Foundry sand-coated proppant and method of making same

Abstract

The application provides a foundry old sand coated proppant and a preparation method thereof. The raw material for preparing the foundry old sand coated proppant comprises foundry old sand, organic resin, graphite, silane coupling agent, curing agent and calcium stearate. The foundry old sand is subjected to surface modification by a low-resin-amount coating technology, and the resin can completely cover the sand particles, so that the high turbidity problem of the foundry old sand is solved, and the breakage rate and acid solubility of the proppant are effectively reduced; the cost is low, the performance is good, and the foundry old sand can be completely used as the proppant. The foundry old sand is used to replace the non-renewable silica sand resource, so that the resource is effectively saved, and the environment is protected.

Description

Technical Field

[0001] This invention belongs to the field of petroleum proppant, specifically relating to a casting sand coating proppant and its preparation method. Background Technology

[0002] Silica sand fracturing proppant is the most widely used propping material in oilfield development. During oilfield development, high-pressure fracturing technology is used to open fractures in the rock of the oil-bearing layer, and then proppant is injected into the fracture along with the fracturing fluid to provide support and increase oil extraction efficiency. Considering that silica sand is a non-renewable resource, and tens of millions of tons of silica sand are being consumed rapidly every year, there is an urgent need to find alternative materials to natural silica sand.

[0003] On the other hand, the foundry industry generates tens of millions of tons of foundry sand every year. Most of this foundry sand is disposed of by landfill, and long-term accumulation will pollute the natural environment. In particular, after being washed by rainwater and the migration of groundwater, the resin and heavy metals in the foundry sand will cause serious pollution to water resources. Therefore, it is urgent to find a way to deal with foundry sand. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides a casting sand coating support agent and its preparation method. By using a low resin content coating technology to modify the surface of casting sand, the resulting modified casting sand can be reused completely, saving materials and protecting the environment.

[0005] To achieve the above objectives, the present invention adopts the following technical solution: On one hand, the present invention provides a casting sand coating support agent, the raw materials for preparing the casting sand coating support agent include: casting sand, organic resin, graphite, silane coupling agent, curing agent and calcium stearate.

[0006] Preferably, the foundry sand comprises 100 parts by weight, the organic resin comprises 0.1-0.6 parts by weight, the graphite comprises 0.01-0.50 parts by weight, the silane coupling agent comprises 0.01-0.10 parts by weight, the curing agent comprises 0.01-0.1 parts by weight, and the calcium stearate comprises 0.05-0.10 parts by weight.

[0007] Preferably, the particle size of the foundry sand is 40 / 70.

[0008] Preferably, the organic resin includes phenolic resin or epoxy resin.

[0009] Preferably, the graphite is of an earthy or flaky form with a particle size of 300-2000 mesh.

[0010] Preferably, the curing agent includes hexamethylenetetramine or organic ammonia.

[0011] On the other hand, the present invention provides a method for preparing the aforementioned casting sand coating support agent, comprising the following steps: S1. Heat the old foundry sand and mix it with organic resin, graphite, silane coupling agent, curing agent and calcium stearate to obtain a mixture; S2. Cool the mixture to obtain a casting old sand coating support.

[0012] Preferably, the foundry sand needs to undergo a crushing step before use. The specific steps are as follows: crush the foundry sand to a particle size of ≤2mm using a crusher, remove the upper coarse particles using a coarse screen, and remove the lower fine particles using a fine screen.

[0013] Preferably, the coarse screen includes one of 10, 20, 30, 40, and 50 mesh, and the fine screen includes one of 40, 50, 70, 100, and 140 mesh.

[0014] Preferably, in step S1, the temperature is heated to 150-250°C.

[0015] Compared with the prior art, the beneficial effects of the present invention are as follows: Foundry sand is coated with materials such as clay and resin, and its surface has a high ash content, especially after casting, which fails to meet the technical requirements for turbidity. Directly replacing natural silica sand would cause blockages and affect the efficiency of oil extraction. Therefore, this invention uses a low-resin coating technology to modify the surface of foundry sand. The resin completely covers the sand particles, solving not only the high turbidity problem of foundry sand but also effectively reducing the breakage rate and acid solubility of the proppant. It is low-cost, high-performance, and can be reused as a proppant. Using foundry sand to replace non-renewable silica sand resources effectively conserves resources and protects the environment. Detailed Implementation

[0016] The present invention will now be described in further detail with reference to specific embodiments, so that those skilled in the art can more clearly understand the present invention.

