阅读说明：本技术 一种低密度碳化硅基复相陶粒支撑剂及其制备方法 (Low-density silicon carbide-based complex-phase ceramsite proppant and preparation method thereof ) 是由 杨兆中 廖梓佳 李小刚 薛屺 陈浩 杜博迪 舒鸫锟 于 2020-12-21 设计创作，主要内容包括：本发明公开了一种低密度碳化硅基复相陶粒支撑剂,该支撑剂以石英粉和废矿物油为原料烧制而成,具有碳化硅晶体结构；废矿物油中包含质量百分比20～50％的轻质油、20％以上的高碳重质油。支撑剂的制备方法步骤：以经过预处理后的废矿物油和石英粉为原料,添加无水乙醇和氧化硼,混合球磨；待无水乙醇挥发后,将球磨后的物料烘干,再研磨成粉体进行造粒成球,得到支撑剂素坯；将支撑剂素坯干燥后于真空条件下进行烧结,得到低密度碳化硅基复相陶粒支撑剂。与常规陶粒支撑剂相比,本发明制得的支撑剂具有高强度低密度的性能特征,且以废矿物油为原料,有利于废矿物油回收处理。(The invention discloses a low-density silicon carbide-based complex-phase ceramsite proppant, which is prepared by firing quartz powder and waste mineral oil serving as raw materials and has a silicon carbide crystal structure; the waste mineral oil contains 20-50% of light oil and more than 20% of high-carbon heavy oil by mass percent. The preparation method of the proppant comprises the following steps: taking pretreated waste mineral oil and quartz powder as raw materials, adding absolute ethyl alcohol and boron oxide, mixing and ball-milling; after the absolute ethyl alcohol is volatilized, drying the ball-milled materials, grinding the materials into powder, and granulating the powder into balls to obtain a propping agent biscuit; and drying the proppant biscuit, and sintering under a vacuum condition to obtain the low-density silicon carbide-based complex-phase ceramsite proppant. Compared with the conventional ceramic proppant, the proppant prepared by the invention has the performance characteristics of high strength and low density, and the waste mineral oil is used as the raw material, so that the recovery treatment of the waste mineral oil is facilitated.)

1. The low-density silicon carbide-based complex-phase ceramsite proppant is characterized in that the proppant is prepared by firing quartz powder and waste mineral oil serving as raw materials and has a silicon carbide crystal structure; the waste mineral oil comprises 20-50% of light oil and more than 20% of high-carbon heavy oil by mass percent; the silica powder has a silica content of more than 90% and is prepared by crushing natural quartz stone.

2. The preparation method of the low-density silicon carbide-based complex-phase ceramsite proppant as set forth in claim 1, wherein the preparation method comprises the following steps:

s1, pretreatment of waste mineral oil: heating the waste mineral oil raw material to 40-60 ℃, performing oil-water separation by using a centrifuge, adding a flocculating agent into the separated oil, stirring for 60min, and filtering to remove impurities in the oil;

s2, taking quartz powder and waste mineral oil as raw materials, adding absolute ethyl alcohol and boron oxide, mixing and ball-milling; after the absolute ethyl alcohol is volatilized, drying the ball-milled materials at 100-120 ℃ for more than 4 hours, and then grinding the materials into powder;

s3, granulating the powder into balls, and spraying a binder in the granulating process to obtain spherical proppant biscuits;

and S4, drying the proppant biscuit, sintering under a vacuum condition, cooling and screening to obtain the low-density silicon carbide-based complex phase ceramsite proppant.

3. The method for preparing the low-density silicon carbide-based complex-phase ceramsite proppant as set forth in claim 2, wherein the flocculant is cationic polyacrylamide, and the addition amount of the flocculant is 1% -5% of the mass of the waste mineral oil.

4. The method for preparing the low-density silicon carbide-based complex phase ceramsite proppant as set forth in claim 2, wherein the step S2 specifically comprises: firstly, quartz powder and boron oxide are mixed and ball-milled by a dry method to obtain powder with the particle size of more than 85 percent below 30um, and then waste mineral oil and absolute ethyl alcohol are added for mixing and wet milling.

5. The method for preparing the low-density silicon carbide-based complex phase ceramsite proppant as set forth in claim 4, wherein the mass ratio of the waste mineral oil to the quartz powder is more than 1, and the amount of the boron oxide accounts for 1-3% of the total mass of the waste mineral oil and the quartz powder.

