CN102139971A - Method and process for advanced treatment of well drilling effluent - Google Patents

Abstract

The invention relates to a method and process for advanced treatment of drilling waste liquid. The advanced treatment method and process of drilling waste fluid of the present invention include chemically enhanced solid-liquid separation, mechanical dehydration, advanced oxidation technology treatment and other processes. First, add 2-16g/L polyaluminum chloride to the drilling waste fluid, stir quickly and evenly, then add 50-200mg/L cationic polyacrylamide, stir at a low speed for 10-15min, destabilize and coalesce the drilling waste fluid, Dehydrate by centrifugation. Then, the advanced oxidation advanced treatment is carried out on the drilling waste fluid after the solid separation, and the pH value of the drilling wastewater is adjusted to 4. Hydrogen peroxide and ammonium persulfate are used as composite oxidants, and ferrous sulfate is used as a catalyst. Under the conditions of sunlight or simulated sunlight, React for 120-150 minutes, adjust the pH value of the drilling waste fluid to 8-9 with milk of lime, discharge or perform other treatments after clarification. The method can greatly reduce the indicators of suspended solids, chroma and COD _Cr of drilling waste fluid, and has a good application prospect.

Description

A method and process for advanced treatment of drilling waste fluid

technical field

The invention relates to the technical field of oil and gas field environmental protection.

Background technique

Drilling waste fluid mainly refers to the waste drilling fluid discharged during the oil drilling process and the waste fluid composed of cleaning fluid, well fluid, and sewage (formed by rainwater flushing the well site with some mud and oily substances) of various operating equipment, etc. Among them, waste drilling fluid is the main part. The main pollution characteristics are high COD _Cr , high chroma, high suspended solid content and easy dispersion in water.

A variety of chemical treatment agents and surfactants are added to the waste drilling fluid. Its composition is relatively complex, and generally contains heavy metals, oils, bentonite, alkalis and compounds (including organic matter) that are harmful to humans, animals and the environment. Such as iron chromium salt, sulfonated asphalt, sulfonated tannin extract, sulfonated lignite, etc., can greatly cause environmental pollution around the drilling site and cannot be discharged directly.

At present, the methods for treating drilling waste fluid (including solid waste such as drilling cuttings) mainly include: direct discharge, reinjection, landfill, composting, land cultivation, stabilization/solidification, thermal desorption, and incineration. Direct discharge is only applicable to non-toxic drilling waste fluid. Direct discharge of oily or non-water-based drilling waste fluid and cuttings is absolutely prohibited. The reinjection method can only eliminate the impact on the surface environment or seabed water body, and the polluting components such as oil, salt and heavy metals have not been treated, and if there is a spill, secondary pollution will occur. The landfill method only eliminates the pollution of the drilling site, the pollutants have not been treated, the leachate is more harmful to the groundwater, and there are other factors such as the landfill site, land cultivation and composting reduce the concentration of salt and heavy metal components. Concentration, petroleum and some organic compounds are biodegradable, but it is easy to cause pollution of the surface water environment, and also has an impact on the shallow underground water; if it needs to be cleaned in the future, the volume of the treated waste will increase, and there will be different degrees of air pollution. Stabilization/curing treatment Contaminated components are stabilized, and the leachate of solidified matter can pass the current test. After treatment, the volume increases, and salt and petroleum can reduce the solidification effect and may leach out. Thermal desorption and incineration are mostly used to treat drilling waste produced by oil-based drilling fluids, which consume a lot of energy, and acid compounds corrode equipment at high temperatures and cause air pollution to varying degrees.

The above methods all have deficiencies in different aspects and degrees, so a combined technology treatment process for the treatment of drilling waste fluid is proposed, mainly a physical and chemical treatment process based on coagulation, which adds a chemical coagulant to the drilling waste fluid After treatment with flocculant, the wastewater produced after treatment still has parameters such as COD _Cr and suspended solids exceeding the standard. The coagulation-advanced oxidation treatment process of drilling waste fluid is a combined treatment process developed in recent years, and the advanced oxidation treatment methods mainly include Fenton reagent catalytic oxidation, ozone _O3 oxidation, wet catalytic oxidation, etc. Wet oxidation requires high temperature and pressure conditions, and requires high equipment and other equipment, which is not easy to realize. Ozone _O3 oxidation has a good oxidation effect under alkaline conditions, but it requires a load on the results of the reaction equipment and a stable quality of the influent water; however, the composition of the waste liquid at the drilling site is variable, and the water quality varies greatly, so it is not easy to apply at the drilling site. Fenton's reagent catalytic oxidation has high oxidation treatment capacity, is a treatment method of homogeneous catalytic oxidation, and also has the characteristics of coagulation with pollutants during the oxidation process, and has low requirements for reaction equipment. In order to improve the treatment effect of Fenton reagent catalytic oxidation, photo-Fenton, electric-Fenton, ultrasonic-Fenton and other advanced oxidation treatment technologies have been proposed successively. Pollutants, and improve the biodegradability of wastewater, but the popularization and application of these technologies are still limited.

