CN104694092B - A kind of shale gas horizontal well strengthens water-base drilling fluid and its application of the borehole wall - Google Patents

Abstract

The invention relates to a water-based drilling fluid for strengthening the well wall of a shale gas horizontal well and an application thereof. The water-based drilling fluid comprises the following components in parts by weight: water, 100 parts; clay, 0-5 parts; micro-nano particles Plugging agent, 0.5-3 parts; chemical plugging agent, 0.5-3 parts; viscosifier, 0.1-2 parts; fluid loss reducer, 1-5 parts; coating inhibitor, 0.05-2 parts; polyamine Inhibitor, 0.1-3 parts; lubricant, 1-5 parts; alkalinity regulator, 0.1-1 part, inorganic salt, 2-25 parts, weighting agent, 0-200 parts. The micro-nano particle plugging agent and the chemical plugging agent in the water-based drilling fluid for strengthening the well wall of shale gas horizontal wells according to the present invention have a synergistic effect of strengthening the well wall, and can effectively block shale micropores and fractures to prevent pressure It can also significantly improve the efficiency of mud shale membrane, and help to play the role of chemical activity balance and anti-collapse.

Description

A kind of water-based drilling fluid for shale gas horizontal well strengthening borehole wall and its application

technical field

The invention relates to a shale gas horizontal well wall strengthening drilling fluid and its application, in particular to a high-performance water-based drilling fluid that can replace oil-based drilling fluid.

Background technique

The recoverable reserves of China's shale gas resource prediction technology reach 10.3×10 ¹² to 47.0×10 ¹² m ³ , which has good prospects for exploration and development. Once successful large-scale exploration and development can effectively alleviate the contradiction between oil and gas supply and demand in China, so shale gas Gas exploration and development has become a major national strategy during the "Twelfth Five-Year Plan".

At this stage, horizontal drilling technology is one of the core technologies for shale gas development and is widely used in shale gas development drilling. In order to increase production by hydraulic fracturing in the later stage, horizontal well sections are mostly distributed in formations with natural fractures, and drilled along the direction of the minimum horizontal principal stress. During the drilling process, the drilling fluid filtrate is easily invaded into the shale, which can cause serious wellbore instability. Therefore, the wellbore stability has become one of the key technical problems in the development of shale gas resources in horizontal wells.

Oil-based drilling fluid has the advantages of excellent inhibition, lubricity, and high-temperature stability. It is currently the preferred drilling fluid for shale gas horizontal well sections. However, its preparation cost is high and there are environmental protection problems. Well leakage problem will cause great economic loss. Water-based drilling fluids have the advantages of low cost and environmental friendliness. However, in the drilling of shale gas horizontal wells, conventional water-based drilling fluids are difficult to solve the problems of wellbore instability and wellbore leakage in horizontal wells, and there are shale inhibition properties. Insufficient extreme pressure lubrication performance and other shortcomings, it is difficult to meet the engineering technical requirements of shale gas horizontal well drilling.

Contents of the invention

Aiming at the deficiencies of the prior art, the present invention provides a water-based drilling fluid for strengthening the borehole wall of a shale gas horizontal well and its application. wall effect. The invention mainly mixes a novel shale micro-nano particle plugging agent with other drilling fluid ingredients according to the performance requirements of the drilling fluid to obtain a water-based drilling fluid for strengthening well walls of shale gas horizontal wells.

Technical scheme of the present invention is as follows:

A water-based drilling fluid for strengthening the borehole wall of a shale gas horizontal well, comprising the following components by weight:

water, 100 parts;

Clay, 0-5 parts;

Micro-nano particle blocking agent, 0.5-3 parts;

Chemical blocking agent, 0.5-3 parts;

Tackifier, 0.1-2 parts;

Filtrate reducer, 1 to 5 parts;

Polyamine inhibitor, 0.1 to 3 parts;

Coating inhibitor, 0.05 to 2 parts;

Lubricant, 1-5 parts;

Alkalinity regulator, 0.1 to 1 part;

Inorganic salt, 2-25 parts;

Weighting agent, 0-200 parts;

The micro-nano particle blocking agent is a product of emulsion polymerization of acrylic or methacrylic monomers and vinyl monomers.

