A system and method for harmless and recycling treatment of waste drilling fluid

Abstract

The application discloses a harmless and recycling treatment system and method for waste drilling fluid, and relates to the technical field of waste drilling fluid treatment, and comprises the following steps: S1, calcium-free demulsification dehydration: adding a demulsifying agent combination to waste drilling fluid filter pressing liquid, wherein the demulsifying agent combination comprises 1.3-1.7 g / L of diatomite, 0.08-0.12 mol / L of NaOH, 0.25-0.35 g / L of FeCl3 and 8-12 mg / L of PAM, and mud-water separation is performed. Through the first treatment process of CaSO4 destabilization crystallization and Na2CO3 cooperative softening, the calcium ion removal rate is increased to 97.3%, the magnesium ion removal rate reaches 72.5%, the calcium ion is further reduced to 62 mg / L after the NF membrane secondary treatment, and the NF membrane water hardness requirement and the final recycling standard are comprehensively met.

Description

Technical Field

[0001] This invention relates to the field of waste drilling fluid treatment technology, specifically to a system and method for the harmless treatment and reuse of waste drilling fluid. Background Technology

[0002] In the oilfield development sector, the direct discharge of waste drilling fluid generated during drilling operations without proper treatment can cause serious pollution to water bodies, soil, and groundwater systems. Drilling hydraulic fluid contains a large amount of suspended solids, high-valence anions and cations, recalcitrant organic matter, and heavy metals. Among existing technologies at home and abroad, the mainstream treatment method is solid-liquid separation, such as chemically enhanced solid-liquid separation technology and coagulation sedimentation. However, the separated water is not deeply treated and still needs to be transported to a centralized treatment station, which is costly and inefficient. Some on-site treatment methods in China are crude, with waste mud being transported directly to brick factories without treatment or with only simple treatment, or flocculation sedimentation mud-water separation and pressure filtration technology being used, but without deep treatment of the pressure filtrate, resulting in resource waste and environmental pollution. The lack of unified standards for the reuse of pressure filtrate restricts the development of resource utilization.

[0003] The existing shortcomings in the harmless treatment of waste drilling fluid are:

[0004] 1. Patent document CN104944480A discloses a waste drilling fluid harmless treatment agent. "This invention relates to a waste drilling fluid harmless treatment agent. It mainly solves the problem that existing 'solidification' treatment methods for waste drilling fluid cannot fundamentally remove harmful substances, easily causing secondary pollution. The components and proportions of this waste drilling fluid harmless treatment agent by weight percentage are as follows: pH adjuster 1.0%–1.5%, heavy metal remover 0.7–1.0%, oxide remover 2.0–2.5%, flocculant 1.5–2.0%, coagulant aid 0.05%–0.1%, decolorizing agent 2.0%–2.5%. The liquid phase of the product after treatment with this waste drilling fluid harmless treatment agent can be used for oilfield reinjection water, and the solid phase can be used for paving well sites and maintaining well-drainage roads, realizing the resource reuse of waste." However, the device described in the above document suffers from the technical problem of using chemical precipitation methods, resulting in low calcium ion removal rates.

[0005] 2. Patent document CN108316873B discloses a water-based drilling waste harmless treatment device, method, and application. "This invention provides a water-based drilling waste harmless treatment device, method, and application. The water-based drilling waste harmless treatment device includes a non-landing collection unit, a liquid-phase regeneration treatment unit, and a solid-phase harmless treatment unit; the non-landing collection unit is connected to both the liquid-phase regeneration treatment unit and the solid-phase harmless treatment unit; the liquid-phase regeneration treatment unit is connected to the solid-phase harmless treatment unit." The water-based drilling waste harmless treatment device and method of the present invention saves land and treatment costs, and saves costs such as drilling waste harmless treatment, landfill excavation and seepage prevention; the pH, COD, color and petroleum content of the base soil and non-fired block leachate prepared after the drilling waste harmless treatment meet environmental protection requirements, and the non-fired blocks and base soil meet relevant building material standards, realizing the recycling and resource utilization of drilling waste. However, the device in the above document has the technical problem that the filtrate is difficult to reuse, resulting in water waste.

