High-efficiency lubricant for nano molybdenum compound drilling fluid, continental facies shale long horizontal well water-based drilling fluid system, preparation method of continental facies shale long horizontal well water-based drilling fluid system and preparation method and application of drilling fluid

Abstract

A continental facies shale long horizontal well water-based drilling fluid system comprises the following raw materials by weight: 1-2 parts of xanthan gum; 4-6 parts of a temperature-resistant and salt-resistant zwitterionic filtrate reducer; 60-80 parts of potassium chloride; 10-20 parts of a sulfomethylated phenolic resin dry agent for the drilling fluid; 10-20 parts of a sulfonated lignite dry agent for drilling fluid; 20-35 parts of a film-forming filtrate reducer for the drilling fluid; 20-35 parts of a rigid plugging agent while drilling; 15-25 parts of a low-fluorescence anti-collapse blocking agent for the drilling fluid; 30 to 50 parts of montmorillonite; 1000 parts of tap water; 1.5 to 2.5 parts of sodium carbonate; 15-25 parts of a flow pattern regulator for drilling fluid; and 3-7 parts of a high-efficiency lubricant for a nano molybdenum compound drilling fluid. The invention further discloses a preparation method of the efficient lubricant for the nano molybdenum compound drilling fluid, a preparation method of a continental facies shale long horizontal well water-based drilling fluid system and a preparation method and application of the drilling fluid. The high-efficiency lubricant for the nano-molybdenum compound drilling fluid, which is researched and developed by the invention, generates MoS2 which is gradually deposited on the surface in the friction process of a drill column to form a MoS2 deposition coating film, so that the friction reduction and wear resistance are improved.

Description

Technical Field

[0001] The present invention relates to the technical field of oil and gas field exploration and development drilling, and in particular to a high-efficiency lubricant for nano-molybdenum compound drilling fluid, a water-based drilling fluid system for continental shale long horizontal wells, a preparation method thereof, and a drilling fluid preparation method and application thereof. Background Art

[0002] With the continuous growth of global energy demand and the rise of shale gas development, the importance of drilling technology, especially drilling fluid technology, in shale oil and gas development has become increasingly prominent. Although traditional oil-based drilling fluids are effective in preventing wellbore collapse, their high cost and environmental pollution limit their large-scale application. At the same time, in the practice of efficient development of shale reservoir oil and gas, long horizontal wells have development advantages that vertical wells cannot match. However, due to the long horizontal section, complex and diverse lithology encountered, and long contact time between drilling fluid and drilling tools and the formation, there are many technical difficulties in the drilling process.

[0003] Since 2011, during the exploration of shale oil resources in the Chang 7 formation of the Yanchang Group in the southwestern part of the Ordos Basin, a large number of wells have found rich oil and gas indicators in black organic shales, and the low oil flow obtained by fracturing in a few wells proves the existence of shale oil resources in organic shales. The 15 horizontal wells initially drilled had certain technical problems using local water-based drilling fluids. Multiple complex problems such as well leakage, well collapse, and stuck drills coexist in the same wellbore or even the same open hole section. The proportion of complex problem wells exceeds 63% (43% of wells completed in advance). The poor applicability and stability of conventional drilling fluids have increased the difficulty of drilling and completion, and seriously affected the construction of high-quality shale oil wellbores. Therefore, the development of a water-based drilling fluid suitable for long horizontal wells in continental shale has become an urgent problem to be solved.

[0004] The main technical difficulties in drilling fluid for long horizontal wells in continental shale are: wellbore stability, lubrication and anti-sticking, wellbore purification and reaming difficulties, well leakage, and reservoir protection.

