CN1176859C - Coagulation and dehydration treatment method of waste drilling fluid - Google Patents

Abstract

The present invention provides a coagulating and dewatering treatment method of waste drilling fluid, which particularly comprises the following steps: an inorganic aluminum salt flocculating agent and organic cation polyelectrolyte flocculating agent solution are added into the waste drilling fluid, and mixed solution is statically coagulated for 10 to 15 minutes after the mixed solution is uniformly stirred; after the waste drilling fluid is completely chemically stably dewatered, lump flocculates and part of flocculated water are centrifugally dewatered. The inorganic aluminum salt flocculating agent is preferably aluminum trichloride, and the use level of the aluminum trichloride is from 2000 to 3500 mg/L; an organic cation polyelectrolyte flocculating agent is organic cation polyelectrolyte with a quaternary ammonium salt cation functional group, suspended fine particles are prompted to coagulate the bulk flocculates under the synergy of the coagulation and the flocculation of the inorganic aluminum salt flocculating agent and the organic cation polyelectrolyte flocculating agent, and then the purpose of the solid-liquid separation of the waste drilling fluid is achieved after a centrifugally dewatering process.

Description

Coagulation and dehydration treatment method of waste drilling fluid

Technical field:

The invention relates to a treatment method for waste drilling fluid in oil and gas fields, in particular to a dehydration treatment method for waste drilling fluid.

Background technique:

During the drilling process of oil and gas fields, drilling fluid leakage, replacement of drilling fluid, cleaning of drilling platform, removal of cuttings and blowout accidents will generate a large amount of waste drilling fluid and sewage. According to the size of the drilling rig and the drilling depth, the amount of waste produced varies. Generally, the waste drilling fluid produced by each well is about 200 to 300 cubic meters. Therefore, the treatment of waste drilling fluid has become an important research content of environmental protection. The Chinese patent "Drilling and Completion Mud Recovery and Treatment Device" (88218926.3) introduces a heating, drying and curing system to treat waste mud. This device has the disadvantages of high energy consumption and slow processing speed, and is not suitable for mass processing of waste drilling fluid. The patent "Slurry Solid-Liquid Separation Method and Equipment" (98104310) proposes to rely on natural sedimentation and use movable filters to separate the solid matter contained in the slurry, but it is not suitable for drilling mud with good colloidal stability, and the mud is static It will not settle and separate after being placed for several months. The patent "Method of Treating Mud Water" (90101597.0) proposes to add alkaline earth metal oxide or hydroxide and anionic polymer coagulant to mud water, and then add sulfuric acid and anionic polymer coagulant to produce large flocculation The flocs obtained by using this method to treat waste drilling fluid have poor stability, and can return to gel and form mud after soaking in water for a long time, which has potential secondary pollution. The patent "Treatment Method and Storage Structure of Waste Drilling Fluid" (92108103.0) and the patent "Composite Efficient Drilling Mud Wastewater Treatment Agent" (91102191) both propose adding inorganic flocculants such as aluminum sulfate and organic flocculants such as hydrolyzed polyacrylamide to the waste drilling fluid. Flocculant: After flocculation and settlement, the supernatant is drawn out, and a layer of fiber is added to the concentrated flocculation sediment, and then sealed with concrete such as cement. Since hydrolyzed polyacrylamide is an anionic polymer flocculant, the flocculation of mud clay particles is formed by bridging adsorption, and the flocs produced by this method of treating waste drilling fluid are poor in stability, and the long-term immersion in water Automatic back glue to form mud. Although the concrete cover layer on the top surface of the flocs isolates it from the air, the back-glued mud can diffuse and leak into the surrounding soil along the surrounding and bottom layers of the pit, and continue to cause environmental pollution.

Invention content:

The purpose of the present invention is to overcome the shortcomings of the existing treatment methods and provide a dehydration treatment method for waste drilling fluids with low energy consumption, high treatment speed, good stability of flocs and environmental protection.

