CN113528102A - Completely degradable plugging agent for drilling fluid and preparation method thereof - Google Patents
Completely degradable plugging agent for drilling fluid and preparation method thereof Download PDFInfo
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- CN113528102A CN113528102A CN202010302795.7A CN202010302795A CN113528102A CN 113528102 A CN113528102 A CN 113528102A CN 202010302795 A CN202010302795 A CN 202010302795A CN 113528102 A CN113528102 A CN 113528102A
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- C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
- C09K8/00—Compositions for drilling of boreholes or wells; Compositions for treating boreholes or wells, e.g. for completion or for remedial operations
- C09K8/50—Compositions for plastering borehole walls, i.e. compositions for temporary consolidation of borehole walls
- C09K8/504—Compositions based on water or polar solvents
- C09K8/506—Compositions based on water or polar solvents containing organic compounds
- C09K8/508—Compositions based on water or polar solvents containing organic compounds macromolecular compounds
- C09K8/5086—Compositions based on water or polar solvents containing organic compounds macromolecular compounds obtained otherwise than by reactions only involving carbon-to-carbon unsaturated bonds
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- C08J3/12—Powdering or granulating
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- C09K8/00—Compositions for drilling of boreholes or wells; Compositions for treating boreholes or wells, e.g. for completion or for remedial operations
- C09K8/02—Well-drilling compositions
- C09K8/03—Specific additives for general use in well-drilling compositions
- C09K8/035—Organic additives
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- C09K8/00—Compositions for drilling of boreholes or wells; Compositions for treating boreholes or wells, e.g. for completion or for remedial operations
- C09K8/50—Compositions for plastering borehole walls, i.e. compositions for temporary consolidation of borehole walls
- C09K8/516—Compositions for plastering borehole walls, i.e. compositions for temporary consolidation of borehole walls characterised by their form or by the form of their components, e.g. encapsulated material
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- C09K8/00—Compositions for drilling of boreholes or wells; Compositions for treating boreholes or wells, e.g. for completion or for remedial operations
- C09K8/60—Compositions for stimulating production by acting on the underground formation
- C09K8/84—Compositions based on water or polar solvents
- C09K8/86—Compositions based on water or polar solvents containing organic compounds
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- C09K8/00—Compositions for drilling of boreholes or wells; Compositions for treating boreholes or wells, e.g. for completion or for remedial operations
- C09K8/60—Compositions for stimulating production by acting on the underground formation
- C09K8/92—Compositions for stimulating production by acting on the underground formation characterised by their form or by the form of their components, e.g. encapsulated material
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- D01—NATURAL OR MAN-MADE THREADS OR FIBRES; SPINNING
- D01F—CHEMICAL FEATURES IN THE MANUFACTURE OF ARTIFICIAL FILAMENTS, THREADS, FIBRES, BRISTLES OR RIBBONS; APPARATUS SPECIALLY ADAPTED FOR THE MANUFACTURE OF CARBON FILAMENTS
- D01F6/00—Monocomponent artificial filaments or the like of synthetic polymers; Manufacture thereof
- D01F6/58—Monocomponent artificial filaments or the like of synthetic polymers; Manufacture thereof from homopolycondensation products
- D01F6/62—Monocomponent artificial filaments or the like of synthetic polymers; Manufacture thereof from homopolycondensation products from polyesters
- D01F6/625—Monocomponent artificial filaments or the like of synthetic polymers; Manufacture thereof from homopolycondensation products from polyesters derived from hydroxy-carboxylic acids, e.g. lactones
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- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
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- C08J2367/00—Characterised by the use of polyesters obtained by reactions forming a carboxylic ester link in the main chain; Derivatives of such polymers
- C08J2367/04—Polyesters derived from hydroxy carboxylic acids, e.g. lactones
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- C09K2208/00—Aspects relating to compositions of drilling or well treatment fluids
- C09K2208/08—Fiber-containing well treatment fluids
Abstract
The invention relates to a completely degradable plugging agent for drilling fluid, which comprises the following components in percentage by mass: 2-5% of polylactic acid microsphere plugging agent, 38-50% of polylactic acid granular plugging agent, 40-55% of polylactic acid fibrous plugging agent and 2-5% of polylactic acid sheet plugging agent. Meanwhile, the invention also provides a preparation method of the polylactic acid microsphere plugging agent, the polylactic acid fibrous plugging agent and the polylactic acid sheet plugging agent. The polylactic acid plugging agent is a plugging agent which can be completely self-degraded in drilling fluid. The plugging agent can effectively plug formation pores by matching different particle sizes and different forms, is degraded after well completion operation, and achieves the effect of reservoir protection to the maximum extent.
