阅读说明：本技术 高温水基钻井液及其制备方法 (High-temperature water-based drilling fluid and preparation method thereof ) 是由 孟虎 刘亚东 朱国伟 吴骏峰 于 2019-11-27 设计创作，主要内容包括：本发明公开了一种高温水基钻井液,按重量份计的103-104份基浆、1-1.5份降滤失剂Ⅰ、1.5-2份降滤失剂Ⅱ、2-2.5份降滤失剂Ⅲ、2份聚乙二醇、1-1.5份胺基硅醇、3-5份氯化钾、2-2.5份润滑剂、0.6-1份600-800目的碳酸钙粉末、1.2-1.5份400-500目改性硅藻土,及添加量为使高温水基钻井液加重至1.4-1.7g/cm<Sup>3</Sup>的重晶石。本发明还公开了一种高温水基钻井液的制备方法。本发明具有抗高温、降低钻井液渗透率、滤失量的有益效果。(The invention discloses a high-temperature water-based drilling fluid which comprises, by weight, 103-104 parts of base slurry, 1-1.5 parts of a fluid loss additive I, 1.5-2 parts of a fluid loss additive II, 2-2.5 parts of a fluid loss additive III, 2 parts of polyethylene glycol, 1-1.5 parts of amino silanol, 3-5 parts of potassium chloride, 2-2.5 parts of a lubricant, 0.6-1 part of 800-mesh calcium carbonate powder with 600-fold materials, 1.2-1.5 parts of 500-mesh modified diatomite with 400-fold materials, and the addition amount is such that the high-temperature water-based drilling fluid is weighted to 1.4-1.7g/cm 3 The barite of (1). The invention also discloses a preparation method of the high-temperature water-based drilling fluid. The invention has the advantages of high temperature resistance, and reduction of the permeability and the filtration loss of the drilling fluid.)

1. A high temperature water-based drilling fluid, comprising: 103-104 parts of base slurry, 1-1.5 parts of fluid loss additive I, 1.5-2 parts of fluid loss additive II, 2-2.5 parts of fluid loss additive III, 2 parts of polyethylene glycol, 1-1.5 parts of amino silanol, 3-5 parts of potassium chloride, 2-2.5 parts of lubricant, 0.6-1 part of 600-mesh calcium carbonate powder, 1.2-1.5 parts of 400-mesh modified diatomite and the addition amount of the high-temperature water-based drilling fluid is increased to 1.4-1.7g/cm³The barite of (a);

wherein, the filtrate reducer I is a graft copolymer taking corrosive acid as a framework;

the fluid loss agent II is a composition taking the calcium carbonate powder with the particle size of 1000-2000 meshes as a fluid loss agent I and the calcium carbonate powder with the particle size of 1000-2000 meshes as cores and the asphalt with the middle softening point as a shell, wherein the softening point of the asphalt with the middle softening point is 80-150 ℃, and the mass ratio of the calcium carbonate powder with the particle size of 1000-2000 meshes to the asphalt with the middle softening point is 1:1: 0.8;

the fluid loss agent III is a composition which takes a fluid loss agent I as a core, high-softening-point asphalt as a semi-coated inner shell and medium-softening-point asphalt as an outer shell, wherein the softening point of the high-softening-point asphalt is 160-260 ℃, and the mass ratio of the fluid loss agent I to the high-softening-point asphalt to the medium-softening-point asphalt is 1:0.3: 0.3.

2. The high temperature water-based drilling fluid of claim 1, wherein the base slurry comprises water, calcareous bentonite, sodium carbonate and sodium hydroxide in a mass ratio of 100:2:0.1: 0.2.

3. The high temperature water-based drilling fluid of claim 2, wherein the base slurry further comprises sodium chloride, and the mass ratio of the sodium chloride to the calcareous bentonite is 1: 1.

