Modified calcium carbonate, method for preparing the same, and lost circulation material containing the same

Abstract

The application provides modified calcium carbonate, a preparation method thereof and a plugging agent containing the same. The modified calcium carbonate is a dicalcium bis-palmitoyl tartrate hydrophobic modified calcium carbonate. The plugging agent comprises the modified calcium carbonate, natural asphalt, high filtration material, degradable fiber and oil.

Description

Technical Field

[0001] This invention relates to the field of oil and gas well plugging, and particularly to a hydrophobic modified calcium carbonate for plugging. Background Technology

[0002] With the large-scale exploration and development of unconventional oil and gas resources, the application of oil-based drilling fluids is becoming increasingly widespread. Oil-based drilling fluids possess advantages such as strong inhibition, good lubrication, high-temperature resistance, strong anti-pollution ability, and good reservoir protection performance, making them the preferred choice for drilling challenging wells. They are particularly significant for shale gas development, wells with special processes, and exploration and development of oil and gas resources in complex formations prone to collapse and water sensitivity. Research suggests that oil-based drilling fluids have fundamentally solved the hydration problem of shale and mudstone; however, complex situations such as blockage and wellbore instability still occur during application. Analysis indicates that the main reason is the insufficient plugging capacity of oil-based drilling fluids, which cannot effectively control the pressure transmission in shale and mudstone. Therefore, there is an urgent need to develop an oil-based drilling fluid with enhanced plugging performance. Summary of the Invention

[0003] One aspect of the present invention provides a modified calcium carbonate, wherein the modified calcium carbonate is a hydrophobic modified calcium carbonate in which bispalmitoyl tartrate diester is bonded to the surface of calcium carbonate particles, and the particle size of the modified calcium carbonate is 1200 mesh to 1500 mesh.

[0004] In one specific embodiment, the mass ratio of the dipalmitoyl tartrate diester to the calcium carbonate particles is 1:(45-55).

[0005] The second aspect of the present invention provides a method for preparing modified calcium carbonate according to the first aspect of the present invention, which includes the following steps:

[0006] 1) Calcium carbonate is dispersed in a dispersant to obtain a dispersion;

[0007] 2) Heat the dispersion, then add bispalmitoyl tartrate diester, and stir until the modification reaction is complete to obtain the modified material;

[0008] 3) The modified material is filtered, washed, dried and pulverized to obtain the modified calcium carbonate.

[0009] In one specific embodiment, the dispersant is anhydrous ethanol.

[0010] In one specific embodiment, in step 2), the temperature is heated to 55°C to 65°C.

[0011] In one specific embodiment, in step 2), the modification reaction time is 45 min to 55 min.

[0012] In one specific embodiment, in step 3), the filter cake obtained after filtration of the modified material is washed with ethanol 3 to 5 times and then vacuum dried at 70°C to 85°C.

[0013] The third invention provides a sealing agent comprising modified calcium carbonate prepared by the method described in the first invention or any one of the second invention, natural asphalt, high filtration loss material, biodegradable fiber, and oil.

[0014] In one specific embodiment, the modified calcium carbonate content is 20% to 40% of the total mass of the sealing agent, the natural bitumen content is 15% to 20%, the high filtration loss material content is 10% to 15%, the biodegradable fiber content is 5% to 10%, and the balance is oil.

[0015] In one specific embodiment, the softening point temperature of the natural asphalt is ≤ the lost formation temperature +10℃ and ≥ the lost formation temperature -10℃.

[0016] In one specific embodiment, the particle size of the natural bitumen is 0.1 mm to 0.2 mm.

[0017] In one specific embodiment, the high filtration loss material is a high filtration loss plugging agent.

[0018] In one specific embodiment, the biodegradable fiber is any one of cellulose fiber, chitin fiber, and polylactic acid fiber.

[0019] In one specific embodiment, the biodegradable fiber has a fiber length of 1 mm to 2 mm and a fiber diameter of 0.2 mm to 0.6 mm.

