Water-based drilling fluid suitable for gravel-pack intervals in the eastern part of Ecuador and method for its preparation

Abstract

The application discloses a water-based drilling fluid suitable for gravel layer well sections in eastern Ecuador and a preparation method thereof, relates to the oilfield drilling technical field, and solves the technical problem that existing drilling fluids cannot adapt to deep well drilling in oil exploitation, and comprises superfine fibers, flexible temporary plugging agents, granular plugging agents, anti-sloughing agents, vegetable oil lubricants, pH regulators, fluid loss reducers, viscosity increasing agents, weighting agents and water; the water-based drilling fluid is particularly suitable for drilling operations of gravel layer well sections in eastern Ecuador, has moderate viscosity, and has good sand carrying and wall protection capacity, and thus not only meets the needs of gravel layer well sections, but also meets the technical requirements of drilling fluids for upper shale and lower mudstone formations; specifically, the flexible temporary plugging agents, the granular plugging agents and the anti-sloughing agents in the system have good plugging effects on the upper shale and the lower mudstone, improve mud cake quality, keep well walls stable, and one system can adapt to different formations, and is convenient and feasible to operate in actual application.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of oilfield drilling, more particularly to the technical field of water-based drilling fluid suitable for gravel layer well section in eastern Ecuador. BACKGROUND

[0002] Ecuador is a country located in the northwest of South America, adjacent to Colombia in the north, connected to Peru in the south, and facing the Pacific Ocean in the west, with daily oil production exceeding 500,000 barrels. Ecuadorian crude oil is mainly heavy crude oil, with an API value of generally 12-15, and the main production area is in the eastern tropical rainforest region. Ecuadorian oil development began in the 1970s, led by Western multinational oil companies, and adopted a relatively extensive development approach, resulting in serious environmental pollution and triggering a series of international lawsuits over the years. In the 21st century, Chinese oil companies began to enter Ecuador, and China Petroleum and Sinopec jointly acquired Andes Oil Company, which has the operating rights of Block 14 and 17 in Ecuador, and engineering and technical service companies have also entered Ecuador, undertaking drilling, well repair, exploration and related professional technical service tasks, and providing related equipment, materials and technology, and have now become the dominant force in Ecuadorian oil development.

[0003] There are several gravel layers with different thicknesses in the TIYUYACU formation in eastern Ecuador, with a total thickness exceeding 200 meters, composed of mudstone, gravel and chert, etc. The characteristics of this section of formation are large hardness, uneven distribution, strong permeability, easy hole shrinkage, serious drill bit wear, and prone to differential pressure sticking. In addition, during the tripping and casing process, this section needs to be repeatedly reamed and circulated, resulting in a large amount of non-production time and affecting the well construction period.

[0004] In the prior art, there are also many drilling fluid systems applied to gravel layer well sections. For example, Chinese invention patent publication No. “CN111019615A” discloses a non-excavation mud system suitable for gravel strata and a preparation method, and the publication date is April 17, 2020. Each cubic meter of the mud system includes the following components by mass fraction: 100 parts of water, 4 parts of sodium-based bentonite, 1 part of a blocking agent, 0.35-0.45 parts of a plant glue, 0.05-0.15 parts of a flocculating agent, 0.05-0.15 parts of a viscosity increasing agent, 0.5 parts of a fluid loss reducer, 1.1 parts of a wear-reducing mud cake inhibitor, and 0.1 parts of sodium hydroxide. The mud system has unique cementation water sensitivity swelling inhibition, which inhibits the swelling of water-sensitive filling materials with low cementation strength between gravel particles; it can form a dense mud film, reduce the filtration loss, balance the soil pressure, and thus enhance the wellbore stability; it can reduce the adhesion coefficient and prevent drill bit mud cake; it has good rheological properties, filtration reduction performance and lubricity, can meet the requirements of shield mud drilling, and has the advantages of environmental protection and low cost; it can effectively reduce the torque, wear and fatigue of the drilling tool when passing through unweathered hard pebbles in the formation, and prolong the service life of the drill bit bearing.

[0005] The trenchless mud system in the above patent can only be applied to surface drilling operation, and cannot adapt to deep well drilling in oil exploitation, for example, reducing the drilling fluid density will cause instability of the upper or lower formation, and the gravel layer drilling problem is not fundamentally solved, the traditional material and method for increasing the sealing property are not strong in pertinence for the gravel layer well section, in addition, changing the well structure will cause the increase of casing layers, and increase the well construction cost. SUMMARY

[0006] The present application aims at: in order to solve the technical problems in the prior art that the drilling fluid cannot guarantee the stability of the well wall and control the formation pressure by simply relying on reducing the drilling fluid density, and cannot meet the drilling fluid technical requirements of the upper and lower formations at the same time, a set of system cannot cope with different formations including the gravel layer, in addition, changing the well structure and the casing sequence is not easy to operate and implement in engineering, and increases the well construction cost, the present application provides a water-based drilling fluid suitable for the gravel layer well section in the east of Ecuador and a preparation method thereof.

