Alex,
Here are some thoughts on LDHI; Others may contribute more:
1. LDHI generally do not usually pose integrity (carbon steel corrosion or seal degradation) concerns with production equipment when mixed with production fluids. However, stainless steel tubing may see pitting corrosion on exposure to chlorides which may be present in some pure LDHI, depending on vendor formulation, so extensive material compatibility tests should be done with the proposed chemical.
Also the topsides process efficiency may be affected by presence of some of the AA type LDHIs causing formation of unresolved emulsion layer. Separation efficiency should be verified in presence of proposed LDHI as part of the qualification.
2. Normal production equipment may be used. In one N.Sea example, switching from glycol to LDHI saved the need for glycol regeneration facility. Existing facility conversion from thermodynamic inhibitor to LDHI should focus more on LDHI retaining its effectiveness in presence of all other chemicals injected in the produced fluid stream. For example, corrosion inhibitors usually reduce the efficiency of LHDIs requiring higher LDHI dosage to compensate for that and affecting LDHI expense. Similar to material compatibility, extensive chemical compatibility and thermal stability tests should be done during qualification. I would recommend contacting Dr. Aftab Khokhar who studied at NTNU in Trondheim and has experience in this.
3. Sales agreement may depend on certain compound concentration limits. LDHI may be formulated in various solvents different from the restricted compounds. If produced fluids from several facilities are mixed in a gathering pipeline then components may get diluted. If LDHI is used periodically, then dilution and scheduling of injection should be coordinated with the pipeline operator and with other producing facilities to ensure threshold concentration is not exceeded.
If LDHI is formulated with methanol which can partition into the gas phase, that should be accounted for with thermodynamic simulation to evaluate methanol content in gas at different LDHI injection rates.
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Taras Makogon
HoustonTX
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