[0006] 3. Patent document CN108640218A discloses a method and application for solid-liquid separation treatment of waste drilling fluid. "This invention relates to a method and application for solid-liquid separation treatment of waste drilling fluid. The technical solution includes three steps: ultrasonic treatment, centrifugation of the waste drilling fluid, and solid-liquid phase separation. The ultrasonic treatment time is 15 min to 60 min, and the ultrasonic treatment frequency is 18 kHz to 25 kHz; the centrifugation time is 10 min to 60 min, and the centrifugation speed is 2000 r / min to 4000 r / min." The method for solid-liquid phase separation of waste drilling fluid is to separate the waste drilling fluid after centrifugation. The beneficial effects of this invention are: compared with conventional plate and frame filter presses, high-speed centrifugation, and other drilling fluid solid-liquid separation methods, the waste drilling fluid solid-liquid separation treatment method provided by this invention uses ultrasonic treatment, waste drilling fluid centrifugation, and solid-liquid phase separation. The treatment process is simple, highly operable, and has low treatment costs, making it particularly suitable for the harmless treatment and resource utilization of waste drilling fluid during oil and gas exploration and development. However, the device described in the above document has a technical problem of low heavy metal removal rate. Summary of the Invention

[0007] The purpose of this invention is to provide a system and method for the harmless treatment and reuse of waste drilling fluid, so as to solve the technical problems mentioned in the background art.

[0008] To achieve the above objectives, the present invention provides the following technical solution: a method for the harmless treatment and reuse of waste drilling fluid, comprising the following steps;

[0009] S1. Demulsification and dehydration without calcification: A demulsifying agent combination is added to the waste drilling hydraulic fluid, the demulsifying agent combination comprising 1.3-1.7 g / L diatomaceous earth, 0.08-0.12 mol / L NaOH, 0.25-0.35 g / L FeCl3 and 8-12 mg / L PAM, to separate mud and water;

[0010] S2, Primary nucleation granulation for calcium and magnesium removal: The filtrate obtained in step S1 is fed into the primary nucleation granulation device, 80-120 g / L of CaSO4 is added and the pH is adjusted to 8.5-9.5. After reacting for 2-24 hours, 0.8-1.2 mol / L of Na2CO3 and 0.15-0.25 mol / L of NaOH are added, and the reaction time is 1-3 hours.

[0011] S3, Secondary nucleation granulation for heavy metal removal: The filtrate after step S2 is fed into the secondary nucleation granulation device, 1.2-1.8 mmol / L of Na2S is added and the pH is adjusted to 9.0-10.0. The reaction time is 20-40 minutes.

[0012] S4. Deep filtration: The filtrate after step S3 is sequentially passed through multi-media filtration, activated carbon filtration and nanofiltration (NF) membrane module, wherein the NF membrane operates at a pressure of 1.2-1.8 MPa, so that the filtrate water quality meets the reuse standard.

[0013] S5. Reuse: The produced water obtained in step S4 is reused for drilling mud preparation, and the concentrate is discharged for disposal.

[0014] Preferably, the demulsifying agent combination in step S1 is 1.5 g / L diatomaceous earth, 0.10 mol / L NaOH, 0.3 g / L FeCl3 and 10 mg / L PAM.

[0015] Preferably, in step S2, the amount of CaSO4 added is 100 g / L, pH=9, and after reacting for 24 hours, 1.0 mol / L Na2CO3 and 0.2 mol / L NaOH are added and reacted for 2 hours.

[0016] Preferably, in step S3, the amount of Na2S added is 1.5 mmol / L, the pH is 9.5, and the reaction time is 30 minutes.

[0017] Preferably, in step S4, the NF membrane's rejection rate for divalent ions satisfies: Ca 2+ Retention rate ≥65%, SO4 2- Retention rate ≥ 90%.

