Clay-phase-free calcium chloride water-based drilling fluid as well as preparation method and application thereof

Abstract

The invention relates to the technical field of oil field drilling fluids, in particular to a clay-phase-free calcium chloride water-based drilling fluid as well as a preparation method and application thereof. The clay-phase-free calcium chloride water-based drilling fluid is prepared from the following raw materials: water, calcium chloride, a pH regulator, a tackifying coating agent, a filtrate reducer, a plugging agent, an auxiliary inhibitor, an antioxidant, a lubricating corrosion inhibitor, a dispersing agent and barite. The clay-phase-free calcium chloride water-based drilling fluid disclosed by the invention not only has excellent mudstone hydration inhibition, but also avoids the use of a pH regulator which is easy to react with calcium chloride, and through the clay-phase-free formula design, the rheological stability and the filtration loss control performance are remarkably improved, and the requirements of well cleaning and well control are considered; in addition, the drilling fluid also has good lubricating and drag-reducing performance, and meets related requirements of construction of highly-inclined directional wells and horizontal wells in mudstone stratums.

Description

Technical Field

[0001] The invention relates to the technical field of oilfield drilling fluid, in particular to a clay-free calcium chloride water-based drilling fluid and a preparation method and application thereof. Background Art

[0002] Oil and gas resources are an important part of the energy sector. While accelerating the process of oil and gas development, problems and challenges are also increasing. Among them, the stability of the wellbore in the mudstone section and the slurrying of high-clay cuttings are more prominent and are the main factors restricting the increase in drilling speed. In the case of insufficient inhibition of the drilling fluid, the mudstone wellbore is prone to collapse due to expansion, causing complex accidents downhole; in addition, high-concentration mudstone cuttings pollution will cause a significant increase in drilling fluid viscosity and shearing, which will affect the pump pressure and limit the displacement on the one hand, which is not conducive to the disturbance of the cuttings bed in the high-angle and horizontal sections, affecting the wellbore cleaning effect; on the other hand, it will cause the ECD to rise and increase the risk of well leakage.

[0003] Calcium chloride drilling fluid has strong mudstone inhibition due to its high concentration of calcium ions. At the same time, high concentration of calcium chloride can also be used as a solid-free weighting agent to reduce the solid content in the drilling fluid, thereby increasing the solid capacity limit. Therefore, for highly water-sensitive formations with high clay content such as mudstone, calcium chloride drilling fluid can effectively inhibit the expansion and instability of the well wall and the hydration and slurrying of drill cuttings, thereby reducing complex downhole accidents and improving drilling efficiency. However, in actual application, there are still many unresolved problems with calcium chloride drilling fluid, such as the easy reaction of calcium ions with caustic soda and soda ash, which will lead to compatibility problems, and the strong flocculation effect of divalent cations on clay will make it difficult to control the viscosity and filtration loss of clay-containing calcium chloride drilling fluid, and will also limit the role of conventional lubricants. Therefore, it is necessary to develop a clay-free calcium chloride water-based drilling fluid. Summary of the invention

[0004] In order to overcome the shortcomings of existing calcium chloride water-based drilling fluids and solve the problems of well wall stability and clay slurrying in mudstone formations, the present invention provides a calcium chloride water-based drilling fluid without clay phase and its preparation method and application. The drilling fluid has significant inhibition, stable pH and rheology, controllable filtration loss, excellent lubricity, and can effectively improve the drilling efficiency of mudstone formations.

[0005] To achieve the above object, the present invention provides the following solutions:

[0006] One of the technical solutions of the present invention is a water-based calcium chloride drilling fluid without a clay phase, wherein the raw materials include, by weight:

[0007] Water: 100 parts

[0008] Calcium chloride: 40-100 parts

[0009] pH adjuster: 2.0-3.0 parts

[0010] Thickening coating agent: 2.0-3.0 parts

[0011] Fluid loss reducer: 3.0-5.0 parts

[0012] Plugging agent: 1.0-1.5 parts

[0013] Auxiliary inhibitor: 5.0-10.0 parts

[0014] Antioxidant: 2.0-3.0 parts

[0015] Lubricating corrosion inhibitor: 1.0~2.0 parts

[0016] Dispersant: 1.0-2.0 parts

[0017] Barite: unlimited amount, added until the density of calcium chloride water-based drilling fluid without clay phase is 1.20-2.00 g / cm 3 That's it.

[0018] The second technical solution of the present invention is a method for preparing the above-mentioned calcium chloride water-based drilling fluid without clay phase, comprising the following steps:

[0019] Calcium chloride, auxiliary inhibitor, pH regulator, viscosity enhancing coating agent, antioxidant, fluid loss reducer, plugging agent, lubricating corrosion inhibitor, dispersant and barite are added to water in order by mass under stirring to prepare the clay-free calcium chloride water-based drilling fluid.

[0020] A third technical solution of the present invention is the application of the above-mentioned clay-free calcium chloride water-based drilling fluid in oil and gas drilling projects.

[0021] The present invention discloses the following technical effects:

[0022] The present invention develops a clay-free calcium chloride water-based drilling fluid and a preparation method thereof. In addition to having excellent mudstone hydration inhibition, the present invention also avoids the use of a pH regulator that is easily reactive with calcium chloride, and through a clay-free formula design, significantly improves rheological stability and filtration control performance, while taking into account the needs of wellbore cleaning and well control; in addition, the present invention also has good lubrication and drag reduction performance, and meets the relevant requirements for the construction of high-angle directional wells and horizontal wells in mudstone formations.

[0023] The invention provides a clay-free calcium chloride water-based drilling fluid having excellent clay hydration inhibition performance, while avoiding the use of traditional pH regulators such as sodium hydroxide and sodium carbonate that are incompatible with calcium chloride, thereby improving the stability of the system; and the preparation of betaine derivatives realizes the demand for rheological regulation of the drilling fluid under clay-free conditions, and provides appropriate coating performance in combination with polyethyleneimine, thereby further ensuring the integrity of drill cuttings; in addition, the rigid nanomaterial as a plugging agent can participate in the formation of mud cakes together with a filtrate reducer and barite, thereby improving the density of the mud cake, and can also fill formation micropores or microcracks to stabilize the well wall; and the "zero-dimensional" carbon dot material is innovatively introduced to effectively improve the lubrication and corrosion inhibition performance of the system to meet the demand for low friction torque of directional wells and horizontal wells; and the dispersant is reasonably used to improve the solid phase capacity limit of the calcium chloride drilling fluid, thereby contributing to the stability of the performance of the high-density system.

[0024] The density of the calcium chloride water-based drilling fluid without clay phase can reach 2.00 g / cm 3 , temperature resistance can reach 150℃, pH is stable, rheology is excellent, dynamic-plastic ratio is >0.5, API and HTHP filtration losses are <4.0mL and 14.0mL respectively, extreme pressure friction coefficient is <0.07, apparent viscosity increase rate after 40% sodium-based bentonite contamination is <20%, mudstone rolling recovery rate is >96%, linear expansion rate is <4%, corrosion rate is <0.076mm / a, suitable for construction operations in high mudstone formations, especially directional wells and horizontal wells. DETAILED DESCRIPTION

[0025] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as limiting the present invention, but should be understood as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0026] It should be understood that the terms described in the present invention are only for describing a particular embodiment and are not intended to limit the present invention. In addition, for the numerical range in the present invention, it should be understood that each intermediate value between the upper and lower limits of the scope is also specifically disclosed. The intermediate value in any stated value or stated range, and each smaller range between any other stated value or intermediate value in the described range is also included in the present invention. The upper and lower limits of these smaller ranges can be independently included or excluded in the scope.

[0027] Unless otherwise indicated, all technical and scientific terms used herein have the same meanings as those generally understood by those skilled in the art. Although the present invention describes only preferred methods and materials, any methods and materials similar or equivalent to those described herein may also be used in the implementation or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials associated with the documents. In the event of a conflict with any incorporated document, the content of this specification shall prevail.

[0028] It will be apparent to those skilled in the art that various modifications and variations may be made to the specific embodiments of the present invention description without departing from the scope or spirit of the present invention. Other embodiments derived from the present invention description will be apparent to the skilled artisan. The present invention description and examples are exemplary only.

[0029] The words “include,” “including,” “have,” “contain,” etc. used in this document are open-ended terms, meaning including but not limited to.

[0030] The "parts" described in the present invention, unless otherwise specified, all represent parts by mass.

[0031] The "%" described in the present invention, unless otherwise specified, refers to mass percentage.