The treatment method of the present invention is composed of coagulation and flocculation, chemical destabilization and dehydration, and solid-liquid separation. minute. After the waste drilling fluid is completely chemically destabilized and dehydrated, the agglomerated flocs and part of the flocculated water are centrifuged and dehydrated. The centrifuge speed can be selected at 2000-5000 rpm.

The invention provides a novel inorganic aluminum salt flocculant and an organic cationic polyelectrolyte flocculant;

The above-mentioned inorganic aluminum salt coagulant is composed of one or more of aluminum sulfate, aluminum trichloride, potassium aluminum sulfate dodecahydrate, polyaluminum chloride, polyaluminum sulfate, iron-aluminum copolymer, etc.;

Preferably, the inorganic aluminum salt coagulant is aluminum trichloride, and its usage amount is 2000-3500 mg/L.

The above-mentioned organic cationic polyelectrolyte flocculants are organic cationic polyelectrolytes with quaternary ammonium salt cationic functional groups, such as diallyl dimethyl ammonium chloride-acrylamide copolymer, acrylamide-ethyl acrylate trimethyl chloride Ammonium Copolymer, Acrylamide-Ethyl Methacrylate Trimethylammonium Chloride Copolymer, Acrylamide-Ethyl Acrylate Trimethylammonium Methyl Sulfate Copolymer, Acrylamide-Ethyl Methacrylate Trimethylammonium One or more such as ammonium methyl sulfate copolymer.

The polyelectrolyte containing quaternary ammonium salt cationic groups is characterized by a molecular weight of 1×10 ⁶ to 10×10 ⁶ and a cationic degree of 5% to 80%. The best cationic flocculant is acrylamide-ethyl acrylate trimethylammonium chloride copolymer with a molecular weight of 3×10 ⁶ and a cationic degree of 15%.

The best synergistic inorganic aluminum salt coagulant and organic cationic polyelectrolyte coagulant is aluminum trichloride and acrylamide-ethyl acrylate-based trimethylammonium chloride copolymer, which can effectively flocculate the waste drilling fluid system after chemical destabilization In the solid phase particles, the amount of the latter is 200-300mg/L.

Under the synergistic effect of coagulation and flocculation of the novel inorganic aluminum salt flocculant and organic cationic polyelectrolyte flocculant of the present invention, the negatively charged clay particles on the surface of the mud are completely destroyed by electrostatic neutralization and bridging adsorption of macromolecules. Colloidal system, which promotes the coalescence of suspended fine particles into large flocs. After centrifugal dehydration, it ensures that the flocculated sludge has a good ability to resist water immersion. The separated water can be recycled and reused, such as preparing drilling fluid, etc., for decementing The slag can be directly and safely buried underground, and finally achieve the purpose of solid-liquid separation of waste drilling fluid.

Description of drawings:

Fig. 1 is a flow chart of coagulation and dehydration treatment of waste drilling fluid.

Detailed ways:

As shown in Figure 1, first pump the waste drilling fluid into the mud tank or other containers, then add the inorganic coagulant and cationic organic flocculant solutions to the container containing the waste drilling fluid in sequence, and start the mixer to stir slowly and evenly , static coagulation for 10 to 15 minutes, after the waste drilling fluid is completely chemically destabilized and dehydrated, the agglomerate flocs and part of the flocculated water are pumped into the centrifuge, and the water separated by centrifugation can be recycled for drilling operation, the decemented slag can be directly and safely buried in the ground.

Take the treatment of coagulation and dehydration of different types of waste drilling fluids produced by four wells in four oilfields in my country, including Zhongyuan Pu 5123 Well, Xinjiang Bao 101 Well, Jiangsu Sha 7 Well and Jiangsu Zhen 138 Well, as an example, see the table below.

