A method and system for treating waste drilling mud

Abstract

The present invention relates to the technical field of treatment of waste drilling mud, and in particular to a treatment method and system for waste drilling mud. The treatment method comprises: S1: mixing the waste drilling mud with an additive to obtain a solid-liquid mixture; S2: filtering the solid-liquid mixture to obtain a first oil-water mixture and oil mud; S3: allowing the first oil-water mixture to stand for stratification to obtain oil and high-salt water; S4: mixing the oil with the oil mud; heating and evaporating the high-salt water at 100-110°C to obtain water vapor and salt; condensing the water vapor to obtain low-salt water; S5: degelling, demulsifying and centrifuging the oil mud to obtain a second oil-water mixture and a solid mixture; S6: allowing the second oil-water mixture to stand to obtain oil and low-salt water. The present invention optimizes the treatment process, exchanges lower resource input for higher resource utilization, and combines the harmless treatment of mud with the treatment of high-salt water, so that the solid and liquid in the waste drilling mud are successfully separated and recovered.

Description

Technical Field

[0001] The invention relates to the technical field of processing waste drilling mud, and in particular to a processing method and a processing system for waste drilling mud. Background Art

[0002] Drilling activities are a vital step in the exploration and development of oil and gas. In order to ensure the safety and efficiency of drilling, a special liquid, called drilling mud, is introduced into the wellbore. This mud plays a variety of functions during the drilling process, including cooling and lubricating the drill bit, carrying drill cuttings to the surface, maintaining the stability of the hole wall, and resisting the high pressure underground, but as drilling proceeds, a large amount of mud will mix with the underground rocks and oil to form waste mud. This waste mud usually contains oil, suspended solids and various chemicals, and direct discharge into the environment will cause serious environmental pollution. Therefore, the effective treatment and recycling of drilling waste mud has become an important issue in the oil industry.

[0003] Prior art publication number CN104453747A discloses a resource utilization method for waste oil-based mud from oil and gas field drilling. First, the waste oil-based mud is collected in a receiving tank for sedimentation. After sedimentation, fluid mud is generated in the upper part and solid mud is generated in the lower part; the fluid mud and solid mud are poured into the barrel of a heating furnace for heating, cracking and evaporation. The oil, gas and water components generated by evaporation and cracking are sent to the oil and gas bag and condenser in turn for cooling, and then enter the oil, gas and water three-phase separator for separation. The oil generated after separation enters the oil product tank from the outlet for use, the water enters the condensing tank for use, and the combustible gas is sent to the heating furnace for use as fuel; the residue generated after distillation is discharged and used as raw material for briquette; the flue gas generated is discharged after being treated to meet the standards; the slag generated is discharged for paving or landfill.

[0004] Traditional mud treatment methods mainly include mechanical separation, chemical treatment and biological treatment. However, these methods have many defects. For example, mechanical separation methods are difficult to effectively separate tiny solid particles and oil; chemical treatment methods may introduce new pollutants; and biological treatment methods are slow and difficult to treat medium and high concentrations of oil pollution.

[0005] Therefore, developing a method for treating waste drilling mud has important research value and practical application prospects.

[0006] In view of this, the present invention is proposed. Summary of the invention

[0007] The purpose of the present invention is to provide a method and system for treating waste drilling mud, so as to solve the above technical problems and realize the comprehensive utilization of waste mud resources.

[0008] The specific technical solutions of the present invention are as follows:

[0009] In a first aspect, the present invention first provides a method for treating waste drilling mud, comprising:

[0010] S1: mixing the drilling waste mud with the additive to obtain a solid-liquid mixture;

[0011] S2: subjecting the solid-liquid mixture to filter pressing treatment to obtain a first oil-water mixture and oil sludge after filter pressing treatment;

[0012] S3: allowing the first oil-water mixture to stand and separate into layers, to obtain an upper layer of oil and a lower layer of high-salt water;

[0013] S4: mixing the upper layer oil with the oil sludge after the filter press treatment; heating and evaporating the high-salt water at 100-110° C. to obtain gaseous water vapor and solid salt; and then condensing the water vapor to obtain low-salt water;

[0014] S5: sequentially subjecting the oil sludge after the filter press treatment to degelling treatment, demulsification treatment and centrifugal separation treatment to obtain a second oil-water mixture and a solid mixture;

[0015] S6: The second oil-water mixture is allowed to stand for stratification to obtain an upper layer of oil and a lower layer of wastewater; the wastewater is introduced into S4 for heating, evaporation and condensation in sequence to obtain low-salt water.

