Device and method for treating gas field produced water containing liquid hydrocarbon

Abstract

The invention belongs to the technical field of oil field water treatment, and particularly relates to a treatment system and method for gas field produced water containing liquid hydrocarbon. The treatment system comprises a separation device, a settling tank and a scaling device which are communicated in sequence. The treatment method comprises the following steps: 1) separating the liquid hydrocarbon-containing gas field produced water in a separation device to obtain a water-hydrocarbon mixed solution; 2) mixing the water-hydrocarbon mixture and crude oil according to a volume ratio of (3-1): 1, conveying the mixture to a settling tank, separating a crude oil liquid hydrocarbon mixture and settling water through gravity settling, and externally conveying the crude oil liquid hydrocarbon mixture through a pipeline; 3, the settling water is conveyed into a scaling device, an iron removal agent, a calcium and magnesium removal agent and a demulsifying agent are sequentially added, then precipitation reaction is carried out, and reinjection water is obtained on the upper layer. Liquid hydrocarbon can be recycled, meanwhile, the hydrocarbon content in water is reduced, the settling water is treated through a treating agent, and the requirement of oilfield reinjection water is met.

Description

Technical Field

[0001] This invention belongs to the field of oilfield water treatment technology, specifically relating to a treatment device and method for produced water from gas fields containing liquid hydrocarbons. Background Technology

[0002] After the extracted crude oil undergoes oil-water separation, the separated water still contains dissolved liquid hydrocarbons. Direct discharge into the environment would cause environmental pollution and waste of water resources. Therefore, the extracted water can be treated and modified for use in oilfield reinjection.

[0003] Water quality modification has been developed in my country for many years and has shown good results in oilfield reinjection water, making it a relatively mature technology. However, due to the significant differences in oilfield wastewater, it is difficult to find a single agent or process suitable for all wastewater treatment systems. Therefore, it is necessary to develop new agents and improve processes specifically tailored to the actual conditions of oilfield sites to better meet the needs of oilfield development. How to reduce the oil content of produced water is a problem that existing technologies need to address.

[0004] Jin Hua et al. conducted on-site trials of water quality modification technology at the Guan-2 phase wastewater treatment plant in Dagang Oilfield. They added water quality modifiers and purifying agents to the original treatment system to adjust the pH value of the wastewater and achieve water purification. The sludge discharged during the process was filtered into oil-containing sludge cakes in a sludge tank for further treatment. After on-site adjustments, the oil content in the wastewater reached ≤5 mg / L, meeting the reinjection standard, and the median suspended solids particle size basically met the requirements. In the Tarim Hade 4 oilfield of Tarim Oilfield, clean water and wastewater are treated separately and then reinjected separately. This reinjection method increases surface costs, operational workload, and the possibility of corrosion and scaling in the injected water. Liu Shijing et al. mixed wastewater and clean water in a 6:4 ratio, adjusted the pH value of the wastewater system to induce scaling, added flocculants to remove sediment, and added bactericides, corrosion inhibitors, and scale inhibitors before external transportation. Indoor studies showed that the oil content and suspended solids content of the treated mixed water met the standards.

[0005] CN103183425A describes a water treatment technology using oil flotation, which employs the following technical solution: 300-2000 PPM of water-insoluble organic matter is added to the water to be treated and dispersed mechanically. Next, 30-300 PPM of coagulant and 2-20 PPM of flocculant are added according to conventional water treatment methods. These react to form flocs that adsorb impurities in the water and separate them from the water, thus completing the water treatment process. Finally, the discharged sludge is squeezed and washed to recover the added water-insoluble organic matter, allowing it to be recycled.

[0006] Although the above methods can meet the reinjection requirements after produced water treatment, the liquid hydrocarbons cannot be separated and transported with the crude oil, resulting in a waste of resources. Summary of the Invention

[0007] The purpose of this invention is to provide a treatment device for produced water from gas fields containing liquid hydrocarbons, overcoming the aforementioned technical problems in the prior art.

[0008] The purpose of this invention is to provide a method for treating produced water from gas fields containing liquid hydrocarbons, which involves recovering the liquid hydrocarbons and treating the produced water before reinjection.

[0009] Therefore, the technical solution provided by the present invention is as follows: A treatment system for produced water from a gas field containing liquid hydrocarbons includes a separation unit, a settling tank, and a scaling device connected in sequence.

[0010] The separation device is a three-phase separation device.

