Low-corrosivity sulfur dissolving agent and preparation method thereof

Abstract

The invention relates to the technical field of oil-gas field development and pipeline transportation, in particular to a low-corrosivity sulfur dissolving agent and a preparation method thereof. The specific technical scheme is as follows: the low-corrosion sulfur dissolving agent comprises the following components: 50-70 wt% of metal alkoxide, 5-15 wt% of benzene compounds, 10-20 wt% of an alkaline triazine sulfur removal agent, 3-10 wt% of a surfactant, 5-15 wt% of a corrosion inhibitor and 3-10 wt% of an auxiliary agent. The prepared sulfur dissolving agent can be widely applied to medium and low sulfur-containing gas well shafts and gathering and transportation pipelines so as to slow down deposition of elemental sulfur and release of H2S and relieve erosion damage of deposition of wet elemental sulfur to oil pipes and packer rubber.

Description

Technical Field

[0001] The invention relates to the technical field of oil and gas field development and pipeline transportation, and in particular to a low-corrosive sulfur dissolving agent and a preparation method thereof. Background Art

[0002] Fossil energy, mainly oil and gas, is still the "ballast stone" of global energy security. According to 20 scenario forecasts from 11 institutions (including IEA, bp, Equinor, IEEJ, OPEC, EIA, etc.), oil and gas will still account for more than 40% of the global primary energy structure in the next 20 years. Among them, ExxonMobil, OPEC, etc. predict that oil and gas will still account for more than 50% of the energy structure in 2050. Driven by the "dual carbon" goal, the proportion of natural gas as a high-quality clean energy in primary energy consumption has increased significantly. Natural gas will still be an important tool for "carbon reduction" in the energy system. Therefore, a series of natural gas fields at home and abroad have entered the ranks of large-scale development or expansion.

[0003] According to surveys, almost every crude oil producing country in the world has natural gas reservoirs containing hydrogen sulfide, and acidic natural gas fields are scattered all over the world. Elemental sulfur exists in large quantities in sour natural gas. H2S reacts with elemental sulfur to form unstable polyhydrogen sulfide. High temperature and high pressure are conducive to the formation of compounds.

[0004] The reaction equation is:

[0005] During the mining process, the reduction of formation pressure causes the precipitation, migration and deposition of sulfur particles in porous media, resulting in a decrease in formation porosity and permeability. In the process of gas rising from the bottom of the well to the wellhead, polyhydrogen sulfide decomposes into H2S and elemental sulfur and deposits on the well wall. The deposition of elemental sulfur is extremely harmful and can cause blockages every few days or weeks, which affects the gas reservoir production on the one hand, and in severe cases causes the gas well to stop production or be scrapped.

[0006] During the process of natural gas gathering and transportation, where the temperature and pressure change greatly, the sulfur element in the natural gas will precipitate into sulfur and adsorb on the inner wall of the pipeline, blocking the pipeline. In addition, its corrosion to metal and rubber is also a very difficult problem, which also poses a great threat to the safety of gas fields and construction workers.

[0007] In addition, due to the influence of capture gas source, capture process and economic cost, the supercritical CO2 fluid transported by pipeline will inevitably be mixed with some corrosive impurities, such as H2O, O2, H2S, SO x and NO xEtc. Especially when there are multiple impurities in supercritical CO2, complex chemical reactions can occur between the impurities. Even if the contents of H2O, O2, SO2, NO2 and H2S are all lower than the recommended threshold of the existing CO2 quality specification, chemical reactions can still occur between the impurities to generate corrosive substances such as H2SO4, HNO3, elemental sulfur, H2O, etc., leading to the formation of a strongly acidic liquid phase. Therefore, multiple trace impurities and reaction products between impurities significantly enhance the corrosiveness of supercritical CO2 fluid, greatly increasing the corrosion risk of pipelines.