[0016] The present invention finds that by optimizing the processing steps, the mud is first mixed with the additive and subjected to filter pressing, which is beneficial to effectively separate and recover the oil, solid and water in the mud at the relatively low heating evaporation temperature.

[0017] Preferably, the solid content of the sludge after the filter press treatment is 50-60wt%.

[0018] Preferably, the oil content in the first oil-water mixture is ≤2wt%

[0019] Preferably, the heating evaporation temperature is 100-110°C.

[0020] Preferably, the auxiliary agent is diatomaceous earth.

[0021] The present invention finds that when diatomaceous earth is added to the waste drilling mud, a better flow rate ratio is used to more effectively filter out fine suspended matter, further improve the clarity of oil and water, and thereby ensure that they can be effectively recycled.

[0022] Preferably, in the solid-liquid mixture, the amount of the auxiliary agent is 2-5wt%.

[0023] Preferably, before S1, the waste drilling mud is pretreated, and the pretreatment includes: controlling the solid content of the waste drilling mud to 10-15wt%; the oil content ≤2wt%; and the water content to 85-90wt%.

[0024] The present invention has found that, in specific implementation, the properties of the mud will also affect the effective treatment of oil, solids and water in the mud. For example, the complete separation of heavier oil and water in the mud poses certain challenges. Subsequent research has found that when the solid content and the oil and water content of the waste drilling mud are within the above ranges, it is more conducive to the effective separation of oil, solids and water in the mud.

[0025] In the present invention, before the waste drilling mud is processed, a sensor is first used to monitor the mud in real time to determine information such as the specific ratio of oil, solids and water in the mud.

[0026] Preferably, in S3, the degumming treatment comprises: mixing the oil sludge after the filter press treatment with a degumming agent at 60-90° C. to react to obtain a first mixed slurry.

[0027] Preferably, the breaker comprises calcium oxide and / or ferrous sulfate.

[0028] Preferably, the particle size of the breaker is 0.5 to 5 microns.

[0029] The present invention finds that the particle size range of the above-mentioned breaker can ensure that the breaker dissolves quickly and reacts fully with the components in the mud. The breaker reacts with the components in the mud to destroy the colloidal stability of the mud, making it easier to separate the solid components and liquid components in the mud.

[0030] Preferably, based on the mass of the first mixed slurry, the addition ratio of the breaker is 1-5wt%.

[0031] Preferably, in S3, the demulsification treatment comprises: mixing the first mixed slurry with a demulsifier at 60-90° C. to obtain a second mixed slurry;

[0032] Based on the mass of the second mixed slurry, the amount of the demulsifier is 0.1-2wt%.

[0033] In the specific implementation process, those skilled in the art can select a conventional demulsifier according to actual conditions, and no further limitation is made here.

[0034] The centrifugal separation process includes: centrifuging the second mixed slurry to separate a second oil-water mixture and a solid mixture.

[0035] The present invention finds that the emulsified state in the mud can be destroyed by adding a demulsifier, and the oil droplets in the emulsion will gather to form larger oil droplets, which are easier to separate from the water phase.

[0036] In the present invention, the solid mixture includes barite and soil; preferably, the method for treating waste drilling mud also includes: subjecting the solid mixture to screening and flotation separation in sequence to obtain refined barite and soil.

[0037] Preferably, the soil, chelating agent and curing agent are mixed for treatment.

[0038] More preferably, the chelating agent may be a common heavy metal chelating agent or a heavy metal scavenging agent, which is not further limited herein.