Description
Technical Field
The invention relates to a blocking agent which is used for reducing reservoir damage and can be completely self-degraded in a drilling process in the field of petrochemical additives.
Background
During drilling, the water and solid particles in the drilling fluid leak into the formation along the voids in the formation. Particularly, when drilling a reservoir, the blocking of the stratum caused by the migration of solid-phase particles and the water locking effect caused by the invasion of liquid phase into the stratum are the main reasons for causing the damage of the reservoir and reducing the liquid production. The current common method is to add a plugging agent into the drilling fluid to plug the stratum so as to prevent harmful solid phase and liquid phase from invading the stratum to cause damage to the stratum. In order to improve the plugging effect of the stratum, the plugging agent is matched with plugging materials with different shapes and different particle sizes according to the shape and the size of the pore cracks of the stratum. The existing commonly used plugging materials are granular and fibrous, but need to be removed at a later stage after plugging, and if the removal is not thorough, secondary damage can be caused to the stratum.
Polylactic acid (PLA) and its copolymer are synthetic high molecular materials with excellent biocompatibility and biodegradability, and can be degraded automatically under the action of natural enzyme.
Disclosure of Invention
The invention aims to provide a completely degradable plugging agent for drilling fluid and a preparation method thereof, aiming at the conditions that the plugging agent cannot be naturally degraded and cannot completely remove secondary damage to a reservoir stratum in the prior art. The plugging agent with different particle sizes is prepared by using naturally degradable polylactic acid as a raw material through different preparation processes, and can be naturally degraded in a stratum while the plugging effect is ensured, so that the effect of reservoir protection is achieved.
The technical scheme comprises the following steps:
a completely degradable plugging agent for drilling fluid comprises the following components in percentage by mass: 2-5% of polylactic acid microsphere plugging agent, 38-50% of polylactic acid granular plugging agent, 40-55% of polylactic acid fibrous plugging agent and 2-5% of polylactic acid sheet plugging agent.
Wherein:
the particle size range of the polylactic acid microsphere plugging agent is 1-20 micrometers;
the polylactic acid granular blocking agent comprises three types according to different grain diameter ranges, wherein the grain diameter range of the type I polylactic acid granules is 20-25 mu m, the grain diameter range of the type II polylactic acid granular blocking agent is 25-30 mu m, and the grain diameter range of the type III polylactic acid granular blocking agent is 30-35 mu m;
the fiber diameter of the polylactic acid fibrous plugging agent is 5-15 microns, the polylactic acid fibrous plugging agent comprises three types according to the fiber length, the fiber length of the polylactic acid fibrous plugging agent I is less than 0.5mm, the fiber length of the polylactic acid fibrous plugging agent II is 1-1.5 mm, and the fiber length of the polylactic acid fibrous plugging agent III is more than 1.5 mm;
the thickness of the sheet material of the polylactic acid sheet plugging agent is 0.2 mm-0.5 mm, the sheet material comprises three types according to the length of the sheet material, the fiber length of the polylactic acid sheet plugging agent I is 2 mm-3 mm, the fiber length of the polylactic acid fibrous plugging agent II is 3 mm-4 mm, and the fiber length of the polylactic acid fibrous plugging agent III is 4 mm-5 mm.
Further:
the mixing ratio of the type I, type II and type III polylactic acid particle plugging agents in the polylactic acid particle plugging agent is 1:2: 5;
the mixing ratio of the type I, the type II and the type III polylactic acid fibrous plugging agents in the polylactic acid fibrous plugging agent is 5:3: 2;
the mixing ratio of the type I, the type II and the type III polylactic acid in the polylactic acid sheet plugging agent is 3:4: 4.
The preparation method of the polylactic acid microsphere plugging agent comprises the following steps:
(1) preparation of the aqueous phase
Weighing 1-4 g of emulsifier, putting the emulsifier into 200mL of distilled water, stirring, heating to fully dissolve the emulsifier, filtering the prepared solution, and pouring the filtered solution into a reaction container; the emulsifier is one or a mixture of polyvinyl alcohol and tween 80;
(2) preparation of oil phase
Weighing 0.5-7 g of polylactic acid (PLA), adding into 10-100 mL of polylactic acid solvent, stirring and dissolving to fully disperse the PLA;
(3) preparation of polylactic acid microsphere plugging agent
Stirring a reaction container filled with a water phase at a constant speed, dropwise adding an oil phase into the reaction container at a fixed dropwise adding speed, controlling the dropwise adding time to be 5-10 min, continuously stirring for 3-5 h, heating in a water bath to volatilize dichloromethane, after emulsion foam disappears, performing centrifugal separation, pouring out a supernatant, repeatedly washing a centrifugate with distilled water, and performing vacuum drying on a fully cleaned product in a vacuum drying oven to obtain the powdery milky polylactic acid microsphere plugging agent.