4. A method of preparing a high temperature water-based drilling fluid as claimed in any of claims 1 to 3, comprising the steps of:

s1, preparing a filtrate reducer II: adding the medium softening point asphalt into an asphalt tank, heating to dissolve, stirring and mixing uniformly, adding the filtrate reducer I and 2000-mesh calcium carbonate powder, stirring to fully mix, cooling, and crushing to 400-mesh 500-mesh powder;

s2, preparing a filtrate reducer III: adding the asphalt with the high softening point into an asphalt tank, heating to dissolve the asphalt, paving the asphalt layer with the height of 2-3 mu m, uniformly paving the filtrate reducer I on the asphalt layer, cooling and crushing the asphalt layer to 800 meshes to obtain a semi-coated filtrate reducer I; adding the pitch with the medium softening point into a pitch tank, heating to dissolve, adding the semi-coated filtrate reducer I, stirring to fully mix, cooling, and crushing to 400-mesh and 500-mesh powder;

s3, sequentially adding a fluid loss additive I, a fluid loss additive II, a fluid loss additive III, polyethylene glycol, amino silanol, potassium chloride, a lubricant, 800-mesh calcium carbonate powder prepared from 600-mesh and 500-mesh modified diatomite into the base slurry, and uniformly stirring to obtain a glue solution;

s4, adding barite into the glue solution and weighting the weight of the high-temperature water-based drilling fluid to 1.4-1.7g/cm³Stirring and mixing uniformly to obtain the high-temperature water-based drilling fluid;

wherein the stirring rate is 10000-12000 r/min.

5. The preparation method of the high-temperature water-based drilling fluid as claimed in claim 4, wherein the preparation method of the base slurry comprises the following specific steps: adding sodium hydroxide into water according to the parts by weight, stirring for 20min, standing for 2h, then adding calcareous bentonite and sodium carbonate, stirring for 20min, and standing for 24h to obtain base slurry.

6. The preparation method of the high-temperature water-based drilling fluid as claimed in claim 5, wherein the step of standing for 24 hours in the process of preparing the base slurry further comprises the steps of adding 2-3 parts of sodium chloride, stirring for 20 minutes, and standing for 24 hours to obtain the base slurry.

Technical Field

The invention relates to the field of preparation of water-based drilling fluid. More particularly, the invention relates to a high-temperature water-based drilling fluid and a preparation method thereof.

Background

Rotary drilling is the most common drilling technique used in oil fields today, and during drilling, cuttings are deposited and must be continuously removed from the vicinity of the drill bit at the bottom of the hole in order to facilitate continued drilling. Drilling fluid is pumped down the borehole through the drill pipe and out through nozzles in the drill bit to carry the cuttings down the borehole to the surface through the annulus between the formation and the drill pipe. Drilling fluids can be classified as water-based, oil-based, synthetic-based, foam-based, gas-based, and the like, depending on the fluid medium. Water-based drilling fluids are preferred for economic, environmental, etc. reasons.

Water exists in the drilling fluid in three forms (combination state, adsorbed water and free water) as a dispersion medium of the water-based drilling fluid, and the free water in the drilling fluid permeates into cracks or pores of rock on a well wall under the action of pressure difference, which is called the fluid loss action of the drilling fluid. During fluid loss, particles in the drilling fluid can form three zones in the well wall and the stratum: an outer filter cake on the wellbore wall, an inner filter cake formed by particles entering the formation, and a primary damage invasion zone formed by fine particle invasion during primary damage of the drilling fluid. When the filtration loss is increased, a filter cake is thickened, the well diameter is reduced, large torque is caused to a rotating drilling tool, and pressure fluctuation caused during tripping and descending easily causes differential pressure sticking, so the filtration loss protection is a key characteristic of the performance of drilling fluid. At present, the fluid loss reducing effect of the drilling fluid can be effectively improved by adding a treating agent (such as conventional polymers such as cellulose, XC and polyacrylamide), but the temperature resistance of the conventional polymers such as the cellulose, XC and polyacrylamide is generally less than 150 ℃. However, with the deep development of oil drilling, the bottom temperature is higher and higher (>180 ℃), and the conventional drilling fluid is easy to degrade, crosslink and dehydrate at high temperature, so that the conditions of high-temperature thickening, mud cake thickening, filtration loss increase and the like are caused. Furthermore, the treating agent is modified to adapt to a high-temperature environment, for example, a graft copolymer which is obtained by modifying a corrosive acid treating agent and takes corrosive acid as a framework has good salt and pollution resistance and thermal stability, but the substance has a good viscosity reduction effect because the substance contains stronger hydrated groups such as a sodium carboxylate group and the like with a hydration effect, the moderate viscosity reduction can improve the fluidity of the water-based drilling fluid, but the excessive viscosity can cause the uniformity of the solid-containing water-based drilling fluid to have a problem, and how to meet the use amount to meet the requirement of the drilling fluid in the whole flowing circulation process and avoid the problem, namely how to ensure the overall performance of the drilling fluid, reduce the permeability and the filtration loss of the drilling fluid and form a thin and compact mud cake is a problem which needs to be solved at present.

