A method for resource utilization of gas field water

Abstract

This invention discloses a method for the utilization of gas field water resources, specifically including the following steps: Step 1, gas field water treatment: adjusting the pH value to 11-12. Step 2, filtration: solid-liquid separation to obtain precipitate and treated gas field water. Step 3, electrolysis: the gas field water treated in Step 2 undergoes ion-exchange membrane electrolysis to obtain chlorine and hydrogen gas. Step 4, calcination: calcining the precipitate from Step 2 to constant weight. Step 5, dissolution: dissolving in water after calcination. Step 6, filtration: solid-liquid separation to obtain strontium carbonate precipitate and calcium hydroxide solution. Step 7, CO2 introduction: the calcium hydroxide solution reacts with CO2 to obtain calcium carbonate precipitate. This method achieves effective utilization of gas field water resources.

Description

Technical Field

[0001] This invention belongs to the field of wastewater treatment, specifically relating to a method for the utilization of water resources in gas fields. Background Technology

[0002] Gas field water refers to groundwater that is brought to the surface during natural gas extraction, mainly including associated water generated during drilling, well testing, well workover, and gas well production. Drainage operations are essential during gas field development to maintain stable natural gas production. With the extraction of natural gas, gas field water production has been increasing. By the end of 2021, all 37 gas fields were in operation, with 423 wells and a production capacity of 677.1 × 10⁴ m³ / d. Among these, 26 gas fields produced water, and 5 gas-bearing structures with formation water produced a total of 169 wells, producing 1536 m³ of water per day. In the past three years, the wells with a daily water production of more than 10 m3 are: Qili 50 Well (Kaizhou) 12.9 m3, Chi 11 Well (Liangping) 12-20 m3, Yunhe 1 Well (Dazhu) 20-23 m3, Wo 081-H1 (Dianjiang) 30 m3, Qili 024-2 Well (Dazhu) 35 m3, Qili 48 (Dazhu) 32-50 m3, Tiandong 12 Well (Liangping) 65 m3, and Yun'an 012-12 Well (Wanzhou) 50-216 m3. While gas field water is continuously produced, it has been noted that the discharge of gas field water can have certain environmental impacts. For example, water quality testing results from well Chi 037-6 show that the chloride content reached 3.48 × 10⁴ mg / L. Large amounts of chloride entering the soil can cause soil salinization, altering soil physicochemical properties and reducing fertility. Furthermore, because Cl⁻ is more reactive than NO₃⁻ and PO₄⁻, it inhibits the absorption of nitrogen and phosphorus by crops, thus reducing crop yields. Therefore, comprehensive utilization of gas field water resources, including the recovery of chlorine and other resources, is being considered. This would not only reduce the environmental harm caused by the discharge of gas field water but also increase its effective economic value.

[0003] Currently, there are three main methods for treating gas field water: formation reinjection, compliant discharge, and comprehensive resource utilization. Formation reinjection offers advantages such as large treatment capacity and low cost; however, due to complex geological structures in different regions, significant differences in water quality among wells, dispersed production sites, and difficulties in centralized collection and treatment, this method is prone to polluting the local environment and groundwater resources. Current technology for treating gas field water to meet discharge standards is relatively low, and the characteristic pollutants in the wastewater are difficult to identify. Therefore, specific treatment plans must be developed for each well, increasing the difficulty of this method and hindering standardized, large-scale treatment. Most importantly, neither of these two methods involves the recovery and utilization of valuable resources within the gas field water. Summary of the Invention

[0004] This invention provides a method for the utilization of water resources in gas fields, which enables the effective use of water resources in gas fields by extracting strontium resources in the form of strontium carbonate precipitation and producing hydrogen and chlorine by electrolysis of gas field water.

[0005] The technical solution adopted in this invention includes the following steps:

[0006] Step 1, Gas field water treatment: Add sodium carbonate to the gas field water and stir thoroughly to adjust the pH value to 11-12.

[0007] Step 2, Filtration: Solid-liquid separation yields precipitated and treated gas field water.

[0008] Step 3, Electrolysis to produce hydrogen: The treated gas field water is electrolyzed using an ion-exchange membrane to produce chlorine and hydrogen.