The preparation method of the polylactic acid fibrous plugging agent comprises the following steps:
(1) preparation of spinning solution
Weighing 2.5-5 g of polylactic acid (PLA), adding into 100mL of polylactic acid solvent, and stirring for dissolving to fully disperse the PLA;
(2) the prepared spinning solution is received at the position where the voltage is 18 kV-25 kV and the distance between a receiving plate and a needle is 4-10 cm, the temperature of the spinning solution is controlled at 20-25 ℃, the nano fibrous plugging agent is prepared through electrospinning equipment, and after the spinning is completely cooled and formed, the spinning is cut according to the length requirements of different models.
The preparation method of the polylactic acid flaky plugging agent comprises the following steps:
(1) weighing 10 g-20 g of polylactic acid (PLA), adding into 100mL of polylactic acid solvent, and stirring and mixing at a low speed to prepare polylactic acid paste;
(2) placing the polylactic acid paste on a sheet machine with films laid on two sides, and compacting by using a press roll of the sheet machine to prepare a sheet;
(3) rolling the sheet, and placing the sheet in a constant-temperature drying room for thickening to obtain a cut polylactic acid sheet mould pressing material;
(4) and cutting the sheet die pressing material into sheets according to the model requirement.
The polylactic acid solvent is one or a mixed solvent of more of dichloromethane, chloroform and acetone.
The polylactic acid particle blocking agent mentioned in the present invention is a conventional commercially available polylactic acid particle, and further, is commercially available from co-plastication technology ltd, guan, city.
The invention selects degradable environment-friendly material polylactic acid as raw material, and utilizes the characteristic of natural degradation of the polylactic acid to process the polylactic acid into four different shapes of polylactic acid microsphere plugging agent, polylactic acid granular plugging agent, polylactic acid fibrous plugging agent and polylactic acid sheet plugging agent according to different sizes and shapes of gaps of the stratum, and the plugging materials with different sizes. The polylactic acid microsphere plugging agent is mainly used for plugging micropores with the size of below 20 microns in a stratum, the polylactic acid granular plugging agent is mainly used for plugging gaps with the size of above 20 microns in the stratum, the polylactic acid fibrous plugging agent is mainly used for plugging gaps of cracks in the stratum, and the polylactic acid sheet plugging agent is mainly used for forming a layer of plugging layer on the surface of a well wall to prevent liquid phase intrusion. The four blocking agents with different shapes sequentially form a blocking layer on the well wall to effectively protect the reservoir. The plugging agent can be automatically degraded after drilling is finished, secondary clearing is not needed, the plugging agent is not damaged to a reservoir after being completely degraded, and oil layer protection can be realized to the maximum extent.
Detailed Description
Description of the preferred embodiments
A completely degradable plugging agent for drilling fluid comprises the following components in percentage by mass: 2-5% of polylactic acid microsphere plugging agent, 38-50% of polylactic acid granular plugging agent, 40-55% of polylactic acid fibrous plugging agent and 2-5% of polylactic acid sheet plugging agent.
The particle size range of the polylactic acid microsphere plugging agent mentioned in the embodiment is 1-20 μm.
The polylactic acid particle blocking agent mentioned in this example is classified into three types according to their particle size ranges, wherein the particle size range of the type I polylactic acid particles is 20 μm to 25 μm, the particle size range of the type II polylactic acid particle blocking agent is 25 μm to 30 μm, and the particle size range of the type III polylactic acid particle blocking agent is 30 μm to 35 μm. The mixing ratio of the type I, type II and type III polylactic acid particle plugging agents in the polylactic acid particle plugging agent is 1:2: 5.
The polylactic acid fibrous plugging agent mentioned in the embodiment has a fiber diameter of 5 to 15 μm, and the fiber type graft plugging agent is classified into three types according to the length of the fiber, wherein the fiber length of the type I polylactic acid fibrous plugging agent is less than 0.5mm, the fiber length of the type II polylactic acid fibrous plugging agent is 1 to 1.5mm, and the fiber length of the type III polylactic acid fibrous plugging agent is more than 1.5 mm. The mixing ratio of the polylactic acid fibrous plugging agent I, the polylactic acid fibrous plugging agent II and the polylactic acid fibrous plugging agent III is 5:3: 2.
