A weighting agent and its preparation method

Abstract

This invention provides a weighting agent and its preparation method. The preparation method includes the following steps: hydroxylating iron ore powder to obtain hydroxylated iron ore powder; mixing and ball milling calcium carbonate powder and hydroxylated iron ore powder to obtain a mixture; baking and cooling the mixture to obtain the weighting agent; wherein the particle size of the iron ore powder is 12-18 μm, and the particle size of the calcium carbonate powder is 55-58 μm. The weighting agent includes the product prepared by the weighting agent preparation method described above. The weighting agent provided by this invention uses chemical bonding to combine calcium carbonate powder and iron ore powder into one, stably increasing the density of drilling fluid and making the density distribution of drilling fluid uniform, which is beneficial to the control of drilling fluid settling stability.

Description

Technical Field

[0001] This invention relates to the field of drilling fluid treatment agents, specifically to a weighting agent and its preparation method. Background Technology

[0002] During oil well production, adding weighting agents to drilling fluids not only increases the hydrostatic injection pressure of the drilling fluid, balances formation collapse stress, and stabilizes the wellbore, but also balances formation fluid pressure in high-pressure wells, thereby preventing well kicks, blowouts, and other malfunctions. Currently, the most commonly used acid-soluble weighting agent in drilling fluids is calcium carbonate, which has a density of 2.7 g / cm³. 3 Calcium carbonate is low in arsenic, a heavy metal. Adding calcium carbonate as a weighting agent to drilling fluid helps control formation pressure, prevent blowouts, well collapses, or well kicks, and adjusts the drilling fluid density for balanced pressure drilling. However, due to its low density, using calcium carbonate as a weighting agent results in a large dosage, easily leading to excessively high solid content in the drilling fluid, which hinders rapid drilling. Therefore, calcium carbonate is typically used in combination with other denser materials such as barite or iron ore powder as a weighting agent. However, simply combining calcium carbonate and iron ore powder as a weighting agent presents a problem: their densities differ, and uniform dispersion in the drilling fluid slurry cannot be guaranteed, making it difficult to control the settling stability of the drilling fluid. For example, if one part of the slurry has more calcium carbonate and less iron ore powder, while another part has less calcium carbonate and more iron ore powder, this can easily cause different densities in different parts of the drilling fluid slurry, resulting in pressure instability between the wellbore and the formation, and causing accidents such as wellbore collapse.

[0003] Chinese patent application number CN201310349412.1, entitled "A weighting agent for high-density drilling fluid, its preparation method, and a drilling fluid containing the weighting agent," discloses a weighting agent for high-density drilling fluid, its preparation method, and a drilling fluid containing the weighting agent. In this patent, the weighting material is selected from at least one of barite, modified barite, iron ore powder, activated iron ore powder, manganese ore powder, calcium carbonate, barium carbonate, or galena powder. Chinese patent application number CN201610881250.X, entitled "A low-damage particle size distribution weighted water-based drilling fluid," discloses a low-damage particle size distribution weighted water-based drilling fluid. In this patent, the weighting material includes vanadium-titanium iron ore powder, nano-barite, and nano-calcium carbonate. However, the raw materials and methods of this application are different from those of the present application. Through hydroxylation, a Ca-O-Fe chemical bond is formed between calcium carbonate and iron ore powder, thereby making the calcium carbonate and iron ore powder stably bonded, the drilling fluid settling more stably, and avoiding wellbore collapse accidents. Summary of the Invention

[0004] In view of the shortcomings of the prior art, the purpose of this invention is to solve one or more problems existing in the prior art. For example, one objective of this invention is to provide a weighting agent and its preparation method that can stably increase the density of drilling fluid and make its density distribution uniform.

[0005] To achieve the above objectives, the present invention provides a method for preparing a weighting agent, the method comprising the following steps: hydroxylating iron ore powder to obtain hydroxylated iron ore powder; mixing and ball milling calcium carbonate powder and hydroxylated iron ore powder to obtain a mixture of the two; baking and cooling the mixture to obtain a weighting agent; wherein the particle size of the iron ore powder may be 12-18 μm, and the particle size of the calcium carbonate powder may be 55-58 μm.

[0006] According to one or more exemplary embodiments of one aspect of the present invention, the hydroxylation treatment may include the steps of: mixing iron ore powder with ferric chloride solution and stirring to obtain a first intermediate; mixing tannic acid, potassium persulfate and the first intermediate to obtain a second intermediate; and post-processing the second intermediate to obtain hydroxylated iron ore powder.

