Composite hardness removal agent suitable for high hardness aqueous systems and method of use thereof

Abstract

The application provides a composite hardness removal agent suitable for a high-hardness aqueous system and a use method thereof, and the composite hardness removal agent comprises lime, sodium sulfate, sodium sulfite and sodium carbonate. The composite hardness removal agent is suitable for a high-hardness aqueous system of a fracturing flowback fluid in an oil and gas field, can effectively avoid the risk of calcium sulfate scaling while significantly reducing the cost of the agent, realizes deep hardness removal, and can simultaneously remove dissolved oxygen, so as to solve multiple challenges such as cost, scaling, effect and system corrosion in one station.

Description

Technical Field

[0001] This invention relates to the field of water treatment technology, and provides a composite hardening remover suitable for high-hardness aqueous systems of fracturing flowback fluid in oil and gas fields and its application method. In particular, it relates to a composite hardening remover for treating high-hardness, high-mineralization aqueous systems and its application method, which is especially suitable for oil and gas field flowback fluids, brine refining and industrial circulating water systems. Background Technology

[0002] Hydraulic fracturing is a key technology for improving oil and gas field recovery, but it generates a large amount of fracturing flowback fluid. This wastewater has a complex composition and typically has high hardness (with Ca2+ as a key component). 2+ Mg 2+ It is characterized by high mineralization, high chemical oxygen demand (COD), and the presence of various additive residues. In order to meet environmental protection requirements and water resource recycling, fracturing flowback fluid must undergo deep treatment, among which reducing hardness (softening) is a crucial step before reuse or compliant discharge.

[0003] High-hardness aqueous systems, especially calcium chloride-based oil and gas field flowback fluids with calcium ion concentrations exceeding 20,000 mg / L, pose a significant challenge in industrial water treatment. Existing technologies commonly employ the "liquid alkali-sodium carbonate" method for hardening removal. While effective, this method suffers from the following drawbacks: ① High cost: Sodium carbonate is expensive, accounting for a large proportion of reagent costs when treating extremely hard water. ② Corrosion risk: Dissolved oxygen in the water can corrode metal equipment, and traditional hardening agents lack oxygen removal capabilities. ③ Limited effectiveness: It only removes hardness and cannot simultaneously address oxygen corrosion. ④ Requires multiple systems for distributed dosing, resulting in complex and demanding operating procedures.

[0004] Although some technologies propose using sodium sulfate to partially replace sodium carbonate to reduce costs, the introduction of sulfate ions may increase the risk of calcium sulfate scaling, and it cannot deeply remove hardness or solve the problems of corrosion and water discoloration caused by high dissolved oxygen.

[0005] Therefore, there is an urgent need for a low-cost, multifunctional, and highly efficient hard removal technology. Summary of the Invention

[0006] In response to the problems mentioned in the background art, the main objective of this invention is to provide a composite hardening remover suitable for high-hardness water-based systems of fracturing flowback fluid in oil and gas fields and its application method. This method can significantly reduce the cost of the reagent, effectively avoid the risk of calcium sulfate scaling, achieve deep hardening removal, and simultaneously remove dissolved oxygen, thus providing a one-stop solution to multiple challenges such as cost, scaling, effectiveness, and system corrosion.

[0007] In a first aspect, the present invention provides a composite hardening remover suitable for high-hardness aqueous systems of fracturing flowback fluids in oil and gas fields, comprising lime, sodium sulfate, sodium sulfite, and sodium carbonate.

[0008] In some embodiments, the composite hardening agent comprises, by weight: 10-40 parts lime, 20-60 parts sodium sulfate, 5-25 parts sodium sulfite, and 15-50 parts sodium carbonate.

[0009] In some embodiments, the composite hardening agent has a sodium sulfate to sodium sulfite weight ratio of (8:1) to (1:1), which optimally balances cost and synergistic effects.

[0010] In some embodiments, the weight ratio of sodium sulfate to sodium sulfite is 8:1, 7:1, 6:1, 5:1, 4:1, 3:1, 2:1, 1:1, or any two of the above values ​​forming any one of the ranges.