[0017] Silica sand fracturing proppant is the most widely used propping material in oilfield development. During oilfield development, high-pressure fracturing technology is used to open fractures in the rock of the oil-bearing layer, and then proppant is injected into the fracture along with the fracturing fluid to provide support and increase oil extraction efficiency. Considering that silica sand is a non-renewable resource, and tens of millions of tons of silica sand are being consumed rapidly every year, there is an urgent need to find alternative materials to natural silica sand.

[0018] On the other hand, the foundry industry generates tens of millions of tons of foundry sand every year. Most of this foundry sand is disposed of by landfill, and long-term accumulation will pollute the natural environment. In particular, after being washed by rainwater and the migration of groundwater, the resin and heavy metals in the foundry sand will cause serious pollution to water resources. Therefore, it is urgent to find a way to deal with foundry sand.

[0019] To solve the above-mentioned technical problems, the present invention provides a casting sand coating support agent. The raw materials for preparing the casting sand coating support agent include: casting sand, organic resin, graphite, silane coupling agent, curing agent and calcium stearate.

[0020] Furthermore, the weight percentages of the foundry sand are 100 parts, the weight percentages of the organic resin are 0.1-0.6 parts, the weight percentages of the graphite are 0.01-0.50 parts, the weight percentages of the silane coupling agent are 0.01-0.10 parts, the weight percentages of the curing agent are 0.01-0.1 parts, and the weight percentages of the calcium stearate are 0.05-0.10 parts.

[0021] Furthermore, the particle size of the foundry sand is 40 / 70.

[0022] Furthermore, the organic resin includes phenolic resin or epoxy resin.

[0023] Furthermore, the graphite is of an earthy or flaky form with a particle size of 300-2000 mesh.

[0024] Furthermore, the curing agent includes hexamethylenetetramine or organic ammonia.

[0025] On the other hand, the present invention provides a method for preparing the aforementioned casting sand coating support agent, comprising the following steps: S1. Heat the old foundry sand and mix it with organic resin, graphite, silane coupling agent, curing agent and calcium stearate to obtain a mixture; S2. Cool the mixture to obtain a casting old sand coating support.

[0026] It should be noted that, in some embodiments, the steps for preparing the mixture are as follows: Take 100 parts of the sieved foundry sand, add it to a batch heating machine, heat it to 150-250℃, and then add it to a sand mixer. Take 0.1-0.6 parts of organic resin, add it to the sand mixer, and stir for 5-20 seconds. Take 0.01-0.50 parts of graphite, add it to the sand mixer, and stir for 2-10 seconds. Add 0.01-0.10 parts of silane coupling agent, and stir for 2-10 seconds. Add 0.01-0.1 parts of curing agent, and stir for 10-50 seconds. Add 0.05-0.10 parts of calcium stearate, stir and crush for 20-50 seconds, and then discharge and cool.

[0027] Furthermore, the foundry sand needs to undergo a crushing process before use. Specifically, the foundry sand is crushed to a particle size of ≤2mm using a crusher, the upper coarse particles are removed using a coarse screen, and the lower fine particles are removed using a fine screen.

[0028] Furthermore, the coarse screen includes one type of 10, 20, 30, 40, or 50 mesh, and the fine screen includes one type of 40, 50, 70, 100, or 140 mesh.

[0029] Further, in step S1, the temperature is increased to 150-250°C.

[0030] Example 1 This embodiment provides a method for preparing a coating support for foundry sand, comprising the following steps: 1. Take old foundry sand and crush it to a particle size of ≤2mm using a crusher.

[0031] 2. Use a 30-mesh coarse sieve to remove the upper layer of coarse particles; use a 70-mesh fine sieve to remove the lower layer of fine particles; thus obtaining 40 / 70 grade foundry waste sand.

[0032] 3. Take 100 portions of the sieved foundry sand, put it into the batch heating machine, heat it to 170°C, and then put it into the sand mixer.