[0032] The first aspect of the present invention provides a clay-free calcium chloride water-based drilling fluid, wherein the raw materials include, by weight:

[0033] Water: 100 parts

[0034] Calcium chloride: 40-100 parts

[0035] pH adjuster: 2.0-3.0 parts

[0036] Thickening coating agent: 2.0-3.0 parts

[0037] Fluid loss reducer: 3.0-5.0 parts

[0038] Plugging agent: 1.0-1.5 parts

[0039] Auxiliary inhibitor: 5.0-10.0 parts

[0040] Antioxidant: 2.0-3.0 parts

[0041] Lubricating corrosion inhibitor: 1.0~2.0 parts

[0042] Dispersant: 1.0-2.0 parts

[0043] Barite: unlimited amount, added until the density of calcium chloride water-based drilling fluid without clay phase is 1.20-2.00 g / cm3 That's it.

[0044] In a preferred embodiment of the present invention, the water is fresh water and / or sea water;

[0045] The pH regulator is composed of 60 to 80 parts of magnesium oxide and 20 to 40 parts of polyetheramine by mass. Magnesium oxide does not react with calcium chloride in the drilling fluid, and can continuously maintain the alkaline environment of the system, while being less affected by temperature; polyetheramine is also less affected by calcium chloride, and can enhance the alkalinity of the system on the basis of magnesium oxide, and also has strong inhibitory properties, which can assist in inhibiting clay hydration. The two work together to provide a suitable alkaline pH environment and maintain the stability of calcium chloride drilling fluid.

[0046] In a preferred embodiment of the present invention, the viscosity-enhancing coating agent is composed of 60 to 80 parts of betaine derivatives and 20 to 40 parts of polyethyleneimine;

[0047] The preparation method of the betaine derivative comprises the following steps:

[0048] 30-60 parts by weight of arachidonic acid and 5-10 parts by weight of potassium hydroxide are mixed and then deoxygenated by nitrogen. Then 12-24 parts by weight of dimethylaminopropylamine are added and the temperature is raised to 140-160° C. to react for 5-8 hours. Then the mixture is cooled to room temperature, distilled under reduced pressure, and washed to obtain an intermediate product A.

[0049] 10 to 20 parts by weight of epichlorohydrin are added to 100 to 200 parts by weight of a 90 wt% ethanol aqueous solution and mixed, then 6 to 12 parts by weight of aspartic acid are added, the temperature is raised to 40 to 50° C., the reaction is performed for 4 to 6 hours, and then the mixture is cooled to room temperature to obtain an intermediate product B;

[0050] The intermediate product A is added to the intermediate product B and mixed, and then nitrogen is passed to deoxygenate. The temperature is raised to 75-85° C. to react for 10-16 hours, and then cooled to room temperature. The solvent is removed by rotary evaporation to obtain the betaine derivative.

[0051] It is particularly noted that the viscosity-enhancing coating agent is composed of betaine derivatives and polyethyleneimine. Among them, the betaine derivative has a cationic group and an anionic group, which can form dense and stable micelles through intermolecular hydrogen bonds, van der Waals forces and electrostatic interactions in an aqueous solution with high calcium ion content. On the one hand, it can reduce surface tension and improve the dispersion stability of the drilling fluid solid suspension system. On the other hand, it benefits from the shear rearrangement characteristics of the micelles and exhibits good shear thinning behavior, that is, it provides high viscosity at low shear rates and reduces viscosity at high shear rates. This helps the drill bit to break rocks during high-speed shearing and effectively carry cuttings during the circulation of the drilling fluid, thereby keeping the wellbore clean. The molecular chains of traditional viscosity-enhancing agents will curl up in a high-concentration calcium ion environment, unable to form an effective spatial network structure, and it is difficult to play a shear thinning role. In addition, polyethyleneimine can assist in improving the clay hydration inhibition of the drilling fluid on the one hand, and on the other hand, it also has certain coating properties, which helps to improve the integrity of the cuttings.

[0052] In a preferred embodiment of the present invention, the fluid loss reducer is composed of 5 to 10 parts of carboxymethyl cellulose, 40 to 50 parts of carboxymethyl starch and 40 to 55 parts of potassium humate, by weight.

[0053] The raw materials of the carboxymethyl cellulose are composed of 50 to 70 parts of peanut shell cellulose, 20 to 30 parts of corn cymbidium cellulose and 10 to 20 parts of sugarcane bagasse cellulose by weight.

[0054] The carboxymethyl cellulose is prepared by compounding peanut shell cellulose, corn platycodon cellulose and sugarcane bagasse cellulose in proportions by mass and then performing carboxymethylation.

[0055] The raw materials of the carboxymethyl starch are composed of 30 to 40 parts of wheat starch, 30 to 40 parts of potato starch and 20 to 40 parts of cassava starch by weight;

[0056] The carboxymethyl starch is prepared by compounding wheat starch, potato starch and cassava starch according to mass proportions and then performing carboxymethylation production.

[0057] In a preferred embodiment of the present invention, the plugging agent is composed of 60 to 80 parts of nano-calcium carbonate, 10 to 20 parts of nano-zinc oxide and 10 to 20 parts of nano-aluminum oxide, by mass. Nano-calcium carbonate can fill micropores, improve the density of mud cake and compress the thickness of mud cake. In addition to these properties, nano-zinc oxide can also effectively inhibit the growth and reproduction of microorganisms and prevent the drilling fluid from spoiling and deteriorating. Nano-aluminum oxide has stronger rigidity, which helps to improve the pressure bearing strength of the plugging layer.

[0058] The auxiliary inhibitor is composed of 40-60 parts of potassium chloride and 40-60 parts of sodium formate by weight. Potassium ions can be "embedded" between clay layers to inhibit clay hydration and expansion; formate ions can remove free radicals, play an antioxidant role, and help improve the temperature resistance of the polymer.

[0059] In a preferred embodiment of the present invention, the antioxidant is composed of 5 to 10 parts of catechins, 5 to 10 parts of rutin, 30 to 40 parts of sodium D-isoascorbate, and 40 to 60 parts of polyethylene glycol by weight. Catechins, rutin, and sodium D-isoascorbate can effectively remove free radicals and reduce the oxidative effects on polymer materials, thereby improving the stability of drilling fluids at high temperatures; polyethylene glycol, on the one hand, helps catechins, rutin, and sodium D-isoascorbate to disperse in the drilling fluid and thus play a role, and on the other hand, it can also use its cloud point effect to assist in improving the lubricity, plugging, and inhibition of the drilling fluid.

[0060] In a preferred embodiment of the present invention, the method for preparing the lubricating corrosion inhibitor comprises the following steps:

[0061] 7-15 parts by weight of glutamic acid and 10-18 parts by weight of glucose are dissolved in 100 parts by weight of deionized water, followed by hydrothermal reaction at 180-200° C. for 6-10 hours, cooled to room temperature and filtered, and the filtrate obtained by filtration is placed in a 500Da dialysis bag for 24-48 hours, with water replaced every 6 hours, and then the solvent is removed by rotary evaporation, and vacuum dried to obtain an intermediate product A;

[0062] The intermediate product A is added to 100 parts by weight of 90 wt% ethanol aqueous solution, stirred for 10 to 30 minutes, and then 20 to 30 parts by weight of chlorododecane is added. After nitrogen is passed through to deoxygenate, the temperature is raised to 60 to 80° C., and after reacting for 8 to 12 hours, the heating is stopped and the mixture is cooled to room temperature, and then the solvent is removed by rotary evaporation to obtain the intermediate product B;

[0063] The intermediate product B is mixed with 20 to 30 parts by weight of oleic acid imidazoline and 30 to 40 parts by weight of ricinoleic acid diethanolamide and stirred for 1 to 3 hours to obtain the lubricating corrosion inhibitor.

[0064] It is particularly noted that the lubricating corrosion inhibitor has both lubricating drag reduction and corrosion inhibition effects. Nitrogen-doped carbon dots are prepared from amino acids and glucose through hydrothermal synthesis, and then surface-modified to obtain amphiphilic nitrogen-doped carbon dots, which contain a large number of carboxyl and hydroxyl hydrophilic groups and hydrophobic alkyl long chains, and can be adsorbed on the metal surface and form a thin film layer. On the one hand, it can avoid direct contact between friction pairs, thereby reducing the friction coefficient and achieving a lubricating drag reduction effect; on the other hand, since high-concentration calcium chloride is highly corrosive, it will corrode metal parts such as drilling tools and casings, and the lubricating corrosion inhibitor can block the contact between the corrosive medium and the metal, and play a corrosion inhibition role. At the same time, the presence of oleic acid imidazoline and ricinoleic acid diethanolamide strengthens this adsorption and film-forming effect, further improving the lubrication and corrosion inhibition effects.