[0005] Patent CN107652952A discloses a high-performance water-based drilling fluid suitable for long horizontal sections of shale gas, which is uniformly mixed with water, bentonite, caustic soda, multifunctional composite agent, medium molecular weight fluid loss reducer, high-efficiency coating agent, anti-collapse lubricant, plugging and filtration reducer, inhibitor, nano plugging agent and speed-increasing lubricant. This invention is aimed at the marine shale gas formation in Fuling area. The sedimentary environment of marine and continental shale formations is different, and the rock types and bedding fracture development are significantly different. This patent cannot meet the requirements of long horizontal well drilling of continental shale.

[0006] Patent CN103937470A discloses a water-based drilling fluid suitable for horizontal mud shale, which is composed of water, bentonite for drilling fluid, sodium carbonate, viscosity enhancer, shale inhibitor, fluid loss reducer, small molecule coating agent, asphalt plugging and anti-collapse agent, aluminum-based polymer, rigid plugging and anti-collapse agent, lubricant, emulsifier, and weighting agent. The patent's inhibitory test uses horizontal mud shale in the Bonan Oilfield block, which is also aimed at marine shale formations, and cannot guarantee the stability of continental shale well walls. Summary of the invention

[0007] Aiming at the continental shale formation, a set of water-based drilling fluids for long horizontal wells has been developed to meet the needs of safe drilling fluids in long horizontal sections, effectively reduce drill string friction, and achieve the effect of oil-based drilling fluids.

[0008] A method for preparing a nano-molybdenum compound high-efficiency lubricant for drilling fluid comprises the following steps: (1) Place hexadecyltrimethylammonium bromide and bentonite in distilled water, stir thoroughly, and then add soda ash while stirring to obtain solution A; (2) placing sodium molybdate and acylthiourea into solution A obtained in step (1), stirring to make it uniform, to obtain solution B; (3) The solution B obtained in step (2) is transferred to an autoclave, kept at 240° C. for 24 h, cooled to room temperature, centrifuged, washed, and dried to obtain a nano-molybdenum compound high-efficiency lubricant for drilling fluid.

[0009] Preferably, the mass ratio of hexadecyltrimethylammonium bromide, bentonite, sodium molybdate and acylthiourea is 0.35:1.0:1.21:1.90; the temperature for sufficient stirring in step (1) is 80°C and the time is 10 minutes; and the amount of soda ash added is 5% of the mass of bentonite.

[0010] A water-based drilling fluid system for long horizontal wells in continental shale comprises the following raw materials in parts by weight: 1-2 parts of xanthan gum; 4-6 parts of temperature-resistant and salt-resistant zwitterionic fluid loss reducer; 60-80 parts of potassium chloride; 10-20 parts of sulfonated phenolic resin drying agent for drilling fluid; 10-20 parts of sulfonated lignite drying agent for drilling fluid; 20-35 parts of film-forming fluid loss reducer for drilling fluid; 20-35 parts of rigid while-drilling plugging agent; 15-25 parts of low-fluorescence anti-collapse plugging agent for drilling fluid; 30-50 parts of montmorillonite; 1000 parts of tap water; 1.5-2.5 parts of sodium carbonate; 15-25 parts of flow pattern regulator for drilling fluid; and 3-7 parts of high-efficiency lubricant for nano-molybdenum compound drilling fluid.

[0011] Preferably, the drilling fluid flow regulator is silicon dioxide-coated iron oxide nanoparticles; the preparation method thereof is specifically as follows: (1) mixing iron oxide nanoparticles with an ethanol-reverse osmosis aqueous solution and performing ultrasonic treatment to obtain a mixture; (2) Adding ethyl orthosilicate to the mixture obtained in step (1), adjusting the pH to 11, stirring at room temperature to make it evenly dispersed, reacting for 12 hours, washing with reverse osmosis water, and washing with ethanol until the solution is neutral; drying at -45°C for 24 hours to obtain silica-coated iron oxide nanoparticles.

[0012] Preferably, the amount of ethyl orthosilicate added is 1.0-1.5% of the mass of the mixture.

[0013] Preferably, the volume ratio of the iron oxide nanoparticles to the ethanol-reverse osmosis aqueous solution is 10:1.