[0007] According to one or more exemplary embodiments of one aspect of the present invention, the post-processing may include: heating and holding the second intermediate at a certain temperature; filtering, washing and drying to obtain hydroxylated iron ore powder.

[0008] According to one or more exemplary embodiments of one aspect of the present invention, the mass ratio of the iron ore powder, ferric chloride solution, tannic acid and potassium persulfide may be 1:(25-30):(0.5-0.8):(0.14-0.18).

[0009] According to one or more exemplary embodiments of one aspect of the present invention, the temperature of the heat preservation can be 50-60°C and the time can be 24-25h.

[0010] According to one or more exemplary embodiments of one aspect of the present invention, the mixing ball milling may be carried out by wet ball milling, the mixing ball milling time may be 100 to 110 minutes, the ball milling solvent may include water, and the ball milling medium may include iron balls.

[0011] According to one or more exemplary embodiments of one aspect of the present invention, the mass ratio of the calcium carbonate powder, hydroxylated iron ore powder, water and iron balls may be 1:(1.5-1.8):(2.5-2.8):(6-7).

[0012] According to one or more exemplary embodiments of one aspect of the present invention, the baking temperature may be 80-90°C and the baking time may be 160-180 min.

[0013] According to one or more exemplary embodiments of one aspect of the present invention, the mass fraction of the ferric chloride solution may be 20-25 wt%.

[0014] Another aspect of the present invention provides a weighting agent, which may include a product prepared by the weighting agent preparation method described above.

[0015] Compared with the prior art, the beneficial effects of the present invention may include at least one of the following:

[0016] (1) The weighting agent provided by the present invention can stably increase the density of drilling fluid and make the density of drilling fluid uniform, which is beneficial to the control of the settling stability of drilling fluid.

[0017] (2) The method for preparing the weighting agent provided by the present invention uses the method of forming stable chemical bonds to combine calcium carbonate powder and iron ore powder into one, and the resulting composite is firmly connected, effectively preventing the collapse of the well wall. Detailed Implementation

[0018] The present invention will now be described in detail with reference to tables and exemplary embodiments.

[0019] Exemplary Example 1

[0020] This exemplary embodiment provides a method for preparing a weighting agent, which mainly includes the following steps: hydroxylating iron ore powder to obtain hydroxylated iron ore powder; mixing and ball milling calcium carbonate powder and hydroxylated iron ore powder to obtain a mixture; and baking the mixture and cooling it to room temperature to obtain the weighting agent. The particle size of the iron ore powder can be 12–18 μm, for example, 13 μm, 15 μm, or 17 μm, and the particle size of the calcium carbonate powder can be 55–58 μm, for example, 56 μm or 57 μm. Here, the particle size of the iron ore powder is smaller than that of the calcium carbonate powder, allowing them to aggregate more tightly, resulting in a product with fewer pores after aggregation (hydrogen bonding).

[0021] In this embodiment, the hydroxylation treatment may include the following steps: mixing iron ore powder with a ferric chloride solution and stirring to obtain a first intermediate. Here, a magnetic stirrer can be used, and the stirring speed can be 500–800 r / min. Tannic acid, potassium persulfate, and the first intermediate are mixed to obtain a second intermediate. Here, tannic acid is a yellow or brownish-yellow powder, and its aqueous solution turns blue-black upon contact with an iron salt solution. The second intermediate is then post-processed to obtain hydroxylated iron ore powder.

[0022] In this embodiment, the post-processing may include: heating and holding the second intermediate at a certain temperature, then filtering, washing, and drying to obtain hydroxylated iron ore powder. Here, the second intermediate can be heated to 50–60°C and held at that temperature, for example, to 52°C, 55°C, 57°C, or 59°C, for a holding time of 24–25 hours, for example, 24.2 hours, 24.5 hours, 24.7 hours, or 24.9 hours. Next, the insoluble matter is filtered out, which can be washed with deionized water, and then dried to obtain hydroxylated iron ore powder. Here, an oven can be used for drying at a temperature of 80–90°C for a time of 160–180 minutes.

[0023] In this embodiment, the mass ratio of iron ore powder, ferric chloride solution, tannic acid, and potassium persulfide can be 1:(25-30):(0.5-0.8):(0.14-0.18), for example, 1:26:0.6:0.15, 1:28:0.7:0.16, or 1:28:0.7:0.17. Here, the mass fraction of the ferric chloride solution can be 20-25 wt%, for example, 21 wt%, 23 wt%, or 24 wt%. If the ferric chloride content is too low, the effective iron content cannot be guaranteed, resulting in insufficient hydroxyl groups on the surface of the treated iron ore powder, affecting the stable bonding between the iron ore powder and calcium carbonate. If the ferric chloride content is too high, it will result in waste, and the number of hydroxyl groups will not increase.