[0008] Therefore, in order to prevent the blockage of elemental sulfur, an appropriate solvent is injected into the well to dissolve the elemental sulfur formed, slow down the volatilization of H2S produced by the hydrolysis of wet elemental sulfur, and slow down the corrosion of the pipe column and the gathering pipeline. Many solvents used in this method are CS2, cycloalkanes, inorganic bases, organic bases, alkyl disulfides, and mixtures of the above solvents.

[0009] The oil field is still dominated by the DMDS system and carbon disulfide system, which are highly toxic, costly and corrosive. The physical solvents mainly include CS2, light mineral oil, liquid hydrocarbons, paraffin-based mineral oil, aromatic hydrocarbons, cycloalkanes, petroleum fractions, alkylnaphthalene mixtures, carbon tetrachloride, tetrachloroethylene, etc. The chemical solvents mainly include inorganic bases, organic bases and organic disulfides. Chemical sulfur dissolving agents mainly react with hydrogen sulfide and elemental sulfur to generate easy-flowing substances.

[0010] For physical sulfur dissolving agents, solid sulfur is dissolved in solvents according to the principle of like dissolves like. Common physical sulfur dissolving agents include benzene compounds, cyclohexene, cyclohexane, alcohols, etc. The solubility of solid sulfur in physical solvents is usually from large to small: chlorobenzene> styrene> 1,2,3,4-tetrahydronaphthalene> toluene> cyclohexene> benzene> ethylbenzene> cyclohexane≈ hexane, and the solubility of solid sulfur increases with the increase of temperature. Although the amount of dissolved sulfur is large, it can generally only handle the situation of slight elemental sulfur deposition. When the sulfur deposition is serious and the amount of elemental sulfur deposited is large, it is necessary to use chemical solvents to react chemically with the deposited elemental sulfur to achieve the purpose of solving sulfur deposition. For chemical sulfur dissolving agents, it is the polymerization of solvents, hydrogen sulfide and sulfur to form water-soluble polysulfides. The most common ones are some alkaline compounds, such as dimethyl disulfide (DMDS), N,N-dimethylformamide (DMF), ethanolamine, etc. However, the ability of pure organic alkaline solution to dissolve elemental sulfur is low and cannot meet industrial requirements. In addition, the DMDS system has a pungent odor, high toxicity, and strong corrosiveness, which makes the system face great difficulties in the early preparation, transportation, use, and recycling processes. In addition, it is expensive, has low cost performance, and is limited in practical application. This is also a common problem of all disulfide sulfur dissolving agents. Therefore, the development of a new safe and efficient sulfur dissolving system that is efficient, low toxic, moderately cost-effective, and weakly corrosive has considerable research significance and research value. Summary of the invention

[0011] In view of the deficiencies in the prior art, the present invention provides a low-corrosive sulfur dissolving agent and a preparation method thereof. The prepared sulfur dissolving agent can be widely used in the wellbores of medium and low sulfur gas wells and gathering and transportation pipelines to slow down the deposition of elemental sulfur, the release of H2S, and alleviate the corrosion damage of wet elemental sulfur deposition to oil pipes and packer rubber.

[0012] To achieve the above objectives, the present invention is implemented through the following technical solutions:

[0013] The invention discloses a low-corrosive sulfur dissolving agent, which comprises the following components: 50-70 wt% of metal alkoxide, 5-15 wt% of benzene compound, 10-20 wt% of alkaline triazine desulfurizing agent, 3-10 wt% of surfactant, 5-15 wt% of corrosion inhibitor and 3-10 wt% of auxiliary agent.

[0014] Preferably, the auxiliary agent includes a chelating agent, a penetrant, and an antifreeze agent.

[0015] Preferably, by mass percentage, the chelating agent is 20-40%, the penetrant is 30-50%, and the antifreeze agent is 15-35%.