[0065] In a preferred embodiment of the present invention, the dispersant is composed of 10 to 20 parts of AKN-1070, 10 to 20 parts of AKN-2200, 30 to 40 parts of AKN-2263 and 20 to 50 parts of AKN-2350. Since high concentration calcium chloride has a strong flocculation effect on solid phase materials, resulting in uneven solid phase dispersion, which in turn leads to loose mud cakes that are not conducive to filtration loss control, the introduction of dispersants can effectively improve the dispersion stability of the solid phase in high concentration calcium chloride drilling fluids, and avoid agglomeration between solid phases that affects the water loss and wall-forming properties of the drilling fluid.

[0066] The second aspect of the present invention provides a method for preparing the above-mentioned calcium chloride water-based drilling fluid without clay phase, comprising the following steps:

[0067] Calcium chloride, auxiliary inhibitor, pH regulator, viscosity enhancing coating agent, antioxidant, fluid loss reducer, plugging agent, lubricating corrosion inhibitor, dispersant and barite are added to water in order by mass under stirring to prepare the clay-free calcium chloride water-based drilling fluid.

[0068] In a preferred embodiment of the present invention, water is first added to a container by mass, and calcium chloride is added to the container at a stirring speed of 6000 to 10000 r / min, and stirred for 5 to 10 minutes; the auxiliary inhibitor is continued to be added, and stirred for 3 to 5 minutes; the pH adjuster is continued to be added, and stirred for 3 to 5 minutes; the viscosity-increasing coating agent is continued to be added, and stirred for 20 to 30 minutes; the antioxidant is continued to be added, and stirred for 3 to 5 minutes; the filtrate reducer is slowly added, and stirred for 20 to 30 minutes; the plugging agent is continued to be added, and stirred for 10 to 20 minutes; the lubricating corrosion inhibitor is continued to be added, and stirred for 10 to 20 minutes; the dispersant is continued to be added, and stirred for 5 to 10 minutes; finally, barite is added, and stirred for 30 to 40 minutes to obtain the clay-free calcium chloride water-based drilling fluid.

[0069] A third aspect of the present invention provides an application of the above-mentioned calcium chloride water-based drilling fluid without clay phase in oil and gas drilling engineering.

[0070] The technical solutions described in the present invention, unless otherwise specified, are all conventional solutions in the art, and the reagents or raw materials used, unless otherwise specified, are purchased from commercial channels or have been disclosed.

[0071] The molecular weight of the polyetheramine used in the embodiments of the present invention is 200-500Da.

[0072] The molecular weight of polyethyleneimine used in the embodiments of the present invention is 10000-100000Da.

[0073] AKN-1070, AKN-2200, AKN-2263 and AKN-2350 used in the embodiments of the present invention are from Foshan Qianyou Chemical Co., Ltd.

[0074] The technical solutions provided by the present invention are described in detail below in conjunction with the embodiments, but they should not be construed as limiting the protection scope of the present invention.

[0075] Example 1

[0076] This embodiment provides a clay-free calcium chloride water-based drilling fluid, which is composed of the following components in parts by weight:

[0077] Water: 100 parts

[0078] Calcium chloride: 40 parts

[0079] pH adjuster: 2.0 parts

[0080] Thickening coating agent: 2.0 parts

[0081] Fluid loss reducer: 3.0 parts

[0082] Blocking agent: 1.0 part

[0083] Auxiliary inhibitor: 5.0 parts

[0084] Antioxidant: 2.0 parts

[0085] Lubricating corrosion inhibitor: 1.0 part

[0086] Dispersant: 1.0 part

[0087] Barite: Add to drilling fluid density of 1.20g / cm 3 .

[0088] Among them, water is fresh water.

[0089] The pH regulator is a mixture of magnesium oxide and polyetheramine;

[0090] The pH regulator is composed of 60 parts of magnesium oxide and 40 parts of polyetheramine based on 100 parts by mass;

[0091] The viscosity-enhancing coating agent is a compound of betaine derivatives and polyethyleneimine;

[0092] The viscosity-enhancing coating agent is composed of 60 parts of betaine derivative and 40 parts of polyethyleneimine based on 100 parts by mass;

[0093] The preparation method of betaine derivatives comprises the following steps:

[0094] First, 30 parts by weight of arachidonic acid and 5 parts by weight of potassium hydroxide were added to a four-necked round-bottom flask, and nitrogen was passed through to deoxygenate after stirring for 10 minutes. Then, 12 parts by weight of dimethylaminopropylamine was added dropwise, and the temperature was raised to 140° C. to start the reaction. After 5 hours, the heating was stopped and the mixture was cooled to room temperature. The remaining dimethylaminopropylamine was removed by vacuum distillation, and then a dilute alkali aqueous solution (0.1 mol / L sodium hydroxide solution) was used for multiple washings to remove the remaining arachidonic acid, to obtain an intermediate product A.

[0095] Secondly, 10 parts by mass of epichlorohydrin was added to a three-necked round-bottom flask containing 100 parts by mass of a 90% ethanol aqueous solution, and after stirring for 20 minutes, 6 parts by mass of aspartic acid was added, and the temperature was raised to 40°C to start the reaction, which lasted for 4 hours, and the heating was stopped and cooled to room temperature to obtain an intermediate product B;

[0096] Again, the intermediate product A was added to the flask containing the intermediate product B, and after stirring for 20 minutes, nitrogen was passed to deoxygenate, the temperature was raised to 75°C, the reaction was continued for 10 hours, the heating was stopped and the mixture was cooled to room temperature, and the solvent was removed by a rotary evaporator to obtain the target product betaine derivative.

[0097] The fluid loss reducer is a compound of carboxymethyl cellulose, carboxymethyl starch and potassium humate;

[0098] The fluid loss reducer is composed of 5 parts of carboxymethyl cellulose, 40 parts of carboxymethyl starch and 55 parts of potassium humate based on 100 parts by mass;

[0099] Carboxymethyl starch is produced by compounding wheat starch, potato starch and cassava starch and then carboxymethylating them.

[0100] The starch raw materials used for the carboxymethyl starch are composed of 30 parts of wheat starch, 30 parts of potato starch and 40 parts of cassava starch based on 100 parts by mass.

[0101] The preparation method of carboxymethyl starch is as follows:

[0102] 20 parts by mass of starch raw material are added to a three-necked round-bottom flask filled with 150 parts by mass of deionized water, the temperature is raised to 90° C. under stirring conditions, the temperature is maintained for 5 hours, and then cooled to room temperature, 4 parts by mass of sodium hydroxide and 30 parts by mass of 90wt% ethanol are continuously added under stirring conditions, the temperature is raised to 52° C., and then 8 parts by mass of monochloroacetic acid are dissolved in 15 parts by mass of 90wt% ethanol and added to the flask, the temperature is raised to 62° C., the reaction is carried out for 6 hours, the temperature is cooled to room temperature, anhydrous ethanol is added to precipitate, and the precipitate obtained by filtration is dried and pulverized to obtain carboxymethyl starch.

[0103] The plugging agent is a mixture of nano calcium carbonate, nano zinc oxide and nano aluminum oxide;

[0104] The plugging agent is composed of 60 parts of nano calcium carbonate, 20 parts of nano zinc oxide and 20 parts of nano aluminum oxide based on 100 parts by mass;

[0105] The auxiliary inhibitor is a compound of potassium chloride and sodium formate;

[0106] The auxiliary inhibitor is composed of 40 parts of potassium chloride and 60 parts of sodium formate based on 100 parts by mass;

[0107] The antioxidant is a compound of catechin, rutin, sodium D-isoascorbate and polyethylene glycol;

[0108] The antioxidant is composed of 5 parts of catechins, 5 parts of rutin, 30 parts of sodium D-isoascorbate and 60 parts of polyethylene glycol based on 100 parts by mass;

[0109] The lubricating corrosion inhibitor is obtained by the following preparation method:

[0110] First, 7 parts by mass of glutamic acid and 10 parts by mass of glucose were dissolved in 100 parts by mass of deionized water, and then transferred to a Teflon high-temperature autoclave, heated to 180°C for 6 hours, cooled to room temperature, filtered using a 0.22 μm filter membrane, and then the filtrate obtained by filtration was placed in a 500Da dialysis bag for 24 hours, the water was changed every 6 hours, and then the solvent was removed by rotary evaporation, and the intermediate product A was obtained by vacuum drying;

[0111] Secondly, the intermediate product A was added to a three-necked round-bottom flask containing 100 parts by mass of a 90% ethanol aqueous solution, and after stirring for 10 minutes, 20 parts by mass of chlorododecane was added, and after nitrogen was passed through to deoxygenate, the temperature was raised to 60°C, and after reacting for 8 hours, the heating was stopped and the solution was cooled to room temperature, and then the solvent was removed by rotary evaporation to obtain the intermediate product B;

[0112] Finally, the intermediate product B was mixed with 20 parts by weight of oleic acid imidazoline and 30 parts by weight of ricinoleic acid diethanolamide and stirred for 1 hour to obtain the target product, a lubricating corrosion inhibitor.

