the problems, namely, in any particle size interval, the microspheres have equivalent proportion, high microsphere content and obvious temporary plugging effect, and can meet the requirement of broad spectrum.
2. In the preparation method of the starch microspheres, the structures of the straight chain part and the branched chain part in the starch are equivalent in size and have similar molecular sizes by the combined action of the triethanolamine and the epoxy chloropropane, particularly the operation mode of respectively adding the epoxy chloropropane in two steps, so that the prepared microspheres are easier to control, and the particle size distribution is uniform. Then in the process of crosslinking starch into microspheres later, by using a zwitterionic surfactant and simultaneously slowly adding inorganic salt and epoxy chloropropane at a constant speed, under the combined action of the zwitterionic surfactant and the inorganic salt and the epoxy chloropropane, the particle size of the prepared starch microspheres is linearly changed, and then the poly-dispersed starch microspheres with uniformly distributed particle sizes are prepared.
3. The starch microspheres are prepared by adopting an inverse emulsion polymerization method, and starch monomers are uniformly suspended in a continuous phase under the action of mechanical stirring and a zwitterionic surfactant to complete polymerization. The reaction process has the advantages of low material viscosity and easy heat transfer and control of the reaction, and pure and uniform micron-sized microsphere products can be obtained only by simple separation, cleaning and drying after polymerization, thereby being beneficial to the amplification production and industrial application of the technology.
4. In the preparation method of the zwitterionic starch microspheres, due to the addition of the zwitterionic monomer, the salt resistance, temperature resistance and other properties of the microspheres are remarkably improved.
example 8
3.5 parts of corn starch are weighed into 100 parts of water, 12 parts of triethanolamine are added, and the mixture is fully dissolved at 45 ℃. Then 0.09 part of epoxy chloropropane is added, and the mixture is mixed and reacted for 2.25 hours. 1.5 parts DMAPS was weighed into the starch solution and mixed well. 0.015 part (sodium persulfate: ammonium persulfate =2: 1) was added at 67.5 ℃ and reacted for 5.25 hours. 4.5 parts of dimethyldodecylsulfopropyl ammonium salt is added, and the obtained feed liquid is the water phase A after full mixing. And adding 40 parts of emulsifier (sodium dodecyl benzene sulfonate: sodium dodecyl benzene sulfate =3: 1) into 250 parts of alkane compound (n-heptane: cyclohexane =1: 4), and stirring at high speed to completely dissolve the mixture, wherein the obtained feed liquid is the oil phase B. Slowly pouring A into B at 40 ℃, and weighing 4 parts of Na2CO3Preparing 67.5 parts of inorganic salt solution, simultaneously dripping 1.5 parts of epichlorohydrin into the starch solution at the same temperature, dripping at a constant speed for 6 hours, and continuously reacting for 2 hours after finishing dripping. And then stopping the reaction, adding 75 parts of absolute ethyl alcohol as an organic solvent into the mixed phase for demulsification, filtering out an upper oil phase, washing the microspheres by 175 parts of absolute ethyl alcohol, and finally drying at the constant temperature of 77 ℃ for 18 hours to obtain white powdery microspheres. The concentrated particle size distribution interval of the starch microspheres is 1-19 microns (92.8% of particle sizes are in the interval), and the particle size distribution in the concentrated particle size distribution interval has the following characteristics: (1 μm-4 μm): 16.6 percent; (4 μm-7 μm): 16.3 percent; (7 μm-10 μm): 17.2 percent; (10 μm-13 μm): 15.1 percent; (13 μm-16 μm): 17.4 percent; (16 μm-19 μm): 17.4 percent.