[0039] More preferably, the chelating agent is ethylenediaminetetraacetic acid (EDTA).

[0040] More preferably, the curing agent includes one or more of cement, lime, clay and organic polymer.

[0041] In the present invention, a curing agent and a chelating agent are used in combination, wherein the curing agent is added in an amount of about 5 to 10 ten-thousandths of the weight of the soil, and the chelating agent is added in an amount of about 2 ten-thousandths of the weight of the soil.

[0042] As a preferred embodiment of the present invention, the method for treating waste drilling mud comprises:

[0043] S0: pre-treating the waste drilling mud, wherein the pre-treatment includes: controlling the solid content of the waste drilling mud to be 10-15wt%, the oil content to be ≤2wt%, and the water content to be 85-90wt%;

[0044] S1: mixing the drilling waste mud with the additive to obtain a solid-liquid mixture;

[0045] S2: subjecting the solid-liquid mixture to filter pressing treatment to obtain a first oil-water mixture and oil sludge after filter pressing treatment;

[0046] S3: allowing the first oil-water mixture to stand and separate into layers, to obtain an upper layer of oil and a lower layer of high-salt water;

[0047] S4: mixing the upper layer oil with the oil sludge after the filter press treatment; heating and evaporating the high-salt water at 100-110° C. to obtain gaseous water vapor and solid salt; and then condensing the water vapor to obtain low-salt water;

[0048] S5: sequentially subjecting the oil sludge after the filter press treatment to degelling treatment, demulsification treatment and centrifugal separation treatment to obtain a second oil-water mixture and a solid mixture;

[0049] Preferably, the oil sludge after the filter press treatment is mixed with a demulsifier at 60-90° C. to react to obtain a first mixed slurry; then the first mixed slurry is mixed with a demulsifier at 60-90° C. to obtain a second mixed slurry; finally, the second mixed slurry is centrifuged and separated to obtain a second oil-water mixture and a solid mixture.

[0050] S6: The second oil-water mixture is allowed to stand for stratification to obtain an upper layer of oil and a lower layer of wastewater; the wastewater is introduced into S4 for heating, evaporation and condensation in sequence to obtain low-salt water.

[0051] S7: The solid mixture is screened and flotated to separate barite, and then washed and dried to obtain barite; at the same time, the soil, chelating agent and curing agent are mixed and treated; the curing agent includes one or more of cement, lime, clay and organic polymer.

[0052] In the present invention, the separated solid salt can be provided to industrial salt disposal manufacturers for recycling, and the waste oil can be directly recycled as hazardous waste by hazardous waste companies.

[0053] In the specific implementation process, those skilled in the art can, according to the actual situation, first perform harmless treatment on the oil sludge after the filter press before performing demulsification and other treatments. Specifically, cationic precipitants and anionic precipitants can be added in time according to the on-site treatment conditions, and the specific selection is not further limited here.

[0054] For example, cationic precipitant is an inorganic substance containing phosphate, which precipitates heavy metal ions, reduces their activity, and gives the solidified material a certain fertilizer effect; polyferric chloride is a common cationic water-based sedimentation agent, which has the advantages of rapid precipitation and obvious effect. Anionic precipitant can turn soluble anionic organic pollutants into insoluble substances, reduce their toxicity, and adjust the pH value of waste, while coordinating with cationic precipitant to break emulsions; anionic polyacrylamide sedimentation agent is a common anionic water-based sedimentation agent.

[0055] In the present invention, the existing conventional process can be selected for barite flotation, and the specific process includes the following steps:

[0056] 1. Crushing and grinding: First, the raw ore needs to be crushed and ground to break the ore particles into smaller particles for subsequent processing.

[0057] 2. Adding dressing agents: Then add corresponding dressing agents to the ore pulp after grinding. These dressing agents are often some chemical agents or surfactants (including collectors, foaming agents, and flocculants, etc.), which can make the surface of barite ore interact with water molecules to form foam.