[0033] 4. Take 0.5 parts of epoxy resin, put it into a sand mixer, and stir for 10 seconds.

[0034] 5. Take 0.02 parts of 300-mesh soil-like graphite, put it into a sand mixer, and stir for 6 seconds.

[0035] 6. Add 0.02 parts of silane coupling agent and stir for 3 seconds.

[0036] 7. Add 0.02 parts of organic ammonia curing agent and stir for 30 seconds.

[0037] 8. Add 0.08 parts of calcium stearate, stir and crush for 30 seconds, then discharge and cool.

[0038] 9. Discharged from the sand mixer, the finished silica sand proppant is obtained.

[0039] Example 2 This embodiment provides a method for preparing a coating support for foundry sand, comprising the following steps: 1. Take old foundry sand and crush it to a particle size of ≤2mm using a crusher.

[0040] 2. Use a 30-mesh coarse sieve to remove the upper layer of coarse particles; use a 70-mesh fine sieve to remove the lower layer of fine particles; thus obtaining 40 / 70 grade foundry waste sand.

[0041] 3. Take 100 portions of the sieved foundry sand, put it into the batch heating machine, heat it to 170°C, and then put it into the sand mixer.

[0042] 4. Take 0.1 parts of epoxy resin, put it into a sand mixer, and stir for 10 seconds.

[0043] 5. Take 0.01 parts of 300-mesh soil-like graphite, put it into a sand mixer, and stir for 6 seconds.

[0044] 6. Add 0.01 parts of silane coupling agent and stir for 3 seconds.

[0045] 7. Add 0.01 parts of organic ammonia curing agent and stir for 30 seconds.

[0046] 8. Add 0.05 parts of calcium stearate, stir and crush for 30 seconds, then discharge and cool.

[0047] 9. Discharged from the sand mixer, the finished silica sand proppant is obtained.

[0048] Example 3 This embodiment provides a method for preparing a coating support for foundry sand, comprising the following steps: 1. Take old foundry sand and crush it to a particle size of ≤2mm using a crusher.

[0049] 2. Use a 30-mesh coarse sieve to remove the upper layer of coarse particles; use a 70-mesh fine sieve to remove the lower layer of fine particles; thus obtaining 40 / 70 grade foundry waste sand.

[0050] 3. Take 100 portions of the sieved foundry sand, put it into the batch heating machine, heat it to 170°C, and then put it into the sand mixer.

[0051] 4. Take 0.5 parts of epoxy resin, put it into a sand mixer, and stir for 10 seconds.

[0052] 5. Take 0.5 parts of 300-mesh soil-like graphite, put it into a sand mixer, and stir for 6 seconds.

[0053] 6. Add 0.1 parts of silane coupling agent and stir for 3 seconds.

[0054] 7. Add 0.1 parts of organic ammonia curing agent and stir for 30 seconds.

[0055] 8. Add 0.1 parts of calcium stearate, stir and crush for 30 seconds, then drain and cool.

[0056] 9. Discharged from the sand mixer, the finished silica sand proppant is obtained.

[0057] Comparative Example 1 Natural silica sand is selected as aggregate, and no surface pretreatment is performed.

[0058] Comparative Example 2 This comparative example provides a method for preparing a coating support for foundry old sand, which is the same as in Example 1, except that step 2 is removed and the old sand is not screened.

[0059] Comparative Example 3 This comparative example provides a method for preparing a coating support for foundry sand, which is the same as in Example 1, except that steps 3-9 are omitted, the foundry sand is not surface-treated, and it is directly used in the finished surface support.

[0060] Comparative Example 4 This comparative example provides a method for preparing a casting sand coating support, which is the same as in Example 1, except that the graphite is removed.

[0061] Comparative Example 5 This comparative example provides a method for preparing a coating support for old foundry sand, which is the same as in Example 1, except that the addition of a silane coupling agent is removed.

[0062] Performance Tests and Results The breakage rate, acid solubility, and sphericity are tested according to the standard SY / T 5108-2014.