[0020] In one specific embodiment, the oil is white oil and / or mineral oil.

[0021] The fourth invention provides the application of modified calcium carbonate as described in the first invention, modified calcium carbonate prepared by the method described in any one of the second invention, or the plugging agent described in any one of the third invention in plugging leaks in oil-based drilling fluids.

[0022] The beneficial effects of this invention are:

[0023] The modified calcium carbonate of the present invention has a lower oil absorption value, a lower sedimentation volume, and a higher activation degree, and does not increase viscosity. This greatly reduces the agglomeration of modified calcium carbonate particles, thereby ensuring the dispersibility and dispersion stability of modified calcium carbonate.

[0024] The sealant prepared by combining the modified calcium carbonate of this invention with natural asphalt, high filtration loss sealing material and biodegradable fiber has a better sealing effect due to the synergistic effect of the components.

[0025] Furthermore, the plugging agent of this invention has good compatibility with oil-based drilling fluids, has little impact on the viscosity, shear stress, and demulsification voltage of the oil-based drilling fluid system, and has a certain effect on reducing filtration loss. It can withstand temperatures up to 150℃. Using the plugging agent of this invention, the permeability of 100μm and 125μm ceramic sheet mud cake can be reduced from 10... -4 ×10 -3 μm 2 Reduced to 10 -7 ×10 -3 μm 2 Meanwhile, the mud cake formed by the plugging agent has an acid solubility rate of >70%, and has hydrophobic and oleophilic properties, multi-stage sealing effect, acid solubility and backflow, and does not damage the formation. It meets the requirements of wellbore stability, safe and environmentally friendly production during oil-based drilling fluid construction. Detailed Implementation

[0026] The present invention will be further described below with reference to the embodiments. However, the embodiments of the present invention are merely illustrative examples and should not be construed as limiting the present invention under any circumstances.

[0027] Example 1

[0028] 20g of 800-1200 mesh calcium carbonate and 200mL of anhydrous ethanol as a dispersant were added to a 250mL three-necked flask and ultrasonically dispersed. The flask was then placed in a 60℃ constant-temperature water bath with a reflux condenser. 0.4g of bispalmitoyl tartrate diester as a modifier was slowly added to the flask, and the mixture was stirred at a constant speed of 800 rpm for 55 minutes. After the reaction was complete, the material was cooled to room temperature, filtered, and the filter cake was washed three times with anhydrous ethanol. The cake was then vacuum-dried at 70℃ for 4 hours, pulverized, and stored in a desiccator in a sealed container. The particle size of the pulverized particles was determined to be 1200-1500 mesh using a laser particle size analyzer.

[0029] Example 2

[0030] 25g of 800-1200 mesh calcium carbonate and 200mL of anhydrous ethanol as a dispersant were added to a 250mL three-necked flask and ultrasonically dispersed. The flask was then placed in a 65℃ constant temperature water bath with a reflux condenser. 0.56g of bispalmitoyl tartrate diester as a modifier was slowly added to the flask, and the mixture was stirred at a constant speed of 800 rpm for 50 minutes. After the reaction was complete, the material was cooled to room temperature, filtered, and the filter cake was washed five times with anhydrous ethanol. The cake was then vacuum dried at 85℃ for 4 hours, pulverized, and stored in a desiccator in a sealed container. The particle size of the pulverized particles was determined to be 1200-1500 mesh using a laser particle size analyzer.

[0031] Example 3

[0032] 30g of 800-1200 mesh calcium carbonate and 200mL of anhydrous ethanol as a dispersant were added to a 250mL three-necked flask and ultrasonically dispersed. The flask was then placed in a 55℃ constant temperature water bath with a reflux condenser. 0.55g of bispalmitoyl tartrate diester as a modifier was slowly added to the flask, and the mixture was stirred at a constant speed of 800 rpm for 45 minutes. After the reaction was complete, the material was cooled to room temperature, filtered, and the filter cake was washed four times with anhydrous ethanol. After vacuum drying at 70℃, the cake was pulverized for 5 hours and stored in a desiccator in a sealed container. The particle size of the pulverized particles was determined to be 1200-1500 mesh using a laser particle size analyzer.