[0058] 3. Bubble flotation: The slurry is then stirred and aerated in a bubbling flotation machine. Through the action of air bubbles, the ore particles such as barite combine with the bubbles and float on the surface of the slurry.

[0059] 4. Flotation separation: The barite ore particles in the foam are then collected and separated to obtain concentrate. The remaining pulp is further separated through defoaming agents, filtration, dehydration and other processes to obtain tailings.

[0060] 5. Concentrate purification: Finally, through the further processing of the concentrate, such as digestion, leaching, electrolysis and other methods, the metal elements in the barite can be extracted to obtain the final metal product.

[0061] In a second aspect, the present invention provides a system for treating waste drilling mud, comprising a filter press unit, an oil removal unit and a brine separation unit connected in sequence; and also comprising an oil mud treatment unit connected to the filter press unit;

[0062] The oil sludge processing unit comprises a de-gelling device, a de-emulsifying device, and a centrifugal separation device connected in sequence; and also comprises an oil-water separation device and a solid phase processing device respectively connected to the centrifugal separation device;

[0063] The filter press unit comprises a screw pump and a box-type diaphragm filter press; the filter press unit is used to perform preliminary separation of the solid and liquid phases in the drilling waste mud to obtain a first oil-water mixture and oil sludge after filter press treatment;

[0064] The oil removal unit is used to separate the high-salt water and oil in the first oil-water mixture after natural stratification;

[0065] The salt water separation unit is used to separate salt and water in the high-salt water; the salt water separation unit includes a heating evaporation device and a condensation device; the heating evaporation device is used to heat the high-salt water to obtain gas phase water vapor and solid phase salt; the condensation device is used to condense the gas phase water vapor in the high-salt water to obtain low-salt water;

[0066] The degumming device is used to degumming the oil sludge after the filter press treatment to obtain a first mixed slurry;

[0067] The demulsification device is used to demulsify the first mixed slurry to obtain a second mixed slurry;

[0068] The centrifugal separation device is used to centrifuge and separate the second mixed slurry to obtain a second oil-water mixture and a solid mixture;

[0069] The oil-water separation device is used to statically separate the second oil-water mixture into layers to obtain an upper layer of oil and a lower layer of low-salt water respectively;

[0070] The solid phase treatment device is used to recycle the barite and soil in the solid mixture respectively.

[0071] Preferably, the brine separation unit comprises a salt storage tank and a low-brine water storage tank, and the salt storage tank is connected to the solid phase processing device;

[0072] And / or, the oil removal unit comprises a high-salt water storage tank and an oil storage tank, and the oil storage tank is incorporated into the oil sludge treatment unit;

[0073] And / or, the oil-water separation device includes a wastewater storage tank and a waste oil storage tank, and the wastewater storage tank is incorporated into the brine separation unit.

[0074] In the present invention, the power and filter membrane size of the box-type diaphragm filter press can be selected according to actual conditions, such as the filter membrane size is 1.25×1.25m, and the power is 10-15kw.

[0075] In the present invention, due to the differences in density and physical properties, the oil and high-salt water in the oil removal unit will naturally separate into layers after settling for 2 to 3 hours, thereby obtaining the upper layer of oil and the lower layer of high-salt water.

[0076] Preferably, in the solid phase treatment device, the solid mixture is added to a screen having a mesh number of 325 to 425 to separate barite, and after water is added to the crushed ore grinding, a slurry is made, and added to a flotation tank, and then a collector, a frother and a flocculant are sequentially added. The slurry is then stirred and aerated in a bubbling flotation machine, and by the effect of air foam, ore particles such as barite are combined with foam, float on the surface of the slurry, and the barite ore particles in the foam are subsequently collected, separated, and concentrate is obtained. The washed barite is moved to a rotary dryer or a fluidized bed dryer to obtain clean refined barite particles.

[0077] The specific steps include:

[0078] (1) Sieving and separation: The solid mixture is placed on a 325-425 mesh sieve for sieving, and the difference in particle size between barite and soil is used for separation. 325-425 mesh means that the sieve has 325-425 holes per inch. This fineness ensures the most effective separation of barite.

