An anti-scaling agent which can be attached and solidified in a stratum and a preparation method thereof

Abstract

The present application provides a scale inhibitor which can be attached and solidified in stratum and its preparation method. The scale inhibitor is composed of a scale inhibition system and water absorbent resin, is in emulsion state and can be attached and solidified in stratum. The whole emulsion droplet can be deformed according to the pore throat of stratum and is not easy to be blocked, and can enter into the production layer. The scale inhibitor has low viscosity on the ground, and after staying in the porous medium, gradually thickens under the action of crosslinking agent, can stay in the stratum for a long time, and slowly degrades after meeting divalent cations, the scale inhibitor is slowly released, the scale prevention period is long, the shortcomings of traditional adsorption type or precipitation squeeze process are overcome, and long-term scale prevention is realized after the measures on the wellbore and stratum. The superfine silicon dioxide particles suspended in the water absorbent resin can guarantee good conductivity between resin particles, the bactericide endows the product with the characteristics of bacteriostasis and sterilization, can effectively prevent the rapid degradation of the resin and prolong the release period of the scale inhibitor.

Description

Technical Field

[0001] This invention belongs to the field of oilfield additives technology, specifically relating to a scale inhibitor that can adhere and solidify in formations and its preparation method. Background Technology

[0002] Scaling in oil and gas field production systems is a significant issue affecting production and development efficiency. Scaling can occur throughout the entire lifecycle of oil and gas field development, causing formation and wellbore blockages that affect production and ultimate recovery rates. Among numerous scale inhibition technologies, adding scale inhibitors to oil and gas wells is a commonly used and effective measure. (1) Adding liquid scale inhibitors: Liquid scale inhibitors are easily carried out and have a short effective period; they adhere to the tubing wall, resulting in low agent utilization; adding them requires the use of high-pressure injection pumps, containers, and pump trucks, which is difficult and labor-intensive. (2) Adding solid slow-release scale inhibitors: The dissolution of polymers causes concentrated release of the scale inhibitor and a short effective period.

[0003] Deep formation injection anti-scaling technology is the most widely used anti-scaling technology in onshore and offshore oilfields both domestically and internationally. Essentially, it is a process of placing anti-scaling agents, which are squeezed into the scaling formation. The anti-scaling agents are retained in the formation rocks through adsorption or precipitation. As oil and gas wells produce, they are slowly desorbed and dissolved in the produced water, achieving the purpose of preventing scale buildup in the formation, wellbore, and surface facilities. It is a commonly used well workover technique in oilfields.

[0004] Currently, there are mainly two processes for scale inhibitor injection: adsorption-type extrusion and precipitation-type extrusion. However, the adsorption capacity of these scale inhibitor extrusion processes is affected by many factors, such as formation water composition and pH value, reservoir wettability and mineral composition, temperature, etc. Moreover, the surface is already thickened, so it cannot better penetrate into the deep formation fissures. Most products have a certain shelf life, the length of which depends on the type of scale inhibitor, the retention method adopted, and the formation mineralogical and physical properties. Generally, the shelf life is 0.5 to 2 years, and it cannot prevent scale from entering the wellbore and formation for a long time.

[0005] On June 10, 2022, the State Intellectual Property Office published patent publication number CN114605979A, entitled "A Calcium Carbonate Antiscalant for Oilfields and its Preparation Method." This invention utilizes the coagulation and subsequent dispersion effects of aspartic acid to stably suspend potentially scale-forming microcrystals in water, thus hindering collisions between crystal particles and metal surfaces and inhibiting scale growth. While this antiscalant is effective against calcium carbonate, its effectiveness is short-lived and it cannot provide long-term scale prevention for wellbores and formations. Summary of the Invention

[0006] The purpose of this invention is to provide an antiscalant that can adhere and solidify in formations, overcoming the aforementioned technical problems in the prior art.

[0007] Another object of the present invention is to provide a method for preparing an antiscalant that can adhere and solidify in the formation.