Persulfate is a common oxidizing agent. The sulfuric acid radical (SO ₄ ^- ·) generated after its splitting has a higher oxidation-reduction potential than the hydroxyl radical (·OH) under certain conditions, and most organic compounds can be completely degraded by it. The decomposition temperature of persulfate itself is 70-100°C. This requirement for external heat is limited by certain conditions in the drilling field trial. In addition, ultraviolet rays, Co ₆₀ can be used to generate γ-rays, and transition metal ions (Co ²⁺ , Cu ²⁺ , Fe ²⁺ and Ag ⁺ ) in aqueous solution can catalyze the decomposition of persulfate. The persulfate oxidation technology based on sulfuric acid radicals is limited by the cost of persulfate and other aspects.

Contents of the invention

The purpose of the present invention is to provide a coagulation-advanced oxidation combination technology with fast processing speed and good water quality for oil drilling waste fluid. Using this method can greatly improve the treatment effect of drilling waste fluid and make it discharge up to standard.

The treatment method of the present invention consists of several parts such as destabilization-flocculation, solid-liquid separation, and advanced oxidation. The specific method is: add an aqueous solution of an inorganic coagulant and an organic coagulant to the drilling waste liquid in sequence, and after stirring at a high speed, Stir for 10-15 minutes, centrifuge and dehydrate the drilling waste fluid with chemically enhanced solid-liquid separation, and select the centrifuge speed at 2600-3400 rpm; adjust the pH value to 4 in the separated coagulation effluent, and add hydrogen peroxide in turn (30%), persulfate and ferrous sulfate, placed under the radiation of sunlight or simulated sunlight, reacted for 120-150 minutes, and adjusted the pH value to 8-9 with 10% milk of lime.

The coagulation process in the present invention provides a new type of inorganic coagulant and organic coagulant.

The above-mentioned inorganic coagulant is composed of one or more of aluminum sulfate, ferric sulfate, aluminum chloride, ferric chloride, calcium chloride, calcium hydroxide, polyaluminum chloride and polyferric sulfate. Preferably, the inorganic coagulant is polyaluminum chloride, and its concentration is 2-16 g/L.

The above-mentioned organic flocculant is composed of one or two of nonionic polyacrylamide, anionic polyacrylamide and cationic polyacrylamide. Preferably, the organic flocculant is cationic polyacrylamide, its molecular weight is greater than 1000W, its cationic degree is 15%, and its dosage is 50-200 mg/L.

The chemically enhanced solid-liquid separation process described in the present invention uses inorganic coagulant polyaluminium chloride and organic flocculant cationic polyacrylamide in combination, and the suspended solid particles in the drilling waste fluid become negatively charged through charge neutralization, coagulation and large The coalescence of molecular bridging and adsorption forms large flocs, which can be centrifuged and dehydrated, and the separated water can be reused, such as configuring and maintaining drilling fluid, cleaning drilling tools, etc.

Generally, the indicators of chroma, suspended solids, and COD in the separated water have been significantly improved before treatment. However, for environmentally sensitive areas and areas with high environmental protection requirements, the separated effluent with indicators such as chroma and COD in the water is still lower than the discharge standard needs further treatment. in-depth processing.

In the present invention, the advanced oxidation technology is adopted to carry out advanced treatment on the water separated from the drilling waste fluid. The specific method is: adjust the pH value of the separated water from the drilling waste liquid to 4, then add an oxidant and a catalyst to the water respectively, and place it under ultraviolet-visible light. After reacting for a period of time, adjust the pH value to 8-9 with alkali, terminate the reaction, discharge or enter the subsequent treatment process.