The thickness of the sheet material of the polylactic acid sheet plugging agent mentioned in the embodiment is 0.2 mm-0.5 mm, the material is divided into three types according to the length of the sheet material, the length of the polylactic acid sheet plugging agent I is 2 mm-3 mm, the length of the polylactic acid sheet plugging agent II is 3 mm-4 mm, and the length of the polylactic acid sheet plugging agent III is 4 mm-5 mm. The mixing ratio of the type I, the type II and the type III polylactic acid in the polylactic acid sheet plugging agent is 3:4
The preparation method of the polylactic acid microsphere plugging agent comprises the following steps:
(1) preparation of the aqueous phase
Weighing 1-4 g of emulsifier, putting the emulsifier into 200mL of distilled water, properly stirring the emulsifier by using a constant-temperature magnetic stirrer, and heating the emulsifier to fully dissolve the emulsifier. The prepared solution was filtered and poured into a 500mL three-necked flask. Wherein the emulsifier is one or more of polyvinyl alcohol and Tween 80.
(2) Preparation of oil phase
Weighing 0.5-7 g of polylactic acid (PLA), adding into 10-100 mL of polylactic acid solvent, stirring with a glass rod to completely dissolve, and then fully dispersing with an ultrasonic cleaner. The polylactic acid solvent is one or a mixture of more of dichloromethane, chloroform and acetone.
(3) Preparation of polylactic acid microspheres
A500 mL three-necked flask containing the aqueous phase was set on a booster electric stirrer, and the stirrer was started and stirred at a constant speed. And (3) dropwise adding the oil phase into the three-neck flask at a fixed dropwise adding speed by using an injector, wherein the dropwise adding time is controlled to be 5-10 min. Continuously stirring for 3-5 hours, and then heating in a water bath to volatilize dichloromethane. After the foam of the emulsion disappeared, the mixture was centrifuged, the supernatant was decanted, and the centrifuged material was washed with distilled water repeatedly. And (3) drying the fully cleaned product in a vacuum drying oven in vacuum to obtain powdery milky microspheres.
The preparation method of the polylactic acid fibrous plugging agent mentioned in the example comprises the following steps
(1) Preparation of spinning solution
Weighing 2.5-5 g of polylactic acid (PLA), adding into 100mL of polylactic acid solvent, stirring with a glass rod to completely dissolve, and then fully dispersing with an ultrasonic cleaner.
(2) The prepared spinning solution is received at the position where the voltage is 18 kV-25 kV and the distance between a receiving plate and a needle is 4-10 cm, and the temperature of the spinning solution is controlled at 20-25 ℃ to prepare the nano fibrous plugging agent through electrospinning equipment. And cutting the spun yarn according to the length requirements of different models after the spun yarn is completely cooled and formed.
Wherein the polylactic acid solvent is one or a mixture of more of dichloromethane, chloroform and acetone.
The preparation method of the polylactic acid sheet plugging agent mentioned in the embodiment comprises the following steps: weighing 10 g-20 g of polylactic acid (PLA), adding into 100mL of polylactic acid solvent, and mixing at low speed by using a powerful mixer to prepare the polylactic acid paste. And (3) placing the polylactic acid paste on a sheet machine with films laid on two sides, and compacting by using a press roll of the sheet machine to prepare the sheet. And rolling the sheet, and placing the sheet in a constant-temperature drying room for thickening to obtain the polylactic acid sheet mould pressing material capable of being cut. And cutting the sheet die pressing material into sheets according to the model requirement.
The polylactic acid pellet blocking agent mentioned in this example was a conventional commercially available polylactic acid pellet, and further, is commercially available from co-plastication technology ltd, a city of Dongguan.
Example 1:
(1) preparation of polylactic acid microsphere plugging agent
1g of polyvinyl alcohol and 0.2g of Tween 80 are weighed, put into 200mL of distilled water, stirred appropriately by a constant-temperature magnetic stirrer, heated to be fully dissolved, and the prepared solution is filtered and poured into a 500mL three-neck flask. 0.5g of polylactic acid (PLA) was weighed, added to 100mL of methylene chloride, stirred with a glass rod to be completely dissolved, and then sufficiently dispersed with an ultrasonic cleaner. A500 mL three-necked flask containing the aqueous phase was set on a booster electric stirrer, and the stirrer was started and stirred at a constant speed. The oil phase was added dropwise into the three-necked flask with a syringe at a constant dropping rate for 10 min. Stirring was continued for 3 hours, after which time the water bath was heated to volatilize the dichloromethane. After the foam of the emulsion disappeared, the mixture was centrifuged, the supernatant was decanted, and the centrifuged material was washed with distilled water repeatedly. And (3) drying the fully cleaned product in a vacuum drying oven in vacuum to obtain powdery milky microspheres.