[0033] Comparative Example 1

[0034] 25g of 800-1200 mesh calcium carbonate and 200mL of anhydrous ethanol as a dispersant were added to a 250mL three-necked flask and ultrasonically dispersed. The flask was then placed in an 85℃ constant temperature water bath with a reflux condenser. 0.5g of stearic acid as a modifier was slowly added to the flask, and the mixture was stirred at a constant speed of 600 rpm for 50 minutes. After the reaction was complete, the material was cooled to room temperature, filtered, and the filter cake was washed three times with anhydrous ethanol. The cake was then vacuum dried at 75℃ for 4 hours, pulverized, and stored in a desiccator in a sealed container. The particle size of the pulverized particles was determined to be 1200-1500 mesh using a laser particle size analyzer.

[0035] Comparative Example 2

[0036] 1200 mesh-1500 mesh calcium carbonate powder.

[0037] Preparation of sealing agent

[0038] HHH high filtration loss plugging agent was purchased from Chengdu Chuanfeng Chemical Co., Ltd.

[0039] Example 4

[0040] The natural asphalt used in this embodiment has a softening point of 145℃ and a particle size of 0.1mm-0.2mm; the cellulose fiber length is 1mm-1.5mm and the fiber diameter is 0.2mm-0.25mm.

[0041] 1) Mix 20g of natural asphalt, 30g of white oil and 20g of modified calcium carbonate prepared in Example 1, stir evenly to obtain the first mixture;

[0042] 2) Add 10g of HHH high filtration loss plugging agent to 70g of the first mixture, stir and mix evenly to obtain the second mixture;

[0043] 3) Add 10g of cellulose fiber and 10g of white oil to 80g of the second mixture, stir and mix evenly to obtain the oil-based drilling fluid plugging agent.

[0044] Example 5

[0045] The natural bitumen used in this embodiment has a softening point of 150℃ and a particle size of 0.1mm-0.2mm; the chitin fibers have a length of 1.5mm-2mm and a diameter of 0.25mm-0.3mm.

[0046] 1) Mix 19.5g of natural asphalt, 30g of mineral oil and 25g of modified calcium carbonate prepared in Example 1, stir evenly to obtain the first mixture;

[0047] 2) Add 10.5g of HHH high filtration loss plugging agent to 74.5g of the first mixture, stir and mix evenly to obtain the second mixture;

[0048] 3) Add 9g of chitin fiber and 6g of mineral oil to 85g of the second mixture, stir and mix evenly to obtain the oil-based drilling fluid plugging agent.

[0049] Example 6

[0050] In this embodiment, the natural asphalt used has a softening point of 147℃ and a particle size of 0.1mm-0.2mm; the polylactic acid fiber has a length of 1mm-2mm and a fiber diameter of 0.35mm-0.45mm.

[0051] 1) Mix 19g of natural asphalt, 25g of white oil and 30g of modified calcium carbonate prepared in Example 1, stir evenly to obtain the first mixture;

[0052] 2) Add 11g of HHH high filtration loss plugging agent to 74g of the first mixture, stir and mix evenly to obtain the second mixture;

[0053] 3) Add 8g of polylactic acid fiber and 7g of white oil to 85g of the second mixture, stir and mix evenly to obtain the oil-based drilling fluid plugging agent.

[0054] Example 7

[0055] The natural asphalt used in this embodiment has a softening point of 142℃ and a particle size of 0.1mm-0.2mm; the polylactic acid fiber has a length of 1mm-2.5mm and a fiber diameter of 0.4mm-0.5mm.

