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    Triazine-Based H2S Scavengers' Mechanisms

    News

    Triazine-Based H2S Scavengers' Mechanisms

    2025-02-25

    Mechanisms, Physicochemical Properties, and Compatibility

    The reaction between triazine-based desulfurizers and hydrogen sulfide produces thiotriazine compounds with excellent aqueous solubility, stability, high reactivity, and easy separation‌. Oil-soluble scavengers (such as triazine and aldehyde compounds) dissolve in the oil phase, while most triazine desulfurizers are water-soluble (e.g., triethanolamine triazine derivatives)‌. Some modified triazines (like long-chain alkyl-substituted triazines) exhibit oil solubility‌

    1. Mechanism of H2S Removal by Triazine-Based Scavengers

    Triazine compounds (such as 1,3,5-triazine derivatives) remove H₂S by undergoing nucleophilic addition and condensation reactions, converting H₂S into stable thiotriazine compounds. The specific process is as follows:

    ▲▲ Nucleophilic Addition: The sulfur atom of H₂S acts as a nucleophile attacking the electron-deficient carbon atom in the triazine ring, forming an intermediate.

    ▲▲ Ring-Opening Condensation: The triazine ring further reacts with H₂S to produce stable products like thiotriazines or triazine polysulfides, which exist either in solid or dissolved form, preventing H₂S release.

    Characteristics:

    ▶▶The reaction is highly efficient, especially under alkaline conditions.

    ▶▶The products have good water solubility, making it easy to separate them from downhole fluids.

      H2S scavenger Triazine-Based

      2. Physicochemical Properties and Compatibility Requirements 

      a.  Acidity/Alkalinity

      ▶▶ Optimal pH range: Slightly alkaline (pH 8-10)

      ▶▶ Alkaline environments promote the ionization of H₂S into HS⁻/S²⁻, enhancing nucleophilic reaction activity.
      ▶▶ Acidic conditions (pH < 7) inhibit the reaction and allow H₂S to escape as a gas, increasing corrosion risks

          Compatibility Requirements:
      ▶▶ Must match the pH of drilling/completion fluids; alkaline agents (like NaOH or carbonates) may need to be added.
      ▶▶ Avoid direct mixing with acidic additives (like HCl corrosion inhibitors) to prevent deactivation
      Must match the pH of drilling/completion fluids; alkaline agents (like NaOH or carbonates) may need to be added.

      b.  Water Solubility and Oil Solubility

      Water Solubility: 
      Most triazine-based scavengers are water-soluble (e.g., triethanolamine triazine derivatives), suitable for water-based drilling fluid systems.
      ▶ Advantages: Quick dispersion, high reaction efficiency.
      ▶ Disadvantages: Might precipitate in the oil phase due to low solubility.
      Oil Solubility: Some modified triazines (like long-chain alkyl-substituted triazines) are oil-soluble, suitable for oil-based drilling fluids or high oil content downhole environments.
      ▶ Advantages: Compatible with oil phase, reduces emulsification risk.
      ▶ Disadvantages: May require surfactants to enhance contact with H₂S.
          Compatibility Requirements:
      Choose water-soluble or oil-soluble products based on downhole fluid type:
      ▶ Water-based systems: Prefer water-soluble.
      ▶ Oil-based systems: Use oil-soluble or add emulsifiers for solubility.
      Avoid incompatibility leading to agent precipitation or emulsion instability.
      C. Influence of Temperature and Salinity
      ▶  High Temperature: High temperatures might accelerate triazine decomposition; choose heat-resistant modified products (like cyclic triazine polymers).
      ▶  High Salinity: High salt concentrations might reduce triazine solubility; adjust the formulation or increase dosage

      Sulfide scavenger

      3. Comprehensive Compatibility Requirements for Downhole Fluids

      a. Compatibility with Other Chemicals

      ▶ Avoid coexistence with oxidative biocides (like persulfates) to prevent side reactions.

      ▶ Test synergy with corrosion inhibitors (like imidazolines) to prevent competitive adsorption failures.

      ▶▶Ring-Opening Condensation: The triazine ring further reacts with H₂S to produce stable products like thiotriazines or triazine polysulfides, which exist either in solid or dissolved form, preventing H₂S release.

      b. Product Stability:

      ▶ Ensure that the thiotriazine reaction products do not precipitate or clog formation pores.

      ▶ In environments with high calcium/magnesium ions, add chelating agents (like EDTA) to prevent scale formation.

      c. Environmental and Safety Considerations

      ▶ Select low-toxicity, easily biodegradable triazine derivatives (like hydroxyethyl triazine).

      ▶ Control dosage to avoid accumulation of by-products (like formaldehyde release).

        sulfur dispersing agents

        4. Optimization Suggestions for Application Scenarios

        ▶ Gas wells/sulfur-containing oil wells: Prioritize high water-soluble triazines with pH adjustment.

        ▶ High-temperature deep wells: Use heat-resistant triazine polymers.
        ▶ Oil-based systems: Choose oil-soluble triazines or add non-ionic surfactants.
        Youzhu Chem(www.youzhuchem.com) provides both oil soluble and water soluble H2S Scavenger, tell us the specific application, your expected H2S levels, temperature, and pressure conditions, YouzhuCHEM will share you the right Sulphur removal agent.

        Youzhu Chem(www.youzhuchem.com) supply oilfield chemicals to those companies, who are dedicated to offer full spectrum oilfield production chemicals and services to the entire life-cycle of producing oil well system.

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