[0007] In order to realize the above-mentioned purpose, the present application specifically adopts the following technical scheme: a water-based drilling fluid suitable for the gravel layer well section in the east of Ecuador, the water-based drilling fluid comprises superfine fibers, flexible temporary plugging agent, particle plugging agent, anti-sloughing agent, vegetable oil lubricant, pH regulator, filtrate reducer, viscosity enhancer, weighting agent and water, wherein the weight percentage content of each component is: 0.1-0.3% of superfine fibers, 0.5-0.8% of flexible temporary plugging agent, 0.5-1.0% of particle plugging agent, 0.3-1.0% of anti-sloughing agent, 0.2-1.0% of vegetable oil lubricant, 0.2-0.5% of pH regulator, 0.6-1.5% of filtrate reducer, 0.5-1.2% of viscosity enhancer, 5.0-20.0% of weighting agent, and the balance is water.

[0008] In the technical scheme of the application, the vegetable oil lubricant is an environmentally friendly and efficient drilling fluid lubricant, mainly for improving the lubricity of the drilling system and reducing the friction between the drilling tool and the well wall; the pH regulator is mainly for improving the pH value of the system and maintaining it in a weak alkaline state, which is beneficial to the performance of other additives; the viscosity increasing agent is for maintaining the appropriate viscosity of the system so as to carry the drilling cuttings to the ground and purify the wellbore; the weighting agent is for maintaining the appropriate density of the drilling fluid system, keeping the bottom hole pressure and preventing the overflow and blowout accidents, and also helps to stabilize the well wall by the principle of mechanical balance; the superfine fiber in the water-based drilling fluid has good tensile strength and is easy to disperse in the liquid without increasing the viscosity of the system, and has good sand carrying and plugging capacity, and its mechanism is that it forms a network structure in the well wall mud cake and the gravel layer pore, has high mechanical strength, can quickly bind the flexible temporary plugging agent, particle plugging agent, anti-sloughing agent and fluid loss reducer under the condition of the same formation differential pressure, forms a dense high-strength mud cake, avoids causing differential pressure sticking, hole shrinkage and other complex accidents caused by the strong permeability and low pressure of the gravel layer, and in the application process in Parahuacu oil field, the average mechanical drilling speed is increased by 16% compared with before, and in the case of no well, the 9 5 / 8'' casing of the last 6 wells can be smoothly drilled to the bottom; the flexible temporary plugging agent of the application is a polymeric alcohol, which has multiple effects with one agent, is a colorless transparent liquid at room temperature, is a white emulsion at the bottom of the well, can form a protective film on the well wall to play a plugging role, and can also improve the lubricity of the well wall; the sulfonated asphalt and sulfonated phenolic resin are traditional plugging and fluid loss reduction materials, can realize the wetting reverse of the well wall, form a hydrophobic layer, and can be quickly captured by the superfine fiber network and attached to the well wall and pores during the drilling process, so as to prevent the drilling fluid from penetrating into the formation, and fundamentally solve the problems of easy permeability and differential pressure sticking of the gravel layer in the deep well with a vertical depth of more than 2500 meters; the drilling fluid of the application has the advantages of fast drilling speed, low torque, good hole cleaning effect, smooth tripping and casing running process, and saving of a large amount of non-production time, and specifically, the superfine fiber material of the application improves the strength and quality of the mud cake, forms a thin and tough mud cake on the well wall, prevents the drilling fluid from penetrating into the formation, prevents the occurrence of hole shrinkage caused by the virtual thick mud cake, makes the hole smooth, helps to reduce the torque, realizes good hole cleaning, reduces unnecessary circulation and reaming operations, improves the drilling speed, and the drilling fluid system of the application is simple to prepare and maintain, does not need to increase additional auxiliary equipment and cost, and has a good application prospect in the eastern oil field of Ecuador.The water-based drilling fluid of the present application is particularly suitable for drilling operations in the gravel layer section of the eastern part of Ecuador, has moderate viscosity, and has good sand carrying and wall protection capacity, which not only meets the needs of the gravel layer section, but also meets the technical requirements of drilling fluid for the upper shale and lower mudstone formations. Specifically, the water-based drilling fluid system of the present application has moderate viscosity, and the ratio of the viscosity increasing agent is reasonable. Too low viscosity is not conducive to sand carrying, and too high viscosity causes drilling fluid flow difficulty, which is not conducive to drilling operations. The flexible temporary plugging agent, the particle plugging agent and the anti-sloughing agent in the system also have good plugging effect on the upper shale and the lower mudstone, improve the quality of the mud cake, and keep the wellbore stable. A set of system can adapt to different formations, and is convenient and feasible in actual application. The materials used are commonly used materials in the petroleum industry, and are widely available.