[0014] A method for preparing the water-based drilling fluid system for long horizontal wells in continental shale comprises the following steps: (1) Take tap water, heat it to 100°C, add montmorillonite under stirring at 500 r / min, stir for 30 min, add sodium carbonate, stir for 30 min, let it stand for prehydration for 24 h, and obtain solution A; (2) adding xanthan gum to the solution A obtained in step (1) under stirring at 2000 r / min, stirring for 20 min, then adding a temperature-resistant and salt-resistant zwitterionic fluid loss reducer, stirring for 20 min; finally, adding potassium chloride, sulfomethylphenolic resin dry agent for drilling fluid, sulfonated lignite dry agent for drilling fluid, film-forming fluid loss reducer for drilling fluid, rigid while-drilling plugging agent, and low-fluorescence anti-collapse plugging agent for drilling fluid in sequence; the potassium chloride, sulfomethylphenolic resin dry agent for drilling fluid, sulfonated lignite dry agent for drilling fluid, film-forming fluid loss reducer for drilling fluid, rigid while-drilling plugging agent, and low-fluorescence anti-collapse plugging agent for drilling fluid are added in batches, and each substance added needs to be stirred until it is completely dissolved before continuing to add the next substance; (3) Then, a drilling fluid flow regulator and a nano-molybdenum compound drilling fluid high-efficiency lubricant were added in sequence and stirred for 4 hours to obtain a drilling fluid system.

[0015] A water-based drilling fluid for a long horizontal well in continental shale is prepared by adding 0.0530-0.0630 mm barite powder to the prepared drilling fluid system and increasing the weight to 1.20 g / cm 3 ~1.25 g / cm 3 , stirred for 1 hour to obtain a water-based drilling fluid suitable for long horizontal wells in continental shale.

[0016] The invention discloses an application of a water-based drilling fluid for a long horizontal well of continental shale. The horizontal well drilling fluid is applied to a long horizontal well of continental shale.

[0017] Advantages of the present invention: (1) In terms of plugging and anti-collapse properties, physical plugging agents such as rigid while-drilling plugging agents and chemical plugging agents such as film-forming fluid loss reducers for drilling fluids are preferably compounded to achieve broad-spectrum plugging through "multi-component synergy" and improve overall plugging strength; (2) Lubricity: First, the nano-molybdenum compound drilling fluid high-efficiency lubricant developed during the friction process of the drill string generates MoS2 which is gradually deposited on the surface to form a MoS2 deposition coating, thereby improving the friction reduction and anti-wear performance; second, during the friction process, the deposited MoS2 undergoes an oxidation reaction under the action of friction heat to form an oxide film composed of MoO3, FeO and Fe2O3 on the surface of the drill string. The deposition coating and the oxide film work together to reduce the friction and wear during the friction process of the drill string; (3) In terms of rock carrying, the developed drilling fluid flow regulator exhibits pseudoplastic shear thinning effect at lower concentrations by adding silica-coated iron oxide nanoparticles, which helps the mud maintain a lower viscosity at high shear rates, prevents particle agglomeration, and improves drilling fluid stability. (4) This patented drilling fluid has a stronger ability to inhibit plugging, HTHP water loss ≤ 10.2 mL, linear expansion rate controlled within 8.5%, rolling recovery rate greater than 90%, and the comprehensive performance of the polyhuang drilling fluid system used in the field is improved by more than 20%; at the same time, the density of this patented drilling fluid is adjustable, the performance is stable, and the field preparation and maintenance are simple. In view of the complex conditions of the continental shale layer, it can well maintain the stability of the wellbore wall, and the dynamic plastic ratio is maintained above 0.4; the lubricity of the drilling fluid meets the oil-based standard, and the extreme pressure lubrication coefficient measured on site in the test well is <0.08, ensuring the smooth completion of the 1,800-meter horizontal section of the continental shale. Specific embodiments