(2) Preparation of polylactic acid fibrous plugging agent
2.5g of polylactic acid (PLA) was weighed, added to 100mL of methylene chloride, stirred with a glass rod to be completely dissolved, and then sufficiently dispersed with an ultrasonic cleaner. And (3) receiving the prepared spinning solution at the position of 18 kV voltage and 4cm distance from a receiving plate to a needle head, and controlling the temperature of the spinning solution at 20-25 ℃ to prepare the nano fibrous plugging agent through electrospinning equipment. And cutting the spun yarn into fibrous plugging agent with the thickness of 0.5mm after the spun yarn is completely cooled and formed.
(3) Preparation of polylactic acid sheet plugging agent
10g of polylactic acid (PLA) was weighed, added to 100mL of a polylactic acid solvent, and mixed at a low speed with a powerful mixer to prepare a polylactic acid paste. And (3) placing the polylactic acid paste on a sheet machine with films laid on two sides, and compacting by using a press roll of the sheet machine to prepare the sheet. And rolling the sheet, and placing the sheet in a constant-temperature drying room for thickening to obtain the polylactic acid sheet mould pressing material capable of being cut. And (3) cutting the sheet mould pressing material into a sheet polylactic acid plugging agent with the length and the width of 2 mm.
The polylactic acid plugging agent comprises the following components in percentage by mass: 5% of polylactic acid microsphere blocking agent, 45% of polylactic acid granular blocking agent (20-25 mu m), 45% of polylactic acid fibrous blocking agent and 5% of polylactic acid sheet blocking agent.
Evaluation of plugging Effect
| Core Permeability/mD | Permeability/mD after plugging | Plugging Rate/% | permeability/mD after 20d | Permeability recovery/% |
| 65.2 | 6.9 | 97.4 | 64.5 | 98.9 |
Example 2:
(1) preparation of polylactic acid microspheres
2g of polyvinyl alcohol and 0.5g of Tween 80 are weighed, put into 200mL of distilled water, stirred properly by a constant-temperature magnetic stirrer, and heated to be fully dissolved. The prepared solution was filtered and poured into a 500mL three-necked flask. 2g of polylactic acid (PLA) was weighed, added to 100mL of methylene chloride, stirred with a glass rod to be completely dissolved, and then sufficiently dispersed with an ultrasonic cleaner. A500 mL three-necked flask containing the aqueous phase was set on a booster electric stirrer, and the stirrer was started and stirred at a constant speed. The oil phase was added dropwise into the three-necked flask with a syringe at a constant dropping rate for 7 min. Stirring was continued for 3 hours, after which time the water bath was heated to volatilize the dichloromethane. After the foam of the emulsion disappeared, the mixture was centrifuged, the supernatant was decanted, and the centrifuged material was washed with distilled water repeatedly. And (3) drying the fully cleaned product in a vacuum drying oven in vacuum to obtain powdery milky microspheres.
(2) Preparation of polylactic acid fibrous plugging agent
3.5g of polylactic acid (PLA) was weighed, added to 100mL of methylene chloride, stirred with a glass rod to be completely dissolved, and then sufficiently dispersed with an ultrasonic cleaner. And (3) receiving the prepared spinning solution at a position with a voltage of 21 kV and a distance of 6cm from a receiving plate to a needle head, and controlling the temperature of the spinning solution at 20-25 ℃ to prepare the nano fibrous plugging agent through electrospinning equipment. And cutting the spun yarn into 1mm fibrous plugging agent after the spun yarn is completely cooled and formed.
(3) Polylactic acid sheet plugging agent and preparation thereof
13g of polylactic acid (PLA) was weighed, added to 100mL of a polylactic acid solvent, and mixed at a low speed with a powerful mixer to prepare a polylactic acid paste. And (3) placing the polylactic acid paste on a sheet machine with films laid on two sides, and compacting by using a press roll of the sheet machine to prepare the sheet. And rolling the sheet, and placing the sheet in a constant-temperature drying room for thickening to obtain the polylactic acid sheet mould pressing material capable of being cut. And (3) cutting the sheet mould pressing material into a sheet polylactic acid plugging agent with the length and the width of 2 mm.
The polylactic acid plugging agent comprises the following components in percentage by mass: 2% of polylactic acid microsphere plugging agent, 46% of polylactic acid granular plugging agent (25-30 μm), 48% of polylactic acid fibrous plugging agent and 5% of polylactic acid sheet plugging agent.