[0009] Preferably, the weight percentage of each component is: 0.2-0.3% of superfine fiber, 0.6-0.7% of flexible temporary plugging agent, 0.6-0.9% of particle plugging agent, 0.4-0.8% of anti-sloughing agent, 0.3-0.7% of vegetable oil lubricant, 0.3-0.4% of pH regulator, 0.8-1.2% of fluid loss additive, 0.8-1.0% of viscosity increasing agent, 10.0-15.0% of weighting agent, and the balance is water.

[0010] More preferably, the weight percentage of each component is: 0.2% of superfine fiber, 0.6% of flexible temporary plugging agent, 0.8% of particle plugging agent, 0.7% of anti-sloughing agent, 0.5% of vegetable oil lubricant, 0.3% of pH regulator, 1.0% of fluid loss additive, 0.9% of viscosity increasing agent, 12% of weighting agent, and 83% of water.

[0011] Preferably, the superfine fiber is a polyamide synthetic fiber with a single filament fineness of 0.5 dtex and a single filament length of 1-1.5 cm (the manufacturer is FORTA Company).

[0012] Preferably, the flexible temporary plugging agent is a polymeric alcohol (the manufacturer is Jingzhou Chengxue Industry Company).

[0013] Preferably, the particle plugging agent is industrial sulfonated asphalt SFT (industrial sulfonated asphalt SFT is an industrial sulfonated asphalt SFT for oil fields, black powder, and the manufacturer is Zhengzhou Jingyuan Mud Material Co., Ltd.).

[0014] Preferably, the anti-sloughing agent includes sulfonated phenolic resin, and the sulfonated phenolic resin includes SMP-1 and SMP-2, and the mass ratio of SMP-1 to SMP-2 is 1:1.

[0015] Preferably, the vegetable oil lubricant is a vegetable oil-based drilling fluid extreme pressure lubricant HEP-1, which is a light brown transparent liquid, and the manufacturer is Shandong Deshunyuan Petroleum Technology Co., Ltd.

[0016] Preferably, the pH regulator is magnesium oxide (trade name: REFIT, white powder, manufacturer: INCOPET Company in Ecuador).

[0017] Preferably, the fluid loss additive is low-viscosity anionic cellulose (low-viscosity anionic cellulose is a water-soluble cellulose ether derivative prepared by chemical modification of natural cellulose, with low degree of substitution, manufacturer: Changqing Chemical Group).

[0018] Preferably, the viscosity enhancer includes high-viscosity anionic cellulose and xanthan gum, with a weight ratio of 1:1 to 1.5 (high-viscosity anionic cellulose is PAC-HV, xanthan gum is XC-HV, high-viscosity anionic cellulose is usually used in the form of its sodium salt, manufacturer: Zibo Lianji Chemical Co., Ltd., xanthan gum has the molecular formula (C 35 H 49 O 29 )n, is an extracellular microbial polysaccharide produced by Xanthomonas fermentation of sugars, with a special structure of macromolecules and colloidal properties, and is a good viscosity enhancer material, manufacturer: Zibo Zhongxuan Biochemical Co., Ltd.).

[0019] Preferably, the weighting agent includes 200-mesh limestone powder and 325-mesh limestone powder, with a weight ratio of 1:1 (limestone powder is composed of calcium carbonate, purchased locally in Ecuador).

[0020] A preparation method of a water-based drilling fluid suitable for gravel layer well sections in eastern Ecuador, comprising the following steps:

[0021] Step 1: Prepare each component by adding calculated amounts of water into a slurry preparation tank according to the following proportions: 0.1-0.3% of superfine fibers, 0.5-0.8% of flexible temporary plugging agent, 0.5-1.0% of particulate plugging agent, 0.3-1.0% of anti-sloughing agent, 0.2-1.0% of vegetable oil lubricant, 0.2-0.5% of pH regulator, 0.6-1.5% of fluid loss additive, 0.5-1.2% of viscosity enhancer, 5.0-20.0% of weighting agent, and the rest of water;

[0022] Step 2: Add 0.2-0.5% of pH regulator into the slurry preparation tank and mix thoroughly;

[0023] Step 3: Add 0.6-1.5% of fluid loss additive into the slurry preparation tank and mix thoroughly;

[0024] Step 4: Add 0.5-1.2% of viscosity enhancer into the slurry preparation tank and mix thoroughly, then stand for 24 hours for complete hydration;

[0025] Step 5, 0.5-1.0% of particle blocking agent is added into the mixing tank, and fully stirred and mixed uniformly;

[0026] Step 6, 0.5-0.8% of flexible temporary blocking agent is added into the mixing tank, and fully stirred and mixed uniformly;

[0027] Step 7, 0.3-1.0% of anti-sloughing agent is added into the mixing tank, and fully stirred and mixed uniformly;

[0028] Step 8, 0.2-1.0% of plant oil lubricant is added into the mixing tank, and fully stirred and mixed uniformly;

[0029] Step 9, 5.0-20.0% of weighting agent is added into the mixing tank, and fully stirred and mixed uniformly;

[0030] Step 10, 0.1-0.3% of superfine fiber is added into the mixing tank, and fully stirred and mixed uniformly, to obtain the water-based drilling fluid suitable for the gravel layer well section in eastern Ecuador.