[0009] Step 4, calcination: calcinate the precipitate to constant weight.

[0010] Step 5, Dissolving: After calcination, quickly add a large amount of water to dissolve.

[0011] Step 6, Filtration: Solid-liquid separation yields strontium carbonate precipitate and calcium hydroxide solution.

[0012] Step 7: Introduce CO2: Calcium hydroxide solution reacts with CO2 to obtain calcium carbonate precipitate.

[0013] In a preferred embodiment, after adding Na₂CO₃ to the solution, the reaction reaches complete conversion, and excess sodium carbonate is present in the final solution. Preferably, 1% excess sodium carbonate is present.

[0014] A further improvement is to add KOH solution to the cathode chamber and treated gas field water to the anode chamber.

[0015] A further improvement is that the ion-exchange membrane electrolyzer includes an anode, a cathode, and an ion-exchange membrane, with the membrane positioned between the cathode and anode. The electrolyzer is divided into independent cathode and anode chambers. KOH solution is added to the cathode chamber, and treated gas field water is added to the anode chamber. Cations in the anode chamber can pass through the ion-exchange membrane to the cathode chamber. Hydrogen ions gain electrons on the cathode plate to produce hydrogen gas, and chloride ions lose electrons on the anode plate to produce chlorine gas, thus achieving the electrolysis of gas field water to produce hydrogen and chlorine. A negative pressure zone is formed above the cathode and anode chambers to collect hydrogen and chlorine gas separately.

[0016] A constant current of direct current is continuously applied to the cathode and anode to ensure that electrolysis continues stably.

[0017] A further improvement is the current density of 300-400 A / m. 2 .

[0018] A further improvement is to use natural gas power generation or natural gas residual pressure power generation to provide electricity for electrolysis.

[0019] A further improvement is that the calcination temperature is 900-1000℃.

[0020] A further improvement is to collect the CO2 produced during calcination in step 4 and use it as the gas introduced in step 7. This achieves CO2 recycling, ensuring that the entire process produces no additional CO2 emissions.

[0021] The technical effects of this invention are:

[0022] The method for extracting valuable elements from gas field water by electrolysis provided by this invention separates hydrogen and chlorine gases, avoiding mixing of gases produced during electrolysis. This invention extracts strontium from gas field water by precipitating strontium carbonate. Simultaneously, it removes calcium and magnesium ions from the gas field water, reducing the burden of calcium and magnesium ions on the ion exchange membrane and extending the membrane's lifespan.

[0023] This invention can be installed directly near the wellhead, eliminating the need for large-scale processing plants, and can recover and utilize excess natural gas as an energy resource at a very low cost. Attached Figure Description

[0024] Figure 1 This is a process route flowchart of an embodiment of the present invention.

[0025] Figure 2 This is a schematic diagram of an electrolytic cell. Detailed Implementation

[0026] In the following, the terms “comprising” or “may include” as used in various embodiments of the invention indicate the presence of an inventive function, operation, or element, and do not limit the addition of one or more functions, operations, or elements. Furthermore, as used in various embodiments of the invention, the terms “comprising,” “having,” and their cognates are intended only to indicate a specific feature, number, step, operation, element, component, or combination of the foregoing, and should not be construed as primarily excluding the presence of one or more other features, numbers, steps, operations, elements, components, or combinations of the foregoing, or adding one or more combinations of the foregoing.

[0027] The terminology used in the various embodiments of the invention is for the purpose of describing particular embodiments only and is not intended to limit the various embodiments of the invention. Unless otherwise specified, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the various embodiments of the invention pertain. The terms (such as those defined in commonly used dictionaries) are to be interpreted as having the same meaning as in the context of the relevant technical field and are not to be interpreted as having an idealized or overly formal meaning unless clearly defined in the various embodiments of the invention.

[0028] To make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the embodiments and accompanying drawings. The illustrative embodiments and descriptions of the present invention are only used to explain the present invention and are not intended to limit the present invention.

[0029] like Figure 1 As shown in the accompanying drawings and embodiments, the technical solution of the present invention will be described in detail below.

