Investigation on Origins of Hydrogen Sulfide Production in Sweet Gas Fields

Hydrogen sulfide is a common unwanted material in gas reservoirs which should be removed in the process of refining. Although a large number of gas reservoirs in the world are sour, but sweet gas reservoirs can be found in some areas of the world, for example in south of Iran. Occurrence of hydrogen sulfide (H2S) in a sweet gas field was a major origin for site investigation. The situation became even worse after acidizing. The main cause of H2S forming was guessed to be formation rock types which were mainly composed of anhydrite. In order to make a better view of the work, chemical samples were taken from the well at different production rates and condition of hydrogen sulfide precipitation was simulated using software. The same situation existed for CO2 and design of the investigations started to remove these toxic gases. Further simulations proved that a modified acid mixture, in future acidizing operations, can reduce the amount of these gases significantly and environmental issues would be concerned seriously in such cases.