According to the present invention, preferably, the particle size distribution of the micro-nano particle plugging agent is D10≤100nm, D50≤165nm, D90≤260nm;

Preferably, the acrylate or methacrylate monomer is one of methyl acrylate, ethyl acrylate, n-butyl acrylate, methyl methacrylate, ethyl methacrylate, and n-butyl methacrylate a mixture of two or more kinds;

Preferably, the vinyl monomer is one or a mixture of two or more of vinyl chloride, styrene, vinyl acetate, and sodium p-vinylbenzenesulfonate.

According to the present invention, preferably, the micro-nano particle plugging agent is prepared according to the following steps:

Add acrylate or methacrylate monomers, vinyl monomers, and cosolvents into a reaction kettle filled with water, and stir at high speed to form a stable dispersion system. The water, cosolvents, acrylate or methacrylate monomers , The mass ratio of vinyl monomers is 150-300:80-200:10-30:5-20; the closed reaction kettle is heated in a water bath, and the polymerization reaction is initiated by adding an initiator. 0.2-0.8%; control the reaction time for 2-4 hours, after the reaction is over, cool naturally to obtain the shale micro-nano particle plugging agent for water-based drilling fluid;

Further preferably, the cosolvent is methanol, ethanol, acetone, glycerol, isopropanol or a mixture of two or more; the initiator is potassium persulfate, azobisisobutyronitrile, Azobisisoheptanonitrile, cumene hydroperoxide, and benzoyl peroxide, or a mixture of two or more.

According to the present invention, the micro-nano particle plugging agent is prepared by soap-free emulsion polymerization, and its latex particles have good monodispersity and water resistance, and the surface is clean; when added to water-based drilling fluid, avoid water Foaming problem of base drilling fluid. Moreover, the micro-nanoparticle plugging agent has good monodispersity, the average particle size distribution is about 160nm, and has strong stability. It can be uniformly dispersed in fresh water, fresh water aggravated, and brine drilling fluid, and can be deformed to plug shale Nano-pores and micro-cracks play a role in retarding pressure transmission and filtrate intrusion, and enhance the stability of shale well walls. In addition, the micro-nano particle plugging agent has little effect on the rheological properties of the drilling fluid, and is beneficial to reduce the fluid loss of the drilling fluid. The mechanism of action is as follows: the micro-nano particle plugging agent is a deformable polymer particle of micro-nano scale, which can enter into the nano-pores and micro-cracks of shale, and through adsorption, bridging and deformable filling, it continuously settles, fills, Compaction forms a continuous tight sealing layer inside the shale, plays a role in retarding pressure transmission and filtrate intrusion, and enhances the stability of the shale well wall.

According to the present invention, preferably, the clay is one or a mixture of two or more of bentonite, sepiolite, attapulgite and palygorskite. The above clay can increase the viscosity and shear force of the water-based drilling fluid, form a dense mud cake, and reduce the filtration loss of the water-based drilling fluid.

According to the present invention, preferably, the chemical blocking agent is one or a mixture of two or more of sodium silicate, potassium silicate, polyaluminum, and humic acid-aluminum complex. The above-mentioned chemical plugging agent can be chemically consolidated inside the shale and play a role of chemical wall consolidation.

According to the present invention, the micro-nano particle plugging agent and the chemical plugging agent have a synergistic effect of strengthening the borehole wall, which can not only effectively plug the micro-pores and fractures of shale to prevent pressure transmission, but also significantly improve the efficiency of the shale membrane. It helps to play the role of chemical activity balance and anti-collapse.

According to the present invention, preferably, the thickener is one or a mixture of two or more of high-purity biopolymer, hydroxyethyl cellulose, high-viscosity carboxymethyl cellulose, and high-viscosity polyanion cellulose. The above-mentioned viscosifier can effectively increase the viscosity and shear force of the water-based drilling fluid in a high-salinity environment, and improve the rheology of the water-based drilling fluid, so as to ensure clean wellbore and safe drilling.