[0030] The chloride concentration in the sample was determined using the silver nitrate titration method according to the national standard (GB11896-89). Through repeated experiments and data processing, the chloride concentration in the gas field water was determined to be 50340.00 mg / L. Simultaneously, inductively coupled plasma atomic emission spectrometry (ICP-OES) was used for quantitative analysis of some elements, as shown in Table 1. Strontium resources are relatively abundant in the gas field water, and further in-depth research is necessary.

[0031] Table 1. Element content (mg / L) of some elements in gas field water.

[0032]

[0033] Example 1

[0034] Step 1: Gas Field Water Treatment

[0035] Add Na2CO3 to the gas field water to adjust the pH to 11-12, and stir thoroughly. The reaction equations involved in this process are as follows:

[0036] Ca 2+ +CO3 2- =CaCO3↓

[0037] Mg 2+ +CO3 2- =MgCO3↓

[0038] Sr 2+ +CO3 2- =SrCO3↓

[0039] Step 2, Filtering

[0040] Solid-liquid separation was achieved using vacuum filtration to obtain precipitated and treated gas field water. Qualitative filter paper with a maximum pore size of 10μm-15μm was used for vacuum filtration.

[0041] The composition of the precipitate was analyzed using X-ray fluorescence spectroscopy (XRF). The specific chemical composition is shown in Table 2. The XRF results show that the precipitate is mainly composed of calcium, followed by strontium, indicating that calcium and strontium resources in the gas field water were extracted by precipitation.

[0042] Table 2 Chemical composition of the precipitate (wt%)

[0043]

[0044]

[0045] Step 3: Electrolyze the gas field water treated in Step 2 to obtain hydrogen and chlorine.

[0046] like Figure 2 As shown, the ion-exchange membrane electrolyzer includes an independent cathode cell 5 and an anode cell 6, and a perfluorinated composite ion-exchange membrane 4 disposed between the cathode and the anode. The anode mesh plate 3 in the anode chamber is connected to the positive terminal of the DC power supply 1; the cathode plate 2 in the cathode chamber is connected to the negative terminal of the power supply.

[0047] The treated gas field water was added to the anode tank, and a 0.1 mol / L KOH solution was added to the cathode tank. The current density was set to 400 A / m. 2 The electrolysis time is 2.5 hours.

[0048] The following reaction occurs in the electrolytic cell:

[0049] Anode reaction:

[0050] 2Cl - -2e - →Cl2↑

[0051] Cathode reaction:

[0052] 2H2O+2e - →H₂↑+2OH⁻ -

[0053] Chlorine gas is produced at the anode, and hydrogen gas is produced at the cathode.

[0054] Step 4: Calcination

[0055] The precipitate obtained in step 2 was calcined at 950°C to constant weight, and the CO2 produced during calcination was collected.

[0056] The reaction formulas involved in the process are as follows:

[0057] CaCO3=CaO+CO2↑

[0058] Step 5: Dissolve

[0059] After calcination, quickly add a large amount of water to dissolve it.

[0060] Step 6: Filtering

[0061] Solid-liquid separation was achieved using vacuum filtration to obtain strontium carbonate precipitate and calcium hydroxide solution. Qualitative filter paper with a maximum pore size of 10 μm-15 μm was used for vacuum filtration.

[0062] Step 7: Introduce CO2

[0063] When the calcium hydroxide solution is passed through the CO2 collected in step 4, the solution becomes cloudy, and calcium carbonate precipitate is obtained.

[0064] Example 2

[0065] Step 1: Gas Field Water Treatment

[0066] Add Na2CO3 to the gas field water to adjust the pH to 11-12 and stir thoroughly.

[0067] Step 2, Filtering

[0068] Solid-liquid separation is achieved by using vacuum filtration to obtain precipitated and treated gas field water.

[0069] Step 3: Electrolysis yields hydrogen and chlorine gas.

[0070] The ion-exchange membrane electrolyzer includes an anode, a cathode, and an ion-exchange membrane. The ion-exchange membrane is disposed between the cathode and the anode, and the ion-exchange membrane electrolyzer is divided into independent cathode chambers and anode chambers.

[0071] The treated gas field water was added to the anode tank, and a 1 mol / L KOH solution was added to the cathode tank. The current density was set to 300 A / m. 2 The electrolysis time is 2.5 hours.