Table 1 Example Waste Drilling Fluid Sources coagulant flocculant 1 Zhongyuan Pu 5123 well 3500mg/L aluminum trichloride 300mg/L Acrylamide-Ethyl Acrylate Trimethylammonium Chloride Copolymer 2 Well Bao 101 in Xinjiang 3000mg/L aluminum trichloride 240mg/L Acrylamide-Ethyl Acrylate Trimethylammonium Chloride Copolymer 3 Well Sha 7, Jiangsu 2700mg/L aluminum trichloride 200mg/L Acrylamide-Ethyl Acrylate Trimethylammonium Chloride Copolymer 4 Jiangsu Zhen 138 well 2000mg/L aluminum trichloride 210mg/L Acrylamide-Ethyl Acrylate Trimethylammonium Chloride Copolymer

After the chemical destabilization of the above four waste drilling fluids, strong flocculation occurred, and the solid phase particles coalesced and increased significantly. The average particle size increased from 10.3 μm before flocculation to 126.3-283 μm; the median particle size increased from 4.1 μm to 106.9-246.1 μm, the number of particles with a particle size of less than 20 μm is reduced from 85.5% before flocculation to 5.3%, and a part of water can be separated naturally, and the remaining free water in the pores of the flocculation mass can be separated by further use of a centrifuge , so that the turbidity of the separated water is low and the decolorization is good, which ensures the quality of the solid-liquid separation of the waste drilling fluid. The results are shown in Table 2 and Table 3. After 4000 RPM/separation centrifugal dehydration, the final centrifugal dehydration rate of waste drilling fluid reaches 59%.

Table 2 Example 1 of waste pulp source Zhongyuan Pu 5132 well Sampling Well depth Density Viscosity pH value Oil content Water content Solid phase content Time m g/cm ³ s %v %v %v g/L 1995.3 2760 1.29 50 9.0 5.0 75.0 20.0 440 Rheological parameters main treatment agent Remark Φ ₆₀₀ Φ ₃₀₀ Φ ₂₀₀ Φ ₁₀₀ Φ ₆ Φ ₃ HPAN, HPAM, FCLS, LV-CMC, HV-CMC, crude oil Color: Dark Brown Odor: Oily 178 142 129 113 84 81 Example 2 of Well Bao 101 in Xinjiang Sampling Well depth Density Viscosity pH value Oil content Water content Solid phase content Time m g/cm ³ s %v %v %v g/L 1995.5 2500 1.20 54 8.0 2.5 86.5 11.0 400 Rheological parameters main treatment agent Remark Φ ₆₀₀ Φ ₃₀₀ Φ ₂₀₀ Φ ₁₀₀ Φ ₆ Φ ₃ FA-367, XY-27, SMPSPNH, PAC-142, Color: Dark Brown Odor: Oily 146 100 80 55 24 20 Example 3 of Jiangsu Sha 7 Well Sampling and depth Density Viscosity pH value Oil content Water content Solid phase content Time m g/cm ³ s %v %v %v g/L 1994.10 2100 1.20 40 9.5 6.0 82.5 11.5 290 Rheological parameters main treatment agent Remark Φ ₆₀₀ Φ ₃₀₀ Φ ₂₀₀ Φ ₁₀₀ Φ ₆ Φ ₃ HPAN, HPAM, XY-27ABSN, modified bitumen, crude oil Color: Dark Brown Odor: Oily 153 102 81 55 15 13 Example 4 of Well 138 in Jiangsu Sampling Well depth Density Viscosity pH value Oil content Water content Solid phase content Time m g/cm ³ s %v %v %v g/L 1994.10 2573 1.14 44 10.0 7.0 85.0 8.0 265 Rheological parameters main treatment agent Remark Φ ₆₀₀ Φ ₃₀₀ Φ ₁₀₀ Φ ₁₀₀ Φ ₆ Φ ₃ HPAN, HPAM, XY27, FA367, emulsifier, crude oil Color: Dark Brown Odor: Oily 151 105 75 54 17 12

Note: ①The viscosity test temperature of the waste slurry is about 25°C;

② The main treatment agents used in drilling fluids, HPAN, HPAM, FCLS, CMC, FA367, XY27, SMP, SPNH, PAC142, ABSN, etc. are the code names of polymer compounds with different functions.

in:

HPAN: Hydrolyzed Polyacrylonitrile.