[0008] Therefore, the technical solution provided by the present invention is as follows:

[0009] A scale inhibitor that can adhere and solidify in formations comprises the following substances by weight percentage: 99-99.5% scale inhibitor system and 0.5-1% water-absorbing resin by weight percentage.

[0010] The scale prevention system comprises the following components by mass percentage as a percentage of the scale inhibitor: 50-60% scale inhibitor, 10-15% natural polymer material, 10% barium sulfate, 1% regulator, 0.4-0.6% ammonium sulfate, and the balance being water.

[0011] The water-absorbing resin is obtained by reacting the following components in the following mass percentages as a percentage of the scale inhibitor: acrylic acid 0.3%–0.6%, alkali 0.15%–0.3%, bactericide 0.02%–0.04%, composite organic chromium crosslinking agent 0.01%–0.02%, ultrafine silica 0.01%–0.02%, and initiator 0.01%–0.02%, wherein the ultrafine silica has a particle size of 2000–3000 mesh.

[0012] The anti-scaling agent is a compound of organophosphorus compounds and multi-component polymers in a mass ratio of 1:1 to 2. The multi-component polymers are polyacrylic acid, hydrolyzed polymaleic anhydride, or sodium polyvinyl sulfonate.

[0013] The regulator is diethylenetriamine hydrochloride or polymethacrylate.

[0014] The preparation process of the anti-scaling system is as follows:

[0015] At 50-70℃, first add the formulated amount of natural polymer material to a certain amount of water and stir until the natural polymer material dissolves. Then, add the formulated amount of barium sulfate in batches and stir evenly. Add the formulated amount of scale inhibitor, lower the temperature to 40-60℃, stir and add the slow-release rate regulator. Then, dissolve the formulated amount of ammonium sulfate in the remaining water and stir for 3-4 hours to obtain the final product.

[0016] The bactericide is acryloylmorpholine or dodecyl dimethyl benzyl ammonium chloride, and the initiator is potassium persulfate or sodium bisulfite.

[0017] The mass ratio of acrylic acid to potassium hydroxide is 2:1.

[0018] A method for preparing a scale inhibitor that can adhere and solidify in formations includes the following steps:

[0019] Step 1) Prepare the anti-scaling system;

[0020] Step 2) Preparation of water-absorbing resin: Add the prescribed amount of acrylic acid and alkali to the reactor for neutralization reaction, then add bactericide, composite organic chromium crosslinking agent and ultrafine silica. When the temperature is adjusted to 25℃~30℃, add initiator. Under the action of initiator, the polymerization reaction is initiated. It initially has a certain viscosity. Nitrogen gas is passed through for oxygen removal for 20~30 minutes. When the temperature no longer rises, the reaction ends.

[0021] Step 3) Add the anti-scaling system and water-absorbing resin according to the formula ratio, and stir evenly to obtain the anti-scaling agent.

[0022] The beneficial effects of this invention are:

[0023] The scale inhibitor provided by this invention is an emulsion that can adhere and solidify in the formation. The entire emulsion droplet can conform to the deformation of formation pores and throats, making it less prone to clogging and allowing it to enter the producing layer. The scale inhibitor has low viscosity at the surface and gradually thickens under the action of a crosslinking agent after remaining in the porous medium, allowing it to remain in the formation for a long time. The hydrogel slowly degrades upon encountering divalent cations, resulting in the slow release of the scale inhibitor and a long scale prevention period. This overcomes the shortcomings of traditional adsorption or precipitation-injection processes, providing long-term scale prevention for the wellbore and formation.

[0024] The ultrafine silica particles suspended in the water-absorbing resin ensure good conductivity between resin particles, while the bactericide gives the product antibacterial and bactericidal properties, effectively preventing rapid resin degradation and extending the release cycle of the scale inhibitor. Detailed Implementation

[0025] 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.

[0026] Exemplary embodiments of the present invention are now described; 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 is not intended to limit the invention.

[0027] 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.

[0028] Example 1

[0029] This embodiment provides a scale inhibitor that can adhere and solidify in the formation, composed of the following substances by weight percentage: 99-99.5% scale inhibitor system and 0.5-1% water-absorbing resin by weight percentage.