[0031] The beneficial effects of the present application are as follows:

[0032] 1, the water-based drilling fluid of the present application is particularly suitable for drilling operations in the gravel layer well section in eastern Ecuador, has moderate viscosity, good sand carrying and wall protection capacity, not only meets the needs of the gravel layer well section, but also meets the technical requirements of drilling fluid for upper shale and lower mudstone formations, and the materials used are commonly used materials in the petroleum industry, and are widely available;

[0033] 2. The ultrafine fibers of this invention form a network structure in the wellbore mud cake and gravel layer pores, exhibiting high mechanical strength. Under the same formation pressure differential, they can quickly bind the flexible temporary plugging agent, granular plugging agent, anti-collapse agent, and filtration reduction agent, forming a dense, high-strength mud cake. This avoids complex accidents such as differential pressure stuck pipe and wellbore narrowing caused by the high permeability and low pressure of the gravel layer. The flexible temporary plugging agent is a polyol, which has multiple effects. It is a colorless and transparent liquid at room temperature, but a white emulsion at the bottom of the well. It can form a protective film on the wellbore, exerting a plugging effect while also improving wellbore lubrication. The granular plugging agent, sulfonated asphalt, is made by modifying and sulfonating asphalt. Because sulfonated asphalt contains sulfonic acid groups... The hydration effect is strong. When adsorbed on the shale interface, it can prevent the hydration and dispersion of shale particles, thus preventing collapse. At the same time, the water-insoluble parts (colloids and bitumen) can fill pore throats and fractures, acting as a sealant, and can cover the shale interface, improving mud cake quality. Its oleophilic groups can form a hydrophobic film on the well wall, achieving wetting reversal and preventing filtrate from penetrating into the formation. Sulfonated phenolic resin introduces sulfonic acid groups into the benzene ring unit, and the benzene rings are linked by carbon atoms, enabling it to resist high temperatures. Because sodium sulfonate groups are introduced at the ortho and para positions of the phenyl hydroxyl group, its strong hydration effect and high bond energy of associated water solve its water solubility problem, which determines its resistance to salt and calcium, and its ability to reduce water loss under high temperature and pressure. It has good properties such as good water loss reduction under high temperature and pressure, salt resistance, and reduced mud cake friction coefficient, which play an important role in consolidating the well wall, preventing collapse, and preventing sticking.

[0034] 3. This invention uses ultrafine fibers, specifically the FORTA brand ultrafine fibers, which have good tensile strength, are easily dispersed in liquids without increasing the viscosity of the system, and have good sand-carrying and plugging capabilities.

[0035] 4. The water-based drilling fluid of the present invention has a fast drilling speed, low torque, and good wellbore cleaning effect in gravel formations, and the tripping and casing running processes are smooth, saving a lot of non-productive time.

[0036] 5. In the preparation of the water-based drilling fluid of the present invention, the first addition of a pH adjuster is beneficial to the dispersion and preservation of the filtration loss reducer. The addition of a long-chain filtration loss reducer and a thickener and stirring and standing are beneficial to full hydration and to give full play to the suspension effect of the thickener. Next are the plugging material, weighting agent, etc., which can be suspended in the system and further dispersed. Finally, the ultrafine fiber does not need to be dissolved, just stirred evenly.

[0037] 6. The drilling fluid system of this invention is simple to prepare and maintain, requiring no additional auxiliary equipment or costs, and has good application prospects in oil fields in eastern Ecuador. Detailed Implementation

[0038] In order to make the objects, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be described clearly and completely below in conjunction with the embodiments of the present application. Obviously, the described embodiments are some but not all of the embodiments of the present application.

[0039] The superfine fiber, polymeric alcohol, sulfonated asphalt, sulfonated phenolic resin, vegetable oil lubricant, low viscosity anionic cellulose, high viscosity anionic cellulose, xanthan gum, magnesium oxide, and limestone powder described in the present application are all commercially available products.

[0040] Embodiment 1

[0041] The present embodiment provides a water-based drilling fluid suitable for gravel layer well section in eastern Ecuador, which is composed of superfine fiber, flexible temporary plugging agent, particulate plugging agent, anti-sloughing agent, vegetable oil lubricant, pH regulator, fluid loss additive, viscosity enhancer, weighting agent and water, wherein the weight percentage of each component is as follows: superfine fiber 0.1-0.3%, flexible temporary plugging agent 0.5-0.8%, particulate plugging agent 0.5-1.0%, anti-sloughing agent 0.3-1.0%, vegetable oil lubricant 0.2-1.0%, pH regulator 0.2-0.5%, fluid loss additive 0.6-1.5%, viscosity enhancer 0.5-1.2%, weighting agent 5.0-20.0%, and water makes up the rest.