[0056] 1) Mix 16.5g of natural asphalt, 25g of mineral oil and 30g of modified calcium carbonate prepared in Example 2, stir evenly to obtain the first mixture;

[0057] 2) Add 13.5g of HHH high filtration loss plugging agent to 71.5g of the first mixture, stir and mix evenly to obtain the second mixture;

[0058] 3) Add 7.5g of polylactic acid fiber and 7.5g of mineral oil to 85g of the second mixture, stir and mix evenly to obtain the oil-based drilling fluid plugging agent.

[0059] Example 8

[0060] The natural asphalt used in this embodiment has a softening point of 144℃ and a particle size of 0.1mm-0.2mm; the cellulose fiber length is 2mm-2.5mm and the fiber diameter is 0.5mm-0.6mm.

[0061] 1) Mix 16g of natural asphalt, 20g of white oil and 35g of modified calcium carbonate prepared in Example 3, stir evenly to obtain the first mixture;

[0062] 2) Add 14g of HHH high filtration loss plugging agent to 71g of the first mixture, stir and mix evenly to obtain the second mixture;

[0063] 3) Add 8.5g of cellulose fiber and 6.5g of white oil to 85g of the second mixture, stir and mix evenly to obtain the oil-based drilling fluid plugging agent.

[0064] Example 9

[0065] The natural bitumen used in this embodiment has a softening point of 152℃ and a particle size of 0.1mm-0.2mm; the chitin fibers have a length of 1.5mm-2.5mm and a diameter of 0.55mm-0.6mm.

[0066] 1) Mix 15g of natural asphalt, 15g of white oil and 40g of modified calcium carbonate prepared in Example 1, stir evenly to obtain the first mixture;

[0067] 2) Add 15g of HHH high filtration loss plugging agent to 70g of the first mixture, stir and mix evenly to obtain the second mixture;

[0068] 3) Add 9.5g of chitin fiber and 5.5g of white oil to 85g of the second mixture, stir and mix evenly to obtain the oil-based drilling fluid plugging agent.

[0069] Example 10

[0070] In this embodiment, the natural asphalt used has a softening point of 155℃ and a particle size of 0.1mm-0.2mm; the polylactic acid fiber has a length of 1mm-1.5mm and a fiber diameter of 0.2mm-0.25mm.

[0071] 1) Mix 25g of natural asphalt, 10g of mineral oil and 10g of modified calcium carbonate prepared in Example 1, stir evenly to obtain the first mixture;

[0072] 2) Add 30g of HHH high filtration loss plugging agent to 45g of the first mixture, stir and mix evenly to obtain the second mixture;

[0073] 3) Add 20g of polylactic acid fiber and 5g of mineral oil to 75g of the second mixture, stir and mix evenly to obtain the oil-based drilling fluid plugging agent.

[0074] Example 11

[0075] The natural asphalt used in this embodiment has a softening point of 148℃ and a particle size of 0.1mm-0.2mm; the cellulose fiber length is 1mm-2mm and the fiber diameter is 0.35mm-0.45mm.

[0076] 1) Mix 10g of natural asphalt, 10g of white oil and 50g of modified calcium carbonate prepared in Example 1, stir evenly to obtain the first mixture;

[0077] 2) Add 5g of HHH high filtration loss plugging agent to 70g of the first mixture, stir and mix evenly to obtain the second mixture;

[0078] 3) Add 15g of cellulose fiber and 10g of white oil to 75g of the second mixture, stir and mix evenly to obtain the oil-based drilling fluid plugging agent.

[0079] Comparative Example 3

[0080] The natural bitumen used in this comparative example has a softening point of 154℃ and a particle size of 0.1mm-0.2mm.

[0081] 20g of natural asphalt, 40g of mineral oil and 40g of modified calcium carbonate prepared in Example 1 were mixed and stirred evenly to obtain the oil-based drilling fluid plugging agent.