[0018] The temperature-resistant and salt-resistant zwitterionic fluid loss reducer is: the temperature-resistant and salt-resistant zwitterionic fluid loss reducer produced by Sichuan Southwest Petroleum University Jinniu Petroleum Technology Co., Ltd., code-named CHL-1; the film-forming fluid loss reducer for drilling fluid is: the film-forming fluid loss reducer for drilling fluid produced by Shandong Juxin Chemical Co., Ltd., code-named CMJ-2; the rigid while-drilling plugging agent is: the rigid while-drilling plugging agent produced by Sichuan Southwest Petroleum University Jinniu Petroleum Technology Co., Ltd., code-named DZD-A; the low-fluorescence anti-collapse plugging agent for drilling fluid is: the low-fluorescence anti-collapse plugging agent for drilling fluid produced by Sichuan Southwest Petroleum University Jinniu Petroleum Technology Co., Ltd., code-named EP-Ⅱ.

[0019] Example 1 A method for preparing a nano-molybdenum compound high-efficiency lubricant for drilling fluid comprises the following steps: (1) Place 0.35 g of hexadecyltrimethylammonium bromide and 1 g of bentonite in distilled water, stir thoroughly at 80°C for 10 min, and then add soda ash (5% by weight of bentonite) while stirring to obtain solution A; (2) 1.21 g of sodium molybdate and 1.90 g of acylthiourea were placed in the solution A obtained in step (1), and stirred to make it uniform; solution B was obtained; (3) The solution B obtained in step (2) was transferred into a 100 mL polytetrafluoroethylene-lined autoclave, kept at 240° C. for 24 h, cooled to room temperature, centrifuged, washed, and dried to obtain a nano-molybdenum compound high-efficiency lubricant for drilling fluid.

[0020] Example 2 A water-based drilling fluid system for long horizontal wells in continental shale comprises the following raw materials in parts by weight: 1 part of xanthan gum; 4 parts of temperature-resistant and salt-resistant zwitterionic fluid loss reducer; 65 parts of potassium chloride; 10 parts of sulfonated methylphenolic resin dry agent for drilling fluid; 10 parts of sulfonated lignite dry agent for drilling fluid; 25 parts of film-forming fluid loss reducer for drilling fluid; 20 parts of rigid while-drilling plugging agent; 15 parts of low-fluorescence anti-collapse plugging agent for drilling fluid; 30 parts of montmorillonite; 1000 parts of tap water; 1.5 parts of sodium carbonate; 15 parts of flow pattern regulator for drilling fluid; and 5 parts of nano-molybdenum compound high-efficiency lubricant for drilling fluid; The nano-molybdenum compound drilling fluid high-efficiency lubricant is prepared by the preparation method of Example 1; The drilling fluid flow pattern regulator is silicon dioxide-coated iron oxide nanoparticles, and the preparation method thereof is as follows: (1) mixing the iron oxide nanoparticles with the ethanol-reverse osmosis aqueous solution at a volume ratio of the iron oxide nanoparticles to the ethanol-reverse osmosis aqueous solution of 10:1, and ultrasonically treating the mixture to obtain a mixture; (2) Adding tetraethyl orthosilicate to the mixture obtained in step (1), wherein the amount of tetraethyl orthosilicate added accounts for 1.5% of the mass of the mixture, adjusting the pH to 11, stirring at room temperature to make it evenly dispersed, reacting for 12 hours, washing with reverse osmosis water, and washing with ethanol until the solution is neutral; and drying at -45°C for 24 hours to obtain silica-coated iron oxide nanoparticles.