[0011] A method for treating produced water from a gas field containing liquid hydrocarbons, employing a treatment system for produced water from such a gas field, includes the following steps: Step 1) Produced water from gas fields containing liquid hydrocarbons enters a separation device for separation to obtain a water-hydrocarbon mixture; Step 2) The water-hydrocarbon mixture and crude oil are mixed at a volume ratio of 3-1:1 and then transported to a settling tank. The crude oil-liquid hydrocarbon mixture and settling water are separated by gravity settling. The crude oil-liquid hydrocarbon mixture is then transported out through pipelines. Step 3) The settled water is transported to the scale collector, and iron removal agent, calcium and magnesium removal agent and demulsifier are added in sequence. After the sedimentation reaction, the upper layer is the reinjection water. The mass of water in the water-hydrocarbon mixture obtained in step 1) is less than 0.4%.

[0012] In step 2), the mixing time of the water-hydrocarbon mixture and crude oil is 35-45 minutes.

[0013] In step 2), the hydrocarbon mixture and crude oil are mixed and then transported to a settling tank at a flow rate of 1.5-2 L / h for separation.

[0014] The iron removal agent described in step 3) is transported at a flow rate of 0.4-0.5 g / h.

[0015] The flow rate of the calcium and magnesium removal agent described in step 3) is 0.3-0.4 g / h.

[0016] The demulsifier mentioned in step 3) is hyperbranched polyethyleneimine, and the delivery flow rate is 0.3-0.4 g / h.

[0017] The demulsifier is obtained by reacting a hyperbranched polymer with an amphiphilic surfactant.

[0018] The beneficial effects of this invention are: The present invention provides a method for treating produced water from gas fields containing liquid hydrocarbons. This method involves separating the water-containing liquid hydrocarbons and crude oil into sediment, recovering the liquid hydrocarbons, and reducing the hydrocarbon content in the water. The sediment is then treated with an iron removal agent, a calcium and magnesium removal agent, and a hyperbranched emulsifier to meet the requirements for oilfield reinjection water. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of one embodiment of the processing system of the present invention; Figure 2 This is the result of liquid hydrocarbon composition analysis in an example of total hydrocarbon analysis using a gas chromatograph.

[0020] In the diagram: 1. Separation device; 2. Settling tank; 3. Scale collector. Detailed Implementation

[0021] The following specific embodiments illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification.

[0022] Exemplary embodiments of the present invention will now be described with reference to the accompanying drawings. However, the present invention may be embodied in many different forms and is not limited to the embodiments described herein. These embodiments are provided to fully and completely disclose the invention and to fully convey its scope to those skilled in the art. The terminology used in the exemplary embodiments illustrated in the drawings is not intended to limit the invention. In the drawings, the same units / elements are referred to by the same reference numerals.

[0023] Unless otherwise stated, the terms used herein (including technical terms) have their common meaning as understood by one of ordinary skill in the art. Furthermore, it is understood that terms defined in commonly used dictionaries should be understood to have a meaning consistent with the context of their relevant field, and not to be interpreted as having an idealized or overly formal meaning.

[0024] Example 1 This embodiment provides a treatment system for produced water from a gas field containing liquid hydrocarbons, comprising a separation device 1, a settling tank 2, and a scaling device 3 connected in sequence. Figure 1 As shown.

[0025] Working principle of this invention: Water, liquid hydrocarbons, and crude oil are separated from the produced water. The lower layer of water contains liquid hydrocarbons. This hydrocarbon-containing water is sent to separation unit 1 and settled in a sealed environment for 20-30 minutes to obtain water-containing liquid hydrocarbons with a water mass of less than 0.4%. The water-containing liquid hydrocarbons and crude oil are mixed at a certain volume ratio and then transported to settling tank 2 to separate the liquid hydrocarbons and settling water. The settling water is mixed with treated crude oil and transported externally. The settling water is then introduced into scale collector 3. A treatment agent is added to the scale collector to precipitate iron, calcium, and magnesium ions and demulsify the water. The treated water is then reinjected into the oilfield.

[0026] Example 2 Based on Example 1, this example provides a treatment system for produced water from a gas field containing liquid hydrocarbons, wherein the separation device 1 is a three-phase separation device.

[0027] Three-phase separation devices are based on the buoyancy properties of the liquids to be separated, and achieve separation through the interaction of gravity, mechanics and centrifugal force, resulting in high separation efficiency.

