CN1300008C - Electrolytic method for treating sewage in oil field - Google Patents

Abstract

The invention discloses a method for electrolytically treating oil field sewage. The method comprises the following steps: 1. electrolysis; 2. flocculation; 3. sedimentation; 4. filtration. The electrolysis step involved in the present invention does not introduce other chemicals, so there is no additional generation of sludge, less sludge, no pollution, resource and cost saving, in line with "green chemical technology", sterilization will not produce drug resistance, easy to operate, It is safe, easy to regulate and realize automation, has wide adaptability to different water volume and water quality, and has unique advantages such as easy promotion and application.

Description

A method for electrolytic treatment of oilfield sewage

technical field

The invention relates to a method for electrolytically treating oil field sewage.

Background technique

In the process of oilfield production and development, oily sewage should be produced at the same time, such as oilfield produced water, trench water, well washing water and other oilfield sewage. Oilfield sewage contains impurities such as suspended solids, colloids, dispersed oil, slick oil, and dissolved substances. These sewage must be further treated before further use. Oilfield sewage treatment is to try to remove suspended solids, colloids, dispersed oil and slick oil.

At present, oilfield sewage is mainly treated by a "three-stage" process, that is, oil recovery in large tanks, flocculation and sedimentation, and bed filtration. The oilfield sewage treated according to this process cannot all meet the requirements of various standards (SY/T5329-94) for oilfield injection water. Even if some indicators can meet the standards at the sewage treatment station, due to unstable water quality, it deteriorates along the process, and when it reaches the water injection well , the water quality is not up to standard. Using "water quality modification technology" to treat oilfield sewage, except for bacteria, all indicators can meet the requirements of oilfield injection water, but this method generates a large amount of additional sludge due to the addition of calcium hydroxide (lime). As time goes by, the problem of sludge and bacteria has restricted the normal production of oil fields more and more seriously.

Electrolysis refers to the electrolysis process in the field of electrochemistry, that is, a process in which a current passes through an electrolyte solution or a molten salt electrolyte to cause a chemical reaction to occur simultaneously on two electrodes (or next to the electrodes). When energized, the positive ions in the solution (or molten salt) migrate to the cathode, and the negative ions migrate to the anode; at the same time, a reduction reaction occurs on the cathode to produce new substances; an oxidation reaction occurs on the anode to produce new substances.

At present, there is no report on the application of electrolysis method to the treatment of oilfield sewage.

Contents of the invention

The purpose of the present invention is to propose a method for electrolytic treatment of oilfield sewage in view of the deficiencies in the prior art. The method has better purifying and stabilizing effects when treating oil field sewage.

To achieve the above object, the present invention has taken the following technical solutions:

A method for electrolytic treatment of oilfield sewage, characterized in that it comprises the steps of:

(1) Electrolysis; electrolysis is carried out by energizing oilfield sewage; the distance between the electrode plates is 0.1-100 mm, the voltage between each pair of plates is between 0.5-30 volts, and the current density is 10-3000A/m ² ;

The anode is a reactive metal material, an inert metal material, an alloy or a non-metallic material;

The cathode is a reactive metal material, an inert metal material or an alloy;

(2), flocculation;

(3), settlement;

(4), filter.

Reactive metal materials, inert metal materials, alloys or non-metal materials used in electrodes; electrode materials can be aluminum, iron, platinum, ruthenium, rhodium, titanium, gold, stainless steel, graphite and other simple substances or their alloys, coatings and other forms.

The electrodes used for electrolysis in step (1) can also be two pairs or more than two pairs, and the electrodes are connected in series, parallel or a combination thereof.

As a preference, the distance between the electrode plates of the electrodes is 0.5-30 millimeters.

As another preference, the voltage between the electrodes is 1-15 volts, and the current density is 500-3000 A/m ² .

The three processes of flocculation, sedimentation and filtration used in the present invention are common techniques in this technical field, and can be well grasped by ordinary technical personnel.

The energization described in the present invention includes direct current and alternating current.

Compared with the prior art, the present invention has the following beneficial effects:

In the electrolysis step involved in the present invention, no other chemicals are introduced, so there is no additional generation of sludge, less sludge, no pollution, saving resources and costs, conforming to the "green chemical process", sterilization will not produce drug resistance, It is easy to operate, safe, easy to regulate and realize automation, has a wide range of adaptability to different water volume and water quality, and has unique advantages such as easy promotion and application.

Detailed ways

The present invention will be further described below in conjunction with specific examples.

Example 1

Using electrolytic pre-oxidation method to treat the sewage of an oilfield sewage station, the flow rate is 200m ³ /h, the electrolysis voltage between each pair of cathode and anode is 3.18V, the electrolysis current is 5736A, 12 pairs of electrodes are connected in parallel, and the total electrode area is 3.84m ^2. The distance between each pair of cathode and anode plates is 14 mm, the anode material is aluminum, and the cathode material is platinum. The anode oxidizes the reducing substances in the sewage, such as Fe ²⁺ , S ^2- plasma and FeS colloid, etc. into colloidal Fe _n (OH) _m ^{(3n-m) +} and elemental S, and the bacteria are completely killed, followed by flocculation, Settling and filtering, so that the sewage can be treated into standard injection water that fully meets the requirements of SY/T5329-94, and the water quality is stable.