[0021] A method for preparing a water-based drilling fluid system for a long horizontal well in continental shale comprises the following steps: (1) Take tap water, raise the temperature to 100°C, add montmorillonite under stirring at 500 r / min, and stir for 30 min. Add sodium carbonate, stir for 30 min, and let stand for prehydration for 24 h to obtain solution A; (2) adding xanthan gum to the solution A obtained in step (1) under stirring at 2000 r / min, stirring for 20 min, then adding a temperature-resistant and salt-resistant zwitterionic fluid loss reducer, stirring for 20 min; finally, adding potassium chloride, sulfomethylphenolic resin dry agent for drilling fluid, sulfonated lignite dry agent for drilling fluid, film-forming fluid loss reducer for drilling fluid, rigid while-drilling plugging agent, and low-fluorescence anti-collapse plugging agent for drilling fluid in sequence; the potassium chloride, sulfomethylphenolic resin dry agent for drilling fluid, sulfonated lignite dry agent for drilling fluid, film-forming fluid loss reducer for drilling fluid, rigid while-drilling plugging agent, and low-fluorescence anti-collapse plugging agent for drilling fluid are added in batches, and each substance added needs to be stirred until it is completely dissolved before continuing to add the next substance; (3) Then, a drilling fluid flow regulator and a nano-molybdenum compound drilling fluid high-efficiency lubricant were added in sequence and stirred for 4 hours to obtain a drilling fluid system.

[0022] A water-based drilling fluid for a long horizontal well in continental shale is prepared by adding 0.0530-0.0630 mm barite powder to the above-mentioned water-based drilling fluid system for a long horizontal well in continental shale, and increasing the weight of the system to 1.20 g / cm 3 , and stirred for 1 hour to obtain a water-based drilling fluid suitable for long horizontal wells in continental shale.

[0023] Example 3 A water-based drilling fluid system for long horizontal wells in continental shale comprises the following raw materials in parts by weight: 1 part of xanthan gum; 4 parts of temperature-resistant and salt-resistant zwitterionic fluid loss reducer; 60 parts of potassium chloride; 10 parts of sulfonated methylphenolic resin dry agent for drilling fluid; 10 parts of sulfonated lignite dry agent for drilling fluid; 20 parts of film-forming fluid loss reducer for drilling fluid; 35 parts of rigid while-drilling plugging agent; 15 parts of low-fluorescence anti-collapse plugging agent for drilling fluid; 30 parts of montmorillonite; 1000 parts of tap water; 2.5 parts of sodium carbonate; 15 parts of flow pattern regulator for drilling fluid; and 5 parts of nano-molybdenum compound high-efficiency lubricant for drilling fluid; The rest is the same as in Example 2.

[0024] A water-based drilling fluid for a long horizontal well in continental shale is prepared by adding 0.0530-0.0630 mm barite powder to the above-mentioned water-based drilling fluid system for a long horizontal well in continental shale, and increasing the weight of the system to 1.25 g / cm 3 , and stirred for 1 hour to obtain a water-based drilling fluid suitable for long horizontal wells in continental shale.

[0025] Example 4 A water-based drilling fluid system for long horizontal wells in continental shale comprises the following raw materials in parts by weight: 1.5 parts of xanthan gum; 5 parts of temperature-resistant and salt-resistant zwitterionic fluid loss reducer; 70 parts of potassium chloride; 20 parts of sulfonated methylphenolic resin dry agent for drilling fluid; 20 parts of sulfonated lignite dry agent for drilling fluid; 25 parts of film-forming fluid loss reducer for drilling fluid; 25 parts of rigid while-drilling plugging agent; 20 parts of low-fluorescence anti-collapse plugging agent for drilling fluid; 40 parts of montmorillonite; 1000 parts of tap water; 1.5 parts of sodium carbonate; 15 parts of flow pattern regulator for drilling fluid; and 3 parts of nano-molybdenum compound high-efficiency lubricant for drilling fluid; The rest is the same as in Example 2.