[0079] (2) Flotation tank separation: The screened barite enters the flotation tank again. The refined barite will settle to the bottom of the flotation tank due to its higher specific gravity.

[0080] (3) Washing: After flotation, use hydrochloric acid of appropriate concentration to wash the settled refined barite to remove any impurities or residues on the refined barite and improve its purity. Hydrochloric acid is a strong acid that can effectively remove a variety of impurities;

[0081] (4) Drying: The acid-washed refined barite is then sent to a rotary dryer or a fluidized bed dryer for drying to ensure that dry refined barite particles are obtained.

[0082] Furthermore, the treated soil can be landfilled for reclamation.

[0083] In the present invention, solidification separation is a method of separating liquids and solids in contaminated soil. This treatment is mainly used to reduce the moisture content in the soil, thereby reducing the cost of treatment and disposal. Solidification treatment generally involves adding treatment agents to the soil to reduce the permeability of the soil and increase its structural stability, making it easier to landfill and reclaim.

[0084] The specific steps include:

[0085] (1) Select a solidifying agent and a chelating agent for joint treatment: Select appropriate solidifying agents and chelating agents according to the properties of the soil. Commonly used solidifying agents include cement, lime, clay, and organic polymers; mix the solidifying agent and chelating agent with the separated soil to ensure uniform mixing, which can be achieved by stirring, mechanical mixing or other methods.

[0086] (2) Landfill: The treated soil is transported to the landfill site and then landfilled according to landfill requirements;

[0087] (3) Reclamation: After landfill is completed, land reclamation can enable the contaminated soil to be effectively managed and utilized, thereby achieving sustainable land use.

[0088] In the present invention, the oil content and water content in the mud can be determined quickly and accurately by using the oil-in-water detector; the solid content tester: adopts microwave technology and is suitable for measuring the solid content in the mud.

[0089] Based on the above technical solution, the beneficial effects of the present invention are:

[0090] The present invention provides a method and system for treating the above-mentioned waste drilling mud. By optimizing the treatment process, it is possible to exchange lower resource input for higher resource utilization, and also combines the harmless treatment of mud with the treatment of high-salt water, so that the oil, water and solid phase (salt, soil and barite) in the waste drilling mud can be successfully separated and recovered, which not only realizes the reuse of resources but also greatly reduces environmental pollution. BRIEF DESCRIPTION OF THE DRAWINGS

[0091] In order to more clearly illustrate the technical solutions in the present invention or the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0092] Figure 1 This is a processing flow chart of waste drilling mud provided in Example 1 of the present invention. DETAILED DESCRIPTION

[0093] In order to make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention will be clearly and completely described below in conjunction with the drawings of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0094] Unless otherwise specified, the various raw materials used in the examples are commercially available conventional raw materials, and the technical means used are conventional means well known to those skilled in the art. Among them, the demulsifier was purchased from Xingrui (Shandong) Environmental Technology Co., Ltd., model SGR1721.

[0095] In the waste drilling mud of the following examples and comparative examples, the oil content is about 2wt% and the water content is about 90wt% as measured by the oil-in-water detector; the solid content is about 8wt% as measured by the solid content tester. The oil content in the first oil-water mixture is less than 2wt%.

[0096] Example 1

[0097] This embodiment first provides a system for treating waste drilling mud, comprising a filter press unit, an oil removal unit and a brine separation unit connected in sequence; and also comprising an oil mud treatment unit connected to the filter press unit;

[0098] The oil sludge processing unit comprises a de-gelling device, a de-emulsifying device, and a centrifugal separation device connected in sequence; and also comprises an oil-water separation device and a solid phase processing device respectively connected to the centrifugal separation device;

[0099] The filter press unit comprises a screw pump and a box-type diaphragm filter press; the filter press unit is used to perform preliminary separation of the solid and liquid phases in the drilling waste mud to obtain a first oil-water mixture and oil sludge after filter press treatment;