[0030] The scale prevention system comprises the following components by mass percentage as a percentage of the scale inhibitor: 50-60% scale inhibitor, 10-15% natural polymer material, 10% barium sulfate, 1% regulator, 0.4-0.6% ammonium sulfate, and the balance being water.

[0031] The water-absorbing resin is obtained by reacting the following components in the following mass percentages, based on the mass percentage of the scale inhibitor: acrylic acid 0.3%–0.6%, alkali 0.15%–0.3%, bactericide 0.02%–0.04%, composite organic chromium crosslinking agent 0.01%–0.02%, ultrafine silica 0.01%–0.02%, and initiator 0.01%–0.02%.

[0032] Principle of this invention:

[0033] In the anti-scaling system, natural polymer materials serve as thickeners, diethylenetriamine hydrochloride as a slow-release rate regulator, barium sulfate as a weighting agent, and ammonium sulfate as a coagulant. The water-absorbing resin is generated through a neutralization reaction between acrylic acid and alkali, followed by polymerization under the action of an initiator and crosslinking agent. The composite organic chromium crosslinking agent, model SD-107, was purchased from Shandong Shida Oilfield Technology Service Co., Ltd. SD-107 crosslinking agent is obtained through a multi-step polymerization process and is a low-to-medium temperature (35-70℃) composite crosslinking agent with delayed crosslinking properties. The suspended ultrafine silica particles in the water-absorbing resin ensure good conductivity between resin particles, while the bactericide imparts antibacterial and bactericidal properties to the product, effectively preventing rapid resin degradation and extending the release cycle of the anti-scaling agent.

[0034] Example 2

[0035] Based on Example 1, this example provides a scale inhibitor that can adhere and solidify in the formation, composed of the following substances by weight percentage: 99.5% scale inhibitor system (60% scale inhibitor, 10% natural polymer material, 10% barium sulfate, 1% regulator, 0.6% ammonium sulfate, 17.9% water), and 0.5% water-absorbing resin by weight percentage (0.3% acrylic acid, 0.15% alkali, 0.02% bactericide, 0.01% composite organic chromium crosslinking agent, 0.01% ultrafine silica, 0.01% initiator).

[0036] In this embodiment, the natural polymer material is gelatin, the regulator is diethylenetriamine hydrochloride, the alkali is potassium hydroxide, the bactericide is acryloylmorpholine, the scale inhibitor is a compound of hydrolyzed polymaleic anhydride and ethylenediaminetetramethylenephosphonate in a mass ratio of 1:1, and the initiator is potassium persulfate.

[0037] Preparation process:

[0038] Step 1) Preparation of the anti-scaling system:

[0039] At 70℃, first add the formulated amount of natural polymer material to a certain amount of water (the amount of water added should be enough to dissolve the natural polymer material), stir until the natural polymer material dissolves, then add the formulated amount of barium sulfate in batches, stir evenly, then add the formulated amount of scale inhibitor, lower the temperature to 60℃, stir and add the slow-release rate regulator, then dissolve the formulated amount of ammonium sulfate in the remaining water and stir for 4 hours to obtain the final product; the amount of water added in the two steps is equal to the formulated amount of water.

[0040] Step 2) Preparation of water-absorbing resin:

[0041] Add the prescribed amount of acrylic acid and alkali to the reactor for neutralization reaction, then add bactericide, composite organic chromium crosslinking agent and ultrafine silica. When the temperature is adjusted to 30℃, add the initiator. Under the action of the initiator, the polymerization reaction is initiated. Initially, it has a certain viscosity. Nitrogen gas is purged for oxygen removal for 30 minutes. When the temperature no longer rises, the reaction ends.

[0042] Step 3) Add the anti-scaling system and water-absorbing resin according to the formula ratio, and stir evenly to obtain the anti-scaling agent.

[0043] The prepared scale inhibitor is emulsion-like. After entering the formation, the fluid gradually thickens due to the use of a composite organic chromium crosslinking agent, allowing it to further solidify within 24-48 hours. This enables it to penetrate deeper fissures and adhere better to the rock surface. Suspended silica particles ensure good conductivity between resin particles.