HPAM: Hydrolyzed polyacrylamide.

FCLS: Iron chromium lignosulfonate.

CMC: sodium carboxymethylcellulose.

FA367: Composite ionic polymer fluid loss control agent.

XY-27: Zwitterionic polymer containing anionic and cationic groups, belonging to multi-polymer of vinyl monomers.

SMP: sulfomethyl phenolic resin.

SPNH: It is a ternary compound containing hydroxyl, carbonyl, methylene, sulfonic acid, benzene ring, carboxyl and nitrile group, which is obtained by grafting copolymerization and sulfonation, using lignite and kelp waste silk as the main raw materials. copolymer.

PAC142: Multi-polymer of acrylic acid, acrylic acid amine, acrylonitrile, sodium propylene sulfonate.

ABSN: sodium dodecylbenzenesulfonate.

table 3 waste pulp Before flocculation After flocculation ＜20μm particles Average particle size Median particle size (%) (μm) (μm) ＜20μm particles Average particle size Median particle size (%) (μm) (μm) Example 1 Example 2 Example 3 Example 4 85.5 10.3 4.185.5 10.7 6.085.3 10.8 6.042.4 54.2 28.5 5.3 126.3 106.91.2 177.6 161.81.7 283.0 246.13.3 134.1 118.6

Claims (5)

1. A treatment method for coagulation and dehydration of waste drilling fluid, which is characterized in that it is composed of coagulation and flocculation, chemical destabilization and dehydration, and solid-liquid separation; the specific method is: adding inorganic aluminum salt coagulant and organic Cationic polyelectrolyte flocculant solution, stir evenly and then coagulate statically for 10-15 minutes; after the waste drilling fluid is completely chemically destabilized and dehydrated, centrifuge and dehydrate the agglomerated flocs and part of the flocculated water, the centrifuge speed is 2000-5000 rpm / min; the organic cationic polyelectrolyte flocculant is an organic cationic polyelectrolyte with a quaternary ammonium salt cationic functional group, including diallyl dimethyl ammonium chloride-acrylamide copolymer, acrylamide-ethyl acrylate group three Methylammonium chloride copolymer, acrylamide-ethyl methacrylate trimethylammonium chloride copolymer, acrylamide-ethyl acrylate trimethylammonium methyl sulfate copolymer, acrylamide-ethyl methacrylate One or more of ester group trimethylammonium methyl sulfate copolymer. 2. The waste drilling fluid coagulation dehydration treatment method according to claim 1, characterized in that the inorganic aluminum salt coagulant is composed of aluminum sulfate, aluminum trichloride, potassium aluminum sulfate dodecahydrate, polyaluminum chloride, polysulfuric acid One or more of aluminum and iron-aluminum copolymers. 3. The coagulation and dehydration treatment method of waste drilling fluid according to claim 2, characterized in that the inorganic aluminum salt coagulant is aluminum trichloride, and its usage amount is 2000-3500 mg/L. 4. The coagulation and dehydration treatment method of waste drilling fluid according to claim 1, characterized in that the organic cationic polyelectrolyte flocculant contains a polyelectrolyte with a quaternary ammonium salt cationic group, and its molecular weight is 1×10 ⁶ to 10×10 ^6. The cationic degree is 5% to 80%. 5. The waste drilling fluid coagulation and dehydration treatment method according to claim 1, characterized in that said inorganic aluminum salt coagulant and organic cationic polyelectrolyte coagulant are aluminum trichloride and acrylamide-ethyl acrylate trimethyl ammonium chloride copolymer, the amount of acrylamide-ethyl acrylate trimethylammonium chloride copolymer is 200-300mg/L, and the cationic flocculant acrylamide-acrylic acid used in conjunction with the coagulant aluminum chloride The molecular weight of the ethyl ester trimethyl ammonium chloride copolymer is 3×10 ⁶ , and the cationic degree is 15%.

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