6. The method for preparing the low-density silicon carbide-based complex phase ceramsite proppant as set forth in claim 3, wherein the binder is one of carboxymethyl cellulose, polyvinyl alcohol and water glass.

7. The method for preparing the low-density silicon carbide-based complex phase ceramsite proppant as recited in claim 2, wherein the sintering process in the step S4 specifically comprises: sintering under a vacuum environment, sintering for 1-2 h at 300-600 ℃, then sintering for 1-2 h at 1000-1100 ℃, and finally sintering for 1-2 h at 1450 ℃ to generate the low-density silicon carbide-based complex phase ceramsite proppant.

8. The method for preparing the low-density silicon carbide-based complex phase ceramsite according to claim 7, wherein the temperature rising rate is 5 ℃/min in the step S4.

Technical Field

The invention relates to the technical field of oil and gas field development, in particular to a low-density silicon carbide-based complex-phase ceramsite proppant and a preparation method thereof.

Background

The hydraulic fracturing is the most widely applied technology in the yield increasing reconstruction of oil and gas fields, and is characterized in that a liquid with certain viscosity is injected into a stratum by utilizing a ground high-pressure pump set to enable the stratum to generate artificial fractures. After the artificial fracture is created, it is necessary to further inject a proppant-carrying fluid in order to prevent it from closing under formation stress. After fracturing, the propping agent is left in the underground fracture to keep the fracture open and increase the flow conductivity of the fracture, thereby achieving the purpose of increasing the yield of the oil and gas field. Therefore, the proppant plays an important role in hydraulic fracturing and is one of the key materials influencing the hydraulic fracturing effect.

The current proppants used in China are mainly quartz sand and ceramsite. The quartz sand is mainly prepared by crushing quartz stone and has the apparent density of 2.65g/cm³And on the other hand, the method has better yield-increasing effect in a reservoir with low closing pressure. However, the silica sand has a low compressive strength and starts to be crushed under a closure stress of 20 MPa. In a high-closure-stress reservoir, particularly for the fracturing of the current deep shale gas well, the proppant mainly takes ceramsite as a main component. The ceramsite is generally prepared by taking medium-low grade bauxite as a raw material and adding additives such as pyrolusite, dolomite and the like for sintering, mainly contains a glass phase, a mullite phase and a corundum phase, and has the apparent density of 2.7-3.4g/cm³In the meantime.

The ideal ceramsite proppant should have both low density and high strength characteristics. The lower the density of the proppant, the more beneficial it is to pump to the distal end of the fracture, increasing the propped area. The higher the strength of the propping agent is, the propping agent is not easy to break under high closure stress, and can effectively prop a fracturing fracture. Most of the existing ceramic proppant is sintered from bauxite, and the phase is mainly formed from mullite phase. The higher the proppant strength, the higher the mullite phase content. However, with the gradual decrease of bauxite resources in China, people have more and more tried to prepare fracturing propping agents by replacing bauxite with other raw materials, but the bauxite is still difficult to be completely abandoned as one of the main raw materials for production. For example, patent 201610694698.0 discloses "a fracturing propping agent for oil and gas wells fired by fly ash and a preparation method thereof", which adopts 30-50 wt% of fly ash, 1-10 wt% of titanium dioxide and up to 50-70 wt% of bauxite. The low-density ceramsite proppant disclosed in patent 2009101028785 is prepared from 62-75 wt% of kaolin, 1-6 wt% of manganese dioxide, 0.5-2 wt% of magnesium oxide and 17-30 wt% of high-grade bauxite.

On the other hand, the waste mineral oil is oil extracted and refined from petroleum, coal and oil shale, but the original physical and chemical properties of the oil cannot be used continuously, and belongs to dangerous waste, such as oil-based mud in the drilling process, ballast waste oil in the transportation industry and the like. The problem of disposing of waste mineral oil is always the core of disturbing local ecological environment protection, and especially with the gradual rise of urban population environmental awareness in recent years, the treatment of waste mineral oil has more strict requirements.

Disclosure of Invention

The invention aims to provide a low-density silicon carbide-based complex-phase ceramsite proppant prepared by taking waste mineral oil as a raw material.

The low-density silicon carbide-based complex-phase ceramsite proppant provided by the invention is prepared by firing quartz powder and waste mineral oil serving as raw materials. The proppant has a silicon carbide crystal structure. The waste mineral oil comprises 20-50% of light oil and more than 20% of high-carbon heavy oil by mass percent. The silica powder has a silica content of more than 90% and is prepared by crushing natural quartz stone.