Evaluation of plugging Effect
| Core Permeability/mD | Permeability/mD after plugging | Plugging Rate/% | permeability/mD after 20d | Permeability recovery/% |
| 126.3 | 26.2 | 79.2 | 126.0 | 99.8 |
Example 3:
(1) preparation of polylactic acid microspheres
2.5g of polyvinyl alcohol and 0.5g of Tween 80 are weighed, put into 200mL of distilled water, stirred appropriately by a constant-temperature magnetic stirrer, and heated to be dissolved fully. The prepared solution was filtered and poured into a 500mL three-necked flask. 5g of polylactic acid (PLA) was weighed, added to 100mL of methylene chloride, stirred with a glass rod to be completely dissolved, and then sufficiently dispersed with an ultrasonic cleaner. A500 mL three-necked flask containing the aqueous phase was set on a booster electric stirrer, and the stirrer was started and stirred at a constant speed. The oil phase was added dropwise into the three-necked flask with a syringe at a constant dropping rate for 7 min. Stirring was continued for 3 hours, after which time the water bath was heated to volatilize the dichloromethane. After the foam of the emulsion disappeared, the mixture was centrifuged, the supernatant was decanted, and the centrifuged material was washed with distilled water repeatedly. And (3) drying the fully cleaned product in a vacuum drying oven in vacuum to obtain powdery milky microspheres.
(2) Preparation of polylactic acid fibrous plugging agent
4g of polylactic acid (PLA) was weighed, added to 100mL of methylene chloride, stirred with a glass rod to be completely dissolved, and then sufficiently dispersed with an ultrasonic cleaner. And (3) receiving the prepared spinning solution at a position with a voltage of 25kV and a distance of a receiving plate being 10cm from a needle head, and controlling the temperature of the spinning solution at 20-25 ℃ to prepare the nano fibrous plugging agent through electrospinning equipment. And cutting the spun yarn into 1.5mm fibrous plugging agent after the spun yarn is completely cooled and formed.
(3) Polylactic acid sheet plugging agent and preparation thereof
Polylactic acid (PLA) 16g was weighed, added to 100mL of a polylactic acid solvent, and mixed at a low speed with a powerful mixer to prepare a polylactic acid paste. And (3) placing the polylactic acid paste on a sheet machine with films laid on two sides, and compacting by using a press roll of the sheet machine to prepare the sheet. And rolling the sheet, and placing the sheet in a constant-temperature drying room for thickening to obtain the polylactic acid sheet mould pressing material capable of being cut. And (3) cutting the sheet mould pressing material into a sheet polylactic acid plugging agent with the length and the width of 3 mm.
The polylactic acid plugging agent comprises the following components in percentage by mass: 2% of polylactic acid microsphere plugging agent, 46% of polylactic acid granular plugging agent (30-35 μm), 48% of polylactic acid fibrous plugging agent and 5% of polylactic acid sheet plugging agent.
Evaluation of plugging Effect
| Core Permeability/mD | Permeability/mD after plugging | Plugging Rate/% | permeability/mD after 20d | Permeability recovery/% |
| 156.3 | 38.5 | 75.4 | 155.3 | 99.3 |
Example 4:
(1) preparation of polylactic acid microspheres
3.5g of polyvinyl alcohol and 0.5g of Tween 80 are weighed, put into 200mL of distilled water, stirred properly by a constant-temperature magnetic stirrer, and heated to be dissolved fully. The prepared solution was filtered and poured into a 500mL three-necked flask. 7g of polylactic acid (PLA) was weighed, added to 100mL of methylene chloride, stirred with a glass rod to be completely dissolved, and then sufficiently dispersed with an ultrasonic cleaner. A500 mL three-necked flask containing the aqueous phase was set on a booster electric stirrer, and the stirrer was started and stirred at a constant speed. The oil phase was added dropwise into the three-necked flask with a syringe at a constant dropping rate for 5 min. Stirring was continued for 3 hours, after which time the water bath was heated to volatilize the dichloromethane. After the foam of the emulsion disappeared, the mixture was centrifuged, the supernatant was decanted, and the centrifuged material was washed with distilled water repeatedly. And (3) drying the fully cleaned product in a vacuum drying oven in vacuum to obtain powdery milky microspheres.
(2) Preparation of polylactic acid fibrous plugging agent
5g of polylactic acid (PLA) was weighed, added to 100mL of methylene chloride, stirred with a glass rod to be completely dissolved, and then sufficiently dispersed with an ultrasonic cleaner. And (3) receiving the prepared spinning solution at a position with a voltage of 25kV and a distance of a receiving plate being 10cm from a needle head, and controlling the temperature of the spinning solution at 20-25 ℃ to prepare the nano fibrous plugging agent through electrospinning equipment. And cutting the spun yarn into 1.5mm fibrous plugging agent after the spun yarn is completely cooled and formed.