[0016] Preferably, the chelating agent includes a phosphate chelating agent (such as hydroxycarboxylic acid) or an organic polyphosphate chelating agent (such as polyamine); the penetrant includes a high-temperature penetrant JFC-M and / or acetone; and the antifreeze agent includes ethylene glycol and / or ethanol.

[0017] Preferably, the metal alkoxide includes at least one of sodium tert-butoxide, potassium ethoxide, and potassium tert-butoxide; the benzene compound includes at least one of o-xylene and chlorobenzene; the surfactant includes at least one of sodium polystyrene sulfonate and alkylphenol polyoxyethylene ether; and the corrosion inhibitor includes at least one of azole corrosion inhibitor and amino acid corrosion inhibitor.

[0018] Correspondingly, a method for preparing a low-corrosive sulfur dissolving agent is disclosed. The preparation process of the low-corrosive sulfur dissolving agent is as follows: under normal temperature and pressure conditions, metal alkoxides, benzene compounds, alkaline triazine desulfurizers, surfactants, corrosion inhibitors, and additives are mixed and stirred for 8 to 10 minutes.

[0019] The present invention has the following beneficial effects:

[0020] 1. The sulfur dissolving agent disclosed in the present invention is mainly composed of organic and inorganic sulfur dissolving agents, sulfur removers, penetrants, corrosion inhibitors, other additives, etc. The present invention integrates high-efficiency sulfur dissolving and sulfur removal, and also has the characteristics of low corrosiveness, etc. The sulfur dissolving amount of elemental sulfur powder at 50°C and 2 hours is higher than 100g / 100mL, the sulfur removal rate is higher than 80%, the corrosion rate of N80S steel at 50°C is lower than 0.076mm / a in the standard, the swelling rate of fluororubber is lower than 2.0%, and the tensile performance decreases by no more than 0.5MPa.

[0021] 2. The present invention gives full play to the advantages of metal alkoxide alkaline chemical sulfur dissolving agents, which have high sulfur dissolving capacity, physical sulfur dissolving agent polarity and similar structure to elemental sulfur. Chemical sulfur dissolving agents are used as the main agent and physical sulfur dissolving agents as the auxiliary agent. The high sulfur solubility is used to solve the problem of elemental sulfur deposition blocking the wellbore and pipeline and thus affecting production capacity. In addition to the above-mentioned removal of physically deposited sulfur, the addition of a desulfurizer also has the ability to solve the problem of chemically deposited sulfur. The surfactant is used to enhance its permeability and increase the sulfur dissolving rate to solve the problem of difficult dissolution of deposited blocks. And by adding an environmentally friendly corrosion inhibitor, the problem of serious corrosion of the composite sulfur dissolving agent on the pipe string and the rubber sleeve of the packer is solved. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 is the amount of dissolved sulfur (lumps) at different temperatures (2h);

[0023] Figure 2 This is a diagram of a desulfurization device; in the figure, 1-helium inlet control valve, 2-separating funnel (hydrochloric acid), 3-round-bottom beaker (deionized water + 2.5v% sodium sulfide), 4-iron stand, 5, 6, 7-test tubes (distilled water + 0.5v% sulfur-dissolving agent), 8-conical flask (zinc acetate), 9, 10, 11-switch clamps, 12-magnetic stirring heater, 13-conical flask (sodium hydroxide). DETAILED DESCRIPTION

[0024] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0025] Unless otherwise specified, the technical means used in the embodiments are conventional means well known to those skilled in the art.

[0026] The invention discloses a low-corrosive sulfur dissolving agent, which comprises the following components: 50-70wt% of metal alkoxide, 5-15wt% of benzene compound, 10-20wt% of alkaline triazine desulfurizing agent, 3-10wt% of surfactant, 5-15wt% of corrosion inhibitor, and 3-10wt% of auxiliary agent. The auxiliary agent comprises chelating agent, penetrant, and antifreeze agent. According to the mass percentage, the chelating agent comprises 20-40%, the penetrant comprises 30-50%, and the antifreeze agent comprises 15-35%.

