Composite hardness removing agent suitable for high-hardness water-based system and using method thereof

Abstract

The invention provides a composite hardness removing agent suitable for a high-hardness water-based system and a use method of the composite hardness removing agent. The composite hardness removing agent comprises lime, sodium sulfate, sodium sulfite and sodium carbonate. The composite hardness removal agent is suitable for a high-hardness water-based system of oil and gas field fracturing flow-back fluid, can effectively avoid the risk of calcium sulfate scaling while remarkably reducing the agent cost, realizes deep hardness removal, and can synchronously remove dissolved oxygen, so that multiple challenges such as cost, scaling, effect and system corrosion are solved in a one-stop manner.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of water treatment, and provides a composite hardness removal agent suitable for a high-hardness aqueous system of fracturing flowback fluid in an oil and gas field and a use method thereof, in particular relates to a composite hardness removal agent for treating a high-hardness and high-mineralization aqueous system and a use method thereof, and is especially suitable for oil and gas field flowback fluid, brine refining and industrial circulating water system. BACKGROUND

[0002] Hydraulic fracturing technology is one of the key technologies for improving oil and gas field recovery rate, but a large amount of fracturing flowback fluid is generated. This wastewater is complex in composition, usually has high hardness (mainly Ca 2+ , Mg 2+ ), high mineralization, high chemical oxygen demand (COD), and contains residues of various additives. In order to achieve environmental protection requirements and water resource recycling, the fracturing flowback fluid must be subjected to deep treatment, and reducing hardness (softening) is a crucial link before reuse or standard discharge.

[0003] High-hardness aqueous system, especially calcium chloride type oil and gas field flowback fluid with calcium ion concentration exceeding 20,000 mg / L, is a difficult problem in the field of industrial water treatment. The existing technology generally uses "liquid alkali-sodium carbonate" method for hardness removal, which has the following defects: ① high cost: sodium carbonate is expensive, and the cost of reagent accounts for a large proportion when treating extremely high-hardness water. ② Corrosion risk: dissolved oxygen in the water can cause corrosion of metal equipment, and the traditional hardness removal agent does not have oxygen removal function. ③ Single effect: only hardness can be removed, and oxygen corrosion problem cannot be solved at the same time. ④ Multiple systems are distributed for dosing, and the operation procedure and intensity are high.

[0004] Although some technologies propose to use sodium sulfate to partially replace sodium carbonate to reduce cost, the introduction of sulfate may increase the risk of calcium sulfate scaling, and cannot achieve deep hardness removal and cannot solve the corrosion and discoloration problems caused by high dissolved oxygen.

[0005] Therefore, there is an urgent need for a low-cost, multifunctional and highly efficient hardness removal technology. SUMMARY

[0006] In view of the problems in the above background art, the main purpose of the present application is to provide a composite hardness removal agent suitable for a high-hardness aqueous system of fracturing flowback fluid in an oil and gas field and a use method thereof, which can significantly reduce the cost of reagents, effectively avoid the risk of calcium sulfate scaling, achieve deep hardness removal, and simultaneously remove dissolved oxygen, thereby solving the multiple challenges of cost, scaling, effect and system corrosion in one station.

[0007] In a first aspect, the present application provides a composite hardness removal agent suitable for a high-hardness aqueous system of fracturing flowback fluid in an oil and gas field, which comprises lime, sodium sulfate, sodium sulfite and sodium carbonate.

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

[0009] In some embodiments, the weight ratio of sodium sulfate to sodium sulfite in the composite hardness removal agent is (8:1) to (1:1), which is an optimal range for balancing cost and synergistic effect.

[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, and any one of the ranges formed by any two of the above values.

[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, and any one of the ranges formed by any two of the above values.

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

[0013] In some embodiments, the sodium sulfite is 5 parts, 10 parts, 15 parts, 20 parts, 25 parts, and any one of the ranges formed by any two of the above values.

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

[0015] The second aspect of the application provides a use method of a composite hardness removal agent suitable for a high-hardness aqueous system of oil and gas field fracturing flowback fluid, which comprises adding the composite hardness removal agent of the application to the oil and gas field fracturing flowback fluid, carrying out a precipitation reaction under stirring, and separating the generated precipitate. The method of the application can simultaneously reduce the hardness, dissolved oxygen content, and fouling tendency of the aqueous system.

[0016] In some embodiments, the addition amount is 50-100 g / L of water sample, preferably 50 g / L, 60 g / L, 70 g / L, 80 g / L, 90 g / L, 100 g / L, and any one of the ranges formed by any two of the above values.

[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 dosing sequence of the composite hardness removal agent is: first adding lime, then adding sodium sulfate and sodium sulfite, and finally adding sodium carbonate.

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

[0020] In some embodiments, the components of the composite hardness removal agent are pre-mixed into a solid powder mixture.

[0021] In some embodiments, the composite hardness removal agent is prepared as a slurry or a solution, respectively, and is added in sequence when used.