Disclosure of Invention

An object of the present invention is to solve at least the above problems and to provide at least the advantages described later.

It is yet another object of the present invention to provide a high temperature water-based drilling fluid that is resistant to high temperatures, reduces drilling fluid permeability, and reduces fluid loss.

Still another object of the present invention is to provide a method for preparing a high temperature water-based drilling fluid, which can prepare a high temperature water-based drilling fluid and achieve effective coating of fluid loss additives ii and iii.

To achieve these objects and other advantages in accordance with the present invention, there is provided a high temperature water-based drilling fluid comprising, by weight, 103-³The barite of (a);

wherein, the filtrate reducer I is a graft copolymer taking corrosive acid as a framework;

the fluid loss agent II is a composition taking the calcium carbonate powder with the particle size of 1000-2000 meshes as a fluid loss agent I and the calcium carbonate powder with the particle size of 1000-2000 meshes as cores and the asphalt with the middle softening point as a shell, wherein the softening point of the asphalt with the middle softening point is 80-150 ℃, and the mass ratio of the calcium carbonate powder with the particle size of 1000-2000 meshes to the asphalt with the middle softening point is 1:1: 0.8;

the fluid loss agent III is a composition which takes a fluid loss agent I as a core, high-softening-point asphalt as a semi-coated inner shell and medium-softening-point asphalt as an outer shell, wherein the softening point of the high-softening-point asphalt is 160-260 ℃, and the mass ratio of the fluid loss agent I to the high-softening-point asphalt to the medium-softening-point asphalt is 1:0.3: 0.3.

Preferably, the base slurry comprises water, calcium bentonite, sodium carbonate and sodium hydroxide in a mass ratio of 100:2:0.1: 0.2.

Preferably, the base slurry further comprises sodium chloride, and the mass ratio of the sodium chloride to the calcareous bentonite is 1: 1.

A preparation method of a high-temperature water-based drilling fluid comprises the following steps:

s1, preparing a filtrate reducer II: adding the medium softening point asphalt into an asphalt tank, heating to dissolve, stirring and mixing uniformly, adding the filtrate reducer I and 2000-mesh calcium carbonate powder, stirring to fully mix, cooling, and crushing to 400-mesh 500-mesh powder;

s2, preparing a filtrate reducer III: adding the asphalt with the high softening point into an asphalt tank, heating to dissolve the asphalt, paving the asphalt layer with the height of 2-3 mu m, uniformly paving the filtrate reducer I on the asphalt layer, cooling and crushing the asphalt layer to 800 meshes to obtain a semi-coated filtrate reducer I; adding the pitch with the medium softening point into a pitch tank, heating to dissolve, adding the semi-coated filtrate reducer I, stirring to fully mix, cooling, and crushing to 400-mesh and 500-mesh powder;

s3, sequentially adding a fluid loss additive I, a fluid loss additive II, a fluid loss additive III, polyethylene glycol, amino silanol, potassium chloride, a lubricant, 800-mesh calcium carbonate powder prepared from 600-mesh and 500-mesh modified diatomite into the base slurry, and uniformly stirring to obtain a glue solution;

s4, adding barite into the glue solution and weighting the weight of the high-temperature water-based drilling fluid to 1.4-1.7g/cm³Stirring and mixing uniformly to obtain the high-temperature water-based drilling fluid;

wherein the stirring rate is 10000-12000 r/min.

Preferably, the preparation method of the base pulp comprises the following steps: adding sodium hydroxide into water according to the parts by weight, stirring for 20min, standing for 2h, then adding calcareous bentonite and sodium carbonate, stirring for 20min, and standing for 24h to obtain base slurry.

Preferably, the preparation method further comprises the steps of standing for 24 hours in the preparation process of the base slurry, adding 2-3 parts of sodium chloride, stirring for 20 minutes, and standing for 24 hours to obtain the base slurry.