The above advanced oxidation treatment processes include H ₂ O ₂ /Fe ²⁺ , H ₂ O ₂ /Fe ²⁺ -complexing agent, UV-Vis/H ₂ O ₂ /Fe ²⁺ , UV-Vis/H ₂ O ₂ / Fe ²⁺ -complexing agent, H ₂ O ₂ /S ₂ O ₈ ^2- /Fe ²⁺ or H ₂ O ₂ /HSO ₅ ^- /Fe ²⁺ , UV-Vis/H ₂ O ₂ /S ₂ O ₈ One or more of ^2- /Fe ²⁺ or UV-Vis/H ₂ O ₂ /HSO ₅ ^- /Fe ²⁺ . The preferred advanced oxidation processes are UV-Vis/H ₂ O ₂ /S ₂ O ₈ ²⁻ /Fe ²⁺ and UV-Vis/H ₂ O ₂ /HSO ₅ ⁻ /Fe ²⁺ .

In the above advanced oxidation treatment process, S ₂ O ₈ ^2- is ammonium, sodium or potassium persulfate, and HSO ₅ ^- is potassium monopersulfate double salt. A preferred persulfate is ammonium persulfate.

For the above-mentioned advanced oxidation treatment process, the illumination conditions are ultraviolet light, ultraviolet visible light, sunlight and simulated sunlight (long-arc xenon lamp radiation) and other illumination conditions, and the preferred illumination conditions are sunlight or simulated sunlight (long-arc xenon lamp radiation).

For the above advanced oxidation treatment process, the reaction time is 1.5-4 hours, and the preferred reaction time is 120-150 minutes.

For the above-mentioned advanced oxidation treatment process, sulfuric acid is used for acid adjustment, and 10% milk of lime is used for alkaline adjustment.

Detailed ways

Example 1

Add 12g/L inorganic coagulant polyaluminium chloride and 100mg/L organic flocculant cationic polyacrylamide to waste organic silicon drilling fluid discharged from an oil field, stir at high speed (300r/min) for 90s, and stir at low speed (20r/min) 10 to 15 minutes, centrifuge with a centrifuge at 3400r/min for 2 minutes. The residual turbidity of the separated water is 18FTU (10530FTU before treatment), the residual color is 5 times (10000 times before treatment), the COD _Cr is 1100mg/L (1.4× ¹⁰⁴ mg/L before treatment), and the removal rate reaches 99 %above. Adjust the pH value of the separated water to 4, then add hydrogen peroxide (30%) 7ml/L, 1.5g/L ammonium persulfate, 0.5mmol/L ferrous sulfate, and irradiate with sunlight for 120 minutes at 15-20°C Finally, use milk of lime to adjust the pH value to 8-9, and the COD _Cr of the catalyzed oxidation water is 147.6 mg/L; after irradiating with simulated sunlight (long-arc xenon lamp) in an externally illuminated photochemical reactor for 120 minutes, adjust the pH value to 8-9 , COD _Cr is 135.2mg/L. The content of heavy metal ions in this kind of waste drilling fluid after treatment is shown in Table 1.

Table 1 Contents of heavy metal ions in the effluent of waste polymer drilling fluid in different process stages

Note: "-" means "not detected"

Example 2

For waste polymer drilling fluid discharged from an oil field, add 16g/L inorganic coagulant polyaluminum chloride and 120mg/L organic flocculant cationic polyacrylamide, stir at high speed (300r/min) for 90s, and stir at low speed (20r/min) 10 to 15 minutes, centrifuge with a centrifuge at 3400r/min for 2 minutes. The residual turbidity of the separated water is 8FTU (8150FTU before treatment), the residual chromaticity is 10 times (8000 times before treatment), the COD _Cr is 730mg/L (6.6×10 ⁴ mg/L before treatment), and the removal rate reaches 99 %above. Adjust the pH value of the separated water to 4, then add hydrogen peroxide (30%) 7ml/L, 1.5g/L ammonium persulfate, 0.5mmol/L ferrous sulfate, and irradiate with sunlight for 120 minutes at 15-20°C Finally, use milk of lime to adjust the pH value to 8-9, and the COD _Cr of the catalyzed oxidation water is 147.2 mg/L; after irradiating with simulated sunlight (long-arc xenon lamp) in an externally illuminated photochemical reactor for 120 minutes, adjust the pH value to 8-9 , COD _Cr is 94.2mg/L. The content of heavy metal ions in this kind of waste drilling fluid after treatment is shown in Table 2.