[0113] The dispersant is a compound of AKN-1070, AKN-2200, AKN-2263 and AKN-2350;

[0114] The dispersant is composed of 10 parts by mass of AKN-1070, 10 parts by mass of AKN-2200, 30 parts by mass of AKN-2263 and 50 parts by mass of AKN-2350.

[0115] The preparation method of the above-mentioned clay-free calcium chloride water-based drilling fluid comprises the following steps:

[0116] According to the mass fraction, water is first added into the container, and calcium chloride is added into the container at a stirring speed of 6000r / min, and stirred for 5 minutes; the auxiliary inhibitor is continued to be added, and stirred for 3 minutes; the pH adjuster is continued to be added, and stirred for 3 minutes; the viscosity enhancing coating agent is continued to be added, and stirred for 20 minutes; the antioxidant is continued to be added, and stirred for 3 minutes; the filtrate reducer is slowly added, and stirred for 20 minutes; the plugging agent is continued to be added, and stirred for 10 minutes; the lubricating corrosion inhibitor is continued to be added, and stirred for 10 minutes; the dispersant is continued to be added, and stirred for 5 minutes; finally, barite is added, and stirred for 30 minutes to obtain a clay-free calcium chloride water-based drilling fluid (abbreviated as: drilling fluid).

[0117] The drilling fluid density prepared in this example is 1.20 g / cm 3 , the drilling fluid aging temperature is 70℃.

[0118] Example 2

[0119] This embodiment provides a clay-free calcium chloride water-based drilling fluid, which is composed of the following components in parts by weight:

[0120] Water: 100 parts

[0121] Calcium chloride: 100 parts

[0122] pH adjuster: 3.0 parts

[0123] Thickening coating agent: 3.0 parts

[0124] Fluid loss reducer: 5.0 parts

[0125] Blocking agent: 1.5 parts

[0126] Auxiliary inhibitor: 10.0 parts

[0127] Antioxidants: 3.0 parts

[0128] Lubricating corrosion inhibitor: 2.0 parts

[0129] Dispersant: 2.0 parts

[0130] Barite: Add to drilling fluid density of 1.40g / cm 3 .

[0131] Among them, water is sea water.

[0132] The pH regulator is a mixture of magnesium oxide and polyetheramine;

[0133] The pH regulator is composed of 80 parts of magnesium oxide and 20 parts of polyetheramine based on 100 parts by mass;

[0134] The viscosity-enhancing coating agent is a compound of betaine derivatives and polyethyleneimine;

[0135] The viscosity-enhancing coating agent is composed of 80 parts of betaine derivative and 20 parts of polyethyleneimine based on 100 parts by mass;

[0136] The preparation method of the above betaine derivative comprises the following steps:

[0137] First, 60 parts by weight of arachidonic acid and 10 parts by weight of potassium hydroxide were added to a four-necked round-bottom flask, and nitrogen was passed through to deoxygenate after stirring for 30 minutes. Then, 24 parts by weight of dimethylaminopropylamine was added dropwise, and the temperature was raised to 160° C. to start the reaction. After 8 hours, the heating was stopped and the mixture was cooled to room temperature. The remaining dimethylaminopropylamine was removed by vacuum distillation, and then the remaining arachidonic acid was removed by multiple washings with a dilute alkaline aqueous solution to obtain an intermediate product A.

[0138] Secondly, 20 parts by mass of epichlorohydrin was added to a three-necked round-bottom flask containing 200 parts by mass of 90% ethanol aqueous solution, and after stirring for 30 minutes, 12 parts by mass of aspartic acid was added, and the temperature was raised to 50°C to start the reaction, which lasted for 6 hours, and the heating was stopped and cooled to room temperature to obtain an intermediate product B;

[0139] Again, the intermediate product A was added to the flask containing the intermediate product B, and after stirring for 40 minutes, nitrogen was passed to deoxygenate, the temperature was raised to 85°C, the reaction was continued for 16 hours, the heating was stopped and the mixture was cooled to room temperature, and the solvent was removed by a rotary evaporator to obtain the target product, a betaine derivative.

[0140] The fluid loss reducer is a compound of carboxymethyl cellulose, carboxymethyl starch and potassium humate;

[0141] The fluid loss reducer is composed of 100 parts by mass of carboxymethyl cellulose, 50 parts by mass of carboxymethyl starch and 40 parts by mass of potassium humate;

[0142] Carboxymethyl starch is produced by compounding wheat starch, potato starch and cassava starch and then carboxymethylating them.

[0143] The starch raw materials used for the carboxymethyl starch are composed of 40 parts of wheat starch, 40 parts of potato starch and 20 parts of cassava starch based on 100 parts by mass.

[0144] The preparation method of carboxymethyl starch is the same as the preparation method of carboxymethyl starch in Example 1.

[0145] The plugging agent is a mixture of nano calcium carbonate, nano zinc oxide and nano aluminum oxide;

[0146] The plugging agent is composed of 80 parts of nano calcium carbonate, 10 parts of nano zinc oxide and 10 parts of nano aluminum oxide based on 100 parts by mass;

[0147] The auxiliary inhibitor is a compound of potassium chloride and sodium formate;

[0148] The auxiliary inhibitor is composed of 60 parts of potassium chloride and 40 parts of sodium formate based on 100 parts by mass;

[0149] The antioxidant is a compound of catechin, rutin, sodium D-isoascorbate and polyethylene glycol;

[0150] The antioxidant is composed of 10 parts by weight of catechins, 10 parts by weight of rutin, 40 parts by weight of sodium D-isoascorbate and 40 parts by weight of polyethylene glycol;

[0151] The lubricating corrosion inhibitor is obtained by the following preparation method:

[0152] First, 15 parts by weight of glutamic acid and 18 parts by weight of glucose were dissolved in 100 parts by weight of deionized water, and then transferred to a Teflon high-temperature autoclave, heated to 200°C for 10 hours, cooled to room temperature, filtered using a 0.22 μm filter membrane, and then the filtrate obtained by filtration was placed in a 500 Da dialysis bag for 48 hours, the water was changed every 6 hours, and then the solvent was removed by rotary evaporation, and the intermediate product A was obtained by vacuum drying;

[0153] Secondly, the intermediate product A was added to a three-necked round-bottom flask containing 100 parts by mass of a 90% ethanol aqueous solution, and after stirring for 30 minutes, 30 parts by mass of chlorododecane was added, and after nitrogen was passed through to deoxygenate, the temperature was raised to 80°C, and after reacting for 12 hours, the heating was stopped and the mixture was cooled to room temperature, and the solvent was removed by rotary evaporation to obtain the intermediate product B;

[0154] Finally, the intermediate product B was mixed with 30 parts by mass of oleic acid imidazoline and 40 parts by mass of ricinoleic acid diethanolamide and stirred for 3 hours to obtain the target product.

[0155] The dispersant is a compound of AKN-1070, AKN-2200, AKN-2263 and AKN-2350;

[0156] Preferably, the dispersant is composed of 20 parts of AKN-1070, 20 parts of AKN-2200, 40 parts of AKN-2263 and 20 parts of AKN-2350 based on 100 parts by mass.

[0157] The preparation method of the above-mentioned calcium chloride water-based drilling fluid without clay phase comprises the following steps:

[0158] According to the mass fraction, water is first added into the container, and calcium chloride is added into the container at a stirring speed of 10000r / min, and stirred for 10 minutes; the auxiliary inhibitor is continued to be added, and stirred for 5 minutes; the pH adjuster is continued to be added, and stirred for 5 minutes; the viscosity enhancing coating agent is continued to be added, and stirred for 30 minutes; the antioxidant is continued to be added, and stirred for 5 minutes; the filtrate reducer is slowly added, and stirred for 30 minutes; the plugging agent is continued to be added, and stirred for 20 minutes; the lubricating corrosion inhibitor is continued to be added, and stirred for 20 minutes; the dispersant is continued to be added, and stirred for 10 minutes; finally, barite is added, and stirred for 40 minutes to obtain the clay-free calcium chloride water-based drilling fluid.