[0024] In this embodiment, the mixing ball milling can be performed using a wet ball milling method, and the mixing ball milling time can be 100-110 min, for example, 101 min, 103 min, 105 min, 107 min, or 109 min. Preferably, the solvent used for ball milling can be water, and the milling medium can be iron balls. Here, the mass ratio of calcium carbonate powder, hydroxylated iron ore powder, water, and iron balls can be 1:(1.5-1.8):(2.5-2.8):(6-7), for example, 1:1.6:2.6:6.5, 1:1.7:2.7:6.8, or 1:1.7:2.6:6.6.

[0025] In this embodiment, the drying temperature can be 80–90°C, for example, 82°C, 85°C, 87°C, or 89°C, and the time can be 160–180 min, for example, 165 min, 171 min, 175 min, or 178 min. Here, drying can be performed using an oven.

[0026] Exemplary Example 2

[0027] This exemplary embodiment provides a weighting agent, which may include a product prepared by the weighting agent preparation method described above.

[0028] To better understand the exemplary embodiments 1-2 above, a detailed description will be provided below with reference to specific examples and comparative models.

[0029] Example 1

[0030] (1) Iron ore powder with a particle size between 14 and 16 μm was mixed with a ferric chloride solution with a concentration of 22 wt% and stirred to obtain the first intermediate.

[0031] (2) Add tannic acid and potassium persulfate to the first intermediate under stirring, wherein, by mass ratio, iron ore powder: ferric chloride solution: tannic acid: potassium persulfate = 1:27:0.7:0.16, to obtain the second intermediate;

[0032] (3) The second intermediate is heated and kept at a temperature of 55°C for 24.5 hours. After filtration, washing and drying, hydroxylated iron ore powder is obtained.

[0033] (4) Calcium carbonate powder with a particle size between 56 and 57 μm was mixed with the obtained hydroxylated iron ore powder and ball-milled to obtain a mixture of the two. The ball milling time was 105 min, the mixing ball milling was carried out by wet ball milling, the ball milling solvent was water, the ball milling media was round iron balls, and the mass ratio of calcium carbonate powder: hydroxylated iron ore powder: water: round iron balls was 1:1.7:2.7:6.5.

[0034] (5) The mixture was dried at 85°C for 170 min and then naturally cooled to obtain weighting agent A1.

[0035] Example 2

[0036] (1) Iron ore powder with a particle size between 12 and 14 μm was mixed with a 20 wt% ferric chloride solution and stirred to obtain the first intermediate.

[0037] (2) Add tannic acid and potassium persulfate to the first intermediate under stirring, wherein, by mass ratio, iron ore powder: ferric chloride solution: tannic acid: potassium persulfate = 1:25:0.5:0.14, to obtain the second intermediate;

[0038] (3) The second intermediate is heated and kept at 50°C for 24 hours. After filtration, washing and drying, hydroxylated iron ore powder is obtained.

[0039] (4) Calcium carbonate powder with a particle size between 55 and 56 μm was mixed with the obtained hydroxylated iron ore powder and ball-milled to obtain a mixture of the two. The ball milling time was 100 min, the mixing ball milling was carried out by wet ball milling, the ball milling solvent was water, the ball milling media was round iron balls, and the mass ratio of calcium carbonate powder: hydroxylated iron ore powder: water: round iron balls was 1:1.5:2.5:6.

[0040] (5) The mixture is dried at 80°C for 160 min and then naturally cooled to obtain weighting agent A2.

[0041] Example 3

[0042] (1) Iron ore powder with a particle size between 16 and 18 μm was mixed with a 25 wt% ferric chloride solution and stirred to obtain the first intermediate.

[0043] (2) Add tannic acid and potassium persulfate to the first intermediate under stirring, wherein, by mass ratio, iron ore powder: ferric chloride solution: tannic acid: potassium persulfate = 1:30:0.8:0.18, to obtain the second intermediate;

[0044] (3) The second intermediate is heated and kept at 60°C for 25 hours. After filtration, washing and drying, hydroxylated iron ore powder is obtained.

[0045] (4) Calcium carbonate powder with a particle size between 57 and 58 μm was mixed with the obtained hydroxylated iron ore powder and ball-milled to obtain a mixture of the two. The ball milling time was 110 min, the ball milling was performed using a wet ball milling method, the ball milling solvent was water, the ball milling media was round iron balls, and the mass ratio of calcium carbonate powder: hydroxylated iron ore powder: water: round iron balls was 1:1.8:2.8:7.