[0044] Example 3

[0045] Based on Example 1, this example provides a scale inhibitor that can adhere and solidify in the formation, composed of the following substances by weight percentage: 99% scale inhibitor system (50% scale inhibitor, 15% natural polymer material, 10% barium sulfate, 1% regulator, 0.5% ammonium sulfate, 22.5% water, and 1% water-absorbing resin by weight percentage (0.6% acrylic acid, 0.3% alkali, 0.04% bactericide, 0.02% composite organic chromium crosslinking agent, 0.02% ultrafine silica, and 0.02% initiator).

[0046] Preparation process:

[0047] At 60℃, add 15% of the natural polymer material gelatin to 15% deionized water and stir until the gelatin dissolves. Add 10% barium sulfate in batches, stirring evenly. After slowly adding 50% of the scale inhibitor to the system, lower the temperature to 50℃, stir, and add 1% of the slow-release rate regulator. Then, dissolve 0.5% of the inorganic salt coagulant ammonium sulfate in water and add it, stirring for 2 hours. Continue stirring for 1 hour to obtain the scale inhibitor system.

[0048] Acrylic acid and potassium hydroxide were added to the reactor according to the formula for neutralization. Then, a bactericide, crosslinking agent, and ultrafine silica were added. When the temperature was adjusted to 25℃-30℃, 0.01% initiator was added. The polymerization reaction was initiated under the action of the initiator, initially producing a certain viscosity. Nitrogen gas was purged for 30 minutes to remove oxygen; the reaction was considered complete when the temperature no longer rose. To stabilize the reaction, a certain amount of water could be added.

[0049] In this embodiment, the natural polymer material is gelatin, the regulator is polymethyl methacrylate, the alkali is sodium hydroxide, the bactericide is dodecyl dimethyl benzyl ammonium chloride, the scale inhibitor is a compound of polyacrylic acid and diethylenetriaminepentamethylenephosphonic acid in a mass ratio of 1:2, and the initiator is sodium bisulfite.

[0050] Example 4

[0051] Based on Example 1, this example provides a scale inhibitor that can adhere and solidify in the formation, composed of the following substances by weight percentage: 99.3% scale inhibitor system (55% scale inhibitor, 12% natural polymer material, 10% barium sulfate, 1% regulator, 0.4% ammonium sulfate, 20.9% water, and 0.7% water-absorbing resin by weight percentage (0.4% acrylic acid, 0.2% alkali, 0.04% bactericide, 0.02% composite organic chromium crosslinking agent, 0.02% ultrafine silica, and 0.02% initiator).

[0052] The preparation process is the same as in Example 3.

[0053] In this embodiment, the natural polymer material is gelatin, the regulator is diethylenetriamine hydrochloride, the alkali is potassium hydroxide, the bactericide is acryloylmorpholine, the scale inhibitor is a compound of sodium polyvinylsulfonate and aminotrimethylenephosphonic acid in a mass ratio of 1:1, and the initiator is potassium persulfate.

[0054] To further illustrate the effects of this invention, the scale inhibitors prepared in Examples 2-4 and existing scale inhibitors were subjected to the following performance tests as comparative examples, with a concentration of 20 mg / L for all samples. The comparative example was an oilfield scale inhibitor, model JM-206, purchased from Zibo Jimei Environmental Protection Technology Co., Ltd., which is composed of various organophosphonic acids, surfactants, and synergists.

[0055] Scale prevention rate (SY / T 5673-2020 General Technical Conditions for Scale Inhibitors in Oilfields), viscosity (SYT5834-2007 Performance Evaluation Index and Determination Method for Low Solid Phase Well Control Fluids). Experimental results are shown in Table 1.

[0056] Table 1. Scale prevention rate and viscosity results

[0057] Example 2 Example 3 Example 4 Comparative Example Scale prevention rate 95％ 91％ 93％ 87％ Ground viscosity / mPa.s 16 18 20 - Formation viscosity / mPa.s 300 268 283 -

[0058] The scale inhibitor prepared in Example 2 was applied in the field. The scale inhibitor was prepared at the wellhead according to the required ratio, and then a small amount of water was injected to slug the well. The scale inhibitor was then replaced and pushed into the formation. The well was shut in for 48 hours to react.