[0011] In some embodiments, the lime is 10-40 parts, preferably 10 parts, 15 parts, 20 parts, 25 parts, 30 parts, 35 parts, 30 parts, or any two of the above values ​​forming a range.

[0012] In some embodiments, the sodium sulfate is any one of the ranges of 20 parts, 25 parts, 30 parts, 35 parts, 40 parts, 45 parts, 50 parts, 55 parts, 60 parts, or any two of the above values.

[0013] In some embodiments, the sodium sulfite is 5 parts, 10 parts, 15 parts, 20 parts, 25 parts, or any two of the above values ​​forming a range.

[0014] In some embodiments, the sodium carbonate is any one of the ranges of 15 parts, 20 parts, 25 parts, 30 parts, 35 parts, 40 parts, 45 parts, 50 parts, or any two of the above values.

[0015] Secondly, this invention provides a method for using a composite hardening remover suitable for high-hardness aqueous systems of fracturing flowback fluids in oil and gas fields. The method includes adding the composite hardening remover described in this invention to the fracturing flowback fluid; conducting a precipitation reaction under stirring conditions; and separating the resulting precipitate. The method described in this invention can simultaneously reduce the hardness, dissolved oxygen content, and scaling tendency of the aqueous system.

[0016] In some embodiments, the dosage is 50~100g / L of water sample, preferably 50g / L, 60g / L, 70g / L, 80g / L, 90g / L, 100g / L, or any two of the above values ​​forming a range.

[0017] In some embodiments, the calcium ion concentration in the high-hardness aqueous system of the oil and gas field fracturing flowback fluid is greater than 20,000 mg / L.

[0018] In some embodiments, the order of addition of the composite hardening agent is as follows: first add lime, then add sodium sulfate and sodium sulfite, and finally add sodium carbonate.

[0019] In some embodiments, the sodium sulfate may be added in steps, for example, 30%-50% of its total calculated amount may be added first, and after reacting for 5-30 minutes, the remaining sodium sulfate may be added.

[0020] In some embodiments, the components of the composite hardening agent are premixed as a solid powder mixture.

[0021] In some embodiments, the composite hardening agent is prepared as a slurry or solution and added sequentially during use.

[0022] Beneficial effects

[0023] (1) Synergistic cost reduction: By replacing expensive sodium carbonate with inexpensive sodium sulfate and utilizing the unique properties of sodium sulfite, the overall reagent cost is significantly reduced compared to the traditional "lime-sodium carbonate" method. Through the synergistic effect of lime, sodium sulfate, sodium sulfite and sodium carbonate, a triple hardness removal mechanism of "precipitation-adsorption-flocculation" is formed, which can stably reduce the total hardness of the effluent to below 50 mg / L (calculated as CaCO3).

[0024] (2) Multifunctional integration: Lime provides OH - Removes magnesium hardness and adjusts pH; sodium sulfate provides SO4. 2- , with Ca 2+ The formation of calcium sulfate precipitate significantly reduces calcium ion concentration at extremely low cost; sodium sulfite, as an oxygen scavenger, effectively removes dissolved oxygen from water, fundamentally inhibiting oxygen corrosion of equipment. Simultaneously, it introduces SO3... 2- With Ca 2+ Calcium sulfite precipitate is formed, participating in the co-precipitation process and altering the crystal form of the precipitate, making it more porous and easier to remove; Sodium carbonate provides CO3. 2- Deep hardening is carried out to ensure that the residual hardness of the effluent meets the standard.

[0025] (3) Scale inhibition and corrosion prevention: Sodium sulfite's deoxygenation effect directly prevents corrosion. Simultaneously, multiple anions (SO4)... 2- SO3 2- CO3 2- The competition and synergy between the substances disrupt the crystallization process of single calcium carbonate scale, resulting in a mixed loose precipitate that is not easy to adhere and form scale, thus achieving the scale inhibition effect.