[0063] The flowability test involved quantitatively dispensing 100g of proppant into a conical fixed container. The container's inlet was 5cm above the tabletop, and a flow guide metal rail was connected to the inlet. The dispensing valve was opened to allow the proppant to flow out along the rail, and the horizontal distance from the end point of the proppant flow to the inlet was recorded. The greater the distance, the better the flowability. The results are shown in Table 1.

[0064] Table 1

[0065] As shown in Table 1, using natural silica sand instead of recycled foundry sand as aggregate, without surface pretreatment, increased the breakage rate from 3.6% to 10.2%, acid solubility from 2.6% to 5.6%, and fluidity from 126 mm to 98 mm. The sphericity decreased from 0.7 to 0.6. This indicates that the surface-modified recycled foundry sand used as proppant aggregate in this invention has significant performance advantages over natural silica sand.

[0066] Comparing Example 1 and Comparative Example 2, Table 1 shows that without screening the old sand, the breakage rate increased from 3.6% to 6.2%, the acid solubility increased from 2.6% to 5.9%, and the flowability decreased from 126 mm to 102 mm. This indicates that screening is also crucial in this invention. Screening out coarser and finer particles and increasing the concentration of sand particle size helps improve flowability, thereby enhancing the surface modification effect.

[0067] Comparing Example 1 and Comparative Example 3, Table 1 shows that without surface treatment of the foundry sand, the breakage rate increased from 3.6% to 9.8%, the acid solubility increased from 2.6% to 7.8%, and the fluidity decreased from 126 mm to 96 mm. This demonstrates that surface modification is crucial in this invention.

[0068] Comparing Example 1 and Comparative Example 4, Table 1 shows that removing the added graphite increased acid solubility from 2.6% to 5.0%, and decreased fluidity from 126 mm to 98 mm. This indicates that the addition of graphite in this invention plays a crucial role in improving the fluidity of the proppant.

[0069] Comparing Example 1 and Comparative Example 5, as shown in Table 1, removing the added silane coupling agent increased the breakage rate from 3.6% to 5.2%, indicating that the silane coupling agent added in this invention plays a key role in reducing the breakage rate of the proppant.

[0070] All other raw materials or structures not specifically described in this invention already exist in the prior art and can be purchased directly from the market.

[0071] The above are merely preferred embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A casting sand coating support agent, characterized in that, The raw materials for preparing the casting sand coating support include: casting sand, organic resin, graphite, silane coupling agent, curing agent, and calcium stearate.

2. The casting sand coating support agent according to claim 1, characterized in that, The composition of the foundry sand is 100 parts by weight, the composition of the organic resin is 0.1-0.6 parts by weight, the composition of the graphite is 0.01-0.50 parts by weight, the composition of the silane coupling agent is 0.01-0.10 parts by weight, the composition of the curing agent is 0.01-0.1 parts by weight, and the composition of the calcium stearate is 0.05-0.10 parts by weight.

3. The casting sand coating support agent according to claim 1, characterized in that, The particle size of the foundry sand is 40 / 70.

4. The casting sand coating support agent according to claim 1, characterized in that, The organic resin includes phenolic resin or epoxy resin.

5. The casting sand coating support agent according to claim 1, characterized in that, The graphite is of an earthy or flaky form with a particle size of 300-2000 mesh.

6. The casting sand coating support agent according to claim 1, characterized in that, The curing agent includes hexamethylenetetramine or organic ammonia.

7. The method for preparing the casting sand coating support according to any one of claims 1-6, characterized in that, Includes the following steps: S1. Heat the old foundry sand and mix it with organic resin, graphite, silane coupling agent, curing agent and calcium stearate to obtain a mixture; S2. Cool the mixture to obtain a casting old sand coating support.

8. The preparation method according to claim 7, characterized in that, Before use, foundry sand needs to be crushed. The specific steps are as follows: crush the foundry sand to a particle size of ≤2mm using a crusher, remove the upper coarse particles using a coarse screen, and remove the lower fine particles using a fine screen.

9. The preparation method according to claim 8, characterized in that, Coarse screens include those with mesh sizes of 10, 20, 30, 40, and 50, while fine screens include those with mesh sizes of 40, 50, 70, 100, and 140.

10. The preparation method according to claim 7, characterized in that, In step S1, the temperature is raised to 150-250°C.

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