Coal bed gas fracturing flow-back fluid pretreatment device

Abstract

The utility model provides a coal bed gas fracturing flow-back fluid pretreatment device which comprises an electrocatalytic oxidation pond, a coagulative precipitation pond and a stirring device located in the electrocatalytic oxidation pond and the coagulative precipitation pond, and further comprises electrode modules evenly distributed in the electrocatalytic oxidation pond, each electrode module comprises four anodes and five cathodes, the anode is niobium-based and is coated with a boron-doped diamond film on the surface, the cathode is titanium-based and is coated with a boron-doped diamond film on the surface, and the anode and the cathode of the electrode module are respectively connected with the anode and the cathode of the direct-current power supply. The device is simple in structure, remarkable in gel breaking effect and suspended matter removal effect and reliable in operation, and the problem that the treatment effect is not remarkable when a flocculating agent is directly added into the coal bed gas flow-back fluid is solved.

Description

Technical Field

[0001] The utility model relates to the field of sewage pretreatment devices, in particular to a coalbed methane fracturing return fluid pretreatment device. Background Art

[0002] Coalbed methane is an important unconventional oil and gas resource. At present, the exploration and development of coalbed methane is strong and the growth rate is fast. The amount of fracturing return fluid has increased sharply. The coalbed methane return fluid contains a variety of additives, resulting in the return fluid having the characteristics of high colloid content, suspended matter, and calcium and magnesium ion content. Reinjection is an ideal disposal method for coalbed methane return fluid, but the reinjection capacity is limited and rash reinjection may cause serious damage to the geological reservoir. As environmental protection requirements become more and more stringent, various regions have raised the requirements for reinjection indicators and restricted the scale of reinjection.

[0003] At the same time, the demand for fresh water for fracturing fluid configuration during the fracturing operation of coalbed methane development is relatively large, and most of the coalbed methane development blocks are water-deficient areas, and there is a large gap in water resources for coalbed methane development. Among them, the fresh water for fracturing fluid configuration requires the suspended solids content of water quality to be less than 50mg / L. Coagulation and sedimentation method is the main method for removing suspended solids in sewage. The working principle is to polymerize and form flocs with large volume and good sedimentation performance by adding coagulants and coagulants, and achieve the purpose of solid-liquid separation under the action of gravity. However, the colloid content in the coalbed methane fracturing return fluid is high, and it has the characteristics of strong stability of water quality, and there are many fine suspended particles. Because the colloid has the same charge property and has a high repulsive energy, it cannot come into direct contact with the substance, resulting in it being in a particle state in the water body and suspended in the water, which is difficult to be removed and precipitated, limiting its coagulation and sedimentation treatment effect, and seriously affecting the return of fracturing return fluid. Utility Model Content

[0004] The technical problem to be solved by the utility model is to provide a coalbed methane fracturing return fluid pretreatment device, which has a simple structure and significant gel breaking effect and suspended matter removal effect.

[0005] The technical solution of the present application is: a coalbed methane fracturing return fluid pretreatment device, including an electrocatalytic oxidation tank, a coagulation sedimentation tank and a stirring device located in the electrocatalytic oxidation tank and the coagulation sedimentation tank, and also including an electrode module evenly distributed in the electrocatalytic oxidation tank, each of the electrode modules includes four anodes and five cathodes, the anode is niobium-based and covered with a boron-doped diamond film on the surface, the cathode is titanium-based and covered with a boron-doped diamond film on the surface, the anode and cathode of the electrode module are respectively connected to the positive and negative electrodes of a DC power supply.

[0006] Wherein, the anode and cathode are sheet-shaped bodies with a side surface area of ​​25mm×25mm~30mm×30mm.

[0007] Further, the distance between the anode and the cathode is 1.5 - 2 mm.

[0008] Further, the thickness of the boron-doped diamond films attached to the anode and the cathode is 10 μm each.