The invention at least comprises the following beneficial effects:

the high-performance water-based drilling fluid is prepared by the combined action of base slurry, filtrate reducers I, II and III, polyethylene glycol, amino silanol, potassium chloride, a lubricant, 800-mesh calcium carbonate powder of 600-mesh, 2000-mesh calcium carbonate powder of 1000-mesh and barite, wherein:

the fluid loss agent I is a graft copolymer taking corrosive acid as a framework, can be generated by copolymerization with alkene monomers and the like after deep oxidation of humic acid, the alkene monomers are one of acrylic acid and acrylamide, and the fluid loss agent I can be HFL-H which is black powder and has good salt and pollution resistance, good thermal stability and temperature resistance effect of over 180 ℃;

the fluid loss additive II is a composition taking the calcium carbonate powder of the fluid loss additives I and 1000-mesh 2000-mesh as a core and the middle softening point asphalt as a shell, the fluid loss additive I can effectively reduce the adhesion effect of the fluid loss additive I on the drilling fluid in the preparation mixing and stirring stage and the initial introduction stage by wrapping the middle softening point asphalt so as to ensure the proper viscosity of the drilling fluid, the calcium carbonate powder of the fluid loss additives I and 1000-mesh 2000-mesh is gradually released along with the temperature rise of the drilling fluid introduced into a well as the softening point of the middle softening point asphalt is 80-150 ℃ and the middle softening point asphalt gradually breaks the shell when the drilling fluid enters a stage with the well temperature of 80-150 ℃, the released calcium carbonate powder I further acts on the drilling fluid to improve the performance change of the drilling fluid caused by the temperature rise, and simultaneously the calcium carbonate powder of 1000-mesh 2000-mesh is blocked by matching with the modified diatomite of 400-mesh 500-mesh and the calcium carbonate powder of 600-mesh 800-mesh, in the plugging process, as the 1000-plus 2000-mesh calcium carbonate powder belongs to the post-release product compared with the 400-plus 500-mesh modified diatomite and the 600-plus 800-mesh calcium carbonate powder, the excessive participation of the 1000-plus 2000-mesh calcium carbonate powder with smaller particle size in the formation of the initial damage invasion zone is effectively avoided, the formation possibility of the initial damage invasion zone is weakened, the 400-plus 500-mesh modified diatomite and the 600-plus 800-mesh calcium carbonate powder are firstly filled, and then the 1000-plus 2000-mesh calcium carbonate powder is used for matched filling, so that the sequence is gradual, the more the holes are blocked, the smaller the holes are, and the compactness of the filter cake is increased;

the filtrate reducer III is high-softening-point asphalt particles which take the filtrate reducer I as a core, high-softening-point asphalt as a semi-coated inner shell and medium-softening-point asphalt as an outer shell, and are not coated with core materials, when the filtrate reducer I enters a stage with a well temperature of 80-150 ℃, the medium-softening-point asphalt gradually breaks the shell to leak the filtrate reducer I coated with the high-softening-point asphalt in the filtrate reducer I, so that the filtrate reducer II is used for improving the performance change of drilling fluid caused by the temperature rise, and simultaneously the well temperature is higher than 150 ℃, and the high-softening-point asphalt, together with the high-softening-point asphalt particles, the high-softening-point asphalt and the filter reducer I coated in the high-softening-point asphalt promote the formation of a high-temperature layer mud cake; so as to improve the fluid loss effect of the drilling fluid in the whole circulation process;

in the preparation process of the base pulp, firstly, sodium hydroxide is utilized to pretreat the pulp preparation water, the pH value of the base pulp is adjusted, and Mg is removed²⁺Further preparing base slurry by using sodium carbonate and calcium bentonite to remove Ca²⁺The ions change the calcium bentonite into sodium bentonite, and the hydration and dispersion performance of the bentonite is improved;

the polyethylene glycol can inhibit the hydration and dispersion of the shale and prevent the well wall from collapsing;

the strong inhibition of polyamine in amino silanol and the film forming property of silanol can effectively improve the inhibition of the drilling fluid and keep the anti-pollution capability of the drilling fluid;

potassium chloride cooperates with polyethylene glycol to inhibit shale from dispersing, and K is⁺The silicon oxide can be embedded in the middle of a silicon oxide tetrahedron of clay minerals in an ion mode, enters between crystal layers and enters a cave of an adjacent oxygen layer, and the effect of stabilizing a well wall is achieved;

the lubricant is mainly used for improving the lubricity of mud and mud cakes and preventing sticking of stuck drills, and can be PF-LUBE.

Additional advantages, objects, and features of the invention will be set forth in part in the description which follows and in part will become apparent to those having ordinary skill in the art upon examination of the following or may be learned from practice of the invention.

Detailed Description

The present invention is further described in detail below with reference to examples so that those skilled in the art can practice the invention with reference to the description.