[0026] Example 5 A water-based drilling fluid system for long horizontal wells in continental shale comprises the following raw materials in parts by weight: 1 part of xanthan gum; 4 parts of temperature-resistant and salt-resistant zwitterionic fluid loss reducer; 65 parts of potassium chloride; 10 parts of sulfonated methylphenolic resin dry agent for drilling fluid; 10 parts of sulfonated lignite dry agent for drilling fluid; 25 parts of film-forming fluid loss reducer for drilling fluid; 20 parts of rigid while-drilling plugging agent; 15 parts of low-fluorescence anti-collapse plugging agent for drilling fluid; 30 parts of montmorillonite; 1000 parts of tap water; 1.5 parts of sodium carbonate; 25 parts of flow pattern regulator for drilling fluid; and 5 parts of nano-molybdenum compound high-efficiency lubricant for drilling fluid; The rest is the same as in Example 2.

[0027] Example 6 A water-based drilling fluid system for long horizontal wells in continental shale comprises the following raw materials in parts by weight: 2 parts of xanthan gum; 6 parts of temperature-resistant and salt-resistant zwitterionic fluid loss reducer; 80 parts of potassium chloride; 10 parts of sulfonated methylphenolic resin dry agent for drilling fluid; 10 parts of sulfonated lignite dry agent for drilling fluid; 35 parts of film-forming fluid loss reducer for drilling fluid; 30 parts of rigid while-drilling plugging agent; 25 parts of low-fluorescence anti-collapse plugging agent for drilling fluid; 50 parts of montmorillonite; 1000 parts of tap water; 1.5 parts of sodium carbonate; 15 parts of flow pattern regulator for drilling fluid; and 7 parts of nano-molybdenum compound high-efficiency lubricant for drilling fluid; The rest is the same as in Example 2.

[0028] Comparative Example 1 No drilling fluid flow pattern regulator was added, and the rest was the same as in Example 2.

[0029] Comparative Example 2 No nano-molybdenum compound is added to the high-efficiency lubricant for drilling fluid, and the rest is the same as in Example 2.

[0030] Comparative Example 3 No flow pattern regulator for drilling fluid and nano-molybdenum compound high-efficiency lubricant for drilling fluid are added, and the rest is the same as in Example 2.

[0031] Comparative Example 4 The drilling fluid of patent CN107652952A is used, and the rest is the same as in Example 2.

[0032] Comparative Example 5 The drilling fluid of patent CN103937470A is used, and the rest is the same as in Example 2.

[0033] Comparative Example 6 The drilling fluid flow pattern regulator was replaced with the flow pattern regulator commonly used on site, and the rest was the same as in Example 2.

[0034] The manufacturer of this flow pattern regulator is Shandong Deshunyuan Petroleum Technology Co., Ltd., code-named PANH.

[0035] Performance Testing Comprehensive evaluation method of drilling fluid performance 1. Field testing of drilling fluids in the petroleum and natural gas industry Part 1 Water-based drilling fluids GB / T16783.1-2014 (density, PV, YP, API water loss, HTHP water loss and other parameters shall be implemented in accordance with this standard); 2. Evaluation procedure for lubricants used in drilling fluids SY / T6094-1994 (mud cake viscosity coefficient and extreme pressure lubrication coefficient shall be implemented in accordance with this standard); 3. Evaluation method of shale inhibitors for drilling fluids SY / T6335-1997 (linear expansion rate and rolling recovery rate shall be implemented in accordance with this standard). Shale samples were taken from the core 7 of the Yanchang Formation in the Zhidan Oilfield of Shaanxi Province, a continental shale; 4. Indoor test method for bridging plugging materials for drilling fluid SY / T5840-2007 (the depth of the sand bed shall be in accordance with this standard); The conventional properties of the drilling fluids of the embodiments and comparative examples, such as rheological properties, inhibition, lubricity, water loss wall forming properties and sand bed plugging properties, were tested. The results are shown in Table 1.

[0036] Note: All data are measured at room temperature after hot rolling at 80℃ for 16 hours.