[0026] (4) This invention innovatively introduces sodium sulfite, whose sulfite ions (SO3) 2-This agent can act as a crystal growth disruptor, adsorbing onto the active growth sites of calcium sulfate crystals, causing lattice distortion and preventing the formation of stable, dense scale, thus fundamentally solving the secondary pollution problem caused by the introduction of sulfate ions. Using sodium sulfite as a chemical deoxygenator can reduce dissolved oxygen concentration to below 0.1 mg / L, effectively controlling equipment corrosion and effluent color. This single agent simultaneously solves three major technical challenges: hardening, scale inhibition, and deoxygenation, simplifying the treatment process and dosing system.

[0027] (5) Synergistic effect: Lime provides OH - It removes magnesium hardness; sodium sulfate participates in hardness removal while reducing costs; sodium sulfite has three effects: it acts as an oxygen scavenger, its reaction product sodium sulfate can continue to be used for hardness removal, and it can also act as an interfering agent for calcium sulfate crystallization. Sodium carbonate performs deep hardness removal. The combination of the four components produces a synergistic effect of "1+1+1+1>4", and its treatment effect and economic benefits are far beyond what can be achieved by simply adding the components together. Addressing the fluctuating water quality of fracturing flowback fluid, an optimized dosing sequence and a potential dynamic control system ensure excellent treatment results under different operating conditions.

[0028] Terminology Explanation

[0029] Certain embodiments of the invention will now be described in detail, examples of which are illustrated by the accompanying structural and chemical formulas. The invention is intended to cover all alternatives, modifications, and equivalents, all of which are included within the scope of the invention as defined in the claims. Those skilled in the art will recognize that many similar or equivalent methods and materials can be used to practice the invention. The invention is by no means limited to the methods and materials described herein. In the event that one or more of the incorporated documents, patents, and similar materials differ from or contradict this application (including, but not limited to, defined terminology, application of terminology, described techniques, etc.), this application shall prevail.

[0030] It should be further appreciated that certain features of the invention, for clarity, have been described in multiple independent embodiments, but may also be provided in combination in a single embodiment. Conversely, various features of the invention, for brevity, have been described in a single embodiment, but may also be provided individually or in any suitable sub-combination.

[0031] Unless otherwise stated, all technical terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art. All patents and publications related to this invention are incorporated herein by reference in their entirety.

[0032] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0033] In the following content, all numbers disclosed herein, whether or not they use words such as "approximately" or "about," are approximate values. The value of each number may vary by 1%, 2%, 5%, 7%, 8%, 10%, 15%, or 20%. Whenever a number with a value of N is disclosed, any numbers with values ​​of N+ / -1%, N+ / -2%, N+ / -3%, N+ / -5%, N+ / -7%, N+ / -8%, N+ / -10%, N+ / -15%, or N+ / -20% will be explicitly disclosed, where "+ / -" indicates addition or subtraction. Detailed Implementation

[0034] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. The specific embodiments described herein are for illustrative purposes only and are not intended to limit the invention in any way. Furthermore, descriptions of well-known structures and techniques are omitted in the following description to avoid unnecessarily obscuring the concepts of this disclosure. Such structures and techniques have also been described in many publications.

[0035] All reagents used in this invention can be purchased commercially or prepared by the methods described in this invention.

[0036] Preparation Example 1

[0037] Weigh each component according to the following weight ratio and mix them evenly to prepare composite hardening agent A.

[0038] Lime: 15 parts, Sodium sulfate: 55 parts, Sodium sulfite: 15 parts, Sodium carbonate: 15 parts

[0039] Preparation Example 2

[0040] Weigh each component according to the following weight ratio and mix them evenly to prepare composite hardening agent B.

[0041] Lime: 25 parts, Sodium sulfate: 45 parts, Sodium sulfite: 15 parts, Sodium carbonate: 30 parts

[0042] Preparation Example 3

[0043] Weigh each component according to the following weight ratio and mix them evenly to prepare composite hardening agent C.

[0044] Lime: 30 parts, Sodium sulfate: 40 parts, Sodium sulfite: 5 parts, Sodium carbonate: 25 parts

[0045] Preparation Example 4

[0046] Weigh each component according to the following weight ratio and mix them evenly to prepare composite hardening agent C.

[0047] Lime: 30 parts, Sodium sulfate: 20 parts, Sodium sulfite: 20 parts, Sodium carbonate: 20 parts

[0048] Preparation of Comparative Example 1

[0049] Weigh each component according to the following weight ratio and mix them evenly to prepare composite hardening agent a.