Table 2 Contents of heavy metal ions in the effluent of waste polymer drilling fluid at different process stages

Note: "-" means "not detected"

Example 3

Add 12g/L inorganic coagulant polyaluminum chloride and 60mg/L organic flocculant cationic polyacrylamide to the waste potassium salt polymer drilling fluid discharged from an oil field, stir at high speed (300r/min) for 90s, and stir at low speed (20r/min ) stirring for 10 to 15 minutes, and centrifuged for 2 minutes with a centrifuge at 3400 r/min. The residual turbidity of the separated water is 8FTU (32600FTU before treatment), the residual chromaticity is 20 times (13500 times before treatment), the COD _Cr is 1059.6mg/L (4.4× ¹⁰⁴ mg/L before treatment), and the removal rate reaches More than 99%. Adjust the pH value of the separated water to 4, then add hydrogen peroxide (30%) 7ml/L, 1.0g/L ammonium persulfate, 0.5mmol/L ferrous sulfate, and irradiate with sunlight for 120 minutes at 15-20°C Finally, use milk of lime to adjust the pH value to 8-9, and the COD _Cr of the catalyzed oxidation water is 190.8 mg/L; after irradiating with simulated sunlight (long-arc xenon lamp) in an externally illuminated photochemical reactor for 120 minutes, adjust the pH value to 8-9 , COD _Cr is 112.8mg/L. The content of heavy metal ions in this kind of waste drilling fluid after treatment is shown in Table 3.

Table 3 Contents of heavy metal ions in the effluent of waste polymer drilling fluid at different process stages

Note: "-" means "not detected"

Claims (9)

1. new waste liquid of drilling method for innocent treatment and technology, concrete grammar: at first waste liquid of drilling is handled through chemical enhanced solid-liquid separation process, after the mechanical separation method separation, the waste liquid of drilling after separating is carried out the advanced oxidation advanced treatment, discharge then.

2. according to described waste liquid of drilling method for innocent treatment of claim 1 and technology, it is characterized in that: compound use inorganic coagulant of the chemical enhanced solid-liquid separation process of waste liquid of drilling and organic floculant, at first in waste liquid of drilling, add inorganic coagulant, the broken glue of suspensoid is taken off surely; Add organic floculant then, make and take off steady colloid and sign an undertaking bigger flco, realize chemical enhanced solid-liquid separation.

3. comprise Tai-Ace S 150, ferric sulfate, aluminum chloride, ferric sesquichloride, calcium chloride, calcium hydroxide, polymerize aluminum chloride and bodied ferric sulfate etc. according to used inorganic coagulant in the chemical enhanced reinforcement solid-liquid separation process described in the claim 2; Organic floculant comprises: non-ionic polyacrylamide, anionic polyacrylamide and cationic polyacrylamide.

4. be polymerize aluminum chloride according to the used inorganic coagulant of chemical enhanced solid-liquid separation process described in the right 2; Organic floculant is a cationic polyacrylamide, and molecular weight is greater than 1000w, and cationic degree is 15～20%.

5. according to method for innocent treatment of waste liquid of drilling described in the claim 1 and technology, it is characterized in that: solid-liquid separating method adopts modes such as press filtration, vacuum filtration, centrifuge dehydration, selects centrifugation that waste liquid of drilling is carried out solid-liquid separation.

6. according to method for innocent treatment of waste liquid of drilling described in the claim 1 and technology, it is characterized in that the well-drilling waste water after the mechanical separation adopts the high-level oxidation technology advanced treatment.

7. according to the advanced oxidation of waste liquid of drilling described in the claim 6 treatment process, it is characterized in that: adopt H ₂O ₂/ Fe ²⁺, H ₂O ₂/ Fe ²⁺-complexing agent, UV-Vis/H ₂O ₂/ Fe ²⁺, UV-Vis/H ₂O ₂/ Fe ²⁺-complexing agent, H ₂O ₂/ S ₂O ₈ ^2-/ Fe ²⁺Or H ₂O ₂/ HSO ₅ ^-/ Fe ²⁺, UV-Vis/H ₂O ₂/ S ₂O ₈ ^2-/ Fe ²⁺Or UV-Vis/H ₂O ₂/ HSO ₅ ^-/ Fe ²⁺In a kind of advanced oxidation treatment technology.

8. according to the advanced oxidation of waste liquid of drilling described in the claim 6 treatment process, it is characterized in that: adopt UV-Vis/H ₂O ₂/ HSO ₅ ^-/ Fe ²⁺The advanced oxidation treatment technology, regulating wastewater pH with sulfuric acid is 3～4, adopts daylight or solar simulated as illumination condition, reaction finishes the back and regulates the pH value with 10% milk of lime.

9. according to advanced oxidation treatment process described in the right 6, S ₂O ₈ ^2-Be ammonium salt, sodium salt or the sylvite of persulfuric acid, HSO ₅ ^-Be Potassium Monopersulfate double salt.