[0082] Comparative Example 4

[0083] The polylactic acid fibers used in this comparative example have a length range of 2mm-2.5mm and a fiber diameter range of 0.4mm-0.5mm.

[0084] 1) Mix 15g of HHH high filtration loss plugging agent, 20g of white oil and 35g of modified calcium carbonate prepared in Example 1, stir evenly to obtain the first mixture;

[0085] 2) Add 10g of polylactic acid fiber and 20g of white oil to 70g of the first mixture, stir and mix evenly to obtain the oil-based drilling fluid plugging agent.

[0086] Performance Analysis

[0087] 1. Performance Analysis of Modified Calcium Carbonate

[0088] The hydrophobic properties of the diepalmitoyl tartrate-modified calcium carbonate, the stearic acid-modified calcium carbonate of Comparative Example 1, and the unmodified calcium carbonate of Comparative Example 2 were analyzed according to the national standard GB / T 19281-2003 "Analytical Methods for Calcium Carbonate". The results are shown in Table 1. According to the results in Table 1, the diepalmitoyl tartrate-modified calcium carbonate has lower oil absorption value, higher activation degree, and better hydrophobicity.

[0089] Table 1 Comparison of properties of calcium carbonate before and after modification

[0090] Modifier <![CDATA[Oil absorption value / mL·g -1 > <![CDATA[Settling volume / mL·g -1 > Activation degree / % none 0.2780 1.3 0.00 stearic acid 0.2426 0.8 86.82 Dipalmitoyl tartrate 0.1839 0.3 98.58

[0091] 2. Performance analysis of the plugging agent

[0092] 5# white oil, main emulsion R-hw, auxiliary emulsion F-hw, organic clay RZ, filtration loss reducer J-hw, and wetting agent RS-hw were all purchased from Chengdu Xiyou Huawai Technology Co., Ltd.; the average particle size was 320μm and the density was 4.3g / cm³. 3 The barite was purchased from Sichuan Renzhi Oil Service Co., Ltd.

[0093] Preparation of oil-based drilling fluid base fluid:

[0094] 1) Mix 400 mL of No. 5 white oil with 100 mL of 25 wt% CaCl2 aqueous solution to obtain 500 mL of mixed solution;

[0095] 2) Taking 500 mL of the mixture as 100%, add 0.6% primary emulsion R-hw, 1.8% secondary emulsion F-hw, 2% organic clay RZ, 4% filtration loss reducer J-hw, 2% wetting agent RS-hw, 2% CaO, and 383.31 g of barite, and mix thoroughly to obtain a density of 1.5 g / cm³. 3 Oil-based drilling fluid.

[0096] 100g of the plugging agent prepared in Examples 4 to 11 and Comparative Examples 3 to 4 was added to 520mL of oil-based drilling fluid to obtain oil-based drilling fluid.

[0097] 2.1 Compatibility analysis of plugging agent and oil-based drilling fluid

[0098] After aging the oil-based drilling fluid at 150℃ for 16 hours, the effect of the plugging agent on the performance of the oil-based drilling fluid was determined according to Part 1 of GB / T 16783.1-2014 Field Testing of Drilling Fluids for Petroleum and Natural Gas Industry, Water-based Drilling Fluids. The results are shown in Table 2.

[0099] Table 2 Compatibility Evaluation of Positive Plugging Agent and Drilling Fluid

[0100]

[0101] According to the results in Table 2, the plugging agents of Examples 3 to 8 of the present invention have little effect on the viscosity, dynamic shear force, and demulsification voltage of the oil-based drilling fluid system, indicating good compatibility and a certain effect on reducing filtration loss. The temperature resistance can reach 150℃. In contrast, the plugging agents of the comparative examples have little effect on the performance of the oil-based drilling fluid.