The carbon content of the light oil is lower than 10, the light oil and the heavy oil have obvious layering phenomenon, and the light oil can volatilize at the temperature lower than 600 ℃ in the sintering process to form a certain porous structure in the proppant. The high-carbon heavy oil has high carbon content and high boiling point, can react with silicon oxide at high temperature, and is used as a carbon source for preparing the silicon carbide structural proppant. .

The method for measuring the content of light oil and heavy oil in the waste mineral oil comprises the following steps:

(1) taking the weight as m₀Heating the waste mineral oil to 60 ℃, performing oil-water separation by using a centrifugal machine, and collecting an oil phase;

(2) taking a paper cup, weighing the weight m of the empty paper cup₁Then pouring the oil phase into a paper cup, and weighing the total weight m of the paper cup and the oil₂Standing for 30 minutes until the upper layer floats light oil, slowly pouring out the light oil, obtaining paste adhered to the wall surface of the paper cup as heavy oil, weighing the weight m of the paper cup adhered with the heavy oil₃The content of light oil is equal to (m)₂-m₃)/m₀The content of heavy oil is equal to (m)₃-m₁)/m₀。

The preparation method of the proppant comprises the following steps:

s1, pretreatment of waste mineral oil: heating the waste mineral oil raw material to 40-60 ℃, and performing oil-water separation by using a centrifuge; because the oil contains a small amount of mechanical impurities, the mechanical impurities refer to precipitates or suspensions that are insoluble in the oil and specified solvents, such as silt, dust, iron filings, fibers, and certain insoluble salts; in order to remove impurities, adding a flocculating agent into the separated oil, stirring for 60min, and filtering to remove impurities in the oil; the preferable flocculating agent is cationic polyacrylamide, and the addition amount is 1 to 5 percent of the mass of the waste mineral oil.

S2, taking quartz powder and waste mineral oil as raw materials, adding absolute ethyl alcohol and boron oxide, mixing and ball-milling; after the absolute ethyl alcohol is volatilized, drying the ball-milled materials at 100-120 ℃ for more than 4 hours, and then grinding the materials into powder;

s3, granulating the dry powder into balls, and spraying a binder in the granulating process to obtain spherical proppant biscuits;

and S4, drying the proppant biscuit, sintering under a vacuum condition, cooling and screening to obtain the low-density silicon carbide-based complex phase ceramsite proppant.

Preferably, the step S2 is specifically: firstly, mixing quartz powder and boron oxide, performing dry ball milling to obtain powder with the particle size of more than 85% below 30um, adding waste mineral oil and absolute ethyl alcohol, mixing and wet milling, drying the solidified powder for more than 4 hours at the temperature of 100-120 ℃ after the absolute ethyl alcohol is volatilized, and then grinding into powder dry materials. Wherein the mass ratio of the waste mineral oil to the quartz powder is more than 1, and the mass of the boron oxide accounts for 1-3% of the total mass of the waste mineral oil and the quartz powder.

The binder is one of carboxymethyl cellulose, polyvinyl alcohol and water glass.

The sintering process in the step S4 specifically includes: sintering under a vacuum environment, sintering for 1-2 h at 300-600 ℃, evaporating light oil, sintering for 1-2 h at 1000-1100 ℃, generating a carbon-silicon oxide-boron oxide primary reaction, finally sintering for 1-2 h at 1450 ℃, and controlling the heating rate to be 5 ℃/min in the whole process to generate the low-density silicon carbide-based complex-phase ceramsite proppant.

Compared with the prior art, the invention has the advantages that:

(1) at present, the existing ceramsite proppant mainly takes an oxide phase as a main component and is mainly based on an ore phase structure of alumina-mullite-quartz. The low-density silicon carbide-based complex-phase ceramsite proppant provided by the invention has a silicon carbide crystal structure, and is prepared by firing quartz powder and waste mineral oil which serve as raw materials, oil in the waste mineral oil which serves as a carbon source prepared by using the proppant and boron oxide which serves as a sintering aid. The proppant prepared by the method has higher sphericity (more than 0.8) and lower apparent density (less than or equal to 2.5 g/cm)³) The compressive strength reaches 69MPa, and meanwhile, the composite material has certain oleophylic and hydrophobic properties and higher flow conductivity than the oxide phase ceramsite proppant of the same grade. Silicon carbide has comparable density but higher strength compared to mullite. The proppant has higher strength than the conventional ceramsite proppant under the same density.