< example 1a >

A high temperature water-based drilling fluid comprising: 103 parts of base slurry, 1 part of fluid loss additive I, 1.5 parts of fluid loss additive II, 2 parts of fluid loss additive III, 2 parts of polyethylene glycol, 1 part of amino silanol, 3 parts of potassium chloride, 2 parts of lubricant, 0.6 part of 600-mesh 800-mesh calcium carbonate powder, 1.2 parts of 400-mesh 500-mesh modified diatomite and the addition amount of the additive is that the high-temperature water-based drilling fluid is weighted to 1.4g/cm³The barite of (a);

wherein the base slurry comprises water, calcium bentonite, sodium carbonate and sodium hydroxide in a mass ratio of 100:2:0.15: 0.2;

the filtrate reducer I is a graft copolymer taking corrosive acid as a framework;

the fluid loss agent II is a composition taking the calcium carbonate powder with the particle size of 1000-2000 meshes as a fluid loss agent I and the calcium carbonate powder with the particle size of 1000-2000 meshes as cores and the asphalt with the middle softening point as a shell, wherein the softening point of the asphalt with the middle softening point is 80-150 ℃, and the mass ratio of the calcium carbonate powder with the particle size of 1000-2000 meshes to the asphalt with the middle softening point is 1:1: 0.8;

the fluid loss agent III is a composition which takes a fluid loss agent I as a core, high-softening-point asphalt as a semi-coated inner shell and medium-softening-point asphalt as an outer shell, wherein the softening point of the high-softening-point asphalt is 180 DEG and 220 ℃, and the mass ratio of the fluid loss agent I to the high-softening-point asphalt to the medium-softening-point asphalt is 1:0.3: 0.3.

< example 1b >

The preparation method of the high-temperature water-based drilling fluid comprises the following steps according to the dosage of < example 1-a >:

s1, preparing a filtrate reducer II: adding the medium softening point asphalt into an asphalt tank, heating to dissolve, stirring and mixing uniformly, adding the filtrate reducer I and 2000-mesh calcium carbonate powder, stirring to fully mix, cooling, and crushing to 400-mesh 500-mesh powder;

s2, preparing a filtrate reducer III: adding asphalt with a high softening point into an asphalt tank, heating to dissolve, paving into an asphalt layer with the height (thickness) of 2-3 mu m, uniformly paving the filtrate reducer I on the asphalt layer, cooling and crushing to 800 meshes to obtain a semi-coated filtrate reducer I; adding the pitch with the medium softening point into a pitch tank, heating to dissolve, adding the semi-coated filtrate reducer I, stirring to fully mix, cooling, and crushing to 400-mesh and 500-mesh powder;

s3, adding sodium hydroxide into water according to parts by weight, stirring for 20min, standing for 2h, then adding calcium bentonite and sodium carbonate, stirring for 20min, and standing for 24h to obtain base slurry;

sequentially adding a filtrate reducer I, a filtrate reducer II, a filtrate reducer III, polyethylene glycol, amino silanol, potassium chloride, a lubricant, 800-mesh calcium carbonate powder and 400-mesh 500-mesh modified diatomite into the base slurry, and uniformly stirring to obtain a glue solution;

s4, adding barite into the glue solution and weighting the weight of the high-temperature water-based drilling fluid to 1.4g/cm³Stirring and mixing uniformly to obtain the high-temperature water-based drilling fluid;

wherein the stirring rate involved in the stirring is in the range of 10000-12000 r/min.

< example 2a >

A high temperature water-based drilling fluid comprising: 104 parts of base slurry, 1.5 parts of fluid loss additive I, 2 parts of fluid loss additive II, 2.5 parts of fluid loss additive III, 2 parts of polyethylene glycol, 1.5 parts of amino silanol, 5 parts of potassium chloride, 2.5 parts of lubricant, 1 part of 600-plus 800-mesh calcium carbonate powder, 1.5 parts of 400-plus 500-mesh modified diatomite, and the addition amount is that the high-temperature water-based drilling fluid is weighted to 1.4g/cm³The barite of (a);

wherein the base slurry comprises water, calcium bentonite, sodium carbonate and sodium hydroxide in a mass ratio of 100:2:0.15: 0.2;

the filtrate reducer I is a graft copolymer taking corrosive acid as a framework;