[0022] Beneficial effects (1) Synergistic cost reduction: By replacing a large amount of expensive sodium carbonate with inexpensive sodium sulfate, and utilizing the unique effect of sodium sulfite, the overall reagent cost is greatly reduced compared to the traditional "lime-sodium carbonate" method. Through the synergistic effect of lime, sodium sulfate, sodium sulfite, and sodium carbonate, a "precipitation-adsorption-flocculation" triple hardness removal mechanism is formed, which can stabilize the total hardness of the effluent to below 50 mg / L (as CaCO3).

[0023] (2) Multi-functional integration: Lime provides OH - for removing magnesium hardness and adjusting pH; sodium sulfate provides SO4 2- , which reacts with Ca 2+ to generate calcium sulfate precipitate, greatly reducing the concentration of calcium ions at a very low cost; sodium sulfite acts as an oxygen scavenger, effectively removing dissolved oxygen in water, fundamentally inhibiting oxygen corrosion of equipment, and at the same time, the SO3 2- introduced by it reacts with Ca 2+ to generate calcium sulfite precipitate, participating in the co-precipitation process, changing the crystal form of the precipitate, making it more loose and easy to remove; sodium carbonate provides CO3 2- for deep hardness removal, ensuring that the residual hardness of the effluent meets the standards.

[0024] (3) Scale inhibition and corrosion prevention: The oxygen removal effect of sodium sulfite directly prevents corrosion. At the same time, the competition and synergistic effect of multiple anions (SO4 2- , SO3 2- , CO3 2- ) disrupts the crystallization process of single calcium carbonate scale, generating a mixed and loose precipitate that is not easy to adhere to form scale, achieving scale inhibition effect.

[0025] (4) The present invention innovatively introduces sodium sulfite, whose sulfite ion (SO3 2-) can be adsorbed on the active growth point of calcium sulfate crystals as a crystal growth interference agent, causing lattice distortion and making it impossible to form stable and dense scale, fundamentally solving the secondary pollution problem caused by the introduction of sulfate. Using sodium sulfite as a chemical deoxidizer, the dissolved oxygen concentration can be reduced to below 0.1 mg / L, effectively controlling equipment corrosion and water color. A reagent simultaneously solves the three technical problems of hardness removal, scale inhibition and oxygen removal, simplifying the treatment process and the dosing system.

[0026] (5) Synergistic effect: lime provides OH - and remove magnesium hardness; sodium sulfate participates in hardness removal while reducing costs; sodium sulfite is a three-in-one agent: as an oxygen scavenger, its reaction product, sodium sulfate, can continue to be used for hardness removal, and it itself can also act as a calcium sulfate crystallization interference agent. Sodium carbonate performs deep hardness removal. The combination of the four components produces a "1+1+1+1>4" synergistic effect, and the treatment effect and economic benefits are far superior to the simple addition of each component. In view of the characteristics of the fracturing flowback fluid water quality fluctuation, through the optimized dosing sequence and potential dynamic control system, it is ensured that excellent treatment effect can be maintained under different working conditions.

[0027] Terminology Certain embodiments of the present application are now described in detail by referring to the following illustrative figures and chemical formulas. The application is intended to cover all alternatives, modifications and equivalents thereof as can be included within the scope of the present application as defined in the claims. Those skilled in the art will recognize that many methods and materials similar or equivalent to those described herein can be used in the practice of the present application. The present application is in no way limited to the methods and materials described herein. In the event that one or more of the incorporated literature, patents, and similar materials differs from or contradicts with the present application, including but not limited to defined terms, term application, described techniques, etc., the present application controls.

[0028] It should be further recognized that certain of the described features of the application, while individually novel, are described in the context of separate embodiments in order to more clearly understand the present application. Conversely, various features of the application, while individually novel, can be used in combination with each other in a single embodiment.

[0029] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. All patents and publications identified herein are incorporated herein by reference in their entirety.

[0030] In the description of the present specification, the description of the terms "one embodiment", "some embodiments", "an example", "a specific example", or "some examples" and the like means that the specific features, structures, materials or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present invention. In the present specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Also, the specific features, structures, materials or characteristics described can be combined in any suitable manner in any one or more embodiments or examples. In addition, the person skilled in the art can combine and combine the different embodiments or examples described in the present specification and the features of the different embodiments or examples, without contradiction.

[0031] In the following, all the numbers disclosed herein are approximate, whether or not the word "approximately" or "about" is used in connection with such numbers. The value of each number can vary by 1%, 2%, 5%, 7%, 8%, 10%, 15%, or 20% or more. Whenever a number having a value of N is disclosed, any number having a value of N + / - 1%, N + / - 2%, N + / - 3%, N + / - 5%, N + / - 7%, N + / - 8%, N + / - 10%, N + / - 15%, or N + / - 20% is also disclosed, where "+" and "-" mean plus or minus. DETAILED DESCRIPTION

[0032] In order to make the purpose, technical solutions and advantages of the present invention clearer, the present invention is further described in detail below in combination with embodiments. The specific embodiments described herein are only used to explain the present invention and do not constitute any limitation on the present invention. In addition, in the following description, the description of well-known structures and technologies is omitted to avoid unnecessary confusion of the concept of the present disclosure. Such structures and technologies are also described in many publications.