[0046] (5) The mixture is dried at 90°C for 180 min and then naturally cooled to obtain weighting agent A3.

[0047] Comparative Example 1

[0048] Calcium carbonate powder with a particle size of 57 μm and iron ore powder with a particle size of 15 μm were mixed at a mass ratio of 1:1.7 to obtain weighting agent D1.

[0049] The weighting effects of the three weighting agents (A1, A2, A3) prepared in Examples 1-3 and the weighting agent D1 prepared in Comparative Example 1 were tested, as follows:

[0050] Prepare four cups of weighted drilling fluid, with the weighting agents in the four cups being weighting agents A1, A2, and A3 from Examples 1-3 and weighting agent D1 from Comparative Example 1, respectively.

[0051] By weight, 300 parts of water were added to four enamel measuring cups, and then 12 parts of bentonite, 1.5 parts of sodium hydroxide, 3 parts of sodium carboxymethyl cellulose, 9 parts of sulfonated methyl phenolic resin, 9 parts of sulfonated lignite, and 90 parts of weighting agent were added in sequence under stirring to obtain four types of weighting drilling fluids.

[0052] Samples were extracted from the upper, middle and lower parts of the enamel measuring cup using pipettes (using the siphon principle). The density of each sample was measured and recorded using a mud hydrometer. The results are shown in Table 1.

[0053] Table 1 Drilling Fluid Density

[0054]

[0055] Table 1 shows the density distribution of drilling fluids after adding four different weighting agents. The weighting agents prepared in Examples 1-3 resulted in uniform density throughout the drilling fluid, indicating that the calcium carbonate powder and iron ore powder achieved a stable bond, exerting a weighting effect as a whole. In contrast, the weighting agent prepared in Comparative Example 1 simply combined calcium carbonate powder and iron ore powder; after its addition to the drilling fluid, the calcium carbonate powder and iron ore powder dispersed, resulting in an uneven density distribution where some parts of the drilling fluid had high density and others low density.

[0056] In summary, the weighting agent prepared by this invention uses the method of forming chemical bonds to stabilize the substance, thereby combining calcium carbonate powder and iron ore powder into one, which stably increases the density of drilling fluid and makes the density distribution of drilling fluid uniform, which is beneficial to the control of drilling fluid settling stability.

[0057] Although the invention has been described above in conjunction with exemplary embodiments, those skilled in the art will understand that various modifications and changes can be made to the exemplary embodiments of the invention without departing from the spirit and scope defined by the claims.

Claims

1. A method for preparing a weighting agent, characterized in that, The preparation method includes the following steps: Iron ore powder is subjected to hydroxylation treatment to obtain hydroxylated iron ore powder; Calcium carbonate powder and hydroxylated iron ore powder were mixed and ball-milled to obtain a mixture of the two. The mixture is baked and cooled to obtain a weighting agent; Among them, the particle size of iron ore powder is 12-18 μm, and the particle size of calcium carbonate powder is 55-58 μm; The hydroxylation treatment includes the following steps: Iron ore powder was mixed with ferric chloride solution and stirred to obtain the first intermediate. Tannic acid, potassium persulfate, and the first intermediate are mixed to obtain the second intermediate; The second intermediate was post-processed to obtain hydroxylated iron ore powder; The post-processing includes: The second intermediate is heated and kept at a constant temperature; After filtration, washing, and drying, hydroxylated iron ore powder is obtained.

2. The method for preparing the weighting agent according to claim 1, characterized in that, The mass ratio of the iron ore powder, ferric chloride solution, tannic acid, and potassium persulfide is 1:(25-30):(0.5-0.8):(0.14-0.18).

3. The method for preparing the weighting agent according to claim 1, characterized in that, The insulation temperature is 50-60℃ and the time is 24-25h.

4. The method for preparing the weighting agent according to claim 1, characterized in that, The mixing ball milling adopts a wet ball milling method, the mixing ball milling time is 100-110 minutes, the ball milling solvent includes water, and the ball milling medium includes iron balls.

5. The method for preparing the weighting agent according to claim 4, characterized in that, The mass ratio of the calcium carbonate powder, hydroxylated iron ore powder, water, and iron balls is 1:(1.5-1.8):(2.5-2.8):(6-7).

6. The method for preparing the weighting agent according to claim 1, characterized in that, The baking temperature is 80-90℃ and the time is 160-180 min.

7. The method for preparing the weighting agent according to claim 1, characterized in that, The ferric chloride solution has a mass fraction of 20–25 wt%.

8. A weighting agent, characterized in that, The weighting agent includes the product prepared by the method for preparing the weighting agent according to any one of claims 1 to 7.

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