the fluid loss agent II is a composition taking the calcium carbonate powder with the particle size of 1000-2000 meshes as a fluid loss agent I and the calcium carbonate powder with the particle size of 1000-2000 meshes as cores and the asphalt with the middle softening point as a shell, wherein the softening point of the asphalt with the middle softening point is 80-150 ℃, and the mass ratio of the calcium carbonate powder with the particle size of 1000-2000 meshes to the asphalt with the middle softening point is 1:1: 0.8;

the fluid loss agent III is a composition which takes a fluid loss agent I as a core, high-softening-point asphalt as a semi-coated inner shell and medium-softening-point asphalt as an outer shell, wherein the softening point of the high-softening-point asphalt is 180 DEG and 220 ℃, and the mass ratio of the fluid loss agent I to the high-softening-point asphalt to the medium-softening-point asphalt is 1:0.3: 0.3.

< example 2b >

The preparation method of the high-temperature water-based drilling fluid comprises the following steps according to the dosage of < example 2-a >:

s1, preparing a filtrate reducer II: adding the medium softening point asphalt into an asphalt tank, heating to dissolve, stirring and mixing uniformly, adding the filtrate reducer I and 2000-mesh calcium carbonate powder, stirring to fully mix, cooling, and crushing to 400-mesh 500-mesh powder;

s2, preparing a filtrate reducer III: adding the asphalt with the high softening point into an asphalt tank, heating to dissolve the asphalt, paving the asphalt layer with the height of 2-3 mu m, uniformly paving the filtrate reducer I on the asphalt layer, cooling and crushing the asphalt layer to 800 meshes to obtain a semi-coated filtrate reducer I; adding the pitch with the medium softening point into a pitch tank, heating to dissolve, adding the semi-coated filtrate reducer I, stirring to fully mix, cooling, and crushing to 400-mesh and 500-mesh powder;

s3, adding sodium hydroxide into water according to parts by weight, stirring for 20min, standing for 2h, then adding calcium bentonite and sodium carbonate, stirring for 20min, and standing for 24h to obtain base slurry;

sequentially adding a filtrate reducer I, a filtrate reducer II, a filtrate reducer III, polyethylene glycol, amino silanol, potassium chloride, a lubricant, 800-mesh calcium carbonate powder and 400-mesh 500-mesh modified diatomite into the base slurry, and uniformly stirring to obtain a glue solution;

s4, adding barite into the glue solution and weighting the weight of the high-temperature water-based drilling fluid to 1.4g/cm³Stirring and mixing uniformly to obtain the high-temperature water-based drilling fluid;

wherein the stirring rate involved in the stirring is in the range of 10000-12000 r/min.

< example 3a >

A high temperature water-based drilling fluid comprising: 103 parts of base slurry, 1 part of fluid loss additive I, 1.5 parts of fluid loss additive II, 2 parts of fluid loss additive III, 2 parts of polyethylene glycol, 1 part of amino silanol, 3 parts of potassium chloride, 2 parts of lubricant, 0.6 part of 600-mesh 800-mesh calcium carbonate powder, 1.2 parts of 400-mesh 500-mesh modified diatomite and the addition amount of the additive is that the high-temperature water-based drilling fluid is weighted to 1.4g/cm³The barite of (a);

wherein the base slurry comprises water, calcium bentonite, sodium chloride, sodium carbonate and sodium hydroxide in a mass ratio of 100:2:2:0.1: 0.2;

the filtrate reducer I is a graft copolymer taking corrosive acid as a framework;

the fluid loss agent II is a composition taking the calcium carbonate powder with the particle size of 1000-2000 meshes as a fluid loss agent I and the calcium carbonate powder with the particle size of 1000-2000 meshes as cores and the asphalt with the middle softening point as a shell, wherein the softening point of the asphalt with the middle softening point is 80-150 ℃, and the mass ratio of the calcium carbonate powder with the particle size of 1000-2000 meshes to the asphalt with the middle softening point is 1:1: 0.8;

the fluid loss agent III is a composition which takes a fluid loss agent I as a core, high-softening-point asphalt as a semi-coated inner shell and medium-softening-point asphalt as an outer shell, wherein the softening point of the high-softening-point asphalt is 180 DEG and 220 ℃, and the mass ratio of the fluid loss agent I to the high-softening-point asphalt to the medium-softening-point asphalt is 1:0.3: 0.3.