[0018] Preferably, the water quality of the recycled product water in step S5 meets the following requirements: Ca 2+ ≤180mg / L, Mg 2+≤108mg / L, Zn 2+ ≤0.130mg / L, Mn 2+ ≤0.3mg / L, SO4 2- ≤250mg / L, suspended solids ≤10mg / L, chemical oxygen demand (COD) ≤100mg / L, petroleum hydrocarbons ≤0.5mg / L, pH 6-9, total nitrogen ≤200mg / L, Fe 3+ ≤0.5mg / L, NO3 - ≤10mg / L.

[0019] Preferably, the following modular units are integrated within the container:

[0020] A non-calcified demulsification unit is equipped with a demulsification agent dosing device;

[0021] The series-connected primary and secondary nucleation granulation units are equipped with:

[0022] Primary nucleation granulation unit: CaSO4, Na2CO3, NaOH dosing system and pH adjustment device;

[0023] Secondary nucleation granulation unit: Na2S dosing system and pH adjustment device;

[0024] The depth filtration unit comprises, in sequence, a multi-media filter, an activated carbon filter, and an NF membrane module;

[0025] The system includes a recycled water tank and a concentrate collection tank, with the inlet of the recycled water tank connected to the permeate outlet of the NF membrane module and the inlet of the concentrate collection tank connected to the concentrate outlet of the NF membrane module.

[0026] Preferably, the primary nucleation granulation unit is equipped with an online pH monitor and an automatic control system linked to the CaSO4, Na2CO3, and NaOH dosing pumps;

[0027] The secondary nucleogranulation unit is equipped with an ORP sensor and an automatic Na2S dosing control system.

[0028] Preferably, the NF membrane module is equipped with an operating pressure control system and a membrane fouling monitor, and the operating pressure control system and the membrane fouling monitor are interlocked.

[0029] Compared with the prior art, the beneficial effects of the present invention are:

[0030] 1. This invention employs a primary treatment process combining CaSO4 destabilization crystallization and Na2CO3 synergistic softening, which increases the calcium ion removal rate to 97.3% and the magnesium ion removal rate to 72.5%. After secondary treatment by the NF membrane, the calcium ion concentration is further reduced to 62 mg / L, fully meeting the NF membrane influent hardness requirements and final reuse standards.

[0031] 2. This invention innovatively introduces Na2S co-precipitation technology through a two-stage nucleation granulation process, breaking through the bottleneck of traditional heavy metal treatment: Zn 2+ Removal rate reached 98.5%, Mn 2+ The removal rate was 91.9%, and the concentrations after treatment were as low as 0.05 mg / L and 0.12 mg / L, respectively.

[0032] 3. This invention achieves efficient retention of organic matter and suspended solids through a three-stage technology combining multi-media filtration, activated carbon adsorption, and NF membrane: COD is reduced from 85 mg / L to 42 mg / L, SS is reduced from 243 mg / L to 5.2 mg / L, and turbidity removal rate reaches 56.3%. The final effluent quality fully meets the requirements for mud preparation. Furthermore, through graded treatment and synergistic effect mechanism, the feasibility of resource recycling of complex wastewater is significantly improved.

[0033] 4. This invention allows for the direct use of monovalent salts such as NaCl and KCl retained in the filtrate for pulp preparation, which helps save on reagent costs;

[0034] 5. This invention improves mobility and compatibility by integrating modular units into a container to meet the relocation needs of drilling platforms. Attached Figure Description

[0035] Figure 1 This is a schematic diagram of the processing method of the present invention;

[0036] Figure 2 This is a schematic diagram of the system flow of the present invention.

[0037] In the diagram: 1. Demulsification unit without calcification; 2. Primary nucleation granulation unit; 3. Secondary nucleation granulation unit; 4. Depth filtration unit; 5. Multi-media filter; 6. Activated carbon filter; 7. NF membrane module; 8. Reclaimed water tank; 9. Concentrate collection tank. Detailed Implementation

[0038] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0039] Example 1: Please refer to Figure 1 and Figure 2 One embodiment provided by the present invention:

[0040] The container includes the following modular units: a non-calcified demulsification unit 1, equipped with a demulsification agent dosing device; a primary nucleation granulation unit 2 and a secondary nucleation granulation unit 3 connected in series, each equipped with: a CaSO4, Na2CO3, and NaOH dosing system and a pH adjustment device for the primary nucleation granulation unit 2; a Na2S dosing system and a pH adjustment device for the secondary nucleation granulation unit 3; a depth filtration unit 4, which sequentially includes a multi-media filter 5, an activated carbon filter 6, and an NF membrane module 7; a reclaimed water tank 8 and a concentrate collection tank 9, with the inlet of the reclaimed water tank 8 connected to the permeate outlet of the NF membrane module 7, and the inlet of the concentrate collection tank 9 connected to the concentrate outlet of the NF membrane module 7; the primary nucleation granulation unit 2 is equipped with an online pH monitor and an automatic control system linked to the CaSO4, Na2CO3, and NaOH dosing pumps; the secondary nucleation granulation unit 3 is equipped with an ORP sensor and an automatic Na2S dosing control system; and the NF membrane module 7 is equipped with an operating pressure control system and a membrane fouling monitor, with the operating pressure control system and the membrane fouling monitor interlocked.

[0041] Experiment 1: Add a demulsifying agent combination to the waste drilling hydraulic fluid. The demulsifying agent combination consists of 1.5 g / L diatomaceous earth, 0.10 mol / L NaOH, 0.3 g / L FeCl3 and 10 mg / L PAM.

[0042] Furthermore, by adding demulsifiers to disrupt the emulsified state of the filtrate, the separation of oil, water, and sludge is promoted, causing suspended solids and colloidal particles to coagulate and settle.

[0043] Experiment 2: Primary nucleus crystal granulation for calcium removal and softening:

[0044] Dosage conditions: 100 g / L CaSO4, 1.0 mol / L Na2CO3 and 0.2 mol / L NaOH;

[0045] Reaction parameters: pH=9.0±0.2, stirring speed 300 rpm, reaction time 2 hours;

[0046] Table 1. Effects of Primary Nucleus Granulation Process

[0047]

[0048] Furthermore, as can be seen from the table above, the application of the nucleation granulation device, combined with the destabilization and crystallization of CaSO4 and the synergistic softening by Na2CO3 and NaOH, significantly reduces the calcium and magnesium concentrations. 2+ Removal rate > 97%, Mg 2+ Removal rate 72.5%, residual concentration 22 mg / L

[0049] Experiment 3: Secondary nucleus crystallization for heavy metal removal: Dosage conditions: 1.5 mmol / L Na₂S, pH adjusted to 9.5 ± 0.2, reaction parameters: stirring speed 200 rpm, reaction time 30 minutes.

[0050] Table 2. Effects of Secondary Nucleus Granulation Treatment

[0051]

[0052] Furthermore, the data in the table shows that the Na2S precipitation method has a significant effect on the removal of heavy metals, Zn 2+ Fe 3+ Removal rates were all >98%, Mn 2+ Removal rate > 91%.

[0053] Experiment 4: Verify whether the filtrate pretreated by the nucleation granulation device, after being treated by the depth filtration unit 4, can meet the "Filtrate Reuse Standard":

[0054] Pretreated water quality: Ca in the effluent from the nucleogranulation unit 2+ 195 mg / L, Mg 2+ 22 mg / L, Zn 2+ 0.28 mg / L, Fe 3+ 0.04 mg / L, Mn 2+ 0.35 mg / L, pH: 9.4;

[0055] The depth filtering unit 4 comprises:

[0056] Multi-media filter 5: Quartz sand + anthracite, filtration accuracy of 10μm, flow rate of 2m³ / h.

[0057] Activated carbon filter 6: coconut shell activated carbon, particle size 1.5mm, adsorption time 30min.

[0058] NF membrane module 7: polyamide composite membrane with a molecular weight cutoff of 200 Da and an operating pressure of 1.5 MPa.

[0059] Experimental procedure: Nuclear crystal granulation effluent → Multi-media filter 5 → Activated carbon filter 6 → NF membrane → Detection of final effluent.