(2) The invention not only prepares the fracturing propping agent with low density and high strength, but also provides a new method for recovering and treating the waste mineral oil.

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

Drawings

FIG. 1 is a flow chart of a preparation process of a low-density silicon carbide-based complex-phase ceramsite proppant.

FIG. 2 is a morphology diagram of a single-particle low-density silicon carbide-based complex-phase ceramsite proppant.

Detailed Description

The preferred embodiments of the present invention will be described in conjunction with the accompanying drawings, and it will be understood that they are described herein for the purpose of illustration and explanation and not limitation.

Example 1

A preparation method of a low-density silicon carbide-based complex-phase ceramsite proppant comprises the following steps:

s1, waste mineral oil pretreatment: heating the waste mineral oil raw material to 60 ℃, and performing oil-water separation by using a centrifugal machine; adding cationic polyacrylamide with the oil mass of 3% into the separated oil phase, stirring for 60min, and filtering to remove impurities in the oil.

S2, setting the ball milling rotation speed to be 300r/min, weighing 50g of quartz powder and 1g of boron oxide, mixing and ball milling for 12 hours to obtain more than 85% of powder with the particle size of below 30 microns; then 50g of pretreated waste mineral oil and 160g of absolute ethyl alcohol are added, and the mixture is mixed and wet-milled for 1 hour; and after the absolute ethyl alcohol is volatilized, drying the ball-milled materials at 100 ℃ for 4 hours, and grinding the materials by using a quick grinding machine after drying to obtain dry powder materials. Taking quartz powder and waste mineral oil as raw materials, adding absolute ethyl alcohol and boron oxide, mixing and ball-milling;

and S3, granulating the dry powder material into balls in a disc granulator, and spraying polyvinyl alcohol liquid in the granulating process to obtain spherical proppant biscuit.

S4, drying the proppant biscuit, sintering at 600 ℃ for 1h, sintering at 1000 ℃ for 1h and sintering at 1450 ℃ for 1h in a vacuum environment, keeping the heating rate at 5 ℃/min, cooling and screening to obtain particles with the particle size of 0.212-0.850 mm, namely the low-density silicon carbide-based complex phase ceramsite proppant.

Example 2

A preparation method of a low-density silicon carbide-based complex-phase ceramsite proppant comprises the following steps:

s1, waste mineral oil pretreatment: heating the waste mineral oil raw material to 40 ℃, and performing oil-water separation by using a centrifugal machine; adding cationic polyacrylamide with the oil mass of 3% into the separated oil phase, stirring for 60min, and filtering to remove impurities in the oil.

S2, setting the ball milling rotation speed to be 300r/min, weighing 50g of quartz powder and 1.25g of boron oxide, mixing and ball milling for 12 hours to obtain more than 85% of powder with the particle size of below 30 microns; then 75g of pretreated waste mineral oil and 200g of absolute ethyl alcohol are added, and the mixture is mixed and wet-milled for 1 hour; and after the absolute ethyl alcohol is volatilized, drying for 4 hours at the temperature of 120 ℃, and grinding by using a quick grinding machine after drying to obtain a dry powder material.

And S3, granulating the dry powder material into balls in a disc granulator, and spraying water glass in the granulating process to obtain spherical proppant biscuit.

S4, drying the proppant biscuit, sintering at 300 ℃ for 2h, sintering at 1100 ℃ for 2h and sintering at 1450 ℃ for 2h in a vacuum environment, keeping the heating rate at 5 ℃/min, cooling and screening to obtain particles with the particle size of 0.212-0.850 mm, namely the low-density silicon carbide-based complex-phase ceramsite proppant.

Example 3

A preparation method of a low-density silicon carbide-based complex-phase ceramsite proppant comprises the following steps:

s1, waste mineral oil pretreatment: heating the waste mineral oil raw material to 50 ℃, and performing oil-water separation by using a centrifugal machine; adding cationic polyacrylamide with the oil mass of 3% into the separated oil phase, stirring for 60min, and filtering to remove impurities in the oil.

S2, setting the ball milling rotation speed to be 300r/min, weighing 50g of quartz powder and 1.25g of boron oxide, mixing and ball milling for 12 hours to obtain more than 85% of powder with the particle size of below 30 microns; then 75g of pretreated waste mineral oil and 200g of absolute ethyl alcohol are added, and the mixture is mixed and wet-milled for 1 hour; and after the absolute ethyl alcohol is volatilized, drying for 4 hours at the temperature of 110 ℃, and grinding by using a quick grinding machine after drying to obtain a dry powder material.