According to the present invention, preferably, the fluid loss control agent is one or a mixture of two or more of cationic starch, low-viscosity polyanionic cellulose, sulfonated pitch, and sulfonated phenolic resin. Adding the above-mentioned fluid loss reducer can form a low-permeability, flexible, thin and dense mud cake on the well wall, and reduce the fluid loss of water-based drilling fluid as much as possible.

According to the present invention, preferably, the polyamine inhibitor is one or a mixture of two or more of polyamines, polyetheramines, alkylamines, and quaternary amines. Polyamine inhibitors can form multi-point adsorption on the clay surface through electrostatic adsorption, hydrogen bonding, etc., weaken the electrostatic repulsion between the clay surfaces and the repulsion of the surface hydration film, and inhibit the hydration of the shale surface.

According to the present invention, preferably, the coating inhibitor is one or a mixture of two or more of cationic polyacrylamide, polyacrylamide, potassium polyacrylate, and zwitterionic polymer. The above-mentioned coating inhibitor and the polyamine inhibitor act synergistically to enhance the inhibitory property of the drilling fluid.

According to the present invention, preferably, the lubricant is one or a mixture of two or more of solid lubricants, extreme pressure lubricants, and water-based lubricants. Adding the above-mentioned lubricants can improve the extreme-pressure lubricity of the drilling fluid and meet the requirements of reducing friction and drag in extended-reach horizontal wells.

According to the present invention, preferably, the alkalinity regulator is one or a mixture of two or more of sodium hydroxide, potassium hydroxide and calcium oxide. On the one hand, the above-mentioned alkalinity regulator can keep the pH value of the water-based drilling fluid above 10, and can also ensure that the chemical plugging agent is in a dissolved state in the drilling fluid.

According to the present invention, preferably, the inorganic salt is one or a mixture of two or more of sodium chloride, potassium chloride, calcium chloride and magnesium chloride.

According to the present invention, preferably, the weighting agent is one or a mixture of two or more of barite, hematite, trimanganese tetraoxide, calcium chloride, sodium formate, and potassium formate. The amount of weighting agent can be determined according to the density requirement of the drilling fluid. The water-based drilling fluid for strengthening the borehole wall of a shale gas horizontal well of the present invention can be prepared by a conventional preparation method.

According to the present invention, the application of the above-mentioned water-based drilling fluid for strengthening the borehole wall of a shale gas horizontal well to enhance the stability of the borehole wall.

Compared with the prior art, the present invention has the following advantages:

1. The micro-nano particle plugging agent and the chemical plugging agent in the water-based drilling fluid for strengthening the borehole wall of shale gas horizontal wells of the present invention have a synergistic effect of strengthening the borehole wall, which can effectively seal the shale micropore fracture resistance Slow pressure transmission can also significantly improve the efficiency of mud shale membrane, and help to play the role of chemical activity balance and anti-collapse.

2. The water-based drilling fluid for strengthening wellbore walls of shale gas horizontal wells of the present invention has excellent plugging properties, inhibition and lubricity, and its comprehensive performance is equivalent to that of oil-based drilling fluids, and is low in cost and environmentally friendly.

3. The water-based drilling fluid for strengthening well walls of shale gas horizontal wells of the present invention can solve the problem of well wall instability in shale gas horizontal well sections, and has simple configuration and convenient maintenance.

Detailed ways

The present invention will be further described below through specific examples, but not limited thereto.

The raw materials used in the examples are conventional commercially available products unless otherwise specified.

Example 1

A water-based drilling fluid for strengthening the borehole wall of a shale gas horizontal well that is not aggravated includes the following components by weight:

Fresh water: 100 parts; bentonite: 1.0 parts; micronano particle blocking agent: 1.0 parts; chemical blocking agent: 2.0 parts; viscosifier: 0.3 parts; cationic starch: 1.5 parts; cationic polyacrylamide: 0.1 parts; Strong amine inhibitor: 3.0 parts; extreme pressure lubricant: 1.0 part; sodium hydroxide: 0.1 part; sodium chloride: 20 parts.