[0028] Example 3 This embodiment provides a method for treating produced water from a gas field containing liquid hydrocarbons, including the following steps: Step 1) Produced water from gas fields containing liquid hydrocarbons enters separation device 1 for separation to obtain a water-hydrocarbon mixture; Step 2) The water-hydrocarbon mixture and crude oil are mixed at a volume ratio of 3-1:1 and then transported to settling tank 2. The crude oil-liquid hydrocarbon mixture and settling water are separated by gravity settling. The crude oil-liquid hydrocarbon mixture is then transported out through pipeline. Step 3) The settled water is transported to the scale collector 3, and iron removal agent, calcium and magnesium removal agent and demulsifier are added in sequence. After the sedimentation reaction, the upper layer is the reinjected water. Example 4 Based on Example 3, this example provides a method for treating produced water from a gas field containing liquid hydrocarbons, including the following steps: Step 1) Produced water from gas fields containing liquid hydrocarbons enters a three-phase separation device for sealed sedimentation for 20 minutes to obtain a water-hydrocarbon mixture; Step 2) Mix the water-hydrocarbon mixture and crude oil at a volume ratio of 1:1 for 35 minutes, and then transport it to settling tank 2 at a flow rate of 2L / h for separation. The crude oil-liquid hydrocarbon mixture and settling water are separated by gravity settling. The crude oil-liquid hydrocarbon mixture is then transported out through pipeline. Step 3) The settled water is transported to the scaler 3, and iron removal agent, calcium and magnesium removal agent and demulsifier are added in sequence. After the precipitation reaction, the upper layer is the reinjected water. The iron removal agent is transported at a rate of 0.4 g / h; the calcium and magnesium removal agent is transported at a rate of 0.3 g / h; and the hyperbranched demulsifier is transported at a rate of 0.3 g / h. In this embodiment, the iron removal agent is sodium hypochlorite, the calcium and magnesium removal agent is trisodium phosphate, the hyperbranched demulsifier is hyperbranched polyethyleneimine, the amount of sodium hypochlorite added to the produced water is 200 mg / L, the amount of trisodium phosphate added to the produced water is 150 mg / L, and the amount of hyperbranched polyethyleneimine added to the produced water is 120 mg / L.

[0029] Among them, the analysis results of liquid hydrocarbons in the produced water of gas fields containing liquid hydrocarbons are as follows: Figure 2 As shown, the C6 content is the highest at 20.2%, the content of components > C30 is 0%, and the saturated hydrocarbon content is 96.06%.

[0030] Example 5 Based on Example 3, this example provides a method for treating produced water from a gas field containing liquid hydrocarbons, including the following steps: Step 1) Produced water from gas fields containing liquid hydrocarbons enters a three-phase separation device for sealed sedimentation for 30 minutes to obtain a water-hydrocarbon mixture; Step 2) Mix the water-hydrocarbon mixture and crude oil at a volume ratio of 3:1 for 45 minutes, and then transport it to settling tank 2 at a flow rate of 1.8 L / h for separation. The crude oil-liquid hydrocarbon mixture and settling water are separated by gravity settling. The crude oil-liquid hydrocarbon mixture is transported out through pipeline. Step 3) The settled water is transported to the scaler 3, and iron removal agent, calcium and magnesium removal agent and demulsifier are added in sequence. After the precipitation reaction, the upper layer is the reinjected water. The iron removal agent is transported at a rate of 0.4 g / h; the calcium and magnesium removal agent is transported at a rate of 0.3 g / h; and the hyperbranched demulsifier is transported at a rate of 0.4 g / h.

[0031] In this embodiment, the iron removal agent is sodium hypochlorite, the calcium and magnesium removal agent is trisodium phosphate, and the hyperbranched demulsifier is described in patent CN202411078805.8.

[0032] Example 6 Based on Example 3, this example provides a method for treating produced water from a gas field containing liquid hydrocarbons, including the following steps: Step 1) Produced water from gas fields containing liquid hydrocarbons enters a three-phase separation device for sealed sedimentation for 25 minutes to obtain a water-hydrocarbon mixture; Step 2) Mix the water-hydrocarbon mixture and crude oil at a volume ratio of 2:1 for 40 minutes, and then transport it to settling tank 2 at a flow rate of 1.5 L / h for separation. The crude oil liquid hydrocarbon mixture and settling water are separated by gravity settling. The crude oil liquid hydrocarbon mixture is transported out through pipeline. Step 3) The settled water is transported to the scale collector 3, and iron removal agent, calcium and magnesium removal agent and demulsifier are added in sequence. After the precipitation reaction, the upper layer is the reinjected water. The iron removal agent is transported at a rate of 0.4 g / h; the calcium and magnesium removal agent is transported at a rate of 0.4 g / h; and the demulsifier is transported at a rate of 0.4 g / h.