[0009] Further, the anodes and cathodes in each electrode module are alternately distributed on the same straight line, and the two ends of each electrode module are cathodes.

[0010] Among them, a water inlet pipeline is arranged at the bottom on one side of the electrocatalytic oxidation tank far from the coagulation sedimentation tank, a water outlet pipeline is arranged at the upper end on one side of the coagulation sedimentation tank far from the electrocatalytic oxidation tank, and a sludge discharge pipeline is arranged at the bottom of the coagulation sedimentation tank on the same side as the water outlet pipeline.

[0011] The advantages and beneficial effects of this application are:

[0012] 1. The special structure of the boron-doped diamond thin film and its conductivity endow it with an extremely high oxygen evolution potential. The relatively high oxygen evolution potential can efficiently generate strongly oxidizing hydroxyl radicals. The hydroxyl radicals have very high activity and can effectively catalytically oxidize organic substances. At the same time, diamond has adsorption inertness to many chemical substances and is not prone to electrode passivation and pollution phenomena.

[0013] 2. In this application, the setting of four anodes corresponding to five cathodes can overcome the deficiency that only one side of the anode works under the condition of one-to-one correspondence between the anode and the cathode, improve the utilization rate of the anode, which is equivalent to reducing the replacement frequency of the anode material and saving more costs.

[0014] 3. Both the anode and the cathode are coated with boron-doped diamond thin films, which can switch the positive and negative poles of the power supply at any time and overcome the problem of scaling when the concentration of calcium and magnesium ions is high at the anode and cathode.

[0015] 4. This device can be adapted to the treatment of coalbed methane fracturing flowback fluid, realizing the gel breaking and coagulation pretreatment of coalbed methane fracturing flowback fluid, laying a foundation for subsequent treatment; it has the advantages of stable gel breaking and coagulation treatment effects, reliable operation, and significantly improved suspended solid removal effect, solving the problem that the treatment effect is not obvious when directly adding flocculants to coalbed methane flowback fluid. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is a schematic structural diagram of the present utility model.

[0017] In the figure: 1. Electrocatalytic oxidation tank; 2. Electrode module; 3. Water inlet pipeline; 4. Water outlet pipeline; 5. Stirring device; 6. Coagulation sedimentation tank; 7. Sludge discharge pipeline. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0018] The following will describe in detail the specific embodiments of the present utility model with reference to the accompanying drawings.

[0019] As Figure 1 shown, the technical solution proposed by the utility model is as follows:

[0020] Example 1 A pretreatment device for coalbed methane fracturing flowback fluid, including an electrocatalytic oxidation tank 1, a coagulation sedimentation tank 6 and a stirring device 5 located in the electrocatalytic oxidation tank 1 and the coagulation sedimentation tank 6, further including an electrode module 2 uniformly distributed in the electrocatalytic oxidation tank 1. Each electrode module 2 includes four anodes and five cathodes. The anode is niobium-based with a boron-doped diamond film on its surface, and the cathode is titanium-based with a boron-doped diamond film on its surface. The anodes and cathodes of the electrode module 2 are respectively connected to the positive and negative poles of a DC power supply.

[0021] Among them, the anode and the cathode are sheet-shaped bodies with a side surface area of 25mm×25mm to 30mm×30mm.

[0022] Furthermore, the distance between the anode and the cathode is 1.5 - 2mm.

[0023] Furthermore, the thickness of the boron-doped diamond film attached to both the anode and the cathode is 10μm. Both the anode and the cathode are covered with boron-doped diamond thin films, which can switch the positive and negative poles of the power supply at any time to overcome the problem of scaling of the anode and cathode in the case of high calcium and magnesium ion concentrations.

[0024] The setting of four anodes corresponding to five cathodes can overcome the deficiency that only one side of the end anode works under the condition of one-to-one correspondence between the anode and the cathode. The anode material cost is greater than that of the cathode. The anodes and cathodes in each electrode module 2 are alternately distributed on the same straight line and both ends of each electrode module 2 are cathodes, which improves the utilization rate of the anode, equivalent to reducing the replacement frequency of the anode material and saving more costs.