[0027] Wherein, the chelating agent includes but is not limited to phosphate chelating agents (such as hydroxycarboxylic acids) or organic polyphosphate chelating agents (such as polyamines); the penetrant includes but is not limited to high temperature penetrant JFC-M and / or acetone; the antifreeze agent includes but is not limited to ethylene glycol and / or ethanol.

[0028] The metal alkoxide as a chemical sulfur dissolving agent includes at least one of sodium tert-butoxide, potassium ethoxide, and potassium tert-butoxide; the benzene compound as a physical sulfur dissolving agent includes at least one of o-xylene and chlorobenzene; the surfactant includes at least one of sodium polystyrene sulfonate and alkylphenol polyoxyethylene ether; the corrosion inhibitor includes at least one of azole corrosion inhibitors such as bisimidazoline quaternary ammonium salt and amino acid corrosion inhibitors such as DL-histidine. The surfactant may also include fatty alcohol polyoxyethylene ether.

[0029] The invention discloses a method for preparing a low-corrosive sulfur dissolving agent. The preparation process comprises the following steps: under normal temperature and pressure conditions, mixing metal alkoxide, benzene compound, alkaline triazine desulfurizer, surfactant, corrosion inhibitor and auxiliary agent, and stirring for 8 to 10 minutes to obtain the sulfur dissolving agent.

[0030] The present invention will be further described below in conjunction with specific embodiments.

[0031] Example 1

[0032] 1. The ratio of low-corrosive sulfur dissolving agent is: 55% sodium tert-butylate, 6% o-xylene, 10% alkaline triazine desulfurizer, 5% sodium polystyrene sulfonate, 14% bisimidazoline quaternary ammonium salt, 10% mixture of fatty alcohol polyoxyethylene ether and alkylphenol polyoxyethylene ether, and auxiliary agent composed of hydroxycarboxylic acid, high-temperature penetrant JFC-M and ethylene glycol, and the test temperature is 50°C. The amount of fatty alcohol polyoxyethylene ether and alkylphenol polyoxyethylene ether and the sum of sodium polystyrene sulfonate shall not exceed 10%.

[0033] 2. Preparation of low-corrosive sulfur dissolving agent:

[0034] 1) Synthesis of metal alkoxides: Slowly add a metal source (metal element or dry metal hydride or carbonate and other compounds) to a reactor filled with an alcohol solvent. The feeding rate should be well controlled to avoid excessive reaction. For example, when preparing sodium ethoxide, slowly add small pieces of sodium metal to ethanol. The reaction is carried out under certain temperature and stirring conditions. The reaction temperature and time depend on different metal alkoxides and reaction systems. Generally speaking, the temperature is between 50°C and 150°C, and the reaction time ranges from several hours to tens of hours. During the reaction, pay close attention to the progress of the reaction, such as the color change of the solution, the presence or absence of gas generation, etc. After the reaction is completed, filter the reaction solution to remove unreacted metal impurities and other insoluble substances. Then, distill or vacuum distill the filtrate to remove excess alcohol solvents and possible by-products to obtain a pure metal alkoxide sulfur dissolving agent.

[0035] 2) Mixing: Under normal temperature and pressure conditions, the main agent, auxiliary agent, and auxiliaries synthesized in advance are mixed in a certain proportion according to the needs of the elemental sulfur deposition degree and corrosion degree, and stirred for 8 to 10 minutes. The whole process is simple and convenient, so that mixing and preparation can be carried out on site according to needs.

[0036] 3. Sulfur dissolution effect test

[0037] A certain amount of sulfur powder (block) used in the experiment is placed in a stoppered colorimetric tube, and 100 ml of the sulfur dissolving agent prepared by the present invention is added thereto, and after slight stirring, it is placed in a constant temperature water bath. After dissolving for the same time, the obtained reaction solution is filtered with filter paper, and the remaining sulfur powder is rinsed, dried and weighed, and the sulfur dissolving amount of the sulfur dissolving agent is calculated using the following difference method.