And S3, granulating the dry powder material into balls in a disc granulator, and spraying carboxymethyl cellulose liquid in the granulating process to obtain spherical proppant biscuit.

S4, drying the proppant biscuit, sintering at 300 ℃ for 2h, sintering at 1100 ℃ for 2h and sintering at 1550 ℃ for 1h in a vacuum environment, keeping the heating rate at 5 ℃/min, cooling and screening to obtain particles with the particle size of 0.212-0.850 mm, namely the low-density silicon carbide-based complex-phase ceramsite proppant.

And (3) performance testing:

apparent density, which is a density that characterizes the volume of pores between proppant-free cells, is typically measured with a low viscosity liquid that wets the surface of the particles, including the volume of pores inaccessible to the liquid.

The breaking rate refers to the percentage of the proppant broken under the specified closed pressure condition, and the specific test condition is that m is weighed₁g, pouring the propping agent into a crushing chamber, placing the crushing chamber at the central position of a test board of the automatic press, selecting a value (such as 69MPa) to be tested, starting a program, taking out the crushing chamber after the automatic test is finished, screening crushed fine powder by using the granularity lower limit corresponding to the propping agent, weighing and recording the crushed fine powder as m₂，m₂/m₁Namely the breakage rate.

Fracture conductivity generally refers to the ability of a proppant pack to pass through a fluid, and is expressed by the product of the permeability of the proppant pack and the width of a propped fracture, and can be used for evaluating and screening proppants.

And (3) screening and selecting particles with the particle size of 0.425-0.850 mm according to SY/T5108-2014 of oil and gas industry standard of the people's republic of China, and testing the apparent density and the breakage rate. And (3) screening and selecting particles with the particle size of 0.212-0.425 mm according to the oil and gas industry standard SY/T6302-2009 of the people's republic of China to perform crack conductivity test.

The test results are given in the following table:

proppant samples	Apparent density (g/cm)3)	Breaking rate at 69MPa	Crack conductivity (um) at 69MPa2*cm)
				Example 1	2.28	5.8％	45
Example 2	2.35	4.4％	48
				Example 3	2.45	2.7％	56

To evaluate the performance levels of the proppant of the present invention, applicants consulted the existing 3 same type proppant literature documents to compare with the proppant performance of the present invention.

Document 1 is patent 201910735343.5 a method for preparing low density proppant from oil-based mud waste, by which proppant having particle size of 0.212 to 0.425mm and apparent density of 2.3g/cm is obtained³But the compressive strength is 52MPa, while the compressive strength of the proppant prepared by the method reaches 69 MPa.

The document 2 is patent 201910905037.1, which discloses a fracturing proppant sintered by using thermal desorption residues of oil-based drill cuttings and a preparation method thereof, and the method is used for preparing the fracturing proppant with the particle size of 0.212-0.425 mm, wherein the compressive strength of the proppant reaches 86MPa, but the apparent density of the proppant is more than 2.5g/cm³And the density of the proppant is higher than that of the proppant prepared by the method.

Document 3 is a patent 202010299091.9 of a high strength low density ceramic proppant and a method for preparing the same, by which a ceramic proppant of a conventional oxide phase is prepared. The apparent density of the proppant is 2.61-2.68 g/cm³And the breaking rate is lower than 5% under the closing pressure of 52Mpa, and compared with the silicon carbide-based complex phase ceramsite proppant prepared by the method, the density is high and the strength is low.

In conclusion, the proppant disclosed by the invention is prepared by taking waste mineral oil and quartz powder as main raw materials and performing pretreatment, blending, ball milling, drying, grinding, granulating, drying, sintering, cooling and screening on the waste mineral oil. Different from the conventional ceramsite proppant based on the alumina-mullite-quartz mineral phase structure, the proppant prepared by the method has a silicon carbide crystal structure and has higher strength than the conventional ceramsite proppant. The invention not only prepares the fracturing propping agent with low density and high strength, but also provides a new method for recovering and treating the waste mineral oil.

Although the present invention has been described with reference to a preferred embodiment, it should be understood that various changes, substitutions and alterations can be made herein without departing from the spirit and scope of the invention as defined by the appended claims.