By mid-2000, the H2S content in gas from the Chihuido Lomitas field separator started to increase significantly up to an average of 2,000 ppm. A multidisciplinary team was formed to address the problem, which was deemed to be very likely due to bacterial activity in the reservoir. Therefore, the group focused on the issue of concern, which is generally known as reservoir souring. It was concluded that using sulphur isotope measurement techniques was one of the few tools available to effectively determine the cause of the souring. A group of specialists in isotope assessments from a local Research Institute was called in to join the team. Based on the team's findings, supported by a geochemical model, it was shown that H2S generation in the Troncoso and Avile formations was due to the activity of sulphate reducing bacteria living in the reservoir. The model developed relates increasing bleeding water injection to the phenomenon studied. A thermo-chemical reduction was proposed to explain the H2S content in El Filon Reservoir. Innovative H2S removal techniques are currently being applied.