[0038] S = (W0-W1); where: S-dissolved sulfur content, g / 100ml; W0-initial mass of sulfur powder (lump), g; W1-mass of sulfur powder (lump) after reaction, g; V-volume of sulfur dissolving agent, ml.

[0039] Under the experimental condition of 2h sulfur dissolution time, the results are as follows: the sulfur dissolution amount of elemental sulfur powder is 102.7g / 100mL, the sulfur dissolution amount of on-site sulfur block is 62.1g / 100mL, and the sulfur dissolution amount of on-site sulfur powder is 87.5g / 100mL. It can be seen that the sulfur dissolution effect of the sulfur dissolving agent prepared by the present invention on different sulfur forms is: elemental sulfur powder> on-site sulfur powder> sulfur block, but all can be dissolved in the end.

[0040] The variation curve of the amount of sulfur dissolved in the sulfur dissolving agent prepared by the present invention with temperature is as follows: Figure 1 As shown, it can be seen that the sulfur dissolution rate increases with the increase of temperature.

[0041] 4. Desulfurization effect

[0042] according to Figure 2 As shown in the process, connect the equipment, check the air tightness, take 5ml zinc acetate and add it to the No. 8 conical flask, dilute to 50mL. Then use a pipette to take 75mL of sodium hydroxide solution to the No. 13 150mL conical flask for tail gas absorption. Add 200mL of distilled water to the No. 5, 6, and 7 test tubes respectively, take 1mL of sulfur dissolving agent and add it to No. 5 and 6 respectively, and take 2mL of sulfur dissolving agent and add it to No. 7. Then add 400mL of deionized water to the No. 3 500mL round-bottom beaker, and then add 6mL of sodium sulfide solution. After plugging the bottle stopper, keep all water stoppers closed, inject 4mL of hydrochloric acid into the No. 2 separatory funnel and stir with a magnetic stirrer for 5min. Next, open the No. 9 water stop clamp, and keep the flow rate of 50mL / min, 100mL / min, and 350mL / min for 10min, 10min, and 40min, respectively, and then turn off the gas source. Finally, 15 mL of 0.1 mol / L iodine standard solution and 5 mL of hydrochloric acid were respectively injected into a No. 8 conical flask, mixed thoroughly, and placed in a dark place for 10 minutes before measuring the sulfide content by titration. A 0.01 mol / L sodium thiosulfate solution was added until it turned light yellow, and then a starch indicator was added and titrated until the blue color just disappeared. The final desulfurization rate reached 84.3%.

[0043] The desulfurization rate is calculated according to the following formula: η = (100-(C I2 ×V I2 -C1×V1) / (C I2 ×V I2 -C1×V0))×100%;

[0044] Where: η-sulfur removal rate, %; C I2 -iodine solution concentration, mol / L; V I2 - Volume of iodine solution used, mL

[0045] C1-sodium thiosulfate solution, mol / L; V0-volume of sodium thiosulfate consumed, ml; V1-volume of sodium thiosulfate consumed by the sample, ml.

[0046] 5. Corrosion inhibition behavior

[0047] The 40mm×10mm×3mm metal test piece was polished to 1000# with water-abrasive sandpaper in turn, then degreased with ethanol, and air-dried. After 24 hours, it was weighed on a balance (recorded as W0). According to the standard NACE SP 0775-2023 "Standard Operating Procedure for Preparation, Installation, Analysis and Interpretation of Corrosion Samples in Oilfield Operations", after the solution temperature rises to the target temperature, the metal test piece is hung in the solution, reacts for a period of time and then taken out (the reaction time is recorded as t), and then the surface corrosion deposits are removed with a standard film removal solution, degreased and dehydrated with ethanol again, and air-dried, and placed in a dryer for 24 hours and weighed again (recorded as W1), and the corrosion rate is calculated using the following weight loss method, and compared with the corrosion rate specified in the standard SY / T 5329-2022 "Technical Requirements and Analysis Methods for Water Quality Indicators of Clastic Reservoirs".