[0100] The oil removal unit is used to separate the high-salt water and oil in the first oil-water mixture after natural stratification;

[0101] The salt water separation unit is used to separate salt and water in the high-salt water; the salt water separation unit includes a heating evaporation device and a condensation device; the heating evaporation device is used to heat the high-salt water to obtain gas phase water vapor and solid phase salt; the condensation device is used to condense the gas phase water vapor in the high-salt water to obtain low-salt water;

[0102] The brine separation unit also includes a salt storage tank and a low-brine storage tank, and the salt storage tank is connected to the solid phase treatment device; the oil removal unit includes a high-brine storage tank and an oil storage tank, and the oil storage tank is incorporated into the sludge treatment unit. The oil-water separation device includes a wastewater storage tank and a waste oil storage tank, and the wastewater storage tank is incorporated into the brine separation unit.

[0103] The degumming device is used to degumming the oil sludge after the filter press treatment to obtain a first mixed slurry;

[0104] The demulsification device is used to demulsify the first mixed slurry to obtain a second mixed slurry;

[0105] The centrifugal separation device is used to centrifuge and separate the second mixed slurry to obtain a second oil-water mixture and a solid mixture;

[0106] The oil-water separation device is used to statically separate the second oil-water mixture into layers to obtain an upper layer of oil and a lower layer of low-salt water respectively;

[0107] The solid phase treatment device is used to recycle the barite and soil in the solid mixture respectively.

[0108] The size of the filter press membrane is 1.25m×1.25m, and the power of the box-type diaphragm filter press is 10~15kw.

[0109] This embodiment also provides a method for treating drilling waste mud using the above-mentioned treatment system, comprising the following steps:

[0110] S0: pre-treating the waste drilling mud, wherein the pre-treatment includes: controlling the solid content of the waste drilling mud to be 10-15wt%, the oil content to be ≤2wt%, and the water content to be 85-90wt%;

[0111] S1: Mixing the drilling waste mud with diatomaceous earth to obtain a solid-liquid mixture; the amount of the auxiliary agent is 3wt%.

[0112] S2: subjecting the solid-liquid mixture to filter press treatment to obtain a first oil-water mixture and oil sludge after filter press treatment, respectively; the oil content in the oil sludge is less than 2wt%;

[0113] S3: allowing the first oil-water mixture to stand and separate into layers, to obtain an upper layer of oil and a lower layer of high-salt water;

[0114] S4: Mixing the upper layer oil with the oil sludge after the filter press treatment; heating and evaporating the high-salt water at 110° C. to obtain gaseous water vapor and solid salt; then condensing the water vapor to obtain low-salt water; after testing, the TDS of the low-salt water is ≤1000 mg / L.

[0115] S5: sequentially subjecting the oil sludge after the filter press treatment to degelling treatment, demulsification treatment and centrifugal separation treatment to obtain a second oil-water mixture and a solid mixture;

[0116] Specifically, the oil sludge after the filter press treatment is mixed with ferrous sulfate at 70°C to react to obtain a first mixed slurry; then the first mixed slurry is mixed with a demulsifier at 60°C to obtain a second mixed slurry; finally, the second mixed slurry is centrifuged and separated to obtain a second oil-water mixture and a solid mixture.

[0117] Based on the mass of the first mixed slurry, the addition ratio of the demulsifier is 1wt%. Based on the mass of the second mixed slurry, the amount of the demulsifier is 0.1wt%.

[0118] S6: The second oil-water mixture is allowed to stand for stratification to obtain an upper layer of oil and a lower layer of wastewater; the wastewater is introduced into S4 for heating, evaporation and condensation in sequence to obtain low-salt water.