< example 3b >

The preparation method of the high-temperature water-based drilling fluid comprises the following steps according to the dosage of < example 3-a >:

s1, preparing a filtrate reducer II: adding the medium softening point asphalt into an asphalt tank, heating to dissolve, stirring and mixing uniformly, adding the filtrate reducer I and 2000-mesh calcium carbonate powder, stirring to fully mix, cooling, and crushing to 400-mesh 500-mesh powder;

s2, preparing a filtrate reducer III: adding the asphalt with the high softening point into an asphalt tank, heating to dissolve the asphalt, paving the asphalt layer with the height of 2-3 mu m, uniformly paving the filtrate reducer I on the asphalt layer, cooling and crushing the asphalt layer to 800 meshes to obtain a semi-coated filtrate reducer I; adding the pitch with the medium softening point into a pitch tank, heating to dissolve, adding the semi-coated filtrate reducer I, stirring to fully mix, cooling, and crushing to 400-mesh and 500-mesh powder;

s3, adding sodium hydroxide into water according to parts by weight, stirring for 20min, standing for 2h, then adding calcium bentonite and sodium carbonate, stirring for 20min, standing for 24h, adding sodium chloride, stirring for 20min, and standing for 24h to obtain base slurry;

sequentially adding a filtrate reducer I, a filtrate reducer II, a filtrate reducer III, polyethylene glycol, amino silanol, potassium chloride, a lubricant, 800-mesh calcium carbonate powder and 400-mesh 500-mesh modified diatomite into the base slurry, and uniformly stirring to obtain a glue solution;

s4, adding barite into the glue solution and weighting the weight of the high-temperature water-based drilling fluid to 1.4g/cm³Stirring and mixing uniformly to obtain the high-temperature water-based drilling fluid;

wherein the stirring rate involved in the stirring is in the range of 10000-12000 r/min.

< comparative example 1>

An aqueous based drilling fluid comprising: 103 parts of base slurry, 1 part of fluid loss additive I, 2 parts of polyethylene glycol, 1 part of amino silanol, 3 parts of potassium chloride, 2 parts of lubricant, 0.6 part of 800-mesh calcium carbonate powder with 600-mesh and 1.2 parts of 500-mesh modified diatomite, and the addition amount is that the high-temperature water-based drilling fluid is weighted to 1.4g/cm³The barite of (a);

wherein the base slurry comprises water, calcium bentonite, sodium carbonate and sodium hydroxide in a mass ratio of 100:2:0.15: 0.2;

the fluid loss additive I is a graft copolymer taking corrosive acid as a framework.

The preparation method of the high-temperature water-based drilling fluid comprises the following steps:

s1, adding sodium hydroxide into water according to parts by weight, stirring for 20min, standing for 2h, then adding calcium bentonite and sodium carbonate, stirring for 20min, and standing for 24h to obtain base slurry;

sequentially adding a fluid loss additive I, polyethylene glycol, amino silanol, potassium chloride, a lubricant, 800-mesh calcium carbonate powder of 600-mesh and 500-mesh modified diatomite into the base slurry, and uniformly stirring to obtain a glue solution;

s4, adding barite into the glue solution and weighting the weight of the high-temperature water-based drilling fluid to 1.4g/cm³Stirring and mixing uniformly to obtain the high-temperature water-based drilling fluid;

wherein the stirring rate involved in the stirring is in the range of 10000-12000 r/min.

1: environmental protection performance detection

1.1, according to the technical requirement of environmental protection of water-soluble oilfield chemical (SY/T6788-:

TABLE 1 heavy Metal content determination (unit: mg/L)

Detecting items

Hexavalent chromium

Copper (Cu)

Zinc

Lead (II)

Cadmium (Cd)

Arsenic (As)

Standard of sewage discharge

0.5

0.5 (grade 1)

2.0(1 level)

1

0.1

0.5

The result of the detection

＜0.004

0.02

0.10

＜0.08

＜0.009

0.0008

Detecting items

Mercury

Selenium

Chromium (III)

Silver (Ag)

Nickel (II)

Beryllium (beryllium)

Standard of sewage discharge

0.05

0.1

1.5

0.5

1

0.005

The result of the detection

0.009

＜0.0008

＜0.03

＜0.02

0.02

＜0.001

TABLE 2 biotoxicity degradation assay

Note: semi-effective concentration EC₅₀Means the concentration of the product when the luminescence of the luminescent bacteria is reduced by half, according to EC₅₀The biological toxicity is divided into virulent (less than 1mg/L), heavy toxicity (1-100mg/L), poisoning (101->20000mg/L) five grades; according to the formula Y ═ BOD₅The biodegradability of the/CODcr is divided into three grades of easy (Y is more than or equal to 0.05%), difficult (Y is more than or equal to 0.01% and less than 0.05%) and difficult (Y is less than 0.01%);

as can be seen from Table 1-2, the fluid loss additive I (HFL-H) is determined to be non-toxic and easily degradable and meet the environmental protection requirements by the environmental protection performance detection of SY/T6788-2010.