The micro-nano particle plugging agent is prepared as follows:

Add 200mL of distilled water to a reaction kettle equipped with a stirrer, a thermometer and a heating device, add 100mL of acetone, 12.3g of methyl methacrylate, and 9.6g of styrene while stirring, and stir at a high speed of 1500r/min to form a stable dispersion system. Heating to a temperature of 70°C, adding 0.08 g of potassium persulfate, reacting for 2.5 hours, and cooling naturally.

The chemical blocking agent is sodium silicate, the thickening agent is hydroxyethyl cellulose, and the strong polyamine inhibitor is polyetheramine.

After the above components are mixed, stir at a high speed under normal temperature and pressure for 30 minutes.

Example 2

The preparation density is 1.2g/cm ^The water-based drilling fluid of the shale gas horizontal well strengthening borehole wall, comprises the following components by weight:

Fresh water: 100 parts; bentonite: 1.0 parts; micro-nano particle blocking agent: 1.5 parts; chemical blocking agent: 2.0 parts; viscosifier: 0.2 parts; low-viscosity polyanionic cellulose: 1.5 parts; parts; strong polyamine inhibitor: 3.0 parts; extreme pressure lubricant: 2.0 parts; sodium hydroxide: 0.1 parts; sodium chloride: 20 parts; barite: 30 parts.

The micro-nano particle plugging agent is prepared as follows:

Add 300mL of distilled water to a reaction kettle equipped with a stirrer, a thermometer and a heating device, add 150mL of acetone, 16.7g of n-butyl acrylate, and 11.2g of vinyl acetate while stirring, and stir at a high speed of 1000r/min to form a stable dispersion system. Heating to a temperature of 85°C, adding 0.12 g of azobisisoheptanonitrile, reacting for 3.5 hours, and cooling naturally.

The chemical blocking agent is polyaluminium, the thickening agent is high-viscosity carboxymethyl cellulose, and the strong inhibitor of polyamine is octadecylamine.

After the above components are mixed, stir at a high speed under normal temperature and pressure for 30 minutes.

Example 3

Prepare the water-based drilling fluid with a density of 2.0g/cm ³ for strengthening the borehole wall of a shale gas horizontal well, including the following components by weight:

Fresh water: 100 parts; bentonite: 1.0 parts; micro-nano particle plugging agent: 2.0 parts; chemical plugging agent: 2.0 parts; viscosifier: 0.1 parts; sulfonated bitumen: 2.5 parts; Strong polyamine inhibitor: 2.0 parts; extreme pressure lubricant: 2.0 parts; solid lubricant: 1.0 parts; sodium hydroxide: 0.1 parts; potassium chloride: 5.0 parts; compound formate: 70 parts; barite: 100 copies.

The micro-nano particle plugging agent is prepared as follows:

Add 250mL of distilled water to a reaction kettle equipped with a stirrer, a thermometer and a heating device, add 130mL of isopropanol, 12.3g of ethyl methacrylate, and 9.6g of styrene while stirring, and stir at a high speed of 2000r/min to form a stable dispersion system , heated in a water bath to a temperature of 90°C, added 0.10 g of azobisisobutyronitrile, reacted for 2.0 h, and cooled naturally.

The chemical blocking agent is humic acid-aluminum complex, the thickening agent is high-viscosity polyanion cellulose, and the strong inhibitor of polyamine is quaternary amine.

After the above components are mixed, stir at a high speed under normal temperature and pressure for 30 minutes.

Example 4

A water-based drilling fluid for strengthening the borehole wall of a shale gas horizontal well, the components in parts by weight of raw materials are the same as those in Example 1, except that:

Use attapulgite instead of bentonite, sulfonated phenolic resin instead of cationic starch, and polyacrylamide instead of cationic polyacrylamide; the chemical blocking agent is potassium silicate, and the tackifier is high-viscosity polyanion fiber white.

Example 5

A water-based drilling fluid for strengthening the borehole wall of a shale gas horizontal well, the components in parts by weight of raw materials are the same as those in Example 2, except that:

Without adding bentonite, cationic starch is used instead of low-viscosity polyanionic cellulose, potassium polyacrylate is used instead of polyacrylamide, and hematite is used instead of barite; the chemical blocking agent is sodium silicate, and the viscosity-increasing The agent is hydroxyethyl cellulose.