[0159] The drilling fluid density prepared in this example is 1.40 g / cm 3 , the drilling fluid aging temperature is 90℃.

[0160] Example 3

[0161] This embodiment provides a clay-free calcium chloride water-based drilling fluid, which is composed of the following components in parts by weight:

[0162] Water: 100 parts

[0163] Calcium chloride: 70 parts

[0164] pH adjuster: 2.5 parts

[0165] Thickening coating agent: 2.5 parts

[0166] Fluid loss reducer: 4.0 parts

[0167] Blocking agent: 1.2 parts

[0168] Auxiliary inhibitor: 7.0 parts

[0169] Antioxidants: 2.5 parts

[0170] Lubricating corrosion inhibitor: 1.5 parts

[0171] Dispersant: 1.5 parts

[0172] Barite: Add to drilling fluid density of 1.60g / cm 3 .

[0173] Among them, water is fresh water.

[0174] The pH regulator is a mixture of magnesium oxide and polyetheramine;

[0175] The pH regulator is composed of 70 parts of magnesium oxide and 30 parts of polyetheramine based on 100 parts by mass;

[0176] The viscosity-enhancing coating agent is a compound of betaine derivatives and polyethyleneimine;

[0177] The viscosity-enhancing coating agent is composed of 70 parts of betaine derivative and 30 parts of polyethyleneimine based on 100 parts by mass;

[0178] The preparation method of the above betaine derivative comprises the following steps:

[0179] First, 45 parts by weight of arachidonic acid and 7.5 parts by weight of potassium hydroxide were added to a four-necked round-bottom flask, and nitrogen was passed through to deoxygenate after stirring for 20 minutes. Then, 18 parts by weight of dimethylaminopropylamine was added dropwise, and the temperature was raised to 150° C. to start the reaction. After 6.5 hours, the heating was stopped and the mixture was cooled to room temperature. The remaining dimethylaminopropylamine was removed by vacuum distillation, and then the remaining arachidonic acid was removed by multiple washings with a dilute alkaline aqueous solution to obtain an intermediate product A.

[0180] Secondly, 15 parts by mass of epichlorohydrin was added to a three-necked round-bottom flask containing 150 parts by mass of a 90% ethanol aqueous solution, and after stirring for 25 minutes, 9 parts by mass of aspartic acid was added, and the temperature was raised to 45°C to start the reaction, which lasted for 5 hours, and the heating was stopped and cooled to room temperature to obtain an intermediate product B;

[0181] Again, the intermediate product A was added to the flask containing the intermediate product B, and after stirring for 30 minutes, nitrogen was passed to deoxygenate, the temperature was raised to 80°C, the reaction was continued for 13 hours, the heating was stopped and the mixture was cooled to room temperature, and the solvent was removed by a rotary evaporator to obtain the target product, a betaine derivative.

[0182] The fluid loss reducer is a compound of carboxymethyl cellulose, carboxymethyl starch and potassium humate;

[0183] The fluid loss reducer is composed of 7 parts of carboxymethyl cellulose, 45 parts of carboxymethyl starch and 48 parts of potassium humate based on 100 parts by mass;

[0184] Carboxymethyl starch is produced by compounding wheat starch, potato starch and cassava starch and then carboxymethylating them.

[0185] The starch raw materials used for the carboxymethyl starch are composed of 35 parts of wheat starch, 35 parts of potato starch and 30 parts of cassava starch based on 100 parts by mass.

[0186] The preparation method of carboxymethyl starch is the same as the preparation method of carboxymethyl starch in Example 1.

[0187] The plugging agent is a mixture of nano calcium carbonate, nano zinc oxide and nano aluminum oxide;

[0188] The plugging agent is composed of 70 parts of nano calcium carbonate, 15 parts of nano zinc oxide and 15 parts of nano aluminum oxide based on 100 parts by mass;

[0189] The auxiliary inhibitor is a compound of potassium chloride and sodium formate;

[0190] The auxiliary inhibitor is composed of 50 parts of potassium chloride and 50 parts of sodium formate based on 100 parts by mass;

[0191] The antioxidant is a compound of catechin, rutin, sodium D-isoascorbate and polyethylene glycol;

[0192] The antioxidant is composed of 7.5 parts of catechins, 7.5 parts of rutin, 35 parts of sodium D-isoascorbate and 50 parts of polyethylene glycol based on 100 parts by mass;

[0193] The lubricating corrosion inhibitor is obtained by the following preparation method:

[0194] First, 11 parts by weight of glutamic acid and 14 parts by weight of glucose were dissolved in 100 parts by weight of deionized water, and then transferred to a Teflon high-temperature autoclave, heated to 190°C for 8 hours, cooled to room temperature, filtered using a 0.22 μm filter membrane, and then the filtrate obtained by filtration was placed in a 500 Da dialysis bag for 36 hours, the water was changed every 6 hours, and then the solvent was removed by rotary evaporation, and the intermediate product A was obtained by vacuum drying;

[0195] Secondly, the intermediate product A was added to a three-necked round-bottom flask containing 100 parts by mass of a 90% ethanol aqueous solution, and after stirring for 20 minutes, 15 parts by mass of chlorododecane was added, and after nitrogen was passed through to deoxygenate, the temperature was raised to 70°C, and after reacting for 10 hours, the heating was stopped and the mixture was cooled to room temperature, and the solvent was removed by rotary evaporation to obtain the intermediate product B;

[0196] Finally, the intermediate product B was mixed with 25 parts by mass of oleic acid imidazoline and 35 parts by mass of ricinoleic acid diethanolamide and stirred for 2 hours to obtain the target product, a lubricating corrosion inhibitor.

[0197] The dispersant is a compound of AKN-1070, AKN-2200, AKN-2263 and AKN-2350;

[0198] The dispersant is composed of 15 parts of AKN-1070, 15 parts of AKN-2200, 35 parts of AKN-2263 and 35 parts of AKN-2350 based on 100 parts by mass.

[0199] The preparation method of the above-mentioned clay-free calcium chloride water-based drilling fluid comprises the following steps:

[0200] According to the mass fraction, water is first added into the container, and calcium chloride is added into the container at a stirring speed of 8000r / min, and stirred for 7 minutes; the auxiliary inhibitor is continued to be added, and stirred for 4 minutes; the pH adjuster is continued to be added, and stirred for 4 minutes; the viscosity enhancing coating agent is continued to be added, and stirred for 25 minutes; the antioxidant is continued to be added, and stirred for 4 minutes; the filtrate reducer is slowly added, and stirred for 25 minutes; the plugging agent is continued to be added, and stirred for 15 minutes; the lubricating corrosion inhibitor is continued to be added, and stirred for 15 minutes; the dispersant is continued to be added, and stirred for 7 minutes; finally, barite is added, and stirred for 35 minutes to obtain the clay-free calcium chloride water-based drilling fluid.

[0201] The drilling fluid density prepared in this example is 1.60 g / cm 3 , the drilling fluid aging temperature is 110℃.

[0202] Example 4

[0203] This embodiment provides a clay-free calcium chloride water-based drilling fluid, which is composed of the following components in parts by weight:

[0204] Water: 100 parts

[0205] Calcium chloride: 60 parts

[0206] pH adjuster: 2.0 parts

[0207] Thickening coating agent: 2.2 parts

[0208] Fluid loss reducer: 3.5 parts

[0209] Blocking agent: 1.5 parts

[0210] Auxiliary inhibitor: 8.0 parts

[0211] Antioxidant: 2.0 parts

[0212] Lubricating corrosion inhibitor: 1.8 parts

[0213] Dispersant: 1.2 parts

[0214] Barite: Add to drilling fluid density of 1.80g / cm 3 .

[0215] Among them, water is sea water.