[0102] 2.2 Evaluation of Blocking Effectiveness

[0103] Ceramic plate modules with different pore sizes from 10μm to 125μm, as shown in Tables 3 and 4, were used to simulate formation cores, and the sealing effect was evaluated using a Type 71 high-temperature and high-pressure water loss meter.

[0104] (1) The oil-based drilling fluid was aged by rolling at 150℃ for 16 hours. After aging, the oil-based drilling fluid was subjected to filtration loss measurement for 30 minutes under different pore size ceramic plate modules at 150℃ and 3.5MPa experimental conditions using a Type 71 high-temperature and high-pressure fluid loss meter. The upper oil-based drilling fluid was poured out, leaving the bottom ceramic plate module and mud cake. 700mL of No. 5 white oil was added again, and the filtration loss was measured for 30 minutes under the experimental conditions of 150℃ and 3.5MPa. The permeability of the mud cake formed under the oil-based drilling fluid conditions was calculated according to Darcy's law. The results are shown in Table 3.

[0105] (2) The oil-based drilling fluid was aged by rolling at 150℃ for 16 hours; after aging, the oil-based drilling fluid was subjected to filtration loss measurement for 30 minutes under different pore size ceramic disc modules at 150℃ and 3.5MPa experimental conditions using a Type 71 high-temperature and high-pressure fluid loss meter; the upper oil-based drilling fluid was poured out, leaving the bottom ceramic discs and mud cake, and 700mL of No. 5 white oil was added again, and the filtration loss was measured for 30 minutes under 150℃ and 3.5MPa experimental conditions; according to Darcy's law, the permeability of the mud cake formed under the oil-based drilling fluid conditions was calculated (filtration loss area 22.9cm). 2 The results are shown in Table 4.

[0106] Table 3. Determination of the plugging effect of oil-based drilling fluids.

[0107]

[0108] Table 4. Determination of the plugging effect of oil-based drilling fluids

[0109]

[0110]

[0111] Tables 3 and 4 show the plugging evaluation results, indicating that the permeability of the mud cake formed by the oil-based drilling fluid is (10). -5 ~10 -4 )×10 -3 μm 2 The oil-based drilling fluids with added plugging agents from Examples 3 to 8 showed a significant reduction in the permeability of ceramic disc mud cakes of different sizes. Specifically, the permeability of 100μm and 125μm ceramic disc mud cakes decreased from 10... -4 ×10 -3 μm 2 Reduced to 10 -7 ×10 -3 μm 2 The sealing effect is good; when the oil-based drilling fluid containing the plugging agents of Examples 10 and 11 and Comparative Examples 3 and 4 is added, the mud cake permeability does not change much before and after, and the sealing effect is not ideal, which fully demonstrates that the plugging agent of the present invention has significant plugging advantages.

[0112] 2.3 Unclogging and backflow characteristics of the sealing agent

[0113] To investigate the plugging and backflow characteristics of the plugging agent, the acid solubility rate of the mud cake formed after the plugging agents of Examples 4 to 11 and Comparative Examples 3 to 4 were added to the oil-based drilling fluid base fluid was measured.

[0114] According to SY / T 5358-2002 "Evaluation Method of Reservoir Sensitivity Flow Test":

[0115] 1) Use a medium-pressure filter remover to process oil-based drilling fluid and oil-based drilling fluid for 30 minutes to obtain their respective mud cakes. Dry the mud cakes at 105℃ for 4 hours and place them in a desiccator for later use.

[0116] 2) Weigh 10g of the dried mud cake from step 1), record it as the initial mud cake mass, place it in an Erlenmeyer flask, then add 150mL of 15wt% HCl, react and dissolve in a constant temperature water bath at 90℃ for 2h to obtain a dissolved mixture;

[0117] 3) Filter the dissolved mixture to obtain filter residue, dry the filter residue, weigh it, and record the weight as the mass of the remaining undissolved mud cake;

[0118] 4) Calculate the acid solubility rate of the mud cake based on the formula. Acid solubility rate of mud cake = (initial mud cake mass - remaining undissolved mud cake mass) / initial mud cake mass * 100.