[0050] Sodium hydroxide: 2 parts, sodium carbonate: 50 parts

[0051] Preparation of Comparative Example 2

[0052] Weigh each component according to the following weight ratio and mix them evenly to prepare composite hardening agent b.

[0053] Lime: 25 parts, Sodium sulfate: 45 parts, Sodium carbonate: 30 parts

[0054] Preparation of Comparative Example 3

[0055] Weigh each component according to the following weight ratio and mix them evenly to prepare composite hardening agent c.

[0056] Lime: 25 parts, Sodium carbonate: 30 parts

[0057] Application Example 1: Treatment of High-Hardness Fracturing Flowback Fluid

[0058] A sample of fracturing flowback fluid from an oilfield was taken, with the following water quality: Ca 2+ 32365 mg / L, Mg 2+ 1,200 mg / L, dissolved oxygen: 5.5 mg / L, pH: 6.96

[0059] Processing steps:

[0060] 1) Take 1L of water sample, add 60g of compound hardening agent while stirring, and react for 50 minutes.

[0061] 2) Add 3 mg / LPAM and stir to flocculate for 10 minutes.

[0062] 3) Adjust the pH and let it stand to precipitate, then take the supernatant for testing.

[0063] The test results are shown in Table 1 below:

[0064]

[0065] Compared with Comparative Example 1, the present invention (especially Example 2) significantly reduces costs while maintaining slightly higher but still excellent residual hardness, and completely removes dissolved oxygen, making the precipitate easier to handle.

[0066] Compared to Comparative Examples 2 and 3, the present invention, due to the addition of sodium sulfite, achieves the additional effect of deep deoxygenation. Simultaneously, the introduction of sulfite ions alters the precipitation characteristics and reduces residual hardness. This demonstrates that the addition of sodium sulfite brings unexpected synergistic effects, rather than a simple additive effect.

[0067] The method of this invention has been described through preferred embodiments. Those skilled in the art will readily be able to modify or appropriately alter and combine the methods and applications described herein within the scope, spirit, and context of this invention to implement and apply the technology of this invention. Those skilled in the art can refer to the content herein to appropriately improve process parameters. It should be particularly noted that all similar substitutions and modifications are obvious to those skilled in the art and are considered to be included within the scope of this invention.

Claims

1. A composite hardening remover suitable for high-hardness aqueous systems of fracturing flowback fluid in oil and gas fields, characterized in that, The composite hardening agent comprises, by weight: 10-40 parts lime, 20-60 parts sodium sulfate, 5-25 parts sodium sulfite, and 15-50 parts sodium carbonate. In the high-hardness aqueous system of the oil and gas field fracturing flowback fluid, the calcium ion concentration is greater than 20,000 mg / L; The components of the composite hardening agent are premixed as a solid powder mixture, or prepared separately as a slurry or solution and added in sequence during use; wherein, the composite hardening agent is added in the following order: first lime is added, then sodium sulfate and sodium sulfite are added, and finally sodium carbonate is added.

2. The composite hardening agent according to claim 1, characterized in that, The weight ratio of sodium sulfate to sodium sulfite is (8:1) to (1:1).

3. The composite hardening agent according to claim 1, characterized in that, By weight, the lime is 15-25 parts, sodium sulfate is 45-55 parts, sodium sulfite is 10-15 parts, and sodium carbonate is 15-30 parts.

4. A method of using the composite hardening remover for high-hardness aqueous systems of fracturing flowback fluid in oil and gas fields, as described in any one of claims 1 to 3, characterized in that, This includes adding the composite hardening remover to the flowback fluid from fracturing operations in oil and gas fields.

5. The method of use according to claim 4, characterized in that, It further includes carrying out a precipitation reaction under stirring conditions; and separating the resulting precipitate.

6. The method of use according to claim 4, characterized in that, The dosage is 50~100g / L of water sample.

7. The method of use according to claim 4, characterized in that, The sodium sulfate can be added in stages. First, add 30%-50% of the calculated total amount, react for 5-30 minutes, and then add the remaining sodium sulfate.

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