[0216] The pH regulator is a mixture of magnesium oxide and polyetheramine;

[0217] The pH regulator is composed of 65 parts of magnesium oxide and 35 parts of polyetheramine based on 100 parts by mass;

[0218] The viscosity-enhancing coating agent is a compound of betaine derivatives and polyethyleneimine;

[0219] The viscosity-enhancing coating agent is composed of 65 parts of betaine derivative and 35 parts of polyethyleneimine based on 100 parts by mass;

[0220] The preparation method of the above betaine derivative comprises the following steps:

[0221] First, 40 parts by weight of arachidonic acid and 7 parts by weight of potassium hydroxide were added to a four-necked round-bottom flask, and nitrogen was passed through to deoxygenate after stirring for 15 minutes. Then, 15 parts by weight of dimethylaminopropylamine was added dropwise, and the temperature was raised to 145° C. to start the reaction. After 6 hours, the heating was stopped and the mixture was cooled to room temperature. The remaining dimethylaminopropylamine was removed by vacuum distillation, and then the remaining arachidonic acid was removed by multiple washings with a dilute alkaline aqueous solution to obtain an intermediate product A.

[0222] Secondly, 13 parts by mass of epichlorohydrin was added to a three-necked round-bottom flask containing 130 parts by mass of a 90% ethanol aqueous solution, and after stirring for 24 minutes, 8 parts by mass of aspartic acid was added, and the temperature was raised to 42°C to start the reaction, which lasted for 4.5 hours, and the heating was stopped and cooled to room temperature to obtain an intermediate product B;

[0223] Again, the intermediate product A was added to the flask containing the intermediate product B, and after stirring for 25 minutes, nitrogen was passed to deoxygenate, the temperature was raised to 78°C, the reaction was continued for 12 hours, the heating was stopped and the mixture was cooled to room temperature, and the solvent was removed by a rotary evaporator to obtain the target product betaine derivative.

[0224] The fluid loss reducer is a compound of carboxymethyl cellulose, carboxymethyl starch and potassium humate;

[0225] The fluid loss reducer is composed of 100 parts by mass of carboxymethyl cellulose, 40 parts by mass of carboxymethyl starch and 50 parts by mass of potassium humate;

[0226] Carboxymethyl starch is produced by compounding wheat starch, potato starch and cassava starch and then carboxymethylating them.

[0227] The starch raw materials used for the carboxymethyl starch are composed of 30 parts of wheat starch, 40 parts of potato starch and 30 parts of cassava starch based on 100 parts by mass.

[0228] The preparation method of carboxymethyl starch is the same as the preparation method of carboxymethyl starch in Example 1.

[0229] The plugging agent is a mixture of nano calcium carbonate, nano zinc oxide and nano aluminum oxide;

[0230] The plugging agent is composed of 65 parts of nano calcium carbonate, 20 parts of nano zinc oxide and 15 parts of nano aluminum oxide based on 100 parts by mass;

[0231] The auxiliary inhibitor is a compound of potassium chloride and sodium formate;

[0232] The auxiliary inhibitor is composed of 45 parts of potassium chloride and 55 parts of sodium formate based on 100 parts by mass;

[0233] The antioxidant is a compound of catechin, rutin, sodium D-isoascorbate and polyethylene glycol;

[0234] The antioxidant is composed of 5 parts of catechins, 10 parts of rutin, 40 parts of sodium D-isoascorbate and 45 parts of polyethylene glycol based on 100 parts by mass;

[0235] The lubricating corrosion inhibitor is obtained by the following preparation method:

[0236] First, 10 parts by weight of glutamic acid and 13 parts by weight of glucose were dissolved in 100 parts by weight of deionized water, and then transferred to a Teflon high-temperature autoclave, heated to 185°C for 7 hours, cooled to room temperature, filtered using a 0.22 μm filter membrane, and then the filtrate obtained by filtration was placed in a 500 Da dialysis bag for 30 hours, the water was changed every 6 hours, and then the solvent was removed by rotary evaporation, and the intermediate product A was obtained by vacuum drying;

[0237] Secondly, the intermediate product A was added to a three-necked round-bottom flask containing 100 parts by mass of a 90% ethanol aqueous solution, and after stirring for 15 minutes, 24 parts by mass of chlorododecane was added, and after nitrogen was passed through to deoxygenate, the temperature was raised to 65° C., and after reacting for 9 hours, the heating was stopped and the solution was cooled to room temperature, and then the solvent was removed by rotary evaporation to obtain the intermediate product B;

[0238] Finally, the intermediate product B was mixed with 30 parts by mass of oleic acid imidazoline and 30 parts by mass of ricinoleic acid diethanolamide and stirred for 1.5 hours to obtain the target product, a lubricating corrosion inhibitor.

[0239] The dispersant is a compound of AKN-1070, AKN-2200, AKN-2263 and AKN-2350;

[0240] The dispersant is composed of 10 parts by mass of AKN-1070, 20 parts by mass of AKN-2200, 30 parts by mass of AKN-2263 and 40 parts by mass of AKN-2350.

[0241] The preparation method of the above-mentioned clay-free calcium chloride water-based drilling fluid comprises the following steps:

[0242] According to the mass fraction, water is first added into the container, and calcium chloride is added into the container at a stirring speed of 8000r / min, and stirred for 8 minutes; the auxiliary inhibitor is continued to be added, and stirred for 3 minutes; the pH adjuster is continued to be added, and stirred for 5 minutes; the viscosity enhancing coating agent is continued to be added, and stirred for 30 minutes; the antioxidant is continued to be added, and stirred for 3 minutes; the filtrate reducer is slowly added, and stirred for 25 minutes; the plugging agent is continued to be added, and stirred for 20 minutes; the lubricating corrosion inhibitor is continued to be added, and stirred for 15 minutes; the dispersant is continued to be added, and stirred for 5 minutes; finally, barite is added, and stirred for 40 minutes to obtain the clay-free calcium chloride water-based drilling fluid.

[0243] The drilling fluid density prepared in this example is 1.80 g / cm 3 , the drilling fluid aging temperature is 130℃.

[0244] Example 5

[0245] This embodiment provides a clay-free calcium chloride water-based drilling fluid, which is composed of the following components in parts by weight:

[0246] Water: 100 parts

[0247] Calcium chloride: 90 parts

[0248] pH adjuster: 2.4 parts

[0249] Thickening coating agent: 2.0 parts

[0250] Fluid loss reducer: 4.2 parts

[0251] Blocking agent: 1.3 parts

[0252] Auxiliary inhibitor: 9.0 parts

[0253] Antioxidants: 3.0 parts

[0254] Lubricating corrosion inhibitor: 2.0 parts

[0255] Dispersant: 2.0 parts

[0256] Barite: Add to the drilling fluid density of 2.00g / cm 3 .

[0257] Among them, water is fresh water.

[0258] The pH regulator is a mixture of magnesium oxide and polyetheramine;

[0259] The pH regulator is composed of 75 parts of magnesium oxide and 25 parts of polyetheramine based on 100 parts by mass;

[0260] The viscosity-enhancing coating agent is a compound of betaine derivatives and polyethyleneimine;

[0261] The viscosity-enhancing coating agent is composed of 75 parts of betaine derivative and 25 parts of polyethyleneimine based on 100 parts by mass;

[0262] The preparation method of the above betaine derivative comprises the following steps:

[0263] First, 50 parts by weight of arachidonic acid and 9 parts by weight of potassium hydroxide were added to a four-necked round-bottom flask, and nitrogen was passed through to deoxygenate after stirring for 25 minutes. Then, 21 parts by weight of dimethylaminopropylamine were added dropwise, and the temperature was raised to 155° C. to start the reaction. After 7 hours, the heating was stopped and the mixture was cooled to room temperature. The remaining dimethylaminopropylamine was removed by vacuum distillation, and then the remaining arachidonic acid was removed by multiple washings with a dilute alkaline aqueous solution to obtain an intermediate product A.

[0264] Secondly, 18 parts by weight of epichlorohydrin was added to a three-necked round-bottom flask containing 180 parts by weight of a 90% ethanol aqueous solution, and after stirring for 27 minutes, 10 parts by weight of aspartic acid was added, and the temperature was raised to 48° C. to start the reaction, which lasted for 5.5 hours, and the heating was stopped and cooled to room temperature to obtain an intermediate product B;

[0265] Again, the intermediate product A was added to the flask containing the intermediate product B, and after stirring for 35 minutes, nitrogen was passed to deoxygenate, the temperature was raised to 82°C, the reaction was continued for 15 hours, the heating was stopped and the mixture was cooled to room temperature, and the solvent was removed by a rotary evaporator to obtain the target product, a betaine derivative.

[0266] The fluid loss reducer is a compound of carboxymethyl cellulose, carboxymethyl starch and potassium humate;

[0267] The fluid loss reducer is composed of 100 parts by mass of carboxymethyl cellulose, 45 parts by mass of carboxymethyl starch and 45 parts by mass of potassium humate;

[0268] Carboxymethyl starch is produced by compounding wheat starch, potato starch and cassava starch and then carboxymethylating them.