[0119] S7: Add the solid mixture to a sieve with a mesh size of 325 to separate the barite, and pass it into the flotation tank again to allow the barite to settle, and flotation separation is performed again. Hydrochloric acid of appropriate concentration is added to the flotation tank for washing, and the washed barite is moved to a rotary dryer or a fluidized bed dryer to obtain clean refined barite particles; at the same time, the soil, cement or fly ash and chelating agent are mixed for curing treatment. The dosage of the curing agent is about 5 to 10 ten thousandths of the weight of the soil, and the dosage of the chelating agent is about 2 ten thousandths of the weight of the soil.

[0120] See the processing flow chart Figure 1 .

[0121] In this embodiment, the treated soil is transported to a landfill site and then landfilled according to landfill requirements. After the landfill is completed, land reclamation is carried out, so that the contaminated soil can be effectively managed and utilized, thereby achieving sustainable land utilization.

[0122] Example 2

[0123] This embodiment provides a system and method for treating waste drilling mud, and the difference between the treatment method and the embodiment 1 is that the diatomaceous earth in S1 is replaced by an equal amount of bentonite. According to the test, the TDS of the lower layer of low-salt water obtained in S3 is about 1400 mg / L.

[0124] Example 3

[0125] This embodiment provides a system and method for treating waste drilling mud. The treatment method is different from that of Embodiment 1 only in that the solid content of the waste drilling mud is 15 wt %.

[0126] According to the test, the TDS of the lower salt water obtained in S3 is about 1100 mg / L.

[0127] Comparative Example 1

[0128] This comparative example provides a system and method for treating waste drilling mud, and the treatment method thereof is different from that of Example 1 only in that S1 is not included.

[0129] According to the test, the TDS of the lower salt water obtained in S3 is about 2100 mg / L.

[0130] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for treating waste drilling mud, characterized in that: include: S1: mixing the drilling waste mud with an additive to obtain a solid-liquid mixture; the additive is diatomaceous earth; In the solid-liquid mixture, the amount of the auxiliary agent is 2-5wt%; S2: subjecting the solid-liquid mixture to filter press treatment to obtain a first oil-water mixture and oil sludge after filter press treatment, respectively; the oil sludge after filter press treatment has a solid content of 50-60wt%; S3: allowing the first oil-water mixture to stand and separate into layers, to obtain an upper layer of oil and a lower layer of high-salt water; S4: mixing the upper layer oil with the oil sludge after the filter press treatment; heating and evaporating the high-salt water at 100-110° C. to obtain gaseous water vapor and solid salt; and then condensing the water vapor to obtain low-salt water; S5: sequentially subjecting the oil sludge after the filter press treatment to degelling treatment, demulsification treatment and centrifugal separation treatment to obtain a second oil-water mixture and a solid mixture; S6: placing the second oil-water mixture aside for stratification to obtain an upper layer of oil and a lower layer of wastewater, respectively, and introducing the wastewater into S4 for heating, evaporation and condensation in sequence to obtain the low-salt water; Before S1, the waste drilling mud is pretreated, and the pretreatment includes: controlling the solid content of the waste drilling mud to be 10-15wt%, the oil content ≤2wt%, wherein the oil content is not 0, and the water content is 85-90wt%.

2. The method for treating waste drilling mud according to claim 1, characterized in that: In S5, the degumming treatment includes: mixing the oil sludge after the filter press treatment with a degumming agent at 60-90° C. to react to obtain a first mixed slurry; The breaker includes calcium oxide and / or ferrous sulfate; the particle size of the breaker is 0.5-5 microns; based on the mass of the first mixed slurry, the addition ratio of the breaker is 1-5wt%.

3. The method for treating waste drilling mud according to claim 2, characterized in that: In S5, the demulsification treatment includes: mixing the first mixed slurry with a demulsifier at 60-90° C. to obtain a second mixed slurry; Based on the mass of the second mixed slurry, the amount of the demulsifier is 0.1-2wt%; The centrifugal separation process includes: centrifuging the second mixed slurry to separate a second oil-water mixture and a solid mixture.

4. The method for treating waste drilling mud according to claim 1, characterized in that: The solid mixture includes barite and soil; the solid mixture is sequentially separated by screening and flotation to obtain refined barite and soil.

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