[0072] A negative pressure zone is formed above the cathode chamber and anode chamber to collect hydrogen and chlorine gas separately.

[0073] Step 4: Calcination

[0074] The obtained strontium carbonate precipitate was calcined at 1000℃ to constant weight.

[0075] Step 5: Dissolve

[0076] After calcination, quickly add a large amount of water to dissolve it.

[0077] Step 6: Filtering

[0078] Solid-liquid separation was achieved using vacuum filtration to obtain strontium carbonate and calcium hydroxide solutions. Qualitative filter paper with a maximum pore size of 10 μm–15 μm was used for vacuum filtration.

[0079] Step 7: Introduce CO2

[0080] When CO2 is passed through a calcium hydroxide solution, the solution becomes cloudy, and calcium carbonate precipitate is obtained.

[0081] In a preferred embodiment, the ion-exchange membrane electrolyzer can be directly located near the wellhead and can utilize sufficient electrical energy provided by natural gas power generation and natural gas residual pressure power generation.

[0082] Gas field water is generally characterized by its wide distribution, multiple producing layers, abundant resources, high quality, simultaneous production of gas and water, and ease of development. Adopting a comprehensive treatment method for gas field water resources can not only reduce the environmental impact of wastewater but also achieve efficient utilization of gas field water resources, increasing their effective economic value and facilitating the development and utilization of valuable resources within the gas field water. The gas field water electrolysis treatment and resource utilization method proposed in this patent application uses direct current to separate the cathode and anode to produce hydrogen and chlorine gas. This technology can utilize renewable energy power, producing no CO2 emissions, thus obtaining truly "green hydrogen." This not only reduces the environmental harm caused by the discharge of gas field water but also increases its effective economic value. In practical operation, natural gas power generation and natural gas residual pressure power generation provide sufficient electricity for gas field water electrolysis, enabling the recovery and utilization of natural gas energy and reducing energy resource losses. Placing the gas field water electrolysis device directly near the wellhead allows for the extraction and utilization of valuable gas field water resources, further realizing the comprehensive utilization of resources and energy.

[0083] Those skilled in the art will understand that the above embodiments are specific examples of implementing the present invention, and in practical applications, various changes in form and detail may be made without departing from the spirit and scope of the present invention.

Claims

1. A method for the utilization of water resources in a gas field, characterized in that, Including the following step; Step 1, Gas field water treatment: Add sodium carbonate to the gas field water and stir to adjust the pH value to 11-12; Step 2, Filtration: Solid-liquid separation yields precipitated and treated gas field water; Step 3, Electrolysis: The gas field water treated in Step 2 is subjected to ion-exchange membrane electrolysis to obtain chlorine and hydrogen. Step 4, calcination: calcinate the precipitate from step 2 to constant weight; Step 5, Dissolving: Add water to dissolve after calcination; Step 6, Filtration: Solid-liquid separation yields strontium carbonate precipitate and calcium hydroxide solution; Step 7: Introduce CO2: Calcium hydroxide solution reacts with CO2 to obtain calcium carbonate precipitate.

2. The method according to claim 1, characterized in that, step In step 1, after adding Na2CO3 to the solution, the reaction reaches complete conversion, and excess sodium carbonate is present in the final solution.

3. The method according to claim 1, characterized in that, In step 3, KOH solution is added to the cathode chamber and treated gas field water is added to the anode chamber.

4. The method according to claim 1, characterized in that, In step 3, the ion membrane electrolysis includes an anode, a cathode, and an ion membrane, with the ion membrane disposed between the cathode and the anode.

5. The method according to claim 1, characterized in that, In step 3, the current density for gas field water electrolysis is 300-400 A / m. 2 .

6. The method according to claim 1, characterized in that, In step 3, electricity is supplied for electrolysis using natural gas power generation or natural gas residual pressure power generation.

7. The method according to claim 1, characterized in that, In step 4, the calcination temperature is 900-1000℃.

8. The method according to claim 1, characterized in that, The CO2 produced by calcination in step 4 is collected and used as the gas introduced in step 7.

9. The method according to claim 1, characterized in that: A negative pressure zone is formed above the cathode chamber and anode chamber to collect hydrogen and chlorine gas separately.

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