[0025] Among them, a partition with a height lower than the overall height of the two tank bodies is provided between the catalytic oxidation tank 1 and the coagulation sedimentation tank 6. A water inlet pipeline 3 is arranged at the bottom of one side of the electrocatalytic oxidation tank 1 far from the coagulation sedimentation tank 6, and a water outlet pipeline 4 is arranged at the upper end of one side of the coagulation sedimentation tank 6 far from the electrocatalytic oxidation tank 1. A sludge discharge pipeline 7 is arranged at the bottom of the coagulation sedimentation tank 6 on the same side as the water outlet pipeline 4. The coalbed methane fracturing flowback fluid enters the electrocatalytic oxidation tank 1 through the water inlet pipeline 3, and the coalbed methane fracturing flowback fluid is subjected to electrocatalytic oxidation and gel-breaking treatment under the combined action of the stirring device 5 and the electrode module 2. After the gel-breaking treatment, the sewage removes suspended solids by adding flocculants and coagulants in the coagulation sedimentation tank 6, and the sludge is discharged through the sludge discharge pipeline 7.

[0026] Example 2 Using the pretreatment device described in Example 1 to treat the coalbed methane fracturing flowback fluid in a certain western area. The suspended solid content of this wastewater is 605.6mg / L, and the pretreatment results are shown in Table 1:

[0027]

[0028] Through comparison, it is found that after the coalbed methane fracturing flowback fluid is treated by the above sewage pretreatment device, the removal effect of suspended solids has been significantly improved.

[0029] The above has described in detail an embodiment of the present invention, but the content described is only a preferred embodiment of the present invention and cannot be considered as limiting the scope of implementation of the present invention. All equivalent changes and improvements made according to the scope of the present invention application should still fall within the patent coverage scope of the present invention.

Claims

1. A coalbed methane fracturing flowback fluid pretreatment device, comprising an electrocatalytic oxidation tank (1), a coagulation sedimentation tank (6), and a stirring device (5) located in the electrocatalytic oxidation tank (1) and the coagulation sedimentation tank (6), characterized in that: It also includes electrode modules (2) uniformly distributed in the electrocatalytic oxidation tank (1), each of the electrode modules (2) including four anodes and five cathodes, the anodes are niobium-based and have a boron-doped diamond film on their surfaces, the cathodes are titanium-based and have a boron-doped diamond film on their surfaces, and the anodes and cathodes of the electrode modules (2) are respectively connected to the positive and negative electrodes of a direct current power supply.

2. The coalbed methane fracturing flowback fluid pretreatment device according to claim 1, characterized in that: The anode and cathode are sheet-shaped bodies with a side surface area of ​​25 mm×25 mm to 30 mm×30 mm.

3. The coalbed methane fracturing flowback fluid pretreatment device according to claim 1, characterized in that: The distance between the anode and the cathode is 1.5-2 mm.

4. The coalbed methane fracturing flowback fluid pretreatment device according to claim 1, characterized in that: The thickness of the boron-doped diamond film attached to the anode and the cathode is 10 μm.

5. The coalbed methane fracturing flowback fluid pretreatment device according to claim 1, characterized in that: The anodes and cathodes in each electrode module (2) are alternately distributed on the same straight line, and both ends of each electrode module (2) are cathodes.

6. The coalbed methane fracturing flowback fluid pretreatment device according to claim 1, characterized in that: A water inlet pipeline (3) is arranged at the bottom of one side of the electrocatalytic oxidation tank (1) away from the coagulation sedimentation tank (6), a water outlet pipeline (4) is arranged at the upper end of one side of the coagulation sedimentation tank (6) away from the electrocatalytic oxidation tank (1), and a sludge discharge pipeline (7) is arranged at the bottom of the coagulation sedimentation tank (6) on the same side as the water outlet pipeline (4).

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