(3) Polylactic acid sheet plugging agent and preparation thereof
20g of polylactic acid (PLA) was weighed, added to 100mL of a polylactic acid solvent, and mixed at a low speed with a powerful mixer to prepare a polylactic acid paste. And (3) placing the polylactic acid paste on a sheet machine with films laid on two sides, and compacting by using a press roll of the sheet machine to prepare the sheet. And rolling the sheet, and placing the sheet in a constant-temperature drying room for thickening to obtain the polylactic acid sheet mould pressing material capable of being cut. And (3) cutting the sheet mould pressing material into a sheet polylactic acid plugging agent with the length and the width of 5 mm.
The polylactic acid plugging agent comprises the following components in percentage by mass: 2% of polylactic acid microsphere plugging agent, 46% of polylactic acid granular plugging agent (30-35 μm), 48% of polylactic acid fibrous plugging agent and 5% of polylactic acid sheet plugging agent.
Evaluation of plugging Effect
| Core Permeability/mD | Permeability/mD after plugging | Plugging Rate/% | permeability/mD after 20d | Permeability recovery/% |
| 201.6 | 52.1 | 74.1 | 192.5 | 95.6 |
Claims (9)
1. The completely degradable plugging agent for the drilling fluid is characterized by comprising the following components in percentage by mass: 2-5% of polylactic acid microsphere plugging agent, 38-50% of polylactic acid granular plugging agent, 40-55% of polylactic acid fibrous plugging agent and 2-5% of polylactic acid sheet plugging agent.
2. The fully degradable plugging agent for drilling fluid according to claim 1, wherein:
the particle size range of the polylactic acid microsphere plugging agent is 1-20 micrometers;
the polylactic acid granular blocking agent comprises three types according to different grain diameter ranges, wherein the grain diameter range of the type I polylactic acid granules is 20-25 mu m, the grain diameter range of the type II polylactic acid granular blocking agent is 25-30 mu m, and the grain diameter range of the type III polylactic acid granular blocking agent is 30-35 mu m;
the fiber diameter of the polylactic acid fibrous plugging agent is 5-15 microns, the polylactic acid fibrous plugging agent comprises three types according to the fiber length, the fiber length of the polylactic acid fibrous plugging agent I is less than 0.5mm, the fiber length of the polylactic acid fibrous plugging agent II is 1-1.5 mm, and the fiber length of the polylactic acid fibrous plugging agent III is more than 1.5 mm;
the thickness of the sheet material of the polylactic acid sheet plugging agent is 0.2 mm-0.5 mm, the sheet material comprises three types according to the length of the sheet material, the fiber length of the polylactic acid sheet plugging agent I is 2 mm-3 mm, the fiber length of the polylactic acid fibrous plugging agent II is 3 mm-4 mm, and the fiber length of the polylactic acid fibrous plugging agent III is 4 mm-5 mm.
3. The fully degradable plugging agent for drilling fluid according to claim 2, wherein:
the mixing ratio of the type I, type II and type III polylactic acid particle plugging agents in the polylactic acid particle plugging agent is 1:2: 5;
the mixing ratio of the type I, the type II and the type III polylactic acid fibrous plugging agents in the polylactic acid fibrous plugging agent is 5:3: 2;
the mixing ratio of the type I, the type II and the type III polylactic acid in the polylactic acid sheet plugging agent is 3:4: 4.
4. The fully degradable plugging agent for drilling fluid of claim 1, 2 and 3, wherein the preparation method of the polylactic acid microsphere plugging agent comprises the following steps:
(1) preparation of the aqueous phase
Weighing 1-4 g of emulsifier, putting the emulsifier into 200mL of distilled water, stirring, heating to fully dissolve the emulsifier, filtering the prepared solution, and pouring the filtered solution into a reaction container; the emulsifier is one or a mixture of polyvinyl alcohol and tween 80;
(2) preparation of oil phase
Weighing 0.5-7 g of polylactic acid (PLA), adding into 10-100 mL of polylactic acid solvent, stirring and dissolving to fully disperse the PLA;
(3) preparation of polylactic acid microsphere plugging agent
Stirring a reaction container filled with a water phase at a constant speed, dropwise adding an oil phase into the reaction container at a fixed dropwise adding speed, controlling the dropwise adding time to be 5-10 min, continuously stirring for 3-5 h, heating in a water bath to volatilize dichloromethane, after emulsion foam disappears, performing centrifugal separation, pouring out a supernatant, repeatedly washing a centrifugate with distilled water, and performing vacuum drying on a fully cleaned product in a vacuum drying oven to obtain the powdery milky polylactic acid microsphere plugging agent.