Comparative example 1 (use of conventional surfactant only)
5 parts of potato starch are weighed into 100 parts of deionized water and fully dissolved for 30min at room temperature. 3.5 parts of MAPS were weighed into the starch solution and mixed thoroughly. 0.06 part of ammonium persulfate was added at 70 ℃ and reacted for 4 hours. Adding 3 parts of sodium dodecyl sulfate, and fully mixing to obtain a feed liquid, namely the water phase A. And adding 30 parts of emulsifier (Span 40: Tween60=2: 3) into 250 parts of n-octane, and stirring at high speed to completely dissolve the n-octane to obtain a feed liquid, namely the oil phase B. Slowly pouring the A into the B at 60 ℃, adding 1 part of epoxy chloropropane into the mixed phase at the same temperature, reacting for 10h, and stopping the reaction. Adding 100 parts of carbon tetrachloride as an organic solvent into the mixed phase for demulsification, filtering an upper oil phase, washing the microspheres with 150 parts of carbon tetrachloride, and finally drying at the constant temperature of 55 ℃ for 24 hours to obtain white powdery microspheres. The starch microspheres have a particle size concentration distribution interval of 75-300 microns (92.2% of particle sizes are in the interval), and the particle size distribution in the particle size concentration distribution interval has the following characteristics: (75 μm-150 μm): 19.4 percent; (150 μm-225 μm): 59.8 percent; (225 μm-300 μm): 20.8 percent.
COMPARATIVE EXAMPLE 2 (Triethanolamine, D-SALT)
Weighing 5 parts of potato starch, adding the potato starch into 100 parts of deionized water, adding 20 parts of triethanolamine, and fully dissolving for 30min at room temperature. 3.5 parts of MAPS were weighed into the starch solution and mixed thoroughly. 0.06 part of ammonium persulfate was added at 70 ℃ and reacted for 4 hours. Adding 3 parts of dimethyl hexadecyl sulfoethyl ammonium salt, and fully mixing to obtain a feed liquid, namely the water phase A. And adding 30 parts of emulsifier (Span 40: Tween60=2: 3) into 250 parts of n-octane, and stirring at high speed to completely dissolve the n-octane to obtain a feed liquid, namely the oil phase B. Slowly pouring A into B at 60 ℃, and weighing 0.5 part of CaCl2Preparing 20 parts of inorganic salt solution, simultaneously dropwise adding the inorganic salt solution and 1 part of epoxy chloropropane into the mixed phase at the same temperature, uniformly dropwise adding for 8 hours, and continuously reacting for 2 hours after dropwise adding. And then stopping the reaction, adding 100 parts of carbon tetrachloride as an organic solvent into the mixed phase for demulsification, filtering an upper oil phase, washing the microspheres with 150 parts of carbon tetrachloride, and finally drying at the constant temperature of 55 ℃ for 24 hours to obtain white powdery microspheres. The starch microspheres have a particle size concentration distribution interval of 30-250 micrometers (91.9% of particle sizes are in the interval), and the particle size distribution in the particle size concentration distribution interval has the following characteristics: (30 μm-85 μm): 22.1 percent; (85 μm-140 μm): 27.5 percent; (140 μm-195 μm): 18.2 percent; (195 μm-250 μm): 32.2 percent.
Comparative example 3 (Triethanolamine, micro-crosslinking)
Weighing 5 parts of potato starch, adding the potato starch into 100 parts of deionized water, adding 20 parts of triethanolamine, and fully dissolving for 30min at room temperature. Then 0.04 part of epoxy chloropropane is added, and the mixture is mixed and reacted for 2 hours. 3.5 parts of MAPS were weighed into the starch solution and mixed thoroughly. 0.06 part of ammonium persulfate was added at 70 ℃ and reacted for 4 hours. Adding 3 parts of dimethyl hexadecyl sulfoethyl ammonium salt, and fully mixing to obtain a feed liquid, namely the water phase A. And adding 30 parts of emulsifier (Span 40: Tween60=2: 3) into 250 parts of n-octane, and stirring at high speed to completely dissolve the n-octane to obtain a feed liquid, namely the oil phase B. Slowly pouring the A into the B at 60 ℃, adding 1 part of epoxy chloropropane into the mixed phase at the same temperature, reacting for 10h, and stopping the reaction. Adding 100 parts of carbon tetrachloride as an organic solvent into the mixed phase for demulsification, filtering an upper oil phase, washing the microspheres with 150 parts of carbon tetrachloride, and finally drying at the constant temperature of 55 ℃ for 24 hours to obtain white powdery microspheres. The starch microspheres have a particle size concentration distribution interval of 10-150 microns (94.8% of particle sizes are in the interval), and the particle size distribution in the particle size concentration distribution interval has the following characteristics: (10 μm-45 μm): 19.6 percent; (45 μm-80 μm): 21.2 percent; (80 μm-115 μm): 27.5 percent; (115 μm-150 μm): 31.7 percent.