[0059] After construction, water samples are taken every month for P ion testing. If the ion content is above 5 ppm, the scale inhibitor is effective and has a validity period of more than 3 years.

[0060] In summary, this scale inhibitor has a low viscosity at the surface. After injection into the formation, it can penetrate deeper into fissures and, while remaining in the porous medium, undergoes secondary thickening under the action of a composite organic chromium crosslinking agent. This allows for better adhesion to the rock surface and long-term retention in the formation. The water-absorbing resin slowly demulsifies upon encountering divalent cations, resulting in a slow release of the scale inhibitor. This provides a long-term scale prevention period without the risk of sudden, large-scale release and waste. Following injection, it provides long-term scale prevention for the wellbore and formation.

[0061] 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 scale inhibitor that can adhere and solidify in formations, characterized in that: It consists of the following substances by weight percentage: anti-scaling system 99~99.5%, water-absorbing resin 0.5~1% by weight; The scale prevention system comprises the following components by mass percentage as a percentage of the scale inhibitor: 50-60% scale inhibitor, 10-15% natural polymer material, 10% barium sulfate, 1% regulator, 0.4-0.6% ammonium sulfate, and the balance being water; The water-absorbing resin is obtained by reacting the following components in the following mass percentages as a percentage of the scale inhibitor: acrylic acid 0.3%~0.6%, alkali 0.15%~0.3%, bactericide 0.02%~0.04%, composite organic chromium crosslinking agent 0.01%~0.02%, ultrafine silica 0.01%~0.02%, and initiator 0.01%~0.02%, wherein the ultrafine silica has a particle size of 2000-3000 mesh; The anti-scaling agent is a compound of organophosphorus compounds and multi-component polymers in a mass ratio of 1:1 to 2. The multi-component polymers are polyacrylic acid, hydrolyzed polymaleic anhydride, or sodium polyvinyl sulfonate.

2. The scale inhibitor that can adhere and solidify in formations according to claim 1, characterized in that: The regulator is diethylenetriamine hydrochloride or polymethacrylate.

3. The scale inhibitor that can adhere and solidify in formation according to claim 1, characterized in that: The preparation process of the anti-scaling system is as follows: At 50~70℃, first add the formulated amount of natural polymer material to a certain amount of water and stir until the natural polymer material dissolves. Then, add the formulated amount of barium sulfate in batches and stir evenly. Add the formulated amount of scale inhibitor, lower the temperature to 40~60℃, stir and add the slow-release rate regulator. Then, dissolve the formulated amount of ammonium sulfate in the remaining water and stir for 3~4 hours to obtain the final product.

4. The scale inhibitor that can adhere and solidify in formations according to claim 1, characterized in that: The bactericide is acryloylmorpholine or dodecyl dimethyl benzyl ammonium chloride, and the initiator is potassium persulfate or sodium bisulfite.

5. A scale inhibitor that can adhere and solidify in formations according to claim 1, characterized in that: The mass ratio of acrylic acid to potassium hydroxide is 2:

1.

6. A method for preparing a scale inhibitor that can adhere and solidify in a formation according to any one of claims 1-5, characterized in that, Includes the following steps: Step 1) Prepare the anti-scaling system; Step 2) Preparation of water-absorbing resin: Add the prescribed amount of acrylic acid and alkali to the reactor for neutralization reaction, then add bactericide, composite organic chromium crosslinking agent and ultrafine silica. When the temperature is adjusted to 25℃~30℃, add initiator. Under the action of initiator, the polymerization reaction is initiated. It initially has a certain viscosity. Nitrogen gas is passed through for oxygen removal for 20~30 minutes. When the temperature no longer rises, the reaction ends. Step 3) Add the anti-scaling system and water-absorbing resin according to the formula ratio, and stir evenly to obtain the anti-scaling agent.