[0119] The results are shown in Table 5. As can be seen from Table 5, the acid solubility rate of the plugging agent used in Examples 4 to 9 of this invention is all >70%, indicating a good acid dissolution and plugging effect.

[0120] Table 5 Acid solubility of mud cake

[0121]

[0122]

[0123] In summary, the plugging agent of this invention has good compatibility with oil-based drilling fluids, has little impact on the viscosity, shear stress, and demulsification voltage of the oil-based drilling fluid system, and also has a certain effect on reducing filtration loss. It can withstand temperatures up to 150℃. Using the plugging agent of this invention, the permeability of 100μm and 125μm ceramic sheet mud cake is reduced from 10... -4 ×10 -3 μm 2 Reduced to 10 -7 ×10 -3 μm 2 Meanwhile, the mud cake formed by the plugging agent has an acid solubility rate of >70%, and has the characteristics of multi-stage sealing effect, hydrophobic and oleophilic properties, acid solubility and backflow, and no damage to the formation.

[0124] While the present invention has been described with reference to specific embodiments, those skilled in the art will understand that various changes can be made without departing from the true spirit and scope of the invention. Furthermore, numerous modifications can be made to the subject, spirit, and scope of the invention to suit specific situations, materials, material compositions, and methods. All such modifications are included within the scope of the claims of the present invention.

Claims

1. A lost circulation material, comprising modified calcium carbonate, natural asphalt, HHH high fluid loss lost circulation material, degradable fiber and oil; wherein the modified calcium carbonate is hydrophobic modified calcium carbonate with a di-palmitoyl tartaric acid diester bonded on the surface of calcium carbonate particles, and the particle size of the modified calcium carbonate is 1200 mesh to 1500 mesh; the content of the modified calcium carbonate is 20% to 40%, the content of the natural asphalt is 15% to 20%, the content of the HHH high fluid loss lost circulation material is 10% to 15%, the content of the degradable fiber is 5% to 10%, and the balance is oil, based on 100% of the total mass of the lost circulation material.

2. The lost circulation material of claim 1, wherein, the mass ratio of the di-palmitoyl tartaric acid diester to the calcium carbonate particles is 1: (45-55).

3. The lost circulation material of claim 1 or 2, wherein, the modified calcium carbonate is prepared according to the following steps: 1) dispersing calcium carbonate in a dispersant to obtain a dispersion liquid; 2) heating the dispersion liquid, then adding di-palmitoyl tartaric acid diester, stirring until the modification reaction is complete, to obtain a modified material; 3) performing suction filtration, washing, drying and crushing on the modified material to obtain the modified calcium carbonate.

4. The lost circulation material of claim 3, wherein, the dispersant is anhydrous ethanol.

5. The lost circulation material of claim 3, wherein, in step 2), heating to 55°C to 65°C;and / or in step 2), the time for the modification reaction is 45 min to 55 min.

6. The lost circulation material of claim 3, wherein, in step 3), the filter cake obtained after suction filtration of the modified material is washed with ethanol for 3 to 5 times and vacuum dried at 70°C to 85°C.

7. The lost circulation material of claim 1, wherein, the softening point temperature of the natural asphalt is ≤ the lost circulation formation temperature + 10°C and ≥ the lost circulation formation temperature - 10°C.

8. The lost circulation material of claim 1, wherein, the particle size of the natural asphalt is 0.1 mm to 0.2 mm; the degradable fiber is any one of cellulose fiber, chitin fiber and polylactic acid fiber; the fiber length of the degradable fiber is 1 mm to 2 mm, and the fiber diameter is 0.2 mm to 0.6 mm; the oil is white oil and / or mineral oil.

9. Use of the lost circulation material according to any one of claims 1 to 8 in lost circulation plugging for oil-based drilling fluid.

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