The following calculator can be used to determine how much H2S is dissolved in each phase when the gas H2S concentration (ppmv) is known. The calculation uses the principles of Henry’s law in combination with solubility and partitioning data for H2S. Skip directly to Calculator.
It is very common (and convenient) for producers to measure the H2S concentration in produced gas and relate that to the concentration in the liquid phase. For liquid scavenger suppliers it is of utmost importance to understand how much H2S, in total, is in the system. This data is used to determine how much scavenger needs to be injected to remove the H2S from the system. This is only applicable when treating multiphase systems via direct injection.
Some chemical suppliers make the mistake to base the treatment rate on the gas H2S concentration only. This would result in undertreating. The correct way is to determine the total amount of H2S in the system, thus you have to consider the gas, water and oil. The H2S will migrate between the phases based on the operating pressure and temperate. Liquid properties like salinity and viscosity also affects the partitioning.
The calculator below can be used to get a rough estimate of how much H2S is partitioned between the phases. For example, the H2S concentration of gas in a pipeline is measured to be 1000 ppm(v). The system operates at 10 bar (~ 1000 kPa) and 35C. How much H2S is expected to be in the liquids. Let’s assume a light oil with API gravity of 35 and produced water with a salinity of 60g/l. The data is entered in the calculator below. The results indicate 22.25 mg/l in the water phase and 18.10 mg/l in the oil. The data can now easily be used to determine how much H2S (in mass) is in the system (by using production volumes, thus mg/l H2S multiplied by the production volumes in l/day will yield the mass of H2S in mg/day, simply convert to whatever units required). Feel free to use the H2S mass in Gas calculator here.