5. The fully degradable plugging agent for drilling fluid according to claim 1, 2 and 3, wherein the preparation method of the polylactic acid fibrous plugging agent comprises the following steps:
(1) preparation of spinning solution
Weighing 2.5-5 g of polylactic acid (PLA), adding into 100mL of polylactic acid solvent, and stirring for dissolving to fully disperse the PLA;
(2) the prepared spinning solution is received at the position where the voltage is 18 kV-25 kV and the distance between a receiving plate and a needle is 4-10 cm, the temperature of the spinning solution is controlled at 20-25 ℃, the nano fibrous plugging agent is prepared through electrospinning equipment, and after the spinning is completely cooled and formed, the spinning is cut according to the length requirements of different models.
6. The completely degradable plugging agent for drilling fluid as claimed in claim 1, 2 and 3, wherein the preparation method of the polylactic acid sheet plugging agent comprises the following steps:
(1) weighing 10 g-20 g of polylactic acid (PLA), adding into 100mL of polylactic acid solvent, and stirring and mixing at a low speed to prepare polylactic acid paste;
(2) placing the polylactic acid paste on a sheet machine with films laid on two sides, and compacting by using a press roll of the sheet machine to prepare a sheet;
(3) rolling the sheet, and placing the sheet in a constant-temperature drying room for thickening to obtain a cut polylactic acid sheet mould pressing material;
(4) and cutting the sheet die pressing material into sheets according to the model requirement.
7. The method for preparing the fully degradable plugging agent for drilling fluid according to claim 1, 2 or 3,
the preparation method of the polylactic acid microsphere plugging agent comprises the following steps:
(1) preparation of the aqueous phase
Weighing 1-4 g of emulsifier, putting the emulsifier into 200mL of distilled water, stirring, heating to fully dissolve the emulsifier, filtering the prepared solution, and pouring the filtered solution into a reaction container; the emulsifier is one or a mixture of polyvinyl alcohol and tween 80;
(2) preparation of oil phase
Weighing 0.5-7 g of polylactic acid (PLA), adding into 10-100 mL of polylactic acid solvent, stirring and dissolving to fully disperse the PLA;
(3) preparation of polylactic acid microsphere plugging agent
Stirring a reaction container filled with a water phase at a constant speed, dropwise adding an oil phase into the reaction container at a fixed dropwise adding speed, controlling the dropwise adding time to be 5-10 min, continuously stirring for 3-5 h, heating in a water bath to volatilize dichloromethane, after emulsion foam disappears, performing centrifugal separation, pouring out a supernatant, repeatedly washing a centrifugate with distilled water, and performing vacuum drying on a fully cleaned product in a vacuum drying oven to obtain a powdery milky polylactic acid microsphere blocking agent;
the preparation method of the polylactic acid fibrous plugging agent comprises the following steps:
(1) preparation of spinning solution
Weighing 2.5-5 g of polylactic acid (PLA), adding into 100mL of polylactic acid solvent, and stirring for dissolving to fully disperse the PLA;
(2) the prepared spinning solution is received at the position where the voltage is 18 kV-25 kV and the distance between a receiving plate and a needle is 4-10 cm, the temperature of the spinning solution is controlled at 20-25 ℃, a nano fibrous plugging agent is prepared through electrospinning equipment, and after the spinning is completely cooled and formed, the spinning is cut according to the length requirements of different types;
the preparation method of the polylactic acid flaky plugging agent comprises the following steps:
(1) weighing 10 g-20 g of polylactic acid (PLA), adding into 100mL of polylactic acid solvent, and stirring and mixing at a low speed to prepare polylactic acid paste;
(2) placing the polylactic acid paste on a sheet machine with films laid on two sides, and compacting by using a press roll of the sheet machine to prepare a sheet;
(3) rolling the sheet, and placing the sheet in a constant-temperature drying room for thickening to obtain a cut polylactic acid sheet mould pressing material;
(4) and cutting the sheet die pressing material into sheets according to the model requirement.
8. The fully degradable plugging agent for drilling fluid of claim 4, 5 or 6, wherein the polylactic acid solvent is one or a mixed solvent of dichloromethane, chloroform and acetone.
9. The fully degradable plugging agent for drilling fluid of claim 7, wherein the polylactic acid solvent is one or a mixture of dichloromethane, chloroform and acetone.
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