[0048] C = (W0-W1) / (ρ·s·t), where: C is the corrosion rate of the specimen, mm / a; W0 is the initial weight of the metal specimen before corrosion, g; W1 is the weight of the metal specimen after removing the corrosion deposits, g; ρ is the density of the specimen, g / mm 3 ; s is the surface area of ​​the test piece, mm 2 ; t is the reaction time, d.

[0049] The results showed that after immersion for 5 days, the corrosion rates of API N80S and TP110S sulfur-resistant steels were 0.061mm / a and 0.059mm / a, respectively, which were far less than the corrosion control requirement of 0.076mm / a specified in the standard; there were no obvious signs of corrosion and no obvious pitting morphology on the surface.

[0050] 6. Rubber damage

[0051] Due to the surface area, the damage to the mass and volume of the fluororubber was relatively serious at the beginning, but the overall damage was small. The results are shown in Table 1 below.

[0052] Table 1 Fluororubber damage

[0053] Soaking time (h) Appearance Weight change rate (%) Volume change rate (%) 5 No change 0.22 0.84 10 No change 1.05 1.36 15 No change 1.32 1.53 20 No change 1.51 1.60

[0054] In addition, after immersion for 20 hours, the maximum load of fluororubber decreased from 241.66N in the original state to 233.51N, the tensile strength decreased from 13.58MPa to 13.32MPa, and the elongation at break decreased from 202.48% to 181.64%.

[0055] The final results show that the sulfur dissolving agent prepared by the present invention has low corrosiveness to the pipe and the packer rubber sleeve.

[0056] The embodiments described above are only descriptions of the preferred modes of the present invention, and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should all fall within the protection scope determined by the claims of the present invention.

Claims

1. A low-corrosive sulfur dissolving agent, characterized in that: The invention comprises the following components: 50-70 wt% of metal alkoxide, 5-15 wt% of benzene compound, 10-20 wt% of alkaline triazine desulfurizer, 3-10 wt% of surfactant, 5-15 wt% of corrosion inhibitor and 3-10 wt% of auxiliary agent.

2. The low-corrosive sulfur dissolving agent according to claim 1, characterized in that: The auxiliary agents include chelating agents, penetrants and antifreeze agents.

3. The low-corrosive sulfur dissolving agent according to claim 2, characterized in that: Calculated by mass percentage, the chelating agent is 20-40%, the penetrant is 30-50%, and the antifreeze agent is 15-35%.

4. The low-corrosive sulfur dissolving agent according to claim 2 or 3, characterized in that: The chelating agent includes a phosphate chelating agent or an organic polyphosphate chelating agent; the penetrant includes a high-temperature penetrant JFC-M and / or acetone; and the antifreeze agent includes ethylene glycol and / or ethanol.

5. The low-corrosive sulfur dissolving agent according to claim 1, characterized in that: The metal alkoxide includes at least one of sodium tert-butoxide, potassium ethoxide, and potassium tert-butoxide; the benzene compound includes at least one of o-xylene and chlorobenzene; the surfactant includes at least one of sodium polystyrene sulfonate and alkylphenol polyoxyethylene ether; and the corrosion inhibitor includes at least one of azole corrosion inhibitor and amino acid corrosion inhibitor.

6. A method for preparing the low-corrosive sulfur dissolving agent according to any one of claims 1 to 5, characterized in that: The preparation process of the low-corrosive sulfur dissolving agent is as follows: under normal temperature and pressure conditions, metal alkoxide, benzene compound, alkaline triazine desulfurizer, surfactant, corrosion inhibitor and additive are mixed and stirred for 8 to 10 minutes to obtain the low-corrosive sulfur dissolving agent.

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