[0060] According to the "Standard for Reuse of Filtrate", the following indicators are tested:

[0061] Common indicators: pH, suspended solids (SS), chemical oxygen demand (COD), petroleum hydrocarbons, ammonia nitrogen, and total salt content;

[0062] Ions: Ca 2+ Mg 2+ K + Na+ Cl - SO4 2- NO3 - ;

[0063] Heavy metals: Al 3+ Zn 2+ Mn 2+ Fe 3+ Total phosphorus;

[0064] Other: Total nitrogen, turbidity;

[0065] The water quality standards for reused wastewater must meet the following: Ca 2+ ≤180mg / L, Mg 2+ ≤108mg / L, Zn 2+ ≤0.130mg / L, Mn 2+ ≤0.3mg / L, SO4 2- ≤250mg / L, Suspended solids (SS) ≤10mg / L, Chemical oxygen demand (COD) ≤100mg / L, Petroleum hydrocarbons ≤0.5mg / L, pH 6-9, Total nitrogen ≤200mg / L, Fe 3+ ≤0.5mg / L, NO3 - ≤10mg / L.

[0066] Table 3. Treatment Effect of Multi-Media Filter

[0067]

[0068] Furthermore, multi-media filtration effectively reduces suspended solids, meeting reuse standards.

[0069] Table 4. Treatment effect of activated carbon filter

[0070]

[0071] Furthermore, activated carbon adsorption significantly reduces COD and petroleum hydrocarbons, meeting reuse standards.

[0072] Table 5. Effect of NF membrane treatment

[0073]

[0074] Furthermore, the NF membrane's rejection rate for divalent ions: Ca 2+ (68.2%), Mg 2+ (18.2%), SO4 2- (90.8%)

[0075] Heavy metal removal rate: Zn 2+ (82.1%), Mn 2+ (65.7%)

[0076] pH adjustment: Concentration of the NF membrane leads to a decrease in pH, but it remains within the standard range.

[0077] Working principle: The high-efficiency removal of calcium and magnesium ions employs a CaSO4 destabilization crystallization + Na2CO3 synergistic softening process, increasing the calcium ion removal rate to 97.3% and the magnesium ion removal rate to 72.5%, fully meeting the hardness requirements of the NF membrane feed water. After the first-stage nucleation granulation, the calcium concentration drops to 195 mg / L, and after further treatment by the NF membrane, it further decreases to 62 mg / L, far below the reuse standard. The second-stage nucleation granulation uses a Na2S synergistic precipitation process, breaking through the traditional technical bottleneck of Zn removal. 2+ Removal rate 98.5%, post-treatment concentration 0.05 mg / L, Mn 2+ The removal rate was 91.9%, and the concentration after treatment was 0.12 mg / L. All heavy metal indicators were superior to those in GB / T. The 19923-2005 Industrial Reclaimed Water Standard, combined with multi-media filtration, activated carbon adsorption, and NF membrane, reduced COD from 85 mg / L to 42 mg / L, suspended solids (SS) from 243 mg / L to 5.2 mg / L, and turbidity removal rate to 56.3%. The water quality meets the requirements for mud preparation. Monovalent salts such as NaCl and KCl retained in the recycled filtrate can be directly used for mud preparation, which helps save on chemical costs. The modular container skid design reduces relocation costs. Wastewater discharge is reduced by 80%, and heavy metal and COD emissions are also reduced, avoiding the risk of water, soil, and groundwater pollution. The non-calcification dewatering process avoids the introduction of additional calcium ions by traditional CaO demulsifiers, reducing the well leakage accident rate caused by mud denaturation from the source. Furthermore, 80% of the filtrate is recycled for mud preparation, which can save a lot of water resources and simultaneously recover salts such as NaCl and KCl, realizing a closed-loop utilization of "wastewater → resources".

[0078] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the present invention. No reference numerals in the claims should be construed as limiting the scope of the claims.