[0269] The starch raw materials used for the carboxymethyl starch are composed of 40 parts of wheat starch, 30 parts of potato starch and 30 parts of cassava starch based on 100 parts by mass.

[0270] The preparation method of carboxymethyl starch is the same as the preparation method of carboxymethyl starch in Example 1.

[0271] The plugging agent is a mixture of nano calcium carbonate, nano zinc oxide and nano aluminum oxide;

[0272] The plugging agent is composed of 75 parts of nano calcium carbonate, 10 parts of nano zinc oxide and 15 parts of nano aluminum oxide based on 100 parts by mass;

[0273] The auxiliary inhibitor is a compound of potassium chloride and sodium formate;

[0274] The auxiliary inhibitor is composed of 55 parts of potassium chloride and 45 parts of sodium formate based on 100 parts by mass;

[0275] The antioxidant is a compound of catechin, rutin, sodium D-isoascorbate and polyethylene glycol;

[0276] The antioxidant is composed of 10 parts by weight of catechins, 5 parts by weight of rutin, 40 parts by weight of sodium D-isoascorbate and 45 parts by weight of polyethylene glycol;

[0277] The lubricating corrosion inhibitor is obtained by the following preparation method:

[0278] First, 13 parts by weight of glutamic acid and 16 parts by weight of glucose were dissolved in 100 parts by weight of deionized water, and then transferred to a Teflon high-temperature autoclave, heated to 195°C for 9 hours, cooled to room temperature, filtered using a 0.22 μm filter membrane, and then the filtrate obtained by filtration was placed in a 500 Da dialysis bag for 42 hours, the water was changed every 6 hours, and then the solvent was removed by rotary evaporation, and the intermediate product A was obtained by vacuum drying;

[0279] Secondly, the intermediate product A was added to a three-necked round-bottom flask containing 100 parts by mass of a 90% ethanol aqueous solution, and after stirring for 25 minutes, 28 parts by mass of chlorododecane was added, and after nitrogen was passed through to deoxygenate, the temperature was raised to 75°C, and after reacting for 11 hours, the heating was stopped and the mixture was cooled to room temperature, and the solvent was removed by rotary evaporation to obtain the intermediate product B;

[0280] Finally, the intermediate product B was mixed with 30 parts by mass of oleic acid imidazoline and 35 parts by mass of ricinoleic acid diethanolamide and stirred for 2.5 hours to obtain the target product, a lubricating corrosion inhibitor.

[0281] The dispersant is a compound of AKN-1070, AKN-2200, AKN-2263 and AKN-2350;

[0282] The dispersant is composed of 20 parts of AKN-1070, 10 parts of AKN-2200, 40 parts of AKN-2263 and 30 parts of AKN-2350 based on 100 parts by mass.

[0283] The preparation method of the above-mentioned clay-free calcium chloride water-based drilling fluid comprises the following steps:

[0284] According to the mass fraction, water is first added into the container, and calcium chloride is added into the container at a stirring speed of 10000r / min, and stirred for 10 minutes; the auxiliary inhibitor is continued to be added, and stirred for 3 minutes; the pH adjuster is continued to be added, and stirred for 5 minutes; the viscosity increasing coating agent is continued to be added, and stirred for 25 minutes; the antioxidant is continued to be added, and stirred for 5 minutes; the filtrate reducer is slowly added, and stirred for 20 minutes; the plugging agent is continued to be added, and stirred for 10 minutes; the lubricating corrosion inhibitor is continued to be added, and stirred for 20 minutes; the dispersant is continued to be added, and stirred for 5 minutes; finally, barite is added, and stirred for 35 minutes to obtain the clay-free calcium chloride water-based drilling fluid.

[0285] The drilling fluid density prepared in this example is 2.00 g / cm 3 , the drilling fluid aging temperature is 150℃.

[0286] Comparative Example 1

[0287] The only difference from Example 5 is that the pH adjuster is replaced by a compound of sodium hydroxide and sodium carbonate (consisting of 50 parts of sodium hydroxide and 50 parts of sodium carbonate based on 100 parts by mass), and the other parameters and steps remain unchanged.

[0288] Comparative Example 2

[0289] The only difference from Example 5 is that the lubricating corrosion inhibitor is replaced by a conventional vegetable oil lubricant, and the other parameters and steps remain unchanged.

[0290] Comparative Example 3

[0291] The only difference from Example 5 is that the viscosity-enhancing coating agent is replaced by xanthan gum, and the other parameters and steps remain unchanged.

[0292] The drilling fluids obtained in the above examples and comparative examples were tested for basic performance, inhibition performance, corrosion inhibition performance and lubrication performance with reference to GB / T 29170-2012 "Laboratory Test of Drilling Fluids in Petroleum and Natural Gas Industry", GB / T 18175-2014 "Determination of Corrosion Inhibition Performance of Water Treatment Agents - Rotating Hanging Plate Method" and SY / T6094-1994 "Evaluation Procedure for Lubricants for Drilling Fluids". The results are shown in Tables 1 and 2.

[0293] Table 1 Basic properties of drilling fluid

[0294]

[0295]

[0296] Table 2 Drilling fluid inhibition, lubrication and corrosion inhibition properties

[0297] Drilling Fluid <![CDATA[δ1]]> <![CDATA[δ2]]> <![CDATA[δ3]]> <![CDATA[δ4]]> θ γ EP <![CDATA[C R ]]> Example 1 2.3 4.7 9.3 16.3 96.6 3.9 0.0618 0.037 Example 2 1.7 3.4 5.2 6.9 99.1 1.1 0.0412 0.042 Example 3 1.6 4.9 8.2 13.1 97.8 2.7 0.0534 0.049 Example 4 1.5 4.5 7.6 12.1 98.9 2.3 0.0565 0.051 Example 5 2.6 5.1 7.7 10.3 99.7 1.6 0.0600 0.045 Comparative Example 1 3.2 6.5 9.7 16.1 85.3 2.2 0.0825 0.069 Comparative Example 2 5.4 10.8 14.9 21.6 97.2 2.3 0.2071 0.458 Comparative Example 3 2.8 5.6 8.3 11.1 79.5 1.8 0.0922 0.056

[0298] It can be seen from Examples 1 to 5 that the clay-free calcium chloride water-based drilling fluid provided by the present invention has a density of 1.20 to 2.00 g / cm 3 range, and the aging temperature is in the range of 70 to 150°C. They all have good and stable rheology, low filtration loss, excellent inhibition, excellent lubrication ability and reliable corrosion inhibition performance. It can be seen from Example 5 and Comparative Example 1 that after the pH adjuster is replaced with conventional sodium hydroxide and sodium carbonate, the viscosity and shear force of the drilling fluid are greatly reduced, and it no longer has the ability to suspend barite. At the same time, the filtration loss increases significantly, indicating that sodium hydroxide and sodium carbonate are incompatible with the calcium chloride system. The pH adjuster provided by the present invention not only ensures a stable and appropriate pH value, but also solves the compatibility problem. It can be seen from Example 5 and Comparative Example 2 that after the lubricating corrosion inhibitor is replaced with a conventional vegetable oil lubricant, the extreme pressure friction coefficient of the drilling fluid is significantly increased, the lubrication performance is significantly reduced, and the corrosion rate is greatly increased, which is obviously dissatisfied. It is lower than the standard requirement of 0.076 mm / a, which shows that the lubricating corrosion inhibitor provided by the present invention can solve the problem that conventional vegetable oil lubricants are not suitable for calcium chloride drilling fluids on the one hand, and on the other hand, it also has excellent corrosion inhibition performance; it can be seen from Example 5 and Comparative Example 3 that after the viscosity-enhancing coating agent is replaced with xanthan gum, the dynamic plastic ratio of the drilling fluid decreases by 100%, the shear thinning behavior almost disappears, the filtration loss is significantly increased, and the mudstone rolling recovery rate is significantly reduced, indicating that the viscosity-enhancing coating agent provided by the present invention has excellent temperature-resistant and calcium-resistant viscosity-enhancing coating properties, and gives the high calcium chloride-containing clay-free phase drilling fluid good rheological properties.