[0037] As can be seen from Table 1, the drilling fluid provided by the present invention has a dynamic-plastic ratio of >0.46 and good rheological properties; the system has high inhibition on shale, a linear expansion rate of <8.5%, a rolling recovery rate of >90%, and can effectively inhibit shale hydration; HTHP water loss ≤9.4mL, the mud cake is thin and dense, has high strength, and has good wall-building properties due to water loss; the viscosity coefficient of the drilling fluid mud cake is ≤0.072, the extreme pressure lubrication coefficient is <0.075, and the lubricity is good, reaching the standard of oil-based drilling fluid. It can be seen from various data that the drilling fluid flow type regulator can significantly improve the rheological properties of the drilling fluid, and compared with similar treatment agents on site, it has a significant effect on improving the lithology of long horizontal well drilling fluids; the high-efficiency lubricant for drilling fluid can significantly reduce friction and drag, and the lubricity of the drilling fluid is greatly improved. Overall, the drilling fluid has an adjustable density and stable performance, which can meet the requirements for safe drilling of long horizontal wells of continental shale, and its comprehensive performance is significantly improved compared with the control group.

[0038] Specific applications: The drilling fluid provided in Example 4 was applied in the LT32-P3 horizontal well in the Dingbian shale oil field. The effective reservoir of the well is the 7th section of the Triassic Yanchang Formation, and the reservoir permeability is 0.58-0.89 millidarcy, which belongs to the ultra-low permeability shale reservoir. Before entering the target reservoir, the ordinary polysulfone drilling fluid is converted into the drilling fluid described in Example 4. The horizontal section of the system is simple to handle and maintain, and the well wall stability, rock carrying property and lubricity are generally good. The performance parameters of the drilling fluid are shown in Table 2: Table 2 Drilling fluid properties of the construction well section of Example 4 .

[0039] As can be seen from Table 2, the drilling fluid provided by the present invention successfully completed the operations of drilling, logging, casing running, etc., and effectively solved the technical problems of well wall stability, rock carrying and lubrication in the whole process. The HTHP water loss was ≤10.2 mL, the dynamic plasticity ratio was >0.40, the rheological rock carrying property was kept good, the extreme pressure lubrication coefficient was <0.08, and the friction and drag were effectively reduced, which met the requirements for the safe drilling of the shale oil long horizontal well. Finally, the horizontal section of the well was 1850 m long, setting the record for the longest shale oil horizontal well in the area.

[0040] At present, the drilling fluid of the present invention has been applied in many continental shale oil areas such as Dingbian, Wuqi and Zhidan in the Ordos Basin, effectively solving the problems of poor applicability and stability of early drilling fluids. The potential for extension of long horizontal wells is prominent and the potential for promotion is huge.

Claims

1. A method for preparing a nano-molybdenum compound high-efficiency lubricant for drilling fluid, characterized in that: The following steps are involved: (1) Place hexadecyltrimethylammonium bromide and bentonite in distilled water, stir thoroughly, and then add soda ash while stirring to obtain solution A; (2) placing sodium molybdate and acylthiourea into solution A obtained in step (1), stirring to make it uniform, to obtain solution B; (3) The solution B obtained in step (2) is transferred to an autoclave, kept at 240° C. for 24 h, cooled to room temperature, centrifuged, washed, and dried to obtain a nano-molybdenum compound high-efficiency lubricant for drilling fluid.

2. The method for preparing the nano-molybdenum compound drilling fluid high-efficiency lubricant according to claim 1, characterized in that: The mass ratio of hexadecyltrimethylammonium bromide, bentonite, sodium molybdate and acylthiourea is 0.35:1.0:1.21:1.90; the temperature for full stirring in step (1) is 80°C and the time is 10 minutes; the amount of soda ash added is 5% of the mass of bentonite.