Claims

1. A method for the harmless treatment and reuse of waste drilling fluid, characterized in that: Includes the following steps; S1. Demulsification and dehydration without calcification: A demulsifying agent combination is added to the waste drilling hydraulic fluid, the demulsifying agent combination comprising 1.3-1.7 g / L diatomaceous earth, 0.08-0.12 mol / L NaOH, 0.25-0.35 g / L FeCl3 and 8-12 mg / L PAM, to separate mud and water; S2, Primary nucleation granulation for calcium and magnesium removal: The filtrate obtained in step S1 is fed into the primary nucleation granulation device, 80-120 g / L of CaSO4 is added and the pH is adjusted to 8.5-9.

5. After reacting for 2-24 hours, 0.8-1.2 mol / L of Na2CO3 and 0.15-0.25 mol / L of NaOH are added, and the reaction time is 1-3 hours. S3, Secondary nucleation granulation for heavy metal removal: The filtrate after step S2 is fed into the secondary nucleation granulation device, 1.2-1.8 mmol / L of Na2S is added and the pH is adjusted to 9.0-10.

0. The reaction time is 20-40 minutes. S4. Deep filtration: The filtrate after step S3 is sequentially passed through multi-media filtration, activated carbon filtration and nanofiltration (NF) membrane module, wherein the NF membrane operates at a pressure of 1.2-1.8 MPa, so that the filtrate water quality meets the reuse standard. S5. Reuse: The produced water obtained in step S4 is reused for drilling mud preparation, and the concentrate is discharged for disposal. The demulsifying agent combination in step S1 is 1.5 g / L diatomaceous earth, 0.10 mol / L NaOH, 0.3 g / L FeCl3 and 10 mg / L PAM; In step S2, the amount of CaSO4 added is 100 g / L, pH=9, and after reacting for 24 hours, 1.0 mol / L Na2CO3 and 0.2 mol / L NaOH are added and reacted for 2 hours. In step S3, the Na2S dosage is 1.5 mmol / L, pH=9.5, and the reaction time is 30 minutes. In step S4, the NF membrane's retention rate for divalent ions satisfies: Ca 2+ Retention rate ≥65%, SO4 2- Retention rate ≥ 90%; The water quality of the recycled product water in step S5 meets the following requirement: Ca 2+ ≤180mg / L, Mg 2+ ≤108mg / L, Zn 2+ ≤0.130mg / L, Mn 2+ ≤0.3mg / L, SO4 2- ≤250mg / L, suspended solids ≤10mg / L, chemical oxygen demand (COD) ≤100mg / L, petroleum hydrocarbons ≤0.5mg / L, pH 6-9, total nitrogen ≤200mg / L, Fe 3+ ≤0.5mg / L, NO3 - ≤10mg / L.

2. A waste drilling fluid harmless treatment and reuse system, applicable to the waste drilling fluid harmless treatment and reuse method described in claim 1, characterized in that, This includes the following modular units integrated into the container: A non-calcified demulsification unit (1) is equipped with a demulsification agent dosing device; The primary nucleation granulation unit (2) and the secondary nucleation granulation unit (3) connected in series are respectively equipped with: Primary nucleogranulation unit (2): CaSO4, Na2CO3, NaOH dosing system and pH adjustment device; Secondary nucleogranulation unit (3): Na2S dosing system and pH adjustment device; The depth filtration unit (4) comprises, in sequence, a multi-media filter (5), an activated carbon filter (6), and an NF membrane module (7); The recycled water tank (8) and the concentrate collection tank (9) are connected, with the inlet of the recycled water tank (8) connected to the permeate outlet of the NF membrane module (7) and the inlet of the concentrate collection tank (9) connected to the concentrate outlet of the NF membrane module (7).

3. The waste drilling fluid harmless treatment and reuse system according to claim 2, characterized in that: The primary nucleogranulation unit (2) is equipped with an online pH monitor and an automatic control system linked to the CaSO4, Na2CO3, and NaOH dosing pumps; The secondary nucleogranulation unit (3) is equipped with an ORP sensor and an automatic Na2S dosing control system.

4. The waste drilling fluid harmless treatment and reuse system according to claim 2, characterized in that: The NF membrane module (7) is equipped with an operating pressure control system and a membrane fouling monitor, and the operating pressure control system and the membrane fouling monitor are interlocked.

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