Comparative example 4 (micro-crosslinking, dropwise addition of salt)
5 parts of potato starch are weighed into 100 parts of deionized water and fully dissolved for 30min at room temperature. Then 0.04 part of epoxy chloropropane is added, and the mixture is mixed and reacted for 2 hours. 3.5 parts of MAPS were weighed into the starch solution and mixed thoroughly. 0.06 part of ammonium persulfate was added at 70 ℃ and reacted for 4 hours. Adding 3 parts of dimethyl hexadecyl sulfoethyl ammonium salt, and fully mixing to obtain a feed liquid, namely the water phase A. And adding 30 parts of emulsifier (Span 40: Tween60=2: 3) into 250 parts of n-octane, and stirring at high speed to completely dissolve the n-octane to obtain a feed liquid, namely the oil phase B. Slowly pouring A into B at 60 ℃, and weighing 0.5 part of CaCl2Preparing 20 parts of inorganic salt solution, simultaneously dripping the inorganic salt solution and 1 part of epichlorohydrin into the starch solution at the same temperature, dripping the solution at a constant speed for 8 hours, and continuously reacting for 2 hours after the dripping is finished. And then stopping the reaction, adding 100 parts of carbon tetrachloride as an organic solvent into the mixed phase for demulsification, filtering an upper oil phase, washing the microspheres with 150 parts of carbon tetrachloride, and finally drying at the constant temperature of 55 ℃ for 24 hours to obtain white powdery microspheres. The particle size concentrated distribution range of the starch microspheres is 15 to215 μm (93.0% of the particle size in this interval), the particle size distribution in the particle size distribution interval being characterized by: (15 μm-65 μm): 37.2 percent; (65 μm-115 μm): 19.7 percent; (115 μm-165 μm): 21.1 percent; (165 μm-215 μm): 22 percent.
Evaluation of application of starch microspheres containing zwitterionic monomers as temporary plugging agents- -sand bed plugging experiments, samples prepared in examples and comparative examples were selected for evaluation. An experimental instrument: a drilling fluid sand bed filtration loss instrument, a stirrer and an oven. Experimental materials: log 860 well slurry (density 1.19 g/cm)3) Examples, comparative examples and 20-40 mesh sand samples.
The experimental steps are as follows:
1. slurry preparation: formulated slurry +3% of example sample or comparative sample.
2. Manufacturing a sand bed: adding 20-40 mesh sand into the cylinder by 350cm3Shaking up;
3. adding prepared experimental slurry (400-500 mL), fixing on an instrument frame and sealing an upper channel and a lower channel;
4. and opening an air source, adjusting the pressure to 0.69mPa, simultaneously opening an upper switch and a lower switch, and measuring the condition that the drilling fluid invades the sand bed in the half-hour process.
The experimental results are as follows:
the filtrate loss FL is 30min after the formula is added1And the drilling fluid is basically stable after invading the sand bed to the depth D. After a stable mud cake is formed, the pressure is released, the drilling fluid is poured out, clear water is added to the position of 400mL, and the filtration loss FL after 30min of pressurization (0.69 mPa) measurement is carried out2The experimental results are shown in table 1:
TABLE 1 results of the experiment
Sample (I)
|
Example 1
|
Example 2
|
Example 3
|
Example 4
|
Example 5
|
Example 6
|
Example 7
|
Example 8
|
Comparative example 1
|
Comparative example 2
|
Comparative example 3
|
Comparative example 4
|
Filtration loss FL1/ml
|
0
|
0
|
0
|
0
|
0
|
0
|
0
|
0
|
5
|
3
|
0
|
0
|
Depth D/cm3 |
175
|
185
|
160
|
175
|
215
|
170
|
190
|
205
|
350
|
350
|
325
|
310
|
Filtration loss FL2/ml
|
0
|
0
|
0
|
0
|
0
|
0
|
0
|
0
|
65
|
53
|
42
|
33 |
The experimental results are as follows:
from the above results, it can be seen that the clear water shows good plugging effect without filtration loss at 0.69mPa pressure for 30min when the samples of examples 1-5 are used, while the clear water shows poor plugging effect with filtration loss of 65ml at 0.69mPa pressure for 30min when the samples of comparative examples 1-4 are used.