Example 6

A water-based drilling fluid for strengthening the borehole wall of a shale gas horizontal well, the components in parts by weight of raw materials are the same as those in Example 3, except that:

Use sepiolite instead of bentonite, cationic starch instead of sulfonated pitch, potassium hydroxide instead of sodium hydroxide, sodium chloride instead of potassium chloride, and manganese tetraoxide instead of barite.

The effects of Examples 1-3 will be described below.

1. Rheological fluid loss performance evaluation of drilling fluid

Using the water-based drilling fluid field testing procedure (GB/T 16783-1997), using a six-speed viscometer and a medium-pressure fluid loss meter, the rheology and fluid loss of different examples were tested before and after 120°C/16h hot roll aging. The test results are shown in Table 1. It can be seen from Table 1 that before and after 120°C/16h hot rolling aging, the viscosity and shear force of the drilling fluids in Examples 1-3 are moderate, the API filtration loss is low, and the low-shear viscosity is high, and the shear thinning property is strong , which is conducive to the drilling fluid carrying rock in the horizontal well section.

Table 1 Test results of rheological fluid loss performance of drilling fluid

Note: AV is the apparent viscosity of the drilling fluid; PV is the plastic viscosity of the drilling fluid; YP is the dynamic shear force of the drilling fluid; YP/PV is the dynamic plastic ratio of the drilling fluid; Speed viscometer reading; API is the pressure loss of drilling fluid.

2. Evaluation of drilling fluid plugging and anti-collapse performance

Using the Permeability Plugging Apparatus, the ultra-low permeability sand disk (400mD) was selected as the shale simulation core, and the sealing performance of the drilling fluid in Examples 1-3 was evaluated under the condition of 120°C/7.0MPa. Blocking and anti-collapse performance, the test results are shown in Table 2. It can be seen from Table 2 that the above-mentioned Example 1, Example 2 and Example 3 all have good plugging and anti-collapse performance, and the static fluid loss rate is less than 0.9mL/min ² . The filtration loss is the lowest, and its plugging and anti-collapse performance is the best.

Table 2. Test results of plugging and anti-collapse performance of drilling fluid

3. Evaluation of drilling fluid's ability to inhibit shale hydration dispersion

The shale rolling dispersion test was used to evaluate the performance of the drilling fluids in Examples 1-3 in inhibiting shale hydration and dispersion, and to compare the performance with oil-based drilling fluids. The oil-based drilling fluid formula is as follows: 5# white oil + 2.0% main emulsifier + 1.5% calcium oxide + 0.5% viscosifier + 3.0% wetting agent + 1.5% cutting agent + 4.0% organic soil + 2.0% filter reducer Lost dose.

The shale rock samples used in the experiment are formation cuttings at a well depth of 1800-1850 m in the MHZ layer of an oilfield. The test results are shown in Table 3. It can be seen from Table 3 that the rolling recovery rates of cuttings in Example 1, Example 2 and Example 3 are equivalent to those of oil-based drilling fluid, indicating that it has excellent performance in inhibiting shale hydration and dispersion.

Table 3 Test results of inhibition performance of different drilling fluids

test formula clear water oil-based drilling fluid Example 1 Example 2 Example 3 Recovery rate/(%) 8.90 92.88 92.03 92.81 92.55

4. Evaluation of drilling fluid lubrication performance

The drilling fluid lubricity of Examples 1-3 was evaluated using a drilling fluid extreme pressure lubricating instrument. And compare the performance with oil-based drilling fluid. The oil-based drilling fluid formula is as follows: 5# white oil + 2.0% main emulsifier + 1.5% calcium oxide + 0.5% viscosifier + 3.0% wetting agent + 0.5% cutting agent + 4.0% organic soil + 1.5% filter reducer Lost agent + 30% barite. The test results are shown in Table 4.

It can be seen from Table 4 that the extreme pressure lubrication coefficients of the above-mentioned Examples 1, 2 and 3 are all close to those of oil-based drilling fluids, indicating that they have good drilling fluid lubrication properties and fully meet the requirements of horizontal well drilling operations.