The results of this embodiment are shown in Table 1 below:

Table 1 Sulfur mg/L Organic miscellaneous mg/L Oil mg/L MF ΣFemg/L SRB/ml TGB/ml Corrosion rate mm/a standard ≤10 ≤3 ≤10 ≥15 ≤0.5 ≤10 ≤10 ≤0.076 sewage station 0.2 1.0 3.8 32 0.27 0 0 0.031 Wellhead 0.2 1.3 1.47 33.5 0.31 0 0 0.028

Example 2

The sewage flow rate of the oilfield sewage station is 360m ³ /h, which is treated by electrolytic pre-oxidation. The electrolysis voltage between each pair of cathode and anode is 3.37V, the electrolysis current is 9834A, 21 pairs of electrodes are connected in parallel, the total electrode area is 6.72m ² , the distance between each pair of cathode and anode plates is 20mm, the anode material is stainless steel, the cathode The material is aluminum. The anode oxidizes the reducing substances in the sewage, such as Fe ²⁺ , S ^2- plasma and FeS colloid, etc. into colloidal Fe _n (OH) _m ^{(3n-m) +} and elemental S, and the bacteria are completely killed, followed by flocculation, Settling and filtering, so that the sewage can be treated into standard injection water that fully meets the requirements of SY/T5329-94, and the water quality is stable.

The results of this embodiment are shown in Table 2:

Table 2 Sulfur mg/L Organic miscellaneous mg/L Oil mg/L MF ΣFemg/L SRB/ml TGB/ml Corrosion rate mm/a standard ≤10 ≤3 ≤10 ≥15 ≤0.5 ≤10 ≤10 ≤0.076 sewage station 0 1.4 2.27 38.5 0.43 0 10 0.014 Wellhead 0 1.5 1.35 32 0.28 0 10 0.032

Example 3

The sewage flow rate of the oilfield sewage station is 430m ³ /h, which is treated by electrolytic pre-oxidation. The electrolysis voltage between each pair of cathode and anode is 6.82V, and the electrolysis current is 6393A; this step consists of 26 pairs of electrodes, a total of 13 pairs of electrodes in the first group are connected in parallel, and a total of 13 pairs of electrodes in the second group are connected in parallel, and then the two groups of electrodes are connected in series connection; the total electrode area is 8.32m ² , the distance between each pair of cathode and anode plates is 25 mm, the anode material is graphite, and the cathode material is stainless steel. The anode oxidizes the reducing substances in the sewage, such as Fe ²⁺ , HS ^- , H ₂ S plasma and FeS colloid, etc. into colloidal Fe _n (OH) _m ^{(3n-m) +} and elemental S, and the bacteria are almost completely killed. Then carry out flocculation, sedimentation, and filtration, so that the sewage can be treated into standard injection water that fully meets the requirements of SY/T5329-94, and the water quality is stable.

The result of this embodiment is as shown in table 3:

table 3 Sulfur mg/L Organic miscellaneous mg/L Oil mg/L MF ΣFemg/L SRB/ml TGB/ml Corrosion rate mm/a standard ≤10 ≤3 ≤10 ≥15 ≤0.5 ≤10 ≤10 ≤0.076 sewage station 0.1 0 3.2 28 0.20 0 10 0.051 Wellhead 0.3 2.0 1.7 25 0.34 0 10 0.029

It can be seen from the above examples that the electrolysis step used in the present invention does not introduce other chemicals, so there is no additional generation of sludge, less sludge, no pollution, resource and cost saving, in line with "green chemical process", sterilization will not It produces drug resistance, is simple and safe to operate, easy to control and realize automation, has a wide range of adaptability to different water volume and water quality, and is easy to promote and apply.

Claims (5)

1. A method for electrolytic treatment of oilfield sewage, characterized in that it comprises the steps: (1) Electrolysis; electrolysis is carried out by energizing oilfield sewage; the distance between the electrode plates is 0.1-100 mm, the voltage between each pair of plates is between 0.5-30 volts, and the current density is 10-3000A/m ² ; The anode is a reactive metal material, an inert metal material, an alloy or a non-metallic material; The cathode is a reactive metal material, an inert metal material or an alloy; (2), flocculation; (3), settlement; (4), filter. 2. A method for electrolytic treatment of oilfield sewage according to claim 1, characterized in that the electrodes in step (1) are two or more pairs; the electrodes are connected in series, parallel or a combination thereof . 3. A method for electrolytic treatment of oilfield sewage according to claim 1 or 2, characterized in that the distance between the electrodes is 0.5-30 mm. 4. A method for electrolytic treatment of oilfield sewage according to claim 1 or 2, characterized in that the voltage between the electrodes is 1-15 volts, and the current density is 500-3000A/m ² . 5. A method for electrolytic treatment of oilfield sewage according to claim 3, characterized in that the voltage between the electrodes is 1-15 volts, and the current density is 500-3000A/m ² .