1.2, according to the technical requirement of environmental protection of water-soluble oilfield chemical (SY/T6788-:

TABLE 3 biotoxicity and degradability assays

Product(s)	EC50(mg/L)	Grade of toxicity	BOD5/CODcr(％)	Grade of degradability
					Example 1	50275	Is non-toxic	26.51	Easy to use
Example 2	46029	Is non-toxic	22.37	Easy to use
					Example 3	48801	Is non-toxic	19.46	Easy to use

As shown in Table 3, the biological toxicity and the biological degradability of the products prepared in examples 1-3 are determined to meet the environmental protection technical requirements of the water-soluble oilfield chemical through the biological toxicity and biological degradability measurement of SY/T6788-2010.

2: evaluation of fluid loss Effect

The rheological parameters (funnel viscosity (AV/mPas), plastic viscosity (PV/mPas), dynamic shear force (YP/Pa) and fluid loss (FL/Pa) of the products of examples 1b, 2b, 3b and comparative example 1 before and after aging at different temperatures were measured_API/mL) and high temperature and high pressure fluid loss FL_HTHP(mL), as shown in the following Table:

TABLE 4

From the above table, it can be seen that in the fresh water base slurry (example 1b) the AV of the drilling fluid at room temperature is equal to 25.5mPa · s, and in the brine base slurry (example 3b) the AV of the drilling fluid at room temperature is equal to 23.7mPa · s, both of which are comparable to the AV at room temperature of comparative example 1, indicating that the addition of fluid loss additives ii, iii has little effect on the fluidity of the drilling fluid itself at room temperature;

AV equal to 24.6 mPas, FL for example 1b after 160 ℃/16h ageing_API8.5mL, FL_HTHP20.2 mL; AV of example 3b equal to 22.8 mPas, FL_API8.2mL, FL_HTHP19.6mL, while the AV of comparative example 1 is equal to 27.3 mPas, FL_APIIs 12.8mL, FL_HTHP23.5mL, i.e., the funnel viscosities of examples 1b and 3b are lower than the funnel viscosity of comparative example 1, because the fluid loss additive in fluid loss additive II is released, and the material can effectively reduce viscosity, further reduce the performance change of the drilling fluid caused by temperature rise, and meanwhile, the fluid loss amount and the high-temperature and high-pressure fluid loss amount of examples 1b and 3b are lower than the corresponding fluid loss amount and high-temperature and high-pressure fluid loss amount of comparative example 1, because the fluid loss additive in fluid loss additive II is reducedThe supplementary release of the fluid loss treatment machine and the arrangement of the materials with multiple particle sizes in a progressive way lead to low fluid loss;

AV equal to 23.8 mPas, FL for example 1b after 200 ℃/16h ageing_APIIs 7.8mL, FL_HTHP19.1 mL; AV of (b) is equal to 21.9 mPas, FL_APIIs 7.6mL, FL_HTHP18.4mL, while the AV of comparative example 1 is equal to 29.6 mPas, FL_APIIs 14.5mL, FL_HTHP25.7mL, first, the funnel viscosity of examples 1b, 3b was lower than that of comparative example 1 due to the complex replenishment release of fluid loss treatment agent from fluid loss additive ii, fluid loss additive iii; next, the fluid loss and the high temperature and high pressure fluid loss of examples 1b and 3b were lower than those of comparative example 1, because of the supplementary release of the fluid loss reducing treatment machine in fluid loss reducing agent ii and the progressive arrangement of the multi-particle size material, resulting in low fluid loss. While embodiments of the invention have been described above, it is not limited to the applications set forth in the description and the embodiments, which are fully applicable to various fields of endeavor for which the invention may be embodied with additional modifications as would be readily apparent to those skilled in the art, and the invention is therefore not limited to the details given herein and to the embodiments shown and described without departing from the generic concept as defined by the claims and their equivalents.