[0033] In this embodiment, the iron removal agent is sodium hypochlorite, the calcium and magnesium removal agent is trisodium phosphate, and the demulsifier is hyperbranched polyethyleneimine.

[0034] To further illustrate the effects of the present invention, the samples were treated using the methods of Examples 4-6 in this embodiment. The sample was crude oil from Qing 1 Station, with a water content of 4.6%.

[0035] Step 1) The treated water-hydrocarbon mixture is shown in Table 1. Table 1 shows that the produced water from Qing 1 station has a total mineralization of 13130 ​​mg / L, a pH of 6.2 (slightly acidic), and a Na+ content of... + K + The total concentration is 3664 mg / L, the total Fe content is 56 mg / L, and the aqueous form is calcium chloride.

[0036] Table 1. Component analysis results of produced water from Qing 1 Station

[0037] The reinjection water treated using the method of Example 4 contained 31.2 mg / L of oil, 15.3 mg / L of suspended solids, and 0.1% water content in the crude oil. The reinjection water treated using the method of Example 5 contained 31.5 mg / L of oil, 16.4 mg / L of suspended solids, and 0.2% water content in the crude oil. The reinjection water treated using the method of Example 6 contained 30.5 mg / L of oil, 14.8 mg / L of suspended solids, and 0.2% water content in the crude oil. The expected results were achieved.

[0038] The above examples are merely illustrative of the present invention and do not constitute a limitation on the scope of protection of the present invention. All designs that are the same as or similar to the present invention are within the scope of protection of the present invention.

Claims

1. A treatment system for produced water from a gas field containing liquid hydrocarbons, characterized in that: It includes a separation device, a settling tank, and a scale collector connected in sequence.

2. The treatment system for produced water from a gas field containing liquid hydrocarbons according to claim 1, characterized in that: The separation device is a three-phase separation device.

3. A method for treating produced water from a gas field containing liquid hydrocarbons, employing the produced water treatment system for gas fields containing liquid hydrocarbons as described in claim 1, characterized in that: Includes the following steps: Step 1) Produced water from gas fields containing liquid hydrocarbons enters a separation device for separation to obtain a water-hydrocarbon mixture; Step 2) The water-hydrocarbon mixture and crude oil are mixed at a volume ratio of 3-1:1 and then transported to a settling tank. The crude oil-liquid hydrocarbon mixture and settling water are separated by gravity settling. The crude oil-liquid hydrocarbon mixture is then transported out through pipelines. Step 3) The settled water is transported to the scale collector, and iron removal agent, calcium and magnesium removal agent and demulsifier are added in sequence. After the sedimentation reaction, the upper layer is the reinjection water.

4. The method for treating produced water from a gas field containing liquid hydrocarbons according to claim 3, characterized in that: The mass of water in the water-hydrocarbon mixture obtained in step 1) is less than 0.4%.

5. A method for treating produced water from a gas field containing liquid hydrocarbons according to claim 3, characterized in that: In step 2), the mixing time of the water-hydrocarbon mixture and crude oil is 35-45 minutes.

6. A method for treating produced water from a gas field containing liquid hydrocarbons according to claim 3, characterized in that: In step 2), the hydrocarbon mixture and crude oil are mixed and then transported to a settling tank at a flow rate of 1.5-2 L / h for separation.

7. A method for treating produced water from a gas field containing liquid hydrocarbons according to claim 3, characterized in that: The iron removal agent described in step 3) is transported at a flow rate of 0.4-0.5 g / h.

8. A method for treating produced water from a gas field containing liquid hydrocarbons according to claim 3, characterized in that: The flow rate of the calcium and magnesium removal agent described in step 3) is 0.3-0.4 g / h.

9. A method for treating produced water from a gas field containing liquid hydrocarbons according to claim 3, characterized in that: The demulsifier mentioned in step 3) is hyperbranched polyethyleneimine, and the delivery flow rate is 0.3-0.4 g / h.

10. A method for treating produced water from a gas field containing liquid hydrocarbons according to claim 3, characterized in that: The demulsifier is obtained by reacting a hyperbranched polymer with an amphiphilic surfactant.

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