3. A water-based drilling fluid system for long horizontal wells in continental shale, characterized in that: The invention comprises the following raw materials in parts by weight: 1-2 parts of xanthan gum; 4-6 parts of temperature-resistant and salt-resistant zwitterionic fluid loss reducer; 60-80 parts of potassium chloride; 10-20 parts of sulfonated phenolic resin dry agent for drilling fluid; 10-20 parts of sulfonated lignite dry agent for drilling fluid; 20-35 parts of film-forming fluid loss reducer for drilling fluid; 20-35 parts of rigid while-drilling plugging agent; 15-25 parts of low-fluorescence anti-collapse plugging agent for drilling fluid; 30-50 parts of montmorillonite; 1000 parts of tap water; 1.5-2.5 parts of sodium carbonate; 15-25 parts of flow pattern regulator for drilling fluid; 3-7 parts of nano-molybdenum compound high-efficiency lubricant for drilling fluid; The nano-molybdenum compound drilling fluid high-efficiency lubricant is prepared by the preparation method of claim 1.

4. The water-based drilling fluid system for long horizontal wells in continental shale according to claim 3, characterized in that: The drilling fluid flow regulator is silicon dioxide-coated iron oxide nanoparticles; the preparation method thereof is specifically as follows: (1) mixing iron oxide nanoparticles with an ethanol-reverse osmosis aqueous solution and performing ultrasonic treatment to obtain a mixture; (2) Adding ethyl orthosilicate to the mixture obtained in step (1), adjusting the pH to 11, stirring at room temperature to make it evenly dispersed, reacting for 12 hours, washing with reverse osmosis water, and washing with ethanol until the solution is neutral; drying at -45°C for 24 hours to obtain silica-coated iron oxide nanoparticles.

5. The water-based drilling fluid system for long horizontal wells in continental shale according to claim 4, characterized in that: The amount of ethyl orthosilicate added is 1.0-1.5% of the mass of the mixture.

6. The water-based drilling fluid system for long horizontal wells in continental shale according to claim 4, characterized in that: The volume ratio of iron oxide nanoparticles to ethanol-reverse osmosis aqueous solution was 10:

1.

7. A method for preparing the water-based drilling fluid system for long horizontal wells in continental shale as claimed in claim 3, characterized in that: The following steps are involved: (1) Take tap water, heat it to 100°C, add montmorillonite under stirring at 500 r / min, stir for 30 min, add sodium carbonate, stir for 30 min, let it stand for prehydration for 24 h, and obtain solution A; (2) adding xanthan gum to the solution A obtained in step (1) under stirring at 2000 r / min, stirring for 20 min, then adding a temperature-resistant and salt-resistant zwitterionic fluid loss reducer, stirring for 20 min; finally, adding potassium chloride, sulfomethylphenolic resin dry agent for drilling fluid, sulfonated lignite dry agent for drilling fluid, film-forming fluid loss reducer for drilling fluid, rigid while-drilling plugging agent, and low-fluorescence anti-collapse plugging agent for drilling fluid in sequence; the potassium chloride, sulfomethylphenolic resin dry agent for drilling fluid, sulfonated lignite dry agent for drilling fluid, film-forming fluid loss reducer for drilling fluid, rigid while-drilling plugging agent, and low-fluorescence anti-collapse plugging agent for drilling fluid are added in batches, and each substance added needs to be stirred until it is completely dissolved before continuing to add the next substance; (3) Then, a drilling fluid flow regulator and a nano-molybdenum compound drilling fluid high-efficiency lubricant were added in sequence and stirred for 4 hours to obtain a drilling fluid system.

8. A water-based drilling fluid for long horizontal wells in continental shale, characterized in that: Add 0.0530-0.0630 mm barite powder to the drilling fluid system prepared in claim 7 and increase its weight to 1.20 g / cm 3 ~1.25 g / cm 3 , stirred for 1 hour to obtain a water-based drilling fluid suitable for long horizontal wells in continental shale.

9. An application of a water-based drilling fluid for long horizontal wells in continental shale, characterized in that: The horizontal well drilling fluid is applied to long horizontal wells in continental shale, and the horizontal well drilling fluid is the drilling fluid prepared according to claim 8.

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