Table 4 Test results of inhibition performance of different drilling fluids

test formula clear water oil-based drilling fluid Example 1 Example 2 Example 3 Extreme pressure lubrication coefficient 0.34 0.08 0.08 0.10 0.13

The present invention is not limited to the above-mentioned preferred embodiments, and anyone should know that any modifications, equivalent replacements or improvements made within the spirit and principles of the present invention fall within the protection scope of the present invention.

Claims (7)

1. A water-based drilling fluid for strengthening the well wall of a shale gas horizontal well is characterized in that, the water-based drilling fluid for strengthening the well wall of a shale gas horizontal well is used to strengthen the stability of the well wall, and the water-based drilling The liquid contains the following components by weight: water, 100 parts; Clay, 0~5 parts; Micro-nano particle blocking agent, 0.5~3 parts; Chemical blocking agent, 0.5~3 parts; Tackifier, 0.1~2 parts; Filtrate reducer, 1~5 parts; Polyamine inhibitor, 0.1~3 parts; Coating inhibitor, 0.05~2 parts; Lubricant, 1~5 parts; Alkalinity regulator, 0.1~1 part; Inorganic salt, 2~25 parts; Weighting agent, 0~200 parts; The micro-nano particle blocking agent is a product of emulsion polymerization of acrylate or methacrylate monomers and vinyl monomers; it is prepared according to the following steps: Add acrylate or methacrylate monomers, vinyl monomers, and cosolvents into a reaction kettle filled with water, and stir at high speed to form a stable dispersion system. The water, cosolvents, acrylate or methacrylate monomers , The mass ratio of vinyl monomers is 150-300:80-200:10-30:5-20; the closed reaction kettle is heated in a water bath, and the polymerization reaction is initiated by adding an initiator. 0.2-0.8%; control the reaction time for 2-4 hours, after the reaction is over, cool naturally to obtain the shale micro-nano particle plugging agent for water-based drilling fluid; The particle size distribution of the micro-nano particle plugging agent is D10≤100 nm, D50≤165 nm, D90≤260 nm; The acrylate or methacrylate monomer is one or both of methyl acrylate, ethyl acrylate, n-butyl acrylate, methyl methacrylate, ethyl methacrylate, and n-butyl methacrylate. A mixture of more than one species; The vinyl monomer is one or a mixture of two or more of vinyl chloride, styrene, vinyl acetate, and sodium p-vinylbenzenesulfonate; The chemical blocking agent is one or a mixture of two or more of sodium silicate, potassium silicate, polyaluminum, humic acid-aluminum complex; The alkalinity regulator is one or a mixture of two or more of sodium hydroxide, potassium hydroxide and calcium oxide. 2. The water-based drilling fluid according to claim 1, wherein the clay is one or a mixture of two or more of bentonite, sepiolite, attapulgite, and palygorskite. 3. water base drilling fluid according to claim 1, is characterized in that, described viscosifier is high-purity biopolymer, hydroxyethyl cellulose, high viscosity carboxymethyl cellulose, high viscosity polyanion fiber One or a mixture of two or more of these elements; The fluid loss control agent is one or a mixture of two or more of cationic starch, low-viscosity polyanionic cellulose, sulfonated asphalt, and sulfonated phenolic resin. 4. water base drilling fluid according to claim 1, is characterized in that, described polyamine inhibitor is polyamine, polyether amine, alkylamine, quaternary amine one or two or more mixes; The coating inhibitor is one or a mixture of two or more of cationic polyacrylamide, polyacrylamide, potassium polyacrylate and zwitterionic polymer. 5. The water-based drilling fluid according to claim 1, wherein the lubricant is one or a mixture of two or more of solid lubricants, extreme pressure lubricants and water-based lubricants. 6. The water-based drilling fluid according to claim 1, wherein the inorganic salt is one or a mixture of two or more of sodium chloride, potassium chloride, calcium chloride, and magnesium chloride. 7. water base drilling fluid according to claim 1, is characterized in that, described weighting agent is one or both in barite, hematite, trimanganese tetraoxide, calcium chloride, sodium formate, potassium formate Mix the above.