[0299] The invention discloses five groups of embodiments of a calcium chloride water-based drilling fluid without a clay phase. After aging in a wide density and temperature range, the fluid has the following characteristics: a moderate and stable pH value, excellent rheological properties, low plastic viscosity, and a dynamic-plastic ratio higher than 0.5, showing good sand suspension and sand carrying capacity; excellent fluid loss reduction performance, with API and HTHP fluid loss amounts lower than 4.0 mL and 14.0 mL, respectively; a high capacity limit of inferior solid phase, with an apparent viscosity increase rate lower than 5% after 10% sodium-based bentonite contamination, and when the sodium-based bentonite contamination concentration reaches 40%, the apparent viscosity increase rate of the system is still lower than 20%; a significant effect of inhibiting the hydration of clay, with a mudstone rolling recovery rate higher than 96%, and a linear expansion rate lower than 4%; excellent friction and drag reduction performance, with an extreme pressure friction coefficient significantly lower than 0.1, and suitable for directional well and horizontal well operations; and a corrosion rate lower than 0.076 mm / a, and corrosion inhibition performance that meets operational requirements.

[0300] Note:

[0301] ρ: drilling fluid density, g / cm 3

[0302] T: Drilling fluid aging temperature, °C

[0303] AV: drilling fluid apparent viscosity, mPa·s

[0304] PV: drilling fluid plastic viscosity, mPa·s

[0305] YP: Drilling fluid dynamic shear force, Pa

[0306] YP / PV: Dynamic plastic ratio, Pa / mPa·s

[0307] Φ6: Six-speed rotary viscometer 6-turn reading, dimensionless

[0308] Φ3: Six-speed rotary viscometer 3-turn reading, dimensionless

[0309] API: Drilling fluid medium pressure loss (0.7MPa, room temperature, 30min), mL

[0310] HTHP: Drilling fluid high temperature and high pressure filtration loss (3.5MPa, T, 30min), mL

[0311] EP: Extreme pressure friction coefficient, dimensionless

[0312] δ1: Apparent viscosity increase rate after 10% sodium bentonite contamination, %

[0313] δ2: Apparent viscosity increase rate after 20% sodium bentonite contamination, %

[0314] δ3: Apparent viscosity increase rate after 30% sodium bentonite contamination, %

[0315] δ4: Apparent viscosity increase rate after 40% sodium bentonite contamination, %

[0316] θ: Mudstone rolling recovery rate, %

[0317] γ: Clay linear expansion rate, %

[0318] C R :N80 steel sheet corrosion rate (normal pressure, T, 24h), mm / a

[0319] The embodiments described above are only descriptions of the preferred modes of the present invention, and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should all fall within the protection scope determined by the claims of the present invention.

Claims

1. A clay-free calcium chloride water-based drilling fluid, characterized in that: The raw materials include by weight: Water: 100 parts Calcium chloride: 40-100 parts pH adjuster: 2.0-3.0 parts Thickening coating agent: 2.0-3.0 parts Fluid loss reducer: 3.0-5.0 parts Plugging agent: 1.0-1.5 parts Auxiliary inhibitor: 5.0~10.0 parts Antioxidant: 2.0-3.0 parts Lubricating corrosion inhibitor: 1.0~2.0 parts Dispersant: 1.0-2.0 parts Barite: unlimited amount, added until the density of calcium chloride water-based drilling fluid without clay phase is 1.20-2.00 g / cm 3 That's it.

2. The clay-free calcium chloride water-based drilling fluid according to claim 1, characterized in that: The water is fresh water and / or sea water; The pH regulator is composed of 60 to 80 parts of magnesium oxide and 20 to 40 parts of polyether amine by mass.

3. The clay-free calcium chloride water-based drilling fluid according to claim 1, characterized in that: The viscosity-enhancing coating agent is composed of 60 to 80 parts of betaine derivatives and 20 to 40 parts of polyethyleneimine by weight; The preparation method of the betaine derivative comprises the following steps: 30-60 parts by weight of arachidonic acid and 5-10 parts by weight of potassium hydroxide are mixed and then deoxygenated by nitrogen. Then 12-24 parts by weight of dimethylaminopropylamine are added and the temperature is raised to 140-160° C. to react for 5-8 hours. Then the mixture is cooled to room temperature, distilled under reduced pressure, and washed to obtain an intermediate product A. 10 to 20 parts by weight of epichlorohydrin are added to 100 to 200 parts by weight of a 90 wt% ethanol aqueous solution and mixed, then 6 to 12 parts by weight of aspartic acid are added, the temperature is raised to 40 to 50° C., the reaction is performed for 4 to 6 hours, and then the mixture is cooled to room temperature to obtain an intermediate product B; The intermediate product A is added to the intermediate product B and mixed, and then nitrogen is passed to deoxygenate. The temperature is raised to 75-85° C. to react for 10-16 hours, and then cooled to room temperature. The solvent is removed by rotary evaporation to obtain the betaine derivative.

4. The clay-free calcium chloride water-based drilling fluid according to claim 1, characterized in that: The fluid loss reducer is composed of 5 to 10 parts of carboxymethyl cellulose, 40 to 50 parts of carboxymethyl starch and 40 to 55 parts of potassium humate in parts by mass; The raw materials of the carboxymethyl cellulose are composed of 50 to 70 parts of peanut shell cellulose, 20 to 30 parts of corn cymbidium cellulose and 10 to 20 parts of sugarcane bagasse cellulose by weight. The carboxymethyl cellulose is prepared by compounding peanut shell cellulose, corn platycodon cellulose and sugarcane bagasse cellulose in proportions by mass and then performing carboxymethylation. The raw materials of the carboxymethyl starch are composed of 30 to 40 parts of wheat starch, 30 to 40 parts of potato starch and 20 to 40 parts of cassava starch by weight; The carboxymethyl starch is prepared by compounding wheat starch, potato starch and cassava starch according to mass proportions and then performing carboxymethylation production.

5. The clay-free calcium chloride water-based drilling fluid according to claim 1, characterized in that: The plugging agent is composed of 60 to 80 parts by mass of nano calcium carbonate, 10 to 20 parts by mass of nano zinc oxide and 10 to 20 parts by mass of nano aluminum oxide; The auxiliary inhibitor is composed of 40 to 60 parts of potassium chloride and 40 to 60 parts of sodium formate by mass.

6. The clay-free calcium chloride water-based drilling fluid according to claim 1, characterized in that: The antioxidant consists of 5 to 10 parts of catechins, 5 to 10 parts of rutin, 30 to 40 parts of sodium D-isoascorbate and 40 to 60 parts of polyethylene glycol in parts by mass.

7. The clay-free calcium chloride water-based drilling fluid according to claim 1, characterized in that: The preparation method of the lubricating corrosion inhibitor comprises the following steps: 7-15 parts by weight of glutamic acid and 10-18 parts by weight of glucose are dissolved in 100 parts by weight of deionized water, followed by hydrothermal reaction at 180-200° C. for 6-10 hours, cooled to room temperature and filtered, and the filtrate obtained by filtration is placed in a 500Da dialysis bag for 24-48 hours, with water replaced every 6 hours, and then the solvent is removed by rotary evaporation, and vacuum dried to obtain an intermediate product A; The intermediate product A is added to 100 parts by weight of 90 wt% ethanol aqueous solution, stirred for 10 to 30 minutes, and then 20 to 30 parts by weight of chlorododecane is added. After nitrogen is passed through to deoxygenate, the temperature is raised to 60 to 80° C., and after reacting for 8 to 12 hours, the heating is stopped and the mixture is cooled to room temperature, and then the solvent is removed by rotary evaporation to obtain the intermediate product B; The intermediate product B is mixed with 20 to 30 parts by weight of oleic acid imidazoline and 30 to 40 parts by weight of ricinoleic acid diethanolamide and stirred for 1 to 3 hours to obtain the lubricating corrosion inhibitor.

8. The clay-free calcium chloride water-based drilling fluid according to claim 1, characterized in that: The dispersant consists of 10 to 20 parts of AKN-1070, 10 to 20 parts of AKN-2200, 30 to 40 parts of AKN-2263 and 20 to 50 parts of AKN-2350.

9. A method for preparing a clay-free calcium chloride water-based drilling fluid according to any one of claims 1 to 8, characterized in that: The following steps are involved: Calcium chloride, auxiliary inhibitor, pH regulator, viscosity enhancing coating agent, antioxidant, fluid loss reducer, plugging agent, lubricating corrosion inhibitor, dispersant and barite are added to water in order by mass under stirring to prepare the clay-free calcium chloride water-based drilling fluid.

10. Use of the clay-free calcium chloride water-based drilling fluid according to any one of claims 1 to 8 in oil and gas drilling projects.

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