[0033] The reagents used in the present invention can be purchased from the market or can be prepared by the methods described in the present invention.

[0034] Preparation Example 1 The components were weighed according to the following weight ratio and mixed uniformly to prepare composite hardness removal agent A.

[0035] Lime: 15 parts, sodium sulfate: 55 parts, sodium sulfite: 15 parts, sodium carbonate: 15 parts Preparation Example 2 The components were weighed according to the following weight ratio and mixed uniformly to prepare composite hardness removal agent B.

[0036] Lime: 25 parts, sodium sulfate: 45 parts, sodium sulfite: 15 parts, sodium carbonate: 30 parts Preparation Example 3 The components are weighed according to the following weight ratio and mixed uniformly to prepare the composite hardness-removing agent C.

[0037] Lime: 30 parts, sodium sulfate: 40 parts, sodium sulfite: 5 parts, sodium carbonate: 25 parts Preparation of Example 4 The components are weighed according to the following weight ratio and mixed uniformly to prepare the composite hardness-removing agent C.

[0038] Lime: 30 parts, sodium sulfate: 20 parts, sodium sulfite: 20 parts, sodium carbonate: 20 parts Preparation of Comparative Example 1 The components are weighed according to the following weight ratio and mixed uniformly to prepare the composite hardness-removing agent a.

[0039] Sodium hydroxide: 2 parts, sodium carbonate: 50 parts Preparation of Comparative Example 2 The components are weighed according to the following weight ratio and mixed uniformly to prepare the composite hardness-removing agent b.

[0040] Lime: 25 parts, sodium sulfate: 45 parts, sodium carbonate: 30 parts Preparation of Comparative Example 3 The components are weighed according to the following weight ratio and mixed uniformly to prepare the composite hardness-removing agent c.

[0041] Lime: 25 parts, sodium carbonate: 30 parts Application Example 1: Treatment of high-hardness fracturing flowback fluid Take fracturing flowback fluid from an oilfield, and the water quality is as follows: Ca 2+ : 32365 mg / L, Mg 2+ : 1,200 mg / L, dissolved oxygen: 5.5 mg / L, pH: 6.96 Treatment steps: 1) Take 1 L of water sample, and add 60 g of composite hardness-removing agent under stirring, and react for 50 minutes.

[0042] 2) Add 3 mg / L of PAM, and stir and flocculate for 10 minutes.

[0043] 3) Adjust pH and stand for precipitation, and take supernatant for detection.

[0044] The detection results are shown in Table 1 as follows:

[0045] Compared with Comparative Example 1, the present application (especially Example 2) has a significantly reduced cost and completely removes dissolved oxygen, and the precipitate is easier to handle, while the residual hardness is slightly higher but still excellent.

[0046] Compared with Comparative Example 2 and Comparative Example 3, the present application has the additional effect of deep deoxygenation due to the addition of sodium sulfite, and at the same time, due to the intervention of sulfite, the precipitation characteristics are changed and the residual hardness is lower. This proves that the addition of sodium sulfite brings unexpected synergistic effect, rather than simple superposition.

[0047] The method of the present application has been described by preferred embodiments, and the relevant personnel can obviously make changes or appropriate changes and combinations to the methods and applications described herein within the content, spirit and scope of the present application to realize and apply the present technology. Those skilled in the art can refer to the content herein to appropriately improve the process parameters for implementation. It is particularly pointed out that all similar replacements and changes are obvious to those skilled in the art, and they are considered to be included in the present application.

Claims

1. A composite hardening remover suitable for high-hardness aqueous systems of fracturing flowback fluid in oil and gas fields, characterized in that, It includes lime, sodium sulfate, sodium sulfite, and sodium carbonate.

2. The composite hardening agent according to claim 1, characterized in that, By weight, it includes: 10-40 parts lime, 20-60 parts sodium sulfate, 5-25 parts sodium sulfite, and 15-50 parts sodium carbonate.

3. 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).

4. 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.

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

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

7. The method of use according to claim 5, characterized in that, The dosage is 50~100g / L of water sample.

8. The method of use according to claim 5, characterized in that, 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.

9. The method of use according to claim 5, characterized in that, 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.

10. The method of use according to claim 5, characterized in that, The sodium sulfate can be added in steps, first adding 30%-50% of its calculated total amount, reacting for 5-30 minutes, and then adding the remaining sodium sulfate. Alternatively, the components of the composite hardener may be premixed as a solid powder mixture, or prepared separately as a slurry or solution and added sequentially during use.

Images