[0042] Embodiment 2

[0043] Based on embodiment 1, a water-based drilling fluid suitable for gravel layer well section in eastern Ecuador is provided, wherein the weight percentage of each component is as follows: superfine fiber 0.2-0.3%, flexible temporary plugging agent 0.6-0.7%, particulate plugging agent 0.6-0.9%, anti-sloughing agent 0.4-0.8%, vegetable oil lubricant 0.3-0.7%, pH regulator 0.3-0.4%, fluid loss additive 0.8-1.2%, viscosity enhancer 0.8-1.0%, weighting agent 10.0-15.0%, and water makes up the rest.

[0044] Embodiment 3

[0045] Based on embodiment 1 or 2, a water-based drilling fluid suitable for gravel layer well section in eastern Ecuador is provided, wherein the weight percentage of each component is as follows: superfine fiber 0.2%, flexible temporary plugging agent 0.6%, particulate plugging agent 0.8%, anti-sloughing agent 0.7%, vegetable oil lubricant 0.5%, pH regulator 0.3%, fluid loss additive 1.0%, viscosity enhancer 0.9%, weighting agent 12%, and water 83%.

[0046] In the above embodiments: preferably, the superfine fiber is polyamide synthetic fiber with a filament fineness of 0.5 dtex and a filament length of 1-1.5 cm, and the manufacturer is FORTA company.

[0047] Preferably, the flexible bridging agent is polymeric alcohol, produced by Jingzhou Chengxue Industry Co., Ltd.

[0048] Preferably, the particle bridging agent is oil field industrial sulfonated asphalt SFT, black powder, produced by Zhengzhou Jingyuan Mud Material Co., Ltd.

[0049] Preferably, the anti-sloughing agent is sulfonated phenolic resin (SMP), which is composed of SMP-1 and SMP-2 in a ratio of 1:1, produced by Hebei Yanxing Chemical Co., Ltd.

[0050] Preferably, the vegetable oil lubricant is a common vegetable oil-based drilling fluid extreme pressure lubricant, which is a light brown transparent liquid, produced by Shandong Deshun Source Petroleum Technology Co., Ltd.

[0051] Preferably, the pH regulator is magnesium oxide, white powder, produced by the local INCOPET company in Ecuador.

[0052] Preferably, the fluid loss additive is low-viscosity anionic cellulose, which is a water-soluble cellulose ether derivative prepared by chemical modification of natural cellulose, with low degree of substitution, produced by Changqing Chemical Group.

[0053] Preferably, the viscosity enhancer is high-viscosity anionic cellulose and xanthan gum, wherein the weight ratio of high-viscosity anionic cellulose to xanthan gum is 1:1 to 1.5; the high-viscosity anionic cellulose, usually in the form of its sodium salt, is produced by Zibo Lianji Chemical Co., Ltd., and the molecular formula of xanthan gum is (C 35 H 49 O 29 )n, which is an extracellular microbial polysaccharide produced by Xanthomonas fermentation of sugars, has a special structure of macromolecules and colloidal properties, and is a good viscosity enhancer material, produced by Zibo Zhongxuan Biochemical Co., Ltd.

[0054] Preferably, the weighting agent is limestone powder, which is composed of 200-mesh limestone powder and 325-mesh limestone powder in a weight ratio of 1:1, and the ingredient is calcium carbonate, purchased locally in Ecuador.

[0055] In the above embodiment, the preparation method of the water-based drilling fluid suitable for the gravel layer well section in the eastern part of Ecuador includes the following steps:

[0056] Step 1, according to the above weight percentage, prepare each component by mixing ultra-fine fibers, flexible bridging agent, particle bridging agent, anti-sloughing agent, vegetable oil lubricant, pH regulator, fluid loss additive, viscosity enhancer, weighting agent, and water to make up the remaining amount, and then put the calculated amount of water into a slurry preparation tank;

[0057] Step 2, add the above weight percentage of pH regulator into the mixing tank, fully stir and mix evenly;

[0058] Step 3, add the above weight percentage of fluid loss additive into the mixing tank, fully stir and mix evenly;

[0059] Step 4, add the above weight percentage of viscosity enhancer into the mixing tank, fully stir and mix evenly, stand for 24 hours, fully hydrate;

[0060] Step 5, add the above weight percentage of particle plugging agent into the mixing tank, fully stir and mix evenly;

[0061] Step 6, add the above weight percentage of flexible bridging agent into the mixing tank, fully stir and mix evenly;

[0062] Step 7, add the above weight percentage of anti-sloughing agent into the mixing tank, fully stir and mix evenly;

[0063] Step 8, add the above weight percentage of vegetable oil lubricant into the mixing tank, fully stir and mix evenly;

[0064] Step 9, add the above weight percentage of weighting agent into the mixing tank, fully stir and mix evenly;

[0065] Step 10, add the above weight percentage of ultra-fine fiber into the mixing tank, fully stir and mix evenly, to obtain a water-based drilling fluid suitable for the gravel layer well section in the eastern part of Ecuador.

[0066] Example 4

[0067] Prepare 100 kg of drilling fluid: 0.2 kg of ultra-fine fiber; 0.6 kg of flexible bridging agent polyhydric alcohol; 0.8 kg of particle plugging agent sulfonated asphalt; 0.7 kg of anti-sloughing agent sulfonated phenolic resin, wherein 0.35 kg of sulfonated phenolic resin SMP-1, 0.35 kg of sulfonated phenolic resin SMP-2, 0.5 kg of vegetable oil lubricant; 0.3 kg of pH regulator magnesium oxide, 1.0 kg of fluid loss additive low-viscosity anionic cellulose, 0.9 kg of viscosity enhancer, wherein 0.45 kg of high-viscosity anionic cellulose, 0.45 kg of xanthan gum; 12 kg of weighting agent, wherein 6.0 kg of 200 mesh limestone powder, 6.0 kg of 325 mesh limestone powder; 83.0 kg of water.

[0068] Preparation method: proportionally add pH regulator 0.3 kg, fluid loss additive 1.0 kg, viscosity enhancer 0.9 kg into 83.0 kg water in turn, mix well, stand for 24 hours, fully hydrate, then add particle plugging agent 0.8 kg, flexible bridging agent 0.6 kg, anti-sloughing agent 0.7 kg, vegetable oil lubricant 0.5 kg, weighting agent 12 kg, and super-fine fiber 0.2 kg, mix well, to obtain water-based drilling fluid suitable for gravel layer in eastern Ecuador.

[0069] Example 5

[0070] Preparation of 100 kg drilling fluid: super-fine fiber 0.1 kg; flexible bridging agent polyhydric alcohol 0.5 kg; particle plugging agent sulfonated asphalt 0.5 kg; anti-sloughing agent sulfonated phenolic resin 0.3 kg, wherein sulfonated phenolic resin SMP-1 is 0.15 kg, and sulfonated phenolic resin SMP-2 is 0.15 kg; vegetable oil lubricant 0.2 kg; pH regulator magnesium oxide 0.2 kg, fluid loss additive low-viscosity anionic cellulose 0.6 kg, viscosity enhancer 0.5 kg, wherein high-viscosity anionic cellulose is 0.25 kg, and xanthan gum is 0.25 kg; weighting agent 5.0 kg, wherein 200-mesh limestone powder is 2.5 kg, and 325-mesh limestone powder is 2.5 kg; water 92.1 kg.

[0071] Preparation method: proportionally add pH regulator 0.2 kg, fluid loss additive 0.6 kg, and viscosity enhancer 0.5 kg into 92.1 kg water in turn, mix well, stand for 24 hours, fully hydrate, then add particle plugging agent 0.5 kg, flexible bridging agent 0.5 kg, anti-sloughing agent 0.3 kg, vegetable oil lubricant 0.2 kg, weighting agent 5 kg, and super-fine fiber 0.1 kg, mix well, to obtain water-based drilling fluid suitable for gravel layer in eastern Ecuador.

[0072] Example 6

[0073] Preparation of 100 kg drilling fluid: super-fine fiber 0.3 kg; flexible bridging agent polyhydric alcohol 0.8 kg; particle plugging agent sulfonated asphalt 1.0 kg; anti-sloughing agent sulfonated phenolic resin 1.0 kg, wherein sulfonated phenolic resin SMP-1 is 0.5 kg, and sulfonated phenolic resin SMP-2 is 0.5 kg; vegetable oil lubricant 1.0 kg; pH regulator magnesium oxide 0.5 kg, fluid loss additive low-viscosity anionic cellulose 1.5 kg, viscosity enhancer 1.2 kg, wherein high-viscosity anionic cellulose is 0.6 kg, and xanthan gum is 0.6 kg; weighting agent 20.0 kg, wherein 200-mesh limestone powder is 10.0 kg, and 325-mesh limestone powder is 10.0 kg; water 72.7 kg.

[0074] Preparation method: pH regulator 0.5 kg, filtrate reducer 1.5 kg, tackifier 1.2 kg were added into 72.7 kg water in proportion, fully stirred and mixed uniformly, and then left for 24 hours, fully hydrated, and then added particle blocking agent 1.0 kg, flexible bridging agent 0.8 kg, anti-sloughing agent 1.0 kg, vegetable oil lubricant 1.0 kg, weighting agent 20 kg, and super-fine fiber 0.3 kg, fully stirred and mixed uniformly to obtain a water-based drilling fluid suitable for gravel layer well section in eastern Ecuador.

[0075] Example 7

[0076] Preparation of 100 kg drilling fluid: super-fine fiber 0.15 kg; flexible bridging agent polyhydric alcohol 0.55 kg; particle blocking agent sulfonated asphalt 0.6 kg; anti-sloughing agent sulfonated phenolic resin 0.6 kg, wherein sulfonated phenolic resin SMP-1 is 0.3 kg, and sulfonated phenolic resin SMP-2 is 0.3 kg; vegetable oil lubricant 0.4 kg; pH regulator magnesium oxide 0.3 kg, filtrate reducer low-viscosity anionic cellulose 0.8 kg, tackifier 0.8 kg, wherein high-viscosity anionic cellulose is 0.45 kg, and xanthan gum is 0.35 kg; weighting agent 10 kg, wherein 200 mesh limestone powder is 5.0 kg, and 325 mesh limestone powder is 5.0 kg; water 85.8 kg.

[0077] Preparation method: pH regulator 0.3 kg, filtrate reducer 0.8 kg, tackifier 0.8 kg were added into 85.8 kg water in proportion, fully stirred and mixed uniformly, and then left for 24 hours, fully hydrated, and then added particle blocking agent 0.6 kg, flexible bridging agent 0.55 kg, anti-sloughing agent 0.6 kg, vegetable oil lubricant 0.4 kg, weighting agent 10 kg, and super-fine fiber 0.15 kg, fully stirred and mixed uniformly to obtain a water-based drilling fluid suitable for gravel layer well section in eastern Ecuador.

[0078] Example 8

[0079] Preparation of 100 kg drilling fluid: super-fine fiber 0.25 kg; flexible bridging agent polyhydric alcohol 0.75 kg; particle blocking agent sulfonated asphalt 0.9 kg; anti-sloughing agent sulfonated phenolic resin 0.85 kg, wherein sulfonated phenolic resin SMP-1 is 0.425 kg, and sulfonated phenolic resin SMP-2 is 0.425 kg; vegetable oil lubricant 0.8 kg; pH regulator magnesium oxide 0.4 kg, filtrate reducer low-viscosity anionic cellulose 1.3 kg, tackifier 1.0 kg, wherein high-viscosity anionic cellulose is 0.6 kg, and xanthan gum is 0.4 kg; weighting agent 16 kg, wherein 200 mesh limestone powder is 8.0 kg, and 325 mesh limestone powder is 8.0 kg; water 77.75 kg.

[0080] Preparation method: proportionally add pH regulator 0.4 kg, filtrate reducer 1.3 kg, tackifier 1.0 kg into 77.75 kg water in sequence, fully stir and mix uniformly, stand for 24 hours, fully hydrate, then add granular plugging agent 0.9 kg, flexible temporary plugging agent 0.75 kg, anti-sloughing agent 0.85 kg, vegetable oil lubricant 0.8 kg, weighting agent 16 kg, and superfine fiber 0.25 kg, fully stir and mix uniformly, to obtain a water-based drilling fluid suitable for gravel layer well section in eastern Ecuador.

[0081] The water-based drilling fluids prepared in examples 4-8 are subjected to performance test by using the method common in the art, and the test results are shown in Table 1.

[0082] Table 1 Performance test results of water-based drilling fluids prepared in examples 4-8

[0083]

[0084] As shown in Table 1, the water-based drilling fluids of examples 4-8 have moderate viscosity, adjustable density, thin mud cake, excellent filtrate reduction effect, and good lubricating performance, which meet the requirements of field construction.

[0085] Application example

[0086] Well PRHA-33 in Ecuador is a directional production well in PARAHUACU oilfield, with a total drilling depth of 4005.7 m and a maximum hole deviation angle of 49.32°. The drilling fluid system prepared in example 1 is used in the second opening of 12.25” borehole, and a single drill bit drills through three gravel layers with a total length of 213.1 m, with an average mechanical drilling speed of 8.3 m / h. After drilling, the drill bit is pulled out smoothly without resistance, and a 9.625” casing is lowered to the bottom at one time. Well PRHBA-06 in the same block was previously provided with mud service by other companies, using a common polymer system, with a maximum hole deviation angle of 31.08°. A single drill bit cannot drill through the gravel layer, with an average mechanical drilling speed of only 6.6 m / h. During the drilling process, the gravel layer section is pumped and the hole is opened several times, resulting in non-production time.

[0087] Therefore, all other examples obtained by those of ordinary skill in the art based on the examples in the present application without creative labor fall within the scope of protection of the present application.

Claims

1. A water-based drilling fluid suitable for gravel formations in eastern Ecuador, characterized in that, The water-based drilling fluid includes ultrafine fibers, flexible temporary plugging agent, granular plugging agent, anti-collapse agent, vegetable oil lubricant, pH adjuster, filtration loss reducer, viscosity increaser, weighting agent and water; The weight percentage of each component is as follows: microfiber 0.1~0.3%, flexible temporary plugging agent 0.5~0.8%, granular plugging agent 0.5~1.0%, anti-collapse agent 0.3~1.0%, vegetable oil lubricant 0.2~1.0%, pH adjuster 0.2~0.5%, filtration loss reducer 0.6~1.5%, thickener 0.5~1.2%, weighting agent 5.0~20.0%, water to make up the balance; The microfiber is a polyamide synthetic fiber with a single filament fineness of 0.5 dtex and a single filament length of 1-1.5 cm; The flexible temporary plugging agent is a polymeric alcohol; The particulate plugging agent is industrial sulfonated asphalt SFT; The anti-collapse agent is sulfonated phenolic resin, and the weight ratio of SMP-1 to SMP-2 in the sulfonated phenolic resin is 1:

1. The vegetable oil lubricant is a vegetable oil-based drilling fluid extreme pressure lubricant. The pH adjuster is magnesium oxide; The filtration loss reducer is low-viscosity polyanionic cellulose; The thickener comprises high-viscosity polyanionic cellulose and xanthan gum, with a weight ratio of 1:1 to 1.

5. The weighting agent comprises 200-mesh limestone powder and 325-mesh limestone powder in a weight ratio of 1:

1.

2. The water-based drilling fluid suitable for gravel formations in eastern Ecuador according to claim 1, characterized in that, The weight percentages of each component are as follows: 0.2-0.3% microfiber, 0.6-0.7% flexible temporary plugging agent, 0.6-0.9% granular plugging agent, 0.4-0.8% anti-collapse agent, 0.3-0.7% vegetable oil lubricant, 0.3-0.4% pH adjuster, 0.8-1.2% filtration loss reducer, 0.8-1.0% thickener, 10.0-15.0% weighting agent, and water to make up the balance.

3. A water-based drilling fluid suitable for gravel formation sections in eastern Ecuador according to claim 1 or 2, characterized in that, The weight percentages of each component are as follows: 0.2% microfiber, 0.6% flexible temporary plugging agent, 0.8% particulate plugging agent, 0.7% anti-collapse agent, 0.5% vegetable oil lubricant, 0.3% pH adjuster, 1.0% filtration loss reducer, 0.9% thickener, 12% weighting agent, and 83% water.

4. A method for preparing a water-based drilling fluid suitable for gravel formations in eastern Ecuador, characterized in that, Includes the following steps: Step 1: Prepare the following components: 0.1-0.3% ultrafine fiber, 0.5-0.8% flexible temporary plugging agent, 0.5-1.0% granular plugging agent, 0.3-1.0% anti-collapse agent, 0.2-1.0% vegetable oil lubricant, 0.2-0.5% pH adjuster, 0.6-1.5% filtration loss reducer, 0.5-1.2% thickener, 5.0-20.0% weighting agent, and water to make up the balance. Pour the calculated amount of water into the mixing tank. The ultrafine fiber should have a single filament fineness of 0.5 dtex and a single filament length of 1-1.5 cm. Polyamide synthetic fiber; flexible temporary plugging agent is polyol; particulate plugging agent is industrial sulfonated asphalt (SFT); anti-collapse agent is sulfonated phenolic resin, in which the weight ratio of SMP-1 to SMP-2 is 1:1; vegetable oil lubricant is vegetable oil-based drilling fluid extreme pressure lubricant; pH adjuster is magnesium oxide; filtration loss reducer is low-viscosity polyanionic cellulose; viscosity enhancer includes high-viscosity polyanionic cellulose and xanthan gum, in a weight ratio of 1:1 to 1.5; weighting agent includes 200-mesh limestone powder and 325-mesh limestone powder, in a weight ratio of 1:

1. Step 2: Add 0.2-0.5% pH adjuster to the mixing tank and stir thoroughly until evenly mixed; Step 3: Add 0.6-1.5% of filtration loss reducer to the mixing tank and stir thoroughly until evenly mixed; Step 4: Add 0.5-1.2% thickener to the mixing tank, stir thoroughly and mix evenly, let stand for 24 hours to fully hydrate; Step 5: Add 0.5-1.0% granular sealing agent to the slurry mixing tank and stir thoroughly until evenly mixed; Step 6: Add 0.5-0.8% of flexible temporary plugging agent to the slurry mixing tank and stir thoroughly until evenly mixed; Step 7: Add 0.3-1.0% of anti-collapse agent to the slurry mixing tank and stir thoroughly until evenly mixed; Step 8: Add 0.2-1.0% vegetable oil lubricant to the mixing tank and stir thoroughly until evenly mixed; Step 9: Add 5.0-20.0% weighting agent to the mixing tank and stir thoroughly until evenly mixed; Step 10: Add 0.1-0.3% of ultrafine fiber to the mixing tank and stir thoroughly to obtain a water-based drilling fluid